An Experimental Study on the Topography Effects on the Seismic Response of Combined Piled Raft Foundation

Abstract

The effect of topography on the amplification of seismic forces has been considered in regulations, and they have deemed the use of the seismic force amplification coefficient in the design of adjacent earth-retaining structures necessary. However, the impact of settlement-reducing or anti-sliding piles under the building foundation on the applied acceleration to the foundation is generally not addressed in regulations, and it is necessary to carefully examine this issue for the optimal design. This study sought to empirically assess the impact of using piles as Combined Piled Raft Foundation (CPRF) positioned on the top of slopes, with different slope angles, on the seismic behavior of slopes, scaled at 1/25^th, through shaking table experiments. Six sinusoidal waves were created as input motions to simulate a range of earthquake scenarios, applied to the models to collect data for analyzing the seismic response of the system. No.161 Firouzkooh sand was utilized as the soil in this investigation. The amplification factor (AF) of various locations was used to examine the seismic response of the system. The findings underscore the importance of the amplification factor as a critical parameter in evaluating the seismic response of foundations situated on slope crests. Additionally, Implementing CPRF and longer piles had a mitigating effect on accelerations at most points and improved the seismic response of the slopes, reducing amplification factor and led to less damages. Furthermore, the slope angle was shown to significantly influence the seismic response, with steeper angles generally resulting in higher amplifications at the slope crest.