单轴压缩下低温冷冻原煤的变形及声发射特征试验研究
Experimental study on deformation and acoustic emission characteristics of low-temperature frozen raw coal under uniaxial compression
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摘要: 分别对自然和自然饱水状态下冷冻处理后及未经冷冻处理的煤样开展单轴压缩声发射试验,分析了煤样的强度及变形特征,并对加载过程中的声发射特征与损伤演化规律展开分析。研究表明:低温冷冻后自然和饱水煤样的抗压强度会降低,分别降低13.93%和25.02%;其变形特征和撞击率演化规律基本不变,但压密阶段应力-应变曲线斜率会降低,且最大撞击率会出现增高,分别增加10.20%和22.45%;3种状态下煤样损伤演化规律依次可分为初始损伤阶段、损伤缓慢阶段、快速损伤阶段和峰后损伤阶段,但低温冷冻处理后峰后损伤阶段明显缩短;低温冷冻处理后煤样在峰值载荷处损伤演化明显不同,自然状态下呈多级台阶上升;而冷冻处理后呈单级台阶上升,损伤增长较快,对应破坏越剧烈,煤样破碎程度越高。Abstract: Uniaxial compression was performed on frozen and untreated frozen coal samples under natural and natural saturated conditions. The strength and deformation characteristics of coal samples were analyzed, and the AE characteristics and damage evolution were analyzed during the loading process. The result shows that the compressive strength of natural and saturated coal samples after low-temperature freezing decrease by 13.93% and 25.02%, respectively. The deformation characteristics and hit rate evolution are basically unchanged, but the slope of the stress-strain curve decrease during the compaction stage. The maximum hit rate increases by 10.20% and 22.45%, respectively. The damage evolution of coal samples in the three conditions can be divided into initial damage stage, slow damage stage, fast damage stage and post-peak damage stage, but the post-peak damage stage is significantly shortened after low-temperature freezing treatment. The damage evolution of coal samples at the peak load is obviously different after low temperature freezing treatment, and it rises in multiple steps in the natural state, while it rises in a single step after freezing treatment. The damage grows faster, the corresponding damage is more severe, and the coal sample is more broken.