Study on the microscopic mechanism of performance degradation law of resin anchoring agent in high ground temperature environment

In deep coal mining, the high ground temperature environment causes instability of the anchoring support structure, which seriously threatens the safe and efficient mining of coal mines, and the performance of resin anchoring agents exerts a significant influence on this issue. Therefore, an in-depth study was conducted on the performance evolution of resin anchoring agents in a high ground temperature environment. First, laboratory tests were carried out to simulate different ground temperature conditions, and the gelling time, viscosity, compressive strength and pull-out force of resin anchoring agents were measured. Combined with digital image correlation (DIC) technology and scanning electron microscopy analysis, it is found that with the increase of temperature, the gelling time of anchoring agents is shortened, the viscosity is increased, and the uniaxial compressive strength and pull-out force decrease significantly, indicating an obvious deterioration of mechanical properties. Second, molecular dynamics simulation was adopted to analyze the effect of temperature on the intrinsic strength of resin anchoring agents and the performance of the surrounding rock-anchoring agent interface. The results reveal that increasing temperature enlarges the free volume of the resin: the free volume fraction rises from 38.3% to 40% under the conditions of 303.15 K (30℃) to 363.15 K (90℃). Meanwhile, the mean square displacement of resin chain end increases, the diffusion capacity is enhanced, and the interfacial interaction energy is reduced, thereby weakening the bonding strength. Finally, a synergistic control strategy incorporating material modification, anchoring interface strengthening, and construction process adaptation is specifically proposed to enhance the resin anchoring support strength in high geothermal environments, thereby providing technical support for the safe and efficient mining of deep coal mines.