高温冻土区填土路基的地基融化固结变形分析

Analysis on Thawing Consolidation and Deformation of Ground under Earthen Embankment in Warm Permafrost Region

针对青藏铁路高温冻土区普通填土路基的融沉变形,基于拉格朗日法描述的大变形固结理论及考虑相变作用的路基传热理论,对高温冻土区不同高度填土路基的温度场和地基融化固结变形进行计算分析,并与现场监测结果进行对比。温度场分析结果表明,高温冻土区4和6m高填土路基在短期内可使冻土上限略微抬升,但下伏多年冻土存在缓慢升温过程,其升温幅度每年约为0.02℃左右;随着气候逐渐变暖,填土路基下冻土上限在后期会逐渐下降,且填土路基高度越小则上限下降量越大,最终在路基下部形成融化盘。融化固结变形分析结果表明,填土路基沉降变形表现出季节性,即暖季沉降变形发展迅速,冷季发展缓慢,发展趋势与现场监测结果吻合良好;在给定的地质条件下,2,4和6m高填土路基在竣工50年后其沉降变形量分别为255.2,470.4和689.7mm,即沉降变形量与其高度呈正比,且高填土路基沉降变形的季节性更显著;填土路基高度和多年冻土的含冰量是影响填土路基沉降变形的主要因素。

Considering the thawing settlement of traditional embankments along Qinghai-Tibet Railway in warm permafrost regions,the large strain consolidation theory was proposed by combining large strain consolidation theory with UL （Updated Lagrangian） description and thermal conduction equation with phase change.The thermal regimes and thawing settlements of embankments with various heights in warm permafrost regions were researched according to the proposed theory and the calculations of temperature and settlement were compared with in-situ monitoring results.Thermal calculation results indicate that the permafrost table moves upwards slightly beneath the 4 m-height or 6 m-height embankments in the first few years after embankment construction,but the underlying permafrost warms slowly,and the increase gradient of ground temperature is about 0.02 ℃ annually.Under climate warming,the permafrost table begins to decline quickly in late stage of embankment construction.The lower the embankment is,the larger the table＇s decline is,and finally thaw bulb occurs beneath embankment.The analysis results of thawing consolidation and deformation show that the embankment settlement develops quickly during the warm seasons but slowly in cold seasons,which changes in a seasonal trend and has good agreement with field monitoring results.The settlements of 2,4 and 6 m-height embankments with the given geological conditions used in calculation are 255.2,470.4 and 689.7 mm after 50 years of the construction respectively.The higher the embankment is,the larger the thawing settlement is,and the seasonal trend of settlement is more obvious.The height of embankment and ice content of frozen soil are the major influence factors of embankment settlement in permafrost regions.