Ground types SIN - srmeg.org.sg Ground Types are ground (rock masses) ... Ground types TBM segmental lining Short Course Singapore 11 Klima, Schubert 22 Ground types Discontinuity

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DETERMINATION OF GROUND PROPERTIES

and

DEFINITION OF GROUND TYPES

2Short Course Singapore 11 Klima, Schubert

Ground types

OBJECTIVES

■ Physical and geometrical parameters of the ground are required for various purposes:

□ Assessment of potential failure modes□ Estimation of stresses and displacements□ Evaluation of required support□ Selection of excavation method□ Estimation of water inflow□ Estimation of tool wear and progress rate□ etc.

Necessary for any analytical or numerical design approach.

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Ground types

STRATEGY

■ Get overview on the geological/geotechnical conditions of the project

■ Distinguish engineering-geological units, with emphasis on lithological and structural characteristics

■ Describe the characteristics of each unit and make a sketch of a representative volume, preferably in 3D

■ Identify characteristic features of each unit, eg intact rock strength, anisotropy, shear strength of discontinuities, etc.

■ Determine the degree of acceptable simplification; a simplified model should still allow capturing characteristic behaviours

■ Split units into Ground Types, if variation of properties is large; determine relevant parameters for each GT


Ground types

Determination of properties

■ Which properties do we need?

■ What do we use them for?

■ Whenever possible, try to use direct methods for an estimate of the ground parameters

■ Using empirical methods cannot be completely avoided.

■ When using empirical methods for the determination of parameters check their plausibility

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Ground types

GROUND TYPES

■ Definition: Ground Types are ground (rock masses) with similar properties (of a geotechnically relevant volume)

■ Definition of geotechnically relevant parameters – key parameters

■ Evaluation of the parameter values and ranges

■ Classification into Ground Types

■ Description of Ground Types shall contain

□ Rock/soil type□ Verbal description of composition and condition□ Sketch of representative volume□ Properties of intact rock and discontinuities□ Properties of rock mass (range); in case of anisotropy

properties in different directions


Ground types

Parameter representative value/range

Engineering geological unit

Limestone (limestone, and marble)secondary: dolomite

LithologyGrey and sometimes dark grey limestone with transitions to marble ot to domomite (marble), limestone breccia (cemented)

UCS [MPa] 30 - 80 (50 - 120*)

c [MPa] 8 - 18 (12 - 20*)

45 ± 6

mi [-] 20 ± 6 (15 ± 2*)

Braz. [MPa] 1,4 - 2,9 (range of lab results)

E [GPa] 20 - 60 (40 - 80*)

ν [-] 0,18 ± 0,07 (0,2*)

Abrasivity (low) abrasive CAI [-] 0,9 - 1,8

General descriptionPartially bedded with spacing in a cm range, partially karst along jointsTeilweise with openings of mm to some cm (signs of weathering)

Foliation / bedding, spacing

bedded and thinly laminated; bedding only partially mechanically relevant

foliation spacing

6 - 20 (partially <6 bzw. >20)

φsf [°] 35 - 45

φsf, rest [°] 30 - 40

sizedom.: 2 - 20 cmsec.: 20 - 60 cm

geometry generally blocky

φK,H [°] 35 - 45

φK,H, rest [°] 30 - 40

GSI-classificationJoints and bedding are dominating, blocks show size of cm to some dm, rough discontinuities

GSI [-] 40 - 55

UCSRM [MPa] 14,3 (6,6-25,5)

cRM [MPa] 3,8 (1,9-6,3)

φRM [°] 34,4 (31,1-37,5)

νRM [-]

Elastic properties ERM [GPa] 15,8 (6,4-32,7)

Remarks concerning grouting

Remarks concerning swelling

Dis

co

nti

nu

ity

Foliation / bedding, conditions

Strength propertiesthe rock mass strength is generally dominated by the discontinuities. Isotropic to slightly anisotropic

Joints, block size and goometry

manily narrow jointing and very narrow secondary jointing (incomplete healing); rarely medium jointing

dom.: stepped to planar, rough partially oxidated (karstic joints)sec..: planar /rough to smooth; rarely clayey (sl)

Joints / slickensides, conditions

Interpretation of laboratory results, filed data and core logging

Ground Type 4b Limestone and Marble (Permomesozoic), moderately to heavily fractured

Short descritption Limestone and marble,moderately to heavily fractured

Detailed rock mass description

Inta

ct r

ock

Mechanical propertiesIsotropic to low anisotropic rock with high intact rock strength

Gouting is possible up to a certain level (along joints), locally high grouting volumes possible due to open karst discontinuities

planar to wavy, rough, partially oxidations, partially minor clay fillings

Ad

dit

ion

al

da

ta

no swelling potential

Ro

ck

ma

ss

Representative core photos:

Sketch:

KB 17/07: limestone, bedded, with joints, fractrued, with karst

KB 06/08: Limestone marble, tectonized, fractured

Die dargestellte Gefügeneigung ist beispielhaft. Die tatsächliche Gefügeorientierung zum Bauwerk kann davon stark abweichen.

Remarks:

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Case study:Evaluation of Construction Methods for the Mae Ngad – Mae Kuang Project

Alfred Fasching & Wulf Schubert, 3G

Alois Vigl, viglconsult

Chinda Sutiwanich, Panya


Ground types

The Project

■ The Mae Kuang Dam Inflow Augmentation Project in theChiang Mai province includes a 23.1 km distribution tunnelwith approximately 5 m diameter, connecting the Mae Ngad and Mae Kuang reservoirs.

■ Client: Royal Irrigation Department

■ Feasibility and alignment studies were carried out in theprevious years, including geological investigations. In 2005 the alignment was fixed, and the tender designstarted.

■ Construction start is planned for this year

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Ground types

INTAKE

ADIT #5

ADIT #6

OUTLET

Several alignments were studiedwith emphasis on minimizing risksassociated with tunnelling.

Site installations are possible at theadits 5 and 6, and at the outlet

Adit #5 required during operationfor depletion of tunnel


Ground types

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Ground types

Longitudinal section

quartzitic sandstoneshale and siltstone

intercalations

sheared shalechert and sandstone

limestone blocksquartzitic sandstone with shale intercalations


Ground types

Method of evaluation

■ Rock mass characterization

□ Determination of Rock Mass Types (RMT)□ Assignment of physical parameters to each RMT□ Divide alignment into evaluation sections

■ Evaluation of rock mass behaviour

□ Evaluate response of rock mass to excavation underconsideration of rock mass type, stresses, ground water, tunnel size and orientation for each section

■ Assign construction measures

□ Appropriate excavation and support methods for eachbehaviour type

■ Evaluation of System Behaviour

■ Assignment of time and costs

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Ground types

Distribution of Ground Types

0

1

2

3

4

5

6

7

8

9

0 5.000 10.000 15.000 20.000

station

RM

T

0

500

1000

1500

2000

2500

3000

ove

rbu

rde

n


Ground types

Distribution of Behaviour Types

0

1

2

3

4

5

6

7

8

9

10

11

0

5000

100

00

150

00

200

00

station [m]

Be

ha

vio

ur

Typ

e

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

ove

rbu

rden

, w

ate

rtab

le (

m)

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Ground types

Options studied

ADIT 6ADIT 5

INTAKE OUTLET

D&

B

TBM

D&

B

D&B D&B D&B D&B

OPTION 1

ADIT 6ADIT 5

INTAKE OUTLET

D&

B D&

BTBM D&B TBM

OPTION 2

ADIT 6ADIT 5

INTAKE OUTLETTBM TBM

D&

B

D&B

OPTION 3


Ground types

Tunnelling methods

■ Drill & blast

□ 4 excavation & support classes□ Round lengths from 1,0 to 3,0 m□ Support from spot bolting to full shotcrete lining with bolts

■ TBM

□ Double shield TBM chosen□ Open TBM considered earlier in the project was ruled out due

to the requirement of smooth lining, and the existence of several fault zones

□ Two segment types considered (standard + strong)

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Ground types

D&B tunnel support


Ground types

D&B tunnel support

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Ground types

Typical section adits


Ground types

Support Adits

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Ground types

TBM segmental lining


Ground types

Discontinuity controlled block fall

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Ground types

Finite element model TBM


Ground types

Axial forces

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Ground types

Bending moments


Ground types

Time & cost estimate

■ Advance rates and costs estimated based on:

□ Rock type (strength, abrasivity)□ Rock mass behaviour (assignment of excavation and support types,

TBM performance, etc.)□ Ground water treatment, probing ahead, drainage, grouting etc.,

correlated to ground behaviour□ Special measures & events

□ Machine costs□ Material and labor costs□ Site installation, etc.

■ Uncertainty in rock mass quality was considered by evaluating time and costs for three different rock mass qualities (low, average, high strength)

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Ground types


Ground types

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Ground types


Ground types

Time schedule excavation & supportOPTION 2 m

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000

station (m)

mo

nth

s

0

500

1000

1500

2000

Lining D&B

D&B

TBM

TBM

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Ground types

Time schedule excavation & supportOPTION 3 m

0

10

20

30

40

50

60

0 5000 10000 15000 20000 25000

station (m)

mo

nth

s

0

500

1000

1500

2000

Lining D&B

D&B

TBMTBM


Ground types

Cost Comparison

0%

20%

40%

60%

80%

100%

low RQ average RQ high RQ

Option 1

Option 2

Option 3

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Ground types

Conclusion

■ Systematic geological modelling and rock masscharacterization in combination with a consistentevaluation of rock mass and system behaviour allows to objectively compare different construction methods in terms of feasibility, time and costs.

■ For the Mae Ngad – Mae Kuang project option 1 with thehighest share in labor intensive drill & blast due to relatively low labor costs showed to be economicallyadvantageous. Risk of delays and cost overruns due to multiple headings minimized

Documents

Ground types SIN - srmeg.org.sg Ground Types are ground (rock masses) ... Ground types TBM segmental lining Short Course Singapore 11 Klima, Schubert 22 Ground types Discontinuity