SPLIT SPOON PENETRATION TESTING IN GRAVELS …

SPLIT SPOON PENETRATION TESTING IN G R A V E L S

by

CHRISTOPHER R Y A N DANIEL

B .A .Sc , The University of British Columbia, 1997

A THESIS SUBMITTED PW PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF

M A S T E R OF APPLIED SCIENCE

in

THE F A C U L T Y OF G R A D U A T E STUDIES

(Department of Civil Engineering; Geotechnical Engineering)

We accept this thesis as conforming to the required standard

THE UNIVERSITY OF BRITISH C O L U M B I A

October 2000

© Christopher Ryan Daniel, 2000

In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e head o f my department o r by h i s o r h e r r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n ot be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .

Department o f C / 'u i ' -^ Ei/itîiAeeW</>g^

The U n i v e r s i t y o f B r i t i s h Columbia Vancouver, Canada

Date ^ c / o ^ e r /3 , 3 o & o

A B S T R A C T

The widely used "Standard Penetration Test" (SPT) is considered unreliable for gravel deposits because gravel particles can be larger than the opening of the SPT split-spoon sampler and because drilling methods normally employed for SPT in sands are often impractical in gravels. The "Large Penetration Test" (LPT) potentially reduces the effect of the former through the use of oversized split-spoon samplers. This thesis presents a method of predicting SPT from LPT blow counts so that currently available empirical design methods based on the SPT may be used in gravel deposits. The proposed method considers input energy and sampler dimensions and can be used with any LPT system (i.e. any combination of hammer and split-spoon). The results of the proposed method are compared to those of an existing correlation method and to empirical SPT-LPT correlation factors from the literature, including correlations for the "Japanese LPT" (JLPT) and "Italian LPT" (ILPT). In addition, three field research programs were conducted to develop an empirical correlation factor between the SPT and the "North American LPT" (NALPT). Field tests revealed that the proposed correlation method requires an empirical correction factor of 0.82. Review of the JLPT data set revealed that the SPT-JLPT correlation factor might be unreliable. If the JLPT data is excluded and if the empirical correction factor is applied, it is found that the correlation factors predicted using the proposed method range from 83% to 96% of those observed in sands. The equivalent range for the existing correlation method was 39% to 73%. The author attempted to obtain preliminary insight into the problem of grain size effects using the available test data. The observed SPT-NALPT and SPT-ILPT correlation factors appear to decrease with increasing grain size. Data illustrating a fair relationship between the observed correlation factor and the portion of the soil that is too coarse to enter the SPT split-spoon is presented.

T A B L E O F C O N T E N T S

A b s t r a c t i i

L i s t o f T a b l e s vii

L i s t o f F i g u r e s viii

L i s t o f S y m b o l s a n d A b b r e v i a t i o n s xiii

A c k n o w l e d g e m e n t s xv

1. I N T R O D U C T I O N 1

2 . S P T A N D L P T D E T A I L S A N D C O R R E L A T I O N S 3

2.1 S t a n d a r d P e n e t r a t i o n Tes t ( S P T ) 3

2.2 N o r t h A m e r i c a n L P T ( N A L P T ) 5

2.3 J a p a n e s e L P T ( J L P T ) 12

2.4 I t a l i a n L P T ( I L P T ) 15

3. D Y N A M I C P E N E T R A T I O N T E S T I N G E N E R G Y T H E O R Y 20

3.1 K i n e t i c E n e r g y o f D r i v i n g Sys tems 21

3.2 St ress W a v e T h e o r y 22

3.2.1 Characteristics of Stress Waves 22

3.2.2 Application to SPT and LPT Energy Measurement 24

3.2.2.1 Force Squared (FF) Method 25

3.2.2.2 Force Velocity (FV) Method 27

3.2.3 Stress Wave Modelling 28

4. P R O P O S E D S P T - L P T C O R R E L A T I O N M E T H O D 33

4.1 S o i l Res i s t ance C o n s i d e r a t i o n s 33

iii

4.2 Energy Input Considerations 36

4.3 Synthesis of Proposed Method 46

4.4 Application of Proposed Method 50

5. KIDD2 N A L P T F I E L D P R O G R A M 53

5.1 Drilling Method 57

5.2 Quasi-Static Penetration Tests 57

5.2.1 Description of Test Method 57

5.2.2 Test Results 58

5.2.3 Discussion 58

5.3 Dynamic Penetration Tests 63


5.3.2 Energy Measurement 64


5.4 Discussion of Energy Data 69

5.4.1 Data Repeatability 69

5.4.2 Calibration Factors 76

5.4.3 Quality Control Using Upper Bounds 80

5.4.4 Quality Control Using Force-Velocity Proportionality 82

5.5 Calibration of Proposed Method 87

6. S E W A R D , A L A S K A N A L P T F I E L D P R O G R A M 90


iv



6.2.2 Energy Measurement 93


6.3 Discussion 95

6.3.1 Grain Size Analysis Results 95

6.3.2 Blow Count Repeatability 98

6.3.3 Energy Data Quality 100

6.4 Correlation Factor 106

7. K E E N L E Y S I D E D A M N A L P T F I E L D P R O G R A M 110





7.3 Discussion of Energy Data 115

7.4 Correlation Factor 119

8. DISCUSSION 126

8.1 Standardization of N A L P T Results 126

8.2 Performance of Proposed Correlation Method 127

8.3 Grain Size Effects 129

8.4 Use of SPT-LPT Correlations 136

v

9. C O N C L U S I O N AND R E C O M M E N D A T I O N S F O R F U T U R E 141

R E S E A R C H

Bibliography 144

APPENDIX A - STRESS W A V E F O R M U L A E 148

APPENDIX B - KIDD2 F I E L D P R O G R A M T E S T R E S U L T S 157

APPENDIX C - S E W A R D , A L A S K A F I E L D P R O G R A M T E S T 163 R E S U L T S APPENDIX D - K E E N L E Y S I D E D A M F I E L D P R O G R A M T E S T 168 R E S U L T S

vi

LIST OF T A B L E S

2.1 Results of SPT-ILPT Comparison (Crova et al., 1993). 17

2.2 Summary of SPT and LPT Details. 18

3.1 Soil Parameters Recommended for use with G R L W E A P 32 (GRLWEAP, 1997).

4.1 Hammer, Rod and Sampler Details Used for G R L W E A P Analyses. 41

4.2 Soil Parameters Used for G R L W E A P Parametric Study. 42

4.3 (N / Ru) Values Calculated Using G R L W E A P Parametric Study 43 Results.

4.4 Summary of Proposed Correlation Method Input Data and Results. 50

4.5 Summary of Observed and Predicted Correlation Factors. 50

6.1 Comparison of Uncorrected N A L P T Blow Counts. 98

6.2 Comparison of N A L P T Velocity and Rod Energy Ratios. 103

8.1 Summary of Observed and Standardized SPT-NALPT Correlation 127 Factors.

8.2 Revised Summary of Observed and Predicted Correlation Factors. 128

8.3 Summary of Available Grain Size Information. 131

v i i

LIST O F FIGURES

Figure .No. ^ êe

2.1 Range of Acceptable Dimensions for SPT Split-Spoon Sampler 4 (ASTM 1991a).

2.2 Donut Hammer Lifted Using Rope and Cathead Method (Robertson 6 etal., 1992).

2.3 Typical Longitudinal Section of a Safety Hammer. 7

2.4 Typical Details of a Trip Release Hammer (Clayton, 1990). 8

2.5 N A L P T Split-Spoon Sampler used by USACE. 9

2.6 Cohesionless Sand and Silt SPT-LPT Correlation Graph (Winterkorn 11 and Fang, 1975).

2.7 JLPT Split-Spoon Sampler {after: Kaito et al., 1971). 13

2.8 SPT-JLPT Correlation Data (Yoshida etal., 1988). 14

2.9 ILPT Split-Spoon Sampler and Hammer (Crova et al., 1993). 16

2.10 Comparison of SPT and LPT Test Details. 19

3.1 G R L W E A P Pile or Rod String Model (after: G R L W E A P , 1997). 29

3.2 Idealized Soil Response to Static and Dynamic Loading. 31

4.1 Forces Acting on (a) SPT Split-Spoon and (b) Piezocone During 34 Quasi-Static Penetration (Schmertmann, 1979).

4.2 Energy Expended During Displacement of (a) Ideal Plastic Soil and 37 (b) Ideal Elastic-Plastic Soil.

4.3 Comparison of SPT Blow Counts Predicted Using Ideal Plastic and 39 Ideal Elastic-Plastic Soil Models to G R L W E A P Analysis Results.

viii

I T _ ^ ^

4.4 G R L W E A P Analysis Results for SPT, NALPT, JLPT and ILPT. 40

4.5 Sensitivity of Predicted (N / R u ) Values to Soil Parameter Variations. 44

4.6 Inverse Proportionality Relationship Between (N / R u ) and ENTHRU. 45

4.7 Effect of Rod Cross-Sectional Area on Predicted (N / R u ) Values. 47

4.8 Idealized Effect of Rod Cross-Sectional Area on Axial Force Data. 48

5.1 Kidd2 Piezocone Penetration Test Data. 54

5.2 Distribution of SPT, N A L P T and CPTU Test Holes at Kidd2. 55

5.3 Kidd2 Grain Size Distribution Data. 56

5.4 Sample SPT Quasi-Static Penetration Test Strip Chart Output. 59

5.5 Summary of SPT and N A L P T Quasi-Static Resistance Versus 60 Penetration.

5.6 Measured and Predicted Quasi-Static Penetration Resistance Force 61 Versus Depth.

5.7 Comparison of Measured and Predicted Quasi-Static Penetration 62 Resistance Force.

5.8 Sample and Idealized HPA Strip Chart Output. 65

5.9 Sample D E M Software Operating Screen. 67

5.10a Raw and Energy Corrected SPT Blow Counts Versus Depth. 70

5.1 Ob Raw and Energy Corrected N A L P T Blow Counts Versus Depth. 71

5.11 D E M Output Recorded During Hammer Blows Within the 152 mm 73 to 457 mm (6" to 18") Sampler Penetration Range at 9.5 m (31') Depth in SPT9904.

ix

Figure No. Title Page

5.12 D E M Output Recorded During Hammer Blows Within the 152 mm 74 to 457 mm (6" to 18") Sampler Penetration Range at 18.6 m (61') Depth in SPT9901.

5.13 Comparison of Average Force and Velocity Data Recorded in Two 75 SPT Test Holes at Differing Depths.

5.14 D E M Output Recorded During Hammer Blows Within the 152 mm 77 to 457 mm (6" to 18") Sampler Penetration Range at 9.5 m (31') Depth in LPT9903.

5.15 D E M Output Recorded During Hammer Blows Within the 152 mm 78 to 457 mm (6" to 18") Sampler Penetration Range at 17.1 m (56') Depth in LPT9902.

5.16 Comparison of Average Force and Velocity Data Recorded in Two 79 N A L P T Test Holes at Differing Depths.

5.17 Relationship Between Additional Potential Energy Due to Sampler 81 Set and Blow Count.

5.18 Comparison of D E M and "Corrected" H P A Energy Data. 83

5.19 Average SPT Force and Velocity Data Recorded at 18.6 m (61') in 84 SPT9904.

5.20 Average N A L P T Force and Velocity Data Recorded at 17.1 m (56') 86 in LPT9902.

5.21 Comparison of FV Energy Corrected SPT and N A L P T Blow Counts 89 Recorded at Kidd2.

6.1 Distribution of SPT, N A L P T and DCPT Test Holes at Seward, 91 Alaska Main Test Site.

6.2 Comparison of Percent Gravel in SPT and N A L P T Samples. 96

6.3 Comparison of Mean Grain Size (D 5 0) of SPT and N A L P T Samples. 97


6.4 Comparison of Uncorrected N A L P T Blow Counts from SEWA9803 99 and SEWA9806.

6.5 D E M Force and Velocity Data Collected During SPT at 18.1 m 101 (59.3') in SEWA9802.

6.6 D E M Force and Velocity Data Collected During N A L P T at 19.6 m 102 (64.3')inSEWA9803.

6.7 Average SPT Force and Velocity Data Recorded at 18.1 m (59.3') in 104 SEWA9802.

6.8 Average N A L P T Force and Velocity Data Recorded at 19.6 m 105 (64.3') in SEWA9803.

6.9 Comparison of FF Energy Corrected SPT and N A L P T Blow Counts 108 Recorded at Seward, Alaska Main Test Site.

6.10 Comparison of FV Energy Corrected SPT and N A L P T Blow Counts 109 Recorded at Seward, Alaska Main Test Site.

7.1 Plan View of Keenleyside Dam (Lum and Yan, 1994). 111

7.2 Grain Size Envelope for Keenleyside Dam Sand and Gravel Fill 112 Material (Lum and Yan, 1994).

7.3 D E M Force and Velocity Data Collected During N A L P T at 18.3 m 116 (60') in DH99-20.

7.4 Average N A L P T Force and Velocity Data Recorded at 18.3 m (60') 117 in DH99-20.

7.5 Comparison of D E M and "Corrected" HPA Energy Data. 120

7.6 Comparison of FV Energy Corrected SPT and FF (AW) Energy 121 Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

7.7 Comparison of FV Energy Corrected SPT and FF (NW) Energy 122 Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

xi


7.8 Comparison of Equivalent SPT Blow Counts from BPT Data and FF 124 (AW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

7.9 Comparison of Equivalent SPT Blow Counts from BPT Data and FF 125 (NW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

8.1 Comparison of SPT-ILPT Correlation Factors and Mean Grain Size 133 Data from Messina, Italy (Crova et al., 1993).

8.2 Comparison of SPT-NALPT Correlation Factors and Mean Grain 134 Size Data from Seward, Alaska Research Program.

8.3 Comparison of SPT-NALPT Correlation Factors to "Oversized" 135 Portion of N A L P T Samples from Seward, Alaska Research Program.

8.4 Keenleyside Dam SPT-NALPT Correlation Data (FV Energy 137 Corrected), Sand Versus Gravel Data.

8.5 Dynamic SPT Blows versus Penetration Data from Kidd2 and 138 Seward, Alaska Sites.

8.6 Dynamic N A L P T Blows versus Penetration Data from Kidd2 and 139 Keenleyside Dam Sites.

x i i

LIST O F S Y M B O L S AND ABBREVIATIONS

A area A S T M American Society for Testing and Materials A E split-spoon sampler end bearing area A F split-spoon frictional area at 12" penetration A T E equivalent tip bearing area BC Hydro British Columbia Hydro and Power Authority bpf blows per foot BPT Becker Penetration Test BSC British Soil Classification system c stress wave propagation velocity CPT Cone Penetration Test CPTU Piezocone Penetration Test Cdp pile damping value c , SPT-CPT end bearing correlation factor c 2 SPT-CPT friction correlation factor d split-spoon sampler displacement D dynamic component of total soil resistance DCPT Dynamic Cone Penetration Test D E M Dynamic Energy Monitoring system D 5 0 mean grain size E Young's modulus ENTHRU energy transmitted through drill rods ER energy ratio E R A energy ratio used for G R L W E A P or equivalent analysis ER r energy ratio calculated from the stress wave energy ER V energy ratio calculated from the hammer kinetic energy F force F(t) force which varies with time FF Force Squared stress wave energy measurement method FV Force Velocity stress wave.energy measurement method fs measured CPTU friction sleeve stress g gravitational acceleration G R L W E A P Goble, Rausche and Likins Wave Equation Analysis Pro H height HPA Hammer Performance Analyzer ID inner diameter ILPT Italian Large Penetration Test j Smith damping factor JLPT Japanese Large Penetration Test jsi Smith damping factor at segment (i) K c velocity correction factor

xiii

ksi soil stiffness at segment (i) K , load cell position correction factor K 2 rod length correction factor L length of drill rod between stress wave measurement point and soil-

sampler interface LPT Large Penetration Test L H hammer length N uncorrected blow count N A L P T North American Large Penetration Test N 6 0 blow count corrected to 60% standard energy (Nl)60 blow count corrected to 60% standard energy and 100 kPa overburden

pressure OD outer diameter PE maximum potential energy of SPT or LPT hammer PDI Pile Dynamics Incorporated q soil quake q c measured CPTUtip stress qt CPTU tip stress corrected for pore pressure effects q-s quasi-static R total (static + dynamic) soil resistance Rf CPT friction ratio R s Sampler-Hammer Ratio R u ultimate static resistance Rui ultimate static resistance at segment (i) S static component of total soil resitance SPT Standard Penetration Test t time T time required for a stress wave to pass a point on a drill rod U S A C E United States Army Corp of Engineers u s e Unified Soil Classification system u 2 CPTU pore pressure measurement directly behind the cone tip V velocity V(t) velocity which varies with time w weight w buoyant weight X position along a bar or drill rod Z rod impedance At incremental time step Ad change in split-spoon sampler displacement ild hammer dynamic efficiency P mass density

xiv

A C K N O W L E D G E M E N T S

The author gratefully acknowledges the financial support of the Natural Science and Engineering Research Council (NSERC) of Canada, which was provided as a Post-Graduate Schedule A Scholarship. In addition, the research could not have been completed without the generous support of the following organizations:

• Foundex Explorations Ltd. of Surrey, B.C. donated drilling services and expertise during the Kidd2 investigation;

• The British Columbia Hydro and Power Authority (BC Hydro) donated drilling time and field support during the Keenleyside Dam investigation, provided a D E M system during the Seward and Keenleyside investigations and provided access to the Kidd2 site;

• The United States Army Corps of Engineers (USACE) organized and provided drilling services and field support during the Seward investigation;

• Klohn-Crippen Consultants Ltd. provided the HPA system used during the three field investigations; and,

• Conetec Investigations Ltd., provided funding towards my involvement in the Seward investigation.

In addition, I would like to thank my advisor, Dr. John Howie, for introducing me to the topic and for his guidance and financial support during the course of my research, my co-advisor Dr. R.G. Campanella, for introducing me to geotechnical research and for his financial support, Dr. Alex Sy (Klohn-Crippen) for his insights on gravel testing and dynamic energy theory, Dr. Liam Finn (UBC) for his financial support and guidance during the Seward investigation, Dr. Joe Koester (USACE) for his efforts during the Seward investigation and Ken Lum (BC Hydro) for arranging the Keenleyside work.

Scott Jackson and Harald Schremp provided first class technical support, as always. A l i Amini, Patrick Koerner, Kevin Payne, Rashmi Pishe and Brian Walker provided much needed assistance during the Kidd2 research program.

Thanks to Kim, who is consistently the better half and to parents Trevor and Judi. Thanks also to Jay, Tom, Sue, Andrea, Ruben and Brionie, who have been good friends throughout the process.

xv

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Split Spoon Penetration Testing in Gravels

1. INTRODUCTION

Section 1.0 Introduction

Split spoon samplers are robust geotechnical tools than can be used at relatively little

expense to characterize soil stratigraphy through direct sampling of the strata. The

samplers are generally driven into the soil at the base of a clean, supported borehole by

striking the top of the rods used to lower the sampler with specially designed hammers.

Counting the number of hammer blows required to insert the sampler is a natural

extension of the characterization process that can be useful when compared to similar

data from other sites. For this reason, engineers most commonly perform "Standard

Penetration Tests" (SPT) using a standard 5.08 cm (2") outer diameter split spoon and a

63.5 kg (140 lb) hammer with a drop height of 76 cm (30"). Through the use of

standardized equipment, the energy available for penetration of the sampler as well as the

surface area upon which soil resistance acts is kept constant between tests and variations

of the number of blows required for sampler insertion, the "blow count" (N), should be a

measure of soil resistance. Many empirical correlations between soil design parameters

and SPT blow counts have been published. In fact, data from tests that are generally

considered superior to the SPT are often correlated to SPT blow counts in order to utilize

these empirical correlations. Thus, it is often assumed that SPT blow counts can be

predicted from the results of other in-situ tests.

The SPT is considered unreliable for gravel deposits, primarily because gravel particles

can be larger than the opening of the SPT sampler (3.5 cm, 1.375") and secondarily

because the drilling methods normally employed for SPT in sands are often impractical in

gravels. Perhaps as a result, direct empirical correlations between gravel design

parameters and SPT blow counts are seldom encountered. Tools such as the dynamic

cone penetration test (DCPT), Becker Penetration Test (BPT), seismic methods and, the

topic of this thesis, the Large Penetration Test (LPT) have been used for characterization

of gravels because they avoid one or both of the above issues.


Section 1.0 Introduction

LPT is a generic term that has been used by several authors to describe combinations of

oversized split-spoon samplers and hammers for use in gravels. Unfortunately, the LPT

does not directly address the difficulties of drilling in gravels but the similarity of the

SPT and LPT suggests that nothing more than a scaling factor is required to correlate the

two types of blow counts, which is a major advantage over DCPT, BPT and seismic tests.

The purpose of this thesis is to present and discuss data collected with one LPT system

that is generally available in North America, though not commonly used. The data were

collected at both sand and gravel sites and SPT blow counts from adjacent boreholes are

presented in all cases. In the course of this research, the author developed a preliminary

method of predicting SPT blow counts from the blow counts obtained with any

combination of hammer and split spoon sampler. The method is presented and calibrated

using the few SPT-LPT correlations that have been published to date and the correlations

developed herein.

Several authors have developed empirical and semi-empirical correlations between the

output of a test suitable for gravel and SPT blow counts to allow indirect use of SPT

empirical design methods. Such indirect use of SPT empirical design methods requires

the additional assumption that design parameters predicted from "equivalent" SPT blow

counts will accurately reflect the performance of the gravel deposits. The research

undertaken for this thesis was not designed to investigate the validity of this assumption

but the author has attempted to glean some preliminary insight into related issues such as

"grain-size effects" and this is presented in the Discussion.


Section 2.0 SPT and LPT Details and Correlations

2. SPT AND LPT DETAILS AND CORRELATIONS

The following sections describe the SPT and three LPT systems with which the author

has experience or that have been described in technical journals. The three LPT systems

are identified by area of origin. Existing correlations between the LPT's described and

the SPT are presented where available.

2.1 Standard Penetration Test (SPT)

Split-spoon samplers are hollow cylinders that are split lengthwise to facilitate sample

logging and extraction. Figure 2.1 illustrates the range of acceptable split-spoon

dimensions for SPT. The field engineer notes the condition of the cutting shoe and

whether or not a sample barrel liner and sample catcher were included, as these details

may affect the penetration resistance.

The sampler is driven into the soil at the base of a clean, supported borehole by striking

an anvil attached to the top of the drill rods with a 63.5 kg (140 lb) hammer dropped 0.76

m (30") yielding a maximum possible energy of 473 J (350 ft-lb). The number of blows

required for each 152 mm (6") of penetration are recorded and the total blows over the

interval 152 to 457 mm (6 to 18") are summed to give the blow count (N) in blows per

foot (bpf). Key details of the SPT sampler and hammer are described in A S T M Standard

D1586-84 (ASTM 1991a).

The A S T M standard is much more specific about the required design of the split spoon

than the hammer, stating only that the hammer must have a mass of 63.5 kg (4.35 slug)

and must drop vertically 0.76 m (30") before striking the anvil. As a result, hammer

designs vary considerably. The four most commonly used types are donut, safety, trip

release and automatic hammers.



OPEN SHOE HEAD ROLLPIN

(2 at y8 in. diameter)

A - 1.0 to 2 0 in. (25 to 50 mm) B - 18.0 to 30.0 in. (0.457 to 0.762 m) C - 1.375 ± 0.005 in. (34.93 ±0.13 mm) D - 1.50 ± 0.05 - 0.00 in. (38.1 ± 1.3 - 0.0 mm) E - 0.10 ± 0.02 in. (2.54 ± 0.25 mm) F - 2.00 ± 0.05 - 0.00 in. (50.8 ± 1 . 3 - 0 . 0 mm) G - 16.0* to 23.0*

The 1 Vi in. (38 mm) inside diameter split barrel may be used with a 1 &-gage wall thickness split Bner. The penetrating end ol the drive shoe may be slightly rounded. Metal or plastic retainers may be used to retain soil samples.

Figure 2.1 Range of Acceptable Dimensions for SPT Split-Spoon Sampler (ASTM 1991a).



The donut hammer is perhaps the simplest SPT hammer, consisting of a simple

cylindrical 63.5 kg mass falling down a guide rod. The hammer mass is attached to a

rope which runs through a pulley situated above the hammer. The hammer can be lifted

by manually pulling on the free end of the rope or by wrapping the rope around a rotating

cathead and applying tension, as shown in Figure 2.2. In the latter case, the operator

drops the hammer after visually checking the drop height by releasing the tension on the

rope. It is also possible to use a winch with a clutch release to lift and release the

hammer.

