Study on the Effect of Installation Depth of Pipe on Scour Depth Under the River Crossing Pipeline in Unsteady Flow

Document Type : Research Paper


1 M.Sc. In Water & Hydraulic Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

2 Professor, Department of WaterStructures, Shahid Chamran University of Ahvaz, Ahvaz, Iran.(

3 Assistant Professor, Department of WaterStructures, Shahid Chamran University of Ahvaz, Ahvaz, Iran.


Water and other fluid pipes that are placed on the seabed and rivers bed change the flow pattern around them. These changes increase the shear stress of the bed and the severity of turbulence around the pipe and create a scouring hole under the pipe. The scouring under the pipe may lead to instability, bending, and even breakage of the pipeline. In this study, local scouring around pipelines across the river in unsteady flow conditions was investigated. In the experiments, three pipe diameters (20, 40, and 60 mm) and three installation depths (on the bed, a quarter of the pipe diameter above the bed, and half of the pipe diameter above the bed) were used. It can be understood from the results of this laboratory study that the amount of final scour depth due to the passage of flood hydrograph is always less than the scour depth due to the steady flow corresponding to the peak flow of the hydrograph. For different pipe installation depths, the amount of scouring for the installation depth of one-quarter of the pipe diameter above the bed in both steady and unsteady flow conditions is higher than other installation depths.


Main Subjects

1-    Azamathulla, H.M., Yusoff, M.A.M. and Hasan, Z.A., 2014. Scour below submerged skewed pipeline. Journal of Hydrology509, pp.615-620.
1-    Chang, W.Y., Lai, J.S. and Yen, C.L., 2004. Evolution of scour depth at circular bridge piers. Journal of Hydraulic Engineering130(9), pp.905-913.
2-    Chiew, Y.M., 1991. Prediction of maximum scour depth at submarine pipelines. Journal of Hydraulic Engineering117(4), pp.452-466.
3-    Dey, S. and Singh, N.P., 2007. Clear-water scour depth below underwater pipelines. Journal of Hydro-Environment Research1(2), pp.157-162.
4-    Ghodsian, M., Moncada-M, A.T. and Aguirre-Pe, J., 2000. Scour below Pipeline in River Crossing. Journal of Hydraulic Engineering126(10), pp.793-793.
5-    Graf, W.H. and Suszka, L., 1985, August. Unsteady flow and its effect on sediment transport. In 21st IAHR congress (pp. 539-544).
6-    Griffiths, G.A. and Sutherland, A.J., 1977. Bedload transport by translation waves. Journal of the Hydraulics Division103(ASCE 13363 Proceeding).
7-    Tabarestani, M.K. and Zarrati, A.R., 2017. Local scour calculation around bridge pier during flood event. KSCE Journal of Civil Engineering21(4), pp.1462-1472.
8-    Kothyari, U.C., Garde, R.C.J. and Ranga Raju, K.G., 1992. Temporal variation of scour around circular bridge piers. Journal of Hydraulic Engineering118(8), pp.1091-1106.
9-    - Lee, K.T., Liu, Y.L. and Cheng, K.H., 2004. Experimental investigation of bedload transport processes under unsteady flow conditions. Hydrological processes18(13), pp.2439-2454.
10- Link, O., Castillo, C., Pizarro, A., Rojas, A., Ettmer, B., Escauriaza, C. and Manfreda, S., 2017. A model of bridge pier scour during flood waves. Journal of Hydraulic Research55(3), pp.310-323.
11- Lu, J.Y., Shi, Z.Z., Hong, J.H., Lee, J.J. and Raikar, R.V., 2011. Temporal variation of scour depth at nonuniform cylindrical piers. Journal of Hydraulic Engineering137(1), pp.45-56.
12- Maza, J.A., 1987. Introduction to river engineering. Advanced Course on Water Resources Management, Universita Italiana per Stranieri.
13- Oliveto, G. and Hager, W.H., 2002. Temporal evolution of clear-water pier and abutment scour. Journal of Hydraulic Engineering128(9), pp.811-820.
14-  Oliveto, G. and Hager, W.H., 2005. Further results to time-dependent local scour at bridge elements. Journal of Hydraulic Engineering131(2), pp.97-105.
15- Sumer, B.M. and Fredsoe, J., 1991, January. Onset of scour below a pipeline exposed to waves. In The First International Offshore and Polar Engineering Conference. International Society of Offshore and Polar Engineers.
16- Sumer, B.M., 2002. The mechanics of scour in the marine environment. World Scientific.
17- Wu, Y. and Chiew, Y.M., 2013. Mechanics of three-dimensional pipeline scour in unidirectional steady current. Journal of Pipeline Systems Engineering and Practice4(1), pp.3-10.
18- Zhao, M., Vaidya, S., Zhang, Q. and Cheng, L., 2015. Local scour around two pipelines in tandem in steady current. Coastal Engineering98, pp.1-15.
Volume 43, Issue 4
March 2021
Pages 117-128
  • Receive Date: 26 December 2020
  • Revise Date: 09 January 2021
  • Accept Date: 26 January 2021
  • Publish Date: 21 December 2020