SlideShare une entreprise Scribd logo
1  sur  78
Télécharger pour lire hors ligne
Dredging
Dredging
WHAT IS DREDGING?
Dredging is the term given to digging, gathering, or
pulling out material to deepen waterways, create
harbours, channels, locks, docks and berths, desilt
lakes and keep river entrances and approaches to
boat ramps clear. The material removed during
dredging can vary greatly and can be any combination
of rocks, clays, silts or sands.
WHY DREDGING?
   To maintain the depth in existing ports, harbours and channels to
   provide ready and safe passage for commercial and recreational
                                vessels.
  To create new or deeper access or berths for vessels. This may mean
  the deepening and widening of channels and anchorages as well as
   the excavation of basins and marinas from areas of previously dry
                                   land.
 To provide material for specific purposes, eg. beaches in coastal areas
subject to erosion are sometimes ‘renourished’ with sand dredged from
                              other areas.

   To bypass an artificial structure , such as a breakwater, that is an
obstacle to the normal pattern of sediment movement along the coast.

 Dredging prevents a build up of material to be deposited down stream
of the obstacle to allow the natural sediment transport process to occur.

                To place a structure inside water bodies
DREDGING PROCEDURE

Dredging procedure can be classified as:

 Pretreatment,
 Extraction and
 Disposal.
DREDGING PROCEDURE
Pretreatment :

Pretreatment means treatment of the ground before
the dredging operations.
It usually consists of a separate operation carried out
independently of other dredging.
There are two basic methods of pretreatment:
chemical and mechanical and both are applied to rock
or cemented soil.
DREDGING PROCEDURE
Extraction:
The extraction process involves the movement of the spoil
from its natural pretreated position into vertical
transportation and its delivery to the transport system.

Extraction processes are often a combination of at least two
operations: the primary operation which disintegrates or
dislodges the soil and the secondary operation which moves
it.

The first of these operations        is   performed   either
mechanically or hydraulically.
DREDGING PROCEDURE
Disposal :

Disposal facilities are consist of bottom discharge,
grab, scrapers, pipelines, land based unit, natural
processes.
DIFFERENT TYPES OF DREDGING

  Dredging can be classified as:

  1. Mechanical Dredging
  2. Hydraulic Dredging
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:
    Mechanical dredging involves removal of
    material by a bucket, placement of the material
    in a scow or on a barge, and towing that scow
    or barge to a disposal or transfer area.
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:
     oIf a scow is used with open water disposal, the
     doors would open at the disposal site, releasing
     the material to fall through the water column to
     the bottom.
     oIf a scow or barge is used with any other type
     of disposal, it would be towed to the disposal or
     transfer site where another bucket machine
     would remove the material from the scow or
     barge and transfer it onto a vehicle or directly
     into a near shore disposal area.
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




          Aerial view of Mechanical Dredging
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




          Aerial view of Mechanical Dredging
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




         Dredged materials being pulled out
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




      Dredged materials are being stored on a barge
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




   Dredged materials being transported to disposal area
DIFFERENT TYPES OF DREDGING
Mechanical Dredging:




         Dredged materials being disposed
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:
    Hydraulic pipeline dredging involves use of a hydraulic
    (suction) dredge, most commonly for either beach
    nourishment of suitable sands, or deposit into an upland
    containment area (for dewatering or direct disposal).
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:

     Hydraulic dredging provides the cleanest and
     least obtrusive method for sediment removal
     without damaging the sensitive environment.
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:


 Typically the dredge uses a cutter head on the end of the
 suction arm to loosen the material while the dredge pump
 suctions the loosened material through the arm to the
 pump in a slurry of about 75 to 90 percent water and 10 to
 25 percent sediment. The slurry is pumped through a
 pipeline to a disposal site or dewatering/transfer area.
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:
A hydraulic dredge floats
on the water and
excavates and pumps the
material through a
temporary pipeline to an
offsite location, often
several thousand feet
away. This dredge acts like
a floating vacuum cleaner
that can remove sediment
very precisely.
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




  Dredge is dropped into the water using a crane
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




 Aerial view of barge with hydraulic dredging
 equipment removing ash from the navigation channel
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




   Ash and water are pumped though this pipeline
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




      Relay pump in the middle of the pipeline
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




  Ash and water discharge into holding area .
  Sediment can then be de-watered and either
  replanted or trucked off location.
DIFFERENT TYPES OF DREDGING
Hydraulic Dredging:




 Ash and water discharge into holding area . Sediment
 can then be de-watered and either replanted or
 trucked off location.
Types of Dredgers

According To Dredging Types Dredgers Are
Divided Mainly Into Two Kinds:

1. Mechanical Dredgers
2. Hydraulic Dredgers
Types of Dredgers

In the Mechanical Dredgers material is
conveyed By mechanical contravenes,
whereas, in the Hydraulic Dredgers, it is
conveyed by water through pipes.

