Numerical Investigation of Fracturing of Coal with Cleats Caused by Supercritical CO2 Explosion.

Abstract

The experimental and numerical responses of coal specimens were studied in this work. A supercritical CO2 explosion experiment was carried out on the coal specimens using an independently developed triaxial load platform. The characteristics of crack generation in the specimens were obtained for different initial stresses. For a better understanding of the influence of cleats in a coal seam, a MATLAB code is developed to identify the actual geometry of the cleat in the coal specimen images, enabling the geometric representation of coal with cleats. The fracturing of coal with cleats induced by supercritical CO2 explosion under initial stress is validated using a combination of smoothed particle hydrodynamics and the finite-element method. The cleat can absorb and reflect the stress wave and hinder the propagation of cracks. According to the transmittance of the stress wave, the density and size of cracks that propagate through the cleat, the influences of the dip angle of the cleat, the aperture of the cleat, and the distance from the cleat to the center of the blast hole are discussed. The results show that the greater the distance from the cleat to the center of the blast hole or the greater the aperture of the cleat, the greater the hindrance of the cleat to the propagation of the cracks. With the increase of the dip angle of the cleat, the hindrance of the cleat to crack propagation first increases and then decreases.