Abstract
New construction practices for roller compacted concrete (RCC) overlays and stepped chutes are changing the step geometry from a traditional square-edge, vertical face to a 45° beveled face. A large-scale 3(H):1(V) (i.e., θ = 18.4°) stepped chute model was tested with a 45° beveled face step with a height (h) of 152 mm. Results were compared to data on square-edge, vertical face steps previously obtained. The distance to the inception point of free-surface aeration normalized by the surface roughness was reduced approximately 25% for the same Froude number defined in terms of roughness height. An existing inception point relationship for vertical face steps was adjusted with a best fit correction factor to predict the free-surface inception point for this chute slope and beveled face angle. Relative flow depths, mean air concentration, and energy loss data showed similar general trends for vertical face and beveled face steps, but the depths and air concentrations for beveled face steps were slightly higher for equal values of relative free-surface inception point, Li/L, and relative step height (e.g., h/dc). Energy loss at the free-surface inception point ranged from approximately 20 to 40% of total head for both step types. Additional research is needed to determine the generalized effects of the bevel angle and the chute slope on flow properties. This research is expected to be used by field engineers for the design of stepped chutes with beveled face steps.
Highlights
Like roads, bridges, and buildings, dams are affected over time by structural deterioration, sedimentation of reservoirs, and changes in land use that can alter hydrology associated with the dam
One option commonly used for embankment dam rehabilitation is a roller compacted concrete (RCC)
While forms are not required for placement of RCC, forms allow for better compaction along the step edge
Summary
Bridges, and buildings, dams are affected over time by structural deterioration, sedimentation of reservoirs, and changes in land use that can alter hydrology associated with the dam. Rehabilitation of these dams is often necessary. Placement with constructed vertical forms can be costly and time-consuming, but the characteristics of RCC enable construction of a beveled geometry (e.g., 45◦ angle) using slip forms that move with the placement This provides an attractive result and is economical to construct, so it is becoming widely implemented in the United States even though little is known
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