Three-Dimensional Discrete Element Simulation of Ballast Direct Shear Testing in Vibration Field
Three-Dimensional Discrete Element Simulation of Ballast Direct Shear Testing in Vibration Field
复制标题
振动场道碴直剪试验三维离散元模拟
DOI：
10.1007/s10706-020-01482-4
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发表时间：
2020-08
影响因子：
1.7
通讯作者：
Yanhai Wang
中科院分区：
文献类型：
--
作者：
Junhua Xiao;Xiao Zhang;De Zhang;Xueyu Geng;Yanhai Wang
为揭示动载扰动下道碴颗粒的力学特性，建立了水平振动场中道碴直剪试验的三维离散元模型。基于三维扫描技术，采用Voronoi曲面细分技术，在数值模型中重建道碴颗粒的形态特征。通过对道碴静态直接试验结果的校正，得到了道碴颗粒的细观力学参数。在此基础上，研究了碎石土样在动态条件下的抗剪强度和体积变化。数值结果表明，振动场中道碴的抗剪强度小于静剪条件下的抗剪强度。振动幅值是影响道碴动剪切强度的主要因素，当振动幅值从0.1 mm增加到0.48 mm时，道碴试样的峰值剪应力从185 kPa减小到102 kPa;而当振动频率从10 Hz增加到60 Hz时，道碴动剪切强度变化不明显。通过对碎石剪切前后体积变化的分析，确定了碎石的剪胀特性。在静态和低频动态剪切条件下，碎石试样的体积均单调增加;而当振动频率超过某一临界值时，碎石试样的体积在剪切过程中先增加后减小。此外，增加振幅可以有效地降低该临界频率。对于剪切方向与振动方向不一致的动态条件，当剪切方向与振动方向的夹角从90°（相互垂直）变为0°（同向）时，夹角越小，剪切强度下降越多。
To reveal the mechanical properties of ballast particles under the disturbance of dynamic loading, a 3D DEM model for ballast direct shear test was established in a horizontal vibration field. Based on 3D scanning technology, the morphological characteristics of ballast particles were rebuilt in the numerical model by Voronoi tessellation. By calibrating with experimental results of ballast static direct experiments, meso-mechanical parameters for ballast particles were also obtained. On this basis, ballast sample’s shear strength and volume changing under dynamic condition were studied. Numerical results showed that the ballast shear strength in vibration field were smaller than that under static shear condition. Vibration amplitude was the main factor affecting the dynamic shear strength of ballast, as vibration amplitude increased from 0.1 to 0.48 mm, the peak shear stress of the ballast sample decreased from 185 to 102 kPa; while as the vibration frequency increased from 10 to 60 Hz, the dynamic shear strength of ballast didn’t change obviously. Dilatancy feature of ballast was confirmed by volume change before and after shearing process. For the static and low frequency dynamic shear condition, the volume of the ballast sample increased monotonously; while as the vibration frequency exceeded a critical value, the volume of the ballast sample increased first and then decreased during the shearing process. Moreover, increasing the amplitude could effectively reduce this critical frequency. For the dynamic condition that the shear direction was not coincident with the vibration direction, as the angle between these two directions changed from 90° (perpendicular to each other) to 0° (same direction), the smaller the angle was, the more the shear strength decreased.
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