Longitudinal resistance performance of granular ballast beds under cyclic symmetric displacement loading

Abstract

The longitudinal resistance performance of a granular ballast bed under cyclic symmetric displacement loading was studied based on a full-scale test model of ballast track structures. The change law of the longitudinal resistance characteristics of the ballast bed under variable displacement amplitudes was analyzed. The results show that: the resistance-displacement curves of a granular ballast bed are a set of closed hysteretic curves, indicating obvious energy consumption; a granular ballast bed softens gradually during the cyclic process with constant displacement amplitude, and the residual deformation rate increases nonlinearly with increasing cycle number; the peak value of the longitudinal resistance of lines decreases with increasing cycle number; the cyclic softening of a granular ballast bed is dependent on the displacement amplitude–the higher the displacement, the more severe the cyclic softening will become; after cyclic displacement loading is applied several times, the longitudinal resistance of the bed will degenerate obviously, and the higher the displacement amplitude, the higher the longitudinal resistance attenuation rate of the ballast bed will become.

中文概要

目 的

研究散粒体道床在纵向反复荷载下的阻力性能及变化规律是深入理解有砟轨道无缝线路动态服役性能和辨识无缝线路在循环荷载作用下的受力变形机理的基础。本文旨在利用室内足尺试验模型及专用加载系统, 分析散粒体道床受循环位移荷载时的纵向阻力性能, 探索不同位移加载幅值对有砟道床纵向阻力的影响。

创新点

1. 利用有砟轨道结构足尺试验模型及循环加载装置, 测试循环荷载下的道床纵向阻力-位移滞回曲线; 2. 根据循环加载试验曲线, 构建滞回模型, 刻划散粒体道床的纵向承载和传力性能。

方 法

1. 通过试验分析, 得到散粒体道床在周期性荷载作用下的力-位移曲线(图6、8 和10); 2. 基于试验数据, 分析散粒体道床在周期性荷载下的滞回准则, 得到不同位移幅值下滞回曲线的演化规律(图7、9 和11); 3. 通过图像识别技术, 对周期性荷载作用下道砟颗粒的运动规律进行分析, 从散粒体道床的细观作用机理分析宏观力学表现(图16~18)。

结 论

1. 散粒体道床在循环往复荷载下的纵向阻力-位移曲线为一条封闭的滞回曲线, 且存在明显的耗能现象; 2. 在位移幅值保持不变的循环过程中, 散粒体道床表现出一种循环软化行为; 3. 位移幅值不同, 道床纵向阻力的衰减率不同, 且位移越大, 退化效应越明显。