Mohamad Reza Madadi

This is the first attempt to study the effect of debris on the scour at side by side pier and abutment. A large set of experimental tests was carried out at the hydraulic laboratory of Shahid Bahonar University of Kerman, in a tilting flume with 10 m length, 0.8 m width and 0.5 m depth. Effect of debris shape, thickness, position, length, and the distance between abutment and pier was investigated. Results revealed that the main factor in deepening and developing of scour hole is the distance between pier and abutment, lp, by increasing the distance, the scour depth primarily increases and then decreases to eventually reach the scour depth at single pier. The observations indicated the significant effect of debris on dimensions of scour hole, for example, increasing the debris thickness and length increased the maximum scour depth up to 30 and 8%, respectively. Based on the measured data, some improvements were made on the existing equations and a set of new relations was presented to estimate the side by side pier and abutment scour depth.