地震作用下双层土裂缝边坡稳定性分析

Stability analysis of two-layered cracked slopes subjected to seismic excitation

裂缝常存在于边坡表面,地震作用会大幅降低裂缝边坡稳定性。针对双层土裂缝边坡稳定性问题,定义上下土层分界处高度与边坡高度之比为深度系数以描述双层土的分布,基于极限分析上限定理,构建“点到点”离散运动学机构,并在此机构中引入一条垂直张拉裂缝,结合拟静力法和强度折减法建立能量平衡方程求解裂缝边坡临界高度和安全系数上限解。计算结果与传统上限法进行对比,验证离散运动学机构的有效性及其解的优越性,同时探究土体非均质性及深度系数对裂缝边坡稳定性以及裂缝深度和位置的影响规律。结果表明,地震作用会降低边坡稳定性;随着地震力增大,边坡临界滑动面逐渐加深,裂缝深度略微增大,裂缝位置逐渐远离坡面;对于具体的双层土边坡会存在一个特定的深度系数使边坡安全系数达到最值,同时裂缝会穿越至下层土且深度发生突增。

Cracks,which often exist on the surface of slope,will greatly reduce the stability of cracked slopes under the action of earthquake.To solve the stability problem of the slope with cracks in two-layered soil,the ratio of the boundary height of upper and lower layers to the slope height was defined as the depth coefficient to describe the distribution of two-layer soil.The upper bound theorem of limit analysis was used to construct the"point-to-point"discrete kinematic mechanism,and a vertical tensile crack was introduced into the mechanism.The energy balance equation was established to solve the critical height and the upper bound solution of safety factor of a cracked slope by adopting the pseudo-static approach and the strength reduction method.The calculation results were compared with the results of traditional upper bound theorem to verify the effectiveness of the discrete kinematic mechanism and the superiority of the solution.Meanwhile,the influences of the soil heterogeneity and depth coefficient on the slope stability and the depth and location of cracks were explored.The results show that the slope stability will be reduced under the action of earthquake.With the increase in seismic force,the critical sliding surface of slope deepens gradually,the crack depth increases slightly,and the crack location is gradually away from the slope face.For a specific two-layered soil slope,there will be a specific depth factor to maximize the safety factor of the slope,and cracks will pass through the lower-layered soil and suddenly increase in depth.