摘要
大空隙级配碎石填料因其较好的渗透性能广泛应用于透(排)水性基床,然而级配对细观三维空隙特征的影响尚不明确。针对此不足,对3种代表性级配的透水性基床填料试样开展室内新型平板振动压实试验,并对压实后的试样进行高精度工业XCT扫描,重构其三维模型并获取其内部空隙,计算面空隙率、等效体积和三维形态等空隙结构特征指标,分析不同级配(颗粒堆积结构)对其三维形态及分布规律的影响。研究结果表明,不同级配的试样其内部面空隙率沿高度方向总体呈对称分布,即两端大中部小,骨架密实型颗粒堆积结构试样其面空隙率处于最低水平且沿高度方向的差异性最小,骨架空隙型颗粒堆积结构试样其面空隙率最大且不均匀性也最大;随着颗粒堆积结构从悬浮密实型过渡至骨架密实型再至骨架空隙型,试样内部空隙总数量大幅减小,孤立微空隙和小空隙数量减小,连通性较好的中空隙与大空隙增多;空隙形态逐渐演化为不规则型和长条型,并从较为圆润丰满型过渡至边缘残缺型,具有更好的连通性,可提供水气运移的通道。优化颗粒堆积结构有利于形成连通空隙并提供渗流通道,进而提升基床填料的水−力特性。研究结果可为透水性级配碎石基床填料的优化设计提供理论依据和技术参考。
Unbound aggregate materials featuring large pores are increasingly used to construct permeable bases due to their desired drainage performance.However,the influence of particle packing structure for meso-scale three-dimentional pore characteristics of such materials remain unexplored.To address such deficiency,the original vibratory plate compaction tests were conducted on laboratory specimens of unbound permeable aggregate base(UPAB)materials with three different representative gradations(or particle packing structures).The compacted specimens were subjected to X-ray computed tomography(XCT)scanning for reconstructing their three-dimensional(3D)digital models and then extracting their internal pores.The parameters quantifying internal pore structure characteristics were computed accordingly including surface porosity,equivalent pore volume,and pore shape indices,while their three-dimentional morphology and distributions among different gradations were comparatively analyzed.The results are drawn.The internal surface porosity values of different specimens are generally symmetrically distributed along the height direction with those at the two ends being large and those in the middle being relatively small.The surface porosity values of skeleton dense specimens are at the lowest level and have the least distributed difference,but that of skeleton gap specimens is at the largest level and has the greater distributed difference along the height direction.As the particle packing structure of UPAB specimens gradually transitioned from floating dense type to skeleton dense type and further to skeleton gap type,the total number of pores inside the specimens greatly reduced.The number of isolated microv-and small-sized pores decreased,but the number of medium-and large-sized pores with better connectivity increased.The pores gradually evolved into irregular and elongated ones and transitioned from rounded and plump ones to those with broken boundaries.They have better connectivity and can provide channels for water and g
作者
于群丁
王萌
肖源杰
华文俊
李文奇
王小明
YU Qunding;WANG Meng;XIAO Yuanjie;HUA Wenjun;LI Wenqi;WANG Xiaoming(Urban Rail and Underground Engineering Design and Research Institute,China Railway Siyuan Survey and Design Group Co.,Ltd.,Wuhan 430063,China;School of Civil Engineering,Central South University,Changsha 410075,China;MOE Key Laboratory of Engineering Structures of Heavy Haul Railway(Central South University),Changsha 410075,China)
出处
《铁道科学与工程学报》
EI
CAS
CSCD
北大核心
2024年第1期158-170,共13页
Journal of Railway Science and Engineering
基金
国家自然科学基金资助项目(52178443,U1934209,51878673)
国家重点研发计划(2019YFC1904704)
中国铁道科学研究院科技研究开发计划重大课题(2020YJ022,2019YJ026)
重载铁路工程结构教育部重点实验室(中南大学)开放课题(2021JZZ01,2021JZZ02)
中南大学研究生自主探索创新项目(2021zzts0788,2021zzts0227,2021zzts0223)。
关键词
透水性基床
级配
振动压实
XCT扫描
三维重构
细观空隙
permeable base
gradation
vibratory compaction
X-ray CT scanning
3D reconstruction
meso-scale pores
