缩尺效应对铁路道砟力学特性影响的试验研究

Experimental study on influences of scale effect on mechanical properties of railway ballast

为了研究颗粒级配、缩尺效应对道砟强度及变形特性的影响,采用石英岩标准铁路道砟开展了一系列基于1/4缩尺及全尺寸道砟的三轴剪切试验。试验结果表明:缩尺道砟的峰值强度均较全尺寸道砟的峰值强度低,缩尺对窄级配道砟的峰值强度影响甚小,而使宽级配道砟的峰值强度降低明显,缩尺效应造成的峰值强度降幅最高达10%;道砟的强度指标c,?值受颗粒级配影响较大,而缩尺效应对其影响并不显著。全尺寸与缩尺道砟的体积应变特性差异较小,缩尺道砟的变形模量小于全尺寸道砟,颗粒级配对道砟变形模量的影响不大;在工程设计中采用缩尺道砟的强度和变形参数将有利于安全。

For the purpose of studying the effects of particle size distribution(PSD) and scale effect on strength and deformation characteristics of the ballast, a series of triaxial shear tests based on 1/4 scaled ballast as well as full ballast are carried out using standard ballast of quartzite. In terms of the peak strength, the experimental results show that the peak strength of the scaled ballast is lower than that of the full ballast. Meanwhile, little effect on the peak strength caused by the scale effect can be observed from ballast with narrow gradation, whereas a significant decrease up to 10% of the peak strength can be found resulting from the scale effect from ballast with broad gradation. The strength indices of ballast, cohesion c and internal friction angle ?, are greatly affected by the PSD. However, the scale effect has little influences on the strength index. The difference in volumetric strain of the full and scaled ballasts is small as well as that in deformation modulus between broad and narrow gradations. The deformation modulus of scaled ballast is smaller than that of full ballast. The strength and deformation parameters of the scaled ballast can be used for engineering design, which are beneficial to engineering safety.