某公路特大断面隧道施工方案优化分析

Optimum Analysis of the Construction Procedure of a Tunnel with a Very Large Cross Section

双侧壁导坑法适用于Ⅴ级围岩隧洞开挖,可大大减弱大跨度效应,降低施工安全风险,但存在机械化施工作业空间小、施工周期长等缺点。由于隧道在开挖中实际围岩等级要好于Ⅴ级,在原双侧壁导坑法施工方案的基础上进行了优化分析,由常规的左中右导坑开挖顺序,改为左上、右上、中上——左下、右下、中下的开挖方案。采用GEO5有限元软件进行模拟,比较两种施工方案下的围岩应力、支护结构弯矩以及地表沉降。计算及监测结果表明,优化后的施工方案是安全可靠的,同时又可以增大机械化施工作业空间,简化工序管理难度以提高工效。

The Double-Side-Pilot-Excavation is a popular method in the tunnel excavation since it is suitable for the excavations in the Class V（worst）rock mass and it can also reduce the effect of large span in the tunnel dimensions.However,it has the disadvantages of constrained work space and long construction periods.Consider the fact that the rock mass in the project was actually better than the Class V,the optimization of the conventional Double-Side-Excavation was possible.The excavation sequence of the conventional method of left,middle and right was changed to upper left,upper right,upper middle and then,lower left,lower right and lower middle.The improved procedure was numerically modeled using GEO5 finite element software and the results were compared with the conventional procedure in terms of stress in the surrounding rock mass,bending moment in the supporting structures and the subsidence of the ground surface.The comparison results indicate that the optimized procedure is safe a reliable and further,the headroom for the construction was also able to be increased and therefore,the efficiency could be improved.