Effect of clay content on local scouring downstream of a submerged horizontal jet at maximum bed compaction

Articles in Press

Document Type : Research Paper

Authors

Department of Water Science and Engineering, Faculty of Agriculture and Environment, Arak University, Arak, Iran.

Abstract

Adding clay to the sediment composition downstream of hydraulic structures in rivers generally increase the soil resistance to fluid erosive forces by increasing particle adhesion, improving soil structure, reducing uncontrolled permeability. In the present study, the effect of adding clay to the sediment composition as a protective approach and reducing scour downstream of a submerged horizontal jet by reaching the maximum dry density of the sediment composition has been investigated experimentally. Experiments were conducted for two Froude numbers 4 and 6 and three types of sands with average diameters of 0.63 mm (S1), 1.81 mm (S2) with uniform grain size, and 1.74 mm (S3) with non-uniform grain size in a laboratory flume with a width and depth of 80 cm and a length of 10 m. In order to achieve maximum density, natural clay was used with percentages of 5, 10, and 15. The results showed that for the Sand S1, the scour hole dimensions with the finest grain size (S1) reach zero at a Froude number of 4, and at a Fr = 6, the scour depth, dune height, and scour hole volume decrease by 37%, 50.8%, and 56.25%, respectively. Also, for Sands S2 and S3 with the same average diameter but different grain size distribution, it was observed that particle non-uniformity under maximum density conditions has a significant effect on scour hole dimensions. The results showed that for the S2 grain size and Fr = 4, the scour hole dimensions reach their lowest value by adding 10% clay.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 29 September 2025

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