DYNAMIC FRACTURE AND FRAGMENTATION OF OIL SHALE.

A constitutive model for oil shale was developed from Lagrangian analysis of stress-time histories obtained in plate-impact experiments and from dynamic yield strength data. In these experiments explosive is placed in a hole drilled along the axis of a cylinder of oil shale. The cylinder is placed in a vessel under confining pressure to simulate the overburden, and the explosive detonated. The cylinder is then sectioned at several places so that the damage can be observed. The model was found consistent with the available static and dynamic mechanical and fracture property data and appears to predict the main features and extent of fracture and fragmentation in the plate impact experiment. The results of the small-scale borehole experiments have demonstrated several important advantages. The shock-loaded oil shale is easily sectioned on arbitrary planes, readily providing a thorough, three-dimensional picture of the extent of fracture and fragmentation. Instrumentation with stress or strain gages, or both, is relatively simple and straightforward.