Particle mechanics model for the effects of shear on solute retardation coefficient in rock fractures

Damage on rock fracture surfaces during shear process changes the mechanical and hydrological properties of the fractures, and therefore affects solute migration in fractured rocks. Laboratory experiments on this issue are rarely reported in the literature due to technical difficulties in measuring asperity damage and gouge generation. To conceptually investigate the effects of rock fracture surface damage on solute sorption during shear, we present a retardation coefficient model considering the effect of wear. The particle mechanics model was employed to investigate the effects of gouge generation (abrasive wear) and microcrack development in the damaged zones, on the solute retardation coefficient in rock fractures. The results from demonstration examples show that the shear process significantly increases the retardation coefficients, by offering more sorption surfaces in the factures due to gouge generation (wear), microcracking and crushing of gouge particles. Conceptually three damage zones are classified to characterize the various wear impacts on the solute transport in single fractures. Outstanding issues of the present model and suggestions for future study are also presented. (C) 2012 Elsevier Ltd. All rights reserved.