On the Permeability of the Coarse Materials at the Low Hyraulic Gradient.

在本研究中，进行了低水力坡度下粗粒料渗透特性的试验研究。(水力坡度：i=0.005-0.1.)粗料的渗透性是否符合达西定律尚不清楚，特别是在低水力坡度下。当土结构中的排水系统是影响建筑物安全的重要因素之一时，渗透率是一个重要的数值。本实验所用的材料是直径D=30 mm、15 mm和5 mm的三种玻璃微珠。得到的结果如下：1)在上述水力坡度之间，流经粗料的无压流不符合达西定律。2)同样地，通过粗料的受限流也不符合达西定律。3)流经粗料的指数定律适用于粗料的流动。B：系数。4)作为Analysys对实验数据的结果，b的值约为0.7。这是不符合达西定律的。

In this study, the experiment about the permeability of the coarse materials was carried out at the low hydraulic gradient. (Hydraulic gradient : i=0.005-0.1) It is not clear that the permeability of the coarse materials is valid to Darcy's Law or not especially at the low hydraulic gradient. This permeability is the important value when the drain system in the earth structure is one of important factors for the safety of structure.The materials used in this experiment were three kinds of glass beads with the diameter D=30mm,15mm and 5mm.The results obtained are as follows:1) The unconfined flow through the coarse materials is not valid to Darcy's Law between above mentioned hydraulic gradient.2) Similary, the confined flow through the coarse materials is not valid to Darcy's Law, too3) The exponent law as follows is valid to the flow through the coarse materials.v=a*i^b where v : velocity, i : hydraulic gradient and a , b : coefficients.4) As the results of analysys of the data obtained from experiments, the value of b is about 0.7. This is not valid to Darcy's Law.