换填法抑制季节冻土区铁路路基冻胀效果分析

Analysis on the Effect of Replacing-Soil Method on Inhibiting Frost Heave of Railway Roadbed in Seasonal Frozen Soil Region

以沈哈线路基A、B组填料为研究对象,采用室内冻胀试验,研究粉黏粒含量对其冻胀特性的影响。试验表明:路基填料的冻胀系数随粉黏粒含量增加而增加,且增幅逐渐增大;结合沈哈线路基基床厚度及沿线最大冻深,为保证路基不产生冻胀破坏,应确保换填用路基A、B组填料中不含有粉黏粒。采用非稳态相变温度场的数学模型和热弹塑性冻胀模型,进行沈哈线换填试验段冻土路基冻融过程温度场及冻胀应力、变形场计算分析。结果表明:天然地面下2m左右为冻融活动层,是诱发路基土体冻胀的主要因素;用非冻胀性A、B组填料换填基床厚度范围内的冻胀性土层后,路堤填筑土体无冻胀变形产生,路基中的拉应力(拉应变)区域外移到距离路堤坡脚4m以外的天然地表下土体,大大减弱了对路堤的破坏作用,计算结果与实际情况相符。

A,B class filler obtained along Shenyang-Harbin Railway was taken as the research object.The effect of silt and clay particle content on the frost heaving characteristics of filling material was investigated with indoor freezing and heaving experiments.The results show that the frost heaving coefficient of the roadbed filling increases with the increase of silt and clay particle content,and the amplitude increases gradually.To prevent the existing subgrade from frost heaving damage,it is necessary to make A,B class filler not contain silt and clay particle,considering the thickness of subgrade bed and the maximum frozen depth of Shenyang-Harbin Railway.The mathematical model of the unsteady phase transition temperature field and the thermo-elasto-plastic frost heave model are employed to calculate and analyze the temperature field,the frost heave stress and the deformation field of the frozen soil embankment during its frost heaving process in the replacing soil test section of Shenyang-Harbin Railway.Results show that about 2 m below the natural ground surface is the freezing-thawing active layer,which is the main factor to induce the frost heave of the subgrade.The embankment will be absent from frost heave deformation if the soil with frost heave sensitivity is excavated and then the non-frost-heave A,B group material is filled in the excavated subgrade bed.Moreover,the tensile stress（tensile strain） zone of the roadbed shifts more than 4 m outward from the toe of the side slopes,reducing the damage to the embankment greatly and enhancing the stability of the roadbed.The calculation results agree well with the actual situation.