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Prediction of Failure Risk Level based on Weakness caused by Weathering and Evaluation of Resistance for Erosion on Shirasu Slope

Shirasu斜坡基于风化弱点的破坏风险等级预测及抗冲刷评价

基本信息

批准号：
04452228
负责人：
OCHIAI Hidetoshi
金额：
$ 3.97万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Shirasu widely distributed in southern Kyushu in Japan is weak in the resistance for water so that erosion failure and surface slide failure on natural slopes have occured repeatedly. It is very important for making up a counterplan of preventing disasters to evaluate the transition of basic factors of failure caused by the weathering and erosion actions. In this study, the time transition of resistance force for weathering and erosion on Shirasu slopes is evaluated by the laboratory tests and field tests, and the method predicting risk level of slope failure is proposed based on their results. The main conclusions are summarized as follows :1) The influence of repetition of wetting and drying on the shear properties of Shirasu appears in the deformation property. namely, the failure formula as a rock materials changes into that as a soil material.2) Shirasu in the equilibrium under applied shear stress larger than residual shear strength at saturation collapse when taking the action of wetting.3) Shirasu constituted by only soil particles with small value of density, however, is weak in water flow, Shirasu mixing the soil particles with different densities is hard to erode until the coarse particles with high value of density start flowing out.4) After cutting off in-sifu Shirasu slope, the resistance force for soil hardness tester of Yamanaka type decreases with time passing.5) The properties of undisturbd Shirasu can be estimated from weathering erosion properties of artificially solidified Shirasu.6) The occurrence of slope disaster can be dividd into three groups ; basic factor of failure, motive factor and expansion-restrain factor. Disaster prevention potential can be evalated from the multiple logistic analysis based on the consideration that these factors are regarded as risk factor.

广泛分布于日本九州岛南部的白苏，由于其抗水性差，在天然边坡上反复发生侵蚀破坏和表面滑动破坏。评价风化侵蚀作用引起的破坏基本因素的变化，对制定防灾对策具有重要意义。本文通过室内试验和野外试验，对白须边坡抗风化侵蚀力的时间变化规律进行了研究，并在此基础上提出了预测边坡失稳危险度的方法。主要结论如下：1）干湿交替对白砂剪切性能的影响主要体现在变形性能上。即岩石材料的破坏公式转变为土壤材料的破坏公式。2）在施加的剪切应力大于饱和湿陷时的残余剪切强度时处于平衡状态的白苏。3）白苏仅由具有小密度值的土壤颗粒构成，然而，在水流中很弱，不同密度的土壤颗粒混合后，直到密度值大的粗颗粒开始流出，才很难被侵蚀。4）切断in-sifu Shirasu边坡后，山中式土壤硬度计的阻力随时间的推移而减小。5）从人工固化的白砂的风化侵蚀特性可以推测未受扰动的白砂的性质。6）边坡灾害的发生可分为三组;失败的基本因素、动力因素和发展约束因素。将这些因素视为危险因素，通过多元Logistic分析，可以对防灾潜力进行评价。