The tailing paste thickening technology was investigated to achieve goaf reduction treatment and tailing resource utilization of metal mines and reach the effect of controlling two hazards with one waste. However, superfine tailing particles could easily form suspended water-locking flocs in the thickening process, which seriously affected the increase in the underflow concentration in the thickener. Undisturbed compression-stage bed samples were extracted using an in situ sampling method through a continuous dynamic thickening experiment. Then, the morphologies and geometrical structures of micropores were analyzed through high-precision computed tomography scanning. Subsequently, the influences of the shear evolution of pore structure and seepage channel on the dewaterability of underflow slurry were explored by combining Avizo software and 3D reconstruction technology. The thickening and dewatering mechanism of underflow slurry was also revealed. Results showed that under the shear action, the flocs were deformed and compacted, forming a high-concentration underflow. On this basis, the original micropores were extruded, deformed and segmented. Moreover, many loose micropores were formed, the connectivity became poor and the total porosity declined. The diameter of the water-conducting channel in the sample was enlarged because of the shear force and the seepage effect improved. The maximum flow velocity inside the pores was 1.537 μm/s, which was 5.49% higher than that under the non-shear state.

Clay cement grout is frequently employed in geotechnical reinforcement projects. However, laboratory test revealed that clay cement slurry does not consolidate in a closed environment for an extended period of time, with cracks forming during the consolidation process under natural conditions, indicating that the geotechnical reinforcement poses dangers. Stone powder is a powdery solid waste similar to clay materials. Stone powder particle surfaces provide an attachment point for cement reaction, which can speed up cement hydration, with the ability to substitute clay cement slurry. According to our findings, the bleeding rate of clay cement slurry is 14.80% at 290 mm fluidity, and that of the same mass ratio (1:3) as stone powder cement slurry is 11.09%. The bleeding rate is minimal, which promotes the creation of an integral structure after setting between the slurry and lose rock and soil. Mechanical test results show that the strength of the stone powder cement slurry hardened body is 1458 kPa, whereas the strength of the clay cement slurry hardened body is 436 kPa. Microstructural analysis shows that the stone powder cement hardened body has more hydration products and is porous than the clay cement hardened body. The hardened body of stone powder cement slurry has high strength and resistance to external loads, which can increase the bearing capacity and improve the geotechnical reinforcement effect.

Layering of filling body is common in large-scale filling areas. In this paper, the cement–sand ratio of 1:8 is based on the configuration of 68%, 70%, 72% and 74%; four concentrations; and filling layers of one-, two-, three- and four-layered cemented filling samples. Combined with a uniaxial compression test and two-dimensional particle flow software (PFC2D), the mechanical properties and failure modes were explored. The results show that the concentration can strengthen the uniaxial compressive strength of the filling body while increasing the filling times weakens its power; therefore, the constitutive damage model was constructed. It was found that the initial layered damage existed in the layered filling, and the total damage showed an upward trend of first fast and then slow; the main failure modes of one-layer and two-layer backfills showed prominent shear failure characteristics, and the three-layer and four-layer fillings were closer to tensile failure. From the crack generation to the specimen failure, there is a mutual conversion between different energies.

A larger mining height leads to easy caving of the coal wall in the working face. The flexible reinforcement method during the mining period of the working face affects the normal mining of the working face, and the high strength of the traditional bolt/cable material affects the operation of the shearer drum, so it is necessary to seek a reinforcement material which does not affect the production and the drum coal cutting. This paper proposed a technical scheme of coal wall reinforcement by pre-grouting with a cuttable aluminum–plastic composite pipe which is easy to cut during mining in the working face, tested the mechanical properties of the “grouting + flexible pipe” specimen, and obtained the optimal support spacing by numerical simulation and carrying out an industrial test. The results show that the tensile strength of aluminum–plastic composite pipe is much higher than that of coal spalling and the elongation is much higher than that of the anchor rod. When double-row composite grouting holes are arranged 1.5 and 3.0 m away from the roof, the supporting effect is better. Underground grouting shows that pre-grouting before mining according to the advancing speed of the working face 10–14 days in advance can effectively fill the coal cracks and significantly improve the integrity of the coal wall.

Adding basalt fiber into concrete can significantly improve its mechanical properties. In order to explore the influence of basalt fiber content on the uniaxial compressive strength and splitting tensile strength of concrete and the mechanism of fiber action, this paper conducts compressive and splitting tensile tests on three kinds of basalt fiber concrete specimens with different fiber content and obtains the relationship between the macro mechanical properties and the fiber content. At the same time, with the help of CT scanning equipment and digital image processing technology, the microstructure of basalt fiber concrete with three groups of fiber content is reconstructed, and the pore, crack, and fiber distribution are quantitatively described using the calculation and processing function of the Avizo reconstruction software. The results show that when the optimal fiber content is 3 kg/m³, the improvement rates of uniaxial compressive strength and splitting tensile strength are 31.9% and 23.7%, respectively. The network structure formed by fiber in concrete has the best compactness and the least number of pores, with an average sphericity of 0.89 and an average pore volume of 20.26 μm³. Through analysis, it was found that the initial defects of basalt fiber concrete exist in the form of pores, and the addition of basalt fiber will destroy the large pore size of concrete, change the pore size distribution, and increase the average sphericity; The distribution of the fiber in the concrete is a three-dimensional network, and the distribution of the fiber in the initial defect distribution area is parallel to the direction of pore arrangement.

The grouting method is often used to strengthen the bearing capacity of building foundations. In the process of grouting, the stress structure of slurry and rock and the soil mass under the condition of high permeability and high stress (“double height”) is complex, and the strength mechanism of slurry stone under different double-height conditions is not clear. Therefore, stone samples of grout under the curing pressures of 2 MPa, 4 MPa, 6 MPa, 8 MPa and 10 MPa were prepared for the uniaxial compression test to analyze the influence of curing pressure on compressive strength. The microstructure of the slurry stone was observed by scanning electron microscope, and the development law of microcracks was further studied using the particle flow program. The research shows that the strength of the slurry stone body increases with the increase of curing pressure. When the curing pressure increases from 2 MPa to 10 MPa, the compressive strength of the stone powder-cement slurry stone body increases from 8.3 MPa to 22.7 MPa, an increase of nearly 2.7 times, and the compressive strength of the clay-cement slurry stone body increases from 5.7 MPa to 16.8 MPa, an increase of 2.9 times. According to the axial compressive stress-strain curve of the specimen, the failure process goes through three continuous stages: continuous elasticity, crack propagation, and strength failure. When the stress peak is reached, the number of cracks increases slowly; when the stress peak is reached, the cracks expand rapidly, the number increases exponentially, and a penetrating main crack is finally formed, which destroys the specimen. This study provides a reliable basis for the selection of grouting parameters and grouting materials in stratum-grouting engineering.