为研究2种珊瑚礁灰岩在冲击荷载下的动态力学特性和损伤特征,利用分离式霍普金森压杆(SHPB)试验系统,对珊瑚格架灰岩和珊瑚砂屑灰岩进行10~190 s-1应变率范围内的冲击压缩试验,得到不同应变率下珊瑚礁灰岩的应力-应变曲线,分析试验中试样的动态峰值应力和弹性模量的应变率效应及能量耗散规律,并结合高分辨率CT扫描和图像处理技术,揭示试样的损伤破坏特征。结果表明:格架灰岩的动态应力-应变曲线具有明显的弹性变形阶段,而砂屑灰岩的压密阶段较为明显;动态峰值应力随应变率的增大呈幂函数增长,格架灰岩的应变率效应较明显,动态弹性模量与应变率满足负指数关系;格架灰岩对能量的吸收能力整体强于砂屑灰岩;珊瑚礁灰岩损伤裂纹多沿生物组分胶结差、贯通孔隙多的部位发生,中高应变率下格架灰岩的损伤裂纹以骨架扩展贯通为主,呈脆性劈裂破坏,而砂屑灰岩主要发生穿孔传播,呈压碎破坏模式,研究成果对岛礁工程建设中动力灾害的预防具有一定的指导意义。
Abstract
To investigate the dynamic mechanical properties and damage characteristics of two types of coral reef limestones under impact loading, split Hopkinson pressure bar (SHPB) test apparatus was used to conduct impact compression tests on coral lattice limestone and coral clastic limestone in the strain rate range of 10~190 s-1. The stress-strain curves of reef limestone under different strain rates were analyzed to obtain the strain rate effect and energy dissipation of dynamic peak stress and elastic modulus. In addition, the damage and failure characteristics of samples were revealed using high-resolution CT scanning and image processing technology. Results show that the dynamic stress-strain curves of lattice limestone exhibit an obvious elastic deformation stage, while the compaction stage of clastic limestone is more apparent. Furthermore, the dynamic peak stress increases as a power function with the increase of strain rate, and the strain rate effect of lattice limestone is stronger. The relationship between dynamic elastic modulus and strain rate is negatively exponential. Moreover, the energy absorption capacity of lattice limestone is stronger than that of clastic limestone. The damage cracks of reef limestone are mostly found along sites with poor cementation of biological components or many penetrative pores. Under medium and high strain rates, the damage cracks of lattice limestone mainly undergo matrix propagation and transfixion, presenting brittle fracture failure, and clastic limestone perforation propagation, presenting crushing failure mode. The research findings are of guiding significance for preventing dynamic disasters in island and reef engineering construction.
关键词
动态峰值应力 /
损伤特征 /
珊瑚礁灰岩 /
应变率效应 /
能量耗散 /
动力灾害预防
Key words
dynamic peak stress /
damage characteristics /
coral reef limestone /
strain rate effect /
energy dissipation /
dynamic disaster prevention
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基金
国家自然科学基金面上项目(41877260,41877267);中国科学院战略性先导科技专项(A 类) (XDA13010201)
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