Predicting system of Shirasu slope failure in southern Kyushu

本研究旨在预测九州岛南部降雨引起的边坡破坏的地点、时间和规模。本研究项目主要分为三个部分，即：(1)现场和室内试验，明确降雨引起边坡失稳的内在原因；(2)现场测量系统，获取与降雨诱发原因相关的土壤降雨、吸力和温度信息；(3)数值模型，模拟边坡含水量状况。利用定量理论，应用遥感技术识别边坡破坏危险区。采用X射线反射法对风化过程进行了研究。火山碎屑流沉积物的化学分析明确了鹿儿岛湾附近火山喷发和沉积物的顺序。通过对白苏坡面土壤降水、吸力和温度的实测，明确了白苏坡面降雨入渗和孔隙水蒸发的过程。通过数值模拟试验，模拟了边坡的含水率变化情况，验证了所建立的数值模型的有效性。

This research aims to predict the place time and scale of slope failures due to rainfall in the southern part of Kyushu Island. The research project is mainly divided into three parts, i.e., (1) the in-situ and laboratory tests to make clear the inherent causes of slope failure due to rainfall, (2) field measuring system to acquire the information of rainfall, suction and temperature in soil that relate to the induced causes due to rainfall, and (3) numerical models to simulate the slope condition concerning the water content.To identify the dangerous places of slope failure the remote sensing technology was applied with the quantitative theories. The X ray reflection method was used to investigate the weathering process. The chemical analysis of pyroclastic flow deposits made clear the order of eruptions and sediments around Kagoshima Bay area.The field measurement of rainfall, suction and temperature in soil made clear the process of infiltration of rain and evaporation of pore water on Shirasu slope.The numerical experiments were carried out to simulate the condition of slope concerning the water content and proved the validity of numerical models which developed for this research.