[PPT]Bearing Capacity from SPT and PLT - WordPress.com · Web viewBearing capacity of Piles in group By: Alka Shah Assistant professor Civil Department Nirma University Plie Group

Bearing capacity of Piles in group

By:Alka Shah

Assistant professorCivil DepartmentNirma University

Plie Group

Plie Group

Generally Qug ≠ n QuQug = ultimate load capacity of pile groupn = number of piles in group

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

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 is select as smaller of the two values determined from below two criteria:

1. Qug = n Qu2. Qug = pile group as a equivalent single large pile (consider as a block)

Efficiency of pile group = 𝞰g = Qug/n Qu

Ultimate Load Carrying Capacity of Pile Group

Spacing of Piles

2.5 B to 3.5 B is preferable

Negative Skin Friction

Negative Skin Friction

Negative Skin Friction

Negative Skin Friction

Pile Group Settlement

In group of pile all pile set equally due to rigidity of pile cap

But settlement of group is more then the single pile due to stress zone

Pile group in clay fail due to settlement then the bearing pressure

Settlement of pile group is determine by assuming the entire pile group as an

equivalent raft located at depth 2/3 D

Load distribution diagram is also shown

Width of raft = {B + 2 (1/4) * (2/3 D)}