Analysis of Non-Darcy Flow in Rock Fill Materials Using Gradually Varied Flow Method

Analysis of flow through rockfill materials is usually carried out by solving the differential equation which is a combination of nonlinear [i=mvn] and continuity equations. However, solving this differential equation either by means of finite difference method or similar procedures is relatively time consuming, and with uncertainty involved in water surface profile this becomes even more difficult. To analyze flow through rockfill materials an alternative method which is based on gradually varied flow theory may be applied that is comparatively simpler and less time consuming. To apply this alternative method it is necessary to examine the validity of assumptions on which gradually varied flow method are based. Moreover, the involved parameters in gradually varied flow equation should be reverted to porous media condition. In this research by conducting a vast number of experiments on various types of materials the acceptability of assumptions of gradually varied flow method for analysis of flow through coarse porous media is investigated and the effect of physical characters of porous medium such as void ratio, uniformity coefficient Cu, gradation coefficient Cc and viscosity of fluid as well as certain features of flow such as velocity and hydraulic gradient are also examined. Findings indicate that: 1). by accepting some degrees of discrepancies, one may use the gradually varied flow method for analysis of flow through coarse porous media. 2). the permeability parameters of coarse porous media may be successfully related to the physical characters of granular materials. 3). A Comparison between observed and computed flow profiles through media indicates accuracy and applicability of equations that are derived by authors of this paper.