含水率对昔格达地层大断面隧道初期支护安全性影响研究

摘要

昔格达地层具有水稳性差、易崩解等特点,常常引发隧道初期支护结构开裂、围岩掉块、坍塌冒顶等灾变事故.为了研究围岩含水率对昔格达地层大断面隧道初期支护安全性的影响规律并及时预防灾变事故,以成昆铁路复线桐梓林隧道为工程依托,通过数值模拟对比分析5种典型围岩含水率下隧道初期支护结构的受力特性和变形规律,根据相关规范规定的洞周变形标准和结构强度安全系数标准界定现有支护参数所能够维持的围岩含水率阈值为29％,并为超过此围岩含水率阈值的隧道支护参数提出优化方案.通过现场监控量测数据验证数值模拟计算结果的可靠性和合理性,研究成果不仅完善了昔格达地层大断面隧道设计参数,同时为类似工程提供借鉴和参考.%Catastrophic accidents such as initial support structure cracking,rock mass falling out,collapse and roof fall are often caused by insufficient water stability and collapse of Xigeda strata.In order to study the influence of moisture content on the safety of the initial support in Xigeda strata of the tunnel with large cross-section,the stress characteristics and deformation rules of initial supporting structure under five typical surrounding rock water content conditions are compared and analyzed by means of numerical simulation based on the Tongzilin tunnel.According to the deformation standard and safety factors of structural strength stipulated in relevant specifications,the threshold value of the water content of the surrounding rock mass is maintained at 29％.The tunnel support parameters are optimized while the threshold value of the surrounding rock moisture content is exceeded.The reliability and rationality of the numerical simulation results are verified by field monitoring.Research results not only improve the design parameters of the large cross-section tunnel in Xigeda strata,but also provide references for future similar projects.