高铁路基粗颗粒土水力学参数测试方法研究

高铁路基粗颗粒土的水力学特性对路基内部水分运移及路基的长期累积变形有重要影响。而对这种高压实度的粗颗粒土，常规非饱和土试验仪器存在试样尺寸小、制样难度大的缺点，难以应用。介绍了一种用于测试高压实度路基粗颗粒土-水力学参数的试验装置，利用张力计和时域反射计量器，分别测量路基粗颗粒土在浸湿、干燥阶段不同高度处土体基质吸力、介电常数的变化情况，获得高压实度下高铁路基粗颗粒土土-水特征曲线；并通过瞬态剖面法获得路基粗颗粒土非饱和渗透系数与基质吸力的关系。试验结果表明，该套装置能够适用于最大粒径为20 mm的粗颗粒土，试样压实度最大可达到0.95。通过对一组试验结果分析，并结合Ekblad等试验结果，发现随着填料细颗粒含量增大，?（与进气值有关的参数）值逐渐减小，土体进气值增加；粒径越大，细颗粒含量越低，土体储水能力越低，对应n（与排水程度有关的参数）值越大。为路基粗颗粒土-水力学参数的测定提供了方法。

A method for measuring hydraulic parameters of coarse-grained soils for high-speed railway subgrade

Hydraulic characteristics of coarse-grained soil for high-speed railway subgrade profoundly influence internal moisture migration and long-term accumulative deformation of the subgrade. Conventional test methods have many disadvantages such as small size of sample and difficulties involved in sample preparation in determining hydraulic characteristics of such coarse-grained soil with high compactness, and thus can hardly be applied. A test device for determining hydraulic parameters of coarse-grained soil is presented thoroughly in this paper. Tensiometers and time domain reflectometers (TDR) are installed in the test device, allowing the measurement of matric suction and dielectric constant of coarse-grained soil at different altitudes during wet and dry stage; and consequently the soil-water characteristic curve (SWCC) of coarse-grained soil of high-speed railway subgrade with high compactness can be obtained. Also, the relationship bewteen unsaturated hydraulic conductivity and matrix suction of such soil can be obtained by transient profile method. The test result indicates that this device can be applied to the coarse-grained soil whose maximum particle size is 20 mm and whose degree of compaction may be up to 0.95. By analysing a group of experiment data and refering to data from Ekblad’s experiments, it is found that ? ( a parameter related to air entry value )decreases and air entry value increases with the increase of fine particle content in such soil, and that the largeness of particle size and low concent of fine particle suggest a low water storage capacity and high value of n. This article will provide a method for measuring hydraulic parameters of coarse-grained soils of subgrade.