Simultaneous use of cable and collar to prevent local scouring around bridge pier

Various methods to control scour around bridge piers have been proposed. In the present study the application of cable or collar and a combination of cable and collar were examined experimentally, as countermeasures against local scouring at a smooth circular bridge pier, close to threshold flow conditions of initiation of uniform sediment motion. The results show that the simultaneous use of cable and collar has high efficiency in reducing the scour depth. The best configuration was found for a cable-pier diameter ratio of 0.15 and thread angle of 15°, in which the scour depth in upstream[E1] of the pier reduced to about 53%. In the case of a pier protected with cable and collar the scouring postponed more than pier protected with collar and the rate of scouring is less than in pier protected with collar. These advantages can reduce the risk of pier failure when the duration of flood is short. The results indicate that the scour reduction increases as the cable diameter increased and the thread angle decreased.