大跨超浅埋轻轨车站隧道开挖方法研究

STUDY OF EXCAVATION METHOD FOR ULTRA-SHALLOW-BURIED LIGHT RAILWAY STATION TUNNELS WITH LARGE SPAN

针对大坪车站隧道工程跨度大、埋深浅、地面人口及建筑密集等情况,经过方案比较选择,参考施工过程中力学行为模拟分析结果,在地铁工程施工中提出了“在大管棚预支护下,上半断面侧壁导坑法,下半断面先中槽后侧墙开挖、先拱后墙衬砌”的隧道施工新方法,成功建成了特大跨、超浅埋城市车站隧道。

Chongqing Daping light railway station is located in downtown of Chongqing, where there is a dense population as well as numerous buildings. Daping station tunnel has a clear span of 19.8 m, whereas its excavation span and area are 26.3 m and 430.3 m2, respectively, only 4 m overburden and with a surrounding rock of category III. In view of complex and unfavorable surface conditions over the station tunnel, such as house buildings and city roads, both of which can't resist severe shocks or vibrations, it is necessary that small vibrations induced in tunnel construction process and a strict requirement for the surface subsidence amount be favourable. According to the characteristics of large span and ultra-shallow-buried, located in a densely populated city area of numerous buildings, a new method is proposed to use advanced support of large pipe-roof protection and the tunnel section is divided into two parts during the process of construction. The upper part is operated by using two-side pilot drifting method, while the lower part is excavated from the middle to walls, and the arch lining is constructed before the tunnel wall-lining. The method is developed from numerical simulation of the deformation of rocks during the tunnel construction. The application of this method proves to be successful in the construction of Daping light-railway station tunnel.