The safety hammer was developed to protect rig operators from injury by internalizing the

point of impact between the falling mass and the anvil rod (Figure 2.3). The same lift and

release methods used for the donut hammer may also be used with the safety hammer.

Trip release hammers were developed to improve the repeatability of SPT hammer drops

by allowing the operator to mechanically set the drop height. The efficiency of the

hammer is also improved by eliminating the friction losses inherent in the rope and

cathead method. Details of a typical SPT trip release hammer are shown in Figure 2.4.

The drop weight of an automatic hammer is lifted by a chain drive mechanism that is

hydraulically powered by the rig itself. The primary advantages of automatic hammers

are the speed with which the tests can be completed and the minimal physical effort

required by the rig operator.

2.2 North American L P T (NALPT)

Split-spoon samplers with outer diameters increasing by increments of 12.7 mm (0.5")

above 50.8 mm (2") are widely available. These larger samplers are most commonly

used for environmental investigations to maximize sample volume. The sampler shown

in Figure 2.5 has been used by the United States Army Corps of Engineers (USACE) for



Figure 2.2 Donut Hammer Lifted Using Rope and Cathead Method (Robertson et al., 1992).



Hammer Cap Block and

Hammer Cylinder Anvil Rod

5.63" OD = 5.5"

Four orthogonal rod gu ides, 0.44" thick

0.63"

3.87" OD = 2.61"

39.71" OD = 5.5" ID = 4.82"

2.92" OD = 5.5" ID = 2.75" '

2.93" OD = 5.5" ' ID = 2.75"

J KS3

52.82" OD = 2.61" ID = 2.25"

i Scale 1:10

NW Pin

4.68" OD = 2.61"

• ID = 1.37"

2.82" . OD = 2.2"

ID = 1.37"

Figure 2.3 Typical Longitudinal Section of a Safety Hammer.

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Split Spoon Penetration Testing in Gravels Section 2.0

SPT and LPT Details and Correlations

- IHH-g MMmbly « n-0 kg >

• trip mechanism

-140 lb might < 83 5 kg )

• anvil <wWi ahaft: 32-2 kg )

Figure 2.4 Typical Details of a Trip Release Hammer (Clayton, 1990).



NWJ Box Thread

13 mm 76 mm

34 mm Drainage Port

Ball Valve 47 mm

40 mm

Sample Barrel

ID = 64 mm (Without Liner) ID = 61 mm (With Liner) OD = 76 mm

Opening for Sample Catcher

47 mm

39 mm ID = 61 mm OD = 76 mm

Not to Scale

Figure 2.5 N A L P T Split-Spoon Sampler used by U S A C E .


SPT and LPT Details and Correlations

both environmental and geotechnical characterization of gravel deposits in Alaska. The

author participated in an U S A C E correlation research program and subsequently

conducted two similar research programs at different sites. Though test details varied

somewhat between these three research programs, the "typical" North American LPT

(NALPT) hammer weighs 1335 N (300 lb) and is dropped 0.76 m (30") yielding a

maximum possible energy of 1015 J (750 ft-lb), which is 2.14 times the maximum

possible SPT energy. The sampler has an outer diameter of 76.2 mm (3") and an inner

diameter of 61 mm (2.4") including a 1.3 mm (0.05") thick liner. The number of blows

for each 152 mm (6") of penetration are recorded and the blows over the interval 152 mm

(6") to 457 mm (18") are summed for the blow count (N).

The U S A C E uses an empirical correlation proposed by Winterkorn and Fang (1975) to

convert blow counts measured with the North American LPT to equivalent SPT blow

counts. The correlation is based on the "Sampler-Hammer Ratio" (Rs):

R S = 0 D ' - ' D ' (2.,)

where:

ID is the inner diameter of the open shoe

OD and ID are given in inches

W = weight of hammer (lb.)

H = height of hammer drop (in.)

Thus (Rs) is directly proportional to the sampler dimensions (which determine sampler

penetration resistance) and inversely proportional to the hammer potential energy. To

determine the SPT-LPT correlation factor, the (Rs) value is plotted on the cohesionless

sand and silt correlation graph shown in Figure 2.6 and compared to the (Rs) of the SPT

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 2 0 Split Spoon Penetration Testing in Gravels SPT and LPT Details and Correlations

10 r4

5 H

or o

E £ o X I

CL

E

-o 5 4

Very Compact

Burmister Std.

Dense Terzaghi S td .

f t

Energy Standard W H Do Dj Rs Burmister 250 20 3.625 2.930 3.I2X I 0 - 5

Terzaghi 140 30 2.000 1.375 0.895XI0" 5

Sampler Hammer Ro1io,R s,— -

W - Weight of Hammer, pounds H = Height of Drop, inches D 0

S Outside Dia. Sampler, inches Dj= Inside Dia. Sampler, inches Dr= Relative Density, %

10 ~ic> so ioo"

Driving Resistance, B, Blows/ft 500 I000

Figure 2.6 Cohesionless Sand and Silt SPT-LPT Correlation Graph (Winterkorn and Fang, 1975).

-11 -



(denoted "Terzhagi Std." in the figure). The relationship shown in Figure 2.6 can be

approximated by the following equation:

(AO

(AO

The (R s) values of the SPT and the typical N A L P T are 0.895 • 10"5 ft2/lb and 1.017 • 10"5

ft2/lb, respectively, and the predicted SPT-NALPT correlation factor is roughly 0.93.

2.3 Japanese L P T (JLPT)

Kaito et al. (1971) first proposed the use of the hammer and split-spoon sampler shown in

Figure 2.7 for geotechnical characterization of gravel deposits. The Japanese LPT (JLPT)

hammer weighs 981 N (220 lb) and is dropped 1.5 m (59.1") yielding a maximum

possible energy of 1472 J (1084 ft-lb), which is 3.11 times the maximum possible SPT

energy. The sampler has an outer diameter of 73 mm (2.9") and an inner diameter of 50

mm (2") including a 2 mm thick liner. The number of blows for each 152 mm (6") of

penetration are recorded and the blows recorded for the interval 152 mm (6") to 457 mm

(18") are summed for the blow count (N).

Yoshida et al. (1988) compared SPT and JLPT blow counts obtained in a calibration

chamber filled with sands and gravels of varying density. No attempt was made to

measure the efficiency of the hammers (hammer efficiency will be discussed in Section

3.0). Based on the data shown in Figure 2.8, they proposed the following two

correlations:

Nsn=2-NLPT (gravel) (2.3)

NSPT =1.5- NLPT (sand) (2.4)

S / SPT

S JLPT

u.oe /

(2.2)

- 1 2 -



-Box Thread

Drainage Port

Sample Barrel

ID = 54 (Without Liner) ID = 50 (With Liner) OD = 70

30 mm 70 mm

73

Not to Scale

Figure 2.7 J L P T Split-Spoon Sampler (after: Kaito et al., 1971).



Figure 2.8 SPT-JLPT Correlation Data (Yoshida et al., 1988).

-14-



It should be noted that the "gravels" used during the tests are classified as medium to

coarse-grained sands using the Unified Soils Classification (USC) system. Following

Yoshida et al.'s work, a number of technical papers were published regarding the use of

the Japanese LPT (e.g. Tanaka et a l , 1991, Suzuki et al., 1993 and Hatanaka and Uchida,

1996). The approach of these papers has been to develop new correlations between the

JLPT blow count and engineering parameters such as cyclic strength, rather than to

generate equivalent SPT blow counts from JLPT data.

The (R s) value of the Japanese LPT is 0.875 • 10"5 ft2/lb and the corresponding SPT-JLPT

correlation factor is 1.02, which is in poor agreement with Yoshida et al.'s empirical

results.

2.4 Italian LPT (ILPT)

Crova et al. (1993) describe the use of the split-spoon sampler and hammer shown in

Figure 2.9 for geotechnical characterization of sand and sandy-gravel deposits. The trip-

release hammer weighs 5592 N (1256 lb) and is dropped 0.5 m (19.7") providing a

maximum possible energy of 2796 J (2062 ft-lb), which is 5.91 times the maximum

possible SPT energy. The sampler has an outer diameter of 140 mm (5.5") and an inner

diameter of 100 mm (3.9"), including a 5 mm (0.2") thick liner. The sum of blows

required to drive the sampler from 152 mm (6") to 457 mm (18") penetration is the blow

count (N). SPT were also performed in both the sand and sandy-gravel deposits.

Average rod energy values of 60% and 85% of maximum possible energy were measured

for the SPT and ILPT, respectively. Table 2.1 summarizes the results of their

investigation.

-15-



- 1 6 -



Table 2.1 Resu ts of SPT-ILPT Comparison (aft, er. Crovaet al. 1993)

Deposit Number

of tests

N SPT

. ^ 1 ( 6 0 ) SPT D 5 0 (mm) Deposit

Number of

tests N ILPT .^1(60). ILPT

D 5 0 (mm)

1.41 1.14 Po River Sand 35 ± ± 0.2 to 0.6

0.46 0.40

Holocene sand and gravel 97

1.13 ±

0.52

0.89 ±

0.40 1 to 15

Pleistocene 1.38 1.02 sand and 62 ± ± 1 to 5

gravel 0.45 0.36

Crova et al. conclude that the correlation between the SPT and ILPT is close to one i f

both blow counts are corrected to 60% of the maximum hammer potential energy and

corrected for overburden stress.

The (R s) value of the Italian LPT is 2.978 • 10"5 ft2/lb and the predicted SPT-ILPT

correlation factor is 0.44, which is on poor agreement with Crova et al.'s uncorrected

empirical results in column 3 of Table 2.1.

Table 2.2 and Figure 2.10 summarize the details of the LPT systems described in this

section. As noted by Crova et al., the efficiency of the hammer can have a significant

effect on the measured blow counts and resulting correlation factors. Details of energy

transfer during dynamic penetration tests such as the SPT and LPT are discussed in

Section 3.0.



Table 2.2 Summary of SP and LPT Details Identification SPT N A L P T JLPT ILPT

Outer Diameter mm (in.)

50.8 (2)

76.2 (3)

73 (2.9)

140 (5.5)

Inner Diameter

With Liner

mm (in.)

34.9 (1.375)

61.0 (2.4)

50 (2)

100 (3.9) Inner

Diameter No Liner

mm (in.)

38.1 (1.5)

63.5 (2.5)

54 (2.13)

110 (4.3)

Hammer Weight N (lb.)

623 (140)

1335 (300)

981 (220)

5592 (1256)

Drop Height mm (in.)

762 (30)

762 (30)

1500 (59.1)

500 (19.7)

Maximum Potential Energy

J (ft-lb)

473 (350)

1015 (750)

1472 (1084)

2796 (2062) Maximum

Potential Energy % o f SPT 100 214 311 591

R s ft2/lb 0.895 • 10"5 1.017 • 10"5 0.875 • 10"5 2.978 • 10"5

-18-

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Section 3.0 Dynamic Penetration Testing Energy Theory

3. D Y N A M I C P E N E T R A T I O N T E S T I N G E N E R G Y T H E O R Y

In order to allow meaningful comparison of SPT results acquired with different hammers

and operators it is necessary to consistently deliver the same amount of energy from the

hammer to the sampler via the drill rods. For this reason, the mass and drop height of the

SPT hammer were standardized to ensure that the hammer would have a consistent

potential energy before each drop.

As the popularity of the SPT for geotechnical site characterization increased, the number

of hammer and drill rod systems in use also increased. In the 1970's, studies were

published indicating that different hammer and rod systems were not consistently

delivering the same energy, even though the potential energy before each drop was,

ideally, the same for all hammers. It was recognized that different hammers would have

different efficiencies, that is, they would convert different amounts of the initial potential

energy to kinetic energy when dropped. It is now believed that, in addition to fall

efficiency variations between hammers, details of the hammer, anvil rod and drill rod

geometry may affect the amount of the kinetic energy that is transferred to the drill rods.

Schmertmann and Palacios (1979) showed experimentally that the measured blow count

was inversely proportional to the energy delivered to the drill rods for blow counts less

than 50. Seed et al. (1985) and Skempton (1986) suggested that measured blow counts be

corrected to the value that would be recorded if a standard amount of energy had been

transmitted through the rods. A standard value of 60% of the potential energy of the

hammer (60% of 473.4 J = 284 J) was adopted because it was the average value measured

at the time for various rigs. The actual energy measured during the test is converted to an

energy ratio using the formula:

-20-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 3.0 Split Spoon Penetration Testing in Gravels Dynamic Penetration Testing Energy Theory

ER = Measured Energy

•100% (3.1) 473.4 J

and the energy corrected blow count (N 6 0 ) is calculated as follows:

N • ER 60% (3.2)

Following this initiative, researchers and practising engineers began to "calibrate"

hammer and rod systems by measuring the hammer fall velocity or by measuring the

energy contained in the stress wave travelling down the drill rods. Typical E N T H R U

values have been proposed for most hammer types so that the additional cost of energy

monitoring may be avoided. This generalized approach to dealing with energy variations

is questionable because it does not consider details of the hammer and rod system.

During the course of this research, kinetic and stress wave energy were recorded

whenever possible. The theories and practices of measuring kinetic and stress-wave

energy are described below.

3.1 Kinetic Energy of Driving Systems

The kinetic energy of the hammer reaches a maximum at the instant before the hammer

strikes the anvil rod. The magnitude of the kinetic energy can be calculated by entering

the peak velocity of the hammer into the general formula for kinetic energy:

Kovacs and Salomone (1982) used photovoltaic reflective scanners to record hammer

drop height and peak velocity for a large number of donut and safety hammer impacts.

They recorded losses of 21 to 25% of the total potential energy during free fall for donut

hammers and 26% to 31% for safety hammers.

Kinetic Energy = — • Hammer Mass • (Peak Velocity)2 (3.3)

-21 -



Radar systems are more commonly used to measure fall velocity. One such system is the

Hammer Performance Analyzer (HPA) developed by Pile Dynamics Inc. (PDI). The

HPA consists of an antenna that emits a directable cone of radio waves and detects

returning waves reflected off solid objects within the cone. If the object is in motion,

there will be a phase shift between the original and reflected waves (the Doppler effect).

The data acquisition system calculates the velocity of the fastest moving object from the

largest phase shift recorded. This maximum velocity is recorded as a function of time on

a strip chart. The energy ratio calculated from the hammer kinetic energy is denoted

(ERV).

3.2 Stress Wave Theory

Measuring stress wave energy is considered superior to measuring hammer kinetic energy

because energy losses occur during hammer impact and stress wave transmission, after

the hammer kinetic energy has been measured. This section describes basic theory

related to the formation and propagation of stress waves in linear rod systems, two

methods for calculating the energy contained in the stress wave and a stress wave

modelling program that was used by the author during the course of this research.

3.2.1 Characteristics of Stress Waves

Timoshenko and Young (1955) show that the differential equation of motion for a cross

sectional element within a prismatic bar during longitudinal vibration is:

^W-^ (3-4) dt2 dx2

where:

u = longitudinal displacement of a cross section of the bar

x = position along the bar

-22-


t = time

c = stress wave propagation velocity

where f() and g() are arbitrary functions representing stress waves that propagate with

equal but opposite velocities (c and -c) within the bar. When a stress wave passes a point

on the bar, the result is a change in stress and particle velocity. The particle velocity

should not be confused with the stress wave propagation velocity (c) defined above. The

following sign conventions are generally used to describe the force and particle velocity:

• Compressive forces are positive;

• Particle velocities are positive when the resulting particle displacement is in the

direction of increasing (x). During SPT and LPT, this direction is generally assumed

to be along the rod axis towards the sampler (down).

Timoshenko and Goodier (1970) showed that the axial force, F(t), within a single stress

wave propagating in the direction of increasing (x) may be related to the particle velocity,

V(t), as follows:

* 5,120 m/s (16,800 ft/s) for steel

E = Young's Modulus

p = mass density

The general solution of Equation 3.4 is:

u (x,t) = f(x + ct)-g(x-ct) (3.5)

-23-



F{t) = --V(t) c (3.6)

= Z • V(t)

where (A) is the cross-sectional area of the bar and (Z) is called the "impedance" of the

bar. This property is called "force velocity proportionality" and, due to the adopted sign

convention, must be slightly modified for waves travelling in the direction of decreasing

Palacios (1977) provides a thorough description of the application of Equations 3.4 to 3.7

to stress wave propagation within drill rods. Some of Palacios' results are demonstrated

in Appendix A . These results will be used in Section 5.0, 6.0 and 7.0 to assess the quality

of stress wave data recorded during the course of this research.

3.2.2 Application to SPT and LPT Energy Measurement

Measurements of F(t) and V(t) at a point in the drill rods following hammer impact may

be used to calculate the magnitude of the energy transferred from the hammer to the rods.

The energy ratio calculated using the stress wave energy is called the rod energy ratio

(ER r). For a body in motion, the increment of work done over a time interval centred at

time (ti) is given by:

(x):

c (3.7) = -Z-V(t)

dW = F{tx)-dx

= F(tx)-V(tx).dt (3.8)

-24-


By integrating the increment of work over the time it takes the stress wave to pass the

measurement point (T), the total work performed by the stress wave, which is equal to the

transmitted energy (ENTHRU), may be calculated:

If more than one stress wave contributes to the total force and velocity at the

measurement point (e.g. if downward and upward propagating waves are present due to a

reflection below the measurement point), the engineer must subtract the energy of the

upward propagating wave from the energy of the downward propagating wave to

determine the energy absorbed by the soil during sampler penetration. The principal

difference between the two commonly used methods of SPT energy measurement, Force

Squared (FF) and Force Velocity (FV), is that the former cannot differentiate between

stress wave energy travelling down and up the rods.

3.2.2.1 Force Squared (FF) Method

The Force Squared (FF) method of energy calculation is the current industry standard and

is described in A S T M (1991b). The method is based on the assumption that there are no

upward propagating stress waves at the measurement location until the arrival of the

reflection from the sampler/soil interface (at time 2L/c, where L is the length of rods

between the measurement location and soil-sampler interface). In this case, the energy of

the stress wave passing the measurement location is equally divided between strain and

kinetic energy and measurement of either axial force or velocity is sufficient to determine

the transmitted energy (Palacios, 1977). It is easier to measure axial strain than particle

velocity so the velocity term in Equation 3.9 is eliminated using Equation 3.6, resulting in

the following equation for FF energy:

T

(3.9)

-25-


FF ENTHRU = A ' ' ̂ 2 ' A c ]T F(tf • At (3.10)

where:

Ki = load cell position correction factor (tabulated in A S T M , 1991b)

K2 = rod length correction factor (tabulated in A S T M , 1991b)

K c = velocity correction factor (described in A S T M , 1991b)

At = time step between data points

The summation is carried out from the time that the downward propagating stress wave

first passes the measurement point until (2L/c). A high frequency data sampler is used so

that F(t) may be considered constant over the time step (At). The measured (FF) energy is

extrapolated to the value that would be measured if the rod length were infinite by the

correction factors (Ki) and (K2). Clayton (1990) combines (Ki) and (K2) into a single

correction factor (K), assuming exponential decay of the stress wave with time. The (Kc)

correction factor is based on empirical evidence that the theoretical wave propagation

speed (c) is higher than the actual speed so that the (FF) energy summation is halted

before the actual arrival of the reflection from the sampler.

Modern instrumentation typically consists of four electrical resistance strain gauges

bonded to or bolted on a rod of the type used in the rest of the drill string (called a

transducer rod). The transducer rod is usually placed in the string of drill rods directly

below the anvil rod. Piezo-resistive and piezo-electric load cells placed in series in the

drill string may also be used to record force data but it is generally considered desirable to

limit the number of impedance interfaces around the measurement location to minimize

reflections (see Appendix A for a description of the effect of impedance interfaces on

stress waves).

- 2 6 -



3.2.2.2 Force Velocity (FV) Method

As noted in Appendix A , rod strings in the field typically contain rod couplings at 1.5 or

3.0 metre (5 or 10 foot) spacing as well as other impedance interfaces at which the initial

downward propagating stress wave will be partially reflected. Depending on the nature of

the impedance mismatch, the force velocity proportionality assumption of the (FF)

method may be seriously violated. To avoid problems arising from such partial stress

wave reflections, Sy and Campanella (1991a) proposed the use of the (FV) method for

SPT energy measurement (the method was already widely used for pile-driving

applications). The (FV) method allows for the presence of two time-varying stress waves

propagating in opposite directions through the drill rods. Using arrows to represent the

direction of wave propagation, the total force at the measurement point is (F(t)^ + F(f)t),

which is not proportional to the total velocity of (V(t)^ + V(t)T). The product of the total

force and total velocity yields:

(F(t) I +F(t) t)- (V(t) I +V(t) T)= F(t) I -V(t) I +F(t) T -V(t) t

+ F(t)i -V(t)t + F(t)t -V(t) I

The underlined terms on the right side of Equation 3.11 cancel and, because F(t)tV(t)t

must be negative, the total resulting energy measured is that of the downward minus the

upward propagating waves. The formula used in practice to calculate F V energy is:

FVENTHRU = ̂ F(t) • V(t) • At (3.12)

Where, again, (At) is small enough that F(t) and V(t) may be considered constant. The

FV energy is calculated over the entire time trace and, in practice, the maximum

calculated value is used in Equation 3.1 to calculate (Neo)- The FV energy calculated at

(2L/c) is equal to the energy of the downward propagating stress wave minus the portion

-27-


of that energy that has been reflected at impedance interfaces below the measurement

point. When the rod length is very low there may still be significant amounts of energy in

the hammer and anvil rod when the first reflection from the soil-sampler interface arrives

at the measurement point. It is not necessary to derive correction factors like (Ki) and

(K2) because the FV energy continues to be that of the downward propagating wave

minus the upward, regardless of the source of the upward propagating wave.

The same instrumentation used to measure F(t) for the FF method may be used for the FV

method. V(t) is usually obtained by integrating data from accelerometers that have been

bonded to or bolted on the transducer rod. Accelerometers are much more expensive than

the strain gauges used for force measurement so most F V systems include some sort of

damping material between the accelerometer and rod to protect them from damage. It is

generally believed that accelerometers should be reliable to 5000 g (g = gravitational

acceleration) and capable of measuring signal frequencies as high as 1.5 kHz, even with

the damping material. Recent studies at UBC, including this research, suggest that

significantly higher amplitude and frequency capacities may be required to accurately

measure V(t).

3.2.3 Stress Wave Modelling

Stress wave modelling for pile-driving applications was first used to help quantify

hammer efficiency and to estimate the static load capacity of driven piles. The popular

Goble, Rausche, Likins and Associates wave equation analysis program (GRLWEAP)

was used during the course of this research to predict the effect of increasing the energy

delivered to the soil from SPT to LPT magnitudes.

G R L W E A P models piles or drill rods subjected to dynamic loading as series of discrete

elements connected by spring and dashpot pairs, as shown in Figure 3.1. The mass of

each element and stiffness of each spring are determined from the density, elastic

- 2 8 -



mm®

AL "Pi AL

m p i = A(AL)p

Toe Resistance

Shaft Resistance

NOTE:

ksi = soil stiffness at segment i (function of quake and Ru i); R u i = ultimate static resistance at segment i; j s i = Smith damping factor at segment i; and, c d p = pile damping value.

Figure 3.1 GRLWEAP Pile or Rod String Model (after: GRLWEAP, 1997).

- 2 9 -


modulus and cross-sectional area of the pile or drill rod material. Minimal damping is

expected in steel drill rods so a low, empirical value from the G R L W E A P manual

(GRLWEAP, 1997) is generally used. The same approach is used to model the hammer.

The total resistance to pile penetration (R) is divided into static (S) and dynamic (D)

components. It is assumed that the static component is elastic-plastic in nature and is

present during both driving and subsequent static loading. Input parameters are the

ultimate static resistance (R u) and the quake (q), as shown in Figure 3.2. The (R u) and (q)

values are simply another way of stating elastic-plastic material properties.

The dynamic component (D) of the total soil resistance is usually modelled as Smith

damping:

where (j) is the Smith damping factor. Figure 3.2 also shows the effects of Smith

damping on the static elastic-plastic load-displacement curve.

