骨料不规则程度对混凝土单轴受压性能影响的数值研究

Mesoscale study on the influence of aggregate irregularity on uniaxial compressive properties of concrete

摘要

为了在细观层面上研究骨料不规则程度对混凝土力学性能及破坏形态的影响，采用Python程序二次开发了ABAQUS生成尖锐程度不同的随机分布骨料模型，分别建立零厚度cohesive单元与可变厚度的实体界面过渡区（interface transition zone，ITZ）。首先通过改变网格尺寸和加载垫块与混凝土间的摩擦系数确定合适的参数，并与实验对比验证模型的可靠性，随后分析2种ITZ建模方式的优劣，最后对三维细观混凝土模型进行单轴受压模拟，从应力-应变曲线、破坏形态、能量耗散方面进行分析。结果表明：零厚度cohesive ITZ与实体厚度ITZ模型都可预测混凝土抗压强度，具有实体厚度的ITZ模型的应力-应变曲线及破坏形态与实验更加贴合；混凝土破坏形态受骨料形状参数影响明显，球形骨料模型内部与表面均为贯穿式裂缝，多面体骨料模型应变能较大，混凝土内部微裂缝较多，容易受压破坏成更多的碎块；随着骨料不规则程度的增加，混凝土抗压强度略有提高但峰值应变不受影响。

Abstract

In order to determine the influence of aggregate irregularity on the mechanical properties and failure morphology of concrete，Python programs were developed to generate randomly distributed aggregate models with different sharpness in ABAQUS，and the 0-thickness cohesive element and variable-thickness solid interface transition zone（ITZ）were established respectively.First，the reliability of model was determined by changing mesh size and friction coefficient between the loading pad and concrete compared with the experiment.Then，the quality of two ITZ modeling methods was analyzed.Finally，the uniaxial compression mechanical behavior of the three-dimensional meso-concrete model was analyzed from the aspects of stress-strain curve，fracture propagation，and energy dissipation.The simulation results show that the 0-thickness cohesive ITZ and the solid thickness ITZ model can predict the compressive strength of concrete，and the stress-strain curve and failure morphology of the ITZ model with solid thickness are more consistent with the experiment.The fracture propagation of concrete is obviously affected by the shape parameters of aggregate.The interior and surface of the spherical aggregate model are penetrating cracks.The strain energy of polyhedral aggregate model is larger，and there are many micro-cracks in the concrete，the possibility being compressed and destroyed into more fragments is higher.With the increase of aggregate irregularity，the compressive strength of concrete increases slightly，but the peak strain is not affected.

关键词

三维细观混凝土 / 骨料 / 黏聚力单元 / 数值模拟 / 裂纹扩展

Key words

3D mesoscale concrete / aggregate / cohesive element / numerical simulation / crack propagation

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基金资助

国家自然科学基金资助项目(11802132)