» Research Note « Experimental Study on Settling Velocity Changes of Cohesive Sediments using Settling Column

Document Type : Technical Note

Authors

1 Associate Professor, Water Resources Research Center, Shahrekord University, Shahrekord, Iran

2 M.Sc. Graduate Student, Water Engineering Department, Faculty of Agricultural, Shahrekord University, Shahrekord, Iran

3 Professor, Faculty of Water Engineering, Shahid Chamran University, Ahvaz, Iran

4 Graduated M.Sc. Student, Civil Engineering Department, Faculty of Islamic Azad University, Tehran, Iran

Abstract

In this study, the settling velocity of cohesive sediments in a state of rest was investigated by performing experiments in a cylindrical plexiglass column with an internal diameter of 19 cm and a height of 300 cm. The experiments were carried out with 5 initial concentrations of 3, 5, 10, 15 and 20 g/l, and measurements of sediment concentration were measured at different times from 5 to 480 minutes after starting of sedimentation process. Also sediment concentration was measured by sampling from valves at 20 cm depth intervals in the model. To calculate the settling velocity of the sediment, a differential equation was used which had been proposed by Mclauglin (1959). The results show that the Mclauglin's equation is capable of describing the behavior of cohesive sediment deposition at rest state. In all experiments, the maximum settling velocity of sediment occurred at time of 15 minutes after the starting of the sedimentation process because of maximum flocculation forming. This was in agreement with the results of other researchers. By increasing the initial concentration in the experiments, the settling velocity of sediments decreased. The maximum settling velocity was measured for initial concentration of 3 g/l, and was equal to 5.84 mm/s. The minimum settling velocity was related to the initial concentration of 20 g/l, and was equal to 2.13 mm/s.

Keywords


Cancio L. and Neves R. (1995). "Three dimentional  model system for baroclinic estuarine dynamics and suspended sediment transport in a mesotidal estuary". Computational Mechanics Publications, 11: 353-360.
Cancio L. and Neves R. (1999). "Hydrodynamics  and sediment suspension modelling in stuarine system". Journal of Marine Systems, 22: 105-116.
Fathi-Moghadam, M., A. Arman, H. Samadi-Boroujeni and S. Emamgholizadeh, (2009), "Fall velocity of cohesive sediments in Dez dam reservoir", Research Journal of Environmental Sciences, 3(1): 71-79.
Krone R. B. (1963). "A study of rheologic properties of estuarial sediment". Hyde. Eng. Lab. And Soni. Eng. Lab. Univ. of California, Berkeley, No. 63-38.
Lau Y. L. and Kkrishnappen B. G. (1992). "Size distribution and settling velocity of cohesive sediments during settling". Journal of Hydraulic Research, 30(5): 673-684.
Mehta A.J. and Partheniades E. (1979). "Kaolinite resuspension properties". Tech. Note. Proc ASCE, 105: 164-177.
Mclauglin RT. (1959). "Settling properties of suspensions". Proc. ASCE.HY12. Paper 2311. 85 :9-41.
Nicholas J. and O Connor B. A. (1986). "Cohesive sediment transport model". Journal of Hydraulic Engineering. - 112(7): 621-640.
Samadi-Boroujeni, H., M. Fathi-oghaddam, M. Shafaie-Bajestan and H. Mohammad. Vali. Saman, (2005), "Modelling of sedimentation and self-weight consolidation of cohesive sediments", Sediment and Ecohydraulics Intercoh2005. 1st Edn. Elsevier B.V.Oxford, UK, ISBN: 978-444-53184-1. pp. 165-191
Sanford, L., Dickhudt, P.J., Rubiano-Gomez, L., Yates, M., Suttles, S.E., Friedrichs, C.T., Fugate, D.D., and Romine, H., (2005), "Variability of suspended particle concentrations, sizes, and settling velocities in the Chesapeake Bay turbidity maximum. In: Droppo, I.G., Leppard, G.G., Liss, S.N., and Milligan, T.G. (eds.), Flocculation in Natural and Engineered Environment Systems". CRC Press, Washington D.C., pp. 211–356.
Scully, R.W., Shiffman, R.L., Olsen, H.W. and Ko, H.Y., (1984), "Validation of consolidation properties of phosphatic clay at very high void ratios", ASCE
Symposium on Sedimentation/ Consolidation Models, San Francisco.
Shin,H.J., M. Son and G. Lee, (2015). "Stochastic flocculation model for cohesive sediment suspended in water". Water 2015, 7, 2527-2541; doi:10.3390/w7052527
Spicer, P.T., Pratsinis, S.E., Raper, J., Amal, R., Bushell, G. and Meesters, G. (1998). "Effect of shear schedule on particle size, density, and structure during flocculation in stirred tanks". Powder Tech., 97, 26–34.
Thorne J.A. Grace E. Swift  D.J.P and Niedoroda A. (1991). "The depositional fabric and analytical approach to stratification and facies identification sedimentation on continental margins in shel sand and sandstone bodies". Special Publication 14, International Association of Sedimentologists. Blackwell Scientific Publications, Oxford, pp. 59–87.
Toorman E. (1992). "Modelling of fluid mud flow and consolidation". Ph.D Thesis, Hydraul. Lab., Katholieke Univ. Leuven, Belgium.
Yamagami T., Ueno K. and Sakai, S., (2000), "Back analysis for determination of sedimentation and consolidation properties", Coastal Geotechnical Engineering in Practice, Nakase and Tsuchida (eds) Balkema, Rotterdam, ISBN.
  • Receive Date: 18 August 2017
  • Revise Date: 19 October 2017
  • Accept Date: 24 October 2017
  • First Publish Date: 21 January 2018