滇西南地区软岩隧道大变形特征及控制措施研究

Large deformation characteristics and control measures of soft rock tunnels in southwest Yunnan region

为解决隧道穿越软弱围岩地带易发生大变形破坏的问题,以中老铁路玉磨段巴罗二号隧道工程为背景,通过理论分析结合有限元模拟的方法,分析了软岩隧道大变形段围岩和支护结构的力学特征。为了对围岩大变形进行控制,提出了长管棚超前支护结合排水和初支加固的综合措施。结果表明:在使用综合控制措施前,围岩变形较大,呈现出水平收敛大于拱顶沉降、左侧拱腰变形大于右侧拱腰的特点,且左侧拱腰承受水平应力较大,围岩塑性区范围较大,集中分布在拱腰和拱脚位置,围岩发生塑性破坏的可能性较大;在使用综合控制措施后,围岩竖向沉降和水平收敛分别减少44.87%和32.66%,并且隧道左侧拱腰初支水平应力及围岩塑性区范围显著减小,塑性应变最大值也显著降低。根据现场监测发现,采用综合控制措施后隧道围岩变形量均处于安全范围内,控制效果良好,能够为今后类似工程提供指导和借鉴。

In order to solve the problem of large deformation and damage in the weak surrounding rock zone during tunnel crossing,taking the Baluo No.2 Tunnel Project of the China-Laos Railway Yumo Section as the background,the mechanical characteristics of the surrounding rock and support structure in the large deformation section of the soft rock tunnel were analyzed through theoretical analysis combined with finite element simulation.A comprehensive measure of advanced support combining long pipe shed,drainage,and initial support reinforcement was proposed to control the large deformation of the surrounding rock.The results show that before using the comprehensive control measures,the surrounding rock deformation is large,showing the characteristics of horizontal convergence greater than the crown settlement,and the deformation of the left arch waist greater than that of the right arch waist,and the left arch waist bears greater horizontal stress.The plastic zone of the surrounding rock is large,concentrated in the arch waist and arch foot positions,and there is a high possibility of plastic failure of the surrounding rock.After using the comprehensive control measures,the vertical settlement and horizontal convergence of the surrounding rock reduced by 44.87%and 32.66%respectively,and the initial support horizontal stress of the left arch waist and the plastic zone of the surrounding rock are significantly reduced,and the maximum plastic strain is also significantly reduced.According to the field monitoring,the deformation of the tunnel surrounding rock is within the safe range after adopting the comprehensive control measures,and the control effect is good,which can provide guidance and reference for similar projects in the future.