Intro Cutter Suction Dredge

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Intro Cutter Suction Dredge
Prof. Dr. Ir. C. (Cees) van Rhee
D dgi g Engineering
Dredging
E gi
i g
Delft University of Technology
Contents
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Intro
General lay‐out
Working Method
Cutter head
Intro Cutting Theory (Sand and Rock)
Mixing in cutter – spillage
Operational Limits
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Components
Cutter SSuction D
Cutter uction Dredger
redgerss
Small < 250 kW
• Pontoon
• Ladder
– Cutter head + drive system
– Suction line
S i li
– Support system + winch
• Spuds
• Pumps + discharge system
• Side wires + winches
Large > 2500 kW
Medium, 1500 kW
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Pump + suction line
service platform
service crane
stepping spud
working spud
control room
Ladder
Spud system
pontoon
ladder
Cutter head
main engine + pump room
anchor
booms
cutterhead
Side
wires
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main engine + pump room
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Working principle
anchor wire
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CSD Work Method (1)
Swing to starboard
• Cutter disintegrates or dislodges the material mechanically by rotating cutter head
• Swinging around working spud
Swinging around working spud
• Progress by successive steps
• Material sucked up and transported through pipeline by use of centrifugal dredge pumps
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CSD Work Method
(2)
CSD Work Method
(3)
Stop at starboard, push dredger forward
Start swing to portside
CSD Work Method (4)
Continue swing to portside
CSD Work Method
(5)
Stop at portside, push
dredger forward to next
starboard cut
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CSD Work Method
(6)
CSD Work Method
Start swing to
starboard
CSD Work Method
(8)
(7)
Stop in centre line
CSD Work Method
(9)
Auxiliairy spud is lowered
Main spud is hoisted up
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CSD Work Method
(10)
CSD Work Method
(11)
The spud‐carrier with the hoisted main spud is moved forward
Main spud is lowered
CSD Work Method
(12)
Auxiliairy spud is hoisted up
CSD Work Method
(13)
Dredger starts swinging / dredging
to starboard
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CSD Work Method
Under and over cutting
force balance
(14)
Side winch: breaking
Vert: pushing force needed
Side winch: pulling
Vert: lifting force needed
Ds
Ds
Continuation of starboard swing Over cutting mode
Under cutting mode
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Discharge Methods
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Discharge by pipeline
• Pipeline
• Barge loading
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Barge loading
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Cutter Head
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General Teeth systems
Cutting process
Mixing process
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Clay cutter
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Rock cutter
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• Movie
pen
punttand
borg
houder mes
houder vollas
snijtand
houder tweezijdige bevestiging
getand mes
beiteltand
'serrated' mes
houder enkel
glad mes
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Vosta
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Bucket wheels
Cutting Theory
Ellicott wheel
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Basic failure modes
Cutting in Sand
• Effect of pore pressure
Flow Type
Tear Type
Shear Type
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Forces on the blade
F=G tan(phi)
phi = friction angle
F
T
S
G tan(phi)
G
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Dilatancy
•Dilatancy explained
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Negative pore pressure
(under pressure)
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Forces on layer – effect of dilatancy
T=S’ tan(phi) Coulomb
S’=S‐u
u::v h/k
S’ : effective stress S : Total Stress
u : Pore water pressure
u pore pressure
h
i d h
h cutting depth
S 0 : S’=‐u

Pore water pressure is negative
Increase in effective stress
Increase in Shear stress
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v cutting velocity
k permeability
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Under and over cutting
force balance
Cutting Sand:
Side winch: breaking
Vert: pushing force needed
Side winch: pulling
Vert: lifting force needed
• Larger Cutting forces with
– Lower permeability (finer sand)
– Increase cutting depth & velocity
– Increase water depth
Increase water depth
Ds
Ds
Over cutting mode
Under cutting mode
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Failure modes during
Cutting
Rock Cutting
Chip
Tensile crack
Shear crack
Tool
Crushed zone
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Shear
h
zone
Shear plane
Plastic deformation
Brittle-ductile transition
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Forces during cutting
Rock cutting
• Large cutting forces
B r ittle & D u c tile C u ttin g
– Strength Cutter and teeth
– Teeth placement important
– Tooth wear
Tooth wear
120
100
Force
80
B r ittle
D u c tile
60
40
20
0
0
10
20
30
40
50
60
70
T im e
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Spillage
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Spillage Low cutter
Rev.
High cutter
Rev.
spill
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Cutter head production process
in rock or gravel
Cutter head productions c.q. Spillage
•The rotational speed of the cutter head causes spillage.
–Cutter acts as a pump
•The
The productivity c.q. spillage depends on the ratio:
productivity c.q. spillage depends on the ratio:
•For sand the productivity is:
Pr  2.5
Q pump
3
 Rcutter
•For rock the productivity is much lower
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Influence of waves on operation
Wave influence
• CSD is a floating object
• Response due to wave loading as with other floating structures, but ….
• CSD not only decisive
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– Aux. Equipment
– Coupling, de‐coupling of floating pipeline
– Typical geometry of pontoon with ladder
T i l
t
f
t
ith l dd
– Interaction with soil
• Spud – Spud carriage system
• Cutter head
• Numerical prediction still not satisfactory
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Application of CSD
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Limiting Factors
Nearly all kinds of soils (sand, clay, rock <30 MPa)
Sensitive to wave conditions
Stationary dredger (vulnerable for shipping)
Some are self‐propelled for mobilisation
Max. dredging depth 30 m
 Excavation
 Soil characteristics
 Available power on cutter
 Side winches (max. power and velocity)
 Thickness and width of the layer to be dredged
 Dredging depth (ladder angle, spuds, vacuum limit)
 Pumping distance (pump‐ and pump drive characteristics)
 Shipping
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???
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Next Webinar :
Intro Trailing Suction Hopper Dredge
• September 14 2016
• 14:00 – 15:00 CEST
17