振动压实致粗粒土填料颗粒运移和空隙演化特征
Particle Motion and Migration and Pore-structure Evolution Characteristics of Unbound Embankment Fill Materials Subjected to Vibratory Loading
王萌 1于群丁 2肖源杰 3华文俊 1李文奇 1毛建锋 1李志勇4
作者信息
- 1. 中南大学土木工程学院,湖南长沙 410075
- 2. 中南大学土木工程学院,湖南长沙 410075;中铁第四勘察设计院集团有限公司城市轨道与地下工程设计研究院,湖北武汉 430063
- 3. 中南大学土木工程学院,湖南长沙 410075;重载铁路工程结构教育部重点实验室,湖南长沙 410075
- 4. 湖南省交通科学研究院有限公司,湖南长沙 410015
- 折叠
摘要
路基粗粒土填料的连续振动压实质量评价仍缺乏颗粒运移、骨架和空隙结构特征等细观指标,为此,针对振动压实最优激振参数组合下的粗粒土填料,基于高精度工业X射线计算机断层扫描(XCT)及三维重构技术,从细观尺度对比分析了基床填料内部颗粒运动、迁移和分布规律,量化分析了不同阶段填料内部三维空隙结构演化特征.研究结果表明:振动荷载作用下粗粒土填料颗粒在第1阶段以竖向运动为主,填料内部空隙减小并逐渐形成骨架;颗粒在第2阶段主要在水平面移动及竖直面内滚动,颗粒间的咬合嵌挤作用增强;当超过60％的颗粒其长轴倾角绝对值大于60°时,表明填料已基本接近或达到较优压实状态;相比其他粒径颗粒,4.75～9.5 mm和2.36～4.75 mm两个粒径范围内的颗粒处于粗细颗粒的分界,在振动荷载作用下更趋向于调整自身的位置,进而强化粗颗粒间的骨架效应;随着压实过程的推进,填料内部粗颗粒骨架结构逐渐形成且细颗粒不断填充骨架结构的空隙,面空隙率沿试样高度方向的不均匀性减小,空隙整体形状向规则型发展且空隙间的形态差异不断减小.研究结论可为粗粒土填料室内振动压实质量评价提供更全面的颗粒运动和空隙结构特征等微细观指标.
Abstract
Quality evaluations of the continuous vibratory compaction of unbound granular fill(UGF)embankment materials still lack particle-scale and microscopic indicators for quantifying particle-movement and migration,force-transferring skeleton,and pore-structure characteristics.To address this deficiency,the motion and migration characteristics of marked particles in a specimen with optimal gradation under an optimal combination of vibratory parameter conditions were tracked by X-ray computer topography(XCT)scanning during different stages of vibratory compaction.The evolution characteristics of the three-dimensional(3D)pore structures were quantitatively analyzed in the XCT scanning results using 3D reconstruction technologies.The results indicate that the marked particles mainly move vertically during the first stage of vibratory compaction,leading to the gradual formation of an aggregate skeleton and diminishing pores in the specimen.The particles move horizontally and roll vertically during the second stage of vibratory compaction,which enhances the interparticle contact and interlocking.When over sixty percent of the particles in the specimen have their longest axes oriented at an angle greater than 60° with respect to the horizontal plane,the specimen reaches optimal compaction.Compared with other sizes of particles,particles within 4.75-9.5 mm and 2.36-4.75 mm separate into coarse and fine fractions,respectively,and are more susceptible to movement when vibratory forces are applied;this strengthens the coarse-particle skeleton and fills the interparticle voids.The nonuniformity of the cross-sectional porosity along the specimen height decreases,and the overall morphology of the pores tends to become regular as the differences among the pores diminish.These findings can potentially supplement the more comprehensive indices of particle-scale motion and microscopic pore structure for evaluating the vibratory compaction quality of UGF materials in laboratory conditions.
关键词
路基工程/粗粒土填料/振动压实/X-ray/CT扫描/颗粒运动迁移/空隙结构Key words
subgrade engineering/unbound granular fill(UGF)material/vibratory compaction/X-ray CT scan/particle motion and migration/pore structure引用本文复制引用
基金项目
湖南省自然科学基金杰出青年基金项目(2024JJ2073)
国家自然科学基金项目(52178443)
国家自然科学基金项目(U1934209)
国家自然科学基金项目(51878673)
国家重点研发计划项目(2019YFC1904704)
出版年
2024
NETL
NSTL
万方数据