酸雨入渗作用下残积膨胀土湿胀各向异性机理与理论模型研究

酸雨与土体间的水土化学作用会导致浅表层土体的物理力学性质改变，给边坡、基础工程、轻型结构物及生态环境带来极大危害。现有从湿胀各向异性入手的膨胀土工程地质问题研究，往往忽略大气污染地区酸雨侵蚀对边坡破坏的促进作用。为此，本项目考虑酸雨入渗实际工况，针对膨胀土边坡土体竖向与临空面侧向湿胀异性，研发动态水环境下的膨胀土变形测试装置，开展酸雨入渗下残积膨胀土湿胀变形试验，探究残积膨胀土湿胀各向异性规律；采用多种微观测试技术，分析其微结构、矿物与化学成分演变规律；结合分形及水土化学作用等理论，阐明其湿胀异性微观机制及水土化学作用原理，并提出微结构异性率指标的计算方法,从微观及水化学角度深入揭示酸雨入渗下残积膨胀土湿胀各向异性机理;在此基础上，构建描述酸雨区残积膨胀土湿胀变形的理论模型，为酸雨区膨胀土边坡灾害防治设计提供理论支撑，亦可为水土化学作用下其它类型地质体的致灾机理研究提供有益参考。

The chemical water-soil interaction between acid rainfall and soil will change the physical and mechanical properties of shallow soils, which subsequently brings great harm and adverse effects on the slope, foundation, light structure and ecological environment. However, the existing studies of the anisotropic wetting-expansion characteristics of expansive soils often ignore the contribution of acid rainfall erosion on the slope failure in the areas with air pollution. Herein, this project develops a deformation testing device for expansive soils under dynamic water environments with the consideration of the actual working conditions of acid rainfall infiltration, aiming at the anisotropy wetting-expanding characteristics between the vertical and free lateral side of the expansive soil slope,. The wetting-expansion deformation tests are carried out on expansive soil under acid rainfall infiltration to explore the anisotropic wetting-expansion characteristics of residual expansive soil. The evolution laws of microstructure, mineral and chemical composition of expansive soil are analyzed using a variety of micro test methods. Combined with the theory of fractal and water-soil chemistry, the micro mechanism of anisotropic wetting-expansion and the principle of water-soil chemical interaction are clarified, and the calculation method of the anisotropic microstructural index is proposed. Meanwhile, the mechanism of anisotropic wetting-expansion of residual expansive soil under acid rain infiltration is revealed from micro and hydrochemical aspects. On this basis, a theoretical model describing the wetting-expansion deformation of residual expansive soil in acid rain areas is established considering the effects of anisotropic wetting-expansion, microstructural anisotropy and chemical water-soil interaction. The research results provide a theoretical support for the design and treatment of residual expansive soil slope in acid rainfall areas. Simultaneously, it can provide a useful reference for the research on the disaster mechanism of other types of geological bodies under the chemical water-soil interaction.