Undrained Triaxial Tests on Saturated Sands and Their Significance in the General Theory of Shear Strength

Synopsis In this Article the results of a series of undrained triaxial-compression tests on saturated sand are presented. These indicate: that, under appropriate conditions, a frictional soil having no true cohesion and a dilatant * structure will exhibit zero angle of shearing resistance and will have the shear characteristics of a purely cohesive material with reference to total stresses; that, if a certain value of negative pore-water pressure is reached during shear, these conditions cease to be fulfilled and an apparent angle of shearing resistance is measured. The factors controlling the changes in pore-water pressure during the application of an all-round pressure are analysed in terms of the relative compressibilities of the soil structure, the pore water, and the soil grains; and of the areas of contact between the soil grains. The analysis leads to the conclusion that the angle of shearing resistance in undrained tests (Φu) in saturated soils should have values which are too small to be observed...