摘要
强冲击荷载作用下岩石应力状态复杂多变,为了研究花岗岩在高应变率加载下岩石的应力状态变化及破裂特征,利用霍普金森试验系统对0.6,1.0,1.4长径比花岗岩试样进行动态冲击试验,结合LS-DYNA模拟岩石冲击试验,分析研究了花岗岩试样的应力平衡过程、破裂特征及应力应变演化规律。结果表明:在10 m/s冲击速度下,0.6,1.0,1.4长径比花岗岩应力平衡持续时间分别为60,60,13μs。当ε低于84.6 s^(-1)时,1.4长径比花岗岩无法达到应力平衡,岩石破坏后多呈现断裂或长条状碎块,当提升冲击速度至14 m/s时,应变率提升至102.6 s^(-1),岩石块度逐渐均匀。3种长径比花岗岩试样在80~120 s^(-1)加载应变率下破碎块度均匀。与数值模拟试验结果对比可知,岩石在弹性变形阶段满足应力应变均匀性假定,在塑性变形直至峰后阶段应力分布开始紊乱,诱使应变均匀度下降,这是导致岩石破裂块度分布不均的直接因素。通过降低岩石长径比的方式来消除惯性效应可以使岩石长期处于应力平衡,使岩石破碎块度均匀。
The stress state of the rock is complex and changeable under the action of a strong impact load.To study the change of the stress state and fracture characteristics under high strain rate loading of granite,the Hopkinson test system was used to do the dynamic impact test with length-diameter ratios of0.6,1.0,and 1.4.Combined with LS-DYNA simulated rock impact test,the stress balance process,fracture characteristics,and stress-strain evolution law of granite samples were analyzed.The test results show that under the impact velocity of 10 m/s,the stress equilibrium time of granite stress loading pulse with 0.6,1.0 and 1.4 three length-diameter ratios are 60,60 and 13μs respectively.Whenεis lower than 84.6 s^(-1),the stress equilibrium of granite with length-diameter ratio of 1.4 cannot be achieved,and most of the rocks show fracture or long strip fragments after failure.When the impact velocity is increased to 14 m/s,the strain rate is increased to 102.6 s^(-1),and the rock fragmentation is be coming gradually uniform.When the granite samples with three length-diameter ratios are damaged at the loading strain rate of 80~120 s^(-1),sufficient stress equilibrium time and uniform fragmentation can be guaranteed.Comparing the test and numerical simulation results of the granite sample,it can be seen that the rock could meet the stress and strain uniformity assumption in the elastic deformation stage.In the plastic deformation stage until the post-peak stage,the stress distribution begins to be disordered,thus reducing the decrease of strain uniformity,which is the direct factor leading to the uneven distribution of rock fracture fragmentation.Eliminating the inertial effect by reducing the length-diameter ratio of rock could keep the rock in stress equilibrium for a long time.The longer the duration of stress equilibrium is,the more uniform the rock fragmentation is.
作者
胡智航
董汉宁
刘鑫
徐振洋
HU Zhihang;DONG Hanning;LIU Xin;XU Zhenyang(School of Mining Engineering,University of Science and Technology Liaoning,An'shan 114051,China;The Sencond Construction Co.,Ltd.,China Construction First Group,Beijing 102627,China)
出处
《西安科技大学学报》
CAS
北大核心
2023年第2期352-361,共10页
Journal of Xi’an University of Science and Technology
基金
辽宁省教育厅项目(LJKZ0282,LJKZ0313)。
关键词
SHPB
高应变率
应力平衡
破坏特征
Split Hopkinson Pressure Bar
high strain rate
stress equilibrium
deformation characteristics
