What is Pile Grouping in Pile Foundation?

Pile is a deep foundation. This is a way to transfer loads from superstructure through the pile, developing frictional capacity and end bearing, to firm stratum. This is obvious, that a single pile cannot always enough to bear the loads from column to be supported. To provide additional support to carry actual loads safely piles are grouped. In the group piles are arranged to perform together with perfect embedment like pile cap.Theoretically, it is found that load bearing capacity of piles in a group having several piles are not the same of the multiply of individual pile bearing capacity and number of piles. Actually the group capacity of piles is less than that of sum of individual pile capacity. This observation valid not only in theory but also in practical. This is due to overlap of zone of individual piles stress with adjacent piles in supporting soil. Due to overlapping no pile can develop their full capacity. Thus reduction in capacity is occurred. The degree of reduction of individual pile depends mainly on:

a. Size of each pile

b. Spacing of piles

c. Length of each piles

d. Size of pile group

e. Shape of pile group

However, some piles that mainly develop their capacity by end bearing and whose capacities are not dependent on skin friction, no significant reduction is observed. This condition is found in cohesionless soil. In this soils load bearing value of pile group can be determined by multiplying load bearing value of individual pile and number of piles in group.