寒区级配碎石冻胀正交试验研究

级配碎石作为季节性冻土地区高铁路基基床表层填料，其防冻胀问题尤为关键。为研究在不同条件下级配碎石的冻胀特性，选取不同的含水率、细颗粒含量、冷端温度和压实度进行了室内封闭系统冻胀正交试验。结果表明，在不同因素、不同水平的组合时，级配碎石有不同程度的冻胀。当级配碎石含水率为5%时，试样的冻胀率较小；当含水率超过7%时，大部分试样冻胀率超过1%。对冻胀过程中试样温度场、冻结深度、冻胀变形过程和冻后试样含水率分布进行了分析，发现冻后试样冷端位置的含水率高于初始含水率，暖端位置的含水率低于初始含水率。当以冻胀率作为参考序列，其他试验条件作为比较序列时，灰色关联度分析结果表明，影响级配碎石冻胀率的主要是含水率，其次为细颗粒含量、压实度及冷端温度，其关联度相差不大。并得出了最有利于冻胀发展的组合。为满足寒区高速铁路变形量的要求，提出以控制级配碎石含水率小于5%为指标。

A study of orthogonal design tests on frost-heaving characteristics of graded crushed rock

Seasonally frozen soil is distributed widely in the Northeast China. The prevention measures against the frost heave of graded crushed rock, which is used as the filler of surface layer in subgrade, are crucial to high-speed railway constructed in seasonally frozen soil region due to the strict requirements of subgrade deformation. In order to study the frost heave characteristics of graded crushed rock under different conditions, water content, fine content, cooling temperature and compaction are chosen as influential factors of frost heave characteristics. The closed system laboratory frost heave experiments have been performed based on the orthogonal design, showing that different frost heave amounts appear in different combinations of factors and levels. The frost heave ratio of most graded crushed rock samples is small when water content is 5%, and it exceeds 1% when water content is above 7%. The temperature field, frozen depth, frost heave deformation process and water content distribution in sample after freezing are analyzed. It is found that the water content is greater than the initial water content at the cold side, and is lower than initial water content at the warm side. Using the frost heave ratio as a reference sequence and other factors as comparison sequences, the correlation degrees among water content, fine content, compaction, temperature at cold side and frost heave ratio are analyzed with the gray correlation method. The results from this analysis indicate that water content produces the most significant effect on the frost heave ratio of graded crushed rock. The water content of graded crushed rock should be maintained below 5% in order to prevent frost heave development in the cold regions.