地震效应和坡顶超载对均质土坡稳定性影响的拟静力分析

Quasi-static stability analysis of homogeneous soil slopes under effect of surcharge and earthquake

基于强度折减技术和极限分析上限定理,假定机动容许的速度场破坏面,考虑坡顶超载、水平和竖向地震效应影响推导了边坡稳定性安全系数的计算表达式。采用序列二次规划迭代方法(和内点迭代方法)对边坡安全系数目标函数进行能量耗散最小化意义上的优化计算,与多个算例的对比验证了其方法和程序计算的正确性;对影响土质边坡动态稳定性的一些因素进行了参数分析,分析表明:随着边坡倾角β、坡顶超载q、水平和竖向地震效应影响系数的增大,边坡稳定性安全系数显著下降;随着坡顶超载q、水平地震效应影响系数kh的增大、竖向地震效应影响系数kv的减小,边坡的潜在滑动面越来越深,潜在破坏范围越来越大。竖向地震效应对边坡稳定性也有一定影响,强震条件下的设计计算必须考虑竖向地震效应的影响。

The effects of surcharge and pseudo-static seismic forces on soil slopes were investigated by applying the kinematical approach of limit analysis theory and strength reduction technique. The rotational failure surface was considered and analytical expressions is derived to calculate the safety factor of slope subjected to surcharge and earthquake loading. The upper bound solutions for analytical expression are presented by applying iterative optimization method. From the comparative analysis, it can be seen that the solutions presented here agree well with available predictions both in simple static state and dynamic state. Parametric analysis shows that the safety factor of slopes decreases nonlinearly as the stability condition of a slope deteriorates when an increase in values of slope angle, surcharge and pseudo-static seismic forces occurs. From the numerical results, it also can be seen that latent slide surface moves inward to the slope with the increase of surcharge q and horizontal effect kh and the decrease of vertical effect kv, sliding surface and failure mass becomes bigger. The effect of vertical seismic acceleration on the stability of reinforcement slopes is significant especially for strong motion earthquake; i.e. that the effect of the vertical seismic acceleration should be taken into account in the engineering practices.