Shaking Table Investigation of Seismic Performance of Micropiles

Micropile foundations are progressively recognized worldwide because of their significant advantages such as flexibility, ductility, capacity to withstand extension forces and installability in different ground conditions causing minimal noise and disturbance. Owing to this increasing application of micropile systems, particularly in seismic prone areas, studying their response to seismic excitation is of great importance. In this study, shaking table experiments were carried out on a small-scale physical model of micropiles. The physical model consisted of a 4 x 4 group of micropiles installed in loose sand. The scaled horizontal acceleration time history of 1995 Kobe earthquake was applied to the base of soil container and response of soil and micropile system was monitored in terms of horizontal acceleration and variation of bending moment induced along two model micropiles. Analysis of the results of shaking table tests showed that acceleration on both soil surface and micropiles cap were amplified with respect to the input excitation acceleration. The horizontal acceleration response on micropiles cap was smaller than response of soil surface. Maximum bending moment was observed at the mid-length of both model micropiles and corner micropile experienced higher bending moment compared to center micropile.