hydraulic dredging: horizontal transport. part 1: transpot

Bernard Malherbe - Dredging Technology: horizontal transport of mixtures 1

UNIVERSIDAD DE GRAN CANARIADredging Technology

Ir. Bernard MalherbeProject Development DirectorJan De Nul Group

Hydraulic Dredging: horizontal transportPart 1: Transport of dredged mixtures

trough pipes (2009/2010)


Why Dredging ?

Scope of Works of Dredging:

– Realize or Improve or Maintain Nautical Accessibility for Ships to Ports, Fairways,…: CapitalDredging and Maintenance Dredging

– Reclaim New Land for housing, industrial development– Coastal Protection: restaure beach & dune system, dykes,..– Seabed preparation for offshore infrastructures : pipelines, cables, GBS platforms, scour-protection,

windmill-farms,…– Morphological compensations linked to maritime works– Sanitation of contaminated sediments


Figure 1-4:Evolution of Maximum Size of Maritime Vessel

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

1930 1940 1950 1960 1970 1980 1990 2000 2010

Year into Operation

DW

T C

arry

ing

Cap

acity

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Bulkcarriers DWT Container Carriers TEU

ECONOMY OF SCALE : EVER INCREASING SHIP’S SIZES


Annual Maintenance Dredging vs Anual Cargo Troughput

36.6 59.7Lisboa

Nant es St Nazaire

Bordeaux

Hamburg

Ant werp

Rot t erdam

Zeebrugge

Hai Phong

Bremen&Bremerhaf en

0

5

10

15

20

25

0 50 100 150 200 250 300 350

Cargo Troughput (Mt/year)

ANNUAL MAINTENANCE DREDGING CAN BE A SIGNIFICANT COST-ITEM IN THE OVERALL PORT’S

ECONOMIC BALANCE


Dredging & Reclamation: itDredging & Reclamation: it ’’s all about soil and dredgerss all about soil and dredgers

The CSD “JFJ De Nul”cutter dredger with worldstlargest cutter-power


Dredging equipment: Hydraulic dredgers: Trailing Suction Hopper Dredger (TSHD)

Cutter Suction Dredger (CSD)Mechanical dredgers: Backhoe Dredger (BHD)

BHDCSDTSHD


Evolution of Cutter Suction Dredging FleetEvolution of Cutter Suction Dredging Fleet

CSD ‘Leonardo da Vinci’

CSD ‘Ortelius’


Evolution of Trailing Suction Hopper Dredging FleetEvolution of Trailing Suction Hopper Dredging Fleet

'C s::

Evolution of Trailing Suction Hopper Dredgers: Jan De Nul Fleet

5oooo ,--------------------------------------------------------------------------,25o

~OOO+----------------------------j~~~~~~~3!~

40000+----------------------------------- ----------~"'---I-__+ 200

~ 35000+-------------------------------------~= E

M = S 30000+-------------------------------------------------------~~~----~--~=--+150! ~ O ~ ~ s:: g. 25000 "51 o ~ ~ e "~ 20000 100 § 5 E "¡¡¡

~ 15000 ~ a. ~

10000 --~~~"'-------------------------------------------------+50

5000 ~~~~;;~~~::::::~----------------------------------------------_J O+-------~------_.------_,--------._------,_------~------_,------_.--------,_------+O

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Year

I - Hopper Capacity 1m3) - Vessel Length LOA (m) - Maximum Dredging Depth 1m)

tq:pr ...... ', -, -~ ~,.".-... ~ ..... 1fM9I"II

s ... ""pipo:_

........ -........ --~. lWI ... l_....¡


Dredging Tools: mechanical rupture of cohesion of soil + hydraulic jetting & erosion-transport

3 methods

BucketCutterheadDraghead

BHDCSDTSHD


Soil-cutting tools

Cutterheads fitted with Pickpoints (left) or Cutter-Teeth (right)

Draghead fith with Trailer-Teeth


Transport of dredged material

Transport over sea : 3

Side castingBargeHopper

BHDCSDTSHD

Pipeline


Transport of dredged material

Transport over land : 3 methods

PipelineTrestlesDumptrucks


Hydraulisch Transport with pipelines offers many advantages:

• Continu process, fit for huge quantities & productivities: 20.000 to 100.000 m3/day

• Swift mobilisation & readyness• Limited maintenance• Limited Personnel


Dredging & Transport Distance: influence on Unit Price

Example of Unit Price of Dredging as a function of One-Way Distance

0

5

10

15

20

0 5 10 15 20 25One-Way Sailing Distance Dredging to Disposal (km)

Uni

t Pric

e E

uros

/m3

in-s

itu

Trailer Suction Hopper Dredger

Cutter Dredger w ith 2 boosters & pipeline


Principles of hydraulic transport of dredged material

• Disrupted soil or rock Disrupted soil or rock –– individual particles, heavy suspensions or fragments individual particles, heavy suspensions or fragments –– are mixed with are mixed with water to form a slurry (typical densities: 1,15 to 1 ,50)water to form a slurry (typical densities: 1,15 to 1 ,50)

•• MixtureMixture --forming happens in forming happens in dragheaddraghead or or cutterheadcutterhead and is then sucked into the suction pipe, via and is then sucked into the suction pipe, via hydraulic depressionhydraulic depression

•• Mixture velocity and turbulence (Re > 4.000) preven t the mixtuMixture velocity and turbulence (Re > 4.000) preven t the mixtu re from settling downre from settling down

•• After discharge, turbulence decreases and particles are allowedAfter discharge, turbulence decreases and particles are allowed to settle downto settle down


Drawbacks of hydraulic transport

• Limited transport-distances: 2 tot 10 km• Differential settling: siltpockets• Increase of suspension load of transport-water: visual impact of turbidity• Wear of pipes


Hydraulic transport: practical application in dredging

Shipborne pipeline systems


Working principles of a TSHD and a CSD


Hydraulic transport via shipborne & external pipeline systems

TSHD reclaiming


Hydraulic transport via external pipelines

Floating & Land pipeline


Hydraulic transport via floating/land pipelines

Cutter-dredging and direct upland reclamation

CSD Leonardo da Vinci in Port Hedland, australia


Hydraulic transport & reclamation

ReclamationArea: dredged mixture with high solids concentrations



Discharge of transport-water over a weir-system at the outlet of a sedimentation basin


Beach restaurationdirect settling & open-water discharge

(Sylt, Germany),



Hydraulic Transport: Hydraulic-production computations

• cost-estimates for tender-preparation

• dimensioning of dredge-pumps and shipborne pipe systems for the design

of dredgers

• Dimensioning of jet-devices and nozzles for fluidisation of soil prior to

suction

• Control of performance of dredge-pumps

• Development of simulators


Horizontal Transport = transport of a mixture of (sea)water and particles

Clays

Sands

Gravels


Dredging operation: disruption of aquatic soils (rocks, sediments, …) + transport + disposal

Dredgeable Rocks

Hard Limestones, Arenites, Basalts…..

