湿度影响下双块式无砟轨道道床板新旧混凝土界面力学特性研究

Study on Mechanical Properties of Interface between Old and New Concrete of Double-block Ballastless Track Bed Slab under the Influence of Humidity

在湿度影响下,混凝土的力学性能会随其内部不均匀的湿度场产生不同程度的变化,故水环境中的双块式无砟轨道各混凝土部件(轨枕、道床板及支承层)内部的材料性能存在差异,在长期荷载作用下易产生伤损。因此,探明由湿度导致材料性能变化对水环境中无砟轨道局部力学行为及损伤所带来的影响,对研究无砟轨道水致损伤形成和发展机理具有一定参考价值。通过建立双块式无砟轨道有限元实体模型,对水环境中双块式无砟轨道道床板新旧混凝土界面位置处的应变分布及疲劳损伤情况进行分析。结果表明:考虑湿度影响后,水环境中双块式无砟轨道道床板新旧混凝土界面位置处的变形性能与抗疲劳特性均有一定程度的削弱,长边接触面所受影响最为显著,其最大主拉应变增长31.6%,剪切疲劳寿命减短30.4%,出现在该面中上方位置,该处将是裂纹较早萌生的位置。

Under the influence of humidity, the mechanical properties of concrete vary with its uneven humidity field inside. Therefore, the material properties of the concrete components(double-block sleeper, track slab and support layer) of double block ballastless track in water environment also appear differences, which is likely to be damaged under long-term load. Therefore, it is of certain reference value to study the formation and development mechanism of water-induced damage of ballastless track to explore the impact of the change of material properties caused by humidity on the local mechanical behavior and damage of ballastless track in water environment. By establishing the finite element solid models of double-block ballastless track, the strain distribution and fatigue damage at the interface between the new and old concretes of the double-block ballastless track bed slab in the water environment are analyzed. The results show that, given the influence of humidity, the deformation performance and anti-fatigue properties of the new and old concrete interface of the double-block ballastless track bed in the water environment are weakened to a certain extent, and the influence on the long-side contact surface is the most significant. The maximum principal tensile strain of the long-side contact surface has increased by 31.6%, and the shear fatigue life has been shortened by 30.4%, which appear in the upper-middle position of the surface, where cracks will initiate earlier.