An experimental study on fracture process zone of rock

To reveal the mechanisms and composition of energy consumption in rock fracture and prevent the risk of microcracking in the storage of nuclear waste, carbon dioxide and hydrogen. An experimental study on fracture process zone (FPZ) of rock was performed. In the study, the theoretical length of FPZ was calculated by applying the J-integral combined with the stress distribution around crack tip. Utilizing digital image correlation (DIC) technology, the displacements were measured during the whole loading. By analyzing the displacement distributions at different loading stages, the fractured ligament of each specimen is divided into three zones: intact zone, crack propagation zone and fracture process zone (FPZ). The length and the migration velocity of the FPZ were determined, and the crack propagation velocity was measured. Using optical microscopy, X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), microstructure in the FPZ was studied. The FPZ and the effective Young’s modulus were introduced to modify the models for calculating crack tip opening displacement.