Conceptually, at the beginning of program execution all pile and hammer elements are at

force equilibrium, all pile elements are at rest and all hammer elements are moving with

an assigned velocity. The program calculates the spring and dashpot compression or

extension that occur at existing element velocities over a very small time step. The

resulting net forces that act on each element are used to calculate element-specific

accelerations using Newton's Second Law:

D = j-V.Rt v (3.13)

Acceleration = Force Mass

(3.14)

-30-


Dynamic Penetration Testing Energy Theory

o

Displacement

Figure 3.2 Idealized Soil Response to Static and Dynamic Loading.

-31 -



The new accelerations are applied over the next time step, new element velocities and

displacements are calculated and the analysis is repeated. Iterative modelling of SPT or

pile F(t) and V(t) data allows estimation of (Ru) for pile design purposes. Values of (q)

and (j) recommended by G R L W E A P (1997) for pile-driving analyses are listed in Table

3.1. "Skin" and "Toe" refer to side friction and end bearing parameters.

Table 3.1 Soil Parameters Recommended for use wit) i GRLWEAP (GRLWEAP, 1997).

Soil Type Quake (q) Damping Coefficient (i)

Soil Type Skin mm (in.)

Toe* Skin s/m (s/ft)

Toe s/m (s/ft)

Cohesive 2.5 (0.1) d/120 0.66 (0.2) 0.49 (0.15) Non-cohesive 2.5 (0.1) d/120 0.16(0.05) 0.49 (0.15)

* (d) is the pile diameter, (d / 60) may be more appropriate for silts and fine-grained sands. Toe quake should not be less than 1.5 mm (0.05") for pile-driving applications.

G R L W E A P can be used to model SPT stress wave data i f the modelled soil resistance is

set to zero everywhere except the bottom 30 cm of the pile / drill rods. It is not clear,

however, whether the"soil parameters suggested in Table 3.1, which are based on pile-

driving experience, are appropriate for modelling SPT data. Goble and Abou-Matar

(1992) used an interesting iterative solution technique to back-calculate soil parameters

from SPT F(t) and V(t) data but unfortunately used a research soil model available in

G R L W E A P , limiting the applicability of their results. Sy and Campanella (1991b) used

the parameters recommended in the G R L W E A P manual to predict SPT F(t) and V(t) data

that were in good agreement with field data. Abou-Matar and Goble (1997) were able to

accurately recreate SPT data from a laboratory set-up but soil input was not required as

the sampler was suspended in air. Morgano and Liang (1992) used skin and toe quakes of

2.5 mm (0.1") and 0.5 mm (0.02"), respectively and a value of 0.328 s/m (0.1 s/ft) for

both skin and toe damping. The effect of soil parameters on G R L W E A P results is

addressed further in Section 4.0.

-32-


Section 4.0 Proposed SPT-LPT Correlation Method

4. PROPOSED SPT-LPT C O R R E L A T I O N M E T H O D

The Winterkorn and Fang (1975) correlation procedure described in Section 2.2 correctly

recognizes the importance of the sampler dimensions and input energy but is based on a

limited database and does not consider hammer efficiency. The correlation factors

predicted using the procedure do not agree well with the JLPT and ILPT factors from the

literature. The correlation method proposed in this section is based on the Winterkorn

and Fang technique and ideas proposed by Schmertmann (1979) and Schmertmann and

Palacios (1979). The method is applicable for any combination of hammer and sampler.

4.1 Soil Resistance Considerations

Schmertmann (1979) compared the quasi-static (q-s) penetration resistance acting on an

SPT sampler to that acting on a standard 10.0 cm 2 cone penetration test (CPT)

penetrometer (Figure 4.1). He hypothesized that the force (F) required at the top of the

drill rods to push the SPT sampler at the standard CPT penetration rate of two cm/s could

be estimated from CPT measurements at the same depth using the formula:

where:

Ci = SPT-CPT end bearing correlation factor

A E = SPT end bearing area (10.7 cmz)

C 2 = SPT-CPT friction correlation factor

ID = split-spoon inner diameter (cm)

OD= split-spoon outer diameter (cm)

d = split-spoon penetration depth (cm)

R f = f s / q c

fs = measured CPT friction sleeve stress (N/cm2)

q c = measured CPT tip stress (N/cm )

W' = buoyant weight of SPT drill rods (N)

F = [CrAE+C2 •{ID + OD)-7i-d-RJ[qc-W (4.1)

-33-



(a) SPT (b) CPT

Figure 4.1 Forces Acting on SPT Split-Spoon and Piezocone During Quasi-Static Penetration (Schmertmann, 1979).

-34-



Schmertmann compared CPT data obtained with a Begemann mechanical cone to (F)

measurements obtained in the same soil units and proposed (Cj) and (C2) values of 1.0

and 0.7, respectively. He suggested that the (fs) measurements were too high because of

the design of the mechanical cone and predicted that both (Ci) and (C2) would be roughly

equal to 1.0 for electric cone data. Sy and Campanella (1991b) used this approach to

estimate (R u) values for their G R L W E A P analysis of SPT data.

Adopting this approach for the current objective, the author suggests the calculation of an

equivalent tip bearing area (ATE) as follows:

ATE={CrAE) + (C2-AF-Rf) (4.2)

where:

A E = split spoon end bearing area = (TI / 4) • (OD 2 - ID 2)

Ap = split-spoon frictional area at 305 mm (12") penetration = (ID + OD) • rt • (305 mm)

The purpose of the equivalent tip bearing area is to scale down the large frictional area of

the split-spoon sampler for meaningful comparison with the end bearing area. The

frictional area (AF) is calculated assuming a sampler penetration depth of 305 mm (12")

because this is the average sampler penetration depth during the interval that the blow

count is recorded. (Rf) data is generally not available at gravel sites because CPT

equipment is expensive and easily damaged by coarse particles. (Rf) is typically between

0.002 and 0.005 (0.2% and 0.5%) in cohesionless sands and should be similar for

cohesionless gravel deposits. A n average (Rf) value of 0.35% can be used i f no CPT data

is available.

The manner in which Equation 4.1 accounts for internal and external friction is very

simple and requires further investigation. Paik and Lee (1993) conducted calibration

chamber tests using an instrumented, double-walled, open-ended pipe pile that allowed

-35-



them to measure the total force acting on the external wall of the pile and the force

distribution along the internal wall of the pile during static loading. Their results suggest

that the external lateral earth pressure coefficient (KE) may be considered constant along

the penetrated length of the pile following driving (maximum depth « 0.75 m (2.5')). In

contrast, they conclude that the majority of the internal friction was developed within

three diameters of the pile end and that the internal lateral earth pressure coefficient

decreases with increasing distance from the pile tip. The latter observations were

supported by the results of a similar study by De Nicola and Randolph (1997). Although

the calculation of the internal lateral earth pressure coefficient ( K ^ was based on very

simple assumptions, it is clear that the internal and external stress distributions were

different in these cases and it is probable that internal and external stress distributions

during (q-s) penetration of an SPT sampler would also be different. The empirical

correlation factor (C 2) is likely the most efficient way to account for these internal stress

distributions. Because the majority of internal friction is generated in the open shoe, the

inner diameter of the open shoe should be used in Equation 4.2.

4.2 Energy Input Considerations

Consider the case of an SPT in which 60% of the maximum potential energy is absorbed

by the soil (0.6 • 473 J = 284 J). If an ideal plastic model is assumed (Figure 4.2a), the

energy absorbed by the soil is equal to the sampler displacement (Ad) multiplied by the

ultimate static resistance (R u) and the blow count can be determined from:

where the units of (R u) are Newtons. If an ideal elastic-plastic model is assumed (Figure

4.2b), the energy absorbed by the soil is again equal to the area under the force-

displacement curve and the blow count can be determined from:

7V~ = 03 m

Ad (0.3 m)-Rt

284 J •u (4.3)

= R„ -0.00106

-36-

M.A.Sc. Thesis, Chris R. Daniel The University of Brit ish Columbia Split Spoon Penetration Testing in Gravels

Section 4.0 Proposed SPT-LPT Correlat ion Method

Figure 4.2 Energy Expended During Displacement of (a) Ideal Plastic Soil and (b) Ideal Elastic-Plastic Soil.

- 3 7 -



N = 0.3m

f 284 J q (4.4)

V J

where the units of (R u) and (q) are Newtons and metres, respectively. These two cases

are variations of the G R L W E A P soil model described in Section 3.2.3 for which the

dynamic component of soil resistance (D) has been left out. The case including (D) can

be modelled using GRLWEAP. Figure 4.3 compares Equations 4.3 and 4.4 to the output

of a G R L W E A P SPT analysis using the following soil parameters:

• toe quake = 1.25 mm (0.05");

• skin quake = 2.5 mm (0.1");

• Smith toe damping = 0.492 s/m (0.15 s/ft); and,

• Smith skin damping = 0.164 s/m (0.05 s/ft).

Discontinuous slope breaks in the G R L W E A P data (e.g. Point A in Figure 4.3) are minor

effects of the method used by the program to estimate the blow count. Figure 4.3 clearly

illustrates that energy considerations must include not only the total energy delivered to

the soil but the amount of that energy that is expended overcoming soil elasticity and

dynamic penetration resistance.

Soils with blow counts greater than 50 are generally not of concern for most applications.

In Figure 4.3, the relationship between the predicted blow count (N) and the ultimate soil

resistance (R u) is well represented by a single straight line for blow counts less than 50

and the relationship can therefore be quantified by the slope of the line (N / R u ) . The

ability to fully describe the results of a G R L W E A P analysis using a single number

provides a simple means of comparing analysis results. G R L W E A P analyses of the three

LPT systems described in Section 2.0 were performed using the input listed in Table 4.1

and the same soil parameters used for the original SPT analysis. The analysis output

plotted in Figure 4.4 shows that the LPT data are also reasonably well represented by

-38-



Figure 4.3 Comparison of SPT Blow Counts Predicted Using Ideal Plastic and Ideal Elastic-Plastic Soil Models to G R L W E A P Analysis Results.

-39-



Figure 4.4 G R L W E A P Analysis Results for SPT, N A L P T , J L P T and ILPT.

-40-



linear relationships. Slope breaks similar to Point A are also present in the LPT data but

the deviations appear to be minor compared to the slope variations between the SPT and

the LPT's.

Table 4.1 Hammer, Rod and Sampler Details Used for G R L W E A P Analysis. Detail Units SPT N A L P T JLPT ILPT

Hammer Weight N (lb.)

623 (140) .

1335 (300)

981 (220)

5592 (1256)

Hammer Length cm (in.)

53.3 (21)

69.9 (27.5)

36.8 (14.5)

59.9 (23.6)

Hammer Diameter

cm (in.)

14.0 (5.5)

17.8 (7)

21.1 (8.3)

39.1 (15.4)

Drop Height cm (in.)

76.2 (30)

76.2 (30)

150 (59)

50 (19.7)

ER V % 60 60 78 * 60

E N T H R U ** J (ft-lb)

284 (210)

610 (450)

1140 (844)

1678 (1237)

Rod Length m (ft.)

17.83 (58.5)

17.83 (58.5)

17.83 (58.5)

17.83 (58.5)

Rod Area cm 2

(in 2) 8.0

(1.24) 9.3

(1.44) 10.1

(1-57) 60.6 (9.4)

Sampler Area cm 2

(in.2) 8.8

(1.37) 13.9

(2.16) 18.8

(2.93) 59.4 (9.2)

Sampler Length cm (in.)

45.7 (18)

45.7 (18)

45.7 (18)

45.7 (18)

. Yoshida et al. (1988) to develop SPT-JLPT correlation (Skempton, 1986). For these analyses, ER r was roughly equivalent to ER V in the portion of the rod typically used to measure energy.

Sy and Campanella (1991b) performed a parametric study to determine the effect of the

hammer length, hammer, rod and soil damping values, drill rod couplings, slack at rod

joints, analysis time step, rod element size and soil resistance on G R L W E A P computed

SPT F(t) and V(t) data. They observed that the predicted F(t) and V(t) waveforms were

most sensitive to the geometry of the hammer and rods above the measurement point and

the damping values for the hammer, rod and soil elements. They also observed that the

input soil resistance and hammer efficiency were the most significant factors affecting the

-41 -

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 4.0 Split Spoon Penetration Testing in Gravels Proposed SPT-LPT Correlation Method

predicted blow count and ENTHRU values. An earlier study by McLean et al. (1975)

had also made the latter conclusion.

The author conducted a parametric study to determine the sensitivity of the calculated (N

/ R u ) values to soil parameter variations. Table 4.2 details six sets of soil parameters that

were used to generate (N / R u ) values for the SPT and three LPT's. Cases (a) and (c) are

the values recommended in the G R L W E A P manual (Table 3.1) and the Case (b) values

were used by Morgano and Liang (1992). Cases (d), (e) and (f) demonstrate the effect of

varying the toe quake and skin damping values from those recommended for non-

cohesive soils by G R L W E A P (1997). (N / Ru) values calculated from the analysis

results are summarized in Table 4.3.

Table 4.2 Soil arameters Used for G R L W E A P Parametric Study

Parameter Units Case Parameter Units (a) (b) (c) (d) (e) (f)

Skin Quake (q) mm (in.)

2.5 (0.1)

2.5 (0.1)

2.5 (0.1)

2.5 (0.1)

2.5 (0.1)

2.5 (0.1)

Toe Quake (q) mm (in.)

1.25 (0.05)

0.5 (0.02)

1.25 (0.05)

1.25 (0.05)

2.5 (0.1)

0.5 (0.02)

Skin Damping (J)

s/m (s/ft.)

0.16 (0.05)

0.33 (0.1)

0.66 (0.2)

0.33 (0.1)

0.16 (0.05)

0.16 (0.05)

Toe Damping (J)

s/m (s/ft.)

0.50 (0.15)

0.33 (0.1)

0.50 (0.15)

0.50 (0.15)

0.50 (0.15)

0.50 (0.15)

Skin / Toe Resistance

Distribution % 50/50 25/75 50/50 50/50 50/50 50/50

a) G R L W E A P (1997), non-cohesive soil. b) Morgano and Liang (1992), "various sites' c) G R L W E A P (1997), cohesive soil.

-42-



Table 4.3 (N / R u ) Values Calculated Using G R L W E A P Parametric Study Results.

Test N / R u

Units: bpf / kN (bpf / kin) Average Test Case (a) Case (b) Case (c) Case (d) Case (e) Case (f)

Average

SPT 2.325 (10.340)

2.130 (9.473)

2.851 (12.676)

2.502 (11.125)

2.443 (10.862)

2.252 (10.015)

2.417 (10.749)

N A L P T 0.998 (4.436)

0.946 (4.207)

1.218 (5.416)

1.068 (4.749)

1.025 (4.558)

0.981 (4.363)

1.039 (4.622)

JLPT 0.655 (2.914)

0.606 (2.693)

0.836 (3.715)

0.718 (3.191)

0.681 (3.030)

0.638 (2.838)

0.689 (3.064)

ILPT 0.356 (1.582)

0.328 (1.460)

0.429 (1.907)

0.381 (1.692)

0.372 (1.656)

0.346 (1.538)

0.369 (1.639)

The data in Table 4.3 show that changing the input soil parameters significantly alters the

calculated (N / R u ) values. Of principal interest for the current application, however, is

the ratio of SPT to LPT (N / R u ) values, as it may be assumed that the quake and damping

parameters will not be scale dependent, at least over the range of sampler dimensions

under consideration. Figure 4.5 compares the SPT / LPT ratios calculated for each LPT

using each set of soil parameters and clearly shows that the ratio variations are much

more dependent on the type of LPT than the soil parameters used for the analysis.

The dominant factor controlling the calculated (N / R u ) value is E N T H R U . Figure 4.6

compares the Case (a) (N / R u ) values to ENTHRU for the SPT and each of the LPT's.

The data are well represented by the equations:

N_

Ru

N_

R„

2160 ENTHRU

658 ENTHRU

(Imperial Units)

(Metric Units)

(4.5a)

(4.5b)

which illustrate the inverse proportionality between blow counts and input energy that

was originally observed in the field by Schmertmann and Palacios (1979). Equation 4.5

may be used to predict the (N / R u ) value for any LPT system if E N T H R U is known.

Alternatively, the ratio of SPT to LPT (N / R u ) is simply equal to the ratio of LPT to SPT

ENTHRU, i f inverse proportionality is assumed.

-43 -



8 i

7 -ILPT (average = 6.56)

A Jk.

6 -

5 -

4 -

<~>

J L P T (average = 3.51) o

O

3 -

• • • 2 - NALPT (average = 2.33)

1 - i

a b c d e

Case Identification

Figure 4.5 Sensitivity of Predicted (N / R u) Values to Soil Parameter Variations.

-44-



Figure 4.6 Inverse Proportionality Relationship Between (N / R u) and E N T H R U .

-45-



The fact that the four data points do not fall precisely on a single curve suggests that the

inverse proportionality assumption may only be valid over small ranges of input energy

such as those encountered during SPT's, or that factors other than E N T H R U and the soil

parameters can affect the predicted blow counts. The author conducted an additional

parametric study to determine the effect of hammer geometry and rod cross-sectional area

on (N / R u ). It was found that changing the rod cross-sectional area had a significant

effect on the predicted blow count (Figure 4.7). Schmertmann and Palacios (1979)

present field data acquired with (AW) and (NW) rods that demonstrate this phenomenon.

The steady increase in (N / R u) with rod area shown in Figure 4.7 may be explained by

considering the shape of the down-going stress wave (Abou-matar and Goble, 1997). As

the rod area increases, the peak force of the stress wave and the rate of force "decay"

following the passing of the peak force also increase (Figure 4.8). The soil reaction

force, as modelled by GRLWEAP, can only exceed (Ru) i f damping forces are included

in the total resistance. As the peak force increases, damping forces will increase, energy

transfer efficiency will decrease and the resulting (N / R u ) slope will increase. The

increase in the NWJ rod (N / R u ) with decreasing area below roughly 1.5 in in Figure 4.7

occurs because the (N) vs. (R u) relationships become increasingly non-linear as smaller

rods are modelled. The resulting best-fit relationships tend to over-estimate (N) for low

values of (R u). The data points used to represent the SPT (AW rods) and North American

LPT (NWJ rods) are at the edge of the region where this non-linearity becomes important

but the resulting error appears to be small relative to the ratio difference between the two

systems.

4.3 Synthesis of Proposed Method

The (R u) value is very similar to the quasi-static penetration resistance value (F)

described by Schmertmann (1979). As a first approximation, the blow count for any of

the SPT or LPT systems may be estimated using the equation:

NERA=(N/RU)-F (4.6)

-46 -



1 ' — 1 1 i — 1 — ' — ' — i i

2 3 4

Rod Cross-Sectional Area (in2)

Figure 4.7 Effect of Rod Cross-Sectional Area on Predicted (N / R u ) Values.

-47-



Figure 4.8 Idealized Effect of Rod Cross-Sectional Area on Axial Force Data.

-48-



where (ER A ) is the energy ratio used during the G R L W E A P or equivalent analysis.

Similarly, the correlation factor between the SPT and any of the LPT's may be estimated

by taking the ratio of the two:

(N

6Q)SPT _ (NJK)SPT • FSPT

(NERA)LPT (NIRU)LPT-FLPT

where the standard SPT energy ratio of 60% has been used. Alternatively, since the (N /

R u ) values of the SPT and LPT's basically fall on a single inverse proportionality

relationship, the correlation factor may be predicted using the equation:

(X6Q)SPT _ (ENTRHU) L P T • FSPT

(4.8) (NERA)LPT (ENTHRU)SPT • FL LPT

Referring to Equation 4.1, the ratio of the quasi-static penetration resistances (F) may be

determined entirely from the geometry of the split-spoon samplers i f it is assumed that:

• the buoyant unit weight of the rods is negligible; and,

• the same value of CPT tip resistance (qc) may be used for the SPT and LPT (i.e.

no significant scale effects).

Equation 4.7 and 4.8 then reduce to:

)SPT _ (N/RU)SPT '{ATE)SPT

(KEPJLPT ( N / R J L P T \ A T E ) L P T

( - }

and

(N6Q)SPT _ (ENTRHU)LPT-(ATE)SPT

WERJLPT (ENTHRU)SPT • (ATE) (4.10)

TE JLPT

-49-



which can be used to predict SPT-LPT correlation factors for any LPT i f energy and

dimensional information are available.

4.4 Application of Proposed Method

Table 4.4 summarizes the input data for Equations 4.9 and 4.10 for each of the LPT's

described in Section 2.0 as well as the resulting correlation factor predictions. Table 4.5

summarizes the correlation factors taken from the literature, predicted using the

Winterkorn and Fang (1975) method and predicted using the proposed method.

Table 4.4 Summary of Proposed Correlation Method Input Data and Results

Test A E

(in2) A F

(in2) A T E *

(in2)

Equation 4.9 Equation 4.10

Test A E

(in2) A F

(in2) A T E *

(in2) N / R u

(bpf/kip) 0 ^ 6 0 )sPT

(NER )LPT

ENTHRU (ft-lb)

0 ^ 6 0 )sPT

iÊR )LPT

SPT 1.66 127.2 2.10 10.340 - 210 -N A L P T 2.54 203.6 3.26 4.436 1.50 450 1.38

JLPT 3.46 184.7 4.11 2.914 1.81 844 2.06 ILPT 11.81 354.4 13.05 1.582 1.05 1237 0.95

* Assumes (C 2) = 1.0, R f = 0.0035

Table 4.5 Summary of Observed and Predicted Correlation Factors.

Test Type

Observed Correlation Factors Winterkorn and Fang

Equation 4.9

Equation 4.10 Test

Type Format Material Value

(N)SPT 0 ^ 6 0 )sPT

(NER )LPT

0 ^ 6 0 )sPT

iÊR )lPT

N A L P T - - - 0.93 1.50 1.38

JLPT {N)SPT Sand 1.5 1.02 1.81 2.06 JLPT

Gravel 2.0 1.02 1.81 2.06

ILPT [N\(60)\spt

Sand 1.14

0.44 1.05 0.95 ILPT [N\(60)\spt

Sand and Gravel 0.89

0.44 1.05 0.95 ILPT 1^1(60) \ L P T Sand and

Gravel 1.02

0.44 1.05 0.95

-50-



In all of the cases, the correlation factors predicted using the Winterkorn and Fang

method are lower and therefore more conservative than those calculated using the

proposed method. In fact, the SPT blow counts predicted using the proposed method

would range from 1.5 to 2.0 times those predicted using the Winterkorn and Fang

method. An assessment of which method is correct (or "more correct") should be based

on comparison of predicted and observed correlation factors. Such comparisons are

somewhat limited by the fact that the SPT-JLPT correlation factor was developed using

raw blow counts and the SPT-ILPT correlation factor was developed using blow counts

corrected to a standard energy and overburden pressure (98 kPa).

The observed SPT-JLPT correlation factors are 1.5 to 2.0 times the value predicted using

the Winterkorn and Fang method. The correlation factors predicted using the proposed

method are in good agreement with the observed gravel correlation factor but are higher

than the sand factor. It should be noted that Yoshida et al. (1988) used Tonbi type

hammers for both the SPT and JLPT's that were used to develop their correlation factors.

The correlation factors tabulated in Table 4.5 were calculated assuming SPT and JLPT

energy ratios of 60% and 78%, respectively. If it is assumed that the SPT energy ratio

was 78% (273 fit-lb), the correlation factor predicted using Equation 4.10 decreases from

2.06 to 1.58. Assuming a similar decrease in the correlation factor predicted using

Equation 4.9, the new range of predicted correlation factors becomes 1.39 to 1.58, which

is in good agreement with the observed sand correlation factor of 1.5. The use of sand

versus gravel correlation factors will be discussed in Section 8.0.

Crova et al. (1993) used SPT and ILPT blow counts collected at the same depths to

determine the SPT-ILPT correlation factors. They also state that they used the same

method to correct the SPT and ILPT blow counts to a standard overburden pressure.

Thus, it can be assumed that the applied overburden correction factors do not affect the

ratio of SPT to ILPT blow counts. The observed SPT-ILPT correlation factors are 2.0 to

2.6 times the value predicted using the Winterkorn and Fang method. The correlation

-51 -



factors predicted using the proposed method are in good agreement with all of the

observed correlation factors.

The author participated in three N A L P T field programs to gather additional data for

calibrating the proposed correlation method. The results of these programs are presented

in the next three sections and discussed in Section 8.0.

