基坑开挖及上盖荷载对下卧隧道结构的影响分析

广州珠江新城核心区市政交通项目金穗路以北地下空间基坑位于地铁隧道正上方,基坑开挖、工程(人工挖孔)桩及上盖荷载施工对地铁隧道结构的影响为该工程的关键问题。为此,利用MIDAS/GTS建立有限元模型,对实际的施工工况进行模拟。研究结果表明:隧道结构处于中风化地层的变形量仅为强风化地层的1/3;近距离人工挖孔桩、隧道上方上盖荷载施工及增大转换梁的刚度均能在一定程度上约束隧道的水平和竖向变形;土体偏压开挖对隧道结构水平方向变形影响较大。根据研究结果,提出对下方既有隧道的保护措施,以确保地铁结构安全和正常运营,为设计和施工提供指导意见。

Study on influence of deep excavation and cover load on the underlying subway tunnel structure

The deep excavation of the municipal traffic project in the north of Jinsui Road in the core area of Zhujiang New Town in Guangzhou is above the operating subway tunnels,so the impact of foundation pit excavation,engineering(artificial dig-hole) pile construction and the cover load on the subway tunnels become a key issue.For this reason,a model was established and the actual construction conditions were simulated using MIDAS software.The results show that: the deformation increment formation in the middle of weathering occurred only 1/3 in the strongly weathered around the tunnel shield;the close artificial dig-hole pile on the edge of subway tunnels,the cover load and increasing the stiffness of the beam transformation can bind the vertical and horizontal deformation;the influence of the eccentric soil excavation is much bigger on the horizontal deformation of tunnel structure.Based on the results,the protective measures were proposed to ensure the structural safety and the normal operation of subway tunnels,which provide useful references to the design and construction.