摘要
了解岩石动态抗拉特性对于研究岩体工程在爆破和地震荷载作用下的动态响应具有重要意义。结合超高速相机和数字图形相关技术(digital image correlation,DIC)对花岗岩开展冲击劈裂试验。通过电测应变法和超高速相机判断了巴西圆盘试样的应力平衡和中心起裂条件。采用超高速DIC方法分析了微秒时间尺度上岩石变形场演化,并结合偏光镜试验讨论了晶体尺度上的材料率效应机制。结果表明:花岗岩的抗拉强度随应变速率的关系存在3个分区,II区满足统一动态强度模型,其特征应变率和动增长系数分别为48.3 s^(−1)和0.97,且平均破碎尺寸并不随应变率的增加而显著变化;残余动能占耗散能比值为23%~47%。在晶体尺度上,细观破裂主要以穿晶裂纹、弯折裂纹、裂纹簇聚成带和晶体粉碎化等形式出现。随着应变率增加,岩石的破坏过程发生从中心起裂到边界失效转变,当应变率超过一定值,应力平衡和中心起裂条件失效,动态抗拉强度随应变速率增加反而降低,导致试验条件的有效性存在偏差,试验结果需审慎评估。
Understanding the dynamic tensile behavior of rock is essential for studying the response of rock masses under blasting and seismic loading.Granite specimens were subjected to dynamic Brazilian splitting tests using a combination of ultra-high-speed camera and digital image correlation(DIC)techniques.Stress equilibrium and central crack initiation were assessed through strain gauge measurements and high-speed photography.The evolution of the deformation field on the microsecond timescale was analyzed using high-speed DIC,and the rate-dependent mechanisms at the crystal scale were investigated through polarizing microscopy.The results show that the tensile strength–strain rate relationship of granite can be divided into three regimes.In Regime II,the behavior conforms to the unified dynamic strength model,with a characteristic strain rate of 48.3 s-1 and a dynamic increase factor of 0.97.Notably,the average fragment size remains nearly constant with increasing strain rate.The ratio of residual kinetic energy to total dissipated energy ranges from approximately 23%to 47%.At the crystal scale,meso-scale failure modes include transgranular cracking,crack deflection,crack clustering into bands,and grain pulverization.With increasing strain rate,the failure process transitions from central crack initiation to boundary-dominated failure.When the strain rate exceeds a critical threshold,stress equilibrium and central initiation conditions are no longer met,resulting in an apparent decrease in dynamic tensile strength.This indicates that test validity may be compromised under such conditions,and results must be interpreted with caution.
作者
李晓锋
李海波
刘黎旺
傅帅旸
LI Xiao-feng;LI Hai-bo;LIU Li-wang;FU Shuai-yang(State Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China;University of Chinese Academy of Sciences,Beijing 100049,China;School of Safety Science and Engineering,Nanjing University of Science and Technology,Nanjing,Jiangsu 210094,China)
出处
《岩土力学》
北大核心
2025年第8期2387-2398,共12页
Rock and Soil Mechanics
基金
国家自然科学基金(No.U22A20239)
岩土力学与工程安全全国重点实验室“揭榜挂帅”项目(No.SKLGMEJBGS2402)。
关键词
岩石力学
冲击荷载
率效应机制
统一强度模型
破碎演化
rock mechanics
impact load
strain rate mechanism
unified dynamic strength model
dynamic fragmentation
