Numerical Analysis on Influence of Adjacent Operated Tunnel Caused by Bored Pile Construction

Abstract

This paper aims at investigating the impact of single pile and pile group construction on the ground displacement and structural deformation of adjacent existing tunnel.The findings in this paper provide guidelines for similar construction projects.Based on a reconstruction project for Nanjing Longjin Bridge, numerical simulations were verified by in-situ measurement results.A sensitivity analysis was also performed to evaluate the sensitivity of parameters required for simulation.The simulation revealed that greater deformation could be a direct result of a bigger pile foundation or smaller spacing between the pile and existing tunnel.The deformation in the collapsed area developed rapidly while the sleeve of the benoto pile could effectively restrain the deformation.The depth under the influence of pile foundation construction can be divided into three zones:strong, average, and weak zone.The existing piles in the pile group would weaken the soil squeezing effect.It is suggested that with a nearby existing tunnel, benoto pile should be adopted to reduce the impact on the tunnel and the setup of piles should be quincuncially distributed.The minimum spacing of single piles is 3 times of the pile diameter while the minimum spacing of group pile is 6 times of the pile diameter.