A generalized constitutive stress-strain relation, which includes the effects of both tensile and shear stresses on crack growth, is presented. A bedded-crack version of the fracture model was incorporated into the YAQUI hydrodynamics code. The average strain resulting from a random distribution of cracks in a stressed medium was used to determine the reduced modulus of the material. Tracer gas flow and pressure decay of a proposed oil shale retort were studied using a finite difference formulation of a Darcy fluid flow model. Preshot geologic characterization of the highly instrumented single-borehole explosive test shots in the Colony Mine is described. Crater blast data for both laboratory- and field-size experiments are given. Results were interpreted using empirical cratering and fragmentation techniques.