干湿循环条件下重载铁路路基动力损伤评价与演化机理

Dynamic train load and wetting-drying cycles on soil are the main causes of heavy haul railway subgrade diseases, and the performance evolution and disease mechanism of subgrade subjected to these two factors are in urgent need of systematic and further study. Soil damage occurs during the formation of subgrade disease. It is meaningful to learn the variations of meso-structures and characteristics of subgrade soil for revealing the essence of macro-scale behaviors. This project is going to perform a series of theoretical and experimental studies, sticking to the key scientific problem of evolution mechanism of dynamic damage of heavy haul railway subgrade under cyclic wetting-drying. Considering the characteristics of heavy haul train, track and subgrade structures, a coupled train-ballasted rail-layered subgrade semi-analytical model is going to be established, and dynamic response of subgrade due to heavy haul train load would be studied for designing the experimental plans of soil dynamic tests. Cyclic wetting-drying test considering different cycles and amplitudes is going to be conducted. Then, dynamic triaxial tests together with measurements of electrical resistivity and CT parameters would be carried out on specimens after wetting-drying cycles. A multi-scale damage evaluation method for subgrade soil based on macro-meso damage variables would be proposed to reveal the damage evolution law of heavy haul railway subgrade under cyclic wetting-drying. Finally, in order to better understand the mechanism of subgrade diseases, a dynamic damage evolution model for subgrade soil under cyclic wetting-drying is going to be established, and it can be the theoretical basis of prevention and treatment of subgrade diseases and maintaining of long-term performance of heavy haul railway subgrade.

列车动荷载与土体干湿循环效应是引起重载铁路路基病害的主要因素，二者耦合作用下的路基性能演化及致灾机理亟需深入、系统研究。土体损伤伴随于路基病害形成过程，认识此过程中路基土体细观结构和性状变化，有助于从本质上揭示宏观现象。本项目紧紧围绕干湿循环条件下重载铁路路基动力损伤演化机理这一关键科学问题展开一系列理论和试验研究。考虑重载列车、轨道及路基结构层特点，建立重载列车-有砟轨道-层状路基耦合模型，得到重载列车作用下路基动力响应，并以此确定动力学试验方案。通过对经历不同次数和幅度干湿循环试验后的路基土开展动三轴试验，同时进行电阻率测试及CT扫描，提出基于宏细观损伤变量的路基土多尺度损伤评价方法，研究干湿循环条件下重载铁路路基损伤演化规律。最终，建立干湿循环条件下重载铁路路基动力损伤演化量化模型，揭示路基病害产生机理，为路基病害防治及保证重载铁路路基长期性能提供理论指导依据。

列车动荷载与土体干湿循环效应是引起重载铁路路基病害的主要因素，对二者耦合作用下路基性能演化及致灾机理亟需深入、系统研究。土体损伤伴随于路基病害形成过程，认识此过程中路基土体细观结构和性状变化，有助于从本质上揭示宏观现象。针对以上问题，本项目建立了列车-有砟轨道-层状路基耦合动力学分析模型。对路基土样开展了不同循环次数和循环幅度条件的干湿循环试验，再对经历不同干湿循环条件的土样开展了动三轴试验，得到了路基土的累积塑性应变、动模量随循环荷载次数的发展规律，分析了干湿循环作用对路基动力特性的影响规律。提出了一种土体室内电阻率的测试装置及方法，对经历不同干湿循环与动荷载条件的路基土开展了电阻率测试，得到了干湿循环及动荷载条件对路基土体电阻率特性的影响规律，建立了电阻率与宏观力学指标之间的关系。基于CT图像开展了不同干湿循环条件下重载铁路路基动力损伤演化量化分析，揭示了路基土损伤演化机理。本项目可为我国重载铁路路基长期服役性能评价及路基灾害防治提供了一定理论基础。