  A coupled mech-hydro-chemical model for rock geometry alteration of fractures
under water-rock interaction (WRI) and geostress is developed. Processes
including WRI, asperity deformation, mineral chemical dissolution and pressure
dissolution etc., are taken into account. A feature of this model lies in its
approximate linearization to the non-linear pressure dissolution process, which
makes this model compatible with existing numerical solute transport models.
Case study shows that although usually only a thin layer of rock surface is
invaded by WRI, the mechanical weakening of this thin layer tend to induce
significant increase in rock surface deformation. Thus, the distributed flow
field, mineral dissolution rates, and surface alteration increments etc., are
all affected. This indicates that when fracture flow related issues are
concerned, we should focus on the top thin layer of rock surface rather than
the matrix. Results also show that fluid flow enhances the dissolution of rocks
and development of flowing channels; however, at places where stress induces
high pressure-dissolution but fluid flows slowly, minerals precipitate and fill
up fracture voids. This suggests the hydraulic condition plays a key role in
the development of fracture flow channels and the evolution of fracture
geometry.
