加卸载煤体损伤-渗透特性影响因素实验研究

深部煤层开采过程中，多重因素影响着煤体损伤-渗透特性。为揭示采动煤体损伤-渗透特性演化规律，开展了不同工程条件代表的恒围压加轴压(路径1)、恒轴压卸围压(路径2)和同时加轴压卸围压(路径3)3种力学路径下煤体损伤-渗透实验，分析加卸载方式、轴压加载速率、围压卸荷速率以及围压等因素对型煤煤体损伤-渗透特性的影响规律。结果表明，不同加卸载方式显著影响着试样损伤程度，按严重程度排序依次是:路径1＜路径2＜路径3；试样的抗压强度随加卸载速率的增高而较快达到，损伤程度和渗透率增幅却随之增高；随着围压的增高，损伤的时间响应变慢，渗透率最终恢复程度降低，煤体的损伤、渗透特性具有显著的围压效应。能量累计量随时间的变化呈指数函数关系，损伤扩容后相对渗透率k/k₀呈幂函数关系。

Experimental study on influence factors in damage-permeability characteristics of loading and unloading coal

In the process of deep coal seam mining, multiple factors affect the coal body damage-permeability characteristics.In order to reveal the evolution law of coal mining damage-permeability characteristics, the coal damage-permeability experiments under three mechanical paths of fixed confining pressure and increased axial pressure (path 1), fixed axial pressure and decreased confining pressure (path 2), increased axial pressure and decreased confining pressure (path 3) were carried out under different engineering conditions.Then the influence of factors such as loading and unloading methods, axial pressure loading rate, confining pressure unloading rate, and confining pressure on coal damage-permeability characteristics were analyzed.The results show that the different loading and unloading methods significantly affect the degree of sample damage, whose order is: path 1 < path 2 < path 3.The compressive strength of samples is easier to achieve with an increased rate of loading and unloading, but the extent of damage and permeability increase along with it.With the increase of confining pressure, the time response of damage becomes slow and the ultimate recovery degree of permeability decreases.The damage and permeability characteristics of coal have significant confining pressure effects.The cumulative amount of energy changes with time in an exponential function, and the relative permeability k/k₀ after damage expansion is in a power function.