Exploring the mechanical behavior and microstructure of compacted loess subjected to dry-wet cycles and chemical contamination  

作　　者：Yongpeng Nie Wankui Ni Xiangfei Lü Wenxin Tuo 

机构地区：[1]College of Geological Engineering and Geomatics,Chang'an University,Xi'an,710054,China [2]Department of Civil Engineering,Nagoya Institute of Technology,Nagoya,466-8555,Japan [3]School of Water and Environment,Chang'an University,Xi'an,710054,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2024年第9期3673-3695,共23页岩石力学与岩土工程学报（英文版）

基　　金：supported by the Second Tibet Plateau Scientific Expedition and Research Program(Grant No.2019QZKK0905);the Key Program of the National Natural Science Foundation of China(Grant No.41931285);the Key Research and Development Program of Shaanxi Province(Grant No.2019ZDLSF05-07).

摘　　要：Due to climatic factors and rapid urbanization,the soil in the Loess Plateau,China,experiences the coupled effects of dry-wet cycles and chemical contamination.Understanding the mechanical behavior and corresponding microstructural evolution of contaminated loess subjected to dry-wet cycles is essential to elucidate the soil degradation mechanism.Therefore,direct shear and consolidation tests were performed to investigate the variations in mechanical properties of compacted loess contaminated with acetic acid,sodium hydroxide,and sodium sulfate during dry-wet cycles.The mechanical response mechanisms were investigated using zeta potential,mineral chemical composition,and scanning electron microscopy(SEM)tests.The results indicate that the mechanical deterioration of sodium hydroxidecontaminated loess during dry-wet cycles decreases with increasing contaminant concentration,which is mainly attributed to the thickening of the electrical double layer(EDL)by Nat and the precipitation of calcite,as well as the formation of colloidal flocs induced by OH,thus inhibiting the development of large pores during the dry-wet process.In contrast,the attenuation of mechanical properties of both acetic acid-and sodium sulfate-contaminated loess becomes more severe with increasing contaminant concentration,with the latter being more particularly significant.This is primarily due to the reduction of the EDL thickness and the erosion of cement in the acidic environment,which facilitates the connectivity of pores during dry-wet cycles.Furthermore,the salt expansion generated by the drying process of saline loess further intensifies the structural disturbance.Consequently,the mechanical performance of compacted loess is sensitive to both pollutant type and concentration,exhibiting different response patterns in the dry-wet cycling condition.

关 键 词：Contaminated loess Dry-wet cycles COMPRESSIBILITY Shear strength Microstructural evolution 

分 类 号：TU43[建筑科学—岩土工程]