Tong Gao

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.

To eliminate the massive accumulation of tailings and promote the recycling of mine solid waste to develop green mining, a two-layered cemented paste backfill (CPB) with layering angles of 5°, 10°, 15°, 20° and 25° and complete CPB were prepared to conduct direct shear experiments; thus, the effect of the layering angle on their shear mechanical properties can be investigated. Meanwhile, the particle flow analysis program PFC 2D was used to simulate the micro-crack propagation law and reveal the damage mechanism. The results showed that the layered structure weakens the integrity of CPB and significantly reduces its shear strength, cohesion and internal friction angle. When the layered angle increased from 20° to 25°, the shear strength under normal stress of 100 kPa was decreased by 35.13% and cohesion by 43.43%. As the layered angle increased from 5° to 25°, the internal friction angle decreased first and then increased and reached the minimum when the layered angle was 15°. With the increase in the layered angle, the layered CPB gradually generated tension cracks along the layered surface, and the number of cracks gradually increased. The failure mode of each specimen is mainly a shear crack through the shear surface failure, crack expansion in the middle of shear surface on the upper and lower sides of the spindle-shaped failure and an inverted Z-shaped conjugate shear failure. This research can provide a substantial reference in the design and application of layered CPB in underground mines.