The coral reef rock has a rich porous structure, and establishing an entity model with a realistic porous structure will do great good to study the mechanical behavior and its mechanisms. However, the pore's characterized size of coral rocks spans four orders of magnitude from micro to scales (1 μm to 10 mm). This requires a large specimen size and a very small element size in the model, which leads to extremely high computational costs. To overcome this fundamental challenge, this paper uses CT to scan a macro coral specimen to obtain an entity model and establishes a micro- scale coupled model: (1) retaining pore’s equivalent diameter larger than 1mm in the overall CT entity, and regarding the rest part as a uniformly dense matrix material with unknown material’s properties, which is called the model; (2) extracting a small entity containing pore’s equivalent diameter less than 1mm from the CT entity, which is called the micro model also with unknown matrix material properties; (3) the unknown matrix material parameters in model are derived from mechanical response of the micro model, and the unknown matrix material parameters in micro model are confined by that model's mechanical responses should be coincident with that of a real coral specimen. Comparing with the uniaxial compression test result, this micro- coupled model has high precision and retains the influence of pores at various scales. The computational result shows that it can reduce the computational complexity of a single CT entity model by four orders of magnitude. It provides a new approach for studying similar materials' mechanical behavior and mechanisms under complex loading conditions.

中文翻译：

---

基于CT扫描的珊瑚礁岩石微细观耦合模型


珊瑚礁岩石具有丰富的多孔结构，建立具有真实多孔结构的实体模型将有助于研究其力学行为及其机制。然而，珊瑚岩孔隙的特征尺寸跨越了从微米到尺度（1 微米到 10 毫米）的四个数量级。这需要模型中具有较大的样本尺寸和非常小的单元尺寸，从而导致极高的计算成本。为了克服这一根本性挑战，本文利用CT对宏观珊瑚标本进行扫描，获得实体模型，并建立微尺度耦合模型：（1）在整体CT实体中保留大于1mm的孔隙当量直径，其余部分考虑部分为均匀致密的基体材料，材料特性未知，称为模型； (2)从CT实体中提取出孔隙当量直径小于1mm的小实体，称为微观模型，且基体材料特性未知； (3)模型中的未知基质材料参数是由微模型的力学响应推导出来的，并且微模型中的未知基质材料参数受模型的力学响应应与真实珊瑚标本的力学响应一致的限制。与单轴压缩试验结果相比，该微耦合模型精度较高，保留了不同尺度孔隙的影响。计算结果表明，它可以将单个CT实体模型的计算复杂度降低四个数量级。它为研究复杂载荷条件下类似材料的力学行为和机制提供了一种新方法。