Research On Movement Of Water And Salt In Freezing And Thawing Process Based On Test And Model

Western area of Jilin Province is rich in natural resources and developed inagriculture and animal husbandry, but in recent years, due to anthropogenic andnatural factors, the ecological and environmental problems increased seriously, soilsalinization is one of them. In order to effectively control the expanding trend, thelocal government has begun a new round of land consolidation, which using Da’anirrigation and other water conservancy projects to cite the water of Songhua River andNen River and reclaim the idle saline-alkali land. However, the infiltration of canalwater in irrigation region will cause the rise of the groundwater level, salt in thebottom of soil can easily migrate to the surface under the influence of regional climatecharacteristics (such as long freeze-thaw period, strong evaporation) and lead to soilsalinization. Therefore, this study chose Da’an city as study area, used a combinedmethod of field monitoring and laboratory test to research the salt distribution of soilprofile and the movement of salt and water under the influence of freeze-thaw actionagainst three types of soil in this area.Combined high-density Electrical Resistivity Tomography and the Geostatisticsmodule of ARCGIS to monitor and calculate salt content in the soil profile ofsaline-alkali soil, and analyzed the distribution characteristics of soil salinity: Salt inthe saline-alkali soil mainly distributed in the0-50cm depth of surface, the saltcontent decreased with the increasing of the depth, and the rate of the reduction alsobecame greater.Designed the laboratory test and analyzed the migration law of water and salt infreeze-thaw process, the results showed that:(1) Freeze-thaw action led to an increaseof water and salt content in the surface soil, correlation coefficient of the movement ofwater and salt can reach up to more than0.9, and they showed similar migration law in the freeze-thaw process.(2) Water and salt in paddy field soil, dry field soil andsaline-alkali soil showed differencet migration law due to the differences of physicaland chemical properties of the soil, salinity of saline-alkali soil in the surface willkeeping increase and the paddy field soil had a high risk of salinization under theinfluence of freeze-thaw action.Used Harlan model to simulate the coupling of water and heat ofone-dimensional soil column in freezing process, the results showed: With theincreasing of freezing time, temperature of the soil column continued to decrease andshowed approximate linear distribution after reached stabilized, freezing frontalsurface gradually moved to the warm side and stabilized eventually, the lower thetemperature of cold side, the deeper the freezing depth of the soil column, and watercontent near the freezing frontal surface kept increasing.