引水隧洞衬砌HMC耦合作用下劣化机理及其长期稳定性研究

Lining diseases, i.e. cracks, leakage and erosion damage, are often observed in hydraulic tunnels during emptying inspection, and generate a direct impact on the quality and service life of hydraulic engineering. Different from the concrete structure on the ground, the concrete service environment of the hydraulic tunnel has its special characteristics, in-situ stress, internal and external head pressure and aggressive water environment have a decisive influence on its long-term stability. A series of laboratory tests will be performed to reveal the influence mechanism of erosive ions, in-situ stress and internal and external head pressure on the concrete from the perspective of microstructure. An elastic damage mechanical model and concrete erosion model will be developed and a chemical damage variable will be defined based on the experiments and analysis, and a hydraulic-mechanical-chemical coupling model of concrete will established after investigation of the influence mechanism of stress and water pressure on the mechanical behavior, permeability, effective stress coefficient and diffusion coefficient. Consequently, a numerical method of long-term stability analysis and evaluation of concrete lining structure under the action of stress, head pressure and erosion will be developed. Finally, some guidance for the design and construction of concrete lining of diversion tunnel will be proposed combined with Lanzhou water source construction project. The research results can provide theoretical and technical support for the quality and safe operation of large hydraulic engineering in China.

引水隧洞放空检查时经常发现衬砌裂缝、渗漏水和侵蚀破坏等病害，直接影响到水利工程的质量和服役寿命。不同于其他混凝土结构，引水隧洞混凝土服役环境较为特殊，围岩应力、内外水头压力和侵蚀性水环境对其长期稳定性具有决定性的影响。拟采用岩石力学的方法，开展一系列室内试验，从微细观结构角度逐步揭示围岩应力、内外水头压力、侵蚀离子各自及其耦合作用对混凝土的影响机理；在试验和分析的基础上，建立描述力学行为的弹性损伤力学模型和混凝土侵蚀作用模型，引入化学损伤，分析应力和孔隙水压力对混凝土的力学行为、渗透率、有效应力系数和扩散系数等的影响机理，建立混凝土应力－渗流－侵蚀耦合理论模型；采用有限元方法，提出围岩应力、水头压力和侵蚀作用下衬砌结构长期稳定性分析和评价方法；结合兰州水源地建设工程，为引水隧洞衬砌的设计和施工提供指导性建议。研究成果可为我国大型水利工程的质量和安全运行提供理论和技术支持。

引水隧洞放空检查时经常发现衬砌裂缝、渗漏水和侵蚀破坏等病害，直接影响到水利工程的质量和服役寿命。不同于其他混凝土结构，引水隧洞混凝土服役环境较为特殊，围岩应力、内外水头压力和侵蚀性水环境对其长期稳定性具有决定性的影响。为此，针对引水隧洞混凝土衬砌在地应力、水头压力和地下水侵蚀环境等复杂条件下的长期稳定性问题，开展了一系列混凝土物理、力学、渗透率测试试验、耦合侵蚀室内试验和相关的数值模拟。1）从微观特性（渗透率、SEM、波速、孔隙率、CT扫描）和宏观力学性能（单轴、劈裂抗拉）两个角度揭示了硫酸盐侵蚀下水泥砂浆劣化机理；2）研究了混凝土衬砌在地下复杂环境下和碳酸侵蚀下混凝土微观孔隙结构的演化规律；3）开展了地应力和多种侵蚀性离子（经复合溶液、硫酸钠溶液、氯化钠溶液）耦合作用下引水隧洞混凝土衬砌力学特性影响进行研究，为复杂侵蚀性环境下引水隧洞长期稳定性分析提供理论依据；4）针对混凝土试样开展了应力-化学-渗流耦合侵蚀试验，揭示了地应力、内外水头压力和侵蚀性水环境三者对混凝土衬砌的耦合作用机理；5）建立了复杂应力状态下硫酸根离子和力学荷载耦合作用下混凝土应力－渗流－侵蚀耦合理论模型，借助多场耦合模拟软件COMSOL模拟了受硫酸根离子侵蚀的隧洞混凝土衬砌的损伤劣化过程，为分析引水隧洞长期稳定性提供了有效的方法和手段。研究成果可为我国大型水利工程中引水隧洞混凝土衬砌的设计、施工和维护提供重要的科学依据和技术支持。