Mechanism and prediction of anchor rod strength degradation with deep mine high-stress corrosion environment

Deep coal mining, in addition to facing the three “high” and one “disturbance”, faces a high-stress corrosion environment formed by underground corrosive atmosphere, high stress, strong disturbance, and other factors. Taking the deep mines in the Juye Coalfield, Shandong, as the engineering background, the high-stress corrosion characteristics and influencing factors of deep mining are analyzed. Experimental and theoretical research is conducted on the anchor rod material to reveal the degradation mechanism of anchor rod strength under high-stress corrosion environment, and a theoretical model for the degradation of rod strength is derived. The results are as follows: ① through the SEM, corrosion SSRT, and accelerated corrosion experiments on rod materials, it is found that the corrosion causes a decrease in the elongation at break and fracture time of rod materials by 8.22% and 8.34%, respectively, compared to inert conditions. With the increase of corrosion rate, the material failure mode transitions from ductile to brittle fracture, and the localized corrosion type gradually evolves from pitting to uniform corrosion. ② Combining experimental results with electrochemical theory and non-uniform corrosion models, introducing the Pruckenr temperature influence factor, a time-varying model for the degradation of rod material strength is derived. The in-depth investigation of the impact of service environment temperature T, rod cross-sectional radius R, and material room temperature corrosion rate V_h,298K on the service life of the rod reveals that R is linearly positively correlated with service life. The relationship between T and V_h,298K with service life shows that the degree of service life decay decreases as the levels of influencing factors increase. ③ Combining experimental results with the energy absorption principle of anchor rods, the limit energy absorption capacity of roadway anchor rod support is calculated and analyzed. The results show that as the corrosion rate of the anchor rod increases, the energy absorption of the anchor rod decreases, the maximum seismic resistance decreases, and the risk of roadway dynamic instability disasters increases.