Laboratory Modeling of Energy Dissipation in Six-foot Drop Broken-back Culverts

Abstract

Current mitigations for scour include expensive external energy dissipators such as large riprap basins or concrete stilling basins at culvert outlets. The research presented in this thesis examines the effectiveness of inexpensive internal energy dissipators to maximize the energy loss within the culvert by forming a hydraulic jump inside the culvert barrel. A broken-back culvert in the laboratory represents a 1 (vertical) to 2 (horizontal) slope after the upstream inlet and then continues 138 feet at a 1 percent slope to the downstream outlet. The prototype for these experiments was either a two barrel 10-foot by 10- foot, or a two barrel 10-foot by 20-foot reinforced concrete culvert. The drop between inlet and outlet was selected as 6 feet. Three flow conditions were simulated, consisting of 0.8, 1.0 and 1.2 times the culvert depth.