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为了研究管棚预支护对隧道开挖面稳定性的影响,从塑性极限分析机动学方法出发,利用土的强度折减系数概念,建立了管棚预支护条件下隧道开挖面三维稳定性分析模型,由此确定开挖面稳定系数及其相应的潜在破坏模式。结合实际工程,采用该方法计算得到的开挖面极限支护压力与有限元强度折减法的计算结果吻合较好,验证了本文方法的合理性。进而研究了隧道埋深、隧道洞径及围岩条件对开挖面稳定性的影响,分析了上述因素与开挖面极限支护压力及稳定系数的关系。对有无管棚预支护隧道开挖面稳定性分析表明:在软弱地层、大跨洞径等条件下,管棚预支护能有效提高开挖面稳定性。
In order to study the influence of pipe roof pre-support on the stability of tunnel excavation face, based on the plasticity limit analysis method, the 3D stability analysis of tunnel excavation face under the condition of pre-supporting pipe shed is established by using the concept of strength reduction coefficient of soil. Model, thereby determining the stability of excavation surface coefficient and its corresponding potential failure mode. Combined with the actual project, the calculated limit pressure of excavation surface calculated by this method is in good agreement with the calculated result of FEM strength reduction method, which proves the rationality of this method. The effects of tunnel depth, tunnel diameter and surrounding rock conditions on the stability of the excavation face are studied. The relationship between these factors and the pressure and stability factor of the limit excavation face is analyzed. The analysis of the stability of excavation face with or without prestored tunnel support shows that under the conditions of weak strata and large span of tunnel, pre-supporting of pipe shed can effectively improve the stability of the excavation face.