Mechanical and Microcrack Evolution Characteristics of Roof Rock of Coal Seam with Different Angle of Defects Based on Particle Flow Code

Abstract

The creation of the natural ceiling rock of the coal seam is rife with fractures, holes, and other flaws. The angle of the defects has a significant influence on the mechanical characteristics and crack evolution of coal seam roof rock. Multi-scale numerical simulation software PFC2D gets adapted to realize the crack propagation and coalescence process in the roof rock of a coal seam with different angles of defects under uniaxial compression. The effect of flaw angles on the micro and macro mechanical characteristics of rock is also discovered. The results show that: (1) the defect angle has influence on the stress-strain, elastic modulus, peak strength, peak strain, acoustic emission (AE) and strain energy of roof rock of coal seam. When the defect angles are different, the starting position of the roof rock in a coal seam fracture is different. The quantity of microcracks firstly reduces with an increase in defect angles before gradually increasing. At the same fault angle, the cracks are mostly tensile ones and only a few shear ones. (2) When the defect angle is less than 90°, tensile and shear fractures are mostly localized at the defect’s two tips and propagate along the loading direction. When the defect angle is 90°, the tensile and shear cracks are not concentrated at the tip of the defect. (3) As the defect angles increase, the elastic strain energy rises initially and then falls, and the dissipated energy and total input energy both increase continuously. The elastic strain energy is greatest at the highest strength. The study provides a certain reference for the use of various analysis methods in practical engineering to evaluate the safety and stability of rock samples with pre-existing defects.

Damage Evolution Characteristics and Constitutive Model for Coal and Rock under Asymmetric Loading

“…Determination of mesomechanical parameters is a prerequisite for numerical simulation using the discrete element method. Based on the macromechanical parameters and damage modes of coal rock obtained from indoor tests, this paper adopts the “trial and error method” to determine the fine mechanical parameters of coal rock specimens Table shows the successfully calibrated mesomechanical parameters of the coal rock that can be used for subsequent simulations, and Figure shows the comparative results of the stress–strain and macroscopic damage modes of the coal rock obtained from the indoor tests and numerical simulations.…”

Study on the Degradation Effect of Carbonaceous Shale under the Coupling Effect of Chemical Erosion and High Temperature

“…To establish the parallel bond model, we need to calibrate its mesoscopic parameters. The mesoscopic parameters include the shape, size, distribution, density, stiffness, etc., of the particles, which directly affect the macroscopic mechanical properties of the model [27,28]. Based on the macroscopic mechanical parameters of the uniaxial compression test, we used the inverse analysis method by adjusting the values of the mesoscopic parameters, to make the stress-strain curve of the model as close as possible to the test curve [29].…”