主应力对洞室围岩失稳破坏行为的影响研究

 针对复杂应力环境三向应力状态下地下洞室围岩破坏条件和破裂机制，采用统计损伤理论和数值模拟方法，建立三维非均匀性地质模型，考虑应力的三维效应，引入强度折减法，一方面在保持模型边界条件的同时实现洞室围岩的逐步破坏，另一方面以此定量评价不同应力场中洞室安全稳定状况，探讨不同侧压力系数和轴向应力条件下洞室围岩破坏模式，探究中间主应力对洞室稳定性的影响以及深部岩体分区破裂化现象产生条件和破裂规律等。结果表明，侧压力系数影响洞室围岩初始破裂形成部位和发展趋势；不同的轴向应力使得洞室围岩破裂区域和范围显著不同，在不同的侧压力系数条件下，轴向应力影响洞室稳定的规律存在差异；不同方向中间主应力对洞室围岩安全稳定状况的影响是不同的；当洞室轴线方向与最大水平应力方向平行时，较大的轴向应力会使洞室围岩产生分区破裂化现象，围岩破坏的区域也是拉应变集中的区域等。这些结果对进一步揭示地下洞室围岩非线性变形破坏行为，评价岩土工程安全稳定性，采取合理的支护措施等均具有重要意义。

INFLUENCE OF PRINCIPAL STRESSES ON FAILURE BEHAVIOR OF UNDERGROUND OPENINGS

A statistical damage numerical model was employed to investigate the fracture mechanism of underground openings under triaxial stress state. A three-dimensional tunnel model was established by considering rock heterogeneity described by Weibull distribution. The strength reduction method was introduced into the numerical model to achieve progressive failure of surround rock mass by decreased rock strength gradually. The fracture patterns and safety factors of the underground openings in different stress fields were also obtained quantitatively. Failure patterns under different lateral pressure ratios and axial stresses were analyzed by varying the lateral pressure ratios of the maximum principal stress to the minimum principal stress. The influence of intermediate principal stress on the opening stability, and the stress condition of zonal disintegration phenomena were discussed. The results showed that the failure behavior of the surrounding rock mass was complicated due to the various triaxial stress states. Both lateral pressure ratio and axial stress had significant influences on the tunnel failure patterns. When the direction of tunnel axis is parallel to the maximum principal stress，the zonal disintegration of underground openings appeared because of large axial stress，and the ruptured zone resulted in tensile strain concentration. The numerical model can obtain the fracture patterns and evaluate the tunnel stability，which will be much helpful for revealing nonlinear deformation and failure behavior of rock tunnels in tunnelling engineering.