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The influence of clay on the threshold of movement of fine sandy beds

The influence of clay on the threshold of movement of fine sandy beds
The influence of clay on the threshold of movement of fine sandy beds
The erosion threshold (i.e. surface shear strength) of mixed sediment deposits has been tested under the action of unidirectional currents (mean critical speeds, 4 mm above the bed, ranging from 12.4 cm s?1 to 18.2 cm s?1) or simulated waves (mean critical periods ranging from 2.0 s to 6.7 s, for near-bed wave amplitudes of 0.28–0.57 m) using an oscillating tray in a rectangular recirculating flume. The sediment mixtures investigated consisted of angular fine-grained quartz sands (D50 = 152.5 and 215 ?m) and cohesive estuarine mud. The investigation has shown that the cohesive material increases generally the erosion threshold of sandy deposits. The rate of increase is smaller for mud contents < 30% (clay mineral content < 11–14%, by dry weight) and is attributed to an increase of the internal angle of friction. When the clay mineral content exceeds 11–14% by dry weight, then the sand particles are not in contact with each other. Consequently, the clay component controls the erodibility of the sediment mixture. Finally, a prolonged and intense stress history can increase considerably (by a factor of 1.3–1.7) the original erosion threshold value of these sediments.
sand, clay, flume-studies, erodibility, critical-flow, steady-flow, unsteady-flow
0378-3839
19-43
Panagiotopoulos, I.
bd73f82a-86a9-408e-aa60-094c936aa153
Voulgaris, G.
c695d93c-1092-4223-b02a-6c1fc5fcb45c
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351
Panagiotopoulos, I.
bd73f82a-86a9-408e-aa60-094c936aa153
Voulgaris, G.
c695d93c-1092-4223-b02a-6c1fc5fcb45c
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351

Panagiotopoulos, I., Voulgaris, G. and Collins, M.B. (1997) The influence of clay on the threshold of movement of fine sandy beds. Coastal Engineering, 32 (1), 19-43. (doi:10.1016/S0378-3839(97)00013-6).

Record type: Article

Abstract

The erosion threshold (i.e. surface shear strength) of mixed sediment deposits has been tested under the action of unidirectional currents (mean critical speeds, 4 mm above the bed, ranging from 12.4 cm s?1 to 18.2 cm s?1) or simulated waves (mean critical periods ranging from 2.0 s to 6.7 s, for near-bed wave amplitudes of 0.28–0.57 m) using an oscillating tray in a rectangular recirculating flume. The sediment mixtures investigated consisted of angular fine-grained quartz sands (D50 = 152.5 and 215 ?m) and cohesive estuarine mud. The investigation has shown that the cohesive material increases generally the erosion threshold of sandy deposits. The rate of increase is smaller for mud contents < 30% (clay mineral content < 11–14%, by dry weight) and is attributed to an increase of the internal angle of friction. When the clay mineral content exceeds 11–14% by dry weight, then the sand particles are not in contact with each other. Consequently, the clay component controls the erodibility of the sediment mixture. Finally, a prolonged and intense stress history can increase considerably (by a factor of 1.3–1.7) the original erosion threshold value of these sediments.

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More information

Published date: October 1997
Additional Information: Deposted by Jane Conquer.
Keywords: sand, clay, flume-studies, erodibility, critical-flow, steady-flow, unsteady-flow

Identifiers

Local EPrints ID: 72274
URI: http://eprints.soton.ac.uk/id/eprint/72274
ISSN: 0378-3839
PURE UUID: 0d4f1ebb-3f84-40e8-bccf-a7eeeea7b782

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Date deposited: 04 Feb 2010
Last modified: 13 Mar 2024 21:22

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Contributors

Author: I. Panagiotopoulos
Author: G. Voulgaris
Author: M.B. Collins

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