为掌握白垩系冻结砂岩动态压缩破坏机理,借助分离式霍普金森压杆对-30 ℃饱水砂岩开展不同应变率单轴冲击试验,结果表明:冻结砂岩动态损伤经历“线弹性变形、微裂纹演化、裂隙非稳定扩展、应变软化”4个阶段,损伤来源于初始宏细观缺陷与新生裂隙的交互演变,动态增长因子变化表明砂岩强度和变形的应变率强化效应显著;初始损伤由宏细观缺陷累加构成,不同尺度损伤缺陷耦合形成动态总损伤;单轴冲击压缩下岩石损伤演化呈正交异性,基于各向同性方程修正得到砂岩动态损伤本构关系,临界损伤是具备初始损伤、动弹性模量、动态抗压强度及峰值应变等指标特性的综合量;理论结果与试验曲线吻合良好,决定系数均＞0.910,能较好反映冻结砂岩峰前段强度特征。
Abstract
Uniaxial impact tests with different strain rates were carried out on -30 ℃ water-saturated sandstone with the help of split Hopkinson pressure bar to investigate the dynamic compression failure mechanism of Cretaceous frozen sandstone.Results reveal that the frozen sandstone experienced four stages of dynamic damage: linear elastic deformation,microcrack evolution,unstable crack propagation,and strain softening.The damage comes from the interactive evolution of initial macro- and micro-defects and new cracks.The change of dynamic growth factor demonstrates significant strain rate strengthening effect of sandstone’s strength and deformation.The initial damage is composed of the accumulation of macro- and micro-defects,and the dynamic total damage is formed by the coupling of damage and defects of different scales.The damage evolution of rock under uniaxial impact compression is orthotropic.The dynamic damage constitutive relationship of sandstone is modified based on the isotropic equation.Critical damage is a comprehensive quantity involving initial damage,dynamic elastic modulus,dynamic compressive strength and peak strain.The theoretical results are in good agreement with the experimental curves,with a decisive coefficients over 0.910.The present constitutive relation well reflects the strength characteristics of frozen sandstone before reaching peak.
关键词
白垩系冻结砂岩 /
霍普金森压杆 /
初始损伤 /
正交异性 /
本构模型
Key words
cretaceous frozen sandstone /
Hopkinson pressure bar /
initial damage /
orthotropic /
constitutive model
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基金
国家自然科学基金项目(41702339,51404193)
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