高应变率下预制单节理岩石SHPB劈裂试验能量耗散分析

应用SHPB试验装置研究预制单节理岩石的能量耗散关系。使用SHPB试验系统,对高径比为0.5的完整花岗岩试样及预制单节理花岗岩试样进行高应变率下的冲击劈裂试验。在相同驱动气压下,改变加载方向与节理间的夹角,完成高应变率相同入射能下的冲击劈裂试验。对SHPB系统中的入射能、反射能、透射能及试样吸收能的时程变化规律进行了分析;从能量角度出发,分析冲击荷载作用下单节理岩石的能量耗散规律及其各向异性特征。结果表明:高应变率下,完整花岗岩试样在冲击劈裂试验中的吸收能随平均应变率增加而增加,表现出显著的应变率相关性;预制单节理岩石与加载方向之间夹角对破坏模式的影响明显,节理试样产生3种破坏模式:(1)穿越节理面的劈裂破坏;(2)沿节理岩石层面的滑移破坏;(3)劈裂与滑移破坏共同作用下的破坏。在入射能基本相同,入射时间较长时节理岩石试样吸收能较入射时间较短时的吸收能大。动态劈裂试验中,节理试样的吸收能随节理角度变化(0°~90°)近似呈U型。研究成果可为节理岩石动态力学性能研究提供参考。

Energy dissipation of rock specimens under high strain rate with single joint in SHPB tensile tests

The energy dissipation in single jointed rocks under high strain rate is investigated by the split-Hopkinson pressure bar (SHPB) technique. The dynamic split tensile tests on both intact granite specimens and man-made single jointed granite specimens with a thickness-diameter ratio of 0.5 are carried out. The compressive analysis on the temporal responses of incident energy, reflection energy, transmission energy and absorbed energy stored in the rock specimens is performed. The anisotropy characteristics of energy dissipation of the jointed rock are discussed based on the analysis of energy distribution. The results show that the absorbed energy of rock specimens in SHPB tests increases with the increment of strain rate. The fracture modes of jointed granite with different angles are different from each other. There are three kinds of fracture modes: sliding failure along the joint, combination of splitting failure and slide failure, and splitting failure. When the incident energy stays constant, the absorbed energy with shorter incident time is less than that with longer incident time. The distribution of absorbed energy corresponding to the joint angle within range of 0, 90°] is found to be quite similar with the shape of letter “U”, which further proves the anisotropic characteristics of the single jointed rock in the dynamic split tensile tests. The research results can provide references for the dynamic tensile mechanical properties of jointed rock.