SHEAR-STRENGTH CHARACTERISTICS OF 2 SAPROLITIC SOILS

The saturated and unsaturated shear strength behavior of an undisturbe d, completely decomposed fine ash tuff and an undisturbed, completely decomposed granite from Hong Kong were studied using direct shear and triaxial tests. The completely decomposed fine ash tuff is a fine- to medium-grained saprolite. The completely decomposed granite is a coars e-grained saprolite. Results show that matric suction increases the sh ear strength of both soils. The extent of the increase in the shear st rength with matric suction is related to the soil-water characteristic curve for the soil and to the amount of dilation during shear. The ef fect of matric suction on the shear strength was more pronounced for t he fine- to medium-grained completely decomposed fine ash tuff than fo r the coarse-grained completely decomposed granite. These studies on t he saprolitic soils provide insight into the understanding of the shea r strength of unsaturated, coarse-grained soils.