Bearing capacity of Piles in group By Alka

Bearing capacity of Piles in group By: Alka Shah Assistant professor Civil Department Nirma University

Plie Group

Plie Group Generally Qug ≠ n Qu Qug = ultimate load capacity of pile group n = number of piles in group

Ø But soil between the individual piles may become locked due to densification from driving and group may tend to behave as an equivalent single large pile Ø These tend to increase the group capacity to be greater then the sum of capacities of the individual piles

Ultimate Load Carrying Capacity of Pile Group Ø Ultimate load carrying capacity of pile group is select as smaller of the two values determined from below two criteria: 1. Qug = n Qu 2. Qug = pile group as a equivalent single large pile (consider as a block) Ø Efficiency of pile group = �� g = Qug/n Qu

Spacing of Piles 2. 5 B to 3. 5 B is preferable

Negative Skin Friction

Pile Group Settlement Ø In group of pile all pile set equally due to rigidity of pile cap Ø But settlement of group is more then the single pile due to stress zone Ø Pile group in clay fail due to settlement then the bearing pressure Ø Settlement of pile group is determine by assuming the entire pile group as an equivalent raft located at depth 2/3 D Ø Load distribution diagram is also shown Ø Width of raft = {B + 2 (1/4) * (2/3 D)}