地下铁道由区间隧道扩挖三联拱隧道施工技术

Construction Technique of a Three-connected-arch Tunnel by Excavating from the Normal Route Tunnel in Subway

北京地下铁道某地下区间设计有一段大断面三联拱隧道,由于受开挖工作面的限制,采取从区间隧道扩挖的施工方案。拟定了双侧壁导坑法结合CRD工法施工的方案;采用FLAC模拟该断面施工顺序,确定每步开挖工序产生的沉降值,制定了施工控制标准;介绍了该断面初期支护参数、由区间标准断面转换到三连拱隧道的工法及工程效果。建立的分步控制沉降的施工控制模式,有利于控制每一步序沉降值;三联拱隧道段沉降、变形稳定,满足施工控制值的要求。

There is a three-connected-arch tunnel with large sectional area in the designed the route tunnel in Beijing Subway. Owing to the limitation of excavating space, a construction scheme tunneling from the normal route tunnel is drawn up, which is a combination of both side drift method with center cross diaphragm method. The constructed sequence is simulated by FLAC （Fast Lagrangian Analysis of Continua） to solve settlements caused in each excavated step, and the settlement control values are established. Primary supporting parameters, construction method transformation from the normal route tunnel to the three-connected-arch tunnel, and engi- neering practice effects are introduced respectively. This construction control mode is beneficial to the settlements control in each step. The deflections and settlements of three-connected-arch tunnel tend to be stable and meet the requirements of the construction control values.