Estimation of Local Scour Depth Around Bridge Pier

Hydraulic bridges are critical components in infrastructure network. One of the major causes of its collapse is due to local scouring of its foundations. Hence in this study, the mechanism and various factors affecting local scour around bridge piers was analyzed. For this, a software platform Hydrologic Engineering Center River Analysis System (HEC-RAS) was used to evaluate local scouring around piers of spillway bridge with radial gates of Telengiri Irrigation Project located in Koraput district of Odisha, India. Soil samples were collected at the site and tested in the laboratory to determine various properties required for model inputs and assess the vulnerability of soil for scouring. Geometric data and design specifications of radial-gated bridge structure along with soil properties of the case study were used to build HEC-RAS model and then steady-state flow profiles were given to calculate local scour depth. Analytical methods such as Kothyari, Richardson, and IRC equations were used to corroborate local scour depth values with the model. The model predicted scouring of ۸.۲۹m which is close enough to values predicted by Richardson equation (۸.۹۵ m). This small discrepancy was due to not accounting for bed conditions and armoring of bed material. Parameters were varied in the model such as discharge, width and geometry of piers, skew angle of bridge and piers, angle of attack, and different bed configurations to simulate their effect on local scour depth. The soil was found to be highly erodible as per the soil erodibility factor obtained from the Wischmeier equation.

Keywords:

local scour , Hydrologic Engineering Center River Analysis System , spillway bridge , Telengiri Irrigation Project , Erodibility