岩石冲击破碎块度分形与能量耗散特征研究

Study on Fractal and Energy Dissipation Characteristics of Rock Impact Fragmentation

为研究冲击荷载作用下岩石能量吸收与破碎分形特征,应用霍普金森试验系统对0.6、0.8、1.0、1.2、1.4长径比花岗岩进行动态冲击试验,分析了应变率效应和尺寸效应对花岗岩试件的破碎能耗和破坏形态的影响;在考虑时间因素的基础上,提出一种新的能时密度指标来评价能量耗散,结合分形维数计算与能时密度分析,研究岩石在冲击过程中的能时密度与分形特征。结果表明:0.6~1.4长径比花岗岩试件的应变率和能时密度均符合乘幂关系,同种长径比试件的能时密度随应变率增大呈递增趋势;在48.8~124.2 s^(-1)应变率区间内,分形维数随应变率增加显著增大;花岗岩试件在动荷载下的能时密度和分形维数符合乘幂关系,单位时间内岩石吸收能量越多,分形特征就越明显;引用能时密度结合岩石破碎块度的分形维数计算,能够定量研究岩石单位时间内的能量吸收规律。

In order to study the rock energy absorption and fractal characteristics of crushing under impact load,the dynamic impact tests of granite with aspect ratios of 0.6,0.8,1.0,1.2,and 1.4 were carried out by split Hopkinson bar.The effects of strain rate effect and size effect on the crushing energy consumption and failure mode of granite specimens were analyzed.On the basis of considering the time factor,a new energy time density index is proposed to evaluate the energy dissipation.Combined with fractal dimension calculation and energy time density analysis,the energy time density and fractal characteristics of rocks during the impact process are studied.The results showed that the strain rate and energy-time density of the granite specimens with an aspect ratio of 0.6 to 1.4 are in line with the power relationship,and the energy-time density of the specimens with the same aspect ratio increases with the increase of the strain rate.In the strain rate range of 48.8~124.2 s^(-1),the fractal dimension increases significantly with the increase of the strain rate,the energy-time density and fractal dimension of the granite specimen under dynamic load conform to a power relationship,and the more energy absorbed by the rock per unit time,the more obvious the fractal characteristics.The energy-time density combined with the fractal dimension calculation of rock fragmentation can quantitatively study the energy absorption law of rock per unit time.