The behaviour of pile group and combined piled-raft foundation in liquefiable soil under seismic conditions.

Abstract

This paper highlights the beneficial usage of Combined Pile-Raft Foundation (CPRF) over conventional pile group foundation subjected to seismic loading in liquefiable soil. Firstly, a single pile resting on a liquefiable soil is numerically modelled and subsequently validated with available dynamic centrifuge test result by using finite difference based computer programme, FLAC3D. Thereafter, the model is extended for simulating CPRF and pile group.Further parametric studies are performed to understand the effect of pile spacing (s), pile length (l) and different seismic motions on the behaviour of CPRF and pile group. Results are presented in terms of normalised bending moment (M/Mmax), shear forces and pore water pressure (PWP) ratio. Increase in shear resistances in the range of (35 – 60)% and (40 – 70)% are observed for the piles in CPRF over the conventional pile group foundation, having a pile spacing of 2 to 5 times of its diameter (d) and the (l/d) of 14 to 20, respectively. These outcomes portray the advantages of employing CPRF over pile group founded in liquefiable area under seismic loading.