UNDRAINED CYCLIC SHEAR CHARACTERISTICS OF DENSE VOLCANIC COARSE-GRAINED SOIL,"SHIRASU"

Previous liquefaction studies on volcanic soils generally concentrate on the fines contained within sandy volcanic soils, however, typical Shirasu volcanic soil has a high coefficient of uniformity and contains 20%-30% gravel and non-plastic fines. A series of undrained cyclic shear tests was performed on dense samples of Shirasu to assess the influence of grain size distribution on the liquefaction susceptibility. The relative density of samples was 90%. Testing was carried out on various combinations of the gravels, the sands and the fines. The tests were also carried out over a range of confining stresses. The results of these experiments clearly demonstrated that the effect of initial confining pressure on cyclic shear strength for dense volcanic soil differs for different grain size distributions. The cyclic strength characteristics were also close to particle crushing.