design of pile bearing capacity by insitu testing

Design of Pile Bearing Capacity by In-Situ Testing

Aswin Lim ST., MSc.Eng

Geotechnical Division Civil Engineering Department Faculty of Engineering

Parahyangan Catholic University

1 International Workshop on Pile Foundation

and Pile Dynamics 2012

Outlines

Introduction of CPT and SPT

Driven Pile Capacity

Bored Pile Capacity



In-Situ Geotechnical Tests



Standard Penetration Test (SPT)

Advantages : 1. Simple 2. Obtain sample and number 3. Suitable for many types of soil 4. Can perform in weak rock 5. Widely available

Disadvantages : 1. Sample is disturbed (*Index tests only) 2. Crude number for analysis 3. Not applicable for soft soils 4. High variability and uncertainty

Hammer Weight : 622.72 N Drop distance : 30 inch = 76.2 cm



Standard Penetration Test (SPT)

Nspt = N2+N3

N1 N2 N3



Standar Penetration Test (SPT)

Hammer energy efficiency is ratio between actual hammer energy to input energy. In field, the hammer energy efficiency can vary from 30% to 90%. For standard practice, it use an average energy ratio of 60%.

6060

RSBHNN

Variation of H (hammer efficiency)

Country Hammer type Hammer release H (%)

Japan Donut Free fall 78

Donut Rope and pulley 67

United States Safety Rope and pulley 60


Argentina Donut Rope and pulley 45

China Donut Free fall 60


Variation of B (correction of borehole diameter)

Diameter

mm B

60 - 120 1

150 1,05

200 1,15

Variation of S (Sampler correction)

Variable S

Standard sampler 1

With liner for dense sand and clay 0,8

With liner for loose sand 0,9

Variation of R (correction of rod length)

Rod Length

m R

> 10 1

6 - 10 0,95

4-6 0,85

0-4 0,75




Donut Hammer Safety Hammer




Standard penetration Consistency Unconfined Compression Undrained Shear

number, N60 Strength, qu (KPa) Strength, cu (KPa)

200

Standard penetration Approximate

number, N60 relative density, Dr (%)

0-5 0-5

5-10 5-30

10-30 30-60

30-50 60-95



Bored Pile Capacity Estimation by SPT Testing

Reese and Wright Method (1977)

ppp qAQ .

Note : 1 tsf = 95,76 KPa

SANDY SOILS




Reese and Wright Method (1977)

ss fLpQ ..

SANDY SOILS




Meyerhofs method ( Sand )

ssppu ANANQ ..2,0..40 ...Unit ( ton)

Np = N-SPT value at pile tip Ns = Average N-SPT value along pile




Schmertmanns method ( Clean Sand )






Schmertmanns method ( Cohesive soil)





Cone Penetration Test (CPT) - Sondir

Advantages : 1. Fast and continuous profiling 2. Economical 3. Results not operator dependant 4. Strong theoretical basis in interpretation 5. Particularly suitable for soft soil

Disadvantages : 1. Unsuitable for gravel or boulder deposits 2. No soil sample is obtained




How to measured : 1. Push the rod to advance penetrometer tip ( get the qc)-R1 2. Push the inner rod to extend the tip (get qc + fs )-R2 3. Usually measured in 20 cm range




How to process the data ??

1. qc get directly from the manometer reading 1 (R-1) 2. fs should be calculated based on R-2 and R-1

skin

tip

sA

ARRf 12

Atip = 10 mm2

Askin = 150 mm2

%100c

sf

q

fR Friction ratio



Example Depth Manometer Reading Local Total Friction

(m) Cone Total Friction Friction ratio

(kg/cm2) (kg/cm2) (kg/cm2) (kg/cm) ( % )

0.0

0.2 8 20 0.800 16.01 10.01

0.4 14 30 1.067 37.35 7.62

0.6 19 30 0.734 52.03 3.86

0.8 20 28 0.534 62.70 2.67

1 22 30 0.534 73.37 2.43

1.2 21 30 0.600 85.38 2.86

1.4 30 60 2.001 125.40 6.67

1.6 25 55 2.001 165.42 8.00

1.8 25 65 2.668 218.78 10.67

2 20 55 2.335 265.47 11.67

2.2 15 45 2.001 305.49 13.34

2.4 15 45 2.001 345.51 13.34

2.6 15 45 2.001 385.53 13.34

2.8 15 35 1.334 412.21 8.89

3 15 40 1.668 445.56 11.12

3.2 15 30 1.001 465.57 6.67

3.4 20 45 1.668 498.92 8.34

3.6 10 25 1.001 518.93 10.01

3.8 10 30 1.334 545.61 13.34

4.0 10 15 0.334 552.28 3.34

4.2 5 15 0.667 565.62 13.34

4.4 23 40 1.134 588.29 4.93

4.6 15 40 1.668 621.64 11.12

4.8 10 33 1.534 652.33 15.34

5.0 10 33 1.534 683.01 15.34

5.2 5 10 0.334 689.68 6.67

5.4 5 8 0.200 693.68 4.00

5.6 10 15 0.334 700.35 3.34

5.8 15 25 0.667 713.69 4.45

6.0 15 35 1.334 740.37 8.89

6.2 30 45 1.0005 760.38 3.335

6.4 15 35 1.334 787.06 8.893333

6.6 75 80 0.3335 793.73 0.444667

6.8 55 65 0.667 807.07 1.212727

7.0 115 170 3.6685 880.44 3.19

7.2 135 145 0.667 893.78 0.494074

7.4 250 19

International Workshop on Pile Foundation and Pile Dynamics 2012


0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

0 50 100 150 200 250

D

e

p

t

h

(

m)

qc (kg/cm2)

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

0 1 2 3 4

D

e

p

t

h

(

m)

fs (kg/cm2)

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

0 5 10 15 20

D

e

p

t

h

(

m)

Rf (%)



Soil Profile Interpretation



Driven Pile Capacity Estimation by CPT Testing

Schmertmann-Nottingham Method (1975)

p

cc

p Aqq

Q .2

2,1,

Where : Qp = Pile tip resistance qc,1 = the average value of qc (cone resistance) at 0.7D 4D below pile tip. qc,2 = the average value of qc (cone resistance) until 8D above pile tip Ap = Pile tip area

Note : In general, the value of cone resistance is limited to 100kg/cm2 for sandy soil and 75 kg/cm2 for silty sand

Tip Resistance



Driven Pile Capacity Estimation by CPT Testing

Schmertmann-Nottingham Method (1975)

D

z

L

Dz

sssscss AfAfD

zKQ

8

0 8

, ....8

.

Where : Qs = Skin friction resistance D = Pile diameter or side fs = Skin friction of CPT test As = Skin friction contact area Ks,c = reduction factor based on CPT type, depth, fs, and type of pile material

Note : In general, the value of skin friction is limited to 1.2 kg/cm2 for sandy soil and 1.0 kg/cm2 for silty sand

Skin Friction Resistance



The value of Ks,c

D = pile length, and B = pile side 24 International Workshop on Pile Foundation and Pile Dynamics 2012

International Workshop on Pile Foundation and Pile Dynamics 2012

25

ANY QUESTIONS ????

design of pile bearing capacity by insitu testing

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