土体冻结过程中的地铁基坑稳定性分析

The Analysis of Stability of Metro Foundation Pit In The Process of Soil Freezing

结合哈尔滨某地铁车站基坑的现场监测数据,对季节性冻土地区土体冻结过程对地铁基坑变形稳定性的影响进行了研究。结果表明:气温下降至零度以下时,土孔隙中的水逐渐结冰,冰饱和度发生变化,随着冰饱和度的增大,土的体积也逐渐增大,土的承载能力和稳定性也有所提高,当冰饱和度达到最大值时,土的冻胀过程结束;基坑土体的冻胀现象在最低气温开始下降至零度以下的一段时间内最为强烈,基坑侧壁水平位移和混凝土支撑轴力显著增大,而随着气温的进一步下降,土中未结冰水已经较少,冻胀现象不再明显,基坑侧壁水平位移和混凝土支撑轴力也趋于稳定。研究成果在土体冻结过程对基坑稳定性的影响方面对指导基坑施工有重要意义。

Based on the site monitoring data of the foundation pit of a subway station in Harbin,this paper studies the influence of freezing process of soil in the seasonal frozen soil area on the deformation stability of subway foundation pit.The results show that:When the temperature dropped below zero,the water in the soil pores gradually freezes and the ice saturation changes.With the increase of ice saturation,the volume of soil gradually increases,and the bearing capacity and stability of soil also increase.When the ice saturation reaches the maximum,the frost heaving process of the soil ends.The frost heaving of the foundation pit is most intense in a period of time when the minimum temperature begins to fall below zero,and the horizontal displacement of the side wall of the foundation pit and the axial force of the concrete support increase significantly.However,with the further decrease of the temperature,the unfrozen water in the soil is less,the frost heave phenomenon is no longer obvious and the horizontal displacement of the side wall of the foundation pit and the axial force of the concrete support also tend to be stable.The research results are of great significance in guiding the construction of foundation pit in the influence of soil freezing process on the stability of foundation pit.