Stability Analysis of Surrounding Rock in High-geostress Soft Rock Tunnels under Rapid Construction
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.
High geostressSoft rock tunnelRapid constructionStability analysis
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