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Seasonal Frozen Soil Frozen-thaw Process And The Analysis Of Impact Factors In The North Slope Of TianShan Mountain

Posted on:2014-02-02Degree:MasterType:Thesis
Country:ChinaCandidate:M HuFull Text:PDF
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Xinjiang mainly rely on the spring snow melting flood for recharge, snow melts astemperature rapid up, which bring plenty of water and also cause flood at the same time.With the development of economy, the environment of Xinjiang has suffered differentdegrees of damage, and in most parts of Xinjiang is still lack of water. Its ecologicalenvironment is fragile. How to accurately forecast the spring snowmelt flood runoff isvery urgent. However, the influencing factors of snowmelt flood is very complex, andthe seasonal frozen soil freezing and thawing process is the key factor of snowmeltrunoff. Therefore, study of Xinjiang seasonal freezing and thawing rule of thepermafrost is very urgent.This paper, through field observation in the field experiment of the study area andindoor simulation, studied the seasonal frozen-thaw process of permafrost andseasonally frozen soil temperature, unfrozen water content, soil conductivity and theinfluence factors such as snow, as well as the relationship between the factors. Resultsshow that:(1) the freezing period lasted longer than three months in the study area, themaximum depth of freeze is about40cm; the melting period lasted a shorter time thanthe freezing period is about lasted10days, depth of two-way thawing is about30cm, inthe2013Mar3.(2) During the period of the frozen-thaw process, the changes of soil temperaturedecreases exponentially with the increasing of soil depth, the relationship between thetwo (R2=0.8166). The temperature of shallow soil(0-40cm)is effected of solarradiation change and more intense, The temperature of deep soil(40-70㎝)is mainlyaffected by the of geothermal and changed little. The diurnal variation of the soiltemperature decreases with increasing depth, and showed a single peak-valleyfluctuations. (3) Unfrozen water content did not change significantly in the entire freezingprocess, the melting process is more obvious, the shallow between0cm to25cm soilmoisture is high value area. Soil moisture content of the soil between30cm and40cmis low-value area. When the unfrozen water content of between0.176to0.256soilbegins to melt and the sudden increase in water content. Unfrozen water content withinthe soil freezing depth during the freeze period has decreased, and at a later stageremains unchanged. During the snow ablation it increased suddenly and with increasingdepth there are lag effect.(4) Comparative experiments according to the presence or absence of snow cover,with snow cover the shallow soil temperature effect on temperature response because ofthe snow cover and delay from shallow to deep, from0to30cm soil layer, about every10cm delay1day. Delayed effect in the30-40cm soil layer, the two layers of the soiltemperature has little delay phenomenon;5cm soil temperature, temperature difference,the smaller the farther deep, to a certain depth, temperature differences can be reducedto zero.(5)In the process of frozen soil on the surface of frozen water content whenaround less than0.17in the soil electrical conductivity is about0. In the meltingprocess with the sudden increase of the unfrozen soil water content reaches itsmaximum value, which reached the highest value at the fastest rate of melting. Theexistence of deep frozen soil with no freeze conductivity changed little,but the soilelectrical conductivity were greater than the conductivity of the frozen layer,to themelting of the salt transport with the peak at50cm.
Keywords/Search Tags:Seasonal frozen soil, Freezing and thawing process, Impact factor, JunTang Hu River basin
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