Influence of the anisotropy of the material on the pore water pressures within the downstream shell of a rockfill dam in overtopping scenario

The compaction tasks developed during the construction of the shell of rockfill dams may crush the particles of the material close to each surface layer. If so, this can cause local variations in the permeability of the material and consequently an alteration of the hydraulic pattern of the seepage through the shell as well as the pore water pressures developed within it. This article summarizes the study of this effect through hydraulic numerical modelling developed by the FLOW-3D commercial code. Such study presents a discussion about the influence of the altered and unaltered zones of the layers on the general flow pattern, particularly in the downstream water level depths, hydraulic gradients and pore water pressures. The tests have been set up with a non-laminar seepage equation using a parabolic relation between hydraulic gradient and seepage velocity. The numerical models simulate homogeneous rockfill formed by isotropic layers with different permeability, which result in an overall anisotropic dam body.