Effect of Pile Configuration on the Behavior of Piled-Raft Foundations in Sandy Soil

In this research, an experimental investigation to examine the behavior of piled-raft foundations in loose sand is introduced. A small-scale model was tested in a sandy soil container. Three sensors were fabricated on the pile heads to record the axial load induced by any pile in the group, and the foundation's settlement was also measured. In addition to experiments for an unpiled raft, model groups for 1 pile, 1 x 2, 1 x 3, 2 x 2, 2 x 3, 3 x 3, 3 x 3 triangle heaps, 4 diamond piles, 5 piles, and 9 circle piles were tested in the lab. The loading test was carried out until a relative pile displacement of 10 % of the length of the raft was passed. It was found that the piled-raft models with piles placed in uniform configurations (2 x 2 and 3 x 3) showed an increase in bearing capacity higher than that of piled rafts with the circle and diamond configurations, but not higher than that of triangular configuration. Also, it was found that when the value of loading was 1,000 N and the pile spacing increased from 2.5d to 3d, the settlement increased from 11 to 13 mm, 9.5 to 11 mm, 8.5 to 10 mm, and 7 to 9 mm for models PR2, PR3, PR4, and PR5 (referring to 2-, 3-, 4-, and 5-piled-raft models), respectively. In practically the whole settlement range tested, the results demonstrated that the contribution of the edge and center piles was considerably higher than that of the single piles underneath the raft. The axial loads carried by the edge and the center piles for the PR9, PR5, and PR3 piled-raft types, respectively, were roughly 40 % and 70 %, 52 % and 70 %, and 20 % and 60 % higher than those for the PR1 pile capacity.