高速列车荷载作用下路堤填料（粗粒土）疲劳损伤-蠕变变形耦合分析

Differential settlement of high-speed railway subgrade is a fatal factor which influences the safety of high-speed trains. This project plans to carry out triaxial creep tests on coarse-grained subgrade filling, improve and perfect nonlinear creep models for coarse-grained soil. Based on the characteristics of high-speed train load, dynamic triaxial tests on subgrade filling will be conducted, and the mechanism of particle breakage and fine-particle migration will be explored. According to the level of particle breakage, a dynamic damage variable will be defined, and the dynamic damage evolution law of coarse-grained soil will be studied. This project will analyze the relationship between dynamic fatigue damage and creep deformation caused by static load, build dynamic fatigue damage and creep coupling model for coarse-grained soil through coupled superposition, and then perfect the existing calculation methods for long-term settlement of subgrade and apply them in practice. Using existing track-subgrade dynamic load simulation test system, full-scale model test will be conducted to verify the theory, and improve the coupling model and subgrade deformation analysis method. This project aims at exploring the solution to a worldwide problem- - calculating the long-term settlement of high-speed railway subgrade, and providing technical guidance to the design and construction of high-speed railway. Meanwhile, results of this research can be extended to predict long-term settlement of highway subgrade and analyze the stability or deformation of geotechnical structures under dynamic load such as earthquake.

高速铁路路基的不均匀沉降对高速列车的安全运行至关重要。本课题开展粗粒土路堤填料的大型三轴蠕变实验，改进和完善已有的非线性蠕变模型。针对高速列车动力荷载特点，对路堤填料（粗粒土）开展大型动三轴实验研究，探索路基填料的颗粒破碎与细颗粒迁移规律，基于颗粒破碎程度来定义粗粒土动力损伤变量，分析粗粒土动力损伤演化规律。研究动力疲劳损伤和静荷载形成的蠕变变形之间关系，通过耦合叠加，建立基于损伤与细颗粒迁移的粗粒土动力疲劳损伤-蠕变耦合模型，进而完善现有的路基长期沉降变形分析方法并进行工程应用。利用现有的轨道路基动力模拟实验系统开展路基足尺模型实验进行验证，进一步完善耦合模型和路基变形分析方法。从根本上探索高速铁路路基长期沉降预计这一世界性难题的解决方法，为高速铁路的设计与施工提供技术指导。同时其研究成果可推广应用于公路路基长期沉降预计以及地震等动力荷载作用下的岩土工程稳定与变形分析。

本课题针对高速列车动力荷载特点，开展了系统的路堤填料（粗粒土）动三轴实验研究，基于实验，研究了路堤填料（粗粒土）动力疲劳变形与循环荷载次数的关系，探索了路基填料的颗粒破碎规律与细颗粒迁移机理，初步得出了动力累积变形、（粗粒土）动力参数、破碎程度之间的联系。开展了红砂岩（粗粒土）水解试验、动力特性和颗粒破碎试验，初步得出了红砂岩（粗粒土）水解特性、颗粒破碎程度与路基累积变形的关系。利用现有的轨道路基动力模拟实验系统，开展了路基足尺疲劳动力模型实验研究与验证，深入分析了路基在填筑期、静置期和运营期（动力作用）的沉降特点和规律，对现有的路基长期沉降变形分析方法进行了部分改进。研究成果可为高速铁路的设计与施工提供技术指导。同时可推广应用于公路路基长期沉降的预计与分析。