Abstract
The existence of flaws in brittle rocks or rock-like materials has an obvious influence on the material mechanical properties and cracking behavior of civil engineering projects. In this work, the two-dimensional particle flow code PFC2D was used to study the deformation and strength properties, failure processes, and acoustic emission (AE) characteristics of mudstone with a single preexisting flaw. First, the procedure to construct a parallel bond model is introduced. The Weibull distribution is used to reflect the mechanical heterogeneity of rocks. Then, the microscopic parameters used in PFC2D are calibrated to the macroproperties of mudstone obtained from laboratory tests under the uniaxial compression. The results indicate that the increases of the flaw inclination lead to the increasing uniaxial compressive strength and elastic modulus. In terms of microcrack evolution, the initiation, propagation, and coalescence of microcracks are closely related to the force chain. Specifically, an “X” shaped tension force chain concentrated area around the preexisting flaw is founded, which is the most prone area for microcracks to initiate. With an increase in flaw inclination, the b value of AE also shows an increasing trend. By incorporating the AE event numbers into a damage variable, this paper derives a constitutive model, which is verified by numerical results on brittle rocks with a single preexisting flaw under uniaxial compression.
Highlights
With the development of productivity and technology, increasingly open-pit coal mines have formed a series of high and steep slopes. e slope contains a rich network of fractures, and the stability of these slopes greatly affects the production and life of open-pit coal mines and the safety of personnel
Numerical test curve Fitting curve (a) average. erefore, within the allowable error range, it can be considered that the damage constitutive model constructed by the acoustic emission (AE) event numbers obtained from the AE phenomenon of rock based on the moment tensor simulation can better describe the complex relationship between the deformation and strength of mudstone containing a single preexisting flaw with different flaw inclination under uniaxial compression
The parallel bond model (PBM) with the Weibull distribution calibrated by laboratory tests is used to construct models containing a single preexisting flaw with different flaw inclinations to analyze the deformation and strength properties, the propagation of microcracks, the fractal dimension of the failure surface, and the acoustic emission characteristics. e main conclusions of this work can be summarized as follows: (1) e PBM coupled with the Weibull distribution can well simulate the heterogeneity of mechanical properties inside the rock. e uniaxial compressive strength (UCS), elastic modulus, and Poisson’s ratio of a rock increase with the increase of flaw inclination
Summary
With the development of productivity and technology, increasingly open-pit coal mines have formed a series of high and steep slopes. e slope contains a rich network of fractures, and the stability of these slopes greatly affects the production and life of open-pit coal mines and the safety of personnel. For low-strength fractured rock masses, such as mudstone, there are relatively few studies on the mechanical properties and microcrack propagation [1]. Erefore, it is necessary to conduct a more detailed study on the mechanical properties and microcrack propagation of mudstone containing a single preexisting flaw. Aliabadian et al used 3D printing technology and digital image correlation technology, and the mechanical properties and strain field laws of rock-like materials with single and double flaws in Brazilian testing were studied [4]. Many researchers have used PFC to study the mechanical properties and the growth of microcracks in rock materials or rock-like materials with preexisting flaws.
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