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为研究煤的动态破坏特征,利用霍普金森压杆(SHPB)实验系统开展了不同应变率下的煤样冲击实验,分析了煤动态力学特性及其力学参数随应变率的变化规律,研究了煤样破坏形式,并利用分形理论定量描述了煤破坏后的自相似性。研究结果表明:煤的动态应力-应变曲线基本不存在下凹段,可划分为线弹性阶段、弹塑性阶段和塑性软化3个阶段;煤的平均应变率和最大应变率随冲击气压的增加符合指数增长规律,动态弹性模量和动态抗压强度随应变率遵循线性变化规律;冲击载荷作用下,煤的破坏主要以劈裂破坏和碎裂破坏2种形式出现,且破碎后的形态具有明显的自相似性,其分形维数随应变率线性增加;动态抗压强度、弹性模量与分形维数近似正相关关系。研究结果对于解决当前深部矿山采掘等工程实际问题具有一定的理论意义和实用价值。
In order to study the dynamic destruction characteristics of coal, the Hopkinson pressure bar (SHPB) experimental system was used to carry out coal sample impact experiments at different strain rates. The dynamic mechanical properties of coal and its variation with strain rate were analyzed. The destruction form of coal sample and the fractal theory are used to quantitatively describe the self-similarity after coal failure. The results show that there are basically no concave sections in the dynamic stress-strain curves of coal, which can be divided into three stages: linear elastic stage, elastoplastic stage and plastic softening. The average strain rate and maximum strain rate of coal conform to the increase of impact pressure The law of exponential growth, dynamic elastic modulus and dynamic compressive strength follow the linear change law with strain rate. Under the impact load, the destruction of coal mainly appears in the form of splitting failure and fragmentation, and the morphology after crushing is obvious The fractal dimension increases linearly with the strain rate. The dynamic compressive strength, elastic modulus and fractal dimension have approximate positive correlation. The research results have certain theoretical significance and practical value for solving the practical problems in the current mining of deep mines.