Investigating the Influence of Filter Uniformity Coefficient and Effective Pore Size on Critical Hydraulic Gradient and Maximum Erosion of Dispersive and Non-dispersive Samples


1 Associate Professor, Department of Civil Engineering, University of Zanjan, Zanjan, Iran

2 M.Sc. Graduate, Department of Civil Engineering, Zanjan University, Zanjan, Iran


Filter is one of the main components of embankment dams. By a simple but effective performance, filter protects the dam against erosion and soil scouring in impervious core caused by leakage (piping) and makes it safe. Interaction between filter and erodible base soil is a complex phenomenon which is dependent upon several factors, and has challenged researchers for better understanding the filtration system behavior. Therefore, more investigations in this field are needed. Identification of dispersive soil filtration is of great importance because of high erodibility potential of these soils. In this study, in order to evaluate dispersive soil filtration a device is designed and made by the authors for filter testing. This device can measure the hydraulic gradient in flow path by using a controlled flow head. By performing filter tests on dispersive and non-dispersive soil samples, the effect of uniformity coefficient and effective pore size of the filter on critical hydraulic gradient has been studied. The critical hydraulic gradient varies with the change in filter uniformity coefficient, and by increasing the effective pore size of the filter, critical hydraulic gradient is decreased.