Experimental studies on collapse prediction of Shirasu slopes in consideration of the variation of shearing resistance and infiltrationflow caused by various rainfalls on earthquake

在含有可破碎颗粒的火山土“石拉苏”上进行了一系列不排水循环和单调三轴试验。对松散和致密的试件进行了测试，并将测试结果与Toyoua砂的测试结果进行了比较。结果表明，“石拉苏”的不排水循环和单调剪切特性与围压及其密度有很大关系。第一种是利用倍增入渗仪测量入渗速率变化的方法。另一种是研究补给孔内水深变化的方法。对试验中的非稳定入渗进行了数值模拟，以确定Mualem方程的参数。这些参数也是从从原状土壤中测得的实验室试验值中确定的。对这些结果进行了比较，证实了它们之间的一致性。然而，在数值模拟中发现了明显的不同，即对充电孔的计算需要大量的运行时间。结果表明，渗透仪渗透试验操作简便，适用于多种场地的渗透试验。

A series of undrained cyclic and monotonic triaxial tests has been performed on a volcanic soil "Shirasu" which has crushable particles. Testing was performed on loose and dense specimens and the results were compared with those of Toyoura sand. As a result, the undrained cyclic and monotonic shear behavior of "Shirasu" is found to be greatly dependent on the confining pressure and its density.In-situ tests for measuring unsaturated permeability of Shirasu are carried out by means of two methods. The first is the method that measures the variation of infiltration rates from the doublering infiltrometer. The other is one that does the variation of water depth in the recharging holes. Unsteady infiltration in the tests are numerically simulated to identify the parameters of Mualem's equation. The parameters are also identified from the laboratory test values that measured from the undisturbed soil. These results are compared and confirmed to be coincide with each other. However, evident difference is revealed in the numerical simulation ; i.e. the computation for the recharging hole needs great amount of running time. From the results, it is cleared that infiltration test with infiltrometer is easy handling and useful method for the measurement in many locatins.