Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal
Experimental investigation of static and cyclic behaviour of scaled railway ballast and the effect of stress reversal
复制标题
铁路道碴的静态和循环行为及应力反转效应的实验研究
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
S. Aingaran
中科院分区：
文献类型：
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作者：
S. Aingaran
研究的目的是提高对道床力学行为的基本认识，并研究夯实对道床的影响。这些试验是在铁路道碴上进行的，以消除与测试大颗粒颗粒材料相关的困难。在结垢过程中考虑了级配、矿物学和形状。使用成像技术对定标压载和全尺寸压载进行了颗粒表征工作，以检查使用定标压载的有效性。对结果的详细分析被用来定量测量形状随颗粒大小的变化。结果表明，不同颗粒大小区间的颗粒形状存在明显差异。由于差异很小，它们不会使刻度镇流器的使用失效。作为实验室测试方案的一部分，进行了单调的循环实验。有比例的道碴表现出与较大颗粒材料大致相似的应力应变行为。当围压范围为15~200kPa时，摩擦角为40~50°，与文献中给出的全尺寸道床摩擦角范围一致。考察了列车装载过程中改变围压的影响。结果表明，随着围压的循环，土体的沉降量增大，刚度减小。在循环加载后的拉伸阶段，考察了夯实过程中的主应力反转效应。结果表明，在初始循环过程中，土体在伸展阶段后发生大量沉降，在荷载作用下，很快恢复到伸展前阶段。结果表明，夯击破坏了道床结构，造成了道床刚度的损失。在遵循特定的应力路径后，将试件在三轴单元内进行树脂稳定。可以通过CT检查来研究特定应力路径中结构的变化。
The aim of the research was to improve the fundamental understanding of mechanical behaviour of ballast and study the effect of tamping on ballast. The experiments were carried out on scaled railway ballast to eliminate the difficulties associated with testing large particle granular materials. Consideration was given to the gradation, mineralogy and shape during scaling. Particle characterisation work was carried out on scaled and full size ballast using imaging techniques to examine the validity of the use of scaled ballast. Detailed analysis of results is used to quantitatively measure the changes in shape with particle size. The results show measurable differences in particle shape between different particle size intervals. As the differences are small in magnitude, they do not invalidate the use of scaled ballast. Monotonic, cyclic experiments were carried out as part of a laboratory testing programme. Scaled ballast shows generally similar stress strain behaviour to larger granular materials. The friction angle of 40o to 50o for the confining pressure range of 15 kPa to 200 kPa falls within the range of friction angle obtained for full size ballast in the literature. The effect of changing confining pressure during train loading was examined. The results show that the settlement increases and the stiffness reduces when the confining pressure cycles. The effect of principal stress reversal during tamping was examined by an extension stage after the cyclic loading. It is shown that massive settlement occurs after the extension stage during initial cycles and settlement returns back to the pre-extension stage soon under loading. The results evidence the disruption of ballast structure and loss of stiffness due to tamping. Specimens were resin stabilised within the triaxial cell after specific stress paths had been followed. The changes in structure during a specific stress path can be studied by CT examination.