透水模板条件下新拌混凝土浇筑过程力学行为研究

Due to the complexity of process kinetics characteristics on casting compact concrete adopted controlled permeability formwork, it is difficult for fresh concrete to represent particle contact model in the meso level and deduce vibrating-seeping theory in the macro level. In view of the shortage in macro-mesoscopic theories and methods for seepage-solidification coupling when concrete is poured and bleeding is occurred, this study focuses on the casting process mechanical behavior of fresh concrete based on controlled permeability formwork, which contains: firstly, by means of model test and theoretical analysis, dynamic performance parameters system included medium damping, friction force, contact time and coordination number will be set up and, the virtual concrete particles unit contact model can be put forward; secondly, the permeability parameter characterization methods of controlled permeability formwork and fresh concrete mixture will be presented, thereby, the bleeding characteristic on mixture's interior and boundary can be described clearly; thirdly, combined with model dynamic test and numerical simulation, the interrelations between such as the vibrating technology and bulk damping or energy dissipation, formation mechanism for seepage and increasing-decreasing of pore pressure additionally, will be expounded; and finally, on account of developing the Particle Discrete Element Method theory, an Equivalent Discrete Particle-Homogeneous Liquid's Fluid-Solidification Coupling Model is expected to construct, further more, the improved numerical simulations on these positive results are programmed and verified..Integrated utilized the results above, a new theory to analyze bulk pore pressure dissipation and seepage-solidification of fresh concrete during cast with permeable boundary is attempted to found in this study to reveal mechanical behavior characteristics while the vibrating-seeping phenomenon occurred on fresh concrete's cast process. This study provides theoretical support for technical application on controlled permeability formwork; also, underlie the theory on construction process mechanics of fresh concrete.

采用透水模板浇筑密实混凝土的过程动力学特性复杂，新拌混凝土细观颗粒接触模型与宏观振捣排渗理论描述困难。课题针对浇筑过程排渗固结耦合缺少宏细观理论与方法研究缺失，拟开展透水模板条件下新拌混凝土浇筑过程力学行为研究:通过模型试验与理论分析,建立介质阻尼/摩擦力/接触时间/配位数等动力性能参数体系，提出虚拟混凝土颗粒单元接触模型；给出透水模板和混凝土渗透性参数表征方法，藉此描述新拌混凝土内部/边界泌水渗流特性；结合模型动力试验和数值仿真，阐述混凝土振捣工艺与阻尼/耗能相互关系及排渗/孔压长消形成机理；基于发展颗粒离散元理论思想，构建新拌混凝土等效离散颗粒-均质液相流固耦合理论模型，改进数值模拟计算程序，完成理论验证。综上研究，提出透水边界条件下混凝土孔压消散/排渗固结分析理论，揭示振捣排渗力学行为特征。课题研究可为透水模板技术应用提供理论支撑，也为混凝土浇筑过程力学提供理论基础。

项目背景：透水模板布内衬于模板排除新拌混凝土振捣产生的内部超孔隙压力，其振捣施工力学行为复杂，涉及学科知识交叉，宏细观过程高度非线性，物性参数描述困难；透水模板(布)的物理性能和作用机理研究亦刚起步，对上述浇筑过程行为研究缺少理论依据，对振捣排渗力学机制缺乏了解，未建立起有效分析与评价方法。鉴于此，开展透水模板条件下混凝土浇筑排渗过程力学行为研究。.项目主要研究了（1）混凝土细观虚拟颗粒单元接触力学模型和力学性能参数；（2）透水模板布排渗特性与测试方法；（3）混凝土振捣阻尼与孔隙压力长消试验与理论分析；（4）透水边界条件下混凝土离散-均质耦合排渗固结模型理论与数值方法。.项目研究重要成果：（1）建立了基于卡波姆浆液的颗粒动态可视化混凝土模拟新拌混凝土骨料颗粒接触试验模型与方法；给出了混凝土骨料等效规整离散颗粒的二维接触模型，定义了相应动力性能参数；（2）建立了基于宏观孔隙体积分数、细观孔结构构形及混凝土水化的分形渗透率和基于流变力学的等效两相颗粒体-液体大流变模型；（3）构建了透水模板布复层结构孔径测试分析理论和方法；研究提出了基于分形的透水模板布淤堵渗透时变系数计算方法；（4）建立了新拌混凝土渗透性与模板布几何参数及新拌混凝土工艺参数关系模型；解释了振动条件下透水模板布边界残余孔压分布机制（5）获得了新拌混凝土振捣孔压长消分布、内部排渗速率、累计排渗量与模板布边界、振动能量、混凝土配比之间相互规律；给出了振捣耗能与孔压变化的参数化表征关系与混凝土振捣孔压消散与拌合物固结的解析方程；（6）建立了透水边界条件下混凝土离散-均质耦合排渗固结模型，给出了其数值计算实现方法。.项目研究意义：以上研究，为常态混凝土浇筑成型质量控制与宏细观评价、水工碾压变态混凝土加浆振捣技术控制与分析提供了理论支撑和技术开发应用基础，并取得了多项专利成果。