Coral reef limestone at different depositional depths and facies differ remarkably on the textural and mineralogical characteristics, owing to the complex sedimentary diagenesis. To explore the effects of pore structure and mineral composition associated with diagenetic variation on the mechanical behavior of reef limestone, a series of quasi-static and dynamic compression tests along with microscopic examinations were performed on the reef limestone at shallow and deep burial depths. It is revealed that the shallow reef limestone (SRL) is classified as a porous aragonite-type carbonate rock with high porosity (55.3±3.2)% and pore connectivity. In comparison, the deep reef limestone (DRL) is mainly composed of dense calcite-type calcium carbonate with low porosity (4.9±1.6)% and pore connectivity. The DRL strengthened and stiffened by the tight grain framework consistently displays much higher values of the dynamic compressive strength, elastic modulus, brittleness index, and specific energy absorption than those of the SRL. The gap between two types of limestone further increases with an increase in strain rate. It appears that the failure pattern of SRL is dominated by the inherent defects like weak bonding interfaces and growth lines, revealed by the intricate fracturing network and mixed failure. Likewise, although the preexisting megapores in DRL may affect the crack propagation on pore tips to a certain distance, it hardly alters the axial splitting failure of DRL under impacts. The stress wave propagation and attenuation in SRL is primarily controlled by the reflection and diffusion caused by plenty mesopores, as well as an energy dissipation in layer-wise pore collapse and adjacent grain crushing, while the stress wave in DRL is highly hinged on the insulation and diffraction induced by the isolated megapores. This process is accompanied by the energy dissipation behavior of inelastic deformation resulted from the pore-emanated microcracking.

中文翻译：

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成岩作用变化对珊瑚礁灰岩静态和动态力学行为的影响


由于复杂的沉积成岩作用，不同沉积深度和相的珊瑚礁灰岩的结构和矿物学特征存在显着差异。为了探讨与成岩变化相关的孔隙结构和矿物成分对礁灰岩力学行为的影响，对浅埋深和深埋藏深度的礁灰岩进行了一系列准静态和动态压缩试验以及显微镜检查。结果表明，浅礁灰岩（SRL）属于多孔文石型碳酸盐岩，孔隙率较高（55.3±3.2）%，孔隙连通。相比之下，深礁灰岩（DRL）主要由致密方解石型碳酸钙组成，孔隙度较低（4.9±1.6）%，孔隙连通性低。通过紧密的晶粒框架强化和硬化的 DRL 始终表现出比 SRL 高得多的动态压缩强度、弹性模量、脆性指数和比能量吸收值。随着应变率的增加，两种石灰石之间的差距进一步增大。看来，SRL 的失效模式主要是由复杂的断裂网络和混合失效揭示的弱结合界面和生长线等固有缺陷决定的。同样，虽然DRL中预先存在的大孔可能会在一定距离内影响孔尖端的裂纹扩展，但它几乎不会改变DRL在冲击下的轴向劈裂破坏。 SRL中的应力波传播和衰减主要受大量介孔引起的反射和扩散以及层状孔隙塌陷和相邻颗粒破碎的能量耗散控制，而DRL中的应力波高度取决于绝缘层和由孤立的大孔引起的衍射。这一过程伴随着孔隙产生的微裂纹导致的非弹性变形的能量耗散行为。