Numerical simulation of damage and failure of coal-rock combination based on CT three-dimensional reconstruction

With the development of deep mining, coal-gas compound dynamic disaster becomes increasingly serious, which seriously restricts the safe and efficient mining of deep mine and the coordinated development of mining environment.The coal-gas compound dynamic disaster is essentially the result of the whole failure and instability of the “coal-rock” combination system under the combined action of certain in-situ stress and gas pressure with the strong disturbance of engineering geology.In order to study the damage and failure characteristics of gas-bearing coal-rock combination, the CT scanning experiment was carried out on raw coal and sandstone by using CT technology.The internal fracture structure of coal and rock was obtained, and the three-dimensional reconstruction model of mesostructured of coal-rock combination was established.FLAC3D was used to simulate the damage and failure of gas-bearing coal-rock combination under the condition of conventional triaxial compression and unloading confining pressure and the energy evolution of coal-rock combination.The results show that the average error of fractal dimension between the original CT image and the corresponding reconstructed image is 3.12%,so the accuracy is 96.88%.Under the condition of numerical simulation in this study, during the initial loading stage, the coal-rock combination appears small-scale plastic failure at the contact surface, but the coal-rock combination structure is still in the elastic stage.With the loading process, the coal body outside the contact surface of coal-rock combination begins to appear plastic failure, then the coal body at the contact surface began to appear plastic failure in a large scale.As the loading continues, the whole coal body is destroyed, and the rock mass at the contact surface is also plastic damaged.Meanwhile, the whole coal-rock combination is unstable and failure.With the increase of confining pressure or the decrease of gas pressure, the peak strength, the total input energy, elastic strain energy and dissipative energy of gas-bearing coal-rock combination all present an increasing trend.