Calculating Method of Pile Bearing Capacity Loss Induced by the Tunnel Excavation Underneath the Pile

Abstract:

A method was proposed to calculate the pile bearing capacity loss induced by the tunnel excavation underneath the pile. The hyperbolic loadtransfer function considering the effect of tunnel excavation at the pilesoil interface was compiled and based on it, the Q~s curves of the pile and that after tunnel excavation were figured out. Ultimate bearing capacity of pile was confirmed where pile settlement was fifty millimeter, and it was used as the indicator to measure the influence caused by the excavation. The variation of bearing curve and pile forces as well as influencing factors to the bearing capacity were analyzed based on one work point of Hangzhou Metro Line 1. The bearing capacity loss of pile is 22% when volume loss rate is controlled at 0.5%. After tunnel excavation, there is a position in the pile where the lateral friction is unchanged, while the lateral friction increases upper the position and decreases bellow the position. The bearing capacity loss has a positive correlation with volume loss rate and Initial load of pile, however, has a negative correlation with the distance between the bottom of the pile and the top of the tunnel.