Study of Scour Protection of Composite Foundations by Multihole Collar

Based on the theory of scour protection, a multihole collar for composite foundation was designed, and the effects of collar width, thickness, and pore structure on the water flow around the foundation, the morphology of scour pits, and the time course characteristics of scour were investigated by using Flow-3D software. The results show that increasing the width of the multihole collar can reduce the strength of the horseshoe vortex in front of the pile and reduce the vortex structure near the foundation; increasing the thickness of the multihole collar can weaken the strength of the tail vortex, resulting in siltation of sediments downstream of the foundation; and the pore structure can disrupt the boundary layer of the water flow near the collar and reduce the local scour around the foundation. Among them, the thickness of the retaining collar has the most significant effect on the scour protection performance of the multihole collar, when the multihole collar thickness was increased from 2 mm to 3 mm, the maximum scour depth near the foundation was reduced by 29.08% and the start of scouring was delayed by almost 2.5 times.