Study On Soil Water-Heat-Salt Transfer During Freezing-Thawing And Its Simulation By Numerical Model Over Meadow Land Of Horqin

Combined with soil freezing and thawing period at present stage hydrothermal salt migration rule research present situation, on the basis of existing research, this paper USES the continuous dynamic point of view and fixed point experiment method, the study of horqin sandy meadow soil freezing and thawing period, heat, salt and water movement law, based on multiple factor correlation analysis and SHAW model simulation, analyzes the seasonal freezing and thawing period heat meadow soil water salt dynamic change rule and the main factors affecting the soil freezing and thawing process.This paper made the following main research results:(1) Analysis of meadow to geothermal process, along with the change of the temperature detection khorchin sand between meadow soil temperature change and temperature change trend, and the surface temperature change dramatically.Temperature, temperature lags behind the lag time due to temperature changes, at the same time freeze time lag behind the temperature change is greater than soil temperature changes induces soil lag time, can prove that the soil freezing rate is less than the ablation rate, prior to the corresponding changes in underground and surface;According to the temperature, the seasonal freezing and melting process can be divided into initial stage freeze, stable melting freeze and thaw three stages;Down from the surface soil freezing process, the maximum frozen depth can be up to 100 cm;Soil by underground to warm the soil heat flux and surface temperature melting, as well as the influence from the bottom to the surface and two-way melt from the surface to the bottom.(2) Meadow to underground water level is higher, the whole period, the meadow soil profile moisture content was high, the water content with the range of freezing and thawing process is not obvious, only the initial freeze surface soil and stable freeze by frozen subsoil role change is bigger, other times moisture migration are not very active.Due to soil types, different factors, such as the original water content and soil depth of each layer is not frozen water content while it is possible to achieve a relatively stable state, but the content of each layer is not the same.In addition, the same as the ground temperature change trend.the frozen water content with the increase of soil depth. there is obvious hysteresis.(3) The meadow to salt to the surface accumulation during soil freezing, and reached the maximum in February, after melt and rain embellish effect began to decline.Combined with frost and ground temperature monitoring data can be accurately determine the depth of frozen soil, meadow soil, because salt in freeze soil freezing point are negatively related with salt, so the frost is affected by a certain, the inter annual variation is not the same.(4) The results of correlation analysis showed that correlation between temperature and soil temperature is higher.10 correlation of 0.872 cm, surface layer correlation can reduce step by step down.Smaller correlation of air humidity and soil temperature, soil temperature and negatively correlated with water content, gathered to freeze the water like a frozen layer, soil salinity and negatively correlated with soil temperature.Shallow soil moisture content and salinity completely related, visible with salt water is the main way of salt movement.(5)Using the SHAW model in freezing and thawing period of horqin sandy meadow soil, heat, salt and water movement in the process of simulation, and compared with the actual results, found that the model can simulate the natural freezing and thawing period under the condition of meadow soil hydrothermal salt migration process.At the same time adopt Surferll software rendering 3 d stereogram can intuitive presentation layer and time dimension in the soil temperature, moisture content, the changing process of salt.