服役环境下混凝土防渗墙性能演化研究

The concrete cutoff wall is the lifeline engineering for seepage prevention system of dam built on overburden. During its service process, there exists physical effects, including high confining pressure, high osmotic gradient and reservoir water level periodical fluctuation, and chemical action of surrounding water erosion, which leads to the deterioration of concrete cutoff wall in long-term service performance..In this research, the plain concrete cutoff wall with two ends repressed is selected as study object. Based on the holistic idea of “laboratory experiment–mechanism analysis–evolution law”, the durability of cutoff wall under coupled stress and chemistry is carried out by combining numerical modeling, macro-microscopic experiment and theoretical analysis method. Firstly, according to the true operating performance of cutoff wall reproduced by numerical simulation, the stress state and stress path of cutoff wall during service process are studied. Next, a series of laboratory experiments under coupled stress and chemistry will be carried out, the macroscopic properties deterioration law of cutoff wall during the evolution process is disclosed. Then, the microcosmic method, such as scanning electron microscope, is carried out to research the evolution of microscopic variables of concrete damage and reveal the mechanism of concrete performance evolution under the effect of water chemistry coupled with stresses. Finally, the relationship and regulation mechanisms of the evolution of concrete damage microscopic variables and its macroscopic performance are explored, as well as the cutoff wall performance damage evolution model is established, which provides a scientific basis for improving concrete durability and long-term safe evaluation of the cutoff wall project.

混凝土防渗墙是覆盖层上大坝防渗体系的生命线工程，它在服役过程中存在高围压、高渗透梯度以及库水位周期性升降的物理作用和环境水侵蚀的化学作用，导致防渗墙长期服役性能发生劣化。.本项目以两端固嵌式的素混凝土防渗墙为研究对象，遵循“室内试验—机理分析—演化规律”的整体思路，采用数值建模、宏-微观试验与理论分析相结合的方法，开展应力-化学耦合作用下的防渗墙性能演化研究。在数值仿真再现防渗墙真实工作状态的基础上，研究服役过程中防渗墙应力状态和应力路径；通过开展应力-化学耦合作用下的室内实验，揭示防渗墙老化过程中宏观性能演化规律；应用扫描电镜等细微观手段，研究表征混凝土损伤微观参数的演化规律，揭示应力-化学耦合作用下混凝土性能演化机理；探讨混凝土损伤微观参数与其宏观性能演化的相互关系及其调控机制，建立防渗墙墙体损伤及其性能演化模型，为防渗墙服役期内安全性评价和提高混凝土耐久性提供科学依据。

混凝土防渗墙是覆盖层上大坝防渗体系的生命线工程，它在服役过程中存在高围压、高渗透梯度以及库水位周期性升降的物理作用和环境水侵蚀的化学作用，导致防渗墙长期服役性能发生劣化。本项目以两端固嵌式的素混凝土防渗墙为研究对象，研究其在应力-化学耦合作用下性能演化规律。基于有限单元法数值仿真技术，再现了混凝土防渗墙的应力状态，并提出了基于区间分析的防渗墙应力状态研究方法，构建了考虑泥皮的防渗墙接触面损伤模型；为了探究复杂运行环境下的混凝土的渗透性能演化规律，对水泥砂浆和水泥基质的渗透特性进行了研究，得到了在高渗压的溶蚀作用下的渗透系数与孔隙率的演化规律；为了研究应力-化学耦合作用下的混凝土性能演化规律，开展了针对常态混凝土和碾压混凝土在冻融作用、硫酸盐侵蚀以及高渗压等运行环境下的性能演化研究工作，并探讨了养护环境对水工混凝土性能的研究规律。针对混凝土防渗墙无法直接现场检测其性能演化规律的困难，考虑到面板堆石坝的混凝土面板同样也是防渗结构，因而结合水布垭面板堆石坝，研究了其在长期运行后的性能演化规律，为防渗墙结构提供参考。依托本项目，培养硕士研究生7名，发表学术论文5篇，申请获批专利18项，获批软件著作权3项，参加国内外学术会议8次。通过本课题项目的研究，不仅对于服役环境下混凝土防渗墙长期安全性的评价，还是对未来防渗墙混凝土改性，延长防渗墙的使用寿命，都是有重大的理论和现实意义。