施工通道与站台隧道三岔口段施工方法及力学行为研究

Research on construction method and dynamic mechanical behavior of three-fork section of construction passage and station tunnel

针对软弱围岩双线地铁车站隧道横通道与主线隧道开挖断面差距大,交叉区域围岩受多次扰动易出现应力集中,隧道三岔口段施工风险较大,易出现安全事故等问题,以青秀山地铁车站为依托,利用MIDAS-GTS对隧道连接处施工方法及受力特征进行模拟分析。着重对比大包法和小包法施工引起的围岩位移、应力分布及塑性区范围,并进一步对小包法施工全过程进行动态力学行为研究。研究结果表明:小包法所引起的围岩位移、重分布应力、塑性区范围均小于大包法,且施工工期相比大包法更短;小包法施工过程对围岩影响主要位于三岔口隧道交叉处,拱顶部分区域出现拉应力,拱脚处压应力集中,且施工过程中围岩应力体系转换频繁,选取合适的支护方法可有效控制围岩变形。

For the double-track subway station with weak surrounding rock,there is a large gap between the cross passage and the main line tunnel,the surrounding rock at the intersection of tunnel is prone to stress concentration due to frequent disturbances,and the construction risk of the three fork section of the tunnel is large,which is prone to safety accidents and other problems.By taking the Qingxiushan subway station as the engineering background,the construction method and force characteristics of tunnel junctions were analyzed by using MIDAS-GTS finite element analysis software.By emphasizing the importance to contrast the surrounding rock displacement,stress distribution and plastic zone range caused by the construction of the full and part-envelope construction method,furthermore,the dynamic mechanical behavior of the whole construction process was studied using part-envelope construction method.Research results indicate:The surrounding rock displacement,redistribution stress and stress caused by the part-envelope construction method are smaller than the full-envelope construction method,and the construction period is shorter;The impact of the part-envelope construction method on the surrounding rock is mainly located at the three-fork section tunnel.Tensile stress appears in the part of arch crown,and compressive stress is concentrated at the arch foot.In addition,the surrounding rock stress system changes frequently during the tunnel construction process.Selecting a suitable support method can effectively control the development of the surrounding rock deformation.