短时冻土区残积土边坡水热耦合机理的研究

发布时间：2018-01-27 13:26

本文关键词： 短时冻土残积土边坡水热场耦合二维差分　出处：《福州大学》2014年硕士论文　论文类型：学位论文

【摘要】：福建省闽北等地地处短时冻土区,区域内的短时冻土在冬季具有形成冻融周期短、冻融次数频繁、冻土层深度较浅、冰雪融化后边坡浅层含水率升高等特点。现场调查表明,短时冻土区残积土边坡浅层冻融垮塌频发,给当地公路的养护造成了较大的困难,但相关基础理论研究一直未得到重视。基于以上,本文采用文献与工程调研、室内试验、现场试验与理论分析相结合的技术手段,获得了福建典型残积土水热参数以及冻结特性,编制了短时冻土区残积土边坡水热耦合的计算程序,分析了短时冻土地区气候特点以及边坡土壤墒情特点,得出了闽北地区冻土边坡水热变化规律。研究的主要结论如下：(1)针对典型的两类残积土冻结试验表明,黄壤冻结温度范围为-1℃-2℃,红壤冻结温度范围为-6.5℃-7.5℃；并且含水率越高、含盐率越低,土壤冻结温度呈现上升趋势。(2)综合运用函数拟合及取均值确定初值条件,外边界条件主要考虑蒸发、太阳辐射、净辐射、对流换热及蒸发潜热,基于Harlan模型,通过抓MATLAB编程得到了适用于短时冻区残积土边坡水热耦合的计算程序。(3)试验段冻期集中在2013.12至2014.2间,期间最低气温可达-4.4℃；冻期内的天气以多云及阴天为主,辐射一般低于850W/m2,日辐射峰值最低为21W/m2；各月的低温天数分别为8d、10d、14d,冻期内冻融频繁,共存在18次冻融周期,其中16次一天冻融,1次两天冻融,1次六天冻融；闽北极低气温可达-7℃～-8℃,气温随纬度或海拔增大而降低；降温对边坡温度的影响深度为25cm左右；边坡土壤温度随时间变化呈现正余弦规律并滞后气温变化2-3h；土壤含水率日蒸发量的范围为0.001/d～0.003/d。(4)由模型计算结果可得：闽北地区边坡冻深范围为0-15cm,土坡发生5h以上冻融时,边坡表层容易形成稳定冰层；试验段内一天冻融下,土壤冻时可达5h,六天冻融下,土壤冻时可达32h；气温在土壤冻结温度以下的持续时间低于1.5h时,土壤不易冻结；空气湿度越高,蒸发量越小,边坡土层的冻深以及冻融持续时间越大。(5)土质因素对土壤冻结深度的影响因素敏感性排序为：含盐量初始含水率干密度土骨料比热；外边界因素对土壤冻结深度的影响因素敏感性排序为：日最低气温太阳辐射空气湿度。
[Abstract]:Fujian Province, located in short permafrost areas, permafrost area has formed short freeze-thaw cycle is short in winter, freezing and thawing permafrost in frequent shallow ice melts of the shallow layer of high moisture content. The field survey showed that short-time permafrost Residual Soil Slope Shallow freeze-thaw the collapse happened frequently, caused great difficulties to the local highway maintenance, but the related basic theory research has not been paid attention to. Based on the above, this article uses the literature and engineering investigation, laboratory test, field test and theoretical analysis method combining the obtained Fujian typical Residual Soil Hydrothermal parameters and freezing characteristics, short-term preparation of permafrost residual soil slope calculation program of water heat coupling, analysis of climate characteristics in permafrost regions and short slope soil moisture characteristics, the permafrost slope hydrothermal changes in North Fujian. The main research. The theory is as follows: (1) according to the two typical residual soil freezing experiment showed that soil freezing temperature range of -1 DEG -2 DEG, soil freezing temperature range of -6.5 -7.5 DEG C; and the higher water content, salt content is low, soil freezing temperature rise. (2) the comprehensive use of function the fitting and the average value is determined, the boundary conditions are considered evaporation, solar radiation, net radiation, heat convection and evaporation, based on the Harlan model, through grasping the MATLAB programming calculation program for short-term frozen area of residual soil slope water heat coupling. (3) the test section of frozen period in 2013.12 to 2014.2, the lowest temperature is -4.4 DEG C during the freezing period; the weather with cloudy and cloudy days, radiation is generally lower than 850W/m2, the lowest 21W/m2 emission peak; low temperature days of each month were 8D, 10d, 14d, frozen period of freezing and thawing frequently, there were 18 times of freeze-thaw cycle Among them, 16 times a day 1 times two days of freezing and thawing, freezing and thawing, 1 times six days in freezing and thawing; very low temperature can reach -7 to -8 DEG C, the temperature decreases with the increase of latitude or elevation of temperature; cooling effect on the slope depth of about 25cm; the slope soil temperature changes with time showed a positive cosine law the temperature change and lag 2-3H; range of daily evaporation of soil moisture is 0.001/d ~ 0.003/d. (4) results can be calculated by the model: Northern Slope freezing depth range of 0-15cm, the slope 5h above freezing and thawing, the slope surface is easy to form stable ice; test period of a day of freezing and thawing, frozen soil up to 5h, six days of freezing and thawing, soil freezing up to 32H; the temperature in soil freezing duration under the temperature below 1.5h, the soil is not easy to freeze; the air humidity is high, evaporation is small, the soil slope deep freeze and freeze thawing duration is large (5) soil factors. The sensitivity of influencing factors on soil freezing depth is: salt content, initial moisture content, dry density and soil aggregate specific heat. The sensitivity of influencing factors on soil freezing depth is: daily minimum temperature, solar radiation, air humidity.

【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU445

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