Presenting Some Equations for Calculating the Non-Darcy Flow Coefficients in Rockfills

Rockfill dams are usually used for affecting the flood and reducing the peak discharge. The materials used in these dams will usually make the flow turbulent, therefore Darcy's law can not be used for this kind of dams and the equations based on the non-Darcy flow must be applied. Non-Darcy flow equations are showed in two general ways including: and. One of the main parameters for flow simulation through this type of media is N, which can be specified empirically using experimental data. N is a parameter for flow turbulence and varies from 1 (laminar flow) to 2 (fully turbulent flow). One of the problems with some of non-Darcy equations (e.g. Ergun) is that they can not compute  and N directly. In this research using the Ergun equation and mathematical analysis, a few equations have been derived and presented for computing N and  and finally a new equation has been presented for the equivalent hydraulic conductivity (Ke) coefficients in porous media. A standard example was used for the verification of the resulting equations. Some values were assumed for the soil properties and the value of N,  were computed using the proposed equations in this research study. N was also specified using a non-linear regression analysis and was compared with the corresponding values obtained from the proposed equations. Comparison of the both sets of results showed that the computed N values are relatively precise especially for the boundaries (N=1 and 2).