浅埋偏压大断面暗挖地铁车站工法优化研究

Study on Optimization of Construction Method for Shallow Buried Large Section Mined Subway Station with Asymmetrical Loading

在城市复杂环境下采用暗挖法修建大断面隧道,不同开挖工序、台阶划分等因素对隧道结构内力、变形和围岩应力有着较大影响。以重庆铁路枢纽东环线金山隧道国博中心站工程为背景,结合实际的偏压地形及初步设计方案,采用数值模拟方法研究了双侧壁七步法及不同工序的双侧壁九步法的施工效果。研究结果表明:(1)当车站隧道采用双侧壁七步法施工时,地表竖向沉降及隧道拱顶沉降均较小;(2)当车站隧道采用双侧壁九步法开挖时,容易导致支护结构局部应力集中;(3)双侧壁九步法及七步法对应的隧道围岩塑性区延伸范围区别较小,且三种工法施工后结构偏压效应基本相当;(4)与双侧壁九步法相比,双侧壁七步法工序转换少,便于施工通风和出渣,在施工效率方面具有优势。

As for large-section mined tunnels in the complex urban environment,such factors as excavation procedures and bench division have a great impact on the internal force,deformation of the tunnel structure and the surrounding rock stress.Taking the International Expo Center Station Project in Jinshan tunnel of the East Ring of Chongqing railway terminal as the background,combined with the actual asymmetrically loaded terrain condition and the preliminary design scheme,this paper studies the construction effect of the double side drift seven-step method and the double side drift nine-step method with different construction processes by numerical method.The results show that:(1)when the station tunnel is constructed by the double side drift seven-step method,the vertical settlement of the ground surface and the settlement of the tunnel vault are small;(2)when the station tunnel is excavated by double side drift nine-step method,it is easy to cause local stress concentration of the support structure;(3)the extension range of the plastic zone of the tunnel surrounding rock caused by three construction methods is not different,and the asymmetrical loading effect of the three construction methods is basically the same;(4)compared with the double side drift nine-step method,the double side drift seven-step method has less process conversion,is convenient for construction ventilation and mucking,and has advantages in construction efficiency.