Improvements to the hydraulic performance of culverts under inlet control conditions by optimisation of inlet characteristics

Abstract

With renewed interest in the optimisation of the hydraulic performance of new and existing culverts, particularly relevant to South Africa’s evolving road network and anticipated climate-induced rainfall changes, this research investigated the benefit of angled wingwall and headwall combinations and considered the installation of a ventilation device in order to improve culvert performances. Through experimental modelling at the University of Pretoria Water Laboratory, the angled wingwall and headwall combinations demonstrated significant flow improvements compared to square inlets. It was also demonstrated that a ventilation device could cause flow through culverts to flow under inlet control conditions where it would otherwise have flowed under outlet control conditions. Additionally, the study proposes design coefficient adjustments for square inlet culverts operating under inlet control conditions. The proposed improvements can be applied during design stages, but the findings also propose prefabricated inlet elements as cost-effective solutions for existing culverts, thereby facilitating quick upgrades without the need for lengthy road closures while potentially enabling benefits for pedestrian traffic. Ultimately, this study underscores the potential of innovative and novel design modifications to enhance culvert performance, offering sustainable and economical alternatives to conventional replacement practices while advancing hydraulic engineering resilience in response to evolving infrastructural and environmental demands.