超小净距特大断面地铁车站施工关键技术

Key Technologies in Subway Station Construction with Super-small Clear Space and Super-large Section

重庆地铁礼嘉车站为地下二层双洞4线双岛暗挖车站,最大断面达856 m2。通过数值计算结合现场实测对中岩柱单边落底法施工的特大断面、超小净距、多交叉口隧道进行了研究,分析了不同开挖步序时拱顶位移以及中岩柱宽度、先后行洞合理施工纵距对隧道施工的影响。研究表明:大断面隧道采用中岩柱单边落底施工方法是可行的,中岩柱单边落底施工方法的关键工序是第1步序和第2步序的开挖,施工中应加强监控等措施;中岩柱的宽度宜大于1.5 m;后行隧道与先行隧道间的施工纵距取20 m是合理的。

The Lijia Station of Chongqing metro is a 2 layer underground station with two holes and four lines,the maximum section of which is 856 m2. Combining the field measurement with numerical calculation,a research is conducted on the super-large section,super-small clear distance and multi-intersection tunnels constructed by the middle rock pillar and unilateral drop bottom construction method,the vault displacements in different excavation steps,the influence of the middle rock pillar width and the reasonable construction spacing of successive holes on the tunnel construction are analyzed. The results show that it is feasible to construct the large section tunnels by the middle rock pillar and unilateral drop bottom construction method,in which the key process is the excavation at the first and the second steps. Therefore,monitoring and other measures should be strengthened,the width of middle rock pillar be defined greater than 1.5 m,the reasonable clear-distance between the first hole and the second hole be controlled in 20 m.