Abstract Gas extraction in destressed coal seams is one of the effective measures to improve degasification efficiency and reduce gas disasters in deep coal seams. In order to reveal the influence of damage zone induced by stress relief on gas extraction of slotted boreholes, a multi-field model incorporating stress, damage, gas diffusion and gas flow in heterogeneous coal was established. By using this model, the stress relief induced coal damage around slotted boreholes was simulated with the example of Guhanshan Coal Mine. Besides, the effects of homogeneity coefficient, Langmuir volumetric strain constant and overburden stress on coal seam damage and gas extraction were analyzed. The following results were drawn: The rationality and engineering applicability of the model were verified by comparing the numerical simulated results with the field test data in Guhanshan Coal Mine. The stress relief induced coal damage zone around slotted boreholes rises gradually with the increase of the homogeneity coefficient and overburden stress, and the coal seam permeability rises gradually with the increase of Langmuir volumetric strain constant and the decrease of overburden stress. The reasonable borehole distance is determined to be 8 m which is obtained based on the variations of total gas production and gas pressure with different borehole distances. Therefore, reasonable borehole distances under varying conditions can be determined by integrating different geological conditions of coalmines with the proposed simulation method. The simulation results can provide theoretical guidance for the layout of stress relief boreholes and the improvement of gas extraction efficiency in the future.

中文翻译：

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考虑应力释放损伤的水力开槽扰动煤层气体流动

摘要 脱应力煤层瓦斯抽采是提高深部煤层脱气效率、减少瓦斯灾害的有效措施之一。为揭示应力消除引起的损伤带对槽眼瓦斯抽采的影响，建立了非均质煤中应力、损伤、瓦斯扩散和气流的多场模型。利用该模型，以古汉山煤矿为例，对槽缝钻孔周围应力消除引起的煤损进行了模拟。分析了均质系数、Langmuir体积应变常数和上覆应力对煤层损伤和瓦斯抽采的影响。得出以下结果：通过数值模拟结果与古寒山煤矿现场试验数据的对比，验证了模型的合理性和工程适用性。随着均质系数和上覆应力的增大，开槽钻孔周围的应力消除诱导煤损伤带逐渐升高，随着Langmuir体积应变常数的增大和上覆应力的减小，煤层渗透率逐渐升高。合理井距确定为8 m，这是根据不同井距下总产气量和瓦斯压力的变化得出的。因此，通过将不同的煤矿地质条件与所提出的模拟方法相结合，可以确定不同条件下的合理钻孔距离。