DefinePK

Abstract

Piles are commonly connected using a raft to maintain group action and ensure overcoming any expected differential settlement. Although the raft is indirect contact with subsurface strata, conventional design system ignores the load transferred from raft to the soil due to this contact and encounter on the pile group bearing capacity and settlement. However, piled raft foundations that are not directly rested on soil such as the bases of the bridges and in case of settlement or scoured of soil underneath the raft do not take much attention. In the present study, the effect of group efficiency as well as the load distribution of the friction along the pile shaft the load transferred to the tip of the pile and load transferred to soil underneath pile cap in pile groups in cohesion less soil have been presented. The piles were tested in a setup under compressive axial loads. Load at pile tip and the strain along the piles as well as the pile head loads were measured simultaneously. Furthermore, the load under pile cap transferred directly through pile cap to soil has been measured. The program consisted of installing test piles in dense sand, placing piles in a soil chamber subjected to compressive axial load. However, three groups of testing were performed in axial compression. First group load test was carried out on single pile. Second group is four pile caps rested on soil. Third group is four pile caps non-rested on soil. The load capacity of the piles was established and the load distributions along pile walls were determined at various depths. In addition, the loads at pile tip and underneath the pile cap were measured by load cells. It was found that the group efficiency of pile groups cap of four pile rested on soil is more than that pile group cap of four pile non-rested on soil. The group efficiency was found to be ranging between 1.25 to 1.65. The load transferred to soil underneath pile cap was found to be 8 % from the ultimate load capacity. The settlement of pile groups for piles cap rested on soil is less than that for pile cap non-rested on soil. Finite element analysis gives values of settlement less than experimental test results. Fair agreement has been obtained between finite element analysis and experimental test results.