【作者】 韩天一；

【导师】 武建军；

【作者基本信息】 兰州大学 ， 固体力学， 2008， 硕士

【摘要】 在土体的冻结与融化过程中,土体中温度、水分和应力之间相互耦合机理是一个涉及到热传质学、热力学、流体力学和物理化学的极其复杂的综合问题。由于冻土的特殊性质,尤其是冻土中冰透镜体的出现,使得对冻土的研究与一般土体相比更为复杂,要有效的预防和抑制土体在冻结与融化过程中的冻胀与融沉现象,就必须充分考虑温度、水分和应力的三场耦合作用机理。本文在Harlan模型的基础上,综合考虑了刚性冰假定和水动力学模型,将土体视为空间弹性体,以等效含水量代替冰含量简化水分迁移方程,并采用冰阻抗因子求解冻结区的各计算参数,运用显热容法处理冰水相变潜热,进一步考虑了土体应变对含水量的影响,建立了土体冻结过程中水—热—力的三场耦合模型。运用有限元法和差分法对饱和土冻结过程中水—热—力的耦合机理进行了数值离散,给出了离散后的有限元方程,并在论文最后模拟了土柱和冻土路基的冻结过程,给出了冻土中含水量分布、应力分布规律,以及冻结时间、温度边界条件对冻土中含水量分布、应力分布的影响,经过对计算结果的分析研究,认为为保护冻土区的建筑物的稳定性和运营安全,对冻土路面采取保温措施和降低路基中温度是切实可行的。更多还原

【Abstract】 The coupled mechanism of the moisture-heat-stress fields is an extremely complex problem concerning thermodynamics, hydrodynamics, fluid mechanics, physics and chemistry in the process of freezing and thawing of the soil. The special characteristics of the frozen soil, especially the emergence of ice lens, make the research of the frozen soil more complex than the common soil. To prevent and control the phenomenon of frost-heaving and thawing-settlement during freezing and thawing of the soil, sufficient attention should be paid to the coupled mechanism of the moisture-heat-stress fields.Based on the model of Harlan, this paper synthetically considers the hypothesis of rigid ice and the model of hydrodynamics, and regards the soil as elastic. Most of the earlier scholars treat the ice content as a coupled factor. This paper simplifies the moisture-migration-equation through substituting equivalent water content for ice content, adopts ice-impedance-factors to solve calculation-parameter, uses apparent heat capacity to deal with phase change latent heat, and considers the influence of soil strain on the water content. The model of the coupled moisture-heat-stress field in freezing soil is established.At the end of this paper, FEM and FDM are employed to solve the coupled equation of the moisture-heat-stress field during the freezing of the saturated soil, simulate the freezing process of soil-pole and frozen bed, and summarize the laws of water-content-distribution and the stress distribution, and the influence of frozen time, temperature boundary on water-content-distribution and the stress distribution. From analysis of the results, the conclusion is drawn that it is effective to protect the stability and the security of buildings in the frozen region through heat preservation and temperature control of the bed.更多还原