基于环向失稳的浅埋盾构隧道极限支护压力分析

Analysis of Limit Support Pressure on Shallow Shield Tunnel Based on Circumferential Instability

基于数值模拟和理论分析,从环向角度对浅埋盾构隧道开挖面稳定性及极限支护压力进行了研究。通过弹塑性有限元数值模拟,获得了开挖面支护力与变形的关系和最终破坏模式,发现破坏模式主要受内摩擦角和埋深比影响较大,而受黏聚力影响较小。根据得到的破坏模式,建立了一种基于单参数变量的极限平衡模型,通过优化分析得到最危险破坏面和极限支护力。将极限支护力表示为黏聚力、上覆荷载、土体重度与其影响系数乘积的叠加形式进行了分析,其呈现为随内摩擦角、埋深比、侧向支护压力比增大非线性减小、随黏聚力增大近似呈线性减小的规律。通过与数值模拟和离心试验结果对比,验证了所建模型计算极限支护力的合理性。

Based on numerical simulation and theoretical analysis,the stability of shield tunnel face and limit support pressure of shallow shield tunnel are studied from the perspective of circumferential direction.Based on elasto-plastic finite element numerical simulation,the relationship between tunnel support pressure and deformation and the ultimate failure mode are obtained.The results show that the failure mode is mainly affected by friction angle of soil and buried depth ratio of tunnel,but less by cohesion.Based on the failure mode,a limit equilibrium model based on single parameter variable is established.The most dangerous failure surface and ultimate support force are obtained through optimization analysis.The limit support pressure is expressed as the superposition of cohesion,overlying load,soil weight and their influence coefficients.The obtained limit support pressure decreases nonlinearly with the increase of friction angle,buried depth ratio and lateral support pressure ratio,but decreases approximately linearly with the increase of cohesion.Compared with the numerical results and centrifuge mode test,the rationality of the model for calculating the limit support pressure is verified.