道砟级配的分形方法及对道床剪切性能影响

Study of Fractal Method and Influence of Ballast Gradation on Ballast Bed Shear Behavior

碎石道砟级配对道床力学性能有明显影响,传统级配曲线区间难以精确量化道砟集料的级配分布特征及力学特性。基于分形理论,提出同时适用于新建和劣化后铁路散体道床的道砟级配分维度量化方法。为分析不同道砟级配对道床力学性能的影响原理,采用三维视觉重建技术建立精细化道砟颗粒单元及直剪数值模型,基于验证后的模型,研究分维度量化方法中两项关键级配控制参数对道床剪切力学性能的影响规律。结果表明,道砟级配分维度及道砟细碎颗粒含量与道砟抗剪强度有较强的负相关性,应在道床的养护维修中关注道砟的细碎颗粒含量。道砟级配分维度能同时反映道床的级配组成特征以及剪切力学性能,建议在规范中考虑该参数。

Ballast gradation has a significant impact on the mechanical property of ballast bed.However,the traditional form of ballast gradation curve is difficult to quantify accurately the characteristics and the mechanical property of the ballast bed.Based on the fractal theory,a fractal dimension quantization method which can be applicable to both newly-built and deteriorated railway ballast bed was proposed.In order to analyze the influence of different gradation on the mechanical property of ballast bed,a three-dimensional visual reconstruction method was adopted to set up the refined ballast discrete element and direct shear numerical model.Based on the validated numerical models,the influence of two key ballast gradation control parameters of fractal dimension quantization method on shear mechanical properties of the ballast bed was lucubrated.The results showed that both the ballast gradation fractal dimension and ratio of fine particles of the ballast bed had strong negative correlation to the shearing properties of the ballast bed.The ratio of fine particle should be closely watched during the maintenance of the ballast bed.The fractal dimension gradation quantization method can reflect both the gradation structural features and shear mechanical properties of the ballast bed.Therefore,this parameter is advised to be taken into account in relative standards.