-52 -


Section 5.0 Kidd2 NALPT Field Program

5. KIDD2 N A L P T F I E L D P R O G R A M

The author conducted a five day field program at a site called "Kidd2" located on the

Fraser River Delta just south of Vancouver, BC. The site is adjacent to an electrical

substation and is the property of the British Columbia Hydro and Power Authority (BC

Hydro). The intent of the program was to acquire as much data as possible to check and

to calibrate the proposed correlation method. To that end, both dynamic and quasi-static

penetration tests were performed using SPT and N A L P T equipment. Comparisons of the

quasi-static test data and CPTU data are presented and used to check the penetration

resistance assumptions of the proposed correlation method in this section. Empirical

correlation factors developed using the dynamic SPT and N A L P T data are also presented

and compared to the correlation factors predicted using the Winterkorn and Fang and the

proposed method in this section.

Kidd2 was selected for this investigation for the following reasons:

• close proximity to the University of British Columbia (UBC);

• extensively characterized during the Canadian Liquefaction Experiment

(CANLEX) and during subsequent research by the UBC Civil Engineering and

Earth and Ocean Sciences Departments;

• anticipated SPT blow count range of 10 to 35 within upper 20 metres, based on

C A N L E X results; and,

• silt over silty sand stratigraphy (Figure 5.1) allows SPT-NALPT comparison

without grain size effects.

One piezocone penetration test (CPTU), two SPT and two N A L P T were performed at the

separations shown in Figure 5.2. Grain size distribution data from test holes LPT9902

and SPT9904 are shown on Figure 5.3.

-53-



SPT9901

O CPT

^ LPT9903 • LPT9902

O SPT9904

I—h 0

—I—I 1.5m

Figure 5.2 Distribution of SPT, N A L P T and C P T U Test Holes at Kidd2.

-55-



100

90

80

70

60

50

40

30

20

10

0

— > •

\ \ \

\\ \ \

\'\ V

\ \ \ \ \ \ \ \ \ \ \ — x 'n \\ N J

w > \ >

1. 100 10 1

Grain Size (mm)

0.1 0.01

Range from SPT9904

Range from LPT9902

Figure 5.3 Kidd2 Grain Size Distribution Data.

-56-



5.1 Drilling Method

The four test holes were drilled by the mud-rotary method using a Simcoe 5000 rig

supplied by Foundex Explorations Inc. A 6.125" OD tricone bit was used to drill to the

first test depth and a 4.75" OD tricone bit was used for further advancement of each of

the test holes. The level of the bentonite drill mud mixture was kept above the GWT to

ensure hole stability. SPT and N A L P T were generally performed at 1.5 m (5') intervals

beginning at 4.9 m (16'). Quasi-static (q-s) penetration tests were performed at selected

depths between dynamic test depths.

5.2 Quasi-Static Penetration Tests

The quasi-static penetration test method and results are presented and discussed below.

5.2.1 Description of Test Method

NWJ drill rods were used to lower the SPT or N A L P T split-spoon sampler to the base of

the test hole prior to each quasi-static test. Vertical pushing force was applied to the

NWJ rods at the surface using a constant flow rate hydraulic ram that was securely

mounted on the rig. Additional reaction force was achieved by installing a 3.05 m (10')

solid stem auger roughly one metre toward the front of the drill rig from the test hole

location. The frame of the rig was securely chained to this anchor and the flow rate of

the hydraulic ram adjusted so that the penetration rate would be two cm/s prior to each

quasi-static penetration test. Plastic sample retainers were used and sample barrel liners

were excluded for all tests.

The axial force in the rods was measured using a strain-gauged N W J rod that was

developed to measure FF and F V energy during dynamic tests. The instrumented rod

was placed in the rod string directly below the pushing head of the hydraulic ram. The

strain-gauge output in volts was recorded as a function of time on a strip chart recorder.

Axial force was calculated from the strip chart data using a linear calibration factor

-57-



developed at U B C by hydraulically loading the instrumented rod and monitoring the

strain gauge output.

5.2.2 Test Results

Figure 5.4 is an example of the strip chart output from a quasi-static SPT split-spoon

sampler penetration test. Table B - l , Appendix B, summarizes the test depth, the C P T U

data recorded at the test depth, the estimated rod weight, the strip chart force recorded at

305 mm (1') sampler penetration and the quasi-static resistance force predicted using

Equation 4.1 for each test. It is noted that the average (Rf) values listed in Table B - l are

reasonably close to the selected average value of 0.35%. Table B - l also lists the

recovery of each test, defined as:

Sample Length Recovery = - 100% (5.1)

Sampler Penetration

Figure 5.5 shows the penetration force recorded at 76 mm (3") intervals for each test.

Figure 5.6 presents the CPTU tip resistance (qt) profile and the predicted quasi-static

resistance profiles for the SPT and N A L P T split-spoon samplers. The predicted

resistance at zero (toe) and 30 cm (12") penetration are plotted on the same graphs. Also

plotted on Figure 5.7 are the measured penetration resistance (including rod weight) at

76, 305 and 457 mm (3", 12" and 18") penetration.

5.2.3 Discussion

The data in Figure 5.6 show that the measured quasi-static resistance forces at 76 mm

(3") penetration are generally close to the predicted toe resistance (i.e. zero penetration)

values but the measured values quickly become larger than the predicted values as

sampler penetration increases. This difference is more apparent when the measured force

is plotted directly against the predicted force, as shown in Figure 5.7. The slope of the

-58-



o

• Sampler Penetration

Figure 5.4 Sample SPT Quasi-Static Penetration Test Strip Chart Output.

-59-



12 15 18 21

Penetration (in.)

Recovery (%)

24 27 30

Figure 5.5 Summary of SPT and N A L P T Quasi-Static Resistance Versus Penetration.

-60-

o

ui re c g O

<8s

CM T3 T3 5

w 0) > 2 O

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0 2 4 6 8 10 12

Predicted Force (kip)

Figure 5.7 Comparison of Measured and Predicted Quasi-Static Penetration Resistance Force.

-62-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 5.0 Split Spoon Penetration Testing in Gravels Kidd2 NALPT Field Program

best-fit relationships shown in Figure 5.7 can be more easily understood i f it is assumed

that (Ci) is equal to (C2) and Equation 4.1 is rearranged as follows:

F + W*= qc-C-\AE+K-d-Rf- (ID + OD)\ (5.2)

in which case the best-fit slopes are equivalent to the constant (C). The values of (C) are

1.2 and 1.46 for the SPT and NALPT, respectively. Thus, it may be appropriate to

rewrite Equations 4.9 and 4.10 as:

(N6JSPT _ (N/RJSPT.\.2-{ATEl

(KERA )NALPT (N/RU)NALPT-\A6-{ATE j S P r - (5.3) ) NALPT

and

(N60)SPT (ENTHRU) NALPT '1-2'(-<4TE)SFT

(A^,)NALPT " (ENTHRU)SPT • 1.46 • (ATE )NALPT

This correction will be referred to herein as the quasi-static penetration resistance

correction factor. Similar corrections to the correlation calculations for the JLPT and

ILPT would require field determination of the (C) value for the particular samplers.

5.3 Dynamic Penetration Tests

SPT and N A L P T penetration tests were performed with energy measurement by the

hammer velocity (radar), FF and FV methods.


Input energy for the SPT was provided by a 640 N (144 lb) safety hammer dropped 76.2

cm (30") for a maximum possible energy of 486.5 J (360 ftlb). The accuracy of the scale

used to weigh the hammer and the control over the drop height are such that it is

reasonable to assume that the maximum possible energy was 475 J (350 ftJb). A 0.61 m

(2') A W transducer rod was attached below the N W anvil rod of the safety hammer and

the rest of the rod string consisted of 1.52 m (5') A W J rods. The split spoon dimensions

- 6 3 -


were within A S T M standards. A plastic sample catcher was used and sample barrel

liners were excluded for all tests. An NWJ transducer rod and rod string were used for

the SPT performed at 18.6 m (61') in SPT9904.

Input energy for the N A L P T was provided by a 1458 N (328 lb) safety hammer dropped

76.2 cm (30") for a maximum possible energy of 1108 J (820 ft-lb). This is a significant

variation from the N A L P T "standard" of 1334 N (300 lb) which will require revision of

the estimated correlation factor. A 0.61 m (2') NWJ transducer rod was attached to the

H W anvil rod of the safety hammer and the rest of the rod string consisted of 3.0 m (10')

N W J rods. The split spoon used had an outer diameter of 7.62 cm (3"), an inner diameter

of 6.1 cm (2.4") in the open shoe and an inner diameter of 6.35 cm (2.5") in the sample

barrel. A plastic sample catcher was used and sample barrel liners were excluded for all

tests.

Both the SPT and N A L P T hammers were lifted and dropped using the rope and cathead

technique with two turns of rope around the cathead. The rope was loosened, not thrown

off the cathead, to initiate hammer drops. Weather conditions were dry for most of the

field program and it was necessary to wet the section of the rope that was in contact with

the cathead to reduce friction. The SPT and N A L P T split spoons were driven 457 mm

(18") and 610 mm (24"), respectively, into the soil at the base of the test holes. The

number of blows required for each 2.54 cm (1") of penetration were recorded for both

test types. Samples were classified in the field, bagged and returned to U B C for storage.

5.3.2 Energy Measurement

Hammer kinetic energy was measured for most of the hammer drops using an HPA

system belonging to Klohn-Crippen Consultants Ltd. Figure 5.8 shows an example of

HPA data gathered during the field program and an annotated, idealized data set. H P A

system calibration consists of holding a vibrating tuning fork in front of the antenna. The

HPA comes equipped with tuning forks that oscillate at 4.88 m/s and 9.76 m/s (16 ft/s

-64-



.RANDOM. NOISE

O o a) ti T a. > S °

) trt »- o> = = .£ U. v v

Zero Velocity Line

. HAMMER DROP

J RANDOM. I NOISE

Peak Acceleration!

JVflo

0.2 s

Figure 5.8 Sample and Idealized H P A Strip Chart Output.

-65-



and 32 ft/s). The system was calibrated at the beginning and end of each field day but it

was never deemed necessary to adjust the calibration factor.

Stress wave data were recorded using a Dynamic Energy Monitoring (DEM) system built

for research applications by the U B C Civil Engineering Department and Northwood

Instruments. The SPT measurement system consisted of a 0.61 m A W transducer rod

that was instrumented with four orthogonal strain gauges to measure force and a bolt-on

Entran 7270A-6K (6000 g) accelerometer. The top of the transducer rod was placed in

the rod strong roughly 1.5 m below the plane of hammer impact. The accelerometer was

mounted roughly 25.4 mm (1") below the strain gauges. A linear calibration factor was

developed from laboratory static load tests to relate the output voltage from the strain

gauges to axial force in the rod. The accelerometer calibration factor was provided by

Entran. A n N W J rod was instrumented in the same manner for use during N A L P T . Both

force and acceleration data were sampled at 40 kHz, yielding a Nyquist Frequency of 20

kHz (i.e. the system is capable of monitoring signals with frequency content as high as 20

kHz). A total of 4000 data points were recorded on each channel for each hammer blow.

The data points were recorded at 0.025 ms intervals, yielding 100 ms of force and

acceleration data per hammer blow. Acceleration was digitally integrated to obtain

velocity.

Figure 5.9 shows the operating screen of the software used to display and store the data

gathered by the D E M . The software automatically plots force and velocity following

each hammer blow. The FF energy calculated at the input (2L/c) time and the maximum

FV energy calculated over the length of the data trace are listed along with the peak force

and peak acceleration on the right side of the operating screen after each blow. The user

inputs sufficient rod length and impedance prior to the test to calculate FF energy using

Equation 3.10 (correction factors K i , K2 and Kc are not applied). FV energy is calculated

using Equation 3.12 and is shown plotted with force and velocity as a function of time in

Figure 5.9 (this option is not available in real time).

-66 -



SPT REVIEW DATA

o z •<

10 15 20 TIME (ms)

25 30 35

FILENAME K9904560.DAT DEPTH ( f t ) 56 . OO

PEAK FORCE|21 . 3 (K i p s ) 1 :

PEAK VEL. 11 0 . 8 ( f t / s ) ' 1

PK. ACCEL. (9)

321 5

FV ENERGY 56 4 ()

F2 ENERGY |55.3 ()

Display Controls FV

For. V e l . E n e r g y

• • • SWEEP EXCLUDED

23] •

SITE LOCATION |Kidd2. Near CANLEX

DRILLERS/RIG |Foundex, SIMCOE 5000, mud rotary, rope and cathead

J DATE |Mar 28, 99]

HOLE # KLPT9904

Figure 5.9 Sample DEM Software Operating Screen.

-67-



5.3.3 Test Results

HPA data were not obtained during SPT performed in SPT9901 above 14 m (46") or

during the SPT performed in SPT9904 at 14 m (46'). Tables B-2 and B-3, Appendix B,

summarize the HPA results from SPT9901 and SPT9904 and LPT9902 and LPT9903,

respectively. The average peak velocity and standard deviation are listed for each SPT

and NALPT. The average peak fall velocity of the SPT safety hammer was 3.14 m/s

(10.3 ft/s), corresponding to an average (ERV) of 65% of the maximum possible SPT

energy. The average peak velocity of the N A L P T safety hammer was higher at 3.42 m/s

(11.24 ft/s), corresponding to an average (ERV) of 78.5% of the maximum possible

energy (1113 J, 820 ft-lb). The calculated standard deviations and observed ranges of

recorded velocity suggest that the apparent greater efficiency of the N A L P T hammer

used in this study was real and repeatable.

Tables B-4 and B-5, Appendix B, summarize the HPA, FF and FV data gathered during

the Kidd2 field program. The force and velocity data were visually reviewed and

obviously erroneous data removed before the average FF and FV energies listed in Tables

B-4 and B-5 were calculated. The most frequently encountered problem was the

occurrence of minor accelerometer baseline shifts during the recording period, indicated

by velocity traces that were essentially linear with non-zero slopes beyond roughly 40

ms.

Rod cross-sectional areas were determined through field micrometer measurements of the

inner and outer rod diameters. In most cases, the rod outer diameter met industry

standards but inner diameters did not. The SPT rod string consisted of an " A W "

transducer rod above " A W J " rods with cross-sectional areas of 7.16 cm 2 and 4.84 cm 2

(1.11 in 2 and 0.75 in 2). The N A L P T rod string consisted of "NWJ" rods with cross-

sectional areas of 9.81 cm (1.52 in').

- 6 8 -


The FF energy method requires the input of a single rod impedance (Equation 3.10).

Table B-4 summarizes FF energy ratios calculated using both the " A W J " rod and " A W "

transducer rod impedances.

Raw blow counts recorded during the Kidd2 field program are summarized in Tables B-4

and B-5. SPT blow counts corrected to 60% of the maximum possible SPT energy using

the FF (AWJ and A W rod area) and FV energy ratios are summarized in Table B-4. K i

and K.2 correction factors were interpolated from the values tabulated in A S T M D 4633-

86. The K c correction was not applied. Raw and stress wave energy corrected blow

counts are plotted as a function of depth in Figure 5.10a. The data in Table B-5 shows

that the N A L P T rod energy ratios are generally around 60%. To minimize errors

associated with large energy corrections, the N A L P T blow counts should be corrected to

a standard energy of 60%. N A L P T blow counts corrected to 60% of the maximum

possible Kidd2 N A L P T energy (60% of 1113 J, 820 ft-lb) using the FF (NWJ rod area)

and FV energy ratios are summarized in Table B-5. As the calculated FF energy ratios

were almost entirely greater than 100%, only the raw and FV energy corrected blow

counts are plotted in Figure 5.10b.

5.4 Discussion of Energy Data

The importance of obtaining accurate values of ENTHRU was illustrated in Sections 3.0

and 4.0. The author assessed the reliability of recorded data by checking repeatability,

calibration factors (when possible), determining upper bounds for calculated energies and

checking force-velocity proportionality.

5.4.1 Data Repeatability

The simplest method of assessing the reliability of energy data is to check repeatability.

Other than poorly functioning measurement equipment, there are a variety of reasons

why dynamic penetration test energy data could lack repeatability including inconsistent

hammer drop height, progressive loosening of rod couplings during testing and variable

soil conditions. Despite these poor odds, data will be presented herein illustrating that

HPA and D E M data recorded during SPT and LPT can be remarkably repeatable.

-69-



N and N 6

10 20

N and N 60

30 40 0 10 20 30 40 50 u -

SPT9901

• • • • SPT9904

2 -

4 -•

6 -A 4 0

-A &

8 -A cm -

A C *

10 - A oAm A »

12 -A CM

A Ok • -

A a

14 -A 0 - »

-A « »

16 - A O * - A OA

18 -A »

A O » -

A CJA

O A

20 -

• N

O N 6 0 (FV)

A N 6 0 (FF, A W J rods)

A N 6 0 (FF, A W rods)

Figure 5.10a Raw and Energy Corrected SPT Blow Counts Versus Depth .

-70-



N and N c N and N 60

• N

O N 6 0 (FV)

Figure 5.10b Raw and Energy Corrected N A L P T Blow Counts Versus Depth.

- 7 1 -

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Split Spoon Penetration Testing in Gravels Section S.O

Kidd2 NALPT Field Program

The HPA data recorded during each SPT or LPT at any given depth was qualitatively

very repeatable. This observation is supported by the calculated velocity energy ratio

standard deviations of three to four percent (Table B-2 and B-3). The author notes,

however, that the strip chart output (Figure 5.8) can only be reliably measured to the

nearest 0.5 mm, corresponding to a resolution of 0.12 m/s (0.4 ft/s). The velocity energy

ratio is proportional to the square of -the velocity and the resulting resolution is

significantly worse. For example, SPT hammer fall velocities of 3.17, 3.29 and 3.41 m/s

(10.4, 10.8 and 11.2 ft/s) are equivalent to velocity energy ratios of roughly 67, 72 and 79

percent, respectively. A large amount of data is required to overcome the effects of this

poor resolution when calculating average values and standard deviations. Though it is

likely not possible to accurately quantify the Kidd2 repeatability because of the size of

the data sets, the observed qualitative repeatability seems to be confirmed by the highly

repeatable D E M data.

Figures 5.11 and 5.12 show the D E M data recorded during each of the hammer blows

within the 152 mm to 457 mm (6" to 18") sampler penetration range at 9.5 m (31') in

SPT9904 and at 18.6 m (61') in SPT9901, respectively. The force data in both figures is

highly repeatable until between — and — . The velocity data contain much more

c c

scatter, presumably because acceleration measurement errors are compounded during

integration, but the trend of the data is still very repeatable at both depths. Figure 5.13

compares the average force and velocity data traces recorded at the two test depths. As

would be expected, the data are in poor agreement following the — time of the test at c

the shallower depth but prior to this time the two force traces are in excellent agreement,

illustrating that the force data were not only highly repeatable at individual test depths but

also between test depths and test holes. The agreement between the two velocity traces is

better than would be expected, based on the appearance of the data in Figures 5.11 and

5.12. This suggests that the scatter observed at each test depth is largely random error

that may be eliminated by using the average data traces.

-72-



Figure 5.11 D E M Output Recorded During Hammer Blows Within the 152 mm to 457 mm (6" to 18") Sampler Penetration Range at 9.5 m (31') Depth in SPT9904.

- 7 3 -



Figure 5.12 D E M Output Recorded During Hammer Blows Within the 152 mm to 457 mm (6" to 18") Sampler Penetration Range at 18.6 m (61') Depth in SPT9901.

-74-



g. 1*: CD p

Q. 1*

N

o o >

Figure 5.13 Comparison of Average Force and Velocity Data Recorded in Two SPT Test Holes at Differing Depths.

-75 -


Figures 5.14 and 5.15 show N A L P T D E M data recorded at 9.5 m (31') in Test Hole

LPT9903 and at 17.1 m (56') in Test Hole LPT9902. The force data is again highly

6L repeatable until roughly — . The velocity data appears to contain less scatter than the

c

SPT data but this is probably because a lower number of hammer blows are plotted.

Figure 5.16 compares the average force and velocity data traces recorded at the two test

2L depths. The repeatability of the data is good up to the — time of the shallower test but

c

not as good as observed during the SPT. This may be due to the higher frequency content

of the N A L P T data, which is visually apparent in Figures 5.14 through 5.16. The two

N A L P T data sets compare reasonably well, however, suggesting that the higher

frequencies are still within the recording capabilities of the measurement equipment.

5.4.2 Calibration Factors

Having established that the HPA and D E M data are repeatable, the author sought to

determine whether the magnitudes of the data were reasonable. The magnitude of any

processed data point is entirely dependent on the calibration factor used to convert the

voltage output of the measurement equipment to the desired engineering units.

The calibration factor of the HPA was easily checked in the field because it was easy to

reproduce the test conditions in a very controlled fashion using tuning forks. It would

also be relatively simple to check the calibration factor of the force transducer in the field

using a high capacity load frame. The force calibration factors were checked in the U B C

laboratory at the beginning and end of the Kidd2 investigation and no significant change

was observed.

Checking the calibration factor of high capacity accelerometers such as those used during

the Kidd2 investigation is very difficult because of the difficulty of recreating test

conditions in a controlled fashion. For example, typical peak accelerations recorded

during the Kidd2 investigation ranged from 5000 to 7000 g. For this reason, calibration

factors provided by the accelerometer manufacturer were used during the Kidd2

-76-



70

• • • i • • • i • i i •i i i—i—i—i—i i i i i -5 0 5 10 15 20 25 30 35

Time (ms)

Figure 5.14 D E M Output Recorded During Hammer Blows Within the 152 mm to 457 mm (6" to 18") Sampler Penetration Range at 9.5 m (31') Depth in LPT9903.

-77-



Figure 5.15 D E M Output Recorded During Hammer Blows Within the 152 mm to 457 mm (6" to 18") Sampler Penetration Range at 17.1 m (56') Depth in LPT9902.

-78-

M.A.Sc. Thesis, Chris R. Daniel The University of Bri t ish Columbia Split Spoon Penetration Testing in Gravels


Time (ms)

Figure 5.16 Comparison of Average Force and Velocity Data Recorded in Two N A L P T Test Holes at Differing Depths.

- 7 9 -



investigation. The use of force-velocity proportionality to check integrated accelerometer

data against the more reliable force data will be discussed in Section 5.4.4.

5.4.3 Quality Control Using Upper Bounds

The most obvious upper bound that can be used to check HPA and D E M calculated

energy ratios is 100%. Although this criterion does not seem very stringent, all of the

N A L P T FF energy ratios are greater than 100% and therefore must be in error (Table B-

5, Appendix B).

The velocity energy ratios calculated from the HPA output provide a more stringent,

though less certain upper bound. A number of authors have observed that the actual

energy available for penetration of the sampler into the soil may be greater than the

velocity energy ratio for very soft soils with low blow counts. The additional hammer

energy available for sampler penetration may be calculated using the formula:

Additional Potential Energy = m ' S • Sampler Set m-g-30"

0.4 ( 5 ' 5 )

= 100% N

The above relationship is illustrated in Figure 5.17. A blow count of three was recorded

during the N A L P T at 4.11 m (13.5 ft) in Test Hole LPT9902. The corresponding

additional potential energy of 13.3% represents the amount by which the measured rod

energy ratio could exceed the velocity energy ratio recorded by the HPA system.

Although the effect of the soil-sampler interaction is not felt at the transducer location

2L 2L before — , some portion of the net rod displacement will already have occurred at —

c c

due to compression of the rods between the measurement point and the sampler. The

minor downward translation of the measurement point that occurs between impact and

-80-



• • • • i • i i i i i i i i i i i i i i 0 5 10 15 20 25 30 35 40 45 50

N

Figure 5.17 Relationship Between Additional Potential Energy Due to Sampler Set and Blow Count.

-81 -



— fails to explain why the N A L P T FF rod energy ratios exceed the velocity energy c

ratios by 20% to 60%.

Figure 5.18 compares the average SPT and N A L P T FV energy ratios to the "corrected"

energy ratio calculated from the sum of the hammer kinetic energy and the additional

potential energy calculated using Equation 5.5. Both the SPT and N A L P T F V energy

ratios are roughly equivalent to 0.82 times the corrected velocity energy ratios but the

scatter in the N A L P T data appears to be high.

5.4.4 Quality Control Using Force-Velocity Proportionality

Force-velocity proportionality is perhaps the most commonly used quality control

technique for D E M data. The technique is based on the assumptions that any stress wave

2 1 reflections recorded at the transducer location prior to — will be minor and that

c Equation 3.6 will continue to be valid despite such reflections.

