1. College of Safety Science & Engineering,Henan Polytechnic University,Jiaozuo　 454003,China; 2. The Collaborative Innovation Center of Coal Safety Pro-duction of Henan Province,Henan Polytechnic University,Jiaozuo　 454003,China; 3. State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University,Chongqing　 400044,China; 4. School of Mechanical and Power Engineering,Henan Polytechnic University,Jiaozuo　 454003,China

为探讨不同初始应力下卸荷煤体氧化特性,采用程序升温实验、煤岩三轴蠕变实验、压汞实验对易自燃原煤样及其不同初始应力下卸荷煤样进行微观氧化特性对比研究。结果表明:宏观方面,不同初始应力下卸荷煤体比原始煤样更容易氧化,特征温度点下各实验煤样的CO产生量-应变曲线与轴应力-应变曲线具有相似的规律,且煤样氧化能力随初始应力大小变化曲线呈"驼峰状",当初始应力达到15 MPa,煤岩处于塑性变形裂隙扩展阶段,煤样卸荷后与氧气接触能力显著增强;初始应力达到25 MPa,煤岩处于应变软化阶段,煤样卸荷后与氧气接触能力最强,间接增强了煤样的氧化能力。不同初始应力下卸荷煤体的特征温度点均提前于原始煤样,使得发生氧化自燃的时间提前。微观方面,煤体总孔容和孔径分布共同制约着氧化反应进程,初始应力使煤体的孔容积、孔径增大,小孔和微孔是O2与煤基质氧化反应区域的主要贡献者,小孔、微孔孔容值和比表面积随初始应力的变化趋势与实验煤样氧化能力随初始应力变化趋势相同。根据实验结果,随着煤层埋深增大,地应力增高,采动卸荷后煤体氧化危险程度增大;当煤层赋存地应力随埋深达到临界值后,采动卸荷后煤体氧化危险性程度将会降低;对于同一开采水平,应力相对集中区卸荷后煤体将更易发生氧化自燃,其氧化难易程度与煤体强度、赋存应力存在一定关联。

To study the oxidation characteristics of coal unloaded under different initial stress,in this paper,a compara- tive study on the micro-oxidation characteristics of the raw coal samples with easy spontaneous combustion and the un- loaded coal samples under different initial stress was carried out by using the temperature-programmed experiment,the three axial creep test of coal rock and the mercury injection experiment. The findings indicate that in the macroscopic aspects,the unloaded coal under different initial stresses is easier to oxidize than the raw coal samples,the CO produc- tion-strain curve of the experimental coal samples is similar to the axial stress-strain curve and the coal oxidation capacity changes in the “Hump” with the initial stress,When the initial stress reaches 15 MPa and the coal rock is in the stage of plastic deformation crack propagation,the contact ability of the coal sample after unloaded is significantly enhanced. When the initial stress reaches 25 MPa,the coal sample is in the stage of strain softening,the contact ability of the coal sample after unloaded is the strongest. The characteristic temperature of the experimental coal samples is a- head of the raw coal samples,that is,the period of spontaneous combustion is getting earlier. In the micro aspects,the coal total pore volume and pore size distribution collaboratively restrict oxidation reaction process,the initial stress makes the pore volume and pore size of the experimental coal samples increases,the small pore and micropore is the main contribution of O2 and coal matrix oxidation reaction area. The variation trend of volume of small pore micropore, and specific surface area with the initial stress is the same as the oxidative capacity of the experimental coal with the initial stress. Based on the experimental results,with increasing depth,the in-situ stress increased,the danger degree of coal oxidation will increase after mining unloaded. When the stress in coal seam reaches a certain critical value with the burial depth,mining coal oxidation degree of risk will be reduced after unloaded. For the same level of mining,the spontaneous combustion of coal is easier to occur when the stress is relative concentration,the difficulty degree of coal mining at the initial stage of oxidation is related to the strength of coal and the occurrence of stress.

国家自然科学基金资助项目(51304070；51674103；U1361205)；

PAN Rongkun,CHEN Lei,YU Minggao,et al. Oxidation characteristics of unloaded coal under different initial stress[J]. Journal of China Coal Society,2017,42(9):2369-2375.