EXPLICATION OF PROGRESS FAILURE IN SLOPE STABILITY AND ITS ANALYSIS WITH STRAIN-SOFTENING CONSTITUTIVE EQUATION

由软岩或过固结粘土构成的边坡破坏可以认为是渐进式破坏的结果，即边坡内部局部点的应力分布不均匀导致局部破坏，并逐渐向边坡的其他部位扩散。我们试图获得一个解析模型，用它来模拟边坡破坏作为一个渐进的破坏现象。在研究的第一步，我们通过三轴试验等实验研究了软岩和超固结粘土的时效特性，以及物理化学裂隙特性对其应变硬化-软化特性的影响。在实验结果的基础上，对首席研究员等提出的硬化-软化型本构方程进行了扩展，使其既能表达随时间变化的行为，又能表达物理化学断裂行为。第二步，将扩展本构方程应用于边坡破坏现象，讨论了边值问题，并建立了边坡破坏现象的解析模型。用几种方法模拟了一些边坡破坏模型，得出了最优的模拟方法来表达渐进式破坏现象。第三步，利用离心机进行模型实验。在实验中，虽然对开挖边坡和天然边坡的递进破坏现象都进行了尝试，试图在离心力场中再现递进破坏现象，但到目前为止，还没有得到结论性的结果。为了将研究成果应用于边坡的合理设计、施工和维护，以及边坡破坏的预测，将进行持续的研究。

The slope failure, composed by the soft rock or over-consolidated clay, can be considered to be induced as the results of the progressive failure in which the local failure is generated by non-homogeneous distribution of stress at a local point inside the slope at the start, and it progressively propagates to other parts in the slope. We tried to obtain an analytical model with which the slope failure can be simulated as a progressive failure phenomenon.At the first step of the research, we investigated the time-dependent behavior of soft rock and over-consolidated clay and the effects of physicochemical fissure behavior to the strain-hardening-softening behavior through some experiments such as the triaxial tests. The hardening-softening type of the constitutive equation, which had been proposed by the head investigator, et al., was extended, on the base of the experimental results, to be able to express both the time-dependent behavior and the physicochemical fissure behavior.At the second step, the boundary value problem was discussed by applying the extended constitutive equation to the slope failure phenomenon and creating the analytical model for it. Some model cases of the slope failure were simulated by a few methods and the optimum simulating method was obtained to express the progressive failure phenomenon.At the third step, the model experiments were carried out by using centrifuge. In the experiments, though the progressive failure phenomenon of both the excavated and natural slope was tried to reproduce the progress failure in a centrifuge force field, the conclusive results have not been obtained yet until the current stage.The continuous research will be carried out to apply the results of the research not only to the rational design, construction and maintenance of slopes but also to the prediction of the slope failure.