主应力方向对软岩隧道稳定性影响的试验研究

为探明高地应力场主应力方向对软岩隧道围岩稳定性的影响规律，采用自主研发的"隧道三维应力场模拟试验系统"开展了大型三维地质力学模型试验，研究了最大水平主应力与隧道轴线平行和垂直两种工况下软岩隧道的围岩稳定性.研究结果表明:最大水平主应力与隧道轴线平行时，拱顶沉降和拱脚收敛的最终值分别为-0.221 m和-0.454 m，拱顶、左拱脚、右拱脚和仰拱处的围岩压力分别为0.478、0.361、0.416 MPa和0.261 MPa；最大水平主应力与隧道轴线垂直时，拱顶沉降和拱脚收敛的最终值分别为-0.309 m和-0.548 m，拱顶、左拱脚、右拱脚和仰拱处的围岩压力分别为0.579、0.652、0.593 MPa和0.327 MPa；两种工况下，围岩压力的最小值均出现在仰拱处、最大值均出现在墙脚处，围岩的径向应变增量均为拉应变增量，切向应变增量均为压应变增量，说明隧道开挖导致洞周围岩径向应力减小、切向应力集中. 

Test on the Stability of Soft Rock Tunnel with High Ground Stress Field Influenced by Direction of Maximum Horizontal Principle Stress

In order to study the influence of the principal stress in a high ground stress field on the stability of surrounding rock in soft rock tunnels, a completely self-developed test system "3D geotechnical model test system for tunnels" was used to conduct the large-scale three-dimensional geological mechanics model test. In this research, the stability of surrounding rock in soft rock tunnels under two conditions, when the maximum horizontal principal stress is parallel and perpendicular to the tunnel axis, was investigated. The results show that when the maximum horizontal principal stress is parallel to the tunnel axis, the final values of vault settlement and horizontal convergence of the arch foot are -0.221 and -0.454 m, respectively; and the values of surrounding rock pressure at the vault, left arch foot, right arch foot, and invert are 0.478, 0.361, 0.416, and 0.261 MPa, respectively. When the maximum horizontal principal stress is perpendicular to the tunnel axis, the final values of the vault settlement and horizontal convergence of the arch foot are -0.309 and -0.548 m, respectively; and the values of surrounding rock pressure at the vault, left arch foot, right arch foot, and invert are 0.579, 0.652, 0.593, and 0.327 MPa, respectively. In both cases, the minimum values of the surrounding rock pressure are observed at the invert while the maximum values of the surrounding rock pressure are observed at the wall foot; the radial strain increment in surrounding rock is tensile, and tangential strain increment is compressive, indicating that the excavation of the tunnel leads to a decrease in radial stress and an increase of tangential stress.