Support design method for deep soft-rock tunnels in non-hydrostatic high in-situ stress field

非对称高地应力环境下深埋软岩隧道支护设计方法

Due to the long-term plate tectonic movements in southwestern China,the in-situ stress field in deep formations is complex.When passing through deep soft-rock mass under non-hydrostatic high in-situ stress field,tunnels will suffer serious asymmetric deformation.There is no available support design method for tunnels under such a situation in existing studies to clarify the support time and support stiffness.This study first analyzed the mechanical behavior of tunnels in non-hydrostatic in-situ stress field and derived the theoretical equations of the ground squeezing curve(GSC)and ground loosening curve(GLC).Then,based on the convergence confinement theory,the support design method of deep soft-rock tunnels under non-hydrostatic high in-situ stress field was established considering both squeezing and loosening pressures.In addition,this method can provide the clear support time and support stiffness of the second layer of initial support.The proposed design method was applied to the Wanhe tunnel of the China-Laos railway in China.Monitoring data indicated that the optimal support scheme had a good effect on controlling the tunnel deformation in non-hydrostatic high in-situ stress field.Field applications showed that the secondary lining could be constructed properly.

受长期地质构造运动的影响,中国西南地区的深部地应力是复杂的。隧道穿越非对称高地应力环境下的岩层时,会发生严重的非对称挤压大变形。既有研究未涉及确定这类隧道支护时机和支护刚度的设计方法。本研究分析了非对称主应力环境下高地应力深埋软岩隧道开挖卸荷的力学响应,推导了形变压力特征曲线和松动压力特征曲线的解析解,进一步基于收敛约束理论,建立了非对称高地应力环境下考虑形变压力和松动压力的深埋软岩隧道支护设计方法,明确了第二层钢拱架的支护时机和支护参数。将研究提出的设计方法应用于玉磨铁路万和隧道,现场监测数据显示,采用本设计方法优化后支护方案对控制非对称高地应力环境下深埋软岩隧道的挤压变形有较好的效果,现场应用情况表明设计优化后隧道的二次衬砌可以正常施工。