长期荷载作用下混凝土面板细观损伤与宏观开裂机理研究

With the rapid development of hydropower exploitation in our country, many 300m level’s ultra-high concrete faced rock-fill dams are planning to be constructed in the western alpine and gorge region, the crack prevention of concrete panel is the key challenge. The project intends to field investigate many constructed and under-construction concrete faced rock-fill dam, on the basis of mastering the characteristics of cracking of concrete panels, further study by mastering the characteristics of concrete panel damage and cracking; Through the concrete panel creep deformation and microscopic damage CT laboratory tests, grasp the evolution of meso-damage of concrete panel under long-term loads; Based on extended finite element method, establishing a numerical calculation model of continuous-discontinuous which considering the panel cracking, conducting the numerical simulation of concrete faced rock-fill dam under long-term load with this model, analysis cracking process of concrete panel; on the foundation of the principle of energy transferring dissipation, exploring the inherent relationship between meso-damage and macro-cracking, and revealing the mechanism of meso-damage and macro-cracking for concrete panel under long-term load. The research of this project is meaningful to grasp the initiation and propagation process until cracking damage of the crack, and it’s significant to reveal the cracking mechanism of the panel, it can provide a theoretical foundation and technical support for the construction of ultra-high concrete faced rock-fill dam.

我国水电开发正进入一个快速发展期，西部高山峡谷地区正在规划建设多个300m 级超高面板堆石坝，其中的关键难题就是混凝土面板的防裂。本项目拟通过对在建和完建工程的实地调研，掌握混凝土面板损伤开裂特征，为进一步研究混凝土面板的开裂机理奠定实践基础；采用混凝土面板徐变损伤及混凝土面板细观损伤CT 室内试验，揭示长期荷载作用下混凝土面板细观损伤演化规律；基于扩展有限元法，研究建立考虑混凝土面板连续-非连续开裂的数值计算模型，并应用于长期荷载作用下混凝土面板堆石坝面板开裂的数值仿真计算，揭示混凝土面板的开裂过程；基于能量传递耗散原理，探讨细观损伤与宏观开裂的内在关系，进而揭示长期荷载作用下混凝土面板细观损伤与宏观开裂机理。本项目的研究对于系统分析面板裂缝萌生、扩展直至发生开裂破坏过程，揭示面板的开裂机理有重要意义，可以为超高混凝土面板堆石坝的建设提供理论基础与技术支撑。

混凝土面板是堆石坝的主要防渗体，研究多种荷载长期作用下混凝土面板细观损伤与宏观开裂机理有重要的科学意义和工程应用价值。本项目使用工业CT获取了混凝土试件在施加持续荷载前后的CT图像，通过对断层CT图像进行三维重构得到混凝土内部骨料和孔隙的三维分布，并分析了CT尺度下不同持荷水平混凝土内的损伤特征。基于混凝土面板堆石坝的应力变形数值仿真计算结果，以等效位移荷载的方式模拟面板受力，采用扩展有限元方法模拟了二维面板水力压裂、多条裂缝相交和相互干扰过程。构建了混凝土徐变损伤耦合模型，开展了不同持续荷载水平下的混凝土徐变损伤研究，并针对某面板堆石坝研究了面板在长期蓄水作用下的应力变形特性。考虑静水压力和裂缝倾角的共同影响，对含初始裂缝混凝土试件进行室内轴压试验，得出了含初始裂缝混凝土在不同静水压力环境中的力学性能和破坏形态规律。通过掺入引气剂对混凝土内部造成一定的初始损伤，研究了在单轴受压作用下混凝土内部损伤的演化规律，并获得了在持续荷载作用下初始损伤对非线性徐变的影响以及演化规律。