1. Sedimentation to Consolidation
2009 Sediment Transport Symposium
Cohesive sediment dynamics under water wave
Sedimentation to Consolidation
Wen-Yang Hsu, Hwung-Hweng Hwung, Ray-Yeng Yang, Igor V. Shugan
Tainan Hydraulics Laboratory
National Cheng-Kung Univ.
Tainan, TAIWAN.

2. Outline Introduction Literature Review Sedimentation to consolidation
Summary and future work

3. Ch. 1 Introduction Motivation Problem Identification Objectives
Literature Review
Sedimentation to consolidation
Summary and future work

4. Motivation Fundamental Researches:
Cohesive Sediment Dynamics in Marine Environment
Fundamental Researches:
Wave-mud interaction, fine sediment transport
Engineering Problems:
Coastal protection, land reclamation, dredging of deepwater navigational channels, water quality management and military application.

5. Problem Identification (1/2)
2002, Fine sediment dynamics in the marine environment
CBS: concentrated benthic suspension

6. Problem Identification (2/2)
Sedimentation to Consolidation
Dynamic response of fluid mud layer

7. Objectives Sedimentation Consolidation
Settling function, transition region, dispersion effects
Consolidation
Effective stress, temporal variation of interface

8. Ch. 2 Introduction Literature Review Sedimentation to consolidation
Properties of mud
Sedimentation and consolidation
Wave-mud interaction
Sedimentation to consolidation
Summary and future work

9. Properties of mud Bio-physical-chemical Properties
Composition: clay, silt, water, organic and inorganic maters
Size: smaller than 63 μm ( clay <4 μm , silt <63μm)
Structure: fragile, non-spherical
Molecular Electrons: attractive force and repulsive force
Brady, N.C. and R.R. Weil, 1999, The nature and properties of soil, Prentice-Hall,Upper Saddel River, NJ
Kaolinite
Illite, Chlorite

10. Behavior of mud
Plasticity: is the ability of a clay mass to undergo deformation before breaking.
Cohesion: is the ability of a material to stick or adhere together.
Flocculation: occurs when two particles collide and stick together and effected by three agents:
Brown Motion (Dyer, 1986)
Turbulent Shear (Hunt, 1986)
Differential Settling (Van Leussen, 1994)

11. Sedimentation

12. Sedimentation (1/3) Kynch(1952):
Assume that the settling velocity depends only on the local concentration.
ws=ws0 f(C)

13. Sedimentation (2/3) Owen (1976) Milkkelsen(2001)
Settling column
Milkkelsen(2001)
Laser In Situ Scattering and Transmissometry
Fennesy(1994)
Measurement of size floc by taking picture in a dilute suspension
Point out these drawbacks

14. Sedimentation (3/3) Fugate (2002)
Vertical 1-D equation of conservation of sediment
mass in the water column
Steady state at slack tides at a fixed point
Similarity of Fick’s law
Balance between gravitational settling and diffusive dispersion

15. Consolidation (1/2)

16. Consolidation (2/2) Hight (1987):
Transition point between suspension and soil

17. Ch. 3 Introduction Literature Review Sedimentation to consolidation
Bed material test
Settling behavior
Consolidation Process
Dynamic response of fluid mud
Summary and future work

18. Bed Material Test Selection of sediments Kaolinite, 6180, 211…
Size distribution and specific density
d50, dry density
Rheological property
Viscosity, yield stress, creep behavior
Composition analysis
By X-Ray analysis

19. Preliminary Result Clay(<4um): 28 % Silt(4~63um): 67 %
Fine sand (125~250um): 5%
D50=10.8um
Clay components (<2um)
Kaolinite (69%), Illite (30%)
with a small fraction of SiO2
Slope: viscosity
Inflection point: yield stress

20. Settling behavior
From gravitational settling to hindered settling
Discuss significant factors which would change the floc size, density, and then, settling velocity.
Establish settling function as a background information.

21. Experimental Setup

22. Experiment Focus Kaolinite, 6180 at fresh water and salt water
Different sediment and ambient water condition
Kaolinite, 6180 at fresh water and salt water
Range of concentration
100mg/L~20000mg/L (intense data around transition region)
Diffusive dispersion effect and mechanisms of shock waves
The relations between diffusion and no-shock waves
ABS and ADV calibration for converting backscatter signal to SSC
Measurement of settling velocity
Tracing shock wave, mass conservation, ADV approach

23. Preliminary Results

24. From settling to consolidation process
Formation of lutocline, fluid mud and consolidating bed
Transition region between sedimentation and solid bottom will be major subject.
Time function, distribution of concentration and stress should be important background for mud motion

25. Experimental Setup
Initial SSC would start from 1000 mg/L~100000mg/L

26. Preliminary Results
ABS Data
Backscatter

27. Backscatter

29. Expected Results Sedimentation
Settling function, effect of salinity and shock wave mechanism
Consolidation
Consolidation function, response of effective stress

30. Thank You! Please Comment
Team:
H.-H. Hwung (Principal Investigator)
J. P.-Y. Maa I. V. Shugan
R.-Y. Yang C.-M. Liu
H.-C. Hsu Y. Chang
W.-Y. Hsu H.-L. Wu
Thank you! Please Comment

31. Thank You
Please Comment

34. Ch. 4 Introduction Literature Review Sedimentation to consolidation
Dynamic response of fluid mud
Summary and future work

35. Dynamic response of fluid mud
Energy transformation and energy dissipation due to wave-mud interaction
Dynamic response of pressure, concentration, velocity and rheology property in mud layer.
Occurrence of resonance

36. Experimental Setup

37. Preliminary Results