Evolution of the hydraulic wetting path in fractured coal under true triaxial stress and the influence mechanism of fracture orientation

The coal seam water injection technique is a comprehensive method for mitigating disasters in coal mining, also referred to as "green mining." The objective is to mitigate coal seam pressure, improve permeability, lower temperature, and decrease dust, resulting in significant advantages. This study utilizes experimental research to construct a Discrete Fracture Network (DFN) model through the application of numerical methods. The aim is to investigate the impact of many main cracks on the pathways of water migration and the impacts of wetting in coal seams during the process of water injection. The research presents two models: the intact model and the fractured model. A computational study examines fluid flow within a coal seam and determines the optimal range of hydraulic wetting. This experiment entails the application of a consistent water injection pressure while subjecting the system to authentic triaxial stress conditions. The results indicate that the coal samples align perfectly with the data collected from the physical simulations carried out in the laboratory. Increasing the water injection pressure will better increase the wetting range. The presence of primary cracks within the coal seam also contributes to the expansion of the range of wetness, the fractured model expands the wetting volume by 1.16-1.4 times, and the rate increases with time. The anisotropy coefficient is used to explore the influence of cracks on the wetting direction and contour. The maximum anisotropy coefficients are 0.21 and 0.27, respectively, indicating that the fracture factor has the greatest influence on the wetting direction and contour. While the dominant direction of fracture groups creates the main channel or centralized conduit for wetting. The research results will establish a thorough theoretical framework for studying the hydraulic wetting process of fractured coal and for enhancing the technique of injecting water into coal seams for wetting objectives.