填土地区基坑开挖卸载对下伏地铁隧道的影响分析

Analysis of effect of foundation pit excavation on underlying metro tunnel in filled area

随着城市市政与轨道交通工程的突飞猛进,基坑跨骑于已建地铁隧道之上的情况时有发生,基坑开挖时如何有效控制下伏地铁隧道的隆起变形成为热门课题。以太原市解放路万达广场下穿通道基坑为例,为控制下伏地铁隧道的变形,基坑设计采用了钢板桩+钢支撑与竖向+水平向止水帷幕的支护与截水形式,结合坑底加固、分区开挖等技术措施。同时采用三维有限元软件MIDA S-GTS对基坑支护与开挖进行全过程数值模拟,通过与实测结果对比显示基坑开挖卸荷引起的下伏地铁隧道变形满足相关部门和规范的要求,基坑开挖不会影响下伏地铁隧道的安全,表明该工程采取的技术措施是合理有效的。

With the rapid development of urban municipal and rail transit construction,it often happens that foundation pit straddles the existing metro tunnel.How to effectively control the uplift deformation of the underlying metro tunnel during the excavation of foundation pit has become a hot topic.Taking the foundation pit of Wanda Plaza underpass of Jiefang Road in Taiyuan as an example,in order to control the deformation of the underlying metro tunnel,steel sheet pile,steel bracing,vertical and horizontal water-stop curtain were adopted in the design,combined with technical measures such as pit bottom reinforcement and partition excavation.At the same time,the three-dimensional finite element software MIDAS-GTS is used to simulate the whole process of foundation pit support and excavation.The results show that the deformation of the underlying metro tunnel caused by the unloading of the foundation pit excavation meets the requirements of the relevant departments and specifications,and the excavation of the foundation pit will not affect the safety of the underlying metro tunnel,indicating that the technical measures adopted in this project are reasonable and effective.