Shear Failure in Granular Media

Abstract

A new concept, effective confining contact stress (product of porosity and effective confining stress), used to analyze the mechanism of shear failure in granular materials with special reference to the reduction in effective angle of shearing resistance with increases in confining stress under triaxial compressive stress. Steel balls and sands from borehole, quarry, and river are studied. The results of the tests, which include unusually high stresses, show direct dependence of the angle of shearing resistance on effective confining contact stress within the dilative range regardless of the drainage condition and extent of particle crushing in the tests. This makes possible the formulation of a method by which the effective angle of shearing resistance of a material at any preshear porosity and confining stress can be estimated from the results of a limited number of drained tests within the dilative range. The physical significance of the dependence of shear strength on the new parameter is analyzed.