Limestones, Sandstones, .Tertiary Claystones, Mudstones, …Quaternary Calcarenites, cap-rocks, Corals,……

Hard Rocks(UCS 30 – 60 MPa)

Intermediate Hard Rocks(UCS = 12,5 – 30 MPa)

Soft Rocks(UCS < 12,5 MPa)

In hydraulic dredging the maximum allowable grain-size diameter of dredged soil is determined by the spherical aperture of the dredge pumps.


Products of Rock Dredging by Cutter Suction Dredger

Cap-Rock dredged by CSD (Persian Gulf)

Tertiary Claystones dredged by CSD “JFJ DE Nul”(UCS = 11 MPa)


Products of Rock Dredging by Backhoe Dredger

Coral Reef-Flat (UCS = 10 -15 MPa)

Basalt boulders (UCS = 32 -72 MPa)


Products of Rock Dredging by Trailing Suction Hopper Dredger : Ripping mode (only applicable for large TSHD with high installed power, e.g. > 30.000 kW)

Coral Reef-Flat (UCS = 10- 23 MPa)


Rock testing: UCS test result Contract: # EPC 2-04-P902 Borehole: #DK-BH-08 Sample: # 2 Depth, (m) 0,7-0,8 Job:

81.2 71.9 Weight (g) 914.0081.3 72.5 Area (sq.m) 0.00412881.2 73.1 Temperature (С) 168.1 7.3 Volume, (cm^3) 335.351

48 2.73 Machine #: МС-50032.32 2.62 Date: 4.03.05.83.98 0.2 Technician: Timchenko L.

82.00 1.0003.99

0.00 0.00 0.00 0.0 0.00 0.000000 0.004128 0.0000.50 0.50 0.50 42.0 42.00 0.615511 0.004154 10.1111.00 1.00 1.00 92.0 92.00 1.231022 0.004180 22.0111.50 1.50 1.50 168.0 168.00 1.846533 0.004206 39.9442.00 2.00 2.00 225.0 225.00 2.462043 0.004232 53.161

UCS = 53.161 MPaUCS* = 51.318 MPa

E*= 2.150 GPa E = 1.788 GPa 0.000 22.011

UCS* =

E*=

E =

Interval of Stress, (MPa)

UCS - corrected for sample L/D

E - corrected for sample L/D

Initial linear elastic modulus

Standard Test Method for Elastik Moduli of Intact Rock Core Specimens is Uniaxial comhression. (ASTM D 3148-96)

Load Constant, (kN/dv)Basalt

Load (kN) Axial Strain є1, %Corrected area, A' (sq.m)

Applied Stress, UCS (MPa)

Average Height (сm) Average Diameter (cm)

Unit wet weight (g/cm^3)

Type of failure:

Moisture content (%) Sample Description:

Unit dry weight (g/cm^3)Rate (mm/min)

Deformation (mm)

Dry weight + Tare (g)

Diameter #1 (mm) Diameter #2 (mm) Diameter #3 (mm)

Height #2 (mm) Height #3 (mm)

Height #1 (mm)

Nearshore Chihacheva Bay

Average Deformation (mm)

Load (Rdg.)

Tare: # Tare weight (g) Wet weight + Tare (g)

Borehole # DK-BH-08 Sample #: 2 Depth: 0,7-0,8 m

Axial Strain є1, %

App

lied

Str

ess,

UC

S (

MP

a)

Results of Unconfined Compression Test

0.000

10.000

20.000

30.000

40.000

50.000

60.000

0.0 0.5 1.0 1.5 2.0 2.5 3.0


Basic Rock-Mechanical Characteristics for Rock-Dredging

Ductile Rocks

Brittle Rocks


Dredging of Rock: Blasting or Rock-Cutter-Dredging ? A matter of rock and cuttingpower.


Mineralogy of Rocks: Calcirudite ( UCS = 13 MPa)

Calcirudite:

C : Calcite

D: Dolomite

A: Aragonite (Shell-fragments)

Q: Quartz

Polarizing Microscope Photograph

A

Q

D


Mineralogy of Rocks: Granite ( UCS = 95 MPa)

Macro-Cristalline Pink Granite(Magmatic Intrusive Rock):

Q : Quartz

Fp: Feldspars Plagioclase

Fk: Feldspars Orthoclase

M: Muscovite (Mica)

Z: Zircon

Polarizing Microscope Photograph


Rock Mechanics for Dredging: examples

40509060Rock-Quality DesignationRQD (%)

4050150100Rock-Strength DeviceRSD (MPa)

15 - 3060 - 8080 - 10050 - 90Shore Hardness

10 - 1505 - 10300150Abrasivity Index FPMs

591916Puncture Resistance Is50 (MPa)

40160220180Uniaxial CompressionStrength UCS (MPa)

SandstoneLimestonePorphyreBasaltParameter


Dredging operation: disruption of aquatic soils (sediments, rocks,…) + transport + disposal

Sediments: mainly 3 types

2 mm < d5063 µm < d50 < 2 mmd50 < 63 µm

Granular sediments: gravel,

boulders ,…Granular sediments: SandCohesive sediments: Clay &

Silts

In hydraulic dredging the maximum allowable grain-size diameter of dredged soil is determined by the spherical aperture of the dredge pumps.


