多次冻融循环人工盐渍土路基模型试验研究

Experimental Study on Multiple Freezing‑Thawing Cycles of Artificial Saline Soil Subgrade

青藏铁路西宁至格尔木段为典型的季节性冻土区铁路,冻害频发,严重影响铁路的正常使用和安全运营,为了整治路基体发生冻害,结合成熟的注浆技术和传统撒盐法,提出注盐法整治路基冻害。在室内模型箱中填筑实体模型,进行封闭系统中多次冻融循环条件下人工盐渍土路基模型试验,探究人工盐渍土路基中温度、水分、盐分以及变形规律,验证注盐法整治路基冻害的可行性。试验结果表明:路基土体内温度变化趋势符合环境温度变化趋势的余弦函数变化波动规律,土体内温度变化较环境温度变化推迟36 h左右;温度梯度是引起水分迁移的主要因素,越接近冷端,迁移量越大,在冻结锋面处达到最大;在封闭系统中,盐分随着水分向冷端运移,但是盐分运移量较低,随着周期的推进,盐分呈逐渐降低的趋势;随着温度的周期性变化路基顶面的变形呈现出有规律的冻胀和融沉现象,但是最大冻胀量为0.08 mm,可见路基盐化之后路基土体基本不产生冻胀变形。

The Xining-Golmud section of Qinghai-Tibet Railway is in the typical seasonal frozen soil region.This railway suffers from frost damage frequently,which seriously affects the normal and safe operation of the railway.In order to remedy the frost damage of the roadbed,a salt injection approach combining the mature grouting technology and the traditional salt spraying method was put forward in this paper.The artificial saline soil model was prepared by filling soil in a model box.The model was then submitted to multiple freezing-thawing cycles test in a closed system.The change rule of temperature,moisture,salinity and deformation of saline soil was studied,and the feasibility of salt injection in embankment damage mitigation in the permafrost region was validated.The result displays that the variation trend of temperature in subgrade soil conforms to the variation law of cosine function of environmental temperature,and the temperature in subgrade soil has about 36 hours delay comparing to environmental temperature.The temperature gradient is the main factor causing water migration.The closer the area to the cold side,the greater the amount of water migration.The maximum migration appears at the freezing front.In the closed system,the salt migrates to the cold side with the water,but the amount is low.The salt content decreases gradually with the increase of cycles.With the periodic change of temperature,the deformation at the embankment surface presents a regular phenomenon of frost heave and thaw settlement,and the maximum frost heave is 0.08mm.It can be seen that the subgrade soil does not produce frost heave after subgrade salinization.