Seismic Performance of Deposit Slopes With Underlying Bedrock Before and After Reinforcement by Stabilising Piles

Abstract

The seismic performance of stabilising piles used to reinforce underlying bedrock in a deposit slope is a complex soil-structure interaction problem, on which there is limited design guidance on the optimum use of a single row of rock-socketed piles to reinforce such slopes. Two centrifuge shaking-table model tests at a geometric scale of 1:50 were conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilising piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. Under seismic excitation, the differences in the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The two are prone to uncoordinated movement, which leads to slope instability. Setting stabilising piles reduces the crest settlement and angular deformation and changes the natural frequency of the slope crest. The presence of the rock-socketed stabilising piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. According to the mobilised pile bending moment, shear force, lateral pile-soil load distribution, and pile displacement, the dynamic response characteristics of stabilising piles under continuous multi-level seismic excitation were analysed. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part (the point of action of the resultant force is 1.54m below the slope surface). With increases in the peak ground acceleration (PGA) of the input motion, the resistance of the bedrock in front of the stabilising piles increases; moreover, with the increase of PGA, the peak resistance under the bedrock surface of the stabilising piles gradually moves downwards. This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilising pile.