INDIAN INSTITUTE OF TECHNOLOGY MADRAS

CIVIL ENGINEERING DEPARTMENT

August – December 2012

CE 3350: GEOTECHNICAL ENGINEERING

PRACTICE PROBLEMS FOR PILE FOUNDATIONS

1. A 15 m long 400 mm square pile is driven into a uniform sand which has a friction

angle of 30. Water table is at a depth of 3 m below the ground level. Saturated and

dry unit weights of the sand are 20 and 17 kN/m3 respectively. Calculate the safe

load carrying capacity of the pile with a factor of safety of 3.

2. A pile with a diameter of 500 mm carries an axial load of 300 kN. The soil is

uniform clay with an unconfined triaxial compression strength of 40 kPa. Design the

length of the pile as a purely frictional pile and when it carries load by both friction

and end bearing. Use a factor of safety of 2.5. The average unconfined strength of

clay at the tip of the pile is 75 kPa. The average N value over the length of the pile is

5. Calculate the length for both bored and driven piles.

3. A group of 9 piles (bored piles), each 200 mm in diameter and 12 m long, is used as

a foundation for a column in a uniform deposit of clay with an undrained cohesive

strength of 30 kPa. The piles are arranged in a square pattern with 3 on each side

with a c/c spacing of 400 mm. Calculate the ultimate load capacity of the group.

Estimate the probable settlement of the pile group for this loading if the thickness of

the clay stratum is 20 m and coefficient of volume compressibility mv is 0.3 m2/MN.

4. It is desired to install a pre-cast driven pile with a safe load carrying capacity of 2000

kN at a site. The following hammers are available for driving. Using Engineering

News Formula, recommend the set values to achieve the safe pile capacity and as the

criteria to stop the pile driving. Comment if the capacity of these hammers is

adequate to achieve the required pile capacity. What is the required set value if the

required pile capacity is only 500 kN?

Type of Hammer Weight Ht. of fall

(kN) (m)

Vulcan 65C 28.91 0.39

Vulcan 140C 62.3 0.39

Vulcan 400C 177.9 0.42