波阻抗对岩石动力学特性影响的模拟试验研究

利用分离式霍普金森压杆(SHPB)试验系统,对系列波阻抗的模型材料进行不同应变率下的冲击压缩试验。试验结果表明:岩石在冲击荷载下的应力波传播特征、动态应力应变关系以及破碎块度分形特征同时受波阻抗、应变率和冲击速度的影响。波阻抗相同时,反射波和透射波信号幅值均随冲击速度增大呈线性增大,同时应变率效应明显,随着应变率的增大:峰值应力呈线性增大,动态弹性模量增大,应变软化阶段延长;破碎程度增大,破碎块度分形维数呈线性增大。应变率相同时,随着波阻抗的减小:反射波幅值增大、透射波幅值减小;峰值应力减小,应变软化阶段延长,塑性段趋于明显,且有塑性流动现象出现;破碎程度增大,破碎块度分形维数增大。同时随着波阻抗减小,应变率增大对动态抗压强度的增大以及对破碎程度的加剧效果减弱,应变率效应减弱,逐渐趋于不明显。

Tests for effects of wave impedance on rock’s dynamic performance

A series of impact compression tests were conducted on model materials with different wave impedances under different strain rates using the split-Hopkinson pressure bar (SHPB) test system.The test results showed that under impact load, rock’s stress wave propagation characteristics, dynamic stress-strain relation and fractal features of rock fragmentation are affected by wave impedance, strain rate and impact velocity; when wave impedance is the same, amplitudes of reflected wave and transmitted one increase linearly with increase in impact velocity; at the same time, effect of strain rate is obvious, with increase in strain rate, peak stress increases linearly, dynamic elastic modulus increases, and strain softening stage prolongs; when crushing degree increases, fractal dimension of fragmentations increases linearly; when strain rate is the same, with decease in wave impedance, amplitude of reflected wave increases and transmitted one’s decreases; when peak stress decreases, strain softening stage prolongs, plastic stage tends to be obvious, and plastic flow phenomenon appears; when crushing degree increases, fractal dimension of fragmentations increases; with decrease in wave impedance, effect of increase in strain rate on increase in dynamic anti-compression intensity and enhancing degree of crushing weakens, strain rate’s effect weakens and gradually tends to be unconspicuous.