Study on the damage law of coal rock affected by different alternating periods of cold and heat

Temperature is an important factor affecting the physical properties of coal and rock, and as a solid medium, coal and rock have the properties of thermal expansion and contraction. The alternation of cold and heat will cause irreversible damage to the coal rock due to deformation, which will eventually lead to the damage and destruction of the original fracture structure of the coal rock. In order to study the damage law of coal and rock affected by different alternating cycles of cold and heat, the long-flame coal in Fuxin area of Liaoning Province was selected to make a cube specimen with a size of 100 mm×100 mm×100 mm. The mechanical parameters and surface dimensions of the coal samples before and after the experiment were measured by using the research method of reciprocating the application of temperature loads in a low temperature storage box(–15 °C) and room temperature(20 °C). Furthermore, the expansion law and damage mechanism of the coal sample fracture structure with the alternating cycle of cooling and heating are revealed. The results show ① The coal sample cracks expand and expand under the alternating action of cold and heat, and the expansion amount and expansion rate of the cracks on the surface of the coal sample gradually increase with the cycle of the alternating cycle of cold and heat. ② The mechanical properties of coal samples are weakened under the action of multi-cycle temperature loads, the damage is serious, and the compressive strength of coal samples gradually decreases with the cycle of alternating cycles of cold and heat. ③ The damage mechanics model of coal sample structure is established by ABAQUS software, and the simulation results are in good agreement with the experimental results. The overall structural damage degree of the coal sample is aggravated, indicating that the alternating action of cold and heat is an important factor for the structural damage of the coal sample.