地铁深基坑开挖对下部既有公路隧道的影响分析

以昆明地铁3号线西山公园站深基坑工程骑跨既有公路隧道为工程背景,利用Midas-GTS建立二维数值模拟深基坑全过程,研究基坑开挖对下方既有隧道的变形影响规律。分析坑内加固和基坑时空效应施工措施对控制隧道上抬变形的影响,结合现场实际监测数据和有限元分析表明:(1)基坑开挖对下部岩体具有显著的垂直方向卸荷作用,其受力状态和形状的改变程度受限于上部土体性质、土体开挖量、开挖方式及隧道围岩性质;(2)坑内加固后可明显降低隧道衬砌的隆起变形,降幅约为18%;(3)实际监测数据略小于计算结果,但变形趋势二者较为吻合。

Analysis of Influence of Deep Foundation Pit Excavation on Existing Highway Tunnel

Based on the deep foundation pit of Xishan Park Station of Kunming Metro Line 3,Midas-GTS is used to conduct two dimensional numerical simulation of deep foundation pit and study the effect of deformation of foundation pit excavation on the existing tunnel below. This paper analyzes the influence of the construction measures of pit reinforcement and the space time effect of foundation pit on the deformation of the tunnel in the light of the actual monitoring data and finite element analysis. The results show that:(1) pit excavation has significant unloading effect on the lower part of the vertical rock mass,the stress condition and shape change degree are limited by the upper soil properties,soil excavation quantity,excavation pattern and tunnel surrounding rock properties;(2) the reinforcement of the tunnel can obviously reduce the uplift deformation of the tunnel lining by about 18%;(3) the actual monitoring data are slightly less than the calculation results, but the deformation tendencies of the two are fundamentally identical.