Coral reef limestone (CRL) commonly undergoes dynamic tension when underground structures of island reefs encounter impacts, explosions, or seismic activities. Given the complexity of biological pores, the dynamic tensile fracture characteristics of CRL are poorly understood. Therefore, the dynamic tensile fracture behaviors of deep CRL were systematically observed by Split Hopkinson Pressure Bar tests and digital image techniques. Comparing to traditional rocks, the macro-pores near failure band would significantly change cracking path. The failure patterns are dominated by loading rate. The strongly dependence of dynamic tensile strength and dynamic crack initiation toughness on loading rate suggests the two indices overcome the effect of CRL macro-pores under dynamic impacts. At low loading rates, tensile fractures predominantly follow intergranular cracks, whereas transgranular cracks dominate at higher rates. The fractal dimension of fracture surface decreases with increasing crack propagation velocity, loading rate, and dynamic crack initiation toughness. Due to the unique marine sedimentary environment, the mechanical heterogeneity in multiple scales distinguishes CRL from terrestrial rock materials. The insights into underlying mechanisms of dynamic tension provide support to optimization of blasting scheme and stability assessments for island underground engineering.

中文翻译：

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动态载荷作用下深部珊瑚礁石灰岩的拉伸断裂性能和全场应变演化


当岛礁的地下结构遇到撞击、爆炸或地震活动时，珊瑚礁石灰岩 （CRL） 通常会经历动态张力。鉴于生物孔的复杂性，人们对 CRL 的动态拉伸断裂特性知之甚少。因此，通过 Split Hopkinson Pressure Bar 测试和数字成像技术系统观察深 CRL 的动态拉伸断裂行为。与传统岩石相比，破坏带附近的大孔隙会显著改变裂缝路径。故障模式由加载速率主导。动态抗拉强度和动态裂纹萌生韧性对加载速率的强烈依赖性表明，这两个指标在动态冲击下克服了 CRL 大孔的影响。在低载荷速率下，拉伸裂缝主要跟随晶间裂纹，而跨晶裂纹以较高的速率为主。裂缝表面的分形维数随着裂纹扩展速度、加载速率和动态裂纹起裂韧性的增加而减小。由于独特的海洋沉积环境，多个尺度的力学非均质性将 CRL 与陆地岩石材料区分开来。对动态拉力潜在机制的洞察为岛屿地下工程爆破方案的优化和稳定性评估提供了支持。