摘要
土的细观结构是其宏观力学性质变化的本质,而黄土是一种特殊的结构性土,细观结构研究对揭示黄土地质灾害机理尤为重要。为了探讨黄土在不同外荷作用下的细观结构演化规律,本文采用压汞技术(MIP)及扫描电镜(SEM)等细观结构研究手段,对黄土在不同压实状态,无侧限增减湿,常含水率压缩以及常应力增湿作用下的细观结构进行全面试验研究,并从有效应力角度对细观结构演化进行探讨,进一步总结黄土填方地基的细观沉降机理。结果表明:松散黄土在压实过程中会形成团聚体间大孔隙,团聚体内小孔隙以及黏粒间微孔隙等三层次孔隙结构;初始干密度,饱和度主要影响大、小孔隙结构,而对微孔隙结构无影响;无侧限增湿对孔隙密度分布形态影响有限,但能弱化颗粒间的胶结,而常应力下增湿会引起大孔隙塌陷,产生湿陷变形,孔隙结构趋于均匀稳定;无侧限干燥会同时作用于3个层次孔隙结构,而压缩仅作用于大孔隙结构。整体来讲,细观结构的调整是土有效应力变化的结果,但净应力会先作用于大孔隙,而吸力变化会对3种孔隙结构同时产生影响。细观结构研究表明,压实度在一定程度上决定黄土大孔隙结构,控制施工压实度可以有效控制黄土填方地基施工期及工后期沉降。
Microstructure plays a key role in soil behavior.Loess is a structural soil,and the study of microstructure is crucial for understanding the trigger mechanism of loess geologic hazards.In order to investigate the microstructure evolution of loess under different actions,a series of experiments including compression,wetting,and unconfined drying were conducted on compacted loess.Microstructure was studied using Mercury Intrusion Porosimetry(MIP)tests and Scanning Electron Microscope(SEM)analysis.The evolution of microstructure was discussed in terms of the effective stress of the soil.The settlement mechanism of loess-filled embankments was further revealed through the study of soil microstructure.The experimental results show that during compaction in loess,three different pore structures are formed:inter-aggregate pores,intra-aggregate pores,and micropores.An increase in as-compact dry density lead to a decrease in inter-aggregate pores,while an increase in as-compact saturation degree improved the formation of inter-aggregate pores.The as-compact state had no effect on micropore distribution.Unconfined wetting had a limited effect on pore size distribution but weakened bonding between particles.Due to the reduction of inter-aggregate pores,loess exhibited obvious collapse upon soaking under constant stress.Unconfined drying caused the shrinkage of aggregates,which further induced an increase in inter-aggregate pores and micropores,and a reduction in intra-aggregate pores.The volume change of loess during 1-D compression was caused by a decrease in inter-aggregate pore volume upon compression.In summary,the re-arrangement of microstructure is induced by changes in effective stress in unsaturated soil.However,the three levels of pore structures show different responses to variations in net stress and suction.Net stress has a greater influence on inter-aggregate pores,while changes in suction affect all three pore structures.The results of the microstructure study indicate that the quantity of inter-aggregate pores depends on the compaction degree in the field.Controlling the compaction degree can help reduce the settlement of compacted loess fill during and after construction.
作者
葛苗苗
何璇
谷川
李宁
刘乃飞
GE Miaomiao;HE Xuan;GU Chuan;LI Ning;LIU Naifei(Institute of Geotechnical Engineering,Wenzhou University,Wenzhou 325035,China;Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering,Xi'an 710055,China;Institute of Geotechnical Engineering,Xi'an University of Technology,Xi'an 710048,China;College of Civil Engineering,Xi'an University of Architecture and Technology,Xi'an 710055,China)
出处
《工程地质学报》
CSCD
北大核心
2024年第2期397-409,共13页
Journal of Engineering Geology
基金
国家自然科学基金项目(资助号:52108339)
陕西省岩土与地下空间工程重点实验室开放基金项目(资助号:YT202006)
温州市基础性公益科研项目(资助号:2021S0064)。
关键词
压实黄土
增减湿
细观结构
湿陷
填方沉降
Compacted loess
Wetting/drying
Microstructure
Wetting collapse
Settlement of compacted fil
