风井开挖与盾构下穿对周边环境影响研究

Impact Study of Ventilation Shaft Excavation and Shield Tunneling on the Surrounding Environment

为研究砂卵石地层盾构隧道下穿区间风井基坑对临近建筑结构及地表沉降的影响,结合成都地铁17号线区间风井盾构隧道下穿工程,构建三维数值模型。对风井基坑开挖、支护、盾构穿越风井的全过程施工阶段对临近建筑物的影响进行数值模拟研究,得到了不同施工阶段建筑物变形以及盾构下穿砂卵石地层的临近建筑物变形规律和地表沉降规律以及应力分布结果,发现基坑开挖后地表最大沉降并不是分布于基坑边缘,而是远离基坑边缘一定距离。同时超前模拟了盾构下穿风井过程中地表隆起与沉降的过程,以及对周边建筑的影响程度。通过数值模拟结果和现场实测结果构建地面沉降预测模型,利用Peck修正公式对地表变形进行了计算,结果表明沉降预测模型与埋深密切相关,建立起成都地区深厚砂卵石地层城市盾构下穿风井的地表沉降预测模型,可为类似砂卵石地层盾构施工提供参考。

In order to study the adjacent building displacement and ground surface settlement when a shield beneath interval air shaft foundation pit in sandy cobble stratum,3-D FEM simulating analysis was used to implement the numerical simulation based on the Chengdu Metro Line 17,which passed an air shaft,as the engineering context for the study.The influence of the whole construction process of foundation pit excavation,support and shield driving on the adjacent building displacement and ground surface settlement were respectively investigated.The results of building deformation,deformation law of adjacent buildings under shield tunneling in sandy cobble stratum,ground surface settlement and stratum stress distribution under different construction stage and different construction step was obtained.It is found that the maximum surface settlement after foundation pit excavation is not distributed at the edge of the foundation pit,but a certain distance away from the edge of the foundation pit.simultaneously,it also simulated the process of surface uplift and settlement in the process of shield tunneling through the air shaft,as well as the impact on the surrounding buildings.The ground surface settlement prediction model was proposed based on the numerical simulation and the in-site measurement results,and the revised Peck formula was used to calculate ground surface settlement,the result shows that the settlement prediction model is closely related to the burial depth.The settlement prediction model of air shaft under urban shield in deep sandy cobble stratum in Chengdu was established.Meanwhile,this simulation results can provide reference for shield construction in similar sandy cobble stratum.