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Comparative study of reduction of pier scour using octagonal and circular collars

2024; Elsevier BV; Volume: 298; Linguagem: Inglês

10.1016/j.oceaneng.2024.117169

1873-5258

Lav Kumar Gupta, Bharadwaj Rahul, Manish Pandey,

Soil erosion and sediment transport

This study experimentally evaluated the performance of octagonal and circular collars in reducing pier scour. In this regard, 33 experiments are carried out under steady uniform flow and clear water conditions. The study used two distinct collars, octagonal and circular, as scour countermeasures. Octagonal collars (dc1o,dc2o, dc3o, and dc4o) and circular collars (dc1c,dc2c, dc3c,anddc4c) of four different sizes 1.5 b, 2 b, 2.5 b and 3 b are used in the experiments, respectively. The collar is placed at four elevations, i.e., z1 = 0, z2 = 0.25 y, z3 = 0.5 y, and z4 = 0.75 y, where y is the water depth above the sediment bed. When octagonal collars (dc1o,dc2o, dc3o,anddc4o) are placed on the bed and at 0.25 y, the percentage of scour reduction is 25–100% and 12–34%, respectively. Additionally, when circular collars are placed on the bed and at 0.25 y, the percentage of scour reduction is 16–100% and 12–30%. For the same collar diameter, beyond the 0.25 y elevation above the sediment bed, both octagonal and circular collars resulted in almost the same percentages of scour reduction. The octagonal collar performed better than the circular collar as a countermeasure when kept on the bed and at 0.25 y. This study proposes relationships for maximum scour depth and temporal scour development for collar with pier. From statistical and sensitivity analyses it is observed that the location of the collar followed by collar width are the most influential factors.