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Grouting has been commonly used for structure controlling in mining engineering. To investigate the mechanism of fracturing grouting, an experiment was conducted under constant flowing conditions. Through the real-time gathering of main parameters and reconstruction of the slurry distribution, the complete grouting process and pressure spread of the high-pressure slurry were revealed. An identification method of fracturing diffusion based on acoustic emission (AE) signals was proposed and verified. The results indicated that the intact rock showed fracturing response with a mutated pressure in a short time. For fractured ones, the grouting process can be divided into five stages: seepage flow, pressure holding, fracturing diffusion, steady flow, and pressure relief. Influenced by the hydraulic fracture and slurry infiltration, there were three states: cement diffusion, water seepage, and the unaffected zone. A calculation method of whole stages for the grouting pressure was proposed based on the Hoek–Brown strength criterion and flow model in a fracture. In addition, AE ring counting occurred during the entire slurry process but was relatively concentrated in pressure holding and fracturing diffusion stages. Considering the zonal distribution characteristics, the AE method was used to characterize the slurry diffusion range and flow paths. The slurry distribution was obtained by the three-dimensional cutting and reconstruction method to verify its feasibility. This study is expected to further clarify the grouting mechanism, and guide engineering practices. Highlights: High-pressure grouting experiment of fractured rock based on acoustic emission was carried out. The whole process of fracturing grouting shows five responses in fractured rock. The pressure calculation model for revealed whole injection process was established in inclined fracture. AE monitoring can be used to identify the splitting-diffusion range and path for fracturing grouting. [ABSTRACT FROM AUTHOR]

Coal mining is threatened by the aquifers below coal seams, and grouting is used to reconstruct the aquifers before mining. However, water gushing-out sometimes still occurs from the grouted aquifers. In this paper, two aspects of grouting in a vertical fracture are studied by numerical methods, including the slurry diffusion distance and the influence of grouting stone body on water inflow and water pressure. First, a grouting model consisting of a fracture and a borehole is proposed based on the hydrogeological conditions and grouting processes. Two hydrodynamic models controlled by the grouting stone body are established to study the variation of the water inflow and the water pressure in the filled section of the fracture. Then, the numerical calculation is carried out in detail. The numerical results show that the diffusion distance following the flow direction is significantly greater than the distance against the flow direction. The dynamic viscosity is successfully used to simulate the plugging effect of the grouting stone body. For a same fracture section, when the ratio of the maximum filled area to the fracture section area before grouting is less than 90%, the flow velocity presents an upward trend with the flow section decreasing due to the Venturi effect caused by the grouting stone. When the ratio of these two areas is more than 90%, the change of the flow velocity can be explained by the equal percentage characteristic of the valve. The data monitored by typical boreholes during grouting show that the water inflow and the water pressure both reduce after grouting or water inflow decrease and the water pressure keep unchanged after grouting, which is approximately in line with the fracture flow pattern controlled by the valve open degree. This study is conducive to the theoretical research of grouting engineering. [ABSTRACT FROM AUTHOR]

In this work, the grouting diffusion law of inclined fractures under flowing water conditions was studied, with the expression of slurry flow network in the infinite inclined plane based on potential flow superposition principle and the numerical model of the inclined fracture grouting process in flowing water established using COMSOL software. The influence of fracture dip angle and initial velocity of flowing water on the diffusion of the slurry was analyzed alongside the variation in pressure field, velocity field, and water flow during the diffusion of the slurry in the inclined fracture. The effectiveness of the numerical simulation method was verified by comparing the simulation results and experimental results. The results indicated that there is a limit value for the diffusion distance of slurry in the direction of smooth and inverse water, while increasing the inclination angle of the fracture contributes to the diffusion of the slurry against the water direction and width direction, which enhances the water plugging effect. The increase in the initial velocity of the water will increase the diffusion distance of the smooth water direction, will weaken the diffusion width of the slurry, and will lead to the grouting water plugging process requiring a longer time. During grouting, the flow velocity in the slurry diffusion width range will be significantly reduced, the water flow channel will be gradually narrowed, and the inlet flow decreased. The pressure field in the inclined direction of the fracture is essentially dominated by hydrostatic pressure. [ABSTRACT FROM AUTHOR]