Figure 5.19 compares the average force and velocity data recorded at 18.6 m (61') in

SPT9904. The velocity has been multiplied by the impedance of the A W transducer rod

to simplify the comparison. If no significant reflections were returned from below the

measurement point and the D E M was functioning correctly, one would expect the force

2L to be equal to the velocity multiplied by the rod impedance until — . This is not the case

c

in Figure 5.19, however, where the velocity is consistently greater than the force in this

time range. The author notes that the first major impedance interface below the

measurement point is the coupling between the A W transducer rod and the A W J drill

rods. The two-way travel time between the measurement point and the interface is 0.2

ms, which is almost instantaneous, compared to the rise time of the velocity. Equations

A.5 and A.6 (Appendix A) indicate that the wave reflected at an A W to A W J interface

would cause a force-velocity divergence of roughly 40% of the original force magnitude

(velocity increases, force decrease). Assuming an initial force magnitude of roughly 16

-82-



Figure 5.18 Comparison of D E M and "Corrected" H P A Energy Data.

- 8 3 -



Figure 5.19 Average SPT Force and Velocity Data Recorded at 18.6 m (61') in SPT9904.

-84-



kip, the anticipated force-velocity divergence is 6.4 kip, which is in good agreement with

the early data in Figure 5.19 and raises important questions about the validity of the

force-velocity proportionality assumption of the FF method.

The FF energy ratios calculated using the A W impedance ranged from 34% to 46% and

were considerably lower than the equivalent FV energy ratios, which ranged from 47% to

68%. In contrast, the FF energy ratios calculated using the A W J rod impedance are in

fair agreement with the FV values, ranging from 51% to 68%. There is a simple

theoretical explanation for this observation. When the downward propagating stress

wave encounters the A W / A W J impedance interface, the force and velocity of the

transmitted and reflected waves can be estimated using Equations A.3 to A.6 (Appendix

A), which are based on requirements of equilibrium and continuity across the interface.

Since the axial force and velocity at the interface would be zero prior to stress wave

transmission, the net force behind the upward propagating stress wave must equal the

force of the transmitted wave to satisfy force equilibrium. Similarly, the net velocity

behind the upward propagating reflected wave must equal the velocity of the transmitted

wave to satisfy continuity. The force of the transmitted wave is equal to the velocity of

the wave multiplied by the impedance of the rod through which the wave is travelling is,

in this case, an A W J rod. Therefore, it is not surprising that using the A W J rod

impedance to calculate the FF energy appears to give the most reasonable answer because

the time for the upward propagating wave is small (0.2 ms) relative to the time period

over which the FF energy is calculated. If the A W / A W J interface was the only major

impedance interface in the rod string, it would be quite reasonable to use the FF method

with the A W J rod area to calculate energy ratios.

Figure 5.20 compares the force and velocity data recorded at 17.1 m (56') in LPT9902.

The velocity has been multiplied by the impedance of the NWJ transducer rod to simplify

the comparison. In this case the drill rods were also NWJ, though the N W J transducer

rod was specifically manufactured for this investigation and may have had slightly

different dimensions than the NWJ drill rods (it is difficult to accurately measure the

inner diameter of " J " series rods because the threads are tapered). Figure 5.20 shows that

-85-



i . . . i . i i i

-1 0 1 2 3 4 5 6 7 8 9 Time (ms)

Figure 5.20 Average NALPT Force and Velocity Data Recorded at 17.1 m (56') in LPT9902.

- 8 6 -



the measured peak force of roughly 65 kip was significantly higher than the equivalent

peak product of velocity and NWJ impedance (roughly 40 kip). The author suspects that

one of the primary causes of this discrepancy is the delayed reaction of the integrated

velocity to major shifts in acceleration. The N A L P T data is a particularly difficult test

case because the peak force is roughly three times higher than the SPT peak force but the

width of the initial force "spike" is only 0.4 ms, compared to 0.7 ms for the SPT data.

As the FF method generated unreasonable N A L P T energy ratios and the quality of the

velocity data is lacking, it is not clear which measured energy should be used to correct

the measured N A L P T blow counts. The HPA data appear to be consistent but do not

account for energy losses during impact and stress wave transmission. It would be

appropriate to use the velocity energy ratios i f it could be assumed that the dynamic

efficiency (r)d) of the hammer and rod system, defined by Skempton (1986) as:

are equivalent for the SPT and NALPT. This assumption would be based on the fact that

safety hammers were used for both types of test. Figure 5.18 shows that both the SPT

and N A L P T dynamic efficiencies are roughly equal to 0.82, though there is much more

scatter in the N A L P T F V energy ratios. It appears that the most reasonable course of

action is to use the N A L P T FV energy ratios to correct the blow counts to a standard

energy. In this case, the N A L P T blow counts should only be compared to the FV energy

corrected SPT blow counts to avoid systematic variations.

5.5 Calibration of Proposed Correlation Method

The N A L P T equipment used during the investigation had slightly different properties

than those listed for N A L P T in Table 4.1. Thus Equation 4.10 or 5.4 should be used to

predict a revised SPT-NALPT correlation factor for the Kidd2 investigation (recall that

ERr

(5.6)

-87-



Equation 5.4 contains the quasi-static penetration resistance correction factor). The input

parameters are:

• ( E N T H R U ) N A L P T = 60% of 1109 J (820 ft-lb) = 665 J (492 ft-lb);

• (ATE)SPT = 13.55 cm 2 (2.10 in 2);

• (ENTHRU )SPT = 60% of 473 J (350 ft-lb) = 284 J (210 ft-lb); and,

• (ATE)NALPT = 21.03 cm 2 (3.26 in 2).

yielding a predicted correlation factor of 1.50 using Equation 4.10, greater than the value

of 1.38 listed in Table 4.5. Equation 5.4 yields a correlation factor of 1.24. The revised

N A L P T (R S ) value of 0.93 • 10"5 ft2/lb yields a correlation factor of 0.97, greater than the

value of 0.93 listed in Table 4.5.

Figure 5.21 compares the measured SPT (N6o) and N A L P T (N(,o), both of which have

been corrected to a standard energy using the calculated FV energy ratios. Each data

point represents the average SPT (Neo) and N A L P T (Nô) and the error bars represent the

range of values recorded at a given depth. The observed correlation factor of 1.4 falls

within the range of 1.24 to 1.50 predicted with the proposed correlation method but is

1.44 times the correlation factor predicted using the Winterkorn and Fang method.

The correlation factor predicted using Equation 4.10 is slightly unconservative until the

1 2 quasi-static penetration resistance correction factor of —— = 0.82 is applied. For this

1.46

reason, the field determination of these correction factors should be undertaken for the

JLPT, ILPT and any other LPT systems prior to predicting correlation factors using the

proposed method. A "typical" value of 0.8 could likely be used in the absence of LPT

specific correction factors.

-88-



40

NALPT N60(FV)

Figure 5.21 Comparison of F V Energy Corrected SPT and N A L P T Blow Counts Recorded at Kidd2.

-89-


Section 6.0 Seward, Alaska NALPT Field Program

6. S E W A R D , A L A S K A N A L P T F I E L D P R O G R A M

The United States Army Corp of Engineers (USACE) conducted an SPT, N A L P T and

DCPT research program near Seward, Alaska in August and September of 1998. The

author participated in the field-work and reporting of the project. The site was located on

the flood plain shared by the Resurrection River and Mineral Creek. Ross et al. (1969)

and McCulloch and Bonilla (1970) describe the effects of the March 27, 1964 magnitude

9.2 earthquake on three highway and three railway bridges which cross the Resurrection

River. The two reports present evidence suggesting that the silty, sandy gravel deposits

in the flood plain partially liquefied during the earthquake. This was considered unusual

because SPT blow counts of 30 to 60 had been recorded in the deposits, which is

unusually high for liquefiable deposits. It was postulated that the presence of gravel

particles was responsible for the high SPT blow counts. The U S A C E research program

was initiated to investigate these "grain size effects".

A total of seven test holes or soundings were completed including:

• SEWA9801 - SPT hole with energy measurement, located roughly 500m

upstream of the main test site;

• SEWA9802 - SPT hole with energy measurement;

• SEWA9803 - N A L P T hole with energy measurement;

• SEWA9804, SEWA9805 and SEWA9807 - DCPT holes; and,

• SEWA9806 - N A L P T hole without energy measurement.

The approximate relative locations of SEWA9802 through SEWA9807 are shown on

Figure 6.1. SEWA9802 and SEWA9803 are the only test holes that can be used to

determine an SPT-NALPT correlation factor. Test Hole SEWA9806 may be useful for

checking the repeatability of the SEWA9803 blow counts, i f it is assumed that the energy

ratios are unchanged between the two holes.

-90-



SEWA9806

0 (NALPT) SEWA9803 (NALPT)

O • SEWA9802 (SPT)

SEWA9804 SEWA9807

SEWA9805 (DCPT) (DCPT)

(DCPT)

1—1—1—1 0 1.5 m

Figure 6.1 Distribution of SPT, N A L P T and DCPT Test Holes at Seward, Alaska Main Test Site.

- 9 1 -

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 6.0 Split Spoon Penetration Testing in Gravels Seward, Alaska NALPT Field Program

Table C - l (Appendix C) summarizes the results of grain size analyses performed on

samples recovered during the investigation. The soils encountered ranged from sandy

silts to poorly graded gravel.

6.1 Drill ing Method

The seven test holes were drilled by the hollow-stem auger method using a track-

mounted Acker Soil Max rig supplied by the USACE. The auger casing had an inner

diameter of 10.8 cm (4.25"). The opening at the base of the casing was sealed with a

three-winged drag bit during drilling. When the hole had been advanced to the desired

test depth, the casing was filled with water and the sand bit was carefully removed. It

was usually necessary to continually pour water into the casing due to the high

permeability of the Resurrection River deposits. SPT and N A L P T were generally

performed at 1.5 m (5') vertical intervals beginning at 4.3 m (14').


Dynamic SPT and N A L P T were performed with energy measurement by the FF and F V

methods. HPA data were only recorded for six SPT and nine N A L P T hammer blows.


Input energy for the SPT was provided by a 609 N (137 lb) safety hammer dropped 76.2

cm (30") for a maximum possible energy of 464.1 J (343 ft-lb). As in Section 5.0, it will

be assumed that the maximum possible energy was the standard 475 J (350 ft-lb). Other

than an " A W " transducer rod, the rod string consisted entirely of " A " rods to a maximum

depth of 18.3 m (60'), beyond which " A W " rods were added to the string directly above

the sampler. The split spoon dimensions were within A S T M standards. Plastic sample

catchers were used and sample barrel liners were excluded during all tests.

Input energy for the N A L P T was provided by a 1307 N (294 lb) safety hammer dropped

86.4 cm (34") for a maximum possible energy of 1129 J (833 ft-lb). As in Section 5.0,

this is a significant variation from the N A L P T "standard" energy of 1017 J (750 ft-lb),

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which will require revision of the estimated correlation factor. Other than an A W

transducer rod, the rod string consisted entirely of 1.52 m (5') long N W J rods. The split

spoon used had an outer diameter of 7.62 cm (3"), an inner diameter of 6.10 cm (2.4") in

the open shoe and an inner diameter of 6.40 cm (2.52") in the sample barrel. Plastic

sample catchers were used and sample barrel liners were excluded during all tests.

Both the SPT and N A L P T hammers were lifted and dropped by the rope and cathead

technique with two turns of a 2.86 cm (1.125") diameter rope around the cathead. The

rope was loosened, not thrown off the cathead, to initiate hammer drops. Weather

conditions during the investigation varied from sunny to hard rain. It was necessary to

wet the section of the rope that was in contact with the cathead to reduce friction during

dry weather. The SPT and N A L P T split spoons were driven 457 mm (18") and 610 mm

(24"), respectively, into the soil at the base of the test holes. Blows per 2.54 cm (1") of

penetration were recorded for both test types. Samples were classified in the field,

bagged and returned to a U S A C E laboratory for gradation testing.

6.2.2 Energy Measurement

The Klohn-Crippen Consultants Ltd. HPA was used to monitor a limited number of

hammer drops during the Seward research program. Stress wave data were recorded for

almost all hammer blows using a Northwood Instruments D E M belonging to BC Hydro.

The BC Hydro D E M was very similar to the D E M used during the Kidd2 program,

consisting of a 0.61 m (2') A W rod instrumented with four orthogonal pairs of strain

gauges to measure force and a specially mounted high capacity accelerometer. The

accelerometer was mounted roughly 12.7 mm (0.5') below the strain gauges. Calibration

factors for the strain gauges and accelerometer were provided by Northwood Instruments.

Both force and acceleration were sampled at 100 kHz, yielding a Nyquist frequency of 50

kHz. 4000 data points were collected on each channel at intervals of 0.01 ms, yielding 40

ms of data per hammer blow. Acceleration was digitally integrated to obtain velocity.

The same D E M software used during the Kidd2 program was used during the Seward

program.

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6.2.3 Test Results

Table B-2, Appendix C, summarizes the HPA results from SEWA9802 (SPT) and

SEWA9803 (NALPT). Peak SPT hammer velocities ranged from 2.56 mis to 2.93 m/s

(8.4 ft/s to 9.6 ft/s). Peak N A L P T hammer velocities were higher due to the increased

drop height and ranged from 3.04 m/s to 3.29 m/s (10 ft/s to 10.8 ft/s). The SPT and

N A L P T velocity energy ratios ranged from 44% to 57% and from 55% to 64%,

respectively.

Tables C-3 and C-4, Appendix C, summarize the D E M results gathered during testing in

SEWA9802 and SEWA9803. The force and velocity data were visually reviewed and

erroneous data were identified using the same criteria used during the Kidd2 investigation

and removed before the average FF and FV energies listed in Table C-3 were calculated.

The SPT rod string consisted of an " A W " transducer rod, " A " and " A W " type rods with

cross-sectional areas of 7.16, 7.74 and 7.61 cm 2 (1.11, 1.20 and 1.18 in 2). SPT FF

energies calculated using the impedances of the " A " rods and the " A W " transducer rod

are listed in Table C-3.

The N W J rods in the N A L P T rod string had a cross-sectional area of 9.16 cm 2 (1.42 in 2).

N A L P T FF energies calculated using the impedances of the " A W " transducer rod and the

"NWJ" rods are listed in Table C-4.

Raw blow counts recorded in SEWA9802 and SEWA9803 are summarized in Tables

C-3 and C-4. SPT blow counts were corrected to 60% of the maximum SPT energy

using the " A " rod and " A W " transducer rod FF energy ratios as well as the FV energy

ratios. Similarly, blow counts were corrected to 60% of the maximum possible Seward

N A L P T energy (60% of 1126 J or 833 ft-lb) using the " A W " and " N W J " rod FF energy

ratios and the F V energy ratios.

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6.3 Discussion

The author had the benefit of experience gained during the Seward research program

when designing and conducting the Kidd2 research program. For example, Kidd2 was

selected as the location of the program because the silty sand stratigraphy would allow

the calculation of correlation factors using data that is free of "grain size effects". In

addition, the number and distribution of test holes and several aspects of the energy

measurement techniques employed at Kidd2 are based on apparent deficiencies of the

Seward results. The effects of these perceived limitations on the Seward data set are

discussed below.

6.3.1 Grain Size Analysis Results

Performing SPT and N A L P T in gravel deposits is not a good way to develop a reliable

SPT-NALPT correlation factor because of grain size effects. Comparison of the grain

size distributions of the samples, however, may provide insight into the effect of gravel

size particles on the measured blow counts. For example, i f it were shown that the grain

size distributions of an SPT and an N A L P T sample obtained at the same depth were

identical, it could be assumed that any differences between the two blow counts were

strictly due to the different energies and the different areas upon which the soil resistance

may act. In contrast, i f the grain size distributions differed beyond the limits of lateral

variability, one could assume that blow count variations were due to grain size effects.

Figures 6.2 and 6.3 compare the percent gravel and mean grain size (D50), respectively, of

each SPT sample to those of the N A L P T samples acquired at the same depths. The best-

fit relationships between the SPT and the two N A L P T data sets are essentially identical in

both figures, suggesting that the grain size distributions at each depth were more

dependent on the size of the sampler than on the lateral variability of the site. The fact

that the slopes of the best-fit lines are less than one indicates that the N A L P T samples

were generally coarser and contained more gravel. The coarsest gravel particles sampled

during N A L P T were between 37.5 mm and 50 mm (1.5" and 2.0"), which would not

- 9 5 -



Figure 6.2 Comparison of Percent Gravel in SPT and N A L P T Samples.

-96-

M.A.Sc. Thesis, Chris R. Daniel The University of Brit ish Columbia Split Spoon Penetration Testing in Gravels

Sect ion 6.0 Seward, Alaska NALPT Field Program

Figure 6.3 Comparison of Mean Grain Size (D 5 0) of SPT and N A L P T Samples.

- 9 7 -



have been sampled by the SPT split spoon because the sampler opening is only 35 mm

(1.375").

6.3.2 Blow Count Repeatability

One major limitation of the Seward data set is the lack of multiple SPT and N A L P T blow

counts at each depth to allow assessment of lateral variability. The SPT data cannot be

compared with confidence due to the large spacing between the two SPT test holes. The

two N A L P T holes cannot be compared because SEWA9806 was completed without

energy measurement. In order to provide some assessment of site variability, Figure 6.4

compares the uncorrected blow counts from the two N A L P T holes, as summarized in

Table 6.1. The plot shows significant scatter between the uncorrected blow counts of the

two N A L P T test holes. The slope of the best-fit relationship indicates that slightly higher

blow counts were recorded in SEWA9803, for which D E M data was collected.

Table 6.1 Comparison of Uncorrected N A L P T Blow Counts.

Average Test Dep th m ( f t )

Seward N A L P T B l o w Count (N) Ave rage Test Dep th m ( f t ) S E W A 9 8 0 2 S E W A 9 8 0 6

4.3 30 16 5.8 14 19 7.3 20 12 9.0 29 43 10.3 38 32 11.9 50 53 13.4 32 8 15.0 11 9 16.5 23 21

18.0 44 47 19.5 31 31 21.1 32 27

22.6 30 26 24.1 26 21

-98-



60

0 10 20 30 40 50 60

SEWA9803 NALPT Blow Count (N)

Figure 6.4 Comparison of Uncorrected N A L P T Blow Counts from SEWA9803 and SEWA9806.

-99-



6.3.3 Energy Data Quality

As discussed in Section 5.4, the principal methods of energy data quality control are the

assessment of data repeatability, checking of calibration factors, comparison of results to

upper bounds and assessment of force-velocity proportionality.

An insufficient amount of data was collected to assess HPA repeatability. Figures 6.5

and 6.6 show SPT D E M data recorded at 18.1 m (59.3') in SEWA9802 and N A L P T

D E M data recorded at 19.6 m (64.3') in SEWA9803. Similar to the Kidd2 data, the SPT

and N A L P T force velocity are highly repeatable until — and reasonably repeatable c

beyond. The SPT and N A L P T velocity data contain more scatter than the force data but

the overall trends of the data are still repeatable.

The calibration of the HPA system was checked once per test hole and was always

determined to be acceptable. The calibration of the D E M force transducer was checked

by Northwood Instruments prior to but not immediately after the Seward program. The

accelerometer calibration factor was provided by the manufacturer and could not easily

be checked independently.

In terms of upper bounds, all of the SPT and N A L P T energy ratios were less than 100%.

The average SPT rod energy ratios at test depths 13.4 m and 15.0 m (44.1' and 49.2')

were low for a safety hammer, ranging from 42% to 47% (Table C-3). These unusually

low values are supported, however, by the six SPT velocity energy ratios calculated at

those depths, which ranged from 44% to 57%.

Table 6.2 compares the average N A L P T rod energies to the available velocity energy

ratios. The FF energy ratios calculated using the " A W " transducer rod area are clearly

unreasonable compared to the velocity energy ratios. This supports the observation in

Section 5.4.4 that it is incorrect to use the area of the transducer rod to calculate FF

energy. The NWJ FF and FV energy ratios are slightly greater than and equal to the

-100-



-is q -20 —

10 15

Time (ms)

20 25 30 35

Figure 6.5 D E M Force and Velocity Data Collected During SPT at 18.1 m (59.3') in SEWA9802.

-101 -



Time (ms)

Figure 6.6 D E M Force and Velocity Data Collected During N A L P T at 19 6 (64.3') in SEWA9803.

-102-



velocity energy ratios, respectively. The blow counts at those depths ranged from 23 to

44, indicating that very little additional energy would have been derived from sampler set

(Equation 5.5). The underlying cause of these borderline impossible results is most likely

the resolution of the various energy measurement systems. For example, it was shown in

Section 5.4.1 that the resolution of the HPA system was in the order of 5%.

Table 6.2 Comparison of N A L 3 T Velocity and Rod Energy Ratios*. Test Average Velocity

Energy Ratio (%)

FF Energy Ratio f (%) FV Energy Ratio (%)

Depth m(ff)

Average Velocity Energy Ratio (%) " A W " Rod Area "NWJ" Rod Area

FV Energy Ratio (%)

16.5 (54.1) 61 87.8 64.1 59.7

18.0 (59.2) 58 94.7 69.2 N . A .

19.6 (64.4) 59 88.3 64.5 59.1

N.A. Not Available N A L P T energy quoted as percent of maximum Seward N A L P T energy 1126 J (833 ft-lb). K i and K 2 factors applied to FF energies

Figures 6.7 and 6.8 compare the average D E M output recorded during the SPT at 18.1 m

(59.3') in SEWA9802 and the N A L P T at 19.6 m (64.3') in SEWA9803, respectively.

The velocity has been multiplied by the impedance of the " A W " transducer rod in both

figures to ease comparison.

The cross-sectional area of the " A " type rods used for the SPT is greater than the area of

the " A W " transducer rod. Based on the reasoning presented in Section 5.4.4, one would

expect that the force would be greater than the velocity for most of the time period from

2L impact to — . Substituting the " A " and " A W " rod impedances into Equations A.5 and

c

A.6 (Appendix A) indicates that the total force-velocity deviation should be in the order

of 8% of the original force magnitude (force increases, velocity decreases). Assuming an

original force of roughly 20 kip, the first deviation should be roughly 1.6 kip. In fact, the

force in Figure 6.8 is equal to or slightly less than the velocity for the majority of the

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Figure 6.7 Average SPT Force and Velocity Data Recorded at 18.1 m (59.3') in SEWA9802.

-104-



Figure 6.8 Average N A L P T Force and Velocity Data Recorded at 19.6 m (64.3') in SEWA9803.

-105-



trace. This discrepancy may be due to incorrect assumptions, measurement error or to a

problem with the resolution of the instrument.

The cross-sectional area of the "NWJ" type rods used for the N A L P T was greater than

the area of the " A W " transducer rod. Substituting the "NWJ" and " A W " rod impedances

into Equations A.5 and A.6 (Appendix A) indicates that the force and velocity should

separate by roughly 24% of the original force magnitude. Assuming an original force of

roughly 25 kip, the first separation should be in the order of 6 kip (force increase,

velocity decrease). In fact, the force is greater than the velocity by 5 to 20 kips in the

early part of the trace. Thus, the predicted and observed deviations are in reasonable

agreement.

Both the force and velocity in Figure 6.8 contain a high frequency sinusoidal signal with

a period of 0.15 to 0.20 ms. The precise distance between the end couplings on the

transducer rod is 483 mm (19") and the two way travel time of a reflection within the

transducer rod would be 0.19 ms. Thus the high frequency content of the Seward

N A L P T D E M data likely results from using a relatively low impedance transducer rod in

an otherwise high impedance rod string.

6.4 Correlation Factor

The N A L P T equipment used during this investigation had slightly different properties

than those listed for N A L P T in Table 4.1 and from those of the Kidd2 N A L P T . Thus

Equation 4.10 or 5.4 should be use to predict a revised SPT-NALPT correlation factor for

the Seward investigation. Equation 5.4 may be used because the Seward and Kidd2

N A L P T split-spoons had the same dimensions. The input parameters for the formulae

are:

• ( E N T H R U ) N A L P T = 60% of 1126 J (833 ft-lb) = 676 J (500 ft-lb);

• (ATE)SPT = 13.55 cm 2 (2.10 in 2);

• (ENTHRU )SPT = 60% of 473 J (350 ft-lb) = 284 J (210 ft-lb); and,

-106-



• (ATE)NALPT = 21.03 cm 2 (3.26 in 2).

yielding a predicted correlation factor of 1.53 using Equation 4.10, greater than the value

of 1.38 listed in Table 4.5 and the revised factor of 1.50 predicted for the Kidd2 NALPT.

