气压辅助掘进盾构开挖面失稳机制及土拱效应三维物质点法研究

    Failure mechanism of tunnel face and soil arch effects in auxiliary air balanced shield using three-dimensional material point method

    • 摘要: 开挖面失稳坍塌是隧道施工安全的重大威胁,而厘清开挖面失稳破坏全过程演化机理是制定灾害防控与大变形处治措施的前提。采用三维物质点法对气压辅助掘进盾构开挖面失稳机制进行研究。对比盾构隧道开挖面稳定性模型试验与物质点模拟所得极限支护力、地表沉降以及地应力分布结果,验证物质点法模拟隧道开挖面失稳大变形的可行性。随后建立工程尺度气压辅助掘进盾构模型,探讨埋深、气压支护、刀盘开口型式对开挖面坍塌、地层变形响应及土拱动态演化的影响。研究结果表明:气压支护及刀盘可减缓坍塌速率与最终坍塌量,而较大埋深下早期坍塌速率更快;随着开挖面坍塌,地层协同变形并产生土拱,当土拱发育至地表附近并消散后,地表迅速发生塌陷。物质点法可动态捕捉气压辅助掘进盾构开挖面失稳破坏全过程特征,为类似工程灾后行为预测提供参考。

       

      Abstract: The collapse of tunnel face poses a serious threat to the safety of tunnel construction, and a comprehensive understanding of the entire evolutionary failure mechanism is the key premise for disaster prevention and treatment measures. By using the three-dimensional material point method (MPM), the large deformation behaviours of the collapse of tunnel face in the auxiliary air pressure balanced shield are investigated. The effectiveness of the MPM in analyzing the failure problems of tunnel face is validated by comparing the results of the limit support force, ground settlement and stress distribution with those of the experimental tests. Subsequently, a series of field-scale numerical simulations are conducted to explore the dynamic characteristics of collapse of tunnel face, response of ground deformation, and evolution of soil arch under various burial depths, support air pressures and cutter head types. The results demonstrate that the development rate and final mass of the collapse of tunnel face are reduced by the support of air pressure and cutter head, and a faster early collapse rate is observed in a deeper burial depth. The soil arch emerges with the ground deformation induced by the collapse of tunnel face, and the collapse of ground surface grows rapidly when the soil arch reaches the ground surface and vanishes. The MPM can effectively capture the entire dynamic process of the collapse of tunnel face in the auxiliary air pressure balanced shield, therefore providing valuable insights for preventing the collapse of tunnel face and predicting the post-failure behaviors in similar projects.

       

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