A laboratory acoustic emission experiment and numerical simulationof rock fracture driven by a high-pressure fluid source

In order to improve our understanding of rock fracture and fault instability driven by high-pressure fluidsources, the authors carried out rock fracture tests using granite under a confining pressure of 80 MPawith fluid injection in the laboratory. Furthermore, we tested a number of numerical models using theFLAC3D modeling software to find the best model to represent the experimental results. The high-speedmultichannel acoustic emission （AE） waveform recording system used in this study made it possible toexamine the total fracture process through detailed monitoring of AE hypocenters and seismic velocity.The experimental results show that injecting high-pressure oil into the rock sample can induce AE activityat very low stress levels and can dramatically reduce the strength of the rock. The results of thenumerical simulations show that major experimental results, including the strength, the temporal andspatial patterns of the AE events, and the role of the fluid can be represented fairly well by a modelinvolving （1） randomly distributed defect elements to model pre-existing cracks, （2） random modificationof rock properties to represent inhomogeneity introduced by different mineral grains, and （3）macroscopic inhomogeneity. Our study, which incorporates laboratory experiments and numericalsimulations, indicates that such an approach is helpful in finding a better model not only for simulatingexperimental results but also for upscaling purposes.