To comprehensively understand the differences in mechanical behavior of coal during the mining process at different depths, cyclic triaxial loading and unloading (CTLU) experiments with acoustic emission (AE) monitoring were performed on coal samples collected at 5 depths (300, 600, 700, 850 and 1050 m). The results showed that with increasing depth, the strength and deformation of the coal increased, the evolution of the Poisson's ratio presented a nonlinear increase, the evolution of the elastic modulus gradually changed from “first stable and then decreasing” at shallow depths to a “continuous decrease” at deep depths, and the plastic deformation and progressive damage characteristics of the coal became more significant. The AE evolution characteristics of the studied coal samples were analyzed in detail, and the depth differences of coal failure mechanisms were revealed through a comprehensive analysis of combined AE parameters and the spatial aggregation characteristics of the microcracks. The failure of the shallow coal samples was mainly controlled by tensile cracking, while that of the deep coal samples was controlled by shear cracking. Meanwhile, the energy evolution and partition characteristics of the studied coal samples were investigated; clearly, with increasing depth, the storage capacity of the elastic strain energy increased, the release of which became more incomplete, and the mutation point of the energy conversion process was relatively advanced. Additionally, the change in the coal damage evolution with depth was studied based on the cumulative dissipated energy; it was found that the damage development process of deeper coal was slower, but the damage degree was more serious. Finally, an improved damage model considering the depth effect was established based on strain energy, and the model prediction curves agreed well with the testing values.

为全面了解煤在不同深度开采过程中的力学行为差异，对在 5 个深度（300、600、700、300、600、700、 850 和 1050 米）。结果表明，随着深度的增加，煤的强度和变形量增加，泊松比的演化呈现非线性增加，弹性模量的演化逐渐由浅层的“先稳定后下降”转变为“深度持续减小”，煤的塑性变形和渐进破坏特征更加显着。详细分析了所研究煤样的AE演化特征，结合声发射参数和微裂纹的空间聚集特征综合分析，揭示了煤体破坏机制的深度差异。浅层煤样的破坏主要受拉裂控制，而深层煤样的破坏主要受剪切开裂控制。同时，研究了所研究煤样的能量演化和分配特征；可见，随着深度的增加，弹性应变能的储存量增加，释放更加不完全，能量转换过程的突变点相对提前。此外，基于累积耗散能研究了煤层损伤随深度的变化；发现越深的煤层损害发展过程越慢，但损害程度越严重。最后，基于应变能建立了考虑深度效应的改进损伤模型，模型预测曲线与试验值吻合较好。