季节冻土区纤维改良路基土冻胀融沉特性研究

Study on Frost Heaving and Thawing Settlement Characteristics of Fiber-improved Subgrade Soil in Seasonal Frozen Soil Region

为研究冻融循环下纤维改良路基土含水率、纤维掺量对土体冻胀融沉特性的影响规律,通过开展室内单向冻融试验,测得不同含水率、纤维掺量下路基土的冻融特性,获得水分场变化、冻胀率、融沉系数、冻融全过程温度场以及结冰温度变化规律。结果表明,1)试样单向冻融过程中,随着深度的增加水相变程度越来越小,且冻融结束后各位置含水率不一致。不同初始含水率下的土样经历冻融循环后其水分重分布比较明显,不同纤维掺量的土样经历冻融循环后其水分分布基本相似。随着纤维掺量的增加,其水分迁移程度减小;2)8%~16%含水率范围内,其冻结竖向位移最大达到1.19 mm,其融化竖向位移最大达到2.56 mm,达到12%含水率时其冻胀率和融沉系数基本趋于稳定。在0%~0.5%纤维掺量范围内,其冻结竖向位移最大达到1.10 mm,其融化竖向位移最大达到2.85 mm;3)随着纤维掺量的增加其相变潜热越明显,土体结冰温度先降低后上升,在纤维掺量为0.3%时其结冰温度最低为-1.95℃,且达到结冰温度时间最长为14.1 min。研究成果可以为西部粉砂土分布地区铁路及工程建设提供参考。

In order to study the effect of moisture content and fiber content on the frost heaving and thawing settlement of subgrade soil improved by fiber under freezing and thawing cycles,the indoor unidirectional freezing and thawing tests were carried out,the changes of moisture field,frost heaving rate,thawing settlement coefficient,temperature field and freezing temperature in the whole process of freezing and thawing under different moisture content and fiber content were obtained.The results showed that:1)during the unidirectional freezing and thawing process of the sample,the water phase transition became smaller and smaller with the increase of the depth,and the water content was not consistent after the freeze-thaw process.The moisture redistribution of soil samples with different initial moisture content after freezing-thawing cycles was obvious,and the moisture distribution of soil samples with different fiber content after freezing-thawing cycles was basically similar.With the increase of fiber content,the degree of water migration decreases.2)In the range of 8%-16%moisture content,the maximum vertical displacement of freezing reached1.19 mm,and the maximum vertical displacement of thawing reached 2.56 mm.When the moisture content reached 12%,the frost heave rate and thawing settlement coefficient tended to be stable.In the range of 0%-0.5%fiber content,the maximum vertical displacement of freezing reached 1.10 mm,and the maximum vertical displacement of melting reached 2.85 mm.3)with the increase of fiber content,the latent heat of phase transformation became more obvious,and the soil freezing temperature first decreased and then increased.The lowest freezing temperature was-1.95℃when the fiber content was 0.3%,and the longest time to reach the freezing temperature was 14.1 min.The results of this study can provide reference for railway and engineering construction in silty sand areas in the west of China.