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

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 = Qs = k1.Nav.As.Nav.As

Qb = Qb = k2.N.Ab.N.Ab

Qult = Qs + QbQult = Qs + Qb

Qa= SQs/2 +Qb/3

PILE DESIGN BASED ON MODIFIED PILE DESIGN BASED ON MODIFIED MEYERHOF METHODMEYERHOF 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 Pile Capacity Design Factor of Safety (FOS)Factor of Safety (FOS)

PartialPartial factors of safety for shaft & base factors of safety for shaft & base capacities respectivelycapacities respectively

For shaft, use 1.5 (typical)For shaft, use 1.5 (typical)

For base, use 3.0 (typical)For base, use 3.0 (typical)

Qsu + Qbu

1.5 3.0Qall =

Pile Capacity Design Pile Capacity Design Factor of Safety (FOS)Factor of Safety (FOS)

GlobalGlobal factor of safety for total ultimate factor of safety for total ultimate capacitycapacity

Use 2.0 (typical)Use 2.0 (typical)

Qsu + Qbu

2.0Qall =

Pile Capacity Design Pile Capacity Design Factor of Safety (FOS)Factor of Safety (FOS)

Calculate using Calculate using BOTHBOTH approaches approaches (Partial & Global)(Partial & Global)

Choose the Choose the lower lower of the Qof the Qallall values values

QQuu = Q = Qss + Q + Qbb

Overburden Soil Layer

Qs = skin friction

Qb = end bearing

Qu = ultimate bearing capacity

Pile Capacity Design Pile Capacity Design Single Pile CapacitySingle Pile Capacity

Qu = .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 Pile Capacity Design Single Pile Capacity : In Cohesive Soil Single Pile Capacity : In Cohesive Soil

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn Cohesive Soil

Adhesion factor (Adhesion factor () – Shear strength (S) – Shear strength (Suu) )

(McClelland, 1974)(McClelland, 1974)

Adhesion Factor

Su (kN/m2)25 75 100 125 150 17550

0

0.6

0.2

0.4

0.8

1.0

C/Su

Preferred Design Line

Meyerhof Fukuoka

SPT Nfsu=2.5N

(kPa)

su =

(0.1+0.15N)*50(kPa)

fsu=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 fCorrelation Between SPT N and fsusu

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 DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn 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 DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn 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 DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesive SoilIn Cohesive Soil

Modified Meyerhof (1976):Modified Meyerhof (1976):

Ult. Shaft Friction = QUlt. Shaft Friction = Qsusu 2.0N (kPa) 2.0N (kPa)

Ult. Toe Capacity= QUlt. Toe Capacity= Qbubu 250N – 400N (kPa) 250N – 400N (kPa)

Pile Capacity DesignPile Capacity DesignSingle Pile Capacity:Single Pile Capacity: In Cohesionless In Cohesionless

SoilSoil

Load (kN)

Pile Capacity Design

50

40

30

20

10

0

0 100 200 300 400

Qsu + QbuQbu

Qsu + Qbu

1.5 3.0

Qsu + Qbu

2.0

Qsu

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

Terima KasihTerima KasihNor Azizi YusoffNor Azizi Yusoff

azizy@uthm.edu.myazizy@uthm.edu.my019-7779469019-7779469