Study on acoustic emission and mechanical seepage characteristics of low temperature treated coal rock

In order to study the damage evolution law of coal and the influence of low temperature treatment on the mechanical and seepage properties of coal, the acoustic emission characteristics of coal samples during low temperature treatment and the mechanical and seepage properties of coal samples after low temperature treatment were analyzed through experimental tests. The results show that: when the normal temperature coal sample suddenly enters the low temperature environment, the AE signals are most dense and strong within 0-1 000 s, and gradually decrease and weaken in the middle and late period. Therefore, the damage mainly occurs in the first 1 000 s. With the decrease of the processing temperature, the number and intensity of AE signals of the coal sample increase significantly, and the distribution ratio of signal amplitude is roughly the same. It shows that the larger the temperature difference between coal and external environment, the higher the damage degree. The compressive strength, elastic modulus and Poisson’s ratio of coal samples treated at low temperature in the triaxial loading process are all reduced compared with those of normal temperature coal samples, and the decreasing amplitude is proportional to the low temperature treatment. The initial permeability of coal samples treated at 0 ℃, -20 ℃ and -40 ℃ increased by 8.15%, 23.46% and 74.87%, respectively, compared with normal temperature coal samples.