为了研究易自燃煤体氧化后的力学特性变化，通过程序升温和热重实验获得煤氧化过程中的特征温度，并对煤样进行氧化处理;通过测试煤氧化前后的波速，得出氧化后煤体的损伤因子;通过单轴压缩实验，分析不同氧化煤的力学参数变化规律;通过建立氧化煤受力模型，分析不同氧化煤力学特性的差异并对典型工况研究。研究表明:① 原煤和70，135，200和265 ℃氧化后煤样的平均纵波波速分别为1 642，1 416，1 261，870和557 m/s，不同氧化煤的损伤因子平均值依次为0.19，0.43，0.72和0.86，随着氧化程度加深，波速降低，损伤因子变大;② 原煤应力-应变曲线表现出较好的线性特征，其压密阶段和屈服阶段不明显;随着氧化程度加深，氧化煤应力-应变曲线压密阶段和屈服阶段越明显，多峰效应越显著，峰后台阶跌落效应越突出，且峰后存在明显残余强度，其塑性增强;③ 随着氧化加深，抗压强度从16.36 MPa降至4.10 MPa，弹性模量从3.779降至0.437，割线模量从2.05降至0.19，初始模量从0.609降至0.082，泊松比从0.37降至0.25;氧化对煤体的抗压强度影响最明显，其软化系数从0.89降低至0.25，并提出了“氧化煤动态工程强度”的概念;④ 随着氧化程度的增加，煤样的峰值应变和压密阶段最大轴应变逐渐增加，压缩阶段最大轴应变与峰值应变比值越来越大，当氧化程度达到265 ℃后，其比值近50%;⑤ 随着氧化程度的加深，煤样的破坏形式趋复杂化，破坏后的完整性变差，破坏后脱落的碎煤及煤粉增多，并伴随产生“起皮”现象;⑥ 氧化煤体由外向内划分为强氧化区、弱氧化区和未氧化区，并建立了氧化煤体受力模型，计算得出70，135，200和265 ℃氧化后的煤样未氧化区域直径为44.44，37.24，16.84和0.06 mm，分析了氧化煤体力学性质差异机制，并对典型工况进行了数值模拟分析。

To study the changes in the mechanical properties of spontaneous combustion coal after oxidation,the characteristic temperatures in the process of coal oxidation were obtained by temperature programmed and thermogravimetric experiments,and the coal samples were oxidized.The damage factor of coal body after oxidation was obtained by testing the wave velocity of coal samples before and after oxidation.Through uniaxial compression test,the change law of mechanical parameters of different oxidized coal was analyzed.Through the establishment of the force model of oxidized coal,the difference of the mechanical properties of different oxidized coal was analyzed and the typical working conditions were studied.Through the above experimental study,the following results were obtained:① The average longitudinal wave velocities of raw coal and coal samples after oxidation at 70,135,200 and 265 ℃ are 1 642,1 416,1 261,870 and 557 m/s,respectively.The average values of damage factors of coal with different oxidation degrees are 0.19,0.43,0.72 and 0.86,respectively.With the increase of oxidation degree,the wave velocity decreases and the damage factor increases.② The stress strain curve of raw coal shows good linear characteristics,and its compaction stage and yield stage are not obvious.With the increase of oxidation degree,the more obvious the compression stage and yield stage of the stress strain curve of oxidized coal,the more obvious the multi peak effect,the more prominent the step drop effect behind the peak,and the obvious residual strength after the peak,and the plasticity of the oxidized coal increased.③ With the increase of oxidation degree,compressive strength decreases from 16.36 MPa to 4.10 MPa,average modulus decreases from 3.779 to 0.437,secant modulus decreases from 2.05 to 0.19,initial modulus decreases from 0.609 to 0.082,Poisson’s ratio decreases from 0.37 to 0.25.Oxidation has the most obvious effect on the compressive strength of coal,and its softening coefficient decreases from 0.89 to 0.25.The concept of “the dynamic engineering strength of oxidized coal” is put forward.④ With the increase of oxidation degree,the peak strain of the coal samples and the maximum axial strain in the compaction stage gradually increase,and the ratio of the maximum axial strain to the peak strain in the compression stage becomes larger and larger.When the oxidation degree reaches 265 ℃,the ratio is nearly 50%.⑤ With the deepening of oxidation degree,the form of coal samples destruction becomes more complicated,the integrity of the coal samples becomes worse after the destruction,the broken coal and coal powder that fall off after the destruction increases,accompanied by the phenomenon of “peeling”.⑥ The oxidized coal body is divided into strong oxidation area,weak oxidation area and non oxidation area from outside to inside,and the stress model of oxidized coal body is established.The results show that the diameter of unoxidized area is 44.44,37.24,16.84 and 0.06 mm after oxidation at 70,135,200 and 265 ℃.The difference mechanism of mechanical properties of oxidized coal body is constructed,and the typical working conditions are analyzed by numerical simulation.

1 煤样准备与氧化处理

   1.1 煤样准备

   1.2 煤体氧化处理

   1.3 实验设备及方案

2 实验结果分析

   2.1 氧化煤波速变化规律

   2.2 力学效应分析

3 力学性质差异机制分析

4 工程应用

   4.1 底抽巷抽采对被保护层影响

   4.2 煤柱局部氧化应力分布

5 结论