Control of local scour by symmetrical and asymmetrical collar around the bridge pier in river bend

Subject Areas : Marine structures

پریسیما عباسی ¹ , علیرضا مسجدی ² , محمد حیدرنژاد ³

1 -
2 -
3 -

Received: 2020-11-14 Accepted : 2021-07-05 Published : 2021-07-11

Keywords: Scour, 180 degree bend, قوس 180 درجه, Relative collar length, cylindrical base, طول نسبی طوقه, آب‌شستگی, پایه استوانه‌ای,

Abstract :

Scouring around the bridge piers is one of the main reasons for the destruction of bridges. One of the methods to reduce scouring around the bridge piers is installing a protective collar on the base. For this purpose, to investigate the effect of the collar, a series of experiments in a laboratory flume with an bend of 180 degrees and a central radius of 2.8 meters and a width of 0.6 meters with R / B = 4 was made of Plexiglas. In this research, by placing a base with a diameter of 5 cm with different collars of relative length upstream and downstream 0.4, 0.6, 0.8 and 1 in the position of 70 ° bend with a constant flow of 16 liters Per second and a constant depth of 10 cm. The scouring phenomenon around the base in the state of clear water was investigated. Natural sand with uniform granulation with Dm = 2 mm and uniformity coefficient of 1.8 was used for canal floor. The results of this study showed. Increasing the relative length of the collar upstream and downstream significantly reduces the amount of local scour around the base and also the highest and lowest percentage of reduction in scour depth around the collar with the relative length of upstream and downstream, respectively, 68 and 12 has been achieved.

References:

صفرزاده، گندشمین، ا، (1383) شبیه سازی الگوی جریان در آبگیری جانبی از قوس 180 درجه ، پایان نامه کارشناسی ارشد ، دانشگاه تربیت مدرس.

Breusers, H.N.C., Nicollet, G. and Shen, H.W. (1977). Local scour around cylindrical piers. Journal of Hydraulic Research, 15(3): 211-252.

Chiew, Y.M. and Melville, B.W.(1987). Local Scour Around Bridge Piers. Journal of Hydraulic Research, Vol. 25, No. 1, pp. 15-26.

Chiew,Y.M. (1992). Scour Protection at Bridge Piers. JHE, ASCE, Vol. 118, No.9, ppl 260-1269.

Kumar, V., Ranga Raju, K.G. and Vittal, N.(1999). Reduction of local scour around bridge piers using slots and collars. Journal of Hydraulic Engineering, ASCE, 125(12): 1302-1305.

Raudkivi, A.J. and Ettema, R. (1983). Clear-Water Scour at Cylindrical Piers. Journal of Hydraulic Engineering, ASCE, 109(3).

Raudkivi, A.J. (1998). Loose boundary hydraulics. 4th Edition. Rotterdam ; Brookfield, VT : Balkema. 496 p.

Richardson, E.V., Davies, S.R. (1995). Evaluating scour at bridges. Report. No FHWAIP- 90-017 (HEC 18), Federal Administration, U.S. Department of Transportation, Washington, D.C.

Singh,C.P.,Setia,B. and Verma, D.V.S. (2001). Collar-sleeve combination as a scour protection device around a circular pier. Proceedings of Theme D, 29th Congress on Hydraulics of Rivers,Water Works and Machinery,Chinese Hydraulic Engineering Society, Beijing, China. September 16-21,202-209.

Zarrati, A.M., Nazariha, M. and Mashahir, M.B. (2006). Reduction of local scour in the vicinity of bridge pier groups using collars and riprap. Journal of Hydraulic Engineering, ASCE, 132(2): 154-162.