Test: Pile Foundation - Civil Engineering (CE) MCQ

Under-reamed pile is a special type of bored pile which is provided with a bulb/pedestal at the end. The usual size of such piles are 150 to 200 mm shaft diameter, 3 to 4 m long. The diameter of under-reamed portion is usually 2 to 3 times the shaft diameter.

Let's evaluate the statements about piles:

1. Piles are provided in groups, which are connected together by a pile cap. The structure rests on top of the pile cap. The pile cap is situated below the ground level.

   • This statement is correct. Piles are often used in groups and connected by a pile cap to distribute the load from the structure above. The pile cap is typically situated below the ground level to provide stability.

2. For situations where a pile is subjected to an upward pull, pedestal piles or under-reamed piles are more suitable types of foundations.

   • This statement is also correct. Pedestal piles and under-reamed piles are designed to resist uplift forces due to their enlarged bases, making them suitable for situations where there is an upward pull.

Therefore, the correct option is:

   3. Both 1 and 2

The load carried by skin-friction only 

For clay deposits ultimate load of pile is given by, 

cN_cA_p accounts for end bearing while accounts for frictional resistance.

Resistance load due to skin friction A_s is surface area of pile over which skin friction acts = π D x L = πLD

Static formula gives the ultimate capacity of an individual pile
Hileys formula and Engineering news formula are dynamic formula to calculate the load-carrying capacity of a driven pile
In Cyclic loading test an incremental load is repeatedly applied and removed to separate skin friction and end bearing of a pile.

The settlement of a group of piles in more than the settlement of a single pile even when the load on the single pile and the load on each pile of the pile group are same. This is because of the fact that the zone of influence of a pile group is much deeper than that of a single pile.