Experimental Study for Protection of Piers Against Local Scour Using Slots


Department of Civil Engineering, University of Basrah, Basrah, Iraq


The most important causes of bridge failure are local scour. In this study, laboratory experiments were conducted to investigate the effectiveness of slot as a protection device in reduction of depth of scour at cylindrical piers under clear water flow conditions. The development time of scour depth at the circular pier with and without a slot as a protection device was conducted. The experiments focused on the effect of using different lengths of slot, calculating efficiency and deriving a suitable equation. It was observed that the scour depth decreases as the size of slot length increases; and also the maximum reduction in scour depth equals to 49%. The technique of dimensional analysis was used, and based on laboratory results an empirical formula was derived by using IBM SPSS statistics v24 software. The coefficient of determination (R²) was determined to be (0.961), There was a good agreement between the predicated and observed data.


1.     Wang, C., Yu, X., Liang, F., A review of bridge scour: mechanism, estimation, monitoring and countermeasures. Natural Hazards, Vol. 87, No. 3 (2017) 1881-1906. doi:10.1007/s11069-017-2842-2.

2.     Chiew, Y. M., Melville, B. W., Local scour around bridge piers. Journal of Hydraulic Research, Vol. 25, (1987), 15–26.

3.     Parker, G., Toro-Escobar, C., Voigt, R.L., Countermeasures to protect bridge piers from scour. Final Report NCHRP Project 24–7. Transportation Research Board, Washington, DC, (1998).

4.     Lagasse, P. F., Clopper, P. E., Zevenbergen, L. W. and Girard, L. G., Countermeasures to protect bridge piers from scour. National Cooperative Highway Research Program (NCHRP) Rep. No. 593, Transportation Research Board, Washington, D.C., (2007).

5.     Abd El-Razek, M., Abd El-Motaleb, M., Bayoumy, M., Scour reduction around bridge piers using internal openings through the pier. Proc. 30th IAHR Congress, Thessaloniki, C2, (2003), 285–292.

6.     Haque, M.A., Rahman, M.M., Islam, G.M.T., Hussain, M.A., Scour mitigation at bridge piers using sacrificial piles. International Journal of Sediment Research, Vol.  22, No. 1, (2007), 49–59.

7.     Razi, S., Salmasi, F., Hosseinzadeh Dalir A., and Farsadizaeh, D.: Application of Bed Sill to Control Scouring Around Cylindrical Bridge Piers. Journal of Civil Engineering and Urbanism, Vol. 2, (2011), 115-121.

8.     Grimaldi, C., Gaudio, R., Calomino, F., and Cardoso, A. H.: Countermeasures Against Local Scouring at Bridge Piers: Slot and Combined System of Slot and Bed Sill. Journal of Hydraulic Engineering, Vol. 135, No. 5, (2009b), 425-431.

9.     Tafarojnoruz, A., Gaudio, R., and Calomino, F., Evaluation of Flow-Altering Countermeasures against Bridge Pier Scour.  Journal of Hydraulic Engineering, Vol. 138, No. 3, (2012).

10.   Raudkivi, A. J., Functional trends of scour at bridge piers. Journal of Hydraulic Engineering, Vol. 112, No. 1, (1986), 1-13.

11.   Dargahi, B.: Controlling mechanism of local scouring. Journal of Hydraulic Engineering, Vol. 116, No. 10, (1990), 1197-1214.

12.   Dey, S. Bose, S. K. and Sastry, G. L. N., Clear water scour at circular piers: A model. Journal of Hydraulic Engineering, Vol. 121, No. 12, (1995), 869-876.

13.   Dey, S. and Raikar, R. V., Characteristics of horseshoe vortex in developing scour holes at pier. Journal of Hydraulic Engineering, Vol. 133, No. 4, (2007), 399-413.

14.   Afzali, S. H., New Model for Determining Local Scour Depth Around Piers. Arabian Journal for Science and Engineering, vol. 41, No. 10, (2016), 3807-3815.

15.   Tanaka, S. and Yano, M., Local scour around a circular cylinder. Proc., 12th IAHR Congress, Delft, The Netherlands, 3, (1967), 193-201.

16.   Muzzammil, M., T. Gangadharaiah, and A. K. Gupta. "An experimental investigation of a horseshoe vortex induced by a bridge pier." In Proceedings of the Institution of Civil Engineers-Water Management, Vol. 157, No. 2, 109-119. Thomas Telford Ltd, 2004.

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

18.   Jahangirzadeh A., Basser H., Akib S., Karami H., Naji S., Shamshirband S., Experimental and Numerical Investigation of the Effect of Different Shapes of Collars on the Reduction of Scour around a Single Bridge Pier. PLoS One Vol. 9, No. 6: e98592 (2014). doi: 10.1371/journal.pone.0098592

19.   Melville, B.W. and Sutherland, A.J., Design Method for Local Scour at Bridge Piers. Journal of Hydraulic Engineering, Vol.114, No.10, (1988), 1210-1226.

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

21.   Hoffmans, G.J.C.M. and Verheij, H.J., Scour manual. A.A. Balkema, Rotterdam, The Netherlands, (1997).

22.   Chiew, Y.M., Scour protection at bridge piers. Journal of Hydraulic Engineering, ASCE, Vol. 118, No. 9, (1992), 1260-1269.

23.   Melville, B.W., Pier and Abutment Scour: Integrated Approach. Journal of Hydraulic Engineering, Vol. 123, No. 2, (1997), 125-136.

24.   Ettema, R., Scour at bridge piers. PhD Thesis, Auckland University, Auckland, New Zealand, (1980).