Geotechnical characteristics of some common sediments

15

20

85

97

97

SandContent > 0,063mm(%)

882.161.861626Well-graded sand

2.322.12920Glacial till

1.27

2.09

1,89

Volume-massSat (tds/m3)

0.4319584Mud (silt-clay)

65 - 851,501934Uniform densesand

< 351,433246Uniform loosesand

Relative DensityDr (%)

Volume-massDry (tds/m3)

Water Contentw (%)

Porosityn (%)

Sediment Type


Geotechnical properties of soils in the horizontal transport process of mixtures

Cobbles, boulders, gravels,…

• Main in-situ geotechnical properties (before dredging)– Grain-size distribution, including d50 (median particle-size),

dmf (determining particle-size = (d10+ d20+…d90)/9), sorting degree,…

– Angularity and grain-form– Angle of Internal Friction,– Specific volume-mass,ρs of individual particles

• Quartzite: 2,660 kg/m3• Basalt : 2,900 kg/m3• Claystone :2,300 kg/m3

• Main mixture properties (during transport)

– Grain-size distribution

– Angularity, abrasivity,..

– Specifiv volume-mass

�Critical velocity

� Wear

� Equilibrium slope

� Settling velocity


Grain-Size distribution of dredged gravel

63mm

.r:f¡: me

~ "'" ~ 90

~

~ "" ~ 70

•

e 100.000

r--.

m "\ \ '\

\ \ , '"

, m ,

I.~ ~

t-.. "-

l' "<; m "-

, l' mm

-........ .:bj 3 m

"'00 0,2 10 mm 0.100 0.010


Granular sediments: gravels and sands


Basic Geotechnics of granular sediments and soils: sands. Dredging is a rapid deformation-process ( xx m/sec) versus the evacuation velocity of excess pore-water pressure ( < 10 – 3 m/sec)>> Undrained Conditions

Relative Density (%) >> Degree of Compaction of granular soil

ρd - ρdmin

Dr = ------------------------- x 100 (%) and Drcrit (Casagrande) : no volume-changeρdmax – ρdmin Dr > Drcrit >> Dilatancy

Dr < Drcrit >> ContractancyWith: Dr < 25 % : very loosely packed

Dr : 50 – 75 %: densely packedρdmax: determined by Modified Proctor Test

Cohesion, c (kPa)– Fine sand (d50 = 0,200 mm) : c = 4 kPa– Very coarse sand (d50 = 0,900 mm): c = 0,8 kPa

Angle of Internal Friction, φ (degrees)– Angular sand-grains (river sand) : φ= 38°– Spherical sand-grains (eolian sand) : φ= 25°

Permeability Coefficient, k (m/sec)– Fine sand : k = 10 – 5 m/sec– Very coarse sand : k = 10 -3 m/sec

Shell-fragment content

Critical erosion velocity (at large flow velocities (> 3 m/sec)At low flow velocities : cfr ShieldsAt high flow velocities: cfr van Rhee

(Drawings after Lübling, 2004)


Grain-size distributions of dredged materials in Western Scheldt

Grain-size distribution of Western Scheldt estuary sediments

100.00

90.00

80.00

l. ¡¡p . -- -•

ti + BAl

F. Fredefik - " - " -" " -1- --" -• ... " , - . "

... 70.00 1- - , • ....

IJI Kallosluis - /. ,

f 60.00

• ., 50.00 E

t - - , Hanswe ert --- - ,

, U

• , , ~ 40.00 ---~ -

• L

• 30.00

Walsoorden t r ' - -- <-

20.00 1, .-1

10.00 • • :.:.; l '

0.00 , . -"

10 1

850 71 0 500 355 250 180 125 00 63 ,

.... :_-_._- ,_ :_--_\


Basic Geotechnics : Mohr’s Circle describing the stress conditions in soils

Total Stress :

ՇՇՇՇ = = = = σσσσnnnn . Tan . Tan . Tan . Tan φφφφ + C+ C+ C+ C

Effective Stress ::::

ՇՇՇՇ’ = (σn- u) . Tan φ’ + CՇՇՇՇ = (Undrained) Shear-Strengthσn = total Normal Stressu = pore-water pressureφ = angle of Internal FrictionC = cohesion


Basic Geotechnics : Mohr’s Circle describing the stress conditions in soils

Granular Soils: sands• low C & ՇՇՇՇ = increasing withdepth

• high φ

Cohesive Soils: clays

• high C & ՇՇՇՇ =~=~=~=~ C

• low φ

σn

ՇՇՇՇ

c

φ


Basic geotechnics: vertical and horizontal stresses

Active & Passive Horizontal Soil Pressure cfr Rankine:In dredging, overburden normal stressesare (generally) low:

• >> low horizontal soil pressure…and equilibrium inflow slope , θ, is generallyclose to φ ρs

2

tg θ = tg φ x -----------------------------

( ρs2 + ρw. (ρs- ρd) )

• angle (π /4 +/- φ’/2) is determining the optimal cutting angle


Erosion-sensitivity of sand at large flow velocities (cfr Bischop et al, 2009)

.. oS ~ e O .¡;; e w

0,100

0,010

0,001

0,000 0,0

Experimental d.lta VS. modal calculations

-,

, ,

, .,: , , • , , ~ •• , , • ,

~' ./ .&

/' ' ./ ~~

/ /.1 'r" •

, • I

•

0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4 ,5

Flow velocity [mIs]

Fig, 9: Erosion rates for Zwin'94-experiment

• 45 degrees side slope angle

• 60 degrees side slope angle

• 70 degrees side slope angle --van Rijn 185 mu --van Rijn 315 mu

- van Rhee-simplified 185 um - van Rhee-simplffied 315 um

¡

1 g

5,0

= .'


