Effect of relative density on the matric suction and its contribution to shear strength of unsaturated sandy soil

The bearing capacity of soils and its prediction is a subject that is practiced every day. Shallow foundations are usually constructed on unsaturated soils where the soil strength may be higher compared to fully saturated soils due to the contribution of the matric suction resulting from the reduction in degree of saturation. In this paper, the variation of the matric suction due to variation in degree of saturation and the relative density of sandy soil is studied through experimental tests that were carried out on four states of sandy soil (Dr = 20%, Dr = 35%, Dr = 55%, and Dr = 75%). The results show that the variation in relative density and degree of saturation causes significant changes and important equations were proposed describing these effects on the matric suction, consequently, the variation of the matric suction shown has a great effect on the shear strength of sandy soil.