Equation 5.4 yields a correlation factor of 1.26. The revised Seward N A L P T (R s) value 5 2

of 0.916 • 10" ft /lb yields a Winterkorn and Fang correlation factor of 0.98, greater than

the value of 0.93 listed in Table 4.5 and the revised factor of 0.97 predicted for the Kidd2

NALPT.

Figure 6.9 compares the SPT and N A L P T (N6o), both of which were corrected to 60% of

the maximum possible energy using the FF energy ratios. The " A " and "NWJ"

impedances were used to correct the SPT and NALPT, respectively. Figure 6.10

compares the SPT and N A L P T (N 6 0 ), both of which were energy corrected using the FV

energy ratios. Each data point in the two figures represents a single test depth at which

both SPT and N A L P T energy corrected blow counts were recorded. The observed

correlation factor of both figures is 1.06, which is below the range of 1.26 to 1.53

predicted with the proposed correlation method but is in good agreement with the

Winterkorn and Fang prediction of 0.98. Note that the range of recorded correlation

factors varied from roughly 0.67 to 1.50 and from 0.74 to 1.73 for the FF and F V energy

corrected blow counts, respectively. It will be shown in Section 8.0 that these variations

correlate reasonably well with grain size.

-107-



NALPT N 6 0 (FF, NWJ Rods)

Figure 6 . 9 Comparison of F F Energy Corrected SPT and N A L P T Blow Counts Recorded at Seward, Alaska Main Test Site.

-108-



N A L P T N 6 0 ( F V )

Figure 6.10 Comparison of F V Energy Corrected SPT and N A L P T Blow Counts Recorded at Seward, Alaska Main Test Site.

-109-


Section 7.0 Keenleyside Dam NALPT Field Program

7. K E E N L E Y S I D E D A M N A L P T F I E L D P R O G R A M

An N A L P T investigation was conducted on April 19 and 20, 1999 at Keenleyside Dam

under the supervision of the author and Dr. John Howie of the University of British

Columbia Civil Engineering Department. The program was conducted using equipment

and staff mobilized by BC Hydro for an extensive investigation of the dam foundation.

Keenleyside Dam is located on the Columbia River near Castlegar, B.C. The dam

consists of an earthfill embankment about 430 m long and three gravity structures with a

length of about 370 m. The earthfill dam (Figure 7.1) is a zoned fill embankment with an

upstream sloping impervious core and a downstream pervious sand and gravel shell.

Sand and gravel portions of the earthfill dam below the original river level were

constructed by bottom dumping from barges and end dumping from trucks to form an

embankment just above river level.

Recent modifications to the seismic design parameters for the area, combined with

concerns regarding the bottom and end dumping construction methods, prompted B C

Hydro to conduct extensive field investigations of the earthfill portions of the dam. One

such investigation is described by Lum and Yan (1994). The main purpose of these

investigations has been to quantify the potential for liquefaction of the foundation

materials including native soils and fill material. There is concern that liquefaction of the

dam foundation could initiate a large-scale failure.

Figure 7.2 shows the grain size envelope for the sand and gravel fill material. Mean grain

sizes ranged from roughly 7 mm to 50 mm and samples typically contained between 60%

and 85% gravel. Liquefaction susceptibility is typically quantified using SPT blow

counts but the grain size distribution curves suggest that the material is too coarse for the

SPT. For this reason, BC Hydro has collected not only SPT but also Becker Penetration

Test (BPT) and shear wave velocity data at Keenleyside Dam. Equivalent SPT blow

-110-



Figure 7.1 Plan View of Keenleyside Dam (Lum and Yan, 1994).



24- !?• 1- IV,- V M "10 "20 "40 «60' I00 «?00 00 -

90 ' \ \ w 60 -

<?A w, - E N V E L O P E F O R ADDOny I U 1 T F I Y

70 -

\ 7o; '. O F 0/ T A

60 -

fa fa SO -

fa ft iO -

fa VA fa 30 *

fa w fa, 20 - m 10 •

'/A 0 -

100 0 1'

100 M i l 1 1 | l l 1 1 1 1 1 1

10 111 i i i i r i 111 i i i i i i

1.0 0.1 .( )I

ASTM 0«2 GRAIN SIZE - mm

B0U10ERS COBBLE GRAVEL SIZE SANO SIZE SILT SIZE | CLAY SIZE SIZE SIZE COARSE | FINE :0ARSE| UEOIUM | FINE FINE GRAINED

Figure 7.2 Grain Size Envelope for Keenleyside Dam Sand and Gravel Fill Material (Lum and Yan, 1994).

-112-



counts were estimated from BPT data using the Harder and Seed (1986) and Sy and

Campanella (1993) methods.

One N A L P T test hole (DH99-20) was completed in the vicinity of test holes DH91-C

(BPT) and DH91-D (SPT), as shown on Figure 7.1.

7.1 Drilling Method

The test hole was drilled by the mud rotary method using a truck-mounted AP-1000 drill

rig. A 12.1 cm (4.75") outer diameter tricone bit was used to drill to each test depth. The

level of the drill mud was kept above the groundwater table to improve hole stability.

Several mud loss events occurred between 8.0 m and 8.5 m (26' and 28') and it was

necessary to install casing to 8.5 m (28'). No additional mud loss occurred below this

depth but it was necessary to re-drill the hole from 11.00 m to 20.95 m (36' to 68.7') due

to "squeezing" of the drill string.


Dynamic N A L P T were performed with velocity and rod energy ratio measurements.

7.2.1 Description of Test Meth od

The same split-spoon sampler and hammer used for the Kidd2 investigation were used at

Keenleyside. The safety hammer was lifted using a winch with a clutch-release. The rod

string consisted of 1.52 and 3.05 m (5' and 10') N W rods. N A L P T were performed at

1.52 m (5') vertical spacing between 3.00 m and 14.90 m (10' and 49') and at 18.00 m

and 21.00 m (59' and 69'). Blow counts per 2.5 cm (1") penetration and sample

descriptions were recorded by BC Hydro personnel (Log included in Appendix D).

The Klohn-Crippen Consultants Ltd. HPA system was used to monitor all hammer drops

below 7.13 m (23.4'). Stress wave data were recorded for all hammer blows except at

7.13 m and 21.0 m (23.4' and 68.8') using the BC Hydro D E M . Both force and

acceleration were sampled at 100 kHz.

- 1 1 3 -



7.2.2 Test Results

Table D - l , Appendix D, summarizes the HPA results from DH99-20. Average peak

hammer velocities ranged from 3.08 to 3.38 m/s (10.1 to 11.1 ft/s). Standard deviations

ranged from 0.15 to 0.21 m/s (0.5 to 0.7 ft/s). Average values and standard deviations of

the velocity energy ratios ranged from 63.9% to 76.5% and from 6.2% to 9.0% of the

maximum Keenleyside N A L P T energy of 1108 J (820 ft-lb), respectively.

Table D-2, Appendix D, summarizes the D E M results gathered during testing in DH99-

20. The force and velocity data were visually reviewed and erroneous data were removed

before the average FF and FV energies listed in Table D-2 were calculated. The most

common problem with the data was minor accelerometer baseline offsets, resulting in

uniform non-zero slopes late in the traces.

The " A W " transducer rod and " N W " rods had cross-sectional areas of 7.16 cm 2 and 9.16

cm 2 (1.11 in 2 and 1.42 in 2), respectively. N A L P T FF energy ratios calculated using the

impedances of the " N W " rods and the " A W " transducer rod are listed in table D-2. K i

and K 2 energy correction factors were interpolated from those tabulated in A S T M

(1991b) and applied to the FF energy corrected blow counts.

Raw N A L P T blow counts recorded in DH99-20 are summarized in Table D-2. Blow

counts corrected to 60% of the maximum possible Keenleyside N A L P T energy (60% of

1108 J, 820 ft-lb) using the " N W " and " A W " rod FF energy ratios and the FV energy

ratios are also listed.

Table D-3 summarizes BPT and SPT data recorded in test holes DH91-3C and DH91-3D.

The FV method was used to correct the SPT blow counts to the standard energy. The

BPT blow counts have been converted to equivalent energy corrected SPT blow counts

using the methods proposed by Harder and Seed (1986) and Sy and Campanella (1993).

-114-



7.3 Discussion of Energy Data

The quality of the energy data may be assessed by checking repeatability, upper bounds

and force-velocity proportionality. HPA calibration factors were checked prior to each

test and D E M calibration factors were provided by Northwood Instruments.

The standard deviation of the HPA velocity energy ratios ranged from 6.2% to 9.0%.

This range is higher than the range of 0% to 5.0% recorded for N A L P T during the Kidd2

investigation, indicating that the hammer fall velocity was more variable using the clutch-

release winch at Keenleyside than the rope and cathead at Kidd2. This result was

anticipated because the driller had considerable difficulty achieving the correct drop

height using the clutch-release system and the hammer was often not falling vertically.

Figure 7.3 shows N A L P T D E M data recorded during hammer blows recorded at 18.30 m

2L (60') depth in DH99-20. The force and velocity data are highly repeatable prior to —

c

and the velocity data is uncharacteristically repeatable later in the trace. Figure 7.4

compares the average force and velocity traces recorded during the N A L P T at 18.30 m

(60') in DH99-20. The velocity has been multiplied by the impedance of the " A W "

transducer rod to ease comparison. It is useful at this point to review the D E M energy

data from the Kidd2 and Seward programs:

• Kidd2 SPT: 7.16 cm 2 (1.11 in 2) " A W " transducer rod with 4.84 cm 2

(0.75 in2) " A W J " rods. Referring to Figure 5.19, the product of the measured velocity and the impedance of the transducer rod was generally higher than the corresponding force. This was attributed to upward propagating tensile reflections from the " A W " / " A W J " interface. The peak force was roughly 20 kips. The FF energy ratios calculated using the impedance of the " A W J " rods were in good agreement with the F V energy ratios.

• Kidd2 N A L P T : 9.16 cm 2 (1.42 in2) "NWJ" transducer rod and rods. Referring to Figure 5.20, the product of the measured velocity and the impedance of the transducer rod was

-115-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 7.0 Split Spoon Penetration Testing in Gravels Keenleyside Dam NALPT Field Program

Figure 7.3 D E M Force and Velocity Data Collected During N A L P T at 18.3 m (60') in DH99-20.

-116-



Figure 7.4 Average N A L P T Force and Velocity Data Recorded at 18.3 m (60') in DH99-20.



generally lower than the corresponding force, particularly within the first force peak. This was attributed to the much higher peak force of roughly 65 kips, which would create a severe loading situation for the accelerometer. A l l calculated FF energy ratios were greater than 100%. The dynamic efficiency calculated using the F V energy ratios was equivalent to the factor calculated using the Kidd2 SPT F V energy ratios data (0.82).

• Seward SPT: 7.16 cm 2 (1.11 in2) " A W " transducer rod with 7.74 cm 2

(1.2 in 2) " A " rods. Referring to Figure 6.7, the product of the measured velocity and the impedance of the transducer rod was generally equivalent to the corresponding force. This was attributed to the relatively minor change in area at the " A W " / " A " interface. The peak force was roughly 20 kips. The FF energy ratios calculated using the impedance of the " A " rods were in good agreement with the FV energy ratios.

• Seward NALPT: 7.16 cm 2 (1.11 in 2) " A W " transducer rod with 9.81 cm 2

(1.52 in2) " A " rods. Referring to Figure 6.8, the product of the measured velocity and the impedance of the transducer rod was generally lower than the corresponding force. This was attributed to upward propagating compressive reflections from the " A W " / " N W J " interface. The peak force was roughly 30 kips. The FF energy ratios calculated using the impedance of the "NWJ" rods were in good agreement with the F V energy ratios.

The theory supporting the use of the rod impedance instead of the transducer rod

impedance to calculate FF energy ratios was presented in Section 5.0. The above review

indicates that this practice produces FF energy ratios that are in good agreement with the

calculated F V energy ratios. The Keenleyside N A L P T D E M data was collected using a

7.16 cm 2 (1.11 in 2) " A W " transducer rod with 9.16 cm 2 (1.42 in2) " N W " rods. Based on

the trends observed at Kidd2 and Seward, one would expect that the magnitude of the

Keenleyside force measurements would generally be greater than the product of the

measured velocity and the impedance of the transducer rod. In contrast, review of Figure

7.4 indicates that the two values are roughly equivalent over the majority of the trace.

Accordingly, a review of Table D-2 reveals that the measured F V energies are in fair

-118-



agreement with the FF energy ratios calculated using the " A W " transducer rod

impedance and are higher than those calculated using the rod impedance.

One explanation for this unexplained trend reversal is that the velocity measurements are

in error, possibly due to an incorrect calibration factor (the possible error is likely not a

result of limited capacity because the peak force was only 35 kips). The velocity energy

ratios calculated using the HPA data can be used to provide an additional assessment of

the quality of the D E M data. Figure 7.5 compares the calculated rod energy ratios (Ki

and K.2 factors applied to FF energies) to the measured velocity energy ratio corrected

using Equation 5.5. The dynamic efficiencies are 0.97, 0.89 and 0.70 for the FV, FF

(NW) and FF (AW) energy ratios, respectively. The dynamic efficiency calculated using

the FV energy ratio is unusually high and supports the suggestion that the D E M velocity

data is in error. As a result, the range of FF energy ratios is likely the only reliable

measurement of energy for the Keenleyside data set.

7.4 Correlation Factor

SPT-NALPT correlation factors calculated using actual SPT blow counts and equivalent

SPT blow counts predicted from BPT data are presented below.

The SPT-NALPT correlation factors predicted for the equipment used at Keenleyside

Dam were 1.24 and 1.50, with and without the empirical quasi-static resistance

correction, respectively. The correlation factor predicted using the Winterkorn and Fang

method prediction was 0.97.

Figures 7.6 and 7.7 compare the FF (AW) and FF (NW) energy corrected N A L P T (N6o)

to the 1991 SPT data, respectively. Each data point compares SPT and N A L P T blow

counts recorded at the same depth. The FF (AW) correlation factor (1.07) is considerably

lower than the range predicted using the proposed method but is in good agreement with

the Winterkorn and Fang prediction. The FF (NW) correlation factor (1.44) is in good

agreement with the range predicted using the proposed method but is considerably higher

than the Winterkorn and Fang prediction. It should be noted, however, that Figures 7.6

-119-



100 n

Corrected Velocity Energy Ratio (%)

Figure 7.5 Comparison of D E M and "Corrected" HPA Energy Data.

-120-



Figure 7.6 Comparison of F V Energy Corrected SPT and F F (AW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside

-121 -



(^WNALPT

Figure 7.7 Comparison of F V Energy Corrected SPT and F F (NW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

-122-



and 7.7 both show a large range of possible correlation factors. Because the results are

not very conclusive, it is likely safest to assumed that the observed SPT-NALPT

correlation factor lies between 1.07 and 1.44.

Figures 7.8 and 7.9 compare the FF (AW) and FF (NW) energy corrected N A L P T (N6o)

to Equivalent SPT blow counts predicted using the Harder and Seed (1986) and Sy and

Campanella (1993) methods. The slopes of the relationships range from 0.47 to 0.81,

much lower than the slopes of the SPT-NALPT relationships. This indicates that the

Equivalent SPT blow counts predicted using the BPT data are generally lower than the

actual SPT blow counts at the same depths. It is remarkable that the range of average

correlation factors in Figures 7.8 and 7.9 does not overlap the range of average

correlation factors from Figures 7.6 and 7.7, considering how broad the two ranges are.

-123-



Figure 7 .8 Comparison of Equivalent SPT Blow Counts from B P T Data and FF (AW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

-124-



4 0

3 5

3 0

2 5

§ 2 0

1 5

1 0

0 H

• Harder and Seed Method ( N 6 O ) S P T = 0 - 6 4 ( N 6 0 ) N A L P T

O Sy and Campanella Method ( N 6 0 ) S P T = 0 .81 ( N 6 0 ) N A L P T

o / >r

/ • y^ O

o y o /

• ° /

• o

1 0 1 5 2 0

( ^ 6 O ) N A L P T

2 5 3 0 3 5 4 0

Figure 7.9 Comparison of Equivalent SPT Blow Counts from BPT Data and F F (NW) Energy Corrected N A L P T Blow Counts Recorded at Keenleyside Dam.

-125-


Section 8.0 Discussion

8. DISCUSSION

The following sections summarize and discuss the results of the three research programs

described herein and address the larger issues of grain size effects and appropriate use of

SPT-LPT correlations.

8.1 Standardization of N A L P T Results

It is difficult to compare the results of the various N A L P T research programs because the

hammer energies were not consistent. There may also have been secondary effects due to

the varying shapes of the downward propagating stress waves. It was demonstrated in

Section 4.2, however, that the former are much more significant than the latter. Thus,

"standardization" of the test results may be achieved using an inverse proportionality

relationship to transform the actual results to those that would have been gathered i f

identical equipment had been used at the three sites. The relationship between the actual

results and the standardized results (indicated by a prime (')) is as follows:

1 6 0 , N A l P T [ ) n a l p t ' 60% • PE ' 60% • PE ' ( 8 - 1 }

or

NALPT NALPT 77 , (8.2)

where (PE) and (PE') are the actual and selected standard maximum potential energies,

respectively. Similarly, the relationship between the actual and standardized correlation

factors is as follows:

-126-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Section 8.0 Split Spoon Penetration Testing in Gravels Discussion

( • ^ 6 0 )sPT _ ( - ^ 6 0 )sPT i^60)NALPT £g )̂

NALPT NALPT NALPT

or

fa 60 )'NALPT (^60 )NALPT Ê

Table 8.1 summarizes the results of applying Equation 8.4 to the observed SPT-NALPT

correlation factors using a standard energy (PE') of 1014 J (750 ft-lb), equivalent to

dropping a 1335 N (300 lb) hammer 0.76 m (30").

Table 8.1 Summary of Observed and Standardized SPT-NALPT Correlation Factors.

Research Program

NALPT. Potent

J

' Maximum lal Energy, (ft-lb)

Energy Measurement Method (Rod Type)

( - ^ 6 0 )sPT

( • ^ 6 0 )NALPT

Research Program

Actual, PE Standard, PE ' SPT N A L P T Actual Standard

Kidd2 1109 (820)

1014 (750) FV FV 1.4 1.28

Seward, Alaska

1126 (833)

1014 (750)

FF (A) FF (NWJ) 1.06 0.95 Seward, Alaska

1126 (833)

1014 (750) FV FV 1.06 0.95

Keenleyside Dam

1109 (820)

1014 (750)

FV FF (AW) 1.07 0.98 Keenleyside Dam

1109 (820)

1014 (750) FV FF (NW) 1.44 1.32

8.2 Performance of Proposed Correlation Method

The performance of the proposed correlation method was originally summarized in Table

4.5. Table 8.2 presents a revised summary that includes the standardized SPT-NALPT

correlation factors.

-127-



Table 8.2 Revised Summary of Observed and Predicted Correlation Factors

Test Type

Observed Correlation Factors Winterkorn and Fang

Equation 4.9 *

Equation 4.10 * Test

Type Format Material Value

{N)SP7.

(N)LPT

C^60 )sPT

(NER ) L P R

C^60 )sPT

iÊR )LPT

C^60 )sPT

{^60 )LPT

Sand 1.28 N A L P T C^60 )sPT

{^60 )LPT

Sand and Gravel

0.95 to 1.32

0.93 1.23 1.13

JLPT {N)SPT Sand 1.5 1.02 1.81 2.06 JLPT

(N)LPT Gravel 2.0 1.02 1.81 2.06

Sand 1.14

ILPT [N\(60)\SPT

Sand and Gravel 0.89

0.44 1.05 0.95 ILPT l^l(60) \ L P T

Sand and Gravel 0.44 1.05 0.95

l^l(60) \ L P T Sand and 1.02

1.05 0.95

Gravel 1.02

predicted correlation factors. applied to SPT-NALPT

The sand correlation factors should be used to check the correlation methods in order to

avoid grain size effects. In all cases, the correlation factors predicted using the

Winterkorn and Fang method are more conservative than those predicted using the

proposed correlation method. The SPT-NALPT and SPT-ILPT correlation factors

predicted using the proposed correlation method ranged from 83% to 96% of the

observed values, while the predictions of the Winterkorn and Fang method range from

39% to 73%. The JLPT correlation factors predicted using the proposed correlation

method range from 121% to 137% of the observed correlation factor, while the prediction

of the Winterkorn and Fang method is 68% of the actual value.

The SPT-NALPT and SPT-ILPT Winterkorn and Fang correlation factors are overly

conservative compared to those of the proposed correlation method. The SPT-JLPT

correlation factors predicted using the proposed method are unconservative and in poor

agreement with the observed sand correlation factor. The Winterkorn and Fang

correlation factor is in equally poor agreement but is, at least, conservative. It is possible

that the SPT-JLPT correlation requires an empirical quasi-static resistance correction,

-128 -



particularly because the JLPT sampler has a relatively thick wall compared to the

N A L P T and ILPT. It should also be noted, however, that there is considerable

uncertainty associated with the observed SPT-JLPT correlation factor because neither the

velocity nor rod energy ratios were recorded. A review of the available grain size data in

Section 8.3 casts additional doubt on the SPT-JLPT correlation factor.

8.3 Grain Size Effects

The following quotes from the literature are indicative of the current perception of grain

size effects:

Ross, Seed and Migliaccio (1969):

"... the presence of gravel sizes in a soil can yield high penetration resistance to small sampling tools even if the relative density of the soil mass is low...."

U.S. National Research Council (1985):

"It is not possible to evaluate the liquefaction susceptibility of [soil containing gravel] using the SPT; the presence of gravel can increase greatly the penetration resistance..."

Rollins, Diehl and Weaver (1997):

"... the [SPT] penetration resistance may be artificially increased due to the size of the gravel particles and because gravel particles may plug the sampler....'

In addition, several researchers recommend the use of "small increment" blow counts,

wherein the blows per inch of sampler penetration are recorded and the lowest recorded

value is multiplied by 12 to obtain a revised blow count. This procedure implies that SPT

blow counts are significantly higher in gravels, presumably due to interaction between

very coarse particles and the sampler. While there is considerable evidence indicating

that SPT blow counts tend to increase with average particle size in sands (Decourt, 1989),

and SPT commonly meet with refusal on very large particles such as boulders, there is

very little data in the literature supporting the assertion that SPT blow counts steadily

-129-



increase between coarse sand and boulder size particles. In fact, some researchers who

have performed SPT in gravel deposits have noted the opposite effect:

Andrus and Youd (1989):

"...the low blow count in the loose gravel at both sites suggest a lack of influence of gravel particles and could not have been increased much due to gravel content...."

in which case the SPT blow counts may be representative or even lower than justified in

coarse-grained soils. Part of the difficulty of assessing "grain size effects", however, is

that it is impossible to determine what the SPT blow count in a gravel deposit "should"

be. For example, Burland and Burbridge (1985) conclude that:

"... an analysis of [settlement records from over 200 sites including 18 gravel sites] indicates that the SPT blow count should be increased by a factor of about 1.25 for the purpose of assessing [gravel and sandy gravel] compressibility..."

It is not possible to say whether the recommended increase of blow counts results from a

general decrease in compressibility with increasing grain size, a decrease in SPT blow

counts with increasing grain size or a combination of the two. For this reason, soil

compressibility is not a suitable performance reference for quantifying grain size effects.

Comparison of SPT data to that of other in-situ tests is one way of providing an arbitrary

performance reference. The ideal in-situ test for comparison would be sensitive to the

strength and deformation parameters of the gravel but insensitive to grain size variations.

Shear wave velocity measurements are derived from relatively large volumes of soil and

thus are likely less sensitive to grain size variations. Comparison of small strain

parameters such as shear wave velocity to large strain test results such as SPT blow

counts is considered questionable, however, due to the non-linear nature of soil

deformation. The principal attraction of LPT data as a performance reference is the

similarity of SPT and LPT equipment. As shown in previous sections, the data in SPT-

LPT comparison plots are often well represented by a simple linear best fit.