Cohesive Soils in hydraulic transport : Clays, Silts, Muds,…

Undrained Shear-Strength, cu (kPa)

Liquidity Index (non-dimension)

Yield Stress, Շy (Pa)

Dynamic Viscosity, η (Pasec)

Thixotropy (Pasec or Watt)


Determining for Cohesive soils:

• water-content (w) and Atterberg limits(SL, PL, LL)

• Plasticity-Index : PI = LL – PL

(PI = high >Clay; PI = low > Silt)

• Liquidity Index: LI = (w-PL)/(LL-PL)

• Activityt : A = PI / (% < 0,075mm)

(A < 0,75 Inactive; A 0,75-1,25: Normal; A > 1,25: Active)

• Shear-strength and Cohesion

• Stress-Strain behaviour


Cohesive sediments dredged and lagooned

After filling at ρsat = 1,32 t/m3 After 1 month: consolidation & dessication

ρsat = 1,60 t/m3


Cohesive Soils in hydraulic transport : indicative values

-0,95

0

2,5

LiquidityIndexIn-SituLI si

-0,580500Montmorillonite(swelling clay)

450100Illite (most common clay)

12,53050Kaolinite(weathering of granite)

LiquidityIndex As slurryLI m

wP(Casagrande’s

PlasticityLimit)

wL(Casagrande’s

Flow Limit)

Type of clay

> 150Hard

75 - 150Stiff

40 - 75Firm

< 40Soft

Undrained ShearStrength , cu

(kPa)

Description

In cohesive sediments, the φ is very low, not to say sometimes

close to 0. This means that shear-strengths of cohesive sediments

are determined by c, the cohesion(which is intrinsic at σn =0. But c is observed to increase slightly

with depth in loose cohesivemuds due to consolidation


Cohesive soils & sediments: Undrained Shear Strength and Liquidity Index

" u

.., 1.0

Q.II

O'.e

Q1

" ~.4 • v S 00.5 .. ~ 0 .4 ... :i o_~ ..J

O'.L

0.1

()

-Q,I

-o ~

LL

.L

A,~ jrjclql soj l M'1<1 ... U

-~' ~~-t-±-t~t-------~----~--~~~~~~~------~~--~~-.~~~~~~~------~~--~~~~~ '" . , , I'.i .1 /(11 ... 1, 2;J. '" !5 fI 1 S, !II j(J 2(I, !O 4 0!iOo I!O JO l1O;)tOCJ 2: 001 !OC 400 i!O:O

U~drQII\.~ S~.Of· Slf'. n ~t~ é u • ~ Pa


Frictional Behaviour of Fluids in Flow

• Water and individual particles: slurry transport– Reynold’s Number– Determining parameters:

• dynamic viscosity of transport fluid (termperature, salinity,…)• Volumetric mass of fluid (kg / m3 or kgds/m3)• Particle dimensions determining Critical speed and Slip-Factor• Velocity, vs Critical Speed

• Viscuous flow of cohesive particles: Non-NewtonianBingham fluids– Hedström Number & Reynold’s Number– Determining parameters:

• Dynamic viscosity of suspension (temperature, salinity, volumetric mass, sand-content)

• Initial rigidity Շy (or Yield Stress Շo)• Thixotropy


Stress-Strain behaviour of Newtonian and Non-Newtonian Fluids

Newtonian : Water

Bingham Plastic:

Pseudoplastic:

Dilatant:

Cohesive sediment suspensions,sludge, paint, blood, ketchup

latex, paper pulp,.

quicksand


Rheology of cohesive-sediment suspensions: initial rigidity, dynamicviscosity and thixotropy (after Malherbe, 1987)

Shear Stress

(Poi

A.INDIRECT MEASU

't; INITIAL "'GtDrn

RESS • STRAIN ANALYSIS

Sheor Rote I.el: ... , •

Shear

(Po)

8 .DIRECT MEASUREMENT

't", IN "'Al IIGtDlTV

STRESS • nME RELATION AT CONSTANT LOW

'SHEAR RATE (VAN E-TEST)

FIGURE 5 Typical rheograms of mud Zeebrugge) together with the defillition rigidity and dynamic viscosity.

Time' mini

(harbour of of initial

'1..-----

40

INtTtAL A.GIDITV U-., DVNAMtC VtBCaStTV (P ••• c' VDLUME MAsa OF .EDIMENT'~/m3J CDNCENTRATIDN CKg/m3, Mue CONTENT ,,, e 63 micron' "O·C

, , , , , I I , . , '

30 .. • ... ,,: , , " . , J " ,

J •• ,&16 :,: , 1 , ", , , I • 7D.B" , , I "", , I ',J; l' , l. .,

20 ./ 1 1:: i! I I l ' 1 142,D"

1 I I l' " • 1~D" 1 I , .... &" 1, I

, 1 ,.J:'" I , I I I 4~" , I 1 I 11 J' I

, I ,'7,; 1

, I " I '1 " , , ", le' , 10 I , ")" " ,

, ' J, I " 3&.D" 1 " / I I l' I I , I l· .aptJ/

100" I I l ' I , I

:~~i~':L ~~~~;i;~~~~;;~~¿:}~t~.4-~,~;¡;¡ _____ "'-1-4 ------ - --- -_. o , ~Yr- ~;;lj:;j.~~~! :

O .-..... : ...... ~:~*--'-f:.~. 1I :: :

o 100 100 400 lOO 700

1.150

Ts gIl

1.400 ~slt

FIGURE 6 : Results of rheologic investigations on mud out of the harbour of Zeebrugge. Relation between the initial rigidity, the density and tlle sand-content of the mudo The figure illustrates a1so the "rheologic behaviour transition", R.T.

17


Rheology will determine erosion-sensitivity (expressed as u*crit) for cohesive sediments (B Malherbe PhD thesis)

" .. ". x 16 2

" 7r

,t .p

.. ,a So"'. .. _,-...-"_", von _' _ _ _ _

"un"nt "homln¡

,.

.. ~ gOlv" n

I-/"~ • l4: O

O ,


Rheology determines the equilibrium inflow slope of cohesive sediments

Equilibrium Inflow Slopes of Cohesive Sediments (Mud Zeebrugge) as a function of Yield Stress or Initial Rigidity

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30

Initial Rigidity Ty (Pa)

Slo

pe F

acto

r (m

)

Equilibrium Slope Under Water Equilibrium Slope Above Water

1

m

θ


Rheology determines the Flow behaviourof Non-Newtonian Bingham Fluids in pipes

Bingham fluids exhibit Newtonian behavior after the shear stress exceeds ՇՇՇՇo or ՇՇՇՇyyyy. In the central region a “plug” of unsheared fluid or suspension occurs.

