基于弹性地基梁理论的跨活断层隧道围岩-衬砌体系破坏机制研究

Study on the Failure Mechanism of Surrounding Rock-lining System of a Cross Active Fault Tunnel Based on Elastic Foundation Beam Theory

随着我国西部高烈度地区的隧道工程建设的持续深入发展,长大隧道将不可避免地穿越复杂不良地质区域,接近或跨越活动断裂带,面临严重的错断威胁。将温克尔弹性地基梁理论引入跨活断层隧道抗错断问题的研究中,从几何学和理论力学等角度,将隧道简化为作用在地层上的弹性地基梁;采用法向弹簧与切向弹簧模拟地层与结构的相互作用,并利用有限元数值模拟手段,建立跨活断层隧道围岩-衬砌体系数值模型。基于数值模型,探索了断层错动条件下围岩-衬砌体系位移变化规律,研究了跨断层隧道力学响应特征,同时,深入分析了断层破碎带关键参数对围岩-衬砌体系错断响应的影响。研究结果表明:断层两盘错动影响范围主要集中在断层错动面两侧各30 m的范围内;在中心剪切带处,围岩上下两盘位移连续;衬砌在断层上下盘内受到相反的弯矩作用,在断层破碎带内隧道以受压为主,而在远离断层带处主要呈受拉状态。此外,不同的断层倾角、破碎带宽度、岩体质量等级均对围岩-衬砌体系错断响应有一定影响,跨断层隧道穿越活断层的最佳角度为正交;断层破碎带宽度较大的情况易避免衬砌发生应力集中的现象;断层破碎带岩体质量等级越高,隧道受到断层错动作用越显著。该研究成果可为跨断层隧道抗错断设计提供一定的参考与理论支持。

With the construction of tunnels in high intensity areas in Western China has been developing continuously and deeply,for the long tunnel,it is inevitable to cross the complex unfavorable geological area,close to or cross the active fault zone,and the tunnel structure is seriously threatened by dislocation.In this paper,Winkler's elastic foundation beam theory was introduced into the study of the anti-dislocation problem in a tunnel crossing active faults.From the perspective of geometry and theoretical mechanics,the tunnel is simplified as an elastic foundation beam acting on the stratum.The interaction between stratum and structure is simulated by normal spring and tangential spring,and the numerical model of surrounding rock-lining system of tunnel across active fault is established by means of finite element numerical simulation.Based on the numerical model,the displacement variation law of the surrounding rock-lining system under the fault dislocation was explored,the mechanical response characteristics of cross fault tunnels were studied.Meanwhile,the influence of key parameters of fracture zone on the fault response of surrounding rock-lining system was analyzed.The research results show that the range affected by the fault dislocation is mainly concentrated within 30 m on both sides of the fault plane.The displacement between the hanging wall and footwall of the surrounding rock is continuous in the shear zone.The lining is subject to the opposite bending moment in the hanging wall and footwall.And the tunnel is mainly under pressure in the fracture zone,while it is mainly under tension away from the fracture zone.In addition,different fault dip angle,the width of fracture zone and the rock mass quality grades all have a certain impact on the fault response of surrounding rock-lining system.The optimal angle for a tunnel crossing an active fault is orthogonal.It is easy to avoid the phenomenon of stress concentration in the lining when the width of the fracture zone is large.And the higher the rock mass quality in fracture zone is,the more obvious the influence of fault dislocation on tunnel.The research results can provide a certain reference for the anti-dislocation design of cross active fault tunnels.