Grouting is one of the main technical means to prevent water inrush hazards in coal seam floor aquifers. It is of great significance to elucidate the diffusion law of slurry in the process of grouting in fractured aquifers for safe mining in coal mines. In this paper, the mechanism of slurry diffusion in horizontal fractures of fractured aquifers was studied based on the Bingham slurry with time-varying characteristics; additionally, a one-dimensional seepage grouting theoretical model considering the temporal and spatial variation of slurry viscosity under constant grouting rate was established. In this model, the grouting pressure required by the predetermined slurry diffusion radius can be obtained by knowing the grouting hole pressure and injection flow. Slurry properties, fracture parameters, grouting parameters, and water pressure were the parameters affecting the slurry diffusion process. Looking at the problem of water disaster prevention of coal seam floor in the Working Face 2509 of the Chensilou Coal Mine, according to the aquifer parameters and model calculation results, a grouting scheme with a slurry diffusion radius of 20 m and grouting pressure of 12 MPa was proposed. Finally, with the comparative analysis of the transient electromagnetic method (TEM) and water inflow before and after grouting, it was verified that the design grouting pressure and the spacing of grouting holes were reasonable and the grouting effect was good.

Previous research recognized the threat of faults to safe mining and the importance of identifying fault failure patterns, and began to use theoretical research and numerical simulations to study the activation laws of faults during mining. Conventional wisdom may suggest that the height of the fractured water-conducting zone (FWCZ) of the overburden strata over goaf will be increasingly caused by fault activation, thereby causing roof water inrush, in particular, goaf water existing in the roof of working face. Therefore, the FWCZ in the overburden strata make accurate judgments that are regarded as a key foundation to evaluate the safety of coal mining under water bodies. In view of this problem, the 15,103 working face of Wenzhuang Coal Mine in Shanxi Province were taken as the engineering background, the height of the FWCZ of the adjacent 15,100 working face was observed by drilling fluid leakage method and drilling television method, the observed results provided a reference for judgment of the height of the FWCZ of 15,103 working face. Additionally, the drilling method was adopted to conduct exploration on the terminal location of F6 reverse fault in overburden strata of No. 15 coal seam, the result showed that the disturbance range of F6 reverse fault was located in the FWCZ formed after mining the 15,103 working face. Furthermore, the method of numerical simulation analysis was used to study the failure height of overburden strata after mining the 15,103 working face through F6 reverse fault. The height of the FWCZ of F6 reversed fault was basically equal to that of the upper and lower plates, and F6 reverse fault had no influence on the height of the FWCZ after mining the 15,103 working face. There was a sufficient thick overburden strata between the maximal elevation of the fractured zone and the roof goaf water, and mining through F6 reverse fault under old goaf was safe and reliable. The research results can provide reference for the safe mining of passing through reverse faults under the influence of roof goaf water.

The fault rocks exhibit low strength, high deformability, and high porosity, making them prone to connecting with the coal seam floor and forming water-conducting channels under the influence of mining activities and aquifer water pressure. Investigating the water inrush mechanism in fault rocks beneath coal seam floors is crucial for ensuring the safety and efficiency of coal mining operations involving fault structures. A test was conducted on the seepage-creep coupling of fault rocks under various stresses, water pressures, and cementation strengths. Based on this, a spatial and temporal evolution model for the seepage-creep coupling characteristics of faulted rocks was developed. The results reveal that the evolution of volumetric strain, flow velocity, porosity, and permeability in the fault rocks can be divided into two stages: the creep compression stage and the expansion damage stage. During the creep compression stage, the samples exhibit more pronounced creep deformation, transitioning into the expansion damage stage earlier under conditions of increased axial pressure, reduced confining pressure, elevated water pressure, and decreased cementation strength. The simulation results align closely with the experimental data. From the creep compression stage to the expansion damage stage, the seepage-creep characteristics evolve gradually at first, followed by a distinct turning point upon entering the expansion stage. This turning point is marked by a rapid increase in volume, along with a sharp rise in flow velocity, porosity, and permeability. Spatially, the seepage-creep characteristics exhibit a non-uniform change from the inlet to the outlet, with expansion damage characteristics first appearing at the outlet. This research provides a theoretical basis for safe and efficient coal mining in fault-affected areas.

Rock mass inherently contains discontinuities, and shear sliding of rock masses along discontinuities is the most common failure mode of rock mass in engineering practice (such as slope, dam and tunnel). In this study, the mechanical and failure properties of rock fractures were examined through direct shear tests, pre-peak tiered cyclic shear tests and multistage loading shear creep tests. The results show that the deformable memory of rocks can be observed from shear stress-shear displacement curves, namely reloading curves continued to increase along the loading curve of the last cycle under the pre-peak tiered cyclic shear loading. The envelopes of shear stress-shear displacement curves were similar to the variation trend of shear stress-shear displacement curves obtained in the direct shear test. Besides, the variation trend of residual shear displacement (RSD) and relative residual shear displacement (RRSD) before slip instability were obtained by the data analyses of rock mass under pre-peak tiered cyclic shear tests. It is found that the change in the friction and sliding state of rock fracture is the main reason for the fluctuation of shear stress-shear displacement curves. The Chen's method was used to process the multistage loading shear creep curves and the three creep stages were analyzed. Moreover, the complex creep models in some previous studies were discussed and the data of shear creep tests were successfully fitted to the classical Burgers model. This study provides a guidance for the study on the shear instability of rock fractures under different shear loading paths.