二维静载作用下含正交型交叉裂隙岩体动态力学特性研究

Research on dynamic mechanical properties of rock mass with orthogonal intersecting cracks under two-dimensional static loading

为研究围压对含交叉裂隙岩体的强度特征和破坏规律的影响,考虑裂隙贯通比、初始静载和应变率,基于双轴霍普金森压杆(biaxial Hopkinson pressure bar,BHPB)试验系统开展动静组合加载试验,并借助数字图像相关(digital image correlation,DIC)技术分析试样的变形过程,研究交叉裂隙岩体强度特征、能量耗散规律与断裂特性。研究结果表明:最大主应力方向的动态强度和峰值应变随着最大主应力或应力差的增大而减小,随中间主应力或者应变率的增大而增大,而中间主应力方向的动态应力和峰值应变显示出相反的变化趋势;随着差应力的增大,单位体积损耗能增加;随裂隙贯通比的增大,试样的动态强度减小,能量损耗率显著增加;主次裂隙贯通比决定试样的最终破坏模式,当裂隙贯通比较小时,交叉裂隙试样的起裂–扩展主要受主裂隙控制,当贯通比大于0.67时,主次裂隙相互作用明显,试样形成由主次裂隙、反翼裂纹、共面裂纹组成的多个破裂面;在双向等围压作用下,反翼裂纹在试样主次裂隙尖端贯通,最终呈剪切破坏;在双向不等围压情况下,试样呈现出与最小主应力方向近似垂直的分层剥离成块破坏,整体表现为压剪破坏。

In order to study the influence of confining pressure on the strength characteristics and failure characteristics of rock mass with cross cracks,considering the influence of crack penetration ratio,initial static load and strain rate,a biaxial dynamic and static combined loading test was carried out by using the biaxial Hopkinson pressure bar(BHPB)test system.The deformation process of the sample was analyzed with the help of digital image correlation(DIC)technology,and the strength characteristics,energy dissipation and fracture properties of crossjointed rock mass were studied.The research results show that the dynamic strength and peak strain in the direction of the maximum principal stress decrease with the increase of the maximum principal stress or stress difference,but increase with the increase of the intermediate principal stress or strain rate,while the dynamic stress and peak strain in the direction of the intermediate principal stress show the opposite trend.With the increase of the differential stress,the energy loss per unit volume increases.With the increase of the crack penetration ratio,the dynamic strength of the sample decreases,and the energy loss rate increases significantly.The primary and secondary crack penetration ratio determines the final failure mode of the sample,when the penetration ratio of the cracks is small,the crack initiation-expansion of the cross-jointed specimen is mainly controlled by the main cracks.When the penetration ratio is greater than 0.67,the interaction between the primary and secondary cracks is obvious,and the formation of the sample is composed of primary and secondary multiple fracture surfaces composed of anti-wing cracks and coplanar cracks.Under the action of bidirectional constant pressure,the anti-wing cracks penetrate at the tip of the primary and secondary cracks of the sample,and finally show shear failure.Under the two-way unequal confining pressure,the test sample presents delamination,peeling and block failure approximately perpendicular to the direction of the minimum principal stress,and the overall performance is compressive shear failure.