They are further classified under various
principal types, depending on their mode of
operation.
Mechanical Dredgers
(i) Bucket or Grab Dredger:
It is essentially a stiff-leg
derrick on a floating platform.
By means of a derrick
arrangement it lowers an open
grab bucket onto the material,
fills it there and lifts it.
The        material      is either
deposited        alongside      the
channel, or dumped in barges
or in hoppers provided on the
dredger.
Mechanical Dredgers
(i) Bucket or Grab Dredger:
Mechanical Dredgers
(i) Bucket or Grab Dredger:
Mechanical Dredgers
(i) Bucket or Grab Dredger:
Mechanical Dredgers
(i) Bucket or Grab Dredger:
  Mechanical dredgers work best in consolidated,
  or hard packed materials and can be used to clear
  rocks and debris.
  The advantage of the bucket dredger lies in its
  ability to work in small areas inaccessible to other
  types of dredgers.
  It is efficient in homogeneous materials,
  particularly in stiff mud.
Mechanical Dredgers
(i) Bucket or Grab Dredger:
  The digging power of the bucket depends on its weight
  and its effect is diminished by the lifting tendency of the
  closing wire.

  It dose not have sufficient penetration power to obtain a
  full load in harder material, compacted sand, gravel and
  clay.

  Sometimes, the bucket spins twisting the opening and
  closing wires; the operation is stopped till they are
  straightened out, resulting in much loss of time.
Mechanical Dredgers
(ii) Dipper Dredger:
• The dredger consists of a floating power shovel, and
  except for the digging equipment, it is same a bucket
  dredger.

• It should be used only if the material is resistant such as
  soft rock, boulders’ material consisting of timber etc.

• Its unit cost of dredging is higher than for other dredgers.
Mechanical Dredgers
(ii) Dipper Dredger:
Mechanical Dredgers
(iii) Ladder Dredger:
• This consists of buckets attached at each end of the
  frame.
• It is suitable to excavate cohesive materials.
• These dredgers are used even with self-contained
  hoppers. When hoppers are not provided, scow
  (flat-bottom boats) are required to dispose of
  dredged materials.
Mechanical Dredgers
(iii) Ladder Dredger:
• In river and harbors works, this dredger is suitable
for digging stiff, hard and non-homogeneous
materials; loose sand and soft mud tend to wash out
of the buckets reducing its efficiency for these
materials.

• This dredger is extensively used in Europe and in
the Suez Canal.
Mechanical Dredgers
(iii) Ladder Dredger:
Mechanical Dredgers
(iv) Hopper Dredger:
• A self-contained and self-propelled hopper dredger is
  provided with either a bucket or a dipper.
• But its drawback is that a self-contained hopper
  arrangement generally makes the draft excessive and
  it cannot be used for shallow dredging.
• With this dredger, however, material can either be
  dumped alongside the channel to be dredged, or in any
  place where it is required or where it can be carried
  away by the stream.
Mechanical Dredgers
(iv) Hopper Dredger:
Mechanical Dredgers
(v) Rock Dredger:
• Formerly, when rock had to be removed, the materials
  was broken by blasting, and removed by bucket
  dredgers.
• Of late, where rook is soft, it is removed by means of
  strong steel claws; where it is hard, it is broken up by
  the use of heavy rams.
• The rock outers have the form of heavy chisel pointed
  rams, which after being raised, are allowed to drop 3 to
  6 m. (10 to 20 ft.) on the rock.
• With rams of sufficient weight, hardest rocks can be
  broken up. The debris is removed by grab.
Mechanical Dredgers
(v) Rock Dredger:
HYDRAULIC DREDGERS
(i)Plain Suction Dredger:
   •   This is the simplest hydraulic floating dredger
       with a centrifugal pump and auxiliary
       equipment mounted in the hull.
   •   The size and type of the hull depends on the
       size of the pump used and the amount of
       power needed to operate the equipment.
   •   The size of the dredger is generally described
       by the diameter of the discharge pipe, which
       ranges from 15.2 to 76.2cm (6 to 30inch).
HYDRAULIC DREDGERS
(i)Plain Suction Dredger:
HYDRAULIC DREDGERS
(i)Plain Suction Dredger:
HYDRAULIC DREDGERS
(ii) Cutter Head Dredger:
    • It is similar to the suction dredger, except that
      it has a rotary cutter head which carves clay,
      breaks off chunks of softer rocks such as coral
      and shale, and stirs up gravel and sand so that
      pipe carries material to its capacity.

    • This dredger is being suitable for channel work,
      cut-offs, new construction, harbor excavation
      and making fills.
HYDRAULIC DREDGERS
(