摘要
通过单向冻结试验研究盐分在土体冻结过程中对水分重分布与变形的影响,并结合模型试验分析冻融、蒸发、辐射和降水过程中的水盐迁移规律。研究表明:盐分的存在会减弱土体在冻结过程中的水分迁移,进而抑制土体的冻胀变形。Na Cl盐渍土在冻结过程中只有冰晶产生,土体只发生冻胀变形。而2 4Na SO对温度极其敏感,降温过程中会产生冰晶体和盐晶体,土体发生冻胀和盐胀两种变形。硫酸钠的结晶还会降低土体导水系数,进而减弱土体的水分迁移。在高含盐量的2 4Na SO盐渍土(3.6%)冻结过程中,土体的分凝冻胀现象消失,只有冻结初期的原位盐胀和冻胀。模型试验表明2 4Na SO含量为2%的盐渍土冻融过程中,水盐迁移同样微弱。蒸发条件使得盐分向表面集聚,降水条件使得表层盐分向下迁移。干湿循环是土体发生盐胀破坏的主要原因,其远比冻结过程中的盐分迁移来的剧烈。盐胀发生在土体表面,而冻胀破坏主要在冻结锋面。基于以上试验,探讨了盐渍土在冻结过程中的水盐迁移过程以及盐胀和冻胀的成因。
In order to investigate the effect of salt on water and salt redistribution in freezing process, unidirectional freezing tests of soils with different salt contents were conducted. Moreover, model tests with four different boundary conditions（freeze-thaw cycle,evaporation, radiation, and precipitation） were used to investigate the transfer mechanism of salt and water in saline frozen soil. The results indicated as follows：due to the existence of salt,moisture migration will be weaken in the soil during freezing,so that the frost heave was mitigated. As no salt crystallizes in the freezing process,only frost heave exists in Na Cl soil. However,Na2 SO4 is sensitive to temperature,both salt and ice may crystallize during cooling,resulting in frost heave and salt expansion in sodium sulfate soil. Besides,the permeability of soil was decreased by Na2 SO4 crystals,thus the water movement was reduced. In Na2 SO4 soil with high salt contents（e.g. 3.6%）,in-situ salt expansion and frost heave occur at the initial freezing process,and segregation heave is negligible. For the Na2 SO4 soil with salt content 2%,the water and salt migration are also negligible in freezing-thawing process. Salt effloresces in the evaporation process,and surface soil salinity moves downward with water infiltration. Dry-wet cycle is the main cause of salt expansion,which has a stronger effect on salt movement than freezing process. Salt expansion exists at the soil surface,while frost heave is observed at freezing fringe. Finally,the water and salt transfer mechanism have been investigated,including the cause of salt expansion and frost heave.
作者
肖泽岸
赖远明
XIAO Zean;LAI Yuanming(State Key Laboratory of Frozen Soil Engineering, Northwest lnstitute of Eco-environment and Resources, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China;University of Chinese Academy of Sciences, Beijing 100049, China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2018年第A01期3738-3746,共9页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金重点资助项目(41230630)
中国科学院西部行动计划项目(KZCX2–XB3–19)
国家重点基础研究发展计划(973)项目(2012CB026102)~~
关键词
土力学
盐渍化冻土
水盐迁移
冻融
干湿循环
soil mechanics
saline frozen soil
water and salt transfer
freeze-thaw
dry-wet cycles