-130-



Unfortunately, observed changes in SPT-LPT correlation factors may be due to grain size

effects on the LPT as well as SPT blow counts. It is reasonable to assume that grain size

effects on an LPT sampler would be of a similar nature to those acting on an SPT sampler

(i.e. both blow counts would be higher or lower than justified). For example, an increase

in the observed correlation factor with increasing grain size most likely represents an

increase in SPT blow counts, the severity of which may be partially masked by a similar

increase in LPT blow counts. The LPT blow counts selected as the arbitrary performance

reference should ideally be free of grain size effects. Some measurement of grain size

such as the mean grain size or the portion of the grains that are too large to enter the

sampler can be used to gauge the severity of the anticipated grain size effects and to

determine what size of sampler is required to avoid grain size effects. Table 8.3

summarizes the available grain size information for each of the sites described in the

literature and herein.

Table 8.3 Summary of Available Grain Size Information

Test Type

Research Program

Source of

Sample

Material Type

D 5 0

(mm)

% Coarser than Sampler Inner Diameter Test

Type Research Program

Source of

Sample

Material Type

D 5 0

(mm) SPT LPT

N A L P T

Kidd2 N.A. Sand 0.14 to 0.33 0 0

N A L P T Seward, Alaska N A L P T

Sand and

Gravel 0.9 to 11 Oto 24 N . A .

N A L P T

Keenleyside Dam N.A.

Sand and

Gravel 7 to 50 18 to 57 5 to 45

JLPT Calibration Chamber

Grab Samples

Sand 0.34 0 0 JLPT Calibration

Chamber Grab

Samples Gravel* 1.13 to 1.28 0 0

ILPT Messina, Italy ILPT

Sand 0.2 to 0.6 0 N . A .

ILPT Messina, Italy ILPT Sand

and Gravel

1 to 15 Oto 30 N . A .

N .A. Not Available * This material is not classified as gravel using the USC or BSC systems.

Based on the information in Table 8.3, one would expect that the grain size effect on the

SPT blow counts recorded in sand and gravel at the Seward, Alaska, Keenleyside Dam

-131 -



and Messina, Italy sites would be more significant than those recorded in gravel during

the JLPT calibration chamber tests. In fact, the "gravel" material used to develop the

JLPT correlation factor would not be classified as gravel using the Unified Soil

Classification (USC) or British Soil Classification (BSC) Systems.

Table 8.2 shows that the SPT-NALPT and SPT-ILPT correlation factors decreased with

increasing grain size, supporting the hypothesis that SPT blow counts may actually

decrease with increasing grain size in some portion of the gravel range of soil particles.

It is possible that the increase in observed SPT-JLPT correlation factor with grain size

may have been due to the well documented increase in SPT blow counts with increasing

average particle size in sands.

One major limitation of using correlation factors to quantify grain size effects is the

limited accuracy of the correlation factors. For example, the Seward, Alaska and

Keenleyside Dam correlation plots display considerable scatter. When performing tests

in natural deposits, one must anticipate variations of grain size with depth. Crova et al.

(1993) present an interesting plot comparing the observed SPT-ILPT correlation factor to

the mean grain size of the sample retrieved (Figure 8.1). The data appears to support a

slight decrease in correlation factor with increasing mean grain size, though there is

considerable scatter.

The U S A C E performed grain size analyses of many of the samples retrieved during the

Seward, Alaska research program. Figure 8.2 compares the SPT-NALPT correlation

factor recorded at each test depth to the range of mean grain sizes determined using the

two N A L P T samples collected at each depth. Similarly, Figure 8.3 compares the

correlation factors to the portion of the N A L P T samples that would be too large to enter

the SPT sampler. Unlike the data shown in Figure 8.1, there is no clear relationship

between correlation factor and mean grain size in Figure 8.2. The data in Figure 8.3

show considerable scatter but the average values of the "oversize" portion of the N A L P T

sample correlates reasonably well (r = 0.77) with the observed correlation factors.

-132-



f N H « 0 ) ] S P T 2.0

[ N l ( 6 0 ) l L P r

1.6

1.2

0.8

0.4

"1 < i i i i m | — I I I 11 I I I 1—i | | | in

: Hi f 1 S T D

Moan

J — 1 I I I I I I ! 0.1

1 I I I M I U * I I I M i l l

10 100

dso (mm)

Figure 8.1 Comparison of SPT-ILPT Correlation Factors and Mean Grain Size Data from Messina, Italy (Crova et al., 1993).

-133-



0.1

< co

LU

o

• — i

10

Q)

E ro b

CD c _c f-Q . CO

100

D 5 0 (mm)

Figure 8.2 Comparison of SPT-NALPT Correlation Factors and Mean Grain Size Data from Seward, Alaska Research Program.

-134-



2.0

0.0 - I — i — . — . — p — , — . — . — . — . — , — , — • — i — • — , — P — , — , — , — , — , — , — , — , — I

0 5 10 15 20 25

Portion of NALPT Sample Coarser than S P T Inner Diameter (%, by weight)

Figure 8.3 Comparison of SPT-NALPT Correlation Factors to "Oversized" Portion of N A L P T Samples from Seward, Alaska Research Program.

-135



Based on these results, measurement of the oversize portion of the in-situ soil may be a

better gauge of grain size effects.

No grain size analyses were performed on the samples retrieved at Keenleyside Dam.

The samples collected above and below 14.6 m were identified as gravelly sand and sand,

respectively. Figure 8.4 indicates which data points on the Keenleyside Dam correlation

plot were identified as sand. The fact that the two data points fall on different sides of the

best-fit line indicates that there is no systematic variation of the correlation factor with

grain size, though the available data is very limited.

With regard to the use of "small increment" blow counts, Figures 8.5 and 8.6 show

penetration rate data for the SPT and N A L P T samplers, respectively. The gravel curves

are no less regular than the sand curves, and it would be very difficult to determine which

portions of the curve corresponded to sand versus gravel penetration. For this reason, the

use of "small increment" blow counts appears to be unwarranted, at least at the sites

investigated herein.

8.4 Use of SPT-LPT Correlations

SPT-LPT correlation factors developed in gravel generally differ than those developed in

sands, presumably due to grain size effects. As a result, the only reasonable application

of gravel correlation factors, other than studying grain size effects as described in Section

8.3, is estimating grain size affected SPT blow counts without damaging SPT equipment

on coarse gravel particles.

SPT-LPT correlation factors developed in sand are free of grain size effects. The SPT

blow counts estimated using sand correlation factors and LPT data from gravel deposits

are the blow counts that would have been recorded in a sand deposit i f the LPT blow

counts had been recorded in sand. Whether or not it is appropriate to use the estimated

SPT blow counts as input for empirical design methods that were originally developed

for sands can only be checked by developing soil performance databases. It is quite

-136-



50

0 5 10 15 20 25 30 35 40 45 50

( ^ 6 O ) N A L P T

Figure 8.4 Keenleyside Dam SPT-NALPT Correlation Data (FV Energy Corrected), Sand Versus Gravel Data.

- 1 3 7 -



100

9 12

Penetration (in.)

15 18 21

Figure 8.5 Dynamic SPT Blows versus Penetration Data from Kidd2 and Seward, Alaska Sites.

-138-

M.A.Sc. Thesis, Chris R. Daniel The University of Bri t ish Columbia Split Spoon Penetration Testing in Gravels


100

0 3 6 9 12 15 18 21 24 27

Penetration (in.)

Figure 8.6 Dynamic N A L P T Blows versus Penetration Data from Kidd2 and Keenleyside Dam Sites.

- 1 3 9 -



likely that existing empirical design methods for sands will have to be modified slightly,

just as many sand correlations have been modified for use in non-plastic silts. When

sufficient LPT data is available, it will no longer be necessary to use SPT-LPT

correlations, as the desired gravel parameters may be estimated directly from LPT blow

counts.

-140-


Section 9.0 Conclusion and

Recommendations for Future Research

9. C O N C L U S I O N AND R E C O M M E N D A T I O N S F O R F U T U R E R E S E A R C H

A method for predicting SPT blow counts from LPT blow counts was presented and

checked against an earlier correlation method presented by Winterkorn and Fang (1975)

and against actual correlation factors from the literature and from research programs

described herein. The method accounts for the surface area upon which soil resistance

may act and the actual input energy of the test as opposed to the maximum potential

energy of the hammer. In this regard, the proposed correlation method is better aligned

with current geotechnical practice than the Winterkorn and Fang method.

The method used to predict quasi-static penetration resistance was found to generate

values that were too low for both the SPT and N A L P T samplers. A simple empirical

correction factor of 0.82 was required to correct this error. Application of the proposed

correlation method to samplers other than the N A L P T sampler may require additional

quasi-static penetration testing to develop correction factors for other samplers.

Accurate measurement of the rod energy ratio is very important for any application of

dynamic penetration test results, including the proposed correlation method. The author

observed that the correlation factors generated during the three research programs

described herein were sensitive to the method of dynamic energy measurement (i.e. FF

versus FV), to the assumptions required for the method (e.g. what rod area is used for FF

energy calculation) and to the quality of the data. The author employed assessment of

data repeatability, checking of calibration factors, upper bounds and force-velocity

proportionality as quality control methods. The dynamic energy data were highly

repeatable but the force and velocity magnitudes did not consistently match the

predictions of simple hand calculations. This suggests that the geometry of the hammer

and rods must be considered more explicitly for accurate predictions. In some cases, the

calculated energies were clearly in error and could not be used to correct the measured

blow counts to a standard energy. SPT blow counts were corrected to 60% of the

maximum potential energy (60% of 473 J = 284 J). The average rod energy ratios

- 1 4 1 -




recorded during N A L P T were generally around 60% of the maximum potential energy of

the N A L P T hammer. For this reason, N A L P T blow counts were also corrected to 60%

of the maximum potential energy (60% of 1015 J = 609 J).

The proposed SPT-LPT correlation method generated predictions that compared

favourably with correlation factors from the literature and from the three research

programs describe herein. Excluding the SPT-JLPT correlations, the predictions of the

proposed correlation method ranged from 83% to 96% of the observed correlation factors

while the Winterkorn and Fang predictions ranged from 39% to 73%. The JLPT data is

considered unreliable because the data was not corrected to a standard energy. The

predicted correlation factors were in better agreement with correlation factors observed in

sand than in gravel, presumably because of grain size effects.

Excluding the JLPT data, it was generally noted that the observed correlation factors

decreased with increasing grain size, suggesting that SPT blow counts were decreasing

with increasing grain size in the gravel range of soil particles. This observation is

contrary to the current geotechnical perception that SPT blow counts increase with

increasing grain size in the gravel range of soil particles. The observed SPT-JLPT

correlation factors increased with increasing grain size but the "gravel" material used for

the testing would be classified as coarse sand using the USC and BSC systems.

Based on the above conclusions, the author suggests the following items for future

research:

• additional field testing of the proposed correlation method using a range of

hammers and samplers specifically selected to provide a broad range of predicted

correlation factors;

• SPT and LPT calibration chamber testing with energy measurement to investigate

grain size effects where the grain size distribution can be carefully controlled;

-142-




• additional quasi-static penetration tests using a range of split-spoon samplers to

modify the proposed correlation method so that empirical quasi-static resistance

corrections are not required. This type of investigation may also prove useful for

pile-design applications and;

• development of an empirical relationship between gravel liquefaction

susceptibility chart and LPT blow counts or SPT blow counts predicted using

SPT-LPT correlation factors;

• development of a reliable method for field-checking dynamic energy monitoring

systems; and,

• development of simple software for modelling dynamic energy monitoring system

data. This tool could be used to investigate uncertainties in the FF and F V energy

measurement methods such as which rod area should be used for the FF method,

what should the peak force and velocity be and what are the effects of impedance

mismatches on calculated energy.

-143-

Bibliography

A S T M . 1991a. Standard method for penetration test and split-barrel sampling of soils (D1586-84). In 1991 Annual Book of A S T M Standards, sect. 4, vol. 04.08. A S T M , Philadelphia, pp. 232-236.

A S T M . 1991b. Standard test method for stress wave energy measurement for dynamic penetrometer testing systems (D4633-86). In 1991 Annual Book of A S T M Standards, sect. 4, vol. 04.08. A S T M , Philadelphia, pp. 872-875.

Abou-Matar, H . 1990. Evaluation of Dynamic Measurements on the Standard Penetration Test. Thesis presented to the University of Colorado at Boulder in partial fulfillment of the degree of MS.

Abou-matar, H. and Goble, G.G., 1997. SPT dynamic analysis and measurements. A S C E Journal of Geotechnical and Geoenvironmental Engineering, 123(10): 921-928.

Andrus, R.D. and Youd, T.L., 1989. Penetration tests in liquefiable gravels. Proceedings, 12 t h ICSMFE, Rio De Janeiro, Balkema, Rotterdam, Volume 1, pp. 679-682.

Burland, J.B. and Burbridge, M.C. , 1985. Settlement of foundations on sand and gravel. Proceedings, Institution of Civil Engineers, Part 1, December, 78: pp.1325-1381.

Clayton, C.R.I. 1990. SPT energy transmission: theory, measurement and significance. Ground Engineering, 23(10): 35-43.

Crova, R., Jamiolkowski, M . , Lancellota, R. and Lo Presti, D.C.F., 1993. Geotechnical characterization of gravelly soils at Messina site: selected topics. Predictive Soil Mechanics, Houlsby and Schofield, Ed., Thomas Telford, London, pp. 199-218.

Decourt, L, 1989. The standard penetration test, stateOof-the-art report. Proceedings, 12 t h ICSMFE, Rio De Janeiro, Volume 4, pp 2405-2416.

De Nicola, A . and Randolph, M.F., 1997. The plugging behaviour of driven and jacked piles in sand. Geotechnique, 47(4): 841-856.

Goble, G.G. and Aboumatar, H. , 1992. Determination of wave equation soil constants from the standard penetration test. Proceedings, Fourth International Conference on the Application of Stress-wave Theory to Piles, The Hague, The Netherlands, pp. 99-103.

Goble Rausche Likins and Associates, Inc. (GRLWEAP), 1997. G R L W E A P Manual, Version 1997-1, Cleveland, Ohio.

-144-

Harder, L.F. Jr. and Seed, H.B., 1986. Determination of penetration resistance for coarse-grained soils using the Becker hammer drill. Report No. UCB/EERC-86/06, University of California, Berkeley, USA, 118p.

Hatanaka, M . and Uchida, A. , 1996. Empirical correlation between penetration resistance and internal friction angle of sandy soils. Soils and Foundations, 36(4): 1-9.

Kaito, T., Sakaguchi, S., Nishigaka, Y. , Miki , K. and Yukami, H. , 1971. Large Penetration Test. Tsuchi-to-Kiso, 19(7): 15-21 (in Japanese).

Kovacs, W.D. and Salomone, L .A. 1982. SPT hammer energy measurement. A S C E Journal of the Geotechnical Engineering Division, 108(GT4): 599-620.

Lum, K . Y . and Yan, L. , 1994. In-situ measurements of dynamic soil properties and liquefaction resistance of gravelly soils at Keenleyside Dam. Ground Failures Under Seismic Conditions, A S C E Geotech. Special Pub. No. 44, pp. 221-240.

McCulloch, D.S. and Bonilla, M.G. , 1970. Effects of the earthquake of March 27, 1964, on the Alaska Railroad. Geological Survey Professional Paper 545-D, United States Government Printing Office, Washington.

McLean, F.G., Franklin, A . G . and Dahlstrand, T.K., 1975. Influence of Mechanical Variables on the SPT. Proceedings, Conference on In Situ Measurement of Soil Properties, A S C E , Volume 1, pp. 287-318.

Morgano, C M . and Liang, R., 1992. Energy transfer in SPT - Rod length effect. Proceedings, Fourth International Conference on the Application of Stress-wave Theory to Piles, The Hague, The Netherlands, pp. 121-127.

Paik, K. and Lee, S., 1993. Behavior of Soil Plugs in Open-Ended Model Piles Driven into Sands. Marine Georesources and Geotechnology, Vol . 11, pp. 353-373.

Palacios, A. , 1977. The Theory and Measurement of Energy Transfer During Standard Penetration Test Sampling. Thesis presented to the University of Florida in partial fulfillment of the degree of Doctor of Philosophy.

Robertson, P.K., Woeller, D.J. and Addo, K.O. , 1992. Standard penetration test energy using a system based on the personal computer. Canadian Geotechnical Journal, 29: 551-557.

Rollins, K . M . , Diehl, N.B. and Weaver, T.J., 1998. Implications of V S -BPT (Ni)60

correlations for liquefaction assessment in gravels. Second International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, Seattle Washington, pp. 506-517.

-145-

Ross, G.A., Seed, H.B. and Migliaccio, R.R, 1969. Bridge foundation behavior in Alaska Earthquake. Journal of the Soil Mechanics and Foundations Division, Proceedings of the American Society of Civil Engineers, 95(SM4): 1007-1036.

Schmertmann, J.H., 1979. Statics of SPT. A S C E Journal of the Geotechnical Engineering Division, 105(GT5): 655-670.

Schmertmann, J.H. and Palacios, A . 1979. Energy Dynamics of SPT. A S C E Journal of the Geotechnical Engineering Division, 105(GT8): 909-926.

Seed, H.B., Tokimatsu, K., Harder, L.F. and Chung, R . M . 1985. Influence of SPT procedures in soil liquefaction resistance evaluations. A S C E Journal of the Geotechnical Engineering Division, 111(GT12): 1425-1445.

Skempton, A.W. 1986. Standard penetration test procedures and effects in sands of overburden, relative density, particle size, aging and overconsolidation. Geotechnique, 36(3): 425-447.

Suzuki, Y . , Goto, S., Hatanaka, M . and Tokimatsu, K. , 1993. Correlation between strengths and penetration resistances for gravelly soils. Soils and Foundations, 33(1): 92-101.

Sy, A . and Campanella, R.G., 1991a. An alternate method of measuring SPT energy. Proceedings, Second International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, St. Louis, Mo., pp. 499-505.

Sy, A . and Campanella, R.G., 1991b. Wave equation modeling of the SPT. A S C E Geotechnical Engineering Congress, Boulder, Colorado, McLean, Campbell and Harris Ed., A S C E Geotechnical Special Publication. No. 27, Vol . 1, pp. 225-240.

Sy, A . and Campanella, R.G., 1993. BPT-SPT correlations with consideration of casing friction. Proceedings, 46 t h Canadian Geotechnical Conference, Saskatoon, Saskatchewan, pp. 401-411.

Tanaka, Y. , Kudo, K. , Kokusho, K. and Yoshida, Y. , 1991. Dynamic strength of gravelly soils and its relation to the penetration resistance. Proceedings, Second International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, St. Louis, Mo., pp. 399-406.

Timoshenko, S. and Young, D.H., 1955. Vibration Problems in Engineering, D. Van Nostrand Company, New York.

U.S. National Research Council, 1985. Liquefaction of soils during earthquakes, National Academy Press, Washington, D . C , 240p.

-146-

Winterkorn, H.F. and Fang, H., 1975. Foundation Engineering Handbook, Van Nostrand Reinhold Company, New York.

Yoshida, Y . , Motonori, I. and Kokusho, T., 1988. Empirical formulas of SPT blow-counts for gravelly soils. Proceedings, ISOPT-1 for Penetration Testing, pp. 381-387.

- 1 4 7 -

A P P E N D I X A

STRESS W A V E F O R M U L A E

- 1 4 8 -

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Split-Spoon Penetration Testing in Gravels

Appendix A Stress Wave Formulae

S T R E S S W A V E F O R M U L A E

Palacios (1977) presents a detailed review of the use of the one-dimensional wave

equation to describe the formation and propagation of stress waves in SPT drill rods. The

results of his review include a number of simple, closed form solutions for stress wave

magnitudes that are based on equilibrium and continuity requirements. These solutions

can be used to assess the quality of stress wave data recorded in the field and are

presented herein using the example of a simple hammer striking a simple rod. A l l of the

solutions are based on the assumption that there are no energy losses during stress wave

formation or propagation.

Hammer Impact

Figure A . l illustrates several stages in the formation and propagation of stress waves

within a simple hammer and anvil system during and following hammer impact. The

hammer and anvil are constructed of the same, homogenous material. A transducer

element for recording force and velocity versus time is indicated near the bottom of the

anvil rod.

In Figure A . l a , the hammer is falling with uniform velocity (Vj) and the anvil rod is at

rest. There are no axial forces in the hammer or anvil rod. When the hammer strikes the

anvil rod, the impact surface of the hammer must decelerate and the impact surface of the

anvil rod must accelerate so that the velocities of the two surfaces are equal (continuity

requirement). This is a dynamic problem so it is inappropriate to treat the hammer and

anvil as rigid bodies. Instead, the surface accelerations are accommodated by elastic

strain within the two bodies on either side of the plane of impact. The magnitude of the

resulting axial forces must satisfy force equilibrium across the plane of impact and may

be calculated as follows:

-149-



Reflection at free end

Hammer Velocity

Anvil Rod (Zero Velocity)

Reduced fall velocity

Figure A . l Stages in the Formation and Propagation of Stress Waves Within a Simple Hammer and Anvil System.

-150-



F = Z R f

V

, Z R

z H J

(A.1)

V = ( z N

z 'H J

(A.2)

where:

ZH = hammer impedance

Z R = anvil rod impedance

In Figure A . l b , the hammer has struck the anvil rod and equal lengths of material on

either side of the plane of impact are strained (recall that the wave propagation velocity,

c, is a function of the Young's modulus and mass density but not the cross sectional

area). The resulting particle velocity of the material between the plane of impact and the

hammer stress wave front is equal to the sum of the original hammer fall velocity (Vj)

and the velocity determined using Equation A.2. The particle velocity of the material

between the plane of impact and the anvil stress wave front is equal to the force

calculated using Equation A . l divided by the anvil impedance. The two velocities are

equal. The force in the strained material between the two stress wave fronts can be

calculated using Equation A . l and would be positive (compressive) in this case. At the

two interfaces between the strained and unstrained material there are large force

imbalances that rapidly decelerate and accelerate hammer and anvil particles,

respectively, to the translational particle velocity of the strained material. It is common

practice to assume that the interfaces are normal to the rod axis (i.e. wave propagation is

assumed to be one-dimensional).

In Figure A . l c , the upward propagating stress wave arrives at the top of the hammer.

The requirement of the resulting "free-end reflection" is that the total force at the top of

the hammer is zero, so the stress wave is reflected with equal but opposite force (tension).

-151 -



The particle velocity due to the new reflected wave is also negative. The new, total

particle velocity behind the downward propagating stress wave is equal to the sum of the

initial hammer fall velocity (Vj), the negative particle velocity of the original stress wave

and the equal negative particle velocity of the reflected wave. This velocity will not be

zero unless the hammer and anvil impedance are equal.

When the reflected wave reaches the plane of impact (Figure A.le) , the hammer will be

momentarily stress free and moving with uniform velocity, similar to the situation in

Figure A . l a . The system will then repeat the stress wave propagation sequence with

lower magnitude stress waves due to the reduced "impact" velocity of the hammer.

Figure A.2 illustrates the shape of the force and velocity traces that would be recorded by

the instrumentation package mounted on the hypothetical system in Figure A . l i f the

anvil were semi-infinite in length. If the velocity trace were multiplied by the impedance

of the anvil rod it would plot directly over the force trace because of force-velocity

proportionality. The force and velocity magnitude decrease in steps, the duration of

which are equal to twice the length of the hammer (LH) divided by the velocity of the

wave front (c). The magnitudes of the force and velocity step decreases (i.e. the "rates of

decay") following the peak value are a function of the ratio of hammer to anvil

impedance.

Impedance Interfaces

Stress wave data recorded in the field rarely looks like the data shown in Figure A.2

because actual hammers and rod strings are usually more complex than the simple

arrangement shown in Figure A . l (see typical field data presented in Sections 5.0, 6.0 and

7.0). The complexity of a hammer or rod string refers to the number of locations at

which the impedance of the material changes due either to a change in cross sectional

area, Young's modulus or material density. For example, rod strings typically consist of

a series of 1.5 or 3.0 metre (5 or 10 foot) rods. The couplings between rods represent

local changes of impedance. When a stress wave encounters an impedance interface, the

-152-



2L|_| / c L|_| = Length of Hammer

Figure A.2 Hypothetical Force and Velocity Data from Simple Hammer and Anvil System.

