Study on the acoustic-thermal effects and damage models during uniaxial compression failure process of phosphorite with different H/Di

Abstract

Determining the size of ore pillars is crucial for the stability of mining structures and the recovery rate in mining design. To investigate the damage characteristics of phosphorite under different height-to-diameter ratios (H/Di), uniaxial compression tests were conducted on phosphorite specimens with varying H/Di. The effects of these H/Di on the mechanical properties and acoustic-thermal signals were analyzed, leading to the establishment of a joint acoustic emission-infrared damage model. Results showed: (1) Peak stress and ultimate strain of phosphorite specimens were negatively correlated with the H/Di, with compressive strength decreasing and stabilizing as the H/Di increased. (2) Increasing H/Di led to a transition from tensile to shear crack dominance during specimen failure, with cumulative acoustic emission energy and ringing counts positively correlated with H/Di. (3) Infrared radiation temperature before instability failure showed a cyclic pattern of slow increase, sudden rise, and sudden decrease, reaching a peak at failure. Using these findings, separate damage models for different H/Di were established based on two characteristic signals, correcting for monitoring losses, and finally merged into a joint acoustic-thermal damage model. The resulting model aligned well with experimental data, validating its rationality and significantly improving damage prediction accuracy. Thus, the model holds promising application prospects for calculating recovery rates, designing ore pillar sizes, managing goafs, and maintaining abandoned mine stability in phosphate mining design.