单节理深埋隧洞开挖瞬态卸荷响应机理数值模拟研究

Numerical Simulation of Transient Unloading Response Mechanism of Deep Tunnel Excavation with Single Joint

采用颗粒流数值模拟重现深埋单节理隧洞瞬态卸荷过程,从应力状态、变形特征、裂纹扩展等多角度探析节理特征对双江口水电站进厂交通洞瞬态卸荷效应的影响,研究表明:节理对深埋隧洞瞬态卸荷的应力调整过程有着重要的影响,应力集中区将由硐室底角、拱顶转移至节理尖端。随着节理长度的增加,节理尖端应力集中区域离自由面距离逐渐增大,围岩损伤区逐步向岩体深部发生迁移。不同节理角度下,微裂纹数目差异性显著,其中60°和30°节理围岩中的微裂纹数量较多;此外,压剪裂纹所占比例随着节理角度的增大呈现先增大后减小的变化趋势,45°时达最大。研究成果对水工隧洞开挖卸荷作用下围岩破坏机制认识和评价具有指导意义。

Using particle flow numerical simulation to reproduce the transient unloading process of a deep buried single joint tunnel,this study explores the influence of crack characteristics on the transient unloading effect of the access tunnel of Shuangjiangkou Hydropower Station from multiple perspectives such as stress state,deformation characteristics and crack propagation.The study shows that the cracks have an important impact on the stress adjustment process of transient unloading in deep buried tunnels,and the stress concentration area will be transferred from the bottom corner of the chamber and the arch to the tip of the crack.As the length of the crack increases,the distance between the stress concentration area at the crack tip and the free surface gradually increases,and the damage area of the surrounding rock gradually migrates towards the deeper part of the rock mass.There is a significant difference in the number of microcracks under different fracture angles,with more microcracks in the 60°and 30°fractured surrounding rock.In addition,the proportion of compression shear cracks shows a trend of first increasing and then decreasing with the increase of crack angle,and reaches its maximum value at 45°.The research results have guiding significance for understanding and evaluating the failure mechanism of surrounding rock under the unloading action of hydraulic tunnel excavation.