南宁半成岩地层明暗挖地铁车站关键技术及数值分析

Key Technologies and Numerical Analysis of Metro Station by Cut-and-cover and Mining Method at Semi-diagenetic Stratum in Nanning

为解决半成岩地层明暗挖地铁车站施工中存在的问题,结合南宁地铁3号线青秀山站,采用数值模拟分析与现场监测相结合的方法,对半成岩地层明暗挖结合地铁车站修建过程中遇到的关键问题进行分析,并提出解决问题的具体方法。研究结果表明:1)在富水半成岩地层中修建隧道可采用群井降水的方法对地层进行加固,降水后围岩黏聚力大幅度增大,有利于隧道开挖;2)站台层隧道群开挖时应合理安排施工工序,横通道在距离正线隧道开挖面大于1倍隧道洞径后方可开挖,斜扶梯通道宜在横通道二次衬砌完成后开挖;3)群洞隧道三岔口部位应根据工程条件予以加强设计,尤其是在隧道纵向上;4)在一定条件下,明挖站厅层在站台层暗挖隧道群之前施工是可行的。

The key problems encountered during the construction of Qingxiushan Station on Nanning Metro Line No.3 in semi-diagenetic stratum by cut-and-cover and mining method are analyzed based on numerical analysis and site monitoring;and some corresponding countermeasures are put forward.The research results show that:(1)The multiple well dewatering method can be used to consolidate the stratum in water-rich semi-diagenetic stratum;the cohesion of the surrounding rock is improved greatly after dewatering,which can provide favorable conditions for tunnel excavation.(2)When excavating tunnel group in the platform layer,the construction procedure should be reasonably arranged;the horizontal channel can only be excavated when the distance between the excavation face of the main tunnel and the horizontal channel is greater than 1 times of the tunnel diameter;and the ramp passage should be excavated after the cross passage lining reaches the strength.(3)The intersection of the tunnel should be strengthened according to the engineering conditions,especially the longitudinal direction.(4)Under certain conditions,it is feasible to construct the open-cut structure on the station floor before the tunnel group is excavated on the platform floor.