重载铁路基床表层级配碎石渗透特性试验研究

重载铁路基床表层级配碎石渗透系数的快速、精确测定,对工程施工质量及工期的保证具有重要意义。基于达西定律研制适用于级配碎石的大型常水头渗透试验装置,并利用该装置考虑边壁效应进行一系列渗透试验,探究试样孔隙比e、不均匀系数Cu及特征粒径参数对其渗透系数K20的影响程度及规律。结合试验数据,以太沙基模型为基础,建立同时考虑孔隙及级配特征参数的渗透系数改进计算模型,并通过试验验证其精确性。结果表明:级配碎石的K20与其e2、平均粒径平方d502呈线性关系,与Cu呈负指数关系;d50对K20的影响权重最大,Cu次之,e最小;提出的计算模型具有较高准确性,可为新建重载铁路基床表层施工中填料渗透系数的快速测定及运营路基基床的渗透稳定性评估提供参考。

Experimental study of permeability properties of graded macadam in heavy haul railway subgrade bed surface layer

Rapid and accurate measurement of permeability coefficient for the graded macadam used in heavy-haul railway subgrade bed surface layer is of great significance to guarantee the construction quality and period.First,a large-scale constant-head permeameter suitable for graded macadam was developed based on Darcy’s Law,and a series of penetration tests considering wall effects was carried out using the aforementioned device.These initial tests were conducted to explore the influence degree and properties of pore ratio e,unevenness coefficient Cu,and characteristic particle size parameters on the permeability coefficient K20of a specimen.Besides,based on the Terzaghi model,an improved calculation model that took into account both pore and gradation characteristic parameters was established with reference to test data,and the accuracy of the model was verified through experiments.The results show that the graded macadam permeability coefficient K20 has a linear relationship with e2 and the square of mean particle size d502,and has a negative exponential relationship with Cu;d50 has the greatest influence weight on K20,followed by Cu,and e has the smallest influence.The proposed calculation model demonstrates a high degree of accuracy and can provide a reference for rapid determination of permeability coefficient for the fillers used in newly heavy haul railway subgrade bed surface layer under construction.Using this calculation model,the permeability stability of operating subgrade beds can be evaluated.