单向冻结条件下非饱和土水分迁移规律研究  

Study on water migration behavior of unsaturated soil under unidirectional freezing condition

作　　者：张建勋[1] 毛雪松[1] 刘飞飞[1,2] 吴谦 ZHANG Jianxun;MAO Xuesong;LIU Feifei;WU Qian(School of Highway,Chang’an University,Xi’an 710064,China;College of Civil Engineering and Architecture,Henan University of Technology,Zhengzhou 450001,China)

机构地区：[1]长安大学公路学院,陕西西安710064 [2]河南工业大学土木建筑学院,河南郑州450001

出　　处：《冰川冻土》2023年第3期1080-1091,共12页Journal of Glaciology and Geocryology

基　　金：国家自然科学基金项目(51878064,51378072);中央高校基本科研业务费专项资金项目(300102218408,300102219108)资助。

摘　　要：为了揭示路基冻结过程中地下水和土性对水分迁移规律的影响,针对开放体系和封闭体系的粉质黏土和砂土进行了单向冻结条件下的水分迁移试验。通过土柱上层位置设置碎石层,阻断液态水迁移路径,监测冻结过程中土柱的水热变化,结合土柱冻结深度、冻结速率曲线、含水率分布曲线和补水时程曲线,分析仅水汽补给时对土柱顶部水分聚集和冻结特征的影响。试验结果发现,无论是封闭体系还是开放体系,粉质黏土和砂土土柱都会在冻结区中形成两处水分聚集区:第一水分聚集区为控温板底部,以霜的形式聚集,主要是由土柱顶部土体的水汽迁移并凝华相变形成;第二水分聚集区为冻结区中液态水和气态水共同迁移形成,随着冻结锋面的向下推移,形成不连通孔隙的界面,液态水向0℃冰锋线迁移聚集并相变成冰,水汽迁移路径受阻而凝华成冰,致使该处含水率显著增加。相较于封闭体系,开放体系使两处水分聚集区产生更大的水分增量。相比于粉质黏土,砂土介质孔隙较大,在试验时间内水汽补给对水分聚集区的影响更明显,但由于砂土持水能力减弱,水汽补给速率随时间逐渐减小。In order to reveal the influence of groundwater and soil properties on the water migration pattern dur⁃ing the freezing process of subgrade,water migration tests of unidirectional freezing conditions were conducted for open systems and closed systems of silty clay and sandy soil.By setting a gravel layer in the soil column,blocking the liquid water migration path,monitoring the hydrothermal changes of the soil column during the freezing process,and combining the frozen depth,freezing rate curve,water content distribution curve,and wa⁃ter replenishment time-varying curve of the soil column,the effect on the water accumulation and freezing char⁃acteristics of the top of the soil column when only water vapor was replenished was analyzed.The experimental study found that the freezing zone can be divided into a fast freezing zone,a transition freezing zone,and a sta⁃ble freezing zone.The change in unfrozen water content was closely related to the change in the temperature field.At the beginning of the test,the temperature in the unfrozen zone was gradually decreasing,and the unfro⁃zen water migrated to the cold end under the action of the water driving force,and the decrease in unfrozen water content meant that the water migrated into the frozen zone.When the freezing front gradually moved down,the unfrozen zone in the upper soil layer transformed into the frozen zone,and the unfrozen water underwent a freez⁃ing phase change and decreased rapidly.Subsequently,the unfrozen water content showed a slow decreasing trend with the negative temperature.On the other hand,there was a difference in the change of unfrozen water content below the gravel layer between the silty clay and sandy soil columns.Due to silty clay having smaller pores compared with sandy soils,a small accumulation of unfrozen water occurred in the soils below the gravel layer.At the same time,unfrozen water also migrated downward by the gravitational potential.The sandy soil has a weaker water-holding capacity compared to the silty clay and wa

关 键 词：单向冻结 非饱和土 水汽迁移 开放体系 封闭体系 未冻水 

分 类 号：TU411[建筑科学—岩土工程] TU445[建筑科学—土工工程]