Abstract
The growth and evolvement features of crack are of great significance to study the failure mechanism of rock mass and valuate the stability of the cavity. In this study, in order to obtain the mechanics parameters and external macroscopic crack propagation characteristics of red sandstone, triaxial compression tests were carried out. Based on the experimental results, a numerical model was established through the reasonable parameter calibration by the PFC3D software. The internal and external crack propagation processes of red sandstone under triaxial compression were simulated. Moreover, to verify the simulation results, the CT scanning and three-dimensional reconstruction technologies were used to observe the internal crack state of the specimens. The results showed that the internal crack failures occurred first at the end of the rock specimen. Then, the microcracks continued to accumulate and expand under the combined action of axial stress and confining pressure. The accumulated microcracks finally converged to form a macroscopic oblique shear failure. Based on the homogenizing treatment and reasonable parameter calibration, the internal and external crack expansion and evolution processes of the rock were simulated by the PFC3D model and the simulation results are consistent with the results obtained from the triaxial compression test and the CT scanning. The macro- and microfailure mode of crack propagation of the specimen deepens the understanding of rock failure mechanism. The PFC3D homogenization simulation method provides a new feasible method to study the macro- and microfailure mode of internal and external crack propagation of rock under compression.
Highlights
The rock mass is an anisotropic heterogeneous body formed by one or more rock-forming minerals in a certain combination that contains structural defects such as cracks and joints
In the ore excavation process, the rock mass is subjected to complex loading and unloading stress processes, which leads to the deformation and destruction of the rock mass
By comparing internal cracks from the CT three-dimensional reconstruction of red sandstone with numerical simulation results under confining pressure of 15 MPa, it is clear that the shape of the main failure cracks inside the simulated rock specimen is consistent with the internal cracks of the real rock specimen
Summary
The rock mass is an anisotropic heterogeneous body formed by one or more rock-forming minerals in a certain combination that contains structural defects such as cracks and joints. Yang et al studied the strength and failure characteristics of red sandstone by the triaxial compression test [17]. Fan et al established the bonded particle models containing flaws or/and openings in order to investigate the mechanical properties as well as the crack propagation characteristics of the rock under uniaxial compression [27]. To reveal the crack evolution process of red sandstone, triaxial compression tests on red sandstone under different confining pressures were carried out to obtain the mechanical parameters and failure characteristics. Through the comparison of the results obtained from laboratory tests, CT images, and PFC3D simulations, the feasibility of the PFC3D model to study the crack propagation characteristics of the rock specimen was verified. The proposed methodologies and the obtained results provide a new method for the study of rock mechanical properties and damage mechanisms
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