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1. MEYERHOF METHOD
POINT BEARING CAPACITY, QP
Rules…. Of Meyerhof
1st Example… Meyerhof
2nd Example
Please remember Meyerhof design procedure…
2. VESIC METHOD
3. COYLE & CASTELLO METHOD
Example
Example 2
FRICTIONAL RESISTANCE, QS
CASE 1: SAND
Critical Depth : 15 D
d Roughly about 0.5 to 0.8
Meyerhof:
Average unit frictional resistance for high displacement piles:
Average unit frictional resistance for low displacement piles:
4. LAMDA METHODCASE 2: CLAY
5. ALPHA METHOD
CASE 2: CLAY
6. BETA METHOD
Normally Consolidated Over Consolidated
CASE 2: CLAY
• Types of foundation, dimension, length, allowable and ultimate bearing capacity will be decided by IKRAM
• most of the time the ‘SPT’ value used to define the bearing capacity
• For the government, the concrete and spun pile are most preferred
• for private project: bakau pile, micropile, concrete, spunpile, borepile etc.
JKR RECOMMENDATIONS:
Example:
SI Report and Foundation Recommendation
Project title
Client
Proposed Types of Foundation
Bearing capacity calculation
Detail properties of pile/situation
Recommendations
Recommendations
Pile Load Test
Recommendations
SPT
vs
Depth
Project Title
Client
Building desc.
Max. load
Min. load
No. borehole
Pile size
Proposed S.F
Bearing capacity calculation (Meyerhof consideration)
Qa
PILE LAYOUT
SI REPORT :CASE STUDY 1
SI REPORT :CASE STUDY 2
SI REPORT :CASE STUDY 3
i) Determined the average value of N over the depth
ii) Determined the skin friction, Qs
iii) Determined the end bearing, Qb
iv) Calculate ultimate bearing capacity
v) Allowable bearing capacity, Qa
Qs = k1.Nav.As
Qb = k2.N.Ab
Qult = Qs + Qb
Qa= SQs/2 +Qb/3
PILE DESIGN BASED ON MODIFIED MEYERHOF METHOD
Type Of Soil Skin Friction Qs (k1) End Bearing Qb (k2)
Clay α . Cu . As (kN) 100 . N . Ab (kN)
Silt 1.7 . N . As (kN) 250 . N . Ab (kN)
Sand 2.0 . N . As (kN) 400 . N . Ab (kN)
Rock SPT = 50 400 . N . Ab (kN)
Ultimate Bearing Capacity Based On Type Of Soil (Modified Meyerhof)** Commonly used by JKR
Pile Capacity Design Factor of Safety (FOS)
Partial factors of safety for shaft & base capacities respectively
For shaft, use 1.5 (typical)
For base, use 3.0 (typical)
SQsu + Qbu
1.5 3.0Qall =
Pile Capacity Design Factor of Safety (FOS)
Global factor of safety for total ultimate capacity
Use 2.0 (typical)
SQsu + Qbu
2.0Qall =
Pile Capacity Design Factor of Safety (FOS)
Calculate using BOTH approaches (Partial & Global)
Choose the lower of the Qall values
Qu = Qs + Qb
Overburden Soil Layer
Qs = skin friction
Qb = end bearing
Qu = ultimate bearing capacity
Pile Capacity Design Single Pile Capacity
Qu = a.cs.As + cb.Nc.Ab
Qsu Qbu
Qu = Ultimate bearing capacity of the pile
a = adhesion factor (see next slide)
cs = average undrained shear strength for shaft
As = surface area of shaft
cb = undrained shear strength at pile base
Nc = bearing capacity factor (taken as 9.0)
Ab = cross sectional area of pile base
Pile Capacity Design Single Pile Capacity : In Cohesive Soil
Pile Capacity DesignSingle Pile Capacity: In Cohesive Soil
Adhesion factor () – Shear strength (Su) (McClelland, 1974)
Adhesion Factor
Su (kN/m2)25 75 100 125 150 17550
0
0.6
0.2
0.4
0.8
1.0
Ca/Su
Preferred Design Line
Meyerhof Fukuoka
SPT Nfsu=2.5N
(kPa)
su = (0.1+0.15N)*50
(kPa)a fsu= .a su
(kPa)
0 0 5 1 5
1 2.5 12.5 1 12.5
5 12.5 42.5 0.7 29.75
10 25 80 0.52 41.6
15 37.5 117.5 0.4 47
20 50 155 0.33 51.15
30 75 230 0.3 69
40 100 305 0.3 91.5
Correlation Between SPT N and fsu
fsu vs SPT N
0
10
20
30
40
50
60
70
80
90
100
110
0 5 10 15 20 25 30 35 40 45
SPT N
fsu
(kP
a)
Meyerhof Fukuoka
Pile Capacity DesignSingle Pile Capacity: In Cohesive Soil