(ref University of Texas, Austin).

Unsheared plug Core

Sheared Annulus


Flow behaviour of Non-Newtonian Bingham Fluids

Unsheared Core

crr ≤ ( )20

2 cc

cz rRr

uu −==∞µ

τ

crr > ( )

−

+−=∞

012

ττµ R

rrRu rz

z

Sheared Annular Region


Frictional losses of fluids in pipelines: affinities with Friction Cfct & Volume-Mass

Applies to any type of fluid – Newtonian, Pseudo-Plastic, Bingham, Dilatant,…- under any flow conditions

2..

2V

D

Lpf ρλ=∆

General equation describing frictional head losses of fluids/suspensions in pipes


Laminar Bingham Fluid Flow: determination of friction factor

( )

−+= 73

4

Re..3Re.61.

Re

16

BPBPBP

HeHe

λλ

20

2 ..

∞

=µ

τρDHe

∞

=µρ VD

BP

..Re

Hedström Number

(Non-linear)

Reynolds Number


Turbulent Bingham Fluid Flow: determination of friction factor

( )He .146.01.378,1

Re10

.109.2

193.0

5−−

−

+−=

=x

BPa

ea

λλ

λ


Hydraulic Transport: physics of the system

1. Pipeline characteristic (Discharge (Q)/Head (H) relationship)- homogeneous fluid in straight pipe- Soil-water mixtures in straight pipes- special head-losses: bends, narrowings,…- vertical and inclined pipes

2. Pump-characteristic (Discharge (Q)/ Head (H) relationship)

- Pumptypes

- Characteristic for homogeneous fluids

- Characteristic for soil-water mixtures

3. Driving system

- Modification of pump-characteristic

- for diesel-elec, direct diesel,… driving

4. Working area of whole system: driving system, pump, pipeline and mixture


Hydraulic Transport: the Pump – Drive – Pipeline FitDescription via Q – H relationships


Hydraulic Transport: Pipeline Hydraulic Characteristic

Basic Assumptions:• Horizontal cylindric pipeline: no bends, valves,…• Homogeneous incompressible fluid: perfect suspension, no

segregation, no gases,…• Newtonian fluid: (almost) linear realationship between shear stress

and strain• Uniform flow: no velocity profiles between wall and center-line• Constant flow velocity


Hydraulisch Transport: Pipeline characteristic

• Law of mass-conservation:

• Law of momentum-conservation:

outoutinin AVmAVm .... ρρ =

∆p/L = 4.ՇՇՇՇ0 / D (Navier-Stokes) ∆p f = ( α.ρ. v2/2 + λ.L/D. ρ.v²/2 + ξ .ρ.v2/2) (Darcy-Weisbach)with λλλλ=f (Re, He, k/D) ( head-loss coefficient due to friction: see previous slides)

foutin ppp ∆+=


Hydraulic Transport: Pipeline characteristic

• Law of energy-conservation: Law of Bernouilli

Cstghvp =++ ρρ 2

2

1

Pressure Energy

Kinetic Energy

Potential Energy

This physical law expresses the whole process: the pump-d rive plant adds energyto the mixture by increasing velocity: this Kinetic Energy is then oscillatingconstantly within the system between Kinetic Energy (mixture velocity), Pressureenergy (pressure) and Potential energy (elevation). Velocity, pressure and elevation are thus the main parameters of the dredging process .


Hydraulic Transport: Pipeline characteristic

Integration of the 3 physical Laws yields:

Applied to:

• Succession of pipes with various diameters:

• Special losses with dedicated ξ coefficient for bends, valves, etc..:

outoutinin ghvD

Lvpghvp ρρλρρρ +++=++ 222

2

1.

2

1

2

1

222

12

2

1.

2

1

2

1ghv

D

Lvpghvp iioutoutinin ρρλρρρ +++=++ ∑

22222

12

2

1

2

1...

2

1.

2

1

2

1ghvv

D

Lvvpghvp iiiioutoutinin ρρξρλραρρρ +++++=++ ∑∑


Hydraulic Transport: pipeline characteristic

22222

12

2

1

2

1...

2

1.

2

1

2

1ghvv

D

Lvvpghvp iiiioutoutinin ρρξρλραρρρ +++++=++ ∑∑

In the dredging process the geometry/elevation of the pipeline is generallyfixed and known, i.e. not variable during the process. Kinetic Energy and Pressure Energy are the components that can be controlled. They can betransformed into pressure, by dividing the terms by ρ.g.

dynamic pressure and the static pressure (manometric head)

These terms together express the HeadLosses, ∆H, due to friction in the pipelineand in special pipe-components: note the same character as a dynamic pressure!

Entry-losses Straight pipe friction-losses

Bend, valve,..friction-losses


Special resistances for specific pipeline components:


Hydraulic Transport: Pressure Equations

outiiioutoutinin ghvvD

Lvvpghvp ρρξρλραρρρ +++++=++ ∑∑ 2222

12

2

1

2

1...

2

1.

2

1

2

1

Entry-losses

Straight pipe friction-losses

Bend, valve,..friction-losses

Pressure Line:

))./(().(....2

1.

2

1...

2

1..

2

1).(. 2222

mwswmwimimiimmpumpzmzvac vLiSktgvvD

Lvvhhgghp ρρρρρρξρλραρρρ −−−−−−−−−= ∑∑

Suction Line:

Special losses for non-cohesive particles (cfr

Führböter)

Führböter

0

0.5

1

1.5

2

2.5

3

3.5

0 0.5 1 1.5 2 2.5 3

dmf [mm]

Skt

[-]


