Prediction of Scour Depth in a Group of Piers in Staggered Arrangement Using Experimental and Regression Models

The paper presents the results of a controlled experimental study to investigate the effect of mutual interference of the bridge piers placed in a staggered arrangement on local scour depth. Experiments were conducted in a standard recirculating tilting bed water flume 12 m long, 0.60 m wide, and 0.70 m deep. The size of the pier models used was 62 mm and 42 mm. For the mobile bed experiments, the uniform-sized river sand used had an average mean size, d50 = 0.23 mm and 0.30 mm. Estimation of the scour depth of the staggered arrangement of the group of piers with a constant angle of attack of 45° but varying radial pier spacing had been achieved using 54 laboratory datasets. The results of the experimental studies were compared with artificial neural network functions and random forest model analysis. From experimental results, it is found that the downstream piers were placed at a radial spacing greater than five times the diameter of the bridge pier; the vortex shedding effect produced by the front pier on the rear piers is negligible.