不同冲击倾向性煤单轴压缩下能量演化与损伤特征
Energy evolution and damage characteristics of coal with different bursting liability under uniaxial compression
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摘要: 为了研究不同冲击倾向性煤单轴压缩过程中的能量演化规律与损伤特征，基于实验室冲击倾向性等力学参数测试，通过颗粒流数值程序PFC2D获取能够较真实反映煤样宏观力学特性的细观参数，模拟分析了不同冲击倾向性煤单轴压缩下的能量演化规律与损伤特征。研究结果表明：不同冲击倾向性煤的能量演化规律相似，峰值强度前，边界做功主要转化为应变能，耗散能、滑动能与动能的占比则非常小；峰值强度后，应变能快速释放，耗散能、滑动能与动能开始迅速增长。随着冲击倾向性的增强，应变能释放与动能增长速率显著增大，提出应变能释放比率与动能增长比率2个指标，发现应变能释放比率、动能增长比率与冲击倾向性指标中的单轴抗压强度、冲击能量指数以及弹性能量指数具有很好的相关性，可采用该指标来辅助评判煤样的冲击倾向性。峰值强度前不同冲击倾向性煤样内部微裂纹演化规律近似，峰值强度点后微裂纹急剧增长，增速与冲击倾向性呈正相关关系。基于裂纹萌生与体积应变曲线的确定方法，得出煤的起裂应力水平主要分布在44.18%～51.67%，损伤应力水平在89.04%～93.86%。强冲击倾向性煤样的起裂应力水平与损伤应力水平均高于弱和无冲击倾向性煤样，起裂应力水平与损伤应力水平从细观损伤力学角度解释了强冲击倾向性煤样易积聚高弹性应变能并产生脆性冲击破坏的能力。Abstract: In order to study the energy evolution law and damage characteristics of coal with different bursting liability under uniaxial compression based on the laboratory bursting liability and other mechanical parameter tests, the mechanical parameters of the PFC models are calibrated so that the PFC models truly reflect the macro-mechanical properties of coal samples. The energy evolution law and damage characteristics of coal with different bursting tendency under uniaxial compression tests were simulated and analyzed. The results show that the energy evolution laws of different bursting liability coals are similar. Before the peak stress, the boundary work was mainly converted into strain energy, and the proportions of dissipation energy, sliding energy, and kinetic energy were very small. After the peak stress, the strain energy was quickly released. The dissipative energy, sliding energy and kinetic energy began to increase rapidly. With the increase of bursting tendency, the rate of strain energy release and kinetic energy significantly increases. Two indexes of strain energy release rate and kinetic energy growth rate are proposed.It was found that the strain energy release ratio and kinetic energy growth ratio have a good correlation with the uniaxial compressive strength, bursting energy index and elastic energy index. This index can be used to assist in evaluating the coal sample bursting tendency. The evolution of micro-cracks in coal samples with different bursting liability before peak strength is similar,and the micro-cracks grow rapidly after the peak intensity point, and the growth rate is positively correlated with the bursting liability. Based on the method of determining crack initiation and volume strain curve, it is concluded that the cracking initiation stress levels of coal are mainly distributed between 44.18% and 51.67%,and the damage stress level is between 89.04% and 93.86%.The initiation stress level and damage stress levelof the coal samples with strong bursting liability are higher than those of the weak and non-bursting liability coal samples. The initiation stress level and damage stress level reflects the ability of strong bursting liability coal samples to accumulate high elastic strain energy and produce brittle impact failure.
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Keywords:
- coal /
- bursting liability /
- energy evolution /
- damage /
- particle flow simulation
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