Effect of Rheology on Earthen Embankment Breaching

ABSTRACT

Dam breaching results in severe flooding associated with huge losses to lives and properties. Hydraulic and numerical model studies are used to analyze the breach evolution and the behavior of outflow due to breach. The present study uses FLOW-3D, for dam breaching to investigate the effect of rheology on dam breach. The Reynolds-Averaged Navier–Stokes (RANS) equations and the volume of fluid (VOF) equation are used as the governing equations for fluid flow and free surface tracking, respectively. In addition, the Renormalized group (RNG) is used for the turbulence closure model. The planar breach erosion, where the breach is assumed to take place uniformly across the dam length, is simulated for a trapezoidal dam with overtopping. Effect of rheological parameters, i.e., density and viscosity of the fluid stored behind the dam, on the evolution of the dam surface, the flow surface profile, and the peak discharge through the breach is studied. Water along with eight other different fluids is considered in the study. Simulated results for all the cases indicate that the dam breach process is faster, and the peak breach discharge is higher when the fluid is less viscous. A similar trend is also observed when the fluid is with higher density. Two empirical equations, one for the peak breach discharge and the other for the erosion rate, are developed using regression analysis on the simulated results.

Keywords: Planar Dam breach, FLOW-3D, RNG Turbulence model, Peak breach discharge, Erosion rate.