自密实混凝土拌合物表面能时变函数的构建与应用

Construction and application of a time-dependent surface energy function for self-compacting concrete mixtures

摘要

【目的】针对混凝土拌合物在防渗墙等水工结构施工中流动性衰减与界面黏结演化难以定量表征的问题，提出基于坍落度演化的混凝土界面表面能时变建模方法。【方法】通过多龄期坍落度与扩展度试验获取混凝土拌合物的流动性衰减序列，构建与实体试验尺寸一致的三维颗粒流模型，在PFC中采用Johnson-Kendall-Roberts(JKR)接触模型刻画颗粒间黏附行为，并针对砂浆-砂浆、砂浆-骨料、骨料-骨料等不同接触界面设定分级表面能参数以体现黏结力差异。在宏观坍落度结果约束下，以三参数Logistic函数描述砂浆-砂浆界面表面能随龄期的时变规律，通过Sliced/Nested Orthogonal Array(SOA-AR)嵌套正交设计反演函数参数，并将所得γ_mm(t)函数嵌入PFC模型实现界面黏结参数的时变表达。【结果】数值模拟结果表明，引入时变表面能函数能够再现试验中坍落度随龄期下降的规律，拟合曲线拐点与混凝土初凝时间一致。在浇筑模拟中应用γ_mm(t)函数后，混凝土堆积顶面高度差约0.26 m,低于规范限值0.30 m;砂浆-槽壁界面法向反压力约0.02~0.05 kPa,与规范中泥浆静压力量级一致，表明模型能够较真实地反映拌合物的流动与堆积过程及界面受力特征。【结论】所提出的界面表面能时变函数有效刻画了混凝土由流态向凝结态的演化过程，建立了宏观流动性与细观黏结性能的映射关系。研究成果为包含复杂界面行为的水下浇筑与防渗墙施工过程的数值模拟提供了可行思路，为相关工程实践与后续数值分析提供了参考依据。

Abstract

[Objective] To address the difficulty in quantitatively characterizing the flowability degradation and interface bonding evolution of concrete during the construction of hydraulic structures such as cutoff walls, a time-dependent modeling method for concrete interface surface energy based on slump evolution is proposed. [Methods] Multi-age slump and spread tests were conducted to obtain the flowability degradation sequence of the concrete mixture. A three-dimensional particle flow model(PFC), consistent with the dimensions of the physical tests, was constructed. The Johnson-Kendall-Roberts(JKR) contact model was used in PFC to characterize the adhesive behavior between particles. Graded surface energy parameters were assigned to different contact interfaces—mortar-mortar, mortar-aggregate, and aggregate-aggregate—to reflect differences in bonding strength. Under the constraint of macroscopic slump result, a three-parameter Logistic function was employed to describe the time-dependent variation of the mortar-mortar interface surface energy with age. The function parameters were inversely calibrated using a sliced/nested orthogonal array(SOA-AR) design. The obtained γ_mm(t) function was then embedded into the PFC model to realize the time-dependent representation of interface bonding parameters. [Results] Numerical simulation result showed that introducing the time-dependent surface energy function could reproduce the observed age-related slump decline. The inflection point of the fitted curve was consistent with the concrete's initial setting time. After applying the γ_mm(t) function in the casting simulation, the height difference of the concrete top surface was approximately 0.26 m, which was below the 0.30 m limit specified in the code. The predicted normal reaction force at the mortar-trench wall interface ranged from approximately 0.02 kPa to 0.05 kPa, consistent with the order of magnitude of the slurry hydrostatic pressure specified in the code. The result indicated that the model could realistically reflect the flow and deposition process of the mixture and the mechanical characteristics of the interfaces. [Conclusion] The proposed time-dependent interface surface energy function effectively captures the evolution of concrete from a fluid to a setting state and establishes a mapping relationship between macroscopic flowability and mesoscopic bonding properties. The findings provide a feasible approach for the numerical simulation of underwater casting and cutoff wall construction processes involving complex interface behavior, offering a reference for related engineering practice and subsequent numerical analysis.

关键词

界面表面能 / 坍落度 / JKR接触模型 / 颗粒流模拟 / SOA-AR反演 / 混凝土拌合物 / 影响因素 / 水下浇筑

Key words

interfacial surface energy / slump / JKR contact model / particle flow simulation / SOA-AR inversion / concrete mixture / influencing factors / underwater pouring

基金资助

国家重点研发计划项目(2024YFF1700700)