Research on hazard assessment and mitigation measures of landslides induced by large-scale earthquakes on cut and filled slopes in densely-populated residential areas in big cities

在东京大都会日野市人口密集区的试验场地，对安装在钻孔中的三分量地震仪和孔隙水压力计进行了监测。特别是孔隙水压力的上、下分量的动力响应与远距离大震有很高的相关性。钻孔取芯土样的环剪试验结果表明，在地震作用下，地下水位较浅的填谷饱和土容易产生超静孔压。这意味着这些被填满的山谷地面很容易在即将到来的东京大地震下发生快速滑坡。2004年新泻中地震震中地区组织了现场调查，引发了许多滑坡。其中，东竹泽滑坡在缓坡上表现出快速而长的径流运动，并通过填充主要河流形成滑坡坝， ...更多信息 使用重新激活的山体滑坡很少迅速蔓延。在不排水条件下，利用附近监测到的真实的地震加速度，对暴露滑动面上的土样进行环剪试验。剪切位移加速和超静孔隙水压力的产生，可以解释其快速运动的机理。此外，对菲律宾莱特岛2月发生的造成千余人死亡的山体滑坡进行了实地调查。通过对现场采集的土样进行环剪试验，证明了滑坡发生前5天的强降雨引起的地下水上升，以及滑坡发生前的小地震都可能引发滑坡。在日野市及其附近的八王子市的试验场，应用了Sassa开发的岩土滑坡运动模拟。利用环剪试验获得的动力学特征参数和机载激光扫描仪获得的高分辨率地形数据，对东竹泽滑坡进行了研究。东竹泽滑坡的计算结果与实际滑坡流出区吻合较好。根据测得的土壤特性和计算机模拟结果，对日野市和八王子市两个试验场的这些值进行了滑坡溢出区（即危险区）评估。少

Three component seismometers and pore water pressure meters were monitored which were installed in the boreholes in the test site of densely-populated area of Hino city of Tokyo metropolis. Especially dynamic response of up-down component of the pore water pressure showed high correlation with remote large-scale earthquake. Ring shear tests of the soil samples obtained from the core samples of boreholes showed that saturated soils of filled valley with shallow ground water table is susceptible to generation of excess pore pressure at seismic condition. It means that those filled valley grounds are vulnerable to rapid landslides at the upcoming large earthquakes beneath the Tokyo metropolitan area.Field investigation was organized to the 2004 Mid-Niigata Earthquake epicenter area where numerous landslides were induced. Among them, Higashi-Takezawa landslide which showed rapid and long runout movement on a gentle slope and formed a landslide-dam by filling a major river, was focused beca … More use reactivated landslides rarely ran rapidly. Soil samples were taken from the exposed sliding surface and ring shear tests were conducted under undrained condition and by applying real seismic acceleration monitored nearby. Big excess pore water pressure generation and accelerating shear displacement were observed, which could explain its rapid motion mechanism. In addition, field investigation of the landslide in Leyte Island of Philippine which occurred in February and killed more than thousand people. Ring shear tests on soil samples obtained in the field proved that the landslide could be induced not only the ground water rise due to heavy rainfall of 5 days prior to the slide, but also triggered by a small earthquake which occurs just before the initiation of the landslide movement.Geotechnical landslide movement simulation which was developed by Sassa, was applied to the test sites in Hino-city and its adjacent Hachioji-city, as well as Higashi-Takezawa landslide site using dynamic characteristics parameters obtained by the ring shear tests as well as high-resolution topographic data obtained by airborne laser scanner. Results on Higashi-Takezawa landslide matches well the actual landslide runout area. Assessment of landslide runout areas, namely the hazardous areas were identified based on the measured soil characteristics and computer simulation using those values for the two test sites of Hino-city and Hachioji-city by the simulation output. Less