Abstract
The dynamic tensile failure of rock is a main failure mode in deep underground engineering projects. The microscopic failure mechanism analysis of this failure mode plays a key role in dynamic disaster warning. Moment tensor inversion is a very well-known method used to analyze failure mechanisms. However, an acoustic emission (AE) event cannot be accurately distinguished in rock dynamic experiments at the laboratory scale, because there are hundreds of AE events generated within a few hundred microseconds in one dynamic test. Therefore, moment tensor analysis is rarely applied in rock dynamic tests with laboratory scale. In this paper, AE and moment tensor simulations with the discrete element method (DEM) are introduced to analyze the microscopic failure mechanism of rock under a dynamic Brazilian test. Comparing the simulation results of AE and moment tensor analysis with the simulation results of micro-crack with DEM, the moment tensor discriminant method can obtain the mechanical mechanism and energy level of micro-cracks. Furthermore, R, which is the ratio of isotropic and deviatoric components of the moment tensor, is used to analyze the AE source mechanism. The implosion, shear, and tensile of the AE source mechanism can better explain the evolution process of main axial crack and the shear failure zones of the Brazilian disc specimen under dynamic tensile simulation. These findings contribute to a better understanding of the microscopic failure mechanism of rock under a dynamic tensile test than the statistical types of micro-cracks based on break bonds with DEM.
Highlights
Dynamic tensile failure is a main mode of rock failure in deep underground engineering projects [1, 2]
Previous studies mentioned above show that acoustic emission (AE) source simulation and moment tensor analysis have great advantages in studying rock fracture mechanisms. We introduce this method of AE and moment tensor simulation based on PFC to analyze the micromechanical mechanism of the rock dynamic tensile failure process
The rock dynamic tensile failure process is simulated by the SHPB model as established in the previous section
Summary
Dynamic tensile failure is a main mode of rock failure in deep underground engineering projects [1, 2]. It is important and necessary to study the micromechanical mechanism of rock dynamic tensile failure [3]. An acoustic emission (AE) event cannot be accurately distinguished in rock dynamic experiments at laboratory scale. Moment tensor analysis is rarely applied in rock dynamic tests with laboratory scale. The bond between particles break and many broken bonds will lead to rock failure when the rock specimen is under force action in simulation, which is often used to analyze the meso-crack extension [9]. The type statistics of bond break is used to distinguish the rock dynamic failure type [10]. The rock dynamic experiment and simulation studies show that the micro-crack of rock materials is mainly of the tensile crack variety no matter what the macroscopic failure mode is [11]. A wrong result may be found if the macroscopic failure pattern is directly judged by statistical micro-crack types [12]
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