高应力软岩隧道二次衬砌合理支护时机分析研究

NUMERICAL ANALYSIS OF REASONABLE SUPPORT TIMING FOR SECONDARY LINING OF HIGH STRESS SOFT ROCK TUNNEL

以兰渝铁路某隧道为研究对象,考虑炭质板岩地层的蠕变特性,基于广义西元模型,对隧道施工过程进行三维数值模拟,研究了不同支护时机下初期支护、二次衬砌的受力变形规律。研究结果表明:(1)提前施作二次衬砌,能够和初期支护构成叠合支护体系,有效约束软岩变形,减小变形速率,施作时间越早,围岩变形控制效果越好;(2)初期支护和二次衬砌的应力支护时机相关。二次衬砌施作时间越早,越能够改善初期支护的受力状态,减小初期支护应力,同时分担的围岩形变压力越大,二次衬砌应力越大。

Taking a tunnel on the Lanzhou to Chongqing railway as the research object,considering the creep characteristics of carbonaceous shale formations,conduct three-dimensional numerical simulation of the tunnel construction process by using the generalized Nishihara model.Studied the deformation law of initial support and secondary lining under different support timing.The results show that:(1)Pre construction of secondary lining can form a superimposed support system with initial support,effectively restraining soft rock deformation and reducing deformation rate.The earlier the construction time,the better the control effect of surrounding rock deformation.(2)The timing of stress support for initial support and secondary lining is related.The earlier the construction time of the secondary lining,the better the stress state of the initial support,reduce the initial support stress,and share the greater deformation pressure of the surrounding rock,resulting in greater secondary lining stress.