基于上限理论的孔隙水压力作用下隧道洞口段含裂缝仰坡稳定性分析

研究了孔隙水压力作用下隧道洞口段含裂缝仰坡的稳定性。采用极限分析上限法，构建了坡顶含竖向裂缝的对数螺旋转动破坏机制，推导了可反映边坡临界坡高的稳定系数计算公式，将计算结果与未考虑孔隙水压力作用下的含裂缝边坡稳定性极限分析结果进行对比，验证了所提研究方法的合理性。通过算例分析，研究了坡顶裂缝最不利位置分布及仰坡整体安全系数。结果表明:坡顶裂缝开裂深度、土体内摩擦角、坡角越大及水位分布越浅，裂缝位置越靠近坡顶边缘处；孔隙水压力系数、坡顶裂缝开裂深度越大，仰坡稳定性系数越小；坡顶裂缝越深、孔隙水压力系数越大、边坡越陡，越不利于仰坡稳定；而坡内水位分布越低，越有利于仰坡稳定。

Upper Bound Analysis on the Stability of Cracked Slopes at Tunnel Entrance Subjected to Pore Water Pressure

The stability of the cracked slope at tunnel entrance subjected to pore water pressure was studied. The upper-bound limit analysis method and the logarithmic spiral rotation failure mechanism were adopted. A formula for calculating the stability coefficient reflecting the critical slope height was derived. The rationality of the proposed method was verified through comparison of the calculated results with those without effects of the pore water pressure. The distribution of the most critical crack position at the top of slope and the safety factor of the slope were studied by an example analysis. The results show that, the greater the crack depth is, the larger the internal friction angle and the slope angle will be, and the shallower the water level is, the closer the crack position will be to the edge of the slope. The greater the pore water pressure coefficient and the cracking depth are, the smaller the stability coefficient of the slope top will be. The deeper the crack is, the higher the pore water pressure coefficient and the steeper the slope will be, and the more unstable the slope will be. However, the lower the water level is, the more stable the slope will be.