Fracture Behavior of Intact Rock Using Acoustic Emission: Experimental Observation and Realistic Modeling

It is well known that acoustic emission (AE) is a powerful nondestructive testing tool for examining the behavior of materials deforming under stress. One can use it to monitor fracture or damage in a rock mass by listening to AE events during failure under compressive loads. In this paper, an experimental study on the AE source location in square cylinder granite specimens under uniaxial compression is reported. In order to determine the three-dimensional location of AE events, eight AE sensors were mounted on the specimen. The AE source location was determined via the acquisition of eight channel AE sensors after filtering, processing, reporting, and visualizing seismic data. On the basis of the laboratory experiment results, the granite sample was numerically simulated via the Burgers model using the discrete element program PFC2D (Particle Flow Code in Two Dimensions) to further study the mechanism of fracture initiation and propagation in intact rock. In PFC2D, materials may be modeled as either bonded (cemented) or unbonded (granular) assemblies of particles. It can describe nonlinear behavior and localization with accuracy that cannot be matched by typical finite element programs. The consistency of stress-strain curves obtained with PFC2D and with the test results shows that PFC2D is a practical tool for reproducing AE events in rock, and use of the Burgers model is feasible in the field of rock failure and provides an analysis of the microcracking activity inside the rock volume to predict rock fracture patterns under uniaxial loading conditions.