Study and prediction method development of the progressive failure of embankment and gentle slope caused by excess pore water pressure propagation

主震作用后充填体和缓坡破坏的递进迟滞破坏引起了人们的关注。例如，在2003年三陆-南地震和2003年宫城县-北部地震期间，沙质填充物斜坡像泥石流一样坍塌。很明显，孔隙水在破坏中起了重要作用，因为破坏的土壤含有大量的水，表现得像泥浆。在本研究中，我们试图明确这种破坏的破坏机制，并开发预测方法。认为振动产生的超孔隙水压力起重要作用，超孔隙水压力的传播是延迟破坏的原因。本文的研究结果总结如下：1。提出了一种基于不排水循环剪切试验评价非饱和砂土液化潜力的新思路，并进行了试验验证。研究结果阐明了非饱和土的液化机理。根据不排水循环剪切试验后的残余变形，发现剪切变形与土体的剪胀特性有关。这些结果适用于液化土残余变形的评价。在1964年新泻地震中，利用地质切片仪（Geoslicer）实地调查方法寻找了液化引起的流动破坏痕迹。对土路堤吸力和含水率的变化进行了两年的监测。根据数据，研究了其蒸发特性和保水特性。使用开发的动态响应分析代码进行了案例研究。

Progressive delay failure, in which fill and gentle slope fails after main earthquake motion, is being paid attention. For example, during the 2003 Sanriku-Minami earthquake and the 2003 Miyagi-ken Hokubu earthquake, sandy fill slopes failed like a mud flow. It was clear that pore water played important role in the failure, because failed soils contained much water and behaved like a mud. In this study, we have tried to make clear the failure mechanism of such a failure and to develop the prediction method. It was thought that excess pore water pressure generated by the vibration play an important role and the propagation of the excess pore water pressure is the cause of delayed failure. The results of this study are summarized as follows;1. We proposed a new idea to evaluate the liquefaction potential of unsaturated sandy soils based on the undrained cyclic shear test and it was confirmed experimentally. From the results, the liquefaction mechanism of unsaturated soils is clarified.2. Based on the residual deformation after undrained cyclic shear test, it was found that the shear deformation was related to the dilatancy characteristics of soil. These results are applicable to the evaluation of residual deformation of liquefied soil.3. Field investigation method called Geoslicer was used to find the trace of liquefaction induced flow failure during the 1964 Niigata earthquake.4. Change of the suction and water content of earth embankment were monitored for two years. From the data, the evaporation and the water retention characteristics were studied.5. Case study was conducted using the dynamic response analysis code developed.