钻孔灌注桩施工对邻近既有隧道影响数值分析

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

目的研究单桩和群桩施工对地层位移场和邻近既有隧道结构变形的影响规律,为后续类似工程施工提供技术参考.方法以南京龙津桥改建项目桩基工程为背景,通过现场实测验证数值模拟,并进行数值模拟参数敏感性分析.结果桩基尺寸越大、桩基重心与隧道间距越近均会加剧施工变形;坍塌区域变形急速发展,而套筒能有效约束变形;桩基施工影响深度可划分为强影响区、一般影响区、弱影响区;群桩中的已存在桩对挤土效应具有阻挡效应.结论建议近隧桩基施工采用全套管灌注桩施工工艺,配合梅花型布置方式,单桩最小安全施工距离为3倍桩径,群桩最小安全施工距离为6倍桩径.

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.