为了研究低温液氮浸溶处理对淮南矿区中阶煤孔隙结构及其分形特征影响，采用不同液氮浸溶时间处理煤样，通过压汞法和液氮吸附法对煤体的孔隙结构加以测定，结合分形理论从多角度分析不同浸溶时间下煤体孔隙的发育规律及其尺度特征。结果表明：随着液氮浸溶时间的增加，煤体总孔容由198.089×10⁻³ cm³/g上升至371.553×10⁻³ cm³/g，总比表面积则由4.984 m²/g下降至4.496 m²/g，效果显著；煤体吸附孔减小，渗流孔增加，吸附孔的孔隙连通性增加形成更大级别的孔隙，逐渐向渗流孔转变；渗流孔分形维数和吸附孔分形维数与液氮浸溶时间呈现负线性相关，液氮浸溶对于渗流孔分形维数比对吸附孔分形维数的影响程度更为显著；渗流孔分形维数和吸附孔分形维数随着液氮浸溶时间的增大逐渐降低，表明了煤体内部孔隙随着液氮浸溶时间的增大结构复杂程度降低，孔隙之间的贯通性增强，煤体孔隙度和渗透性的增加；综合分形维数随着煤体平均孔径和总孔体积的增加而减小，随着总比表面积的增加而增加，随着液氮浸溶时间的增加，煤体综合分形维数下降，煤体的吸附能力有所减弱，渗流能力有所增强，有助于提升淮南矿区低渗煤层煤层气抽采效果。

In order to study the influence of low temperature liquid nitrogen immersion treatment on the pore structure and fractal characteristics of middle grade coal in Huainan Mining Area, coal samples were treated with different liquid nitrogen immersion time, and the pore structure of coal was measured by mercury injection and liquid nitrogen adsorption method. The fractal theory was combined to analyze the development law and scale characteristics of coal pores under different immersion time from multiple angles. The results show that with the increase of liquid nitrogen immersion time, the total pore volume of coal increases from 198.089×10⁻³ cm³/g to 371.553×10⁻³ cm³/g, while the total specific surface area decreases from 4.984 m²/g to 4.496 m²/g, and the effect is significant. The adsorption pore decreases, the seepage pore increases, and the pore connectivity of the adsorption pore increases to form a larger level of pore, which gradually changes to the seepage pore. There was a negative linear correlation between D₁ (fractal dimension of seepage pore) and D₂ (fractal dimension of adsorption pore) and the immersion time of liquid nitrogen, and the influence of liquid nitrogen immersion on D₁ was more significant than that of D₂. D₁ and D₂ decreased gradually with the increase of liquid nitrogen immersion time, indicating that the structural complexity of internal pores decreased with the increase of liquid nitrogen immersion time, and the porosity and permeability of coal increased. D_c (comprehensive fractal dimension) decreases with the increase of average pore diameter and total pore volume of coal body, and increases with the increase of total specific surface area. With the increase of liquid nitrogen immersion time, the comprehensive fractal dimension of coal body decreases, the adsorption capacity of coal body is weakened, and the seepage capacity is enhanced, which is helpful to improve the coal-bed methane extraction effect of low permeability coal seam in Huainan Mining Area.