无砟轨道水致劈裂-冲刷效应耦合作用机制

he water damage of ballastless track is an important factor in affecting its durability, its essential is the damage development process of concrete and CA mortar caused by the coupling effect of cleavage and erosion of the ballastless track subjected to the collective action of train load and water. The research on the development mechanism of the water damage of ballastless track under high-frequency dynamic load is not in-depth. Thus, the test of softening cementitious materials, the test of material surface erosion, the material penetration test and the model test of coupling effect of cleavage and erosion will be conducted in this project. Based on the facture mechanics, the damage mechanics, the fluid-structure interaction theory and the microcosmic finite element method, the calculation models of erosion for ballastless track under the hydrodynamic pressure will be established to analyze the influence of the load characteristic on the erosion rate. The erosion damage mechanism of ballastless track caused by water will be carried out. Then, the water damage development model of ballastless track considering the coupling effect of the cleavage and erosion will be built to analyze the variation rule of the crack propagation rate, the erosion rate and the crack morphology and clear the coupling mechanism of the cleavage and erosion effects of ballastless track under the hydrodynamic pressure. Finally, the calculation theory and method of the development of water damage for ballastless track under the action of high-frequency train load and water will be established. The research will provide theoretical bases to clear the evolution law of ballastless track caused by water damage and evaluate the service performance of different state of ballastless track.

无砟轨道水致损伤是影响其耐久性的重要因素，该问题的实质是列车荷载与水共同作用下混凝土、CA砂浆在劈裂和冲刷效应耦合作用下的损伤发展。国内外对高频动载下无砟轨道水致损伤发展机理的研究还不够深入。本项目拟开展水泥基胶凝材料软化试验、材料表面冲刷试验、材料浸水渗透力试验、无砟轨道劈裂-冲刷耦合作用模型试验，应用断裂力学、损伤力学、流固耦合理论和细观有限元方法，建立动水压力作用下的无砟轨道冲刷计算模型，分析冲刷速率与荷载特征之间的关系，探明无砟轨道冲刷损伤机理；建立无砟轨道水致劈裂-冲刷效应耦合作用计算模型，分析裂缝扩展速率、冲刷速率及裂缝形态的变化规律，明确动水压力作用下无砟轨道劈裂-冲刷效应耦合作用机制。建立列车荷载与水共同作用下的无砟轨道水致损伤发展计算理论和方法。为明确无砟轨道水致损伤演化规律，评估不同状态无砟轨道的服役性能提供理论基础。

无砟轨道伴随我国高速铁路大规模修建得到了广泛的应用，但在列车荷载与复杂环境因素影响下损伤问题也逐步凸显，特别是雨水丰富和排水不畅地区，无砟轨道水损伤较为严重。本项目针对典型无砟轨道水环境损伤问题，对高速列车复杂动荷载作用及雨水侵入条件下，无砟轨道层间离缝损伤发展机理进行理论与试验研究。通过现场调研，明确无砟轨道的水病害特征，并提出无砟轨道水致损伤的关键科学问题和计算方法。基于湿度扩散理论，建立无砟轨道湿度场计算模型。在无砟轨道湿度场分布特性的基础上，分析了无砟轨道混凝土微观结构特征，应用多尺度力学，分析了不同湿态混凝土基本微观参数，采用混凝土净孔结构的“有效饱和度”，利用两级均匀化法实现了对不同湿度(饱和度)混凝土宏观力学性能的准确预测，为进一步开展动水压力及无砟轨道水致损伤提供支撑。基于质量守恒、动量定理，采用控制体积法建立列车荷载作用下无砟轨道层间离缝内动水流速分析计算模型。在此基础上，设计无砟轨道水冲刷模拟工装，通过数值模拟与试验实测分析，明确加载频率、加载幅值、离缝高度和距出口距离对水流速的影响，根据层间离缝内动水流速的测量值与计算值，计算分析离缝内混凝土的冲蚀作用开展层间裂纹内动水流速。根据层间离缝内动水流速的测量值与计算值，计算分析离缝内混凝土的冲蚀作用。在无砟轨道水力冲刷的研究基础上，考虑到无砟轨道作用的环境复杂性，开展混凝土浸泡溶蚀试验，建立无砟轨道钙溶蚀理论模型和有限元实体模型，研究水致溶蚀作用机理。利用有限元、颗粒离散元法并结合试验研究了脱粘处的无砟轨道层间接触损伤，探究无砟轨道层间离缝在荷载作用下发展初期的损伤成因。研究成果将为进一步丰富和完善混凝土损伤理论及无砟轨道的养护维修提供理论依据。