2020 Volume 20 Issue 1 Pages 1_37-1_50
In recent earthquakes, slope failure occurred with muddy collapse and flow at gentle slopes made of volcanic sandy soil. It seemed that the volcanic sand would be liquefied even in unsaturated condition in these damages. In this study, the unsaturated tri-axial tests using two kinds of volcanic sandy soils were conducted under the different initial conditions of suction and degree of saturation. Furthermore, numerical simulations were also performed in order to reproduce the experiments and make clear the factors which affect liquefaction strength in unsaturated condition. The experiments showed that the cyclic behaviors varied largely depending on kinds of volcanic soils and the unsaturated conditions determined by the values of suction and the degree of saturation. The numerical simulation which considers three phase (soil skeleton, pore water and pore air) reproduced the tendency of experiments. Furthermore, the parameteric study showed that the cyclic behavior of volcanic soils depend on the soil water characteristic curves.
