Influence of Combined Vertical and Lateral Loading on Lateral Response of Piled Raft Foundation

Abstract

Due to the complexity involved in analysing the piled raft foundation under combined loading, the existing design practice for the piled raft assumes that the influence of vertical and lateral loads is independent of each other and the experimental tests on the behaviour of piled raft foundation under the action of combined vertical and lateral loads are relatively scarce. Therefore, the objective of the present study is to examine the behaviour of piled raft foundation subjected to pure lateral loads and combined vertical and lateral loads through laboratory model tests. The experimental programme includes the prototype model test on raft braced by 2 × 2 and 3 × 3 pile groups. The laboratory tests are performed in silty-clay soil underlain by sandy soil. Initially, the response of the piled raft foundation under pure lateral load is performed through laboratory model test and to understand the response of the piled raft foundation under combined loads, and the influence of vertical loads equal to 0.25Vu, 0.5Vu, 0.75Vu and 0.9Vu are considered. The ultimate vertical load capacity (Vu) corresponding to the settlement of 10% of raft width is evaluated by a separate vertical load test. The results of the experiments have shown the significant influence of vertical loads on a pile’s lateral response. For the structural design of piled raft, it is important to find out the bending moment developed in the pile in piled raft. Therefore, the influence of combined loading on the bending moment developed in the pile has been examined from the laboratory model test.