Experimental Investigation of the Effect of Bed’s Coarse Grain Sediments on the Critical Shear Stress for Deposition of Suspended Sediments

Document Type : Research Article


1 Water Engineering Department, Ferdowsi University of Mashhad/ Mashhad, Iran

2 Water Engineering Department, Ferdowsi University of Mashhad

3 دانشگاه شهرکرد


The importance of sediments studies for safety design of hydraulic structures has been drawn attention by river engineers. Determining the critical shear stress for suspended sediment is of highly significant in sediment hydraulics. Therefore in this research, the deposition process of suspended sediment in the presence of bed sediment has been investigated. Deposition experiments were carried out in the circular flume for three values of shear stress, six types of beds (smooth bed and five coarse[1]grained sediments) with initial concentrations of 5, 10 and 20 g/l. The results showed that, for the same initial concentration and equal velocity of flume rotation, the deposition of suspended sediments in the bed containing sediments is higher than that of the smooth bed. However, for specific flume rotation velocity, the bed coarse-grained increased the average of flow shear stresses. It was also found that bed sediments generally increased the critical shear stress for all deposition relative to the smooth bed. Accordingly, it can be explained that in the bed with coarse grain sediments, in the flow with bigger turbulence, full deposition conditions for suspended sediments still exist. The results of this study showed for threshold critical shear stress in a smooth bed, for shear stress of less than 1.28 N/m2, sediments are in the state of the deposition threshold, but for bed containing coarse grain sediment was observed in which the suspended sediments was deposited in each flow shear stress and trapped among bed sediments. Also, it can be stated that due to the phenomenon of trapping suspended sediments in the bed containing coarse grain sediments, cannot be considered threshold critical shear stress for deposition of suspended sediments.


Main Subjects

[1] E. Partheniades, Cohesive Sediments in Open Channels, Elsevier Inc,Burligton, USA, (2009).
[2] J. Huang, R.C. Hilldate, B.P. Greiman, Erosion and sedimentation manual, in, U.S. Department of the interior. United States Bureau of Reclamation, (2006).
[3] Droppo IG, D’Andrea L, Krishnappan BG, Jaskot C, Trapp B, Basuvaraj M, Liss SN, Fine-sediment dynamics: towards an improved understanding of sediment erosion and transport, in: Journal of Soil Sediment (2015), 15:467–479.
[4] R.B. Krone, Flume Studies of the Transport of Sediment in Estuarial Shoaling Processes,, Technical Report, Hydraulic Engineering Laboratory, University of California, Berkeley California., (1962).
[5] A.J. Mehta, E. Partheniades, Depositional Behavior of Cohesive Sediments, Univ. of Florida, Gainesville, Florida, (1973).
[6] A.J. Mehta, E. Partheniades, Depositional Behavior of Cohesive Sediments, Univ. of Florida, Gainesville, Florida, (1973).
[7] J.P. Maa, J. Kwon, K. Hwang, H.K. Ha, Critical bed shear stress for cohesive sediment deposition under steady flows, Journal of Hydraulic Enigineering (ASCE), 134(12), (2008), pp 5.
[8] D. Milburna, B.G. Krishnappan, Modelling Erosion and Deposition of Cohesive Sediments from Hay River, Northwest Territories, Canada, in:  13’ Northern Res. Basins/Workshop, Nordic Hydrology, Territories, Canada, (2001), pp. 14.
[9] B.G. Krishnappan, R. Stephens, Critical shear stresses for erosion and deposition of fine suspended sediment from the Athabasca River, Northern River Basins Study Project, (1996).
[10] M. Khastar-Boroujeni, K. Esmaili, H. Samadi-Boroujeni, A. Ziaei, Wastewater Effect on the Deposition of Cohesive Sediment, Journal of Environmental Engineering, ASCE, (2018).
[11] H. Samadi- Boroujeni, M. Khastar Boroujeni, R. Fatahi Nafchi, M. Ghasemi, M. Heidari, Experimental Study on suspended sediment deposition process in Karkheh dam reservoir, Amirkabir Journal of Civil Engineering, (2018).
[12] N. Vojdani, M. Ghomshi, Erosion critical shear stress of cohesive sediment and its role in the design of open channels, in: national conference on irrigation
and dranage network management, Sh Chamran
University, (2006).
[13] W.I. Ford, J.F. Fox, Model of particulate organic carbon transport, in an 431 agriculturally impacted stream,. Hydrological Processes, (2014), 28(3), 662-675.
[14] B.G. Krishnappan, P. Engel, Entrapment of fines in coarse sediment beds, River Flow Ferreira, Alves, Leal and Cardoso (eds). Taylor and Francis Group, London, (2006), 817–824.
[15] D. Huston, J. Fox, Clogging of fine sediment within gravel substrates: dimensional analysis and macroanalysis of experiments in hydraulic flumes, in Journal of Hydraulic Engineering, (2015), 141:04015015.
[16] K. Glasgerben, M. Stone, B. Krishnappan, J. Dixon, U. Silins, The effect of coarse gravel on cohesive sediment entrapment in an annular flume, in:  Proceedings of the International Association of Hydrological Sciences (2015), pp. 5.
[17] E. Partheniades, J. G.Kennedy, Deposition behavior of fine sediment in a turbulent fluid motion, Proc., 10th Int. Conf. on Coastal Engineering, Tokyo, (1966), pp.707–724.
[18] E.Partheniades, R.H. Cross, A. Ayora, Further research on the deposition of cohesive sediments, in Proceedings of the 11th Conference on Coastal Engineering, (1968), pp. 723–772.