Experimental study on deformation and acoustic emission characteristics of low-temperature frozen raw coal under uniaxial compression

Uniaxial compression was performed on frozen and untreated frozen coal samples under natural and natural saturated conditions. The strength and deformation characteristics of coal samples were analyzed, and the AE characteristics and damage evolution were analyzed during the loading process. The result shows that the compressive strength of natural and saturated coal samples after low-temperature freezing decrease by 13.93% and 25.02%, respectively. The deformation characteristics and hit rate evolution are basically unchanged, but the slope of the stress-strain curve decrease during the compaction stage. The maximum hit rate increases by 10.20% and 22.45%, respectively. The damage evolution of coal samples in the three conditions can be divided into initial damage stage, slow damage stage, fast damage stage and post-peak damage stage, but the post-peak damage stage is significantly shortened after low-temperature freezing treatment. The damage evolution of coal samples at the peak load is obviously different after low temperature freezing treatment, and it rises in multiple steps in the natural state, while it rises in a single step after freezing treatment. The damage grows faster, the corresponding damage is more severe, and the coal sample is more broken.