LOAD-SETTLEMENT AND LOAD-SHARING BEHAVIOUR OF A PILED RAFT FOUNDATION RESTING ON LAYERED SOILS

To understand the load-settlement and load-sharing behaviour of a piled raft foundation resting on different layered soils, small-scale laboratory model tests were conducted. The investigational programme includes a prototype model test on an unpiled raft, braced by a single pile, 2 x 2 and 3 x 3 pile groups. 3D numerical analyses were also implemented to ensure the experimental model's verification and to explore the settlement criterion of the piled raft foundation. The influences of the number of piles, the diameter of the piles and the raft sizes on the ultimate failure load, the load-improvement ratio and the percentage load carried by the raft at different settlement levels and different types of settlements that influence the foundation design criteria are illustrated. The relative contributions of these different design variables were also found using statistical analyses. The test results show the efficacy of using piles as settlement reducers with the raft. From the studies it is clear that as the number of piles below the raft increases from 1 to 9, the load-improvement ratio increases by 20% to 69%, whereas the load shared by the raft decreases with the addition of piles below the raft. From the numerical analyses it was found that the normalized differential settlement of the rafts can be optimized by introducing a number of piles in the central area of the raft.