粗颗粒土双进气值土水特征曲线及强降雨条件下高铁路基水分运移规律

Surface water infiltration under the condition of heavy rainfall has caused subgrade mud pumping, bed rushing diseases of existing high-speed railways in China. In the process of compaction, the micro dual-pore structure of subgrade coarse-grained soils makes the soil-water characteristic curve (SWCC) present obvious dual air-entry-value (AEV). This phenomenon influences the moisture migration in the subgrade. Aiming at water infiltration and migration in the high-speed railway subgrade under heavy rainfall, large-diameter volumetric suction plate apparatus to measure SWCCs of coarse-grained soils will be developed. Experiments will be conducted to measure bimodal SWCCs and permeability coefficient under different conditions of compactness, fine-particles percentage and grain grading. The theoretical expression of bimodal SWCC and permeability coefficient will be proposed. On this basis, theoretical model of moisture migration in the high-speed railway subgrade will be established to reveal the laws of moisture distribution and water capsule formation of the subgrade. And this theoretical model will be verified through full-scale model tests of high-speed railway subgrade. Finally, suggestions on the design of the subgrade structure, waterproof and drainage facilities will be given. Research of this project will provide technical support for subgrade design of new high-speed railways and water disease renovation of existing high-speed railways.

强降雨条件下地表水入渗造成已运营高铁路基翻浆冒泥、道床冲空等病害。路基粗颗粒土压实过程中形成的微观双孔隙群结构特征使得土水特征曲线存在明显的双进气值，影响到路基水分运移。针对强降雨条件下高铁路基水分入渗及运移问题，研发用于路基粗颗粒土土水特征曲线测试的大直径体积压力板仪，试验研究不同压实度、细颗粒含量和级配条件下路基粗颗粒土双进气值土水特征曲线和非饱和渗透系数的变化规律，提出粗颗粒土双进气值土水特征曲线及渗透系数的表达式；在此基础上建立高铁路基水分运移理论分析模型，揭示强降雨条件下路基水分分布规律及路基水囊形成机理，通过高铁轨道路基足尺物理模型试验验证理论模型的合理性，最终提出路基结构层和防排水设计建议。本项目研究将为我国新建高铁路基设计及已建高铁路基水害整治提供技术支撑。

本项目以高速铁路路基为研究对象，针对路基粗颗粒土的水力学特性和强降雨条件下路基内部水分运移这一难题，展开相关研究。在试验方面，开展了路基土μCT、SEM和压汞等微观结构试验，揭示了路基土双孔隙微观结构特征；研制了适用于路基土的TDR探头和大直径渗透柱装置，实现了路基土含水量和水力学特性的测试。开展了不同压实度、不同细颗粒含量路基土的大直径渗透柱实验和压力板试验，获得了路基土双进气值土水特征曲线特性随压实度和细颗粒含量变化的规律，并从微观孔隙结构角度揭示了变化机理，提出了描述路基土双进气值土水特征曲线理论模型。建立了强降雨条件下路基内部水分运移理论分析模型，获得了路基内部水囊形成及运移的规律，提出了路基“水囊”防治方法。