FRACTURE-TOUGHNESS DETERMINATION OF LAYERED MATERIALS

Layered materials, such as sedimentary rocks, are ubiquitous. A newly developed fracture toughness test specimen, which is semi-circular in shape and contains an edge-crack, is subjected to three-point-bend loading. The fracture load and the fracture energy of a layered rock are then measured with static tests, and the fracture toughness is determined using a stress intensity factor method, a compliance method and a J-integral based method. The results of all three methods agree satisfactorily showing that the fracture toughness determination using linear elastic fracture mechanics is valid for anisotropic rock materials. Specifically, the static fracture toughness of oil shale, which is a typical layered rock containing fossil fuel, was measured.