Study on shear strength property of re-slide type landslide and failure mechanism

为研究滑坡的力学行为，进行了恒定偏应力作用下粘土的孔压加载试验。通过对土样的观测，得到了两个变形的孔压门槛值。一个是屈服点，另一个是故障点。通过与实验结果的比较，表明次加载面模式的本构方程能较好地表达这些阈值大小。模拟研究了孔压荷载重复次数门槛值的变化规律。针对孔压反复荷载，绘制了破坏点的破坏包络线，表达了重复荷载作用下状态变量的变化过程。对得到的失效包络线进行了实验验证。证明了失效包络线的存在，但观察到了模拟与实验的差异。指出了SOI…的渐进式失败。更多的L标本在实验中。试件中单元性质的丧失是实验研究理想破坏应力的一个重要问题。详细的讨论留待以后的问题再讨论。土样在孔压荷载作用下的时变行为是由于土体的渐进破坏而形成的。从土力学角度分析认为，滑坡的缓慢破坏是渐进破坏的结果。在实验中还测量了所谓的二次蠕变行为。这一现象可以从土-水耦合的概念来解释。在孔压加载循环中，观察到两种相反的效应：一种是孔压升高引起的应变软化，另一种是孔压降低时的固结。两种相反作用的平衡对粘土在重复荷载作用下的强度有较大影响。在本研究中，还发展了考虑预制滑移线的边坡稳定方法。采用刚塑性本构方程。较少

Pore water pressure loading test on clay under constant deviator stress was conducted to investigate the behavior of landslide. From the observation on soil specimen, two threshold magnitudes in pore water pressure for deformation were obtained. One was a yield point and the other was a failure point. It was shown that the constitutive equation of sub-loading surface mode could express these threshold magnitudes through the comparison with experiments. The change in threshold magnitudes for repeats of pore water pressure loading was investigated with simulation. The failure envelopment line was drawn for failure points against the repeats of pore water pressure loading, which expressed the change process of state variable for repeated loads. The obtained failure envelopment line was examined with experiments. The existence of failure envelopment line was proved, however, the discrepancy between simulation and experiment was observed. It was pointed out to the progressive failure of soi … More l specimen in experiment. The lost of element property in specimen was a serious problem to investigate the ideal failure stress in experiment. The detailed discussion was left to future problem. Time dependent behavior of soil specimen for pore water pressure loading was observed due to progressive failure. It suggested that the slow failure of landslide was due to progressive failure from the viewpoint of soil mechanics. The so-called second creep behavior was also measured in experiment. This phenomenon would be clarified from soil-water coupling concept. In pore water pressure loading cycle, two opposite effects were observed: one was a strain softening for increase in pore water pressure and the other was a consolidation for decrease in pore water pressure. The balance of two opposite effects much affected the soil strength of clay for repeated loads. In this study stability method for slope including the preformed slip line was also developed. Rigid plastic constitutive equation was employed. Less