煤岩在冲击载荷下的动态力学特性对比分析

Comparison analysis on dynamic mechanics features of coal and rock under shock load

为了研究煤岩受爆炸、冲击等动态荷载下的破坏机理,利用50 mm的分离式霍普金森压杆(SHPB)试验系统,对无烟煤和砂岩试样进行不同冲击速率下冲击加载试验,基于应力波理论和分形理论,分别研究了无烟煤和砂岩在动态应力应变、破坏形态、破碎耗散能以及块度分形方面的差异。结果表明:无烟煤与砂岩的动态力学性能明显不同,无烟煤的动态应力应变在初始上升阶段就呈现出了很明显的非线性,并且冲击速率越小这种非线性越明显;而砂岩动态应力应变曲线在初始阶段基本是一条直线,具有线弹性;两者都具有随着冲击速率的增大,其塑性变形、极限强度也增大的趋势,但砂岩的塑性变形明显小于无烟煤的塑性变形。最后通过计算无烟煤、砂岩的破碎耗散能和分形维数可知:两者的破碎耗散能均随冲击速率的增大而呈弱幂函数关系增加,无烟煤的增长速率较快;无烟煤试样破碎块度的分形维数比较集中,随着冲击速度的增加砂岩分形维数有降低的趋势。

In order to study failure mechanism of coal and rock under explosion,impact and other dynamic load,a 50 mm separation type Split Hopkinson Pressure Bar test system was applied to impact load test under different impact speed on anthracite and sandstone samples. Based on stress wave theory and fractal theory,a study was conducted on differences of the anthracite and sandstone from dynamic stress and strain,failure mode,dissipated energy and block fractal. The results showed that dynamic mechanics performances of anthracite and sandstone were different obviously. The dynamic stress and strain of anthracite at initial rising stage would be nonlinear obviously. The smaller impact speed,the nonlinear would be more obvious. The dynamic stress and strain curve of sandstone was a straight line with linear elasticity at initial stage. With impact speed increased,both the plastic deformation and ultra strength would be in increasing tendency. The plastic deformation of the sandstone would be less than the plastic deformation of the anthracite coal. Finally,with calculation of anthracite and sandstone on dissipated energy and fractal dimension,both dissipated energy would be increased with the impact speed increased. The increased speed of anthracite would be fast. The fractal dimension of the anthracite coal sample broken size would be more concentrated.The fractal dimension of sandstone would be in a decreased tendency with the impact speed increased.