Research on the preparation and diffusion characteristics of coal seam bottom fracture grouting material based on solid waste synergy

Fracture in the top and bottom plates of the coal seams in the Lubei Mining Area of China have developed to communicate with the Austrian gray pressurized water, and the threat of water damage is extremely serious. The rapid development of China's domestic economy has led to an increasing amount of industrial solid waste, which seriously jeopardizes the safety of the ecological environment. Based on the current problem, the slag powder (S) and waste rubber particles (R) were used as the main material, supplemented by cement (C) reinforcement with alkali slag (AS) excitation, and the mine fissure grouting and sealing reinforcement material was developed. The effects of water-cement ratio and (S: R) mass fraction on the physical and chemical properties of the grouted rock mass were analyzed using indoor tests, and the optimal components were determined; secondly, three-dimensional slurry-water-rock flow-solid coupling two-phase seepage simulation was realized using COMSOL, which revealed the diffusion morphology of the solid-waste slurry, preliminarily verified the feasibility of the grouting diffusion inside the rock mass, and determined the diffusion rule of the solid-waste slurry concerning the grouting pressure. The results indicate that at a water-cement ratio of 0.7 and a mass fraction of (S: R) at (70%:30%), the slurry has a flow degree of 275 mm, a water precipitation rate of 7.4%, a 28d compressive strength of 6.9 MPa, and follows the Bingham rheological model, with good injectability. Moreover, the slurry diffuses in simulated fracture grouting in a similar pattern to ultrafine cement slurry, satisfying the reinforcement requirements of field grouting. The research content realizes the combination of mine water damage control and solid waste scale, which is critical to ensuring production safety and the mine's green sustainable development.