-153-



total energy of the incident wave is divided between the stress wave transmitted through

the interface and a second, reflected stress wave (Figure A.3). The force and velocity of

the transmitted (FT, VT) and reflected (FR, VR) waves are functions of the incident wave

force and velocity (Fj, Vj):

2-R

FT = \ Z I J

.3 Z i J

(A.3)

( Z A

1 + ^ z 1 J

(A.4)

(z2 -^--1 u f zA 1 + - ^

- (A.5)

V, •

vD = 1 - ^

z 1 J

z ^ 1 + ^

(A.6)

The derivations of Equations A.3 to A.6 are based on force equilibrium and continuity

requirements. Both reflected and transmitted waves exhibit force-velocity

proportionality, when propagation direction is accounted for. Equations A.3 to A.6 are

also valid for incident waves propagating up the rods, as long as the material is

propagating from a material with impedance (Zi) into a (Zi) material. The free-end

reflection case illustrated in Figure A . l c is a special case of a wave approaching an

interface in which (Zi) is equal to zero. The case of a stress wave approaching a fixed

-154-



I

\ / /

\

LL

Figure A.3 Transmitted and Reflected Waves Generated at an Impedance Interface.

-155-



end (total velocity must equal zero) is another special case represented by (Z2) equal to

infinity.

It should be noted that the presence of stress wave reflections in the rod string prior to the

(2L/c) time theoretically invalidates the required assumptions of the FF energy

measurement method. Equation A.3 to A.6 may be used to assess the effect of

impedance interfaces on the measured FF energy.

-156-

APPENDIX B

KIDD2 FIELD PROGRAM TEST RESULTS

-157-


Appendix B Kidd2 Field Program Test Results

Table B-1. Summary of Kidd2 Quasi-Static Penetration Test Data.

Test Hole Depth* m(ft)

C P T U Data Force*, kN (kip) Recovery

(%) Test Hole Depth*

m(ft) 9t bar (ksi) (%)

Rod Measured Predicted Recovery

(%)

SPT9901

13.63 (44.7)

76 (1.10) 0.37 1.29

(0.29) 9.34 (2.1)

9.79 (2.2) 92

SPT9901 16.61 (54.5)

119 (1.73) 0.32 1.56

(0.35) 19.1 (4.3)

15.13 (3.4) 94 SPT9901

18.08 (59.3)

156 (2.27) 0.37 1.69

(0.38) 17.4 (3.9)

20.47 (4.6) 89

LPT9902

5.94 (19.5)

25 (0.36) 0.20 0.67

(0.15) 10.7 (2.4)

4.89 (1.1)

79

LPT9902

9.00 (29.5)

82 (1.19) 0.37 0.89

(0.20) 17.4 (3.9)

17.35 (3.9) 29

LPT9902 12.04 (39.5)

113 (1.63) 0.29 1.16

(0.26) 34.7 (7.8)

22.69 (5.1)

67 LPT9902

15.15 (49.7)

96 (139) 0.39 1.42

(0.32) 30.3 (6.8)

20.91 (4.7) 75

LPT9902

18.11 (59.4)

152 (2.21) 0.37 1.69

(0.38) 43.6 (9.8)

32.48 (7.3) 54

LPT9903

14.36 (47.1)

73 (1.06) 0.39 1.29

(0.29) 23.1 (5.2)

15.57 (3.5) 63

LPT9903 16.65 (54.6)

110 (1.60) 0.33 1.56

(0.35) 34.7 (7.8)

22.69 (5.1) 58 LPT9903

18.08 (59.3)

156 (2.27) 0.37 1.69

(0.38) 46.3

(10.4) 33.37 (7.5) 60

SPT9904

7.47 (24.5)

53 (0.77) 0.41 0.76

(0.17) 15.1 (3.4)

7.12 (1.6)

0

SPT9904 11.31 (37.1)

82 (1.18) 0.25 1.16

(0.26) 14.7 (3.3)

9.79 (2.2) 83 SPT9904

18.14 (59.5)

146 (2.11)

0.37 1.69 (0.38)

20.9 (4.7)

19.13 (4.3) 89

* Tip dept h and force at 305 mm (' ft) sampler penetration. Average R f measured over one foot interval above tip depth.

-158-



Table B-2. HPA Data Collected During SPT at Kidd2.

Test Hole

Starting Test Depth,

m(ft)

Number of

Peak Velocity, m/s (ft/s) Velocity Energy Ratio (%) * Test Hole


m(ft) Blows Average Std. Dev. Average Std. Dev. 14.02 (46) 23 3.07

(10.1) 0.11 (0.4) 63.0 4.6

9901

15.54 (51) 28 3.03

(10.0) 0.11 (0.3) 61.6 4.3

9901 17.07 (56) 30 3.10

(10.2) 0.09 (0.3) 64.4 3.7

18.59 (61) 40 3.06

(10.0) 0.09 (0.3) 62.5 3.5

4.88 (16) 16 3.12

(10.2) 0.08 (0.3) 65.1 3.6

7.92 (26) 15 3.19

(10.5) 0.05 (0.2) 68.1 2.4

9.51 (31.2) 30 3.16

• (10.4) 0.03 (0.1) 66.9 2.1

9904 12.50 (41) 25 3.21

(10.5) 0.06 (0.2) 68.9 2.7

15.54 (51) 26 3.19

(10.5) 0.04 (0.1) 67.8 1.7

17.07 (56) 31 3.16

(10.4) 0.03 (0.1) 66.8 0.0

18.59 (61) 46 3.19

(10.5) | 0.05 (0.2) 68.1 2.7

SPT energy quoted as percent of maximum standard SPT energy 473 J (350 ft-lb).

-159-



Table B-3. HPA Data Collected During NALPT at Kidd2

Test Starting Test Depth,

m(ff)

Number of

Blows

Peak Velocity, m/s (ft/s) Velocity Energy Ratio (%) * Hole


m(ff)

Number of

Blows Average Std. Dev. Average Std. Dev. 4.11

(13.5) 8 3.34 (10.9)

0.12 (0.4) 74.5 5.0

4.88 (16) 16 3.28

(10.8) 0.10 (0.3) 72.1 4.3

6.40 (21) 16 3.40

(11.2) 0.06 (0.2) 77.5 2.9

7.92 (26) 19 3.41

( 1 1 . 2 ) 0.00 (0.0) 77.9 0.0

9.45 (31)

27 3.53 ( 1 1 . 6 )

0.07 (0.2) 83.4 3.2

9902 10.97 (36) 21 3.44

(11.3) 0.05 (0.2) 79.0 2.3

12.50 (41) 23 3.43

(11.3) 0.05 (0.2) 78.8 2.1

14.02 (46) 22 3.47

(11.4) 0.08 (0.2) 80.4 3.5

15.54 (51) 23 3.41

( 1 1 . 2 ) 0.00 (0.0) 77.9 0.0

17.07 (56) 31 3.40

(11.1) 0.06 (0.2) 77.1 2.6

18.59 (61) 37 3.38

(11.1) 0.06 (0.2) 76.6 2.8

4.88 (16) 10 3.40

(11.2) 0.04 (0.1) 77.3 1.8

6.40 (21) 14 3.43

(11.3) 0.07 (0.2) 78.9 3.3

7.92 (26) 20 3.43

(11.3) 0.07 (0.2) 78.7 3.1

9903

9.51 (31.2) 34 3.41

(11.2) 0.02 (0.1) 77.7 1.0

9903 11.03 (36.2) 21 3.42

(11.2) 0.03 (0.1) 78.3 1.5

12.47 (40.9) 22 3.45

(11.3) 0.09 (0.3) 79.7 4.4

15.58 (51.1)

22 3.45 (11.3)

0.06 (0.2) 79.6 2.7

18.56 (60.9) 24 3.50

(11.5) 0.07 (0.2) 81.8 3.3

NALPT energy quoted as percent of maximum Kidd2 NALPT energy 1108 J (820 ft-lb)

-160-



Table B-4. Summary of SPT Blow Counts and Energy Ratios Recorded at Kidd2.

Test Hole

Starting Depth, m(ft)

N E R vf

F F Method F V Method Test Hole


N E R vf

E R r * T K i K 2 N 6 0 * E R rf N 6 0

9901

3.35 (11)

2 N . A . N . A . N . A .

9901

4.88 (16) 6 N . A .

50.9 (34.4) 1.03 1.03 5

(4) 47.2 5

9901

6.40 (21)

7 N . A . 52.0

(35.1) 1.02 1.02 6 (4) 59.2 7

9901

7.92 (26) 13 N . A .

52.2 (35.3) 1.01 1.01 12

(8) 51.2 11

9901

9.45 (31)

33 N . A . 56.5

(38.2) 1.0 1.0 31 (21) 53.6 29

9901 10.97 (36) 22 N . A .

57.9 (39.1) 1.0 1.0 21

(14) 55.4 20 9901

12.47 (40.9) 27 N . A .

54.0 (36.5) 1.0 1.0 24

(16) 52.2 23

9901

14.02 (46) 19 63 56.8

(38.4) 1.0 1.0 18 (12) 51.4 16

15.54 (51) 21 62 58.9

(39.8) 1.0 1.0 21 (14) 51.3 18

17.01 (55.8) 22 65 62.6

(42.3) 1.0 1.0 23 (16) 58.8 22

18.53 (60.8) 30 62 61.8

(41.8) 1.0 1.0 31 (21) 54.7 27

9904

4.97 (16.3) 12 65 51.1

(34.5) 1.03 1.03 11 (7) 52.7 11

9904

7.92 (26) 12 68 61.2

(41.4) 1.01 1.01 12 (8) 55.8 11

9904

9.51 (31.2) 24 67 61.1

(413) 1.0 1.0 24 (17) 58.5 23

9904 12.50 (41) 19 68 63.3

(42.8) 1.0 1.0 20 (14) 63.6 20

9904 14.05 (46.1) 13 N . A .

67.5 (45.6) 1.0 1.0 15

(10) 67.7 15 9904

15.54 (51) 21 68 63.9

(43.2) 1.0 1.0 22 (15) 57 20

17.01 (55.8) 24 67 66.6

(45.0) 1.0 1.0 27 (18) 61.8 25

18.38 (60.3) 36 68 78.7 1.0 1.0 47 j 59 35

N.A. Not Available K i and K 2 factors applied to F F energy corrected blow counts but not to F F energy ratios. Non-bracketed values calculated using "AWJ" rod area 4.84 cm 2 (0.75 in2), bracketed values calculated using area of "AW" transducer rod area 7.16 cm 2 (1.11 in2). "NWJ" rod area 9.16 cm 2 (1.42 in2) used for calculations at 18.38 m (60.3') in SPT9904. SPT energy quoted as percent of standard maximum SPT energy 473 J (350 ft-lb).

-161 -



Table B-5. Summary of NALPT Blow Counts and Energy Ratios Recorded at Kidd2.

Test Hole

Starting ER V

F

FF Method FV Method Test Hole Depth,

m(ft) N ER V

F

ER R * T Ki K 2 N 6 o* E R ; N 6 0

4.11 (13.5) 3 74 83.7 1.06 1.11 - 57.1 3 6.40 (21) 6 78 107.1 1.02 1.03 - 66.8 6 7.86

(25.8) 9 78 101.1 1.0 1.02 - 69.1 10 9.51

(31.2) 15 84 110.5 1.0 1.01 - 72.1 17

9902

11.03 (36.2) 11 79 106.3 1.0 1.0 - 63.4 12

9902 12.50 (41) 11 79 112.1 1.0 1.0 - 81.6 13

14.11 (46.3) 11 81 110.9 1.0 1.0 - 74.5 12

15.61 (51.2) 12 78 119.4 1.0 1.0 - 72.7 14

17.01 (55.8) 16 77 114.6 1.0 1.0 - 66.2 20 18.65 (61.2) 20 77 114.3 1.0 1.0 - 79.8 25 4.94

(16.2) 5 78 113.5 1.03 1.03 - 52.5 4 6.40 (21) 7 79 101.5 1.02 1.02 - 60.3 7 7.96

(26.1) 11 79 96.0 1.01 1.01 - 66.5 12

9903

9.51 (31.2) 16 78 115.4 1.0 1.00 - 68.6 18

9903 11.03 (36.2) 12 78 136.4 1.0 1.0 - 67.7 14

12.47 (40.9) 10 79 114.0 1.0 1.0 - 72.6 12

15.58 (51.1) 11 79 116.7 1.0 1.0 - 63.1 12

18.56 (60.9) 12 82 116.5 1.0 1.0 - 70.0 14

«! and K 2 factors applied to FF energy corrected blow counts but not to FF energy ratios. "NWJ" rod area 9.16 cm 2 (1.42 in2) used for calculation. NALPT energy quoted as percent of maximum Kidd2 NALPT energy 1108 J (820 ft-lb).

-162-

APPENDIX C SEWARD, ALASKA FIELD PROGRAM TEST RESULTS

-163-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Appendix C Split Spoon Penetration Testing in Gravels Seward, Alaska Field Program Test Results

Table C-1. Summary of Seward, Alaska Grain Size Analysis Results.

Test Depth * m(ft)

SEWA9802 (SPT) SEWA9803 (NALPT) SEWA9806 (NALPT) Test Depth * m(ft) u s e

% Gravel f

D 5 0 , mm u s e %

Gravel f D 5 0, mm u s e %

Graved D 5 0, mm

4.3 (14.1)

GP 58 8.0 GM 49 4.4 GW 66 11.0 5.8

(19.0) GW-GM 53 5.5 GP-GM 47 3.9 GW 61 7.6 7.3

(24.0) SM 17 0.2 SP-SM 29 0.9 N.A. 9.0

(29.5) N.A. GP-GM 53 5.4 SM 0 0.2 10.4

(34.1) SW-SM 36 2.0 GW-GM 58 7.8 GP-GM 49 4.4 11.9

(39.0) SW-SM 43 3.3 GW-GM 55 6.4 GW-GM 60 8.8 13.5

(44.3) GP-GM 49 4.4 N.A. GM 47 3.4 15.0

(49.2) SM 15 0.1 SP-SM 30 2.8 ML 1 -16.5

(54.1) SP-SM 39 2.4 SP-SM 37 2.4 SM 37 1.7 18.0

(59.1) SW-SM 43 3.3 GW-GM 49 4.5 GM 50 4.8 19.6

(64.3) SW-SM 35 2.0 SP-SM 41 2.8 SW-SM 41 3.0 21.1

(69.2) SM 12 0.6 SM 12 0.5 SM 14 0.5 22.6

(74.1) N.A. N.A. SM 15 0.3 24.1

(79.1) SM 7 0.5 SM 5 0.4 SW-SM 10. 0.5 N.A. Not Available

Exact test depth varies between test holes. Unified Soil Classification (USC) Gravel / Sand Boundary = #4 Sieve (4.75 mm).

-164-

M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Appendix C Split Spoon Penetration Testing in Gravels Seward, Alaska Field Program Test Results

Table C-2. HPA Data Collected During Seward Program.

Test Hole Drop Height cm (in.)

Test Depth m(ft)

Peak Hammer Velocity of Single Hammer Drop,

m/s (ft/s) Velocity Energy

Ratio (%) *

2.68 (8.8) 48

13.5 (44.13)

2.80 (9.2) 53

SEWA9802 76.2 2.93 (9.6) 57

(SPT) (30) 2.56 (8.4) 44

15.0 (49.18)

2.68 (8.8) 48 2.80 (9.2) 53 3.17

(10.4) 59 16.5

(54.12) 3.29

(10.8) 64

3.17 (10.4) 59

SEWA9803 (NALPT)

86.4 (34)

3.17 (10.4) 59

SEWA9803 (NALPT)

86.4 (34)

18.0 (59.19)

3.17 (10.4) 59 3.04 (10) 55 3.17

(10.4) 59 19.6

(64.35) 3.17

(10.4) 59

3.17 (10.4) 59

SPT energy quoted as percent of standard maximum SPT energy 473 J (350 ft-lb), NALPT energy quoted as percent of maximum Seward NALPT energy 1126 J (833 ft-lb).

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M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Appendix C Split Spoon Penetration Testing in Gravels Seward, Alaska Field Program Test ResuIts

Table C-3. Summary of SPT Blow Counts and Energy Ratios Recorded in SEWA9802. Starting Depth, m(ft)

N F F Method F V Method Starting

Depth, m(ft)

N E R r * f Ki K 2 N 6 0 * E R / N 6 0

4.3 (14.2) 30 38.8

(41.9) 1.04 1.08 22 (24) 39.4 20

5.8 (19.0) 32 43.7

(47.2) 1.03 1.04 25 (27) N.A.

7.3 (23.9) 10 42.1

(45.5) 1.01 1.02 7 (8) 45.5 8

9.1 (29.9) 23 46.0

(49.7) 1.01 1.01 18 (19)

52.1 20 10.3

(33.9) 61 46.9 (50.7) 1.00 1.00 48

(52) 51.4 52 11.9

(39.0) 54 40.7 (44) 1.00 1.00 37

(40) 44.5 40 13.4

(44.1) 33 41.8 (45.2) 1.00 1.00 23

(25) 46.7 26 15.0

(49.2) 25 43.6 (47.1) 1.00 1.00 18

(19) 46.4 19

16.5 (54.0) 53 39.6

(42.8) 1.00 1.00 35 (38) 41.7 37

18.1 (59.3) 99 45.0

(48.6) 1.00 1.00 74 (80) 48.8 81

19.5 (64.0) 52 N.A. N.A.

21.1 (69.2) 61 46.9

(50.7) 1.00 1.00 48 (52) 48.9 50

22.6 (74.1) 40 46.2

(49.9) 1.00 1.00 31 (34) 48.3 32

24.1 (79.2) 43 43.9

(47.5) 1.00 1.00 31 (34) N.A.

N.A. Not Available * HM and K 2 factors applied to F F energy corrected blow counts but not to F F energy ratios.

Non-bracketed values calculated using "A" rod area 7.74 cm 2 (1.2 in2), bracketed values calculated using area of "AW" transducer rod 7.16 cm 2 (1.11 in2).

+ SPT energy quoted as percent of standard maximum SPT energy 473 J (350 ft-lb).

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Appendix C Seward, Alaska Field Program Test Results

Table C-4. Summary of NALPT Blow Counts and Energy Ratios Recorded in SEWA9803. Starting Depth, m(ft)

N FF l\ /lethod FV Method Starting

Depth, m(ft)

N ER r * f

Ki K2 N 6 0 * E R / N 6 0

4.4 (14.3)

30 46.1 (63.2) 1.05 1.06 26

(35) 54.1 27 5.9

(19.3) 14 N.A. N A.

7.4 (24.3)

20 52.7 (72.2) 1.02 1.02 18

(25) 56.2 19 8.9

(29.3) 29 55.0 (75.3) 1.01 1.01 27

(37) 54.2 26 10.5

(34.3) 38 55.4

(75.9) 1.00 1.00 35 (48) 52.6 33

11.9 (39.2)

50 65.5 (89.7) 1.00 1.00 55

(75) 61.4 51 13.5

(44.2) 32 59.1

(80.9) 1.00 1.00 32 (43) 54.8 29

15.0 (49.2) 11 63.1

(86.4) 1.00 1.00 12 (16) 57.8 11

16.5 (54.1)

23 64.1 (87.8) 1.00 1.00 25

(34) 59.7 23 18.0

(59.2) 44 69.2

(94.7) 1.00 1.00 51 (69) N. A.

19.6 (64.3) 31 64.5

(88.3) 1.00 1.00 33 (46) 59.1 31

21.1 (69.3) 32 65.6

(89.9) 1.00 1.00 35 (48) 59.1 32

22.6 (74.3)

30 64.6 (88.5) 1.00 1.00 32

(44) 58.1 29 24.0

(78.9) 26 67.5 (92.5) 1.00 1.00 29

(40) 61.2 27 N.A. Not Available '

K, and K2 factors applied to FF energy corrected blow counts but not to FF energy ratios Non-bracketed values calculated using "NWJ" rod area 9.81 cm 2 (1.52 in2), bracketed values calculated using area of "AW" transducer rod 7.16 cm 2 (1.11 in2). NALPT energy quoted as percent of maximum Seward NALPT energy 1126 J (833 ft-lb).

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APPENDIX D

KEENLEYSIDE DAM FIELD PROGRAM TEST RESULTS

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M.A.Sc. Thesis, Chris R. Daniel The University of British Columbia Appendix D Split Spoon Penetration Testing in Gravels Keenleyside Dam Field Program Test Results

Table D-1. HPA Data Collected in DH99-20 During NALPT at Keenleyside Dam. Starting Test

Depth m(ft)

Number of Blows

Peak Velocity, m/s (ft/s) Velocity Energy Ratio (%) * Starting Test Depth m(ft)

Number of Blows Average Std. Dev. Average Std. Dev.

7.13 (23.4) 36 10.2 0.6 64.3 7.5

8.93 (29.3) 21 10.1 0.6 63.9 7.9

10.30 (33.8) 45 10.5 0.7 68.5 9.0

11.83 (38.8) 22 10.8 0.5 72.2 7.3

13.38 (43.9) 38 10.7 0.5 71.5 6.2

14.9 (48.9) 28 11.1 0.5 76.5 7.2

17.95 (58.9) 48 10.8 0.5 73.2 6.3

20.97 (68.8) 96 10.6 0.7 70.6 8.8

N.A. - Not Available NALPT energy quoted as percent of maximum Keenleyside NALPT energy 1108 J (820 ft-lb).

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Table D-2. Summary of NALPT Blow Counts and Energy Ratios Recorded in DH99-20. Starting Depth, m(ft)

N FF Method FV Method


N ERR* F Ki K 2 N 6 0 * E R ; N 6 0

2.99 (9.8) 19 32.8

(42.0) 1.38 1.09 16 (20) 62.4 20

4.42 (14.5) 18 33.5

(42.9) 1.16 1.05 12 (15) 64.2 19

5.61 (18.4) 12 31.0

(39.7) 1.08 1.03 7 (22) 56.5 11

7.13 (23.4) 21 N.A.

8.93 (29.3) 8 39.8

(50.9) 1.02 1.01 5 (6) 59.9 8

10.30 (33.8) 20 45.9

(58.8) 1.01 1.00 15 (19) 63.2 21

11.83 (38.8) 16 50.2

(64.3) 1.00 1.00 13 (17) 71.7 19

13.38 (43.9) 26 50.9

(65.1) 1.00 1.00 22 (28) 73.5 32

14.9 (48.9) 9 60.1

(76.9) 1.00 1.00 9 (12) 80.7 12

17.95 (58.9) 24 59.0

(75.5) 1.00 1.00 24 (31) 77.7 31

20.97 (68.8) 45 69.1

(88.3) 1.00 1.00 52 (67) 97.5 73

N.A. Not Available Ki and K 2 factors applied to FF energy corrected blow counts but not to FF energy ratios. Non-bracketed values calculated using "NW" rod area 9.16 cm 2 (1.42 in2), bracketed values calculated using area of "AW" transducer rod 7.16 cm 2 (1.11 in2). NALPT energy quoted as percent of maximum Keenleyside NALPT energy 1108 J (820 ft-lb).

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Table D-3. Keenleyside Dam Comparison Data Set. DH91-3c(BPT) DH91-3d (SPT) DH99-20 (NALPT)

Depth m(ft)

Equivalent (N 6 0 ) S PT Depth m(ft) (N6Cj)sPT Depth

m(ft)

(N6O)NALPT Depth m(ft) Harder

and Seed Sy and

Campanella

Depth m(ft) (N6Cj)sPT Depth

m(ft) F2 Method *

FV Method

3.0 (10) 8 16 3.1

(10) 23 2.99 (9.8)

16 (20) 20

4.6 (15) 8 13 4.6

(15) 30 4.42 (14.5)

12 (15) 19

5.8 (19) 6 6 6.1

(20) 17 5.61 (18.4)

7 (22) 11

9.1 (30) 6 4 9.0

(29.5) 5 8.93 (29.3)

5 (6)

8

10.4 (34) 8 8 10.7

(35) 15 10.30 (33.8)

15 (19) 21

11.9 (39) 12 15 12.2

(40) 33 11.83 (38.8)

13 (17) 19

13.4 (44) 8 6 13.7

(45) 31 13.38 (43.9)

22 (28) 32

14.9 (49) 13 14 15.2

(50) 23 14.9 (48.9)

9 (12) 12

18.0 (59) 18 24 18.3

(60) 20 17.95 (58.9)

24 (31) 31

21.0 (69) 17 19 21.5

(70.5) 70 20.97 (68.8)

52 (67) 73

Non-bracketed values calculated using "NW" rod area 9.16 cm* (1.42 in*), bracketed values calculated using area of "AW" transducer rod 7.16 cm 2 (1.11 in2).

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SPLIT SPOON PENETRATION TESTING IN GRAVELS …