Concurrent multi-scale domain decomposition simulation of discontinuous deformation of dam concrete
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摘要: 大坝混凝土的裂缝萌生和失稳扩展分析需要尽可能准确地模拟骨料和砂浆界面的弱不连续,而界面过渡区微米级的厚度模拟使得有限元网格存在网格剖分质量不佳和网格数量庞大的问题。通过在大坝混凝土细观结构的不同材料实体单元间预嵌零厚度界面单元,并进行宏细观子区域界面节点重新匹配,建立了骨料-砂浆-界面单元的宏细观区域分解有限元网格。同时结合隐式梯度损伤模型和内聚力模型,在同一模型中实现骨料、砂浆基质的损伤失效模拟及骨料-砂浆界面的弱连接到脱开模拟,构建了大坝混凝土非连续变形的宏细观并发多尺度区域分解模型。将模型用于某大坝混凝土的直接拉伸试验模拟,不同随机骨料模型均能捕捉骨料和砂浆界面的弱连接到脱开过程。重现的混凝土试件破坏形态与已有研究结果一致,证明了模型的合理性。本研究可为大坝混凝土损伤断裂力学性能的数值试验提供技术支持。Abstract: The analysis of crack initiation and instability propagation of dam concrete needs to simulate the weak discontinuity between aggregate and mortar as accurately as possible. The micron thickness of the interface transition zone makes the finite element mesh have the problems of poor mesh generation quality and large number of meshes. Zero-thickness cohesive interface elements were preset between the solid elements of different material interface. By reassembling subdomain interface configurations after presetting zero-thickness interface elements, the aggregate-mortar-interface multi-scale domain decomposition finite element mesh was established. Meanwhile, the gradient-enhanced continuum damage model and the cohesion model were combined to simulate the failure of aggregate and mortar matrix, and the weak link between the aggregate and cement matrix in one model. A macro-meso concurrent multi-scale domain decomposition model for discontinuous deformation of dam concrete was constructed. The model was applied to the direct tensile test simulation of a dam concrete. Both of the random aggregate models could capture the whole process from weak connection to disconnection of the interface between aggregate and mortar. The failure modes reproduced of concrete specimen were in agreement with the results of reference papers, proving that the model is reasonable, and can provide technical support for the numerical study of damage and fracture mechanical properties of dam concrete.
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表 1 混凝土细观结构各相与宏观均质结构力学性能参数[12,14,19]
Table 1. Mechanical property parameters of concrete meso-structure phases and macroscopic homogeneous structure [12,14,19]
材料 初始弹性模量/GPa 泊松比 拉伸强度/MPa 压缩强度/MPa 损伤门槛值 梯度参数/mm2 材料常数α 材料常数β 压缩-拉伸强度比 骨料 55.5 0.16 6.00 66.0 75.00 0.125 0.999 150 11 砂浆 26.0 0.22 2.50 27.5 9.62×10−5 0.125 0.999 150 11 ITZ 25.0 0.16 2.00 22.0 8.00×10−5 0.125 0.999 150 11 宏观 30.6 0.20 2.58 31.8 8.43×10−5 3.000 0.999 150 12 -
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