高速铁路路基用砾类盐渍土变形特征研究

Study on Deformation Characteristics of Gravel Saline Soil Constructing Subgrade of High-speed Railway

为研究砾类盐渍土构筑高速铁路路基的技术要求及变形特征,结合某高速铁路建设,开展考虑变形控制要求的盐渍土路基盐胀与溶陷系数阈值分析,在此基础上,通过溶陷与盐胀试验、现场浸水试验、冻融循环试验,研究降水及季节交替工况下砾类盐渍土路基的变形特征。结果表明:对于不同设计速度与轨道类型的路基,其盐胀与溶陷系数阈值不同;在单次降温条件,压实系数小于0.97的砾类盐渍土以“体缩”变形为主,压实系数大于0.97的砾类盐渍土盐胀变形较明显;当降雨达到年均降雨量及极端单次降雨时,砾类盐渍土路基可完成不小于65%和95%的溶陷量;在冻融循环条件下,压实系数较小的砾类盐渍土路基变形呈融沉趋势,而压实系数较大的砾类盐渍土路基变形则呈盐胀趋势。基于砾类盐渍土变形研究成果,初步提出满足溶陷与盐胀控制要求的砾类盐渍土路基设计原则。

To study the technical requirements and deformation characteristics of gravel saline soil constructing the subgrade of high-speed railway, and combined with the construction of a high-speed railway, threshold analysis of salt expansion and subsidence coefficient of saline soil subgrade considering the deformation control requirements was performed. On this basis, salt expansion and collapsibility test, field immersion test, experiment of freezing and thawing cycles were carried out to study the deformation characteristics of subgrade filled with gravel saline soil under infiltration and seasonal alternation conditions. The results show that the thresholds of salt expansion and subsidence are different for subgrade with different design speeds and track types. In a single cooling condition, the gravel saline soil is mainly characterized by “body shrinkage” deformation with the compaction coefficient less than 0.97, but it will convert to salt expansion deformation when the compaction coefficient is greater than 0.97. The dissolution ratio of collapsibility of gravel saline soil subgrade is not less than 65% and 95% when the rainfall reaching annual average rainfall and extreme single rainfall. Under the conditions of freezing and thawing cycles, the deformation of gravel saline soil subgrade with a smaller compaction coefficient can be described as a tendency of melting and sinking, while the deformation of the gravel saline soil subgrade with a larger compaction coefficient tends to swell. Based on the research results of the deformation of gravel saline soil, the design principle of gravel saline soil subgrade that meets the requirements of subsidence and salt expansion control is proposed.