针片状指数对道砟直剪力学特性的影响

为研究针片状道砟在破碎情况下对道砟散体直剪力学特性的影响,通过进行不同工况下道砟直剪试验,从道砟散体剪切强度、变形及破碎特性对试验结果进行分析.研究结果表明:(1)随着针片状指数增加,道砟散体直剪力学性能下降,包括抗剪强度和内摩擦角(100 kPa下当针状指数由0分别提高到20%、40%时,抗剪强度分别降低10.9%、16.8%;片状指数由0分别提高到20%、40%时,抗剪强度分别降低14.7%、22.3%;针、片状道砟总值由0分别提高到20%、40%时,抗剪强度分别降低12.4%、18.9%).(2)随着针片状道砟含量增加,试样剪缩和剪胀量均降低.(3)针片状道砟在直剪试验过程中易于发生破碎,且破碎类型多为整体断裂并伴随尖角破碎折断,显著影响有砟道床维修周期.

Effect of Flakiness-Elongation Index on Shear Behavior of Railway Ballast

In order to investigate the influences of flat and (or) elongated ballasts on direct shear mechanical properties considering the breakage effect, the direct shear tests with different test conditions were conducted to study the effect of the flat and/or elongated ballast content with the analysis of testing results from the ballast shear strength, deformation and breakage. The results show that: (1) With the increase of the flakiness and elongation index, the shear behavior of the ballast decreases, both the shear strength and internal friction angle (at 100 kPa, the shear strength respectively decreases by 10.9%, 16.8% when the elongation index increases from 0 to 20%, 40%; the shear strength respectively decreases by 14.7%, 22.3% when the flakiness index increases from 0 to 20%, 40%; the shear strength respectively decreases by 12.4%, 18.9% when the flakiness-elongation index increases from 0 to 20%, 40%). (2) The shear dilatation and shrinkage of samples decrease with the flat and/or elongated ballast content increasing. (3) The flat and elongated ballast particles are prone to break up during the direct shear test, and most of them are fractured with the sharp corner breakage, which significantly affects the ballast bed maintenance cycle.