Effect of Density and Depth of Six-Legged Elements Placement on Rectangular Abutment Scour Depth

The reviews of past researches have shown that abutment scour plays an important role in bridge failures. Hence, protection of bridges against scour is a significant issue. For existing bridges, armoring methods, like riprap, has a wide application. In areas where providing stones is expensive concrete blocks or similar techniques have been applied. In this study for the first time the application of six-legged concrete elements has been experimentally investigated. The six-legged elements have been placed in three different densities (open, medium and dense) and three different placement depths (under the bed, above the bed and medium case). Each alternative has been tested under different flow conditions. Generally, the results proved that the six-legged elements could considerably reduce the scour depth under different flow conditions so as the maximum scour depth of abutment nose was reduced up to 86%. The maximum reduction of scour depth was obtained when the high dense six-legged elements had been placed above the bed.