The effect of interaction on pile-raft system settlement subjected to earthquake excitation

Piled raft is a geotechnical composite structure consists of three elements: piles, raft, and soil. It is, usually, utilized as a foundation for tall building. During earthquakes, a soil-pile, soil-raft, and pile-raft elements are subjected to a complex system of stresses. Stress–strain behavior of soil is, usually, hysteric and non-linear. The problem is further compounded by the interaction of stress waves and soil and piles. Due to significant increasing in seismic activity in world during the last decades especially in Middle East reign, the response of piled raft system needs more attention. This paper aims to study interaction of sandy soils with piled raft and detecting its effects on settlement using numerical analysis by finite element method. PLAXIS 3D package was used as a finite element simulator. The results indicated that there is minor differences in settlement with rigid interface case (R=1) in comparison to the other interface cases (R=0.1-0.9). In addition, the settlement of piled raft, slightly, varies with the size and strength of their interface elements (adhesion and wall friction) to the soil strength (cohesion and friction angle).