破碎岩体隧道塌方预测及台阶工法调整技术研究

塌方是破碎岩体隧道较易发生的工程事故,主要发生在掌子面和未支护段,塌方预测及工法适时调整是避免事故发生的有效途径。依托某塌方隧道工程,提出塌方预测及台阶工法调整流程:首先对未支护段进行塌方预测,采用拱顶岩体稳定理论评估上台阶高度,确定极限矢跨比,并采用数值计算进行验证,选择合理的台阶数目;其次对掌子面稳定性进行评估,基于地质素描对掌子面稳定性进行塌方初判,采用数值计算对掌子面稳定性进行二次评估。鉴于核心土对掌子面稳定的重要作用,对台阶施工预留核心土工法的必要性也进行了分析。最终提出了基于拱顶岩体稳定理论的塌方预测和上台阶极限矢跨比计算方法,以及基于地质素描与数值计算的掌子面稳定性分析方法,相关研究思路可为类似工程提供借鉴和参考。

Collapsing prediction of broken rocky tunnel and adjustment of step excavation method

Tunnel collapsing is a common engineering accident in broken rocky tunnel excavation, which mainly occurred in the working face of tunnel and rock section without supporting. Timely construction method adjustment and advanced collapsing prediction are the effective methods to avoid the accidents. With a collapsing tunnel as the case, the process of collapsing prediction and adjustment of construction method are proposed. Firstly, the collapsing prediction needs to be carried out against rock section without supporting. The upper step height can be assessed by arch rock stability theory and the span limit of tunnel can be determined. The analysis results can be verified by numerical calculation method, and then a reasonable step number can be selected. Secondly, the initial prediction of tunnel working face should be carried out based on geological sketch and numerical calculation are used to carry out secondary assessment. In the light of the important influence of core soil on the stability of tunnel working face, the necessity of method of reserved core soil in step excavation is analyzed. The collapsing prediction and upper step limit vector calculation method based on arch rock stability theory, and the working face stability analysis method based on geological sketch and numerical calculation are proposed.