This study uses laboratory tests and theoretical analysis to adopt a triaxial computer-controlled rock deformation system for studying the dynamic damage characteristics of coal during the process of coal seam water injection in a low-porosity coalbed. The effects of alternating hydraulic pressure on the mechanical properties and the damage evolution of coal under four different stress states are investigated. The results show the following: (1) Under the action of alternating hydraulic pressure, the process of damage and deformation of coal undergoes three deformation stages: initial damage, cumulative damage, and accelerated damage. The second and third stages develop rapidly, and cumulative deformation accounts for more than 90% of the total distortion. (2) Alternating hydraulic pressure has a specific destructive effect on coal, which is cumulative. After 1000 cycles, the limit value of the triaxial compressive strength is much lower than that after 50 alternating hydraulic pressure cycles. (3) With higher amplitudes of alternating hydraulic pressure, the stress generated inside the coal increases, and the coal experiences more damage. (4) Based on the principle of effective stress and mechanical fatigue theory, it can be found that alternating hydraulic pressure can enhance the strain stress sensitivity of coal.

本研究采用实验室测试和理论分析，采用三轴计算机控制的岩石变形系统，研究低孔隙度煤层注煤过程中煤的动态破坏特征。研究了在四个不同应力状态下交替液压对煤的力学性能和损伤演化的影响。结果表明：（1）在交替液压作用下，煤的破坏变形过程经历了初始破坏，累积破坏和加速破坏三个阶段。第二和第三阶段发展迅速，累积变形占总变形的90％以上。（2）交替液压对煤具有特定的破坏作用，这是累积的。在1000次循环后，三轴抗压强度的极限值远低于50次交替液压循环后的极限值。（3）随着交变水压振幅的增大，煤内部产生的应力增加，煤遭受的破坏更大。（4）基于有效应力原理和机械疲劳理论，发现交替的液压可以增强煤的应变应力敏感性。