高速铁路粗粒土填料微观组构与冻胀机理研究

At present, China's high-speed railway is in a rapid development stage, and the operating mileage of high-speed railway applied in cold regions has exceeded 5500km. Frost heaving is the most basis and nucleus problems. Even if a series of measures taken, there is a certain degree of frost heave and thaw settlement of these lines in the period of construction and operation, which means a higher challenges to maintenance. The phenomenon of subgrade frost heaving contradicts the traditional ideas that the coarse-grained soil is less likely to Frost heaving. The macroscopic frost heave rule and the main influencing factors have been mastered by the frost heave monitoring and related experiment in recent years. However, the frost heaving of the roadbed packing has not been explained from the mechanism. In this project, we will study the structural changes of the components in the coarse-grained soil during the one-way freezing process through X-CT microscopic scanning, nuclear magnetic resonance, frost heave test and other means of combining methods. In addition, this project analyzes the occurrence of moisture in filler and the transportation law in the process of freezing and in the theoretical view to explain and modeling to preliminarily build frost heave theory application to coarse-grained soil filler. Therefore, it is of great theoretical significance to study the mechanism of frost heaving of high-speed railway coarse-grained soils in seasonal frozen soils, and to guide the design, construction and maintenance of high-speed railway bedding to reduce and prevent the freezing damage of roadbeds and to further improve the theory of permafrost.

目前，我国高速铁路处于全面发展阶段，其中严寒地区高铁运营里程已经超过5500km，路基冻胀是寒区高铁最基础、最核心的问题。虽然采取了一系列的措施，但这些线路在建设和运营期均出现了一定程度的冻胀变形，对安全运营提出了挑战。路基填料冻胀现象与传统冻胀理论相悖，通过近几年冻胀监测和相关试验研究，已经初步掌握了其宏观冻胀规律及主要影响因素，但迄今尚未从机理上阐明粗粒土冻胀现象。本项目将通过X-CT微观扫描、核磁共振、冻胀试验等多种手段相结合的方法，研究单向冻结过程中粗粒土填料中各组分的的组构变化特征，分析水分在填料中赋存状态和冻结过程中的迁移规律，初步构建适用于粗粒土填料的冻胀理论。综上所述，开展季节性冻土区高速铁路粗粒土填料冻胀机理研究，对指导高速铁路基床结构设计、施工及维护，减少和防治路基冻害，完善冻土理论，都具有重要的理论意义和实用价值。

我国多条高速铁路穿越了冻土广泛分布的高寒地区，高铁建设和运营过程中将面临着一系列抗冻防寒等诸多问题。路基冻胀会影响铁路的平顺性和乘坐舒适度，更为严重的是影响列车的行驶安全，大大增加了铁路工务部门的线路维护工作量。为此开展高寒地区高铁路基粗粒土微观组构及其冻胀机理研究具有重要的意义。本研究借助室内宏、细观试验、理论分析等手段开展了一系列寒区铁路路基粗粒土的冻胀特性研究。借助室内试验，掌握了水泥稳定碎石填料的反复冻胀、融沉特性。研究和分析了冻融、细粒土含量、围压等因素对路基粗粒土填料物理、力学特性的影响规律，并给出冻土地区铁路路基粗粒土填料的合理细粒含量建议值。阐明了不同级配粗粒土中细粒组分在粗粒土中的赋存状态及团聚特征；分析了冻结前后不同级配粗粒土填料中的粗颗粒、细颗粒以及孔隙在填料试样中的分布特征以及水分在填料冻结前后的赋存状态。研究了细颗粒组分在粗粒土中的团聚特征，掌握了冻结前后的粗颗粒与细颗粒、细颗粒与冰晶之间的相互作用，以及冻胀引起的孔隙变化特征，分析了粗粒土冻结过程中水分迁移规律。基于能量守恒定律、质量守恒定律等基本定律，建立了适用于粗粒土填料的水热耦合微分方程，用于描述粗粒土填料的温度场、水分场变化规律，并构建了高铁路基粗粒土冻胀变形的计算模型。相关的研究成果可为高速铁路基床结构设计、施工维护，减少和防治路基冻害提供指导，有助于进一步完善冻土理论。