تاثير تجمع زباله بر عملكرد طوقه در آبشستگي موضعي پايه پل استوانه‌اي

Local scour around bridge piers is one of the most important factors threatening the stability of these structures, an‎d the use of collars is known as an effective method to reduce it. On the other han‎d, the accumulation of floating debris upstream of the pier can change the flow pattern an‎d increase the scour depth. In this study, the effect of debris accumulation on collar performance in local scouring of cylindrical bridge pier was investigated experimentally. The experiments were conducted in a flume 15 m long an‎d 90 cm wide, with a cylindrical base with a diameter of 5 cm an‎d a circular collar with a diameter of 12.5 cm (2.5 times the diameter of the base) in limpid water conditions. The bed was prepared from uniform san‎d with an average diameter of 0.78 mm an‎d a flow velocity to critical velocity ratio of 0.93. The debris was installed in three shapes: cylindrical, inverted semi-pyramid, an‎d triangular, each in two sizes, large an‎d small, at the water surface level an‎d tangent to the front of the base. The results showed that the installation of the collar in a l debris-free condition reduced the scour depth by 35.2% compared to the control pier. However, debris accumulation disrupted the performance of the collar an‎d reduced its efficiency. Larger cylindrical debris had the highest negative impact with 25.4 percent, an‎d small cylindrical debris had the lowest negative impact with 40.3 percent. The study of the bed topography also showed that even in the worst conditions of debris accumulation, the use of a collar reduces the dimensions of the scour hole in the abutment, side an‎d back of it by 28.9, 45.4 an‎d 37.1 percent, respectively, compared to the control abutment. These findings highlight the need to pay attention to the phenomenon of debris accumulation in the design an‎d eva‎luation of bridge abutment protection systems.

منوچهر حيدرپوراسفرجاني

ميرمحمد صادقي

محمد شايان نژاد , مرتضي صادقي