多场耦合作用下垃圾渗滤液对隧道支护结构的腐蚀机理研究

The corrosion of landfill leachate on lining structures of tunnel that pass through waste landfill site is a very complex physical and chemical process. In view of a lack of deeply understanding the corrosion mechanism of landfill leachate on tunnel lining structures, Luodai tunnel in Chengdu, China is taken as research background, the corrosion mechanism of landfill leachate on tunnel lining structures under the action of multiple filed coupling is studied by means of laboratory and field experiments, physical model test, theory research methods and numerical simulations. Firstly, water chemical analysis is conducted to analyze the main components in landfill leachate, and to determine the content of the main element that will corrode tunnel lining structures such as rock bolt, shotcrete lining, and the secondary lining. Then the laboratory and field corrosion experiments will be conducted, and the SEM will be adopted to observe the surface appearance changes of tunnel lining structures and to reveal the corrosion mechanism of landfill leachate. The rule of the physical and mechanical parameters of tunnel lining structures changing with corrosion time and landfill leachate concentration can be established based on the results of laboratory experiments, and the mechanical damage model of tunnel lining structures with corrosion time is established. The physical model test is conducted based on the coupling of stress filed, seepage field and chemical field, which aims to reveal the corrosion mechanism of landfill leachate and to establish the corrosion mathematical model under three fields coupling. COMSOL Multiphysics is a large advanced numerical simulation software and is widely used in scientific research and engineering calculation in various fields. Partial differential equations of different physical fields are established and imported to COMSOL Multiphysics to analyze the safety factor and durable life of tunnel lining structures under the long-term corrosion of landfill leachate. The future research results will enrich innovatively the basic theory of landfill leachate corrosion mechanism on tunnel lining structures under multiple filed coupling.

垃圾渗滤液对下穿垃圾填埋场隧道支护结构的腐蚀是一个非常复杂的物理化学过程。鉴于目前缺乏垃圾渗滤液对隧道支护结构腐蚀机理的深入认识，以洛带隧道为背景，采用试验、理论研究及数值模拟等方法，开展多场耦合作用下垃圾渗滤液对隧道支护结构的腐蚀机理研究。首先进行水化学分析，分析垃圾渗滤液的主要构成，辨识其中主要的腐蚀成分。进而开展腐蚀试验，利用SEM微观扫描揭示其腐蚀机理，分析渗滤液浓度、腐蚀时间对隧道支护结构物理、力学参数的影响规律，建立隧道支护结构力学损伤模型。开展应力场-渗流场-化学场耦合下腐蚀模型试验，揭示三场耦合作用下垃圾渗滤液对隧道支护结构的腐蚀机理，建立垃圾渗滤液对隧道支护结构腐蚀的数学模型，以多场耦合软件Comsol Multiphysic为平台编写分析程序，分析垃圾渗滤液腐蚀作用下隧道安全系数和耐久性寿命。研究成果将丰富并创新多场耦合作用下垃圾渗滤液对隧道支护结构腐蚀机理的基础理论。

以隧道近距离下穿垃圾填埋场为研究背景，采用现场调研及测试、室内试验、理论分析和数值模拟相结合的方法，对多场耦合作用下垃圾渗滤液对隧道支护结构的腐蚀机理开展研究。. 主要研究内容包括：隧道下穿垃圾填埋场对垃圾渗滤液运移规律的影响，垃圾渗滤液对隧道支护结构的腐蚀机理及隧道支护结构的力学损伤本构模型，垃圾渗滤液对隧道支护结构腐蚀的应力场-渗流场-化学场三场耦合机制，下穿垃圾填埋场隧道长期稳定性评价研究。.重要研究结果：(1)建立了隧道开挖前、后隧址区地下水流模型，分析了垃圾渗滤液在地层中的运移规律； 得到了硫酸盐腐蚀环境岩石的渗透系数，获得了应力场-渗流场耦合作用下隧道对地下水流及溶质运移的影响规律； 揭示了化学场-渗流场耦合作用下隧道对垃圾渗滤液运移路径的影响规律。(2)结合经典的多孔材料孔隙分类方法，提出了一种新的水泥基材料内部细观孔隙的分类方法；采用多尺度分析方法，揭示了硫酸盐对喷射混凝土的侵蚀机理，获得了水灰比、暴露方式和暴露时间对侵蚀机理的影响规律；揭示了水灰比和暴露方式条件下喷射混凝土剪切性能的长期演化特征及喷射混凝土强度参数随硫酸盐暴露时间的演变规律。(3)获得了硫酸盐环境喷射混凝土力学特性随时间变化规律，提出了其力学性质随时间变化的表达式；揭示了喷射混凝土在硫酸盐长期腐蚀下的劣化规律，建立了喷射混凝土剪切强度劣化公式；以能量指标定义了喷射混凝土弹性阶段和塑性阶段的损伤变量，提出了硫酸盐腐蚀作用下的喷射混凝土弹塑性损伤本构模型并进行了验证。. 关键数据及其科学意义：获得了隧道近距离下穿垃圾填埋场前后隧址区地下水水化学数据，不同水灰比、暴露方式和暴露时间硫酸盐对喷射混凝土侵蚀试验数据，硫酸盐环境喷射混凝土强度试验数据等关键数据。对多场耦合作用下地下水及垃圾渗滤液运移规律、硫酸盐环境混凝土材料的耐久性及隧道支护结构的长期稳定性研究具有重要的科学意义。