Frictional effects on the volumetric strain of sandstone

The contributions of frictional slip on the nonlinear, hysteretic deformation of sandstone in the reversible regime (i.e., prior to the onset of permanent deformation) for uniaxial strain compression are investigated through an analysis of a Hertz-Mindlin face-centered cubic sphere pack model and laboratory stress-strain tests on Berea sandstone. The analysis demonstrates that the dynamic(1) moduli are path-independent functions of the strain. The analysis also reveals that for uniaxial strain consolidation it is possible to decompose the volumetric strain into a path-independent contribution from nonlinear grain contact deformation and a path-dependent contribution from frictional (slip) compaction. Laboratory stress-strain measurements on Berea sandstone support these findings and, in addition, reveal that frictional compaction accounts for a significant portion of the volumetric strain of Berea sandstone. (C) 2000 Elsevier Science Ltd. All rights reserved.