SHEAR STRESS ENHANCEMENT OF VOID COMPACTION.

Abstract

The spherical model is used to examine the influence of the presence of a shear stress on the volumetric compression of a porous solid. The linear, elastic solution for a hollow sphere subject to homogeneous tractions on the outer boundary is first obtained. Then, assuming that the matrix material is governed by the Drucker-Prager yield criterion, the elastic solution is used to derive an analytic expression for the onset of yield in the hollow sphere. The expression for the initial yield surface shows that the presence of a shear stress hastens the onset of yield in the sphere in comparison to a hydrostatic loading condition. This result agrees well with experimental data. The spherical model results clearly exhibit the experimental finding that the presence of a shear stress tends to enhance the volumetric compaction of porous solids in comparison to a hydrostatic loading condition. For both a porous rock and metal sample, agreement between the spherical model and experimental results is excellent.