Modeling the Mechanics of Rock Scour in Unlined Dam Spillways: Fid-Bau Portal

Modeling the Mechanics of Rock Scour in Unlined Dam Spillways

Gardner, Michael H.

Scour of rock by hydraulic plucking is a critical issue facing many of the world’s dams at which excessive scour of the dam foundation or spillway can compromise their performance. However, the mechanisms that govern plucking are not fully understood, and scour assessment methods are either highly empirical or significantly simplified. Here, a numerical approach is presented that directly models fluid-solid interaction during scour by modeling the fractured rock mass using the Discrete Element Method (DEM) and the Lattice Boltzmann Method (LBM) for simulating the fluid. Often flow over spillways is highly turbulent, requiring numerical methods that can accommodate high Reynolds number flows. As such, Large Eddy Simulation (LES) has been implemented in the LBM to account for the kinematic energy dissipation at scales that are not resolved by the grid resolution in the fluid model. This approach thus can explicitly model particle geometry and how this influences fluid-solid interaction such that local site conditions and how they contribute to the likely mode of scour can be expressly evaluated. This can provide valuable insight into which strategies are most effective in addressing scour risk in dams and structures interacting with water based on site-specific conditions.