作为我国高速铁路主要轨道结构形式之一，中国铁路轨道系统(CRTS) II型板式无砟轨道结构已在京沪、石武、沪昆高铁上得到广泛使用。由于列车、温度荷载等的长期作用，其性能具有时变性和随机性；水泥乳化沥青砂浆(CA砂浆)位于该多层空间轨道结构的中间，且部分出现病害，故亟需开展II型板式无砟轨道结构力学性能随机性与时变性研究，即主要揭示其随机疲劳损伤机理与性能随机演化规律。本项目基于多尺度统计力学，拟开展CRTS II型板式无砟轨道结构随机疲劳损伤行为研究，通过统计力学方法，提出考虑尺寸效应的II型CA砂浆随机疲劳损伤本构模型，并通过概率密度演化方法，建立高速铁路桥上II型板式无砟轨道结构随机疲劳损伤行为多尺度理论分析模型，研究该结构疲劳失效模式，揭示其随机疲劳损伤机理，进而揭示其随机疲劳损伤演化规律。研究成果将为II型板式无砟轨道结构疲劳损伤分析、安全运营与养护维修，提供理论依据与技术指导。

As a main track of the high-speed railway tracks in China, the China railway track system (CRTS) II ballastless slab track has been vastly applied in the Beijing-Shanghai, Shijiazhuang-Wuhan and Shanghai-Kunming high-speed railway. Due to the long-term effects of trains and temperature loads, etc., its performance is time-varying and random. The cement emulsified asphalt mortar (CA mortar) layer is located in the middle of this spacial multi-layer track structure, and some CA mortar layer surfers the varied diseases. Hence, it is urgent to study on the randomness and time-variability of mechanical properties of CRTS II ballastless slab track structure, i.e. mainly to reveal the random fatigue damage mechanism and the stochastic evolution of its performance. Based on the theory of multi-scale statistical mechanics, this project is proposed to study on the random fatigue damage behavior of CRTS II ballastless slab track structure under fatigue load. Initially, based on a statistical mechanics method, a stochastic fatigue damage constitutive model of CRTS II CA mortar considering size effect is proposed. Additionally, using a probability density evolution method, a multi-scale theoretical analysis model for the random fatigue damage behavior of CRTS II ballastless slab track structure on the high-speed railway bridge under fatigue load is developed. Furthermore, the fatigue failure mode, the random fatigue damage mechanism and the stochastic fatigue damage evolution law of the track structure are revealed by applying the analysis model. Therefore, the research results can be applied to provide theoretical basis and technical guidance for the fatigue damage analysis, safe operation and maintenance of CRTS II ballastless slab track structures.