多条既有轨道交通区间隧道上方近距离深大基坑围护方案设计及研究

Design&Research on the Support Scheme of Close Distance Deep&Large Foundation Pit above Multiple Existing Rail Transit Interval Tunnels

依托杭州市余杭区某地块项目配套工程,对水乡北路过现状河流箱涵及驳岸结构建设涉及到的深大基坑进行围护方案设计研究,其重难点主要在于基坑位于杭州市轨道交通L3、L5、L16区间隧道正上方,且基坑底距离区间隧道最近处仅5.0 m。研究采用MJS工法桩结合IMS工法桩进行组合式坑底加固及基坑围护措施。同时结合现状地形条件进行精细化网格划分开挖区域并提出合理开挖步序,旨在控制轨道交通区间隧道上方土体卸荷比并最大程度降低对隧道的扰动,有效控制区间变形。再通过建立等比例基坑和轨道交通隧道的3D数值模型进行设计验证,根据数值模拟结果,基坑开挖对轨道交通隧道的影响可控。

Based on the supporting project of a certain plot of land in Yuhang District,Hangzhou,it focuses on the design and research of the enclosure scheme for the deep foundation pit involved in the construction of the box culvert and revetment structure of the existing river on North Shuixiang Road.The main difficulty lies in the fact that the foundation pit is located directly above the L3,L5 and L16 section tunnels of Hangzhou's rail transit,and the bottom of the foundation pit is only 5.0 m away from the nearest section tunnel.The research adopts the combination of MJS construction method piles and IMS construction method piles for combined pit bottom reinforcement and foundation pit enclosure measures.At the same time,based on the current terrain conditions,the excavation area is finely divided into grids and a reasonable excavation sequence is proposed,aiming to control the unloading ratio of the soil above the rail transit section tunnel and minimize the disturbance to the tunnel,effectively controlling the deformation of the section.Further design verification is conducted by establishing 3D numerical models of equally proportioned foundation pits and rail transit tunnels.Based on the numerical simulation results,the impact of foundation pit excavation on rail transit tunnels is controllable.