Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries Report and Symposium Proceedings (1987) / Chapter Skim
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Session B: Modifying Existing Facilities
Session B: Modifying Existing Facilities
Pages 127-176
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From page 129... ...
Collisions due to thermal motions and differential settling velocities create loose, weak aggregates that are easily dispersed in velocity gradients. Velocity gradient aggregation, however, produces denser, stronger aggregates that will resist at least the velocity gradient under which they were forged.
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From page 134... ...
With this wall in place, currents In the model immediately adjacent to the face of the wharf were twice those that occurred with the blunt end, increasing the bed shear stress by a factor of four.
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From page 138... ...
These remarks should not be construed to mean that there are always feasible remedies. We all know of examples that indicate the only way to significantly reduce maintenance dredging costs is to relocate the facility.
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From page 140... ...
1982. Resuspension potential of deposited cohesive sediment beds.
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From page 145... ...
A. . Carquinez Strait FIGURE 2 Plan view of Mare Island Strait and scour jet array test !
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From page 146... ...
'! ~-i.~.,\' 6 in discharge hose ~\ Prototype Whet array installed 17 Feb 77 at Mare Island Naval Shipyard FIGURE 3 Schematic diagram of 70-jet spatial scour jet array.
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From page 149... ...
. O ~ - - 1 O-in intake l 1= At> A test bed linear jet array was designed by the Naval Civil Engineering Laboratory to answer these questions.
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From page 150... ...
The test bed scour jet array system will be operated for three years beginning September 1986. SITING CRITERIA AND SYSTEM ECONOMICS The primary criterion for siting a scour jet array system is to place it where there is sufficient tidal circulation to carry the resuspended sediment away from the site.
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From page 151... ...
151 Ee ~ ~ I_ ._ ~ ._ ~ X O , Q C, o o o ._ He .= QCal \ Cal
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From page 152... ...
lid. A design for a test bed scour jet array for Mare Island naval Shipyard.
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From page 153... ...
give rise to vertical advection away from the bottom in opposition to the settling velocities of floes and aggregated fine sediments. The combined action of turbulent shear stresses to erode the bottom and vertical advection to flux mobilized sediments away from the bottom is accountable for a net erosion flux of about 23,000 me annually on the downstream side of this bridge.
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From page 154... ...
As the induced velocity field trailing an array of wings begins to decay downstream, a second array could be placed to resuspend the settling sediments mobilized by the first array. With cascades of wing arrays along a channel, it should be possible to keep fine sediments suspended until they have bypassed harbor areas and reached either the sea or channels where~strong natural currents maintain a sufficiently deep-scour ng channel.
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From page 155... ...
On the other hand, the cohesive sedimentary bed behaves as a viscoplastic with a yield stress. When an applied shear stress exceeds the yield stress, the cohesive bed will deform at a rate proportional to the difference between applied and yield stress.
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From page 156... ...
Therefore we shall define the fluid/sediment interface as that level Z ~ Zc where the bulk density has risen to some critical value Pc such that the resulting fluid/sediment slurry just begins to develop a yield stress ~ = sac that obeys the relation due to Miznot (1968) wherein T = EpB = ~ c E = p fA N q B = 2 mq (1)
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From page 158... ...
This of course is conditional on the presence of some applied stress in excess of the yield stress at Z = Zc The induced velocity field due to a lifting body placed a distance b/2 from a plane boundary is found by the method of images (Figure 5~. This problem is equivalent to the induced velocity of an unstaggered biplane solved by Prandtl (1919)
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From page 160... ...
Therefore, the circulation ~ developed by the wing section is the only remaining free parameter to maximize in order to achieve maximum erosion fluxes, since the induced velocity is a linear function of the circulation cob 2sr ()
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From page 162... ...
is the mixing length damping factor as a function of the sediment bulk density in the floe layer. Both akpf)
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From page 168... ...
... FIGURE 10 Completed upwashing wings prior to deployment at Mare Island Naval Shipyard.
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From page 169... ...
~ CONTROL AREA CONTROL AREA | I BASCULE HAIE ISL AND STRAIT I BRI00F VALLEJO STUDY AREA DETAIL COE ORE DGE CHANNEL LIIVE U EBe 0.5-1 0 KNOTS it ~COE ORE DGE CHANNEL LINE INST RUMENTATION ~ - CURRENT METER STRING · PRE SSURE SE VISOR -; - 4~W MOM E NT U M SURVE Y BOUNDARY I00 x 100 f 3 - 5 es. 20 ft SPAN FOILS SHIP CHANNEL -35 to -37 It MLLW FIGURE 11 Site plan for the wing experiments at Mare Island Naval Shipyard.
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From page 171... ...
171 it' : .
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From page 174... ...
We observe that the two spectra and time series are almost identical, despite what was admittedly a very coarse wake-rake of only three sensors. Estimating the depth of the salt wedge to be 5 m during this record, for which the mean current was 25 cm/see, it is concluded that each unit area of wing removes 2.9 percent of the salt wedge energy flux through a unit area of stream cross section.
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