2D/3D modeling of concrete weight coating to understand its performance including crack development

这项工作的目的是产生一个模型，预测海底管道上的混凝土配重涂层（CWC）的性能。模拟现场条件的全尺寸弯曲、剪切或冲击试验成本高且耗时。在评估管道制造过程的潜在变化时，需要一个模型来可靠地预测变化的影响。这种模式将有助于通过确定和预先选择最有希望的制造方法和组合来减少全面测试的负担。必须考虑几个变量，包括：使用的骨料和水泥、钢管防腐涂层的类型、嵌入钢筋的类型和布置以及混凝土配重涂层的应用方法（冲击或压缩）。所有这些变量都在不断变化，这取决于安装的地理位置和可用的材料/方法。提出了一种基于有限元离散元模型（FDEM）技术的微（μ）力学建模方法。FDEM结合了大应变有限元与离散单元的优点，允许明确建模裂纹扩展到原始完整的材料，以及不同相和材料之间的相互作用。通过在μ尺度上对物理相互作用进行建模，FDEM能够再现测试材料的响应，作为模型的一种新兴特性。化学武器公约的µ-表征以及在µ x射线计算机断层扫描机（µCT）内进行的标准机械测试将为FDEM模型的开发提供信息和约束。

The objective of this work is to produce a model that predicts the performance of concrete weight coating (CWC) on submarine pipelines. Full-scale bending, shear, or impact tests to simulate the field conditions are costly and time consuming. When evaluating potential changes to the pipe manufacturing process, a model to reliably predict the impact of the changes is desired. Such a model would help to reduce the burden of full-scale testing by identifying and pre-selecting the most promising manufacturing approaches and combinations to put forward. Several variables must be accounted for, including: the aggregate and cement used, the type of anti-corrosion coating applied to the steel pipe, the type and arrangement of embedded reinforcement, and the method of concrete weight coating application (impingement or compression). All of these variables are in constant flux depending on the geographical location of the installation and the available materials/methods. A micro (µ) mechanical modeling approach is suggested based on the finite discrete element model (FDEM) technology. FDEM combines the advantages of large strain finite elements with those of the discrete elements, allowing for explicitly modelling the propagation of cracks into an originally intact material, as well as the interaction between the different phases and materials. By modelling the physical interactions at the µ-scale, FDEM is able to reproduce the response of the tested material as an emergent property of the model. A µ-characterization of CWC together with standard mechanical tests performed inside a µ x-ray computed tomography machine (µCT) will inform and constrain the development of a FDEM model.