堆石混凝土材料细观力学过程及宏观综合性能研究

Rock-Filled Concrete (RFC), with a full intelligence property by inventors, is a new technique in massive concrete dam construction. RFC has many advantages, such as simple and shortcut construction process, cost-effective, good reliability and environmental friendly etc., so it has already been applied successfully in more than 30 projects. RFC is produced by pouring specialized self-compacted concrete (SCC) into forms containing rocks; the space between rocks can easily be filled with good fluidity SCC. For this reason, the formed RFC, which is dense and low hydration heat, can satisfy strength and durability requirement. The nonlinear macroscopic properties of RFC are determined by the meso-mechanical process, for instance the mechanical response of the rocks skeleton, the flowing and blocking processes of SCC, and the concrete cracking at early age. Using meso-macro dual scale mechanical methods, following problems are researched: firstly, the flowing and blocking processes of SCC between rocks are studied to formulate measures to ensure RFC dense; secondly, the effects of the rock blocks skeleton on the concrete cracking at early age are studied to analyze the mechanism of crack resistance; finally, effects of large scale rocks on the macroscopic comprehensive properties of hardened RFC are studied to improve measurement techniques. All these studies can provide the scientific basis and theoretical foundation for optimizing construction technique and improving comprehensive properties of RFC in order that RFC can be used in some higher dams with the height of more than 100m in the future.

堆石混凝土是以大粒径块石组成堆石骨架，由专用自密实混凝土在重力作用下流动充填堆石体空隙而形成的完整、密实、低水化热的大体积混凝土。堆石混凝土技术由申请人团队发明，具有自主知识产权，已应用于30多个水利水电工程。近期，将逐步推广应用于百米级大坝，对堆石混凝土的综合性能和施工工艺等提出了更高要求。本项目拟采用细观力学方法，1）研究新拌自密实混凝土在堆石体空隙中的流动过程及填充机理，建立最佳施工层厚与块石粒径的对应关系以优化施工工艺；2）研究温度及多种荷载作用下，堆石体骨架与早龄期自密实混凝土的耦合作用与协调发展机制，深入认识堆石混凝土早龄期抗裂机理，以优化温控；3）分析堆石骨架与块石粒径对堆石混凝土综合性能的影响，发展检测堆石混凝土性能的高效实验手段，建立模拟堆石混凝土结构全生命期性能的数值分析模型。该项目的研究为百米级堆石混凝土大坝建设奠定理论基础。

本项目根据堆石混凝土工程的密实性与超大骨料等工程问题提炼出的科学问题开展研究，在Bingham两相流体在复杂空隙中流动、堆石体与自密实混凝土相互耦合作用、超大粒径混凝土细观力学模拟与综合性能等领域开展了深入研究，发展了二维、三维LBM-DEM耦合模拟模拟堆石混凝土浇筑过程，揭示了浇筑过程的流动规律和堵塞机理，提出了临界阻塞条件主要依赖于自密实混凝土最大骨料粒径与堆石孔隙尺寸之比以及自密实的流动性能，从科学角度解释了堆石混凝土实际工艺参数中：1）自密实混凝土最大粒径小于20mm、堆石粒径必须大于300mm的规定有一定富裕度，可以优化以进一步降低造价；2）自密实混凝土流动性能是保障堆石混凝土密实度的关键因素，除传统的V漏斗与塌落扩展度以外，还必须加入稳定性指标。本研究发展的稳定性试验方法和指标已经进入最新编制的行业标准，本项目的研究直接促进了技术进步。本项目还采用物理试验、细观力学模拟和有限元仿真分析等综合手段研究了堆石混凝土热物理及强度等力学性能与自密实混凝土性能的关系，建立了相关公式，进入了堆石混凝土技术标准体系，为堆石混凝土高重力坝和堆石混凝土拱坝建设提供了强有力的技术与理论支撑。本项目研究成果共发表SCI论文44篇，出版1部学术专著，参与主编了3个堆石混凝土相关技术标准，主持编写了2本国际技术文件，获得8项国家发明专利授权，另有8项发明专利正在实质审查，培养了10余名博士及一批硕士，项目组成员王进廷教授获得国家自然科学基金杰出青年基金资助。本研究成果获得了教育部技术发明一等奖和国家技术发明二等奖。