冲击载荷作用下煤的破坏特性试验研究

The failure characteristics of coal under impact load in laboratory

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 failure properties of coal, impact tests of coal under different strain rates were carried out through Split Hopkinson Pressure Bar （SHPB）. The dynamic mechanical characteristics of coal and the changes of mechanical parameters were analyzed, the failure forms of coal were studied, and the self-similarity features of coal under impacting failure were described quan- titatively through fractal theory. The results have shown that there is basically no sunken section in the dynamic stress-strain curves and the curve can be divided three phases： the phase of linear elasticity, the phase of elastoplasticity, and the phase of plastic softening; the laws of average and maximum strain rate are in exponent with the increase of air pressure, and the dynamic elasticity modulus and compressive strength increase linearly with the strain rate; coal under impact loading has two failure forms of cleav- age and fragmentation; the obvious self-similarity of failure coal is found and fractal dimensions in- crease linearly with the strain rate; the relationship between dynamic compressive strength and elastic modulus are approximately positive correlation. The research results have a certain theoretical and prac-tical value to solving practical problems in deep mining.