Hydraulic Transport: Graphical representation of pipeline-characteristic

- Relationship is of the following kind : caQH += ²

aQ² = Head Lossesdue to friction

c = geometric elevation head


Suction characteristic for a horizontal pipeline

p0pin

pz

pp

p0 = patm

p in = patm – (1 + αααα)0.5 ρρρρm v²

Pz = patm – (1 + αααα + λλλλ L/D)0.5 ρρρρm v²

Pp = patm – (1 + αααα + λλλλ L/D)0.5 ρρρρm v² + ∆∆∆∆p


Suction characteristic for a dredge pipeline in operation:

p0 pin

pz

pp

p0 = patm + ρρρρw g h z

p in = patm + ρρρρw g h z – (1 + αααα)0.5 ρρρρm v²

patm

hz

hp

pz = patm + ρρρρw g h z – ρρρρm g (hz-hp) - (1 + αααα + ξ + λλλλ Li/D). 0.5. ρρρρm .v² - ρw.g.Skt.Li.(ρ m-ρw)/((ρs-ρw).v)

pp = patm + ρρρρw g hz – ρρρρm g (hz-hp) – (1 + αααα + ξ + λλλλ Li/D)0.5 ρρρρm v² - ρw.g.Skt.Li.(ρ m-ρw)/((ρs-ρw).v) + ∆p

Li


Hydraulic Transport: Forces on particles in water

Forces exterted on particle:

1. Gravitational force

2. Buoyancy force (Archimedes)

3. Flow-resistance forces• Wall-friction• Drag-resistance

gVF ssg ρ=

gVF swB ρ=

stwDD AvCF ²2

1 ρ=

FB

Fg


Hydraulic Transport: Forces on particles in water

4. Lift-forces due to velocity gradients, particle geometry,….

stwLL AvCF ²2

1 ρ=


Hydraulic Transport: free-fall velocity of particles in water

1 í

0.001

•

• • • •

0.01

o

o ,-" ,-" • , , , ,-r' o . -¡.~ · l· • nff : "-""

Specific Sand & Grave' Fal. Velod!)' in slill Water (18'1::) CIr Jan De Hui Group

, o o-o-, o

o o ..

0.1 1 10

o o o

o o o

'o. o o

o , •

o o

.¡ ••• ~ . .¡ L •••••• '

"

. _ ..... __ . .. _ ... __ . • o

o jo.,.. jo •

, o , , , ,

o .+.-o o o

'0 .

o o

, , , ,

-, o .

o , . .•... ~.~ ..... .

«

• o o . . • . . . • • . . . . . . • o o , , , ,

~, o

" ••

o

o ,~

.

"

o o o ; o o

' .' + .¡ ' .'¡ .'

_ .. __ .-• •• + ••• ,"

. . . • • . •

o ,

•

, ' o

" "

o.,

0.01

0.001

0.0001

0.00001


Practical application: dumping of particles trough a vertical pipe

Non-visquous fluids: only local water-displacement around the particle compensatesfor the volumetric passage of the particle. The total Head remains constant

Visquous fluids : the particle drags an added mass of water during its fall and the upward compensating current gets resistance from the wall of the pipeand the stone. The water-head decreases in the pipe.


............ '_ ........ ""...., .. J." Oo ..... DP cr. .. , ( __ ).

' .700 m

2.<00 ....

' .000"",

~ ,," ..... O H., ..... . OOmm -_....-. .... ....". .... ..,.,.. . .,..-m. ... ."..., __ ..~-'" -_." ............ ......-. ( ... _...,~,..., """'_

'0. '" m (_"""''''1 ,_ . .,..,.,_ ........

I""",,J ... . 0 .... . -- '"

, " , .• ,-"" " .2 m

' .' m (:'0.000 ""'J "-" m (''''00 _ 1

,",ro m'

,".' '''-h . "'" _N ., ..... ,. ro~

=


Hydraulic Transport: Application in Deep Sea Mining


Hydraulic Transport: Application in rock-dumping


Hydraulic Transport: Application in rock-transport, ballasting of GBS


Hydraulic Transport: Particles in flowing water inside a dredge pipe

During the hydraulic transport-process of a dredger:- the dredge-pump & drive plant, adds energy to the fluid by increasing

its Kinetic Energy, which is soon transformed into a combination of Kinetic energy (fluid velocity) and into Potential energy (pressure)

- By increasing the velocity, the turbulence within the fluid will increase, hence facilitating the keeping of particles in suspension

- Energy will not really be transmitted to the sand-particles, but- Particles are kept into suspension by turbulences and

(omnidirectional) turbulent forces- They will be dragged by dragforces (actual friction resistance)

caused by the moving fluid- The velocity of sand-particles is lower than the one of the moving

fluid: this phenomenon is called “slip” and depends upon the sizeof the particles, the concentration of solids inside the suspension, the viscosity, etc…


Hydraulic Transport: Hydraulic regimes of particles in flowing water

Mainly, 4 flow-regimes:

Stationary bed Sliding bed with Homogeneouspartial suspension suspension

Governing factors- Increasing velocity: more drag, more turbulence- Increasing viscosity (increasing concentration): more drag- Decreasing grain-size: smaller fall velocity- Decreasing pipe-diameter: higher velocity


Hydraulic Transport: Hydraulic regimes of particles in flowing water

Particular Case: Plug flow occurring mainly with cohesive sediments(mud-type) with high concentrations , viscosities and/or yieldstress

Plug

Sheared Annulus


Hydraulic Transport: Phenomenon and physics of Slip

Slip-velocity is dependent upon hydraulic regime

- Particle in suspension:

- Particle in sliding bed:

- Particle in vertical flow:

Factors governing slip:• Contact-surface between particle and fluid• Specific density of particles wrt fluid• Grain-size diameter

slîpws vvv −=

0≈slipv

wslip vv <<0

0≈slipv

0.4-0.65Boulders

0.65-0.85Gravel

0.7-0.9Coarse Sand

0.8-1Fine Sand

0,9 - 1Silt and Clay

Slipfactor ƒsSediment/soil

m

sS v

v=∫


Hydraulic Transport: Effect of Inclination of dredge-pipe on Slip

Inclined pipe: large Slip-factor

Vertical pipe: small Slip-factor

Horizontal pipe:

Intermediate Slip-factor, see prev tabe


Volume-Mass and Density: Concepts and Definitions

Volume-massρρρρ is the mass of a soil (kg) per volume-unit (m3). The unit of volume-mass is kg/m3.

