In order to investigate the effect of deep burial metamorphism on the wettability of coal during deep burial metamorphism, a superficial coal sample (∼90 m) and a deep coal sample (∼490 m) collected from two main mining seams were selected to simulate the deep burial metamorphism process. The wettability of two coal samples during deep burial metamorphism was investigated by X-ray photoelectron spectroscopy (XPS), FTIR, zeta potential, and contact angle measurements. Besides, comprehensive DLVO interaction analyses between two coal samples from different mining depths were carried out through the zeta potentials measurements under different pH values. The XPS results demonstrate that the content of surface oxygen atom and oxygen-containing functional group for superficial coal tends to be higher than that of deep coal. The FTIR results indicate that the peak intensity of oxygen-containing functional groups for the superficial is higher than that of deep coal, implying the stronger surface hydrophobicity of deep coal compared to superficial coal. The contact angle of superficial coal is lower than that of deep coal. The zeta potential and DLVO theory analyses of superficial particles and deep coal particles indicate that deep burial metamorphism process might be favorable for bubble-particle collision and attachment, while might be unfavorable for the wetting process oppositely. Based on the surface chemistry characterization and theory analyses, this study is expected to give a theoretical insight into the efficient processing or dedusting process of coals experiencing different deep burial metamorphism processes in the future.

Cement paste backfill (CPB) suffers serious damage and deterioration under the dual erosion conditions of the dry–wet cycle caused by the high chloride salt concentration in mine water and the fluctuation of mine water level. In order to discuss the mechanical properties and permeability characteristics of CPB under erosion, this study designs an immersion experiment for CPB under chloride salt and dry–wet cycle conditions. Through a uniaxial compressive strength (UCS) test, the change law for the mechanical parameters of the CPB was investigated, the strength constitutive equation of the CPB was constructed and the deterioration process of the CPB was analyzed. The penetration test was used to investigate the diffusion characteristics of the packing under chloride salt and dry–wet cycle conditions. The results showed that the strength and Young’s modulus of the CPB initially increased and then rapidly decreased, with maximum decrease rates of 32.2% and 38.2%, respectively. The CPB structure exhibits an initial undamaged stage, an initial damaged stage, a damaged development stage, a damaged destruction stage and a residual damaged stage. The chloride ion penetration depth gradually increased with the number of dry–wet cycles, with a maximum diffusion depth of 20.5 mm. The maximum apparent diffusion coefficient of chloride ion was 18.99 × 10⁻¹⁰ m²/s, and the maximum concentration was 0.303 mol/L. Under the double erosion conditions of chloride salt and dry–wet cycle, the CPB structure was severely damaged.

To achieve effective consolidation of fine particles in moraine and enhance the freeze-thaw resistance of the consolidated body, this study developed a novel grouting material using sodium silicate, lipid-based curing agents, and acidic catalysts. The gelation time and rheological properties of this material were tested. The freeze-thaw resistance was studied through changes in uniaxial compressive strength (UCS) after freeze-thaw cycles, while the consolidation mechanism was analyzed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The experimental results indicate that the material’s gelation time can be controlled between 30s and 1600s, with an initial viscosity ranging from 5.9 to 9.8 mPa·s. Predictive models for these two indicators were established, and variance analysis revealed the influence ranking for gelation time: phosphoric acid dosage had the greatest effect, followed by EGDA content, with the Baume degree of sodium silicate having the least effect. The initial viscosity positively correlated with the Baume degree of sodium silicate and exhibited exponential growth over time. EGDA addition enhanced UCS by over 450%, reaching 1.2 MPa. During freeze-thaw cycles, strength degradation of the consolidated body was reduced by 10% to 30%. Microstructural tests showed that EGDA promotes silica gel formation and creates a network structure with unreacted sodium silicate, forming a dense consolidated body with moraine fine particles, thereby enhancing freeze-thaw resistance. These findings provide design references and theoretical support for moraine grouting in cold regions.

The clean filling pipe can ensure sufficient overflow section, reduce paste transport resistance, and avoid slurry deposition. The introduction of compressed gas into the pipe flushing can improve the flushing effect and efficiency of the pipe and reduce water consumption. However, the dominant factors influencing water consumption water consumption are not well understood. The purpose of this study is to determine the effect of flow velocity, backfill gradient (4–7), gas void fraction (0–1), and gas pressure (0–0.7 MPa) on water consumption. Water consumption was obtained experimentally by modeling the gas–water flushing pipe. The criterion for the completion of pipeline cleaning is to reduce the water solid content of the flushing pipeline from the initial value to 1%. A model was established to predict water consumption, which was validated by industrial tests. The results show that the water consumption of the flushing pipe increased with the power law as the backfill gradient increased and decreased with the increase of gas void fraction, gas pressure, and flow velocity. The water consumption is 0.8–1.1 times the volume of the pipe in water flushing. However, the water consumption of gas–water flushing is 0.60–0.75 times the volume of the pipe. Gas–water flushing can reduce water consumption by up to 30%. The findings are conducive to design pipe flushing parameters to avoid excessive water consumption.