This paper presents the physical properties of pumice fall deposit sampled at Takanodai, Minami-Aso village, Kumamoto Prefecture in JAPAN, where long runout landslide took place due to the main shock from the 2016 Kumamoto earthquake. A series of direct box shear tests under various conditions such as constant-stress, constant-volume and cyclic-shear loading conditions was conducted for undisturbed and unsaturated samples of pumice fall deposit to evaluate shear strength properties and seismic behaviors. Based on the slope stability analysis followed by the soil runout analysis at Takanodai, the pumice fall deposit layer shows a large horizontal displacement. While pumice fall deposit layer has enough stability under a normal condition, the strength reduction induced by the soil particle crushing is considered to be one of the factors caused a long runout landslide at the above site.

本文介绍了在日本熊本县南阿苏村高野台采样的浮石秋天矿床的物理性质，由于2016年熊本地震的主要地震，该地区发生了长期跳动滑坡。对浮石和非饱和的浮石秋天沉积物样品进行了一系列在恒定应力，恒定体积和循环剪切载荷条件下的直接箱形剪切试验，以评估剪切强度特性和地震行为。在高野台的边坡稳定性分析和土壤跳动分析的基础上，浮石降落沉积层显示出较大的水平位移。在正常情况下，浮石降落沉积层具有足够的稳定性，