SHEAR CHARACTERISTICS OF DECOMPOSED GRANITE SOIL COMPRESSIBLE UNDER LOW PRESSURE

In order to investigate the particle crushing and shear characteristics of decomposed granite soil, consolidation tests and direct shear tests were carried out under unsoaked and soaked conditions. A new type of direct shear box with reduced friction was used to know the shear characteristics under low and moderate pressures. Using the strength parameter obtained from direct shear tests under both pressures, we calculated the safety factors of slopes. The results were summarized as follows: 1) Particle crushing of the soil due to the compression and the shear is considerable. 2) The failure line consists of two straight lines changing the slope at normal stress of σ=20kN/m2 which correspond to the lower boundary of particle crushing region. 3) The degree of decrease in shear strength due to soaking is greater in the region of low pressures than at moderate pressures. 4) For shallow sliding failures, the safety factors under the low pressures is a little less than that under the moderate pressures.