Rock Deformation, Experimental
Experimental rock deformation is concerned with evaluating, through controlled laboratory experiments, the effects of environmental and material factors on the deformational behavior of rocks. A rock is said to be deformed when it has suffered a change in shape, a change in volume, or a loss of cohesion. Of concern here are the irrecoverable, inelastic aspects of deformation.
Hydrostatic stress reduces pore space and produces volume change only; all permanent deformation of significance in rock results from the action of differential stress and is expressed as fracture, flow, or a combination of the two. Fracture is deformation with complete loss of cohesion and is characterized by a physical discontinuity across which tensile stress cannot act. Flow is any deformation, not instantly recoverable, without permanent loss of cohesion. A rock becomes permanently deformed when it is subjected to differential stress that exceeds its strength under