The effects of installation order on the response of a pile group in silica sand

Abstract

The pile (and micropile) group effect in sand remains a key issue in civil engineering. This paper describes an experimental study carried out using a calibration chamber and an instrumented model pile installed by jacking. A specific methodology is proposed to study group effect through a generic pile within the group. A pile group can be modeled by a group of five piles, one central pile and four adjacent piles. The central pile represents a generic pile within a group with a large number of piles, and the calibration chamber enables the performance of a parametric study to evaluate the global and local (tip resistance and shaft friction) group effects and quantify them using the efficiency coefficient factors relative to tip resistance and shaft friction. The effect of parameters, such as the pile-to-pile spacing ratio and the installation order on pile group response has been investigated. The instrumented generic pile is designed to study independently tip resistance and shaft friction. The results show that the installation order has a significant influence on the pile group response. Some recommendations from laboratory tests are proposed to optimize pile installation in the case of a group and benefit from group effect.