RESEARCH ON UNSATURATED INFILTRATION CHARACTERISTIC OF RAIN WATER AT IN-SITU ON EARTHQUAKE COLLAPSE OF SHIRASU SLOPE

九州南部地区的白苏土壤面积达4700平方公里，其中约72%位于鹿儿岛，27%位于宫崎，1%位于熊本。白浪的土地被归类为“不寻常的土壤”，因为它经常是灾难的原因。近年来，九州南部沿海地区的土地开发一直在增加，白苏的土壤被用来开垦土地。因此，评估这种填海造地在地震情况下的稳定性是当务之急。采用双环渗透仪测量入渗速率变化的方法，对白松地基非饱和渗透率进行了现场测试。结果表明，用渗透计进行渗透试验是一种简便易行的方法，适用于许多地方。

The Shirasu soil in the southern Kyushu area covers as much as 4,700km^2, about 72% of it is situated in Kagoshima, 27% in Miyazaki and 1% in Kumamoto. The Shirasu ground is classified as "Unusual soil" because it has frequently been the cause of disasters. In recent years, land development along coast lines of southern Kyushu have been on the increase and Shirasu soil has been used to reclaim land. Therefore, evaluating stability of such a reclaimed land in case of earthquakes is in urgent.In-situ tests for measuring unsaturated permeability of Shirasu ground are carried out by means of that measurs the variation of infiltration rates from the double-ring infiltrometer. From the results, it is cleared that infiltration test with infiltrometer is easy handling and useful method for the measurement in many locations.