滨海地区砂土地基广布且水文气候地质条件复杂，基础设施极易发生渗蚀灾变。现有理论和试验多从宏观尺度提出砂土渗蚀形成及发展的定性规律和经验性判别方法，尚无成熟的土体渗蚀宏细观力学特性理论体系，也少有考虑水土耦合的渗蚀演化过程数值模拟成果。本项目围绕暴雨等强渗流作用下砂土渗蚀诱发近水基础设施地基及结构失效灾变问题展开研究，以数值模拟及室内试验为基础，凝练影响渗蚀发展及砂土力学特性改变的关键因素，提出复杂应力场和渗流场作用下各向异性砂土渗蚀启动准则；基于宏细观流固耦合分析，揭示砂土结构改变及其导致的力学特性演化机制；在此基础上，采用离散元与有限元耦合方法并引入砂土颗粒渗蚀损失机制，再现渗蚀诱发的砂土地基整体沉降及堤坝失效灾变全过程。本项目可实现从砂土细观结构演化到宏观失稳灾变的跨尺度表征，预期研究成果可为近水基础设施地基及结构渗流灾变防控设计提供依据，具有重要的科学理论价值和工程应用前景。

Coastal areas are rich in sand foundation as well as complex climatic and geological conditions. Under such circumstances, soil structures are prone to catastrophic failures. Many studies have been focused on the macroscopic perspectives of the initiation and development of internal erosion via soil element testing and continuum-based modeling. However, the micromechanical processes of internal erosion and soil-water coupling are rarely studied and thus requiring further investigation. This project mainly focus on the instability evaluation of sand foundation and structures of offshore infrastructures due to internal erosion under heavy rainfall. By applying the results of numerical coupling simulations and physical experiments methods, this project aims at figuring out the keys regarding to the development and mechanical consequences of internal erosion, formulating criterion of initiation of internal erosion under complex stress and seepage conditions, and revealing the basic principles of the microstructural changes and evolution of mechanical properties subjected to internal erosion. Based on these results, the project further develops the coupled discrete element and finite element method by introducing the particle removal scheme considering internal erosion. The failure process of sand foundation and embankment dams due to internal erosion are expected to be reproduced. This project are expected to bridge the microstructural deformation and macroscopic instability process. The outcomes are expected to provide a significant guidance for the design of seepage preventions, and safety evaluation of offshore infrastructures under intense water infiltration to improve the engineering towards potential hazards.