【作者】 敖国栋；

【导师】 赵成刚；

【作者基本信息】 北京交通大学 ， 岩土工程， 2011， 硕士

【摘要】 摘要：有砟轨道已经有180多年的发展历史,虽然无砟轨道轨道技术近年来发展迅速,但是有砟轨道仍是铁路最常见的,应用最广的形式。有砟轨道结构的优点是结构简单、造价低廉、维修方便。有砟轨道的变形和差异沉降对铁路运营安全和舒适度,以及铁路维护成本的影响很大,是有砟轨道研究的重要课题。本文采用非连续变形分析(DDA)的理论,对道砟的力学特性进行分析模拟。本文的道砟模型使用随机生成的凸五边形道砟颗粒,通过控制道砟颗粒的粒径和数量模拟实际道砟的级配。首先通过反演标定了对道砟模型中的参数,然后对道砟级配对道砟密实度的影响,道砟单轴、三轴条件下的变形响应进行了一系列的研究。道砟在单轴条件下的压缩、循环加载模拟结果表明：道砟的孔隙比对于其变形特性影响最大,未经过压实的松散道砟在加载阶段会表现为弹性和弹塑性两个阶段,而压实后的道砟基本上保持弹性的加卸载特性,卸载后的塑性残余应变很小。经过多次的循环加卸载后,每次的残余塑性应变会逐级减小。道砟在三轴条件下的压缩、剪切模拟结果表明：在三轴等向压缩中,轴向应变随应力提高而增加,但是应变值约为单轴压缩条件下的一半。三轴剪切过程可以分为两个阶段,首先都要经历一个剪缩的过程,这将导致孔隙的压密；接下来剪缩的趋势逐渐减小,特别是低围压条件下,然后会出现剪胀的现象。但随着围压增大,这种剪胀现象会逐渐减小直至完全消失。道砟级配分析结果表明：单一粒径的颗粒孔隙比较大,在大粒径中加入小粒径的颗粒可以减小孔隙比而提高密实度。对于两种粒径的混合颗粒,存在一个最优配比,使得道砟达到最小的孔隙比。更多还原

【Abstract】 ABSTRACT:The ballasted track has a history of 180 years. Although ballastless track technology has developed rapidly in recent years, ballasted track is still the most common and widely used form. The advantages of ballast track structure include simple structure, inexpensive cost, convenient maintenance. The deformation and differential settlement of ballast have a great effect on the safety and comfort, even on the railway maintenance costs, all of these make it to be an important reseach topic.In this paper, discontinuous deformation analysis(DDA) theory is used to simulate the mechanical properties of ballast. The ballast model is simulated by a randomly generated convex pentagon particles, and the real ballast gradation is got by controlling the ballast size and number. First calibrate the model parameters by inversion, then study the effect of gradation on the density and the response to the ballast uniaxial, triaxial deformation.The simulation results of ballast under the uniaxial compression and cyclic loading show that:the void ratio of ballast has the greatest impact on the deformation characteristics, the uncompacted ballast will be manifested in the elastic stage and elastic-plastic stage; although the compacted ballast will remain the elastic properties basically, the residual strain after unloading is small. After repeated cyclic loading, the residual plastic strain will decrease progressively.The simulation results of ballast under triaxial compression and shear simulation show that:In the triaxial isotropic compression, the axial stress increased with increasing strain, but the value is about half of the uniaxial compression. Triaxial shear process can be divided into two phases, the contraction is mainly due to pore compaction, following the trend of contraction decreases, especially under low confining pressure, the dilatancy will take place. As confining pressure increases,this effect is getting unclear until disappear.The ballast gradation analysis shows that:the void ratio of single size is relatively high, adding small size particle to the large particle can reduce the void ratio and increase density. For a mixture of two particle size, there is an optimal ratio, making the ballast to achieve the minimum void ratio.更多还原