高地应力软岩隧道快速施工围岩稳定性分析

Stability Analysis of Surrounding Rock in High-geostress Soft Rock Tunnels under Rapid Construction

研究长进尺快速施工下高地应力软岩隧道围岩的稳定性对保障施工安全、提升施工效率意义重大。首先以掌子面滑移失稳模式讨论围岩失稳问题,采用极限分析上限法,利用耗散功率与外力功率间的关系分析不同地质环境、开挖参数对围岩稳定性的影响;而后,以软弱围岩松散破碎失稳模式讨论围岩失稳问题,采用围岩整体安全系数法揭示高地应力软岩隧道围岩的稳定性演变机理;最后总结提炼出复合两种失稳模式的高地应力软岩隧道围岩稳定性判定基准。研究表明:极限分析上限法不仅可用于评价掌子面稳定性,还可用于求解推断掌子面的失稳形迹;岩体黏聚力与内摩擦角对稳定性具有重要影响,但随着二者的增大掌子面稳定系数并非线性增加,增长速率逐渐放缓;掌子面安全系数随开挖进尺、台阶高度增加呈非线性变化,可根据变化曲率确定最优开挖参数;提出高地应力软岩隧道快速施工下围岩稳定性评价方法,即逐次判定隧道是否发生静态滑移失稳和动态松散破碎失稳。

Studying the stability of surrounding rock in high-geostress soft rock tunnels under rapid construction with long excavation round length is of great significance for ensuring construction safety and improving construction efficiency.Firstly,the sliding instability mode of the working face is discussed to analyze the instability problem of the surrounding rock using the upper bound limit analysis method.The relationship between dissipated power and external force power is used to analyze the influence of different geological environments and excavation parameters on the stability of the surrounding rock.Secondly,the instability of the surrounding rock is disscussed using the loosening and fractured instability mode of weak surrounding rock,the evolution mechanism of the stability of surrounding rock in high-geostress soft rock tunnels is revealed using the overall safety factor method for surrounding rock.Finally,a comprehensive criterion for determining the stability of surrounding rock in high-geostress soft rock tunnels,which combines these two instability modes,is summarized and refined.The research shows that the upper bound limit analysis method can not only be used to evaluate the stability of the working face but also to infer the instability trajectory of the working face.The cohesion and internal friction angle of the rock mass have a significant influence on stability,but as they increase,the stability coefficient of the sidewall does not increase linearly,and the growth rate gradually slows down.The safety factor of the working face varies nonlinearly with the excavation round length and bench height,and the optimal excavation parameters can be determined based on the change in curvature.A method for evaluating the stability of surrounding rock in high-geostress soft rock tunnels under rapid construction is proposed,which sequentially determines whether the tunnel undergoes static sliding instability and dynamic loosening and fractured instability.