Abstract Face support pressure is a crucial index to guarantee the stability at the earth pressure balance (EPB) shield tunnel face. Based on the limit equilibrium theory and the failure pattern observed in existing model tests, a novel three-dimensional failure mechanism is proposed to consider the evolution of failure pattern in dense sand stratum. The failure zone is divided into two parts: a failure slip zone and an upper loosen zone. The failure slip zone is formed by rotating a straight line and a logarithmic spiral, whilst the upper loosen zone is defined as a cone or a cylinder for different stage during the failure zone evolution process. The input parameters of the proposed mechanism are determined based on the results of existing model tests, where the inclination angle of the slip surface α varies from 51° + 0.5φ (φ is the internal friction angle) to 53° + 0.5φ, and the height coefficient of the logarithmic spiral is λ = 0.3. The proposed solution can provide reasonable calculations compared with experimental measurements and numerical simulations, suggesting the efficacy of the method for use in design.

中文翻译：

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考虑破坏模式演化的密砂地层EPB盾构隧道工作面稳定性分析

摘要 工作面支护压力是保证土压平衡（EPB）盾构掌子面稳定性的重要指标。基于极限平衡理论和现有模型试验中观察到的破坏模式，提出了一种新的三维破坏机制，以考虑致密砂层破坏模式的演变。破坏区分为两个部分：破坏滑动区和上部松动区。破坏滑动带由直线和对数螺线旋转形成，而上部松动带定义为破坏带演化过程中不同阶段的锥体或圆柱体。所提出机构的输入参数是根据现有模型试验的结果确定的，其中滑动面的倾角 α 从 51° + 0 变化。5φ（φ为内摩擦角）到53°+0.5φ，对数螺线的高度系数λ=0.3。与实验测量和数值模拟相比，所提出的解决方案可以提供合理的计算，表明该方法用于设计的有效性。