深埋水平岩层隧道开挖稳定性分析及控制

Stability analysis and control of tunnel excavation in deep buried horizontal stratum

针对深埋高地应力水平岩层掌子面开挖稳定性及支护结构失效问题,以大峡谷隧道为工程背景,通过现场测试、室内试验、数值模拟等方法,探究深埋高地应力水平岩层失稳机理及控制措施。研究结果表明:坚硬岩体被节理面切割后,在高地应力作用下容易发生挤压破碎,破碎岩体遇水发生软化,导致掌子面发生大范围塌方,初支和超前支护失效;隧道开挖后岩层发生不均匀沉降,浅部岩层最先发生弯折破坏,层内块体错动滑移,继而向上方岩层发展,并伴随层间分离和层内裂隙发育,最终形成宏观破裂面;提出的台阶法、2 m开挖进尺、砼喷层、双层小导管、提高初支强度的整体优化控制措施,可有效提高现场支护效果。

Aiming at the problems of excavation stability of tunnel face and the failure of supporting structure in deep buried horizontal stratum with high ground stress,based on the engineering background of Daxiagu tunnel,the instability mechanism and control measures of the deep buried horizontal stratum with high ground stress were studied through the field test,laboratory test and numerical simulation methods.The results showed that the hard rock mass cut by the joint plane was prone to occur crushing and breaking under high ground stress,the broken rock mass softened by water led to the large-scale collapse of tunnel face and the failure of primary support and advanced support.After the tunnel excavation,the uneven settlement of stratum occurred,then the shallow stratum suffered tensile and bending failure in the first.The block mass in stratum slipped with dislocation,then developed to the upper stratum,accompanied by interlayer separating and fracture development in stratum,and finally formed a macroscopic fracture plane.The proposed integrated optimization control measures of step method,2 m excavation footage,concrete spray layer,double-layered small pipes and improving primary support strength obtained good on-site support effect.