Bridges are one of the important structures built by humans for safety in crossing rivers. But one of the most common causes of bridges failure is flood, and scouring in the pier and abutment of bridges is the most common cause of flood damage to bridges. In this study, the scouring phenomenon around the semi-circular abutment was studied. This study was designed with the aim of eva‎luating the effectiveness of the cable in reducing scour depth as a function of various parameters. Therefore, the laboratory flume of Isfahan University of Technology was used to study the effectiveness of cable on scouring depth. For this purpose, a semi-circular abutment with a length of 4 cm (L=4 cm) was used. Also, a flexible and water-resistant cable was used. Based on the dimensional analysis, it was determined that the scour depth in the abutment with cable is a function of the cable diameter (dc), thread angle of cable (αt) and step (S). For cable diameter, three values were selected with dc=0.11L, dc=0.24L and dc=0.31L. Three angles of 17°, 22° and 28° were used for the thread angle of cable. Also, S, S/2 and S/3 steps were considered. A total of 28 experiments were performed. The experiments were carried out under clear water flow conditions with a flow intensity of U/Uc=0.8. The flow rate and flow depth were set to 50 Lit/s and 20 cm, respectively. The effects of increasing the cable diameter, increasing the cable thread angle and reducing the step were investigated.In addition to the above results, reduction coefficients (Kc) were calculated for the cable. It was found that due to increasing the diameter of the cable and decreasing the step, the performance of the cable increases first, and after reaching the optimal state, the performance of the cable decreases. However, due to the increase in the thread angle of the cable, the performance of the cable decreased first, and from the 22° thread angle, the performance increased until it reached the optimal performance. Finally, it was found that the optimal settings for cable diameter, cable thread angle and step are dc=0.24L, 28° and S/2, respectively. With these settings, the highest performance of the cable in reducing the scour depth around the semi-circular abutment was achieved by 30.5%. In general, it can be said that choosing the correct value for the parameters affecting scour depth can optimize the efficiency of a countermeasure.

منوچهر حيدرپوراسفرجاني

شمس اله ايوبي , محمد شايان نژاد