The mass of a saturated soil is determined by:• The solid constituents - grains, rock-fragments, shells, organic

matter…- and their specific volume-mass• The liquid or gaseous constituents in the voids between the solids• The proportion (%) of these 3 different phase-constituents in 1 m3,

determined by void-ratio, compaction-degree,… and the gas-content in the fluid

Density is the volume-mass of a soil referred to the referencevolume-mass (fresh water at ρρρρ w = 1.000 kg/m3). Density is hence dimensionless.


Facts and Figures about volume-mass

• Dry solid volume mass• Void-content n = volume of voids / total volume

typically is n = 40 – 60% for granular soils

• Specific volume-mass of solids: Quartz, Feldspars, Carbonate

• Typical values for sand are 1.100 – 1.500 kgds/m³

• Volume-mass of (water) saturated mixture

Typical values for sand are 1.800 – 2.000 kg/m³(variable according to shell-content, grain-size distribution, grain-shape, compaction-characteristics,..)

³/7.265.2 mts −=ρ

sairsd nnn ρρρρ )1()1( −≅+−=

wssat nn ρρρ +−= )1(


Volume-mass and sediment-soil properties

Volume-mass of a sediment or soil expresses the packing of grains and will determine:

• Cohesion and shear- resistance• Relative compaction degree (granular soils)• Degree of consolidation (cohesive soil)• Void ratio


The first most important geotechnical equation in Dredging

:

R.~onsh ip between Dry Vo l ....... -mólss;md S;nurMed VoIurne-m;ass

~OO T"----------------------------------------------------' Pd = (P,a' - P ... ) x _p, __

( p, - P .. )

P .. - 10!5 q,'m.l (,u'In' .... id. Sal _ jO ' . ' " Y._ - " "CJ

p , _ , . , ' ,-oIu ......... -.; h. of • • e'"',.,'--__ -1

" ,..., ~ • >

j ,...,

'.00 +-----__ ------,_----__ ------,_----__ ------__ ----__ ------__ -----' • ..., . 00 1200 ,..., ,..., ,"'o

Dry VoIUITMI Mus (kg dsIm3)


The second most important geotechnical equation in Dredging: the mechanisms of dilution and concentration

Principle of Continuity of solids = during the whole process of dredging – between in-situ, via dredged mixture to discharge and ultimately consolidation/compaction – the mass of solidsdoes not change. The only changes occurring are related tothe proportion of water & gases vs. solids.

Two exceptions:• During overflow: overflow losses induce the loss of fines to the

natural system. • During disposal: fines are dispersed (aquatic disposal) or

evacuated as fines over the weir


Continuity of mass of dry solids (cont)

M dsx = mass of dry soils/mixture-solids in stage xV = bulk volume of soil/mixtureρd = (ρsat – ρw) x _ρs___

( ρs – ρw)• ρw = 1025 kg/m3 (seawater with Sal = 30 0/00 and Temp = 15°C)• ρs = 2650 kg/m3 (specific volume-weight of Quartz)

M ds 1 . V1 = M ds 2 . V2 >> (ρρρρsat 1 –ρρρρw). V1 = (ρρρρsat 2 –ρρρρw) . V2

V1 (ρρρρsat2 –ρρρρw)

V2 (ρρρρsat1 –ρρρρw).Cf =

This simple formula transforms any soil-volume in any other volume, just on the basis of the bulk saturated volume-mass.

Cf is often called the ‘Concentration Factor’.


Dredging Volumes Control: what is measured ? And where ?

Production control can only rely on (online) measurements !!.

Bathy Survey

Vdel = Vin-situ in- Vin-situ out

In-situ (post dredging)

Topo survey

Vdel

Geotechnical survey

ρdel

On disposal

In hopper

Vdel

Suction & discharge tubes

Suction tube

V mixture

Suction tube

ρmixture

Onboard dredger

Bathy Survey

V in-situ in

Geotechnical surveyρin-situ

In-situ (pre-dredging)

Volume(m3)

PressureHeads(kPa)

Velocity(m/sec)

Volume-mass(kg/m3)

Site


Hydraulic Dredging Volumes during Transport: Notions of Apparent Concentration and Delivered concentration

Mwater

Msolids

In-SituρisVsi

MixtureρmVm

Dilution (bulking) Discharge (delivery)

Consolidation

DischargeρdelVdel

ConsolidatedρconVcon

Apparent Concentration Ca

Ca = Vm (also referred to as Cvi)

Vsi

Delivered Concentration Cdel

Cdel = Vdel (also referred to as Cvd)

Vsi


Hydraulic Discharges during Transport

The mixture- discharge, Qm, is defined as the sum of the (transport-) Water-Discharge, Qw, plus the Solids-Discharge , Qs. Discharge introduces the notion of unit-time: xx m3/sec.

However, the measuring gauges, monitor 2 parameters:• ρsat or ρbulk (radio-active transmission probe, measuring the

attenuation of γ -rays, interacting with large atoms)• vw or the velocity of the electrolytic fluid water (electro-magnetic

gauge)

Hence, no direct measurement is achieved of the Solids-Discharge, Qs,…which is ultimately what a dredger is only interested in. Sediment-particles in a moving fluidare known to “slip”, which means they are moving with a velocity slower or equal tothat of the fluid (see Slide 47). That’s why the Ca is called ‘apparent’.

Therefore, there is little other choice for the dredger than to assume a slip-factor , ƒs, for the transported sediment, and to calculate the Solids-Discharge from the Mixture-Discharge.

Qdel = ƒs . Qm = ƒs. vm.A . Ca A = section of dredging tube at the gauge


Hydraulic Discharges during Transport

In the equation above, all parameters are measured or known , except the slip-factor, ƒs.

But ƒs can , in some circumstances, be measured by feedback: when comparing the total integrated mixture volume, Vm over a given period, with the (topographical) measured Vdel (e.g. via Digital Terrain Modelling of an upland confined disposal facility) over that same working period, one gets a better approximation of the ƒs factor.

This is, of course, only valid for (almost) instanteneous compacting/consolidating sediments like sands and gravels. Granular sediments/soils bulk more during hydraulic transport, but get back rapidly to their (more or less) original (in-situ) compaction degree. (FYI: the ƒs is quite different from 1 for granular sediments).

