含非贯通裂隙砂岩的动力破坏特性研究

Dynamic failure characteristics of sandstone with non-penetrating cracks

为研究动载作用下非贯通裂隙对岩石破坏特性的影响,采用分离式霍普金森压杆(SHPB)对含不同裂隙数量及深度非贯通裂隙砂岩进行冲击试验,并基于分形理论和能量耗散原理分析其动力破坏特性。研究结果表明,动态峰值应力随裂隙数量及深度变化情况较复杂;峰值应变随裂隙数量增加而增加,随裂隙深度增加先增大后减小;动态弹性模量随裂隙数量增加先增加后减小,随裂隙深度增加而减小;不同工况试样的破坏模式分为张应变破坏、张应变-剪切复合破坏和压碎破坏3种,且裂隙数量对破坏模式的影响较裂隙深度大;试样破坏后的分形维数、单位体积耗散能和能量吸收率均随裂隙数量及深度的增加而增加,且分形维数与单位体积耗散能和能量吸收率均近似正线性关系。

In order to study the influence of non-penetrating cracks on rock failure characteristics under dynamic loading,splitting Hopkinson pressure bar(SHPB)is used to conduct impact tests on sandstones with different number and developed depth of non-penetrating cracks.The dynamic failure characteristics are analyzed based on fractal theory and energy dissipation principle.The results show that dynamic peak stress is more complicated in different number and developed depth of cracks.Peak strain increases with the increase in the number of cracks,and it increases at first and then decreases with the increase in the developed depth of cracks.Dynamic elastic modulus increases at first and then decreases with the increase in the number of cracks,but it decreases with the increase in the developed depth of cracks.The failure modes of specimens under different working conditions are mainly divided into three types,i.e.tension strain failure,tension strain-shear composite failure and crushing failure.The number of cracks has more significant influence on the failure mode than the developed depth of cracks.The fractal dimension,energy dissipation per unit volume and energy absorption rate of the rupturing rocks increase with the increase of the number and developed depth of cracks.Moreover,the fractal dimension and dissipation energy per unit volume are both approximately linear correlated with energy absorption rate.