Investigation of mitigation of local scour at bridge piers using cellular filling system

Local scour around the piers of river bridges is one of the most significant hydraulic problems affecting the stability of transportation structures. In this study, the effectiveness of the geocell an alternative method for controlling local scour was examined experimentally. The experiments were conducted under clean-water scour conditions using coarse bed sediment with an average diameter of 4,05 mm under various flow rate conditions. By systematically varying the depth and length in the flow direction of the geocell placed around a cylindrical bridge pier, the relationship between these parameters and Frd and dsmax was investigated. Measurements revealed that the geocell system prevents lateral movement by confining the bedding sediment and significantly reduces the maximum scour depth compared to the reference condition. It was determined that the system's scour prevention efficiency is directly dependent on the set cell dimensions; the highest efficiency (54%) was achieved with a shallow (εz=5 cm) and narrow (εx=7,5 cm) cell configuration. As cell depth and length increased, a decrease in system efficiency was observed because it became easier for the downward flow and vortices to affect the bed sediment. As part of the study, multiple nonlinear regression models were developed to estimate the dimensionless maximum scour depth using experimental data, and their statistical fit (R² = 0,721) was evaluated. As a result, it was demonstrated that the application of geocell for scour control at bridge piers can be considered a stable protection method compatible with coarse sediment that does not require physical intervention in the existing bridge structure.