Parametric Study of the Behavior of Large Piled Raft Foundation on Stiff Clay

Abstract

This paper presents a parametric study conducted numerically for large piled rafts on stiff clay. The pile number, pile length, pile spacing and raft thickness effects were evaluated on the behavior of large piled rafts in terms of the differential and average settlements, bending moment of the raft and load sharing. The configurations of piled raft adopted in the study ranged from 5 × 5 to 13 × 13 piles distributed uniformly underneath the raft. The pile length was varied between 10 and 30 times the diameter of the pile. The pile spacing effect was observed for any piled raft configuration such that the area enclosed by the pile group underneath the raft varied from 0.2 to 0.9 times the raft area. The raft thickness was varied to ensure that its stiffness changed from flexible to intermediate and to rigid. Results of the study show that average settlement reduces with increment in pile number and pile length. The differential settlement decreases as raft thickness increases but at the cost of higher bending moments. The addition of piles is not beneficial in reducing the bending moments when compared to an unpiled raft. With an increase in the number of piles and pile spacing, there is an increment in the load the piles carry. For the same pile number and pile spacing, linear increment of the loads the piles carry was observed with increasing pile length.