Cohesive and/or fine-grained sediments/soils will bulk less, will need time to consolidate to a constant value and will generally keep a residual bulking (within a project-period of months or years). Unless, accelerated consolidation by dewatering is done. (FYI: the ƒs is generally close to 1 for cohesive sediments)

Qdel = ƒs . Qm = ƒs. vm.A. Ca


Application of concentration-equation: Compaction and Consolidationof Dredged & Delivered Materials

, .. , .. , • , - .. s

, , lO

,

h .. A' 18

lO ., ;1 .. I lO • o • .. ! ; .

" / .... • .... .... .... .... , .... , .... , .... , .... , ..

nm. l ' I I t tinco To(JrMI

-


Application of concentration-equation: Production-Control and Cyclus-Management

Loadlng Dlagram of a Tralling Suction Hopper Dredger

60000

50000

I~) Drtd , ia; : 1(6) Dumpi., I r ,0,,,",.',, I ~~) Soi!i., foU '0

I ,1 '1 Id .... un

, (J) D~,u.,: I , . opptr loodi., l ' <--> ,

40000

" ~ 30000 3 t ~

, , ~ I I I I

/ I

I

I I

(l ) Ho~pt'r I I ,

.mp~ ... ;

"" I

20000

10000

(1 ) s om. ,.o I Y I I drtd , . '0.'

I I * I

I

o o 20 40 60 80 100 120 140

Cycle-time (minUles)


Double Transformed Loadlng Dlagram of a TSHD

60000 Il'rodu ri.-. timt,

• ,'Í-~ 50000 ~ • ~ ~ , 'O 40000 •

"1 e o "-~ , ~ 30000 "" / 1 ~ • .. ~ e 20000 --1 • l ," ' >

• e S

t - 10000 , ----e , - ,-• , E

,

• u • .. O -" O 40 60 80 100 120 140

-10000

Cycle time (minutes)


Application of concentration-equation: optimization of productivity byincrease of mixture-density

• " ~ I ~

.~

.~ •• " o ~

~

2

1.9

1.8

1.7

1.6

1.5

1.'

1.3

1.1

1 1000

Enect o, Increase in Mixture Volume-Mass on Cyclus-Productlvity (tdsfcyclus)

1050 1100 1150 1200

Increólse in Mixture's _- '!" volume-mass

1250 1300

Original Mixture Volume-Mass (kglm3)

1350 1400 1450


Hydraulic Transport: Examples of sequence of Volume-Masses and volumes in a dredging & reclamation project

Saturated (water) Dry


Hydraulic Transport: Hydraulic Process description

The hydraulic transport of sand-water mixtures is (for the time being) too complex and too poorly understood to be describedanalytically. Therefore, engineers have to rely on empiricalrelationships and formulae

The most relevant empirical formulae are based on closed-looplaboratory tests:

- PhD’s theses uit ’50-ies en ’60-ies- R. Durand & E. Condolios (1952) – R. Gibert (1960)- Alfred Führböter (1961)- Jufin-Lopatin (1966)- Wilson (1972-1996)

But the lab-tests had drawbacks:� .too small diameters of pipes (excepted Durand and Wilson)� too limited concentration ranges� selected (near ideal) dredged materials (excepted Durand)


Hydraulic Transport: Two-layered Model cfr Wilson

Wilson (1992-1996)

A = Wet Surface

C = Concentration

V = Volume


Hydraulic Transport: Two-layered Model further elaborated

Václav Matousek – TU Delft (1997)


Hydraulic Transport: Real-scale tests on Two-Layered ModelVia verification on real-scale reclamation works, the Two-Layered

model was transformed into a practical engineering tool –Pusan Port Development (South-Korea, anno 2002) 0,300 mm sand


Hydraulic Transport: Practical engineering State of the Art

Concluding:- Only empirical formulae are used- Parameters are calibrated with site-specific measurements or

experience-data- Corrections to be applied for different pipe-diameters, cutter dredgers

or hopper dredgers,…Careful:- Input-data are generally not precise (too little soil and soil-variability

data)- median grain-size is not easy to determine- effect of coarse materials (boulders,…) is huge : stones> 5 cm diameter are removed from lab-tests- effect of fines on dynamic viscosity- effect of variations in grain-size distribution

- Type of dredging is importantTSHD: Segregation of material in hopper: coarser under

discharge pipeCSD: undercutting vs overcutting

- Variations in process-parameters are not smoothed out over long discharge-pipes


Hydraulic Transport: Hydraulic characteristic of sand-water mixture

- Relationship is of the following type:

- Minimum of curve: critical velocity/discharge

cQ

baQH ++= ²

vcrit

settling suspension


Hydraulic Transport: Influence of variable concentrations and grain-sizes (Führböter)

Effect of increasing concentration Effect of increasing median-grain-size


Hydraulic Transport in Pipelines: Affinities with Grain-Size

water

Counter-Pressures (bar)

Mixture Velocity[m/s]

0 1 2 3 4 5 6 7 8 9 10 11 12

5

10

15

Mediumsand

Coarse Sand

gravel

Fine sand

Water


Hydraulic Transport in Pipelines: Affinities to Volume-Mass

Counter Pressure[bar]

Mixture Velocity [m/s]V crit

Water

Fine Sand, 1.200t/m³

Fine Sand, 1.500t/m³


Hydraulic Transport in Pipelines: Affinities with Pipeline-Length

Counter Pressure[bar]

Mixture Velocity [m/s]V crit

Water

Fine Sand, 1.200t/m³, 1000m

Fine Sand, 1.200t/m³, 1500m


Hydraulic Transport:

END of PART 1


Hydraulic Transport: Exercise about Concentration

Input: Dredged Material : Silty SandIn-Situ Volume-Mass :ρ sat = 1.500 kg/m3Measured Volume-Mass in Pressure Tube: ρm = 1.300 kg/m3Measured velocity in Pressure Tube : v = 5 m/sec

ρs=2.65 t/m³ρw=1.025 t/m³

Calculate : • What is the bulking factor due to hydraulic dredging ?• What is the apparent Concentration ?• What is the Delivered Solids Discharge (estimated)?

hydraulic dredging: horizontal transport. part 1: transpot

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