• Values of undrained shear strength, su can be obtained from the following: Unconfined compressive test
Field vane shear test
Deduce based on Fukuoka’s Plot (minimum su )
Deduce from SPT-N values based on Meyerhof
Pile Capacity DesignSingle Pile Capacity: In Cohesive Soil
NOTE: Use only direct field data for shaft friction prediction instead of Meyerhof
Modified Meyerhof (1976):
Ult. Shaft friction = Qsu 2.5N (kPa)
Ult. Toe capacity = Qbu 250N (kPa)
or 9 su (kPa)
(Beware of base cleaning for bored piles – ignore
base capacity if doubtful)
Pile Capacity DesignSingle Pile Capacity: In Cohesive Soil
Modified Meyerhof (1976):
Ult. Shaft Friction = Qsu 2.0N (kPa)
Ult. Toe Capacity= Qbu 250N – 400N (kPa)
Pile Capacity DesignSingle Pile Capacity: In Cohesionless
Soil
Load (kN)
Pile Capacity Design
50
40
30
20
10
0
0 100 200 300 400
SQsu + QbuQbu
SQsu + Qbu
1.5 3.0
SQsu + Qbu
2.0
SQsu
De
pth
(m
)
2.2 ANALYSIS AND DESIGN OF PILE UNDER LATERAL STATIC LOADS
Piles behaviour…
STEPS OF CALCULATION: BRINCH & HANSEN
Ultimate soil resistance
BROM’S METHOD
SOIL TYPE : SANDY / COHESIONLESS
SHORT PILE LONG PILE
SOIL TYPE : COHESIVE
SHORT PILE LONG PILE
FR
EE
HE
AD
FIX
HE
AD
C SOIL SOIL
ULTIMATE LATERAL LOAD CAPACITY BY BROM’S
ULTIMATE LATERAL LOAD CAPACITY BY BROM’S
LONG PILE
PILE DRIVING FORMULA
Courtesy: Transportation Curriculum Coordination Council, U.S
Pile Driving System
Hammers
Steam Hammer
Open End Diesel
Closed End Diesel
Hydraulic HammersVibratory Hammers
Jack-In
Cushions
Hammer cushion set in pile cap
different types of cushions
Typical plywood pile cushion
PILE LOAD TEST
Slow Maintain Pile Load Test
PILE LOAD TEST
FAILURE ??
• when pile settlement occur rapidly
• when the pile head has moved 10% of pile tip diameter
• gross settlement of 38mm for 2X design load
• residual settlement of less than 6.5mm
INTERPRETATION OF TEST DATA
NEGATIVE SKIN FRICTION
CASE 1
CASE 2
CASE 3
2.4. PULLOUT RESISTANCE OF PILES
CASE 1: CLAYEY SITE
CASE 2: SAND
Determination of net uplift capacity….
2.5. BEARING CAPACITY OF PILES RESTING ON ROCK
2.5
FS ≥ 3
Scale effect cause of rock fractured
( 4 ≤ S.E ≤ 5 )
2.5
2.6. BEARING CAPACITY OF GROUP PILES
2.6
• most cases, piles used in groups
• pile cap is constructed over group of piles
• when piles placed close to each other, stresses transmitted will overlap >>> reduce the load-bearing capacity of pile
• practice, center-to-center pile spacing, d = minimum 2.5D
• in ordinary situations, 3D ≤ d ≤ 3.5D
• consider group efficiency
2.6
CASE 1: Group of Piles in Sand
If > 1 (piles spacing are large), piles will behave as individual piles, thus in
practice make sure < 1
Alternative solution…
2.6
General Conclusions….
2.6
CASE 2: Group of Piles in Clay
Steps of design:
2.6
CASE 3: Group of Piles in Rock
Minimum center-to-center spacing = D + 300mm
2.6
2.6
2.6
2.6
2.7. ELASTIC SETTLEMENT OF PILES
2.8. ELASTIC SETTLEMENT OF GROUP PILESGENERAL CASES
SAND & GRAVEL CASES
Load
Time
Components of settlement
Constructiontime
Load
Time
Components of settlement
Constructiontime
Settlement
Time
Initialsettlement si
Const.time
Load
Time
Components of settlement
Constructiontime
Settlement
Time
Consolidationsettlement sc
Initialsettlement si
Total finalsettlement sTf
Const.time
2.8. CONSOLIDATION SETTLEMENT OF GROUP PILES
PROCEDURE
ACKNOWLEDGEMENT….
Apart of this presentation are from my former students efforts, Sem. 1 2003/04 until now… I’m thank you for their support and works!
Other References,• B.M., Das : Principles of Foundation Engineering• Liu Evett : Soils and Foundations• Coduto: Foundation Design• Dunn, Anderson, Kiefer: Fundamentals of
Geotechnical Analysis • Monash University, Australia• Ir Mohamed bin Daud, JKR, Kelantan
