Vulnerability evaluation of soil material simulated river bank material in torrential rainfall

摘要

In recent years, average monthly precipitation is decreasing while daily rainfall intensity increases.Additionally, the frequency of heavy downpour in the last 20 years is the highest over the past century of which twomonths from August to September are paid attention. The possible effect of this trend on global warming is high. Damageof river bank by torrential rainfall occurs in many parts of Japan, and river bank of the Tenryu River was burst after arecord heavy rain in Nagano prefecture in July 2006. Specifically, influence of river bank by torrential rainfall andseepage from river water are apprehended. Moreove r, behavior of partial saturation on river bank is not graspedcircumstantially, so vulnerability evaluation of river bank is ne cessary in torrential rainfall. However, there is a multitudeof infrastructure such as river bank all over Japan, and it is inefficient to check the vulnerability on all river banks b ylaboratory tests. Moreover, soil properties vary in each area of Japan, and local soil material of the area where the riverbank is to be sited is used for construction . Consequently, this study performed water retentivity test of soil simulatingseepage process in river bank by using representative soil materials from river banks from each area of Japan. From theresult, the authors compared soil -water retentivity curve and one dimensional deformati on characteristics of soil materialin seepage process and evaluated vulnerability of river bank in each area.