Dynamic mechanical properties of deep coal rocks under three-dimensional dynamic and static loading

Gaining a comprehensive understanding of the dynamic mechanical properties of deep coal rock is highly important for ensuring the safe design and evaluation of coal rock engineering. This paper conducted triaxial coal samples using SHPB loading experiments on deep Using the split Hopkinson pressure bar to test coal samples test equipment, under various situations. The findings indicate that the stress-strain curves of coal subjected to coupled triaxial dynamic-static loading exhibit a consistent pattern. The stress-strain curves did not exhibit a compaction phase because of the initial axial prestress. Furthermore, the dynamic peak stress and secant modulus of the deep coal samples exhibited a linear increase as the constraint pressure and strain increased, followed by a decrease as the axial prestress increased. The threshold pressure for alterations in axial prestress is approximately 8 MPa (equivalent to 44% of the compressive strength). Amount of energy taken in by the deep coal samples during impact loading varies with the rise of axial static prestress at the same strain rate and confining pressure. Initially, it increases and then declines. Axial static tension grows as increased, the coal samples transitioned from experiencing shear damage to experiencing a combination of shear and tension damage. This study aims to provide guidance for preventing coal rock dynamic disasters and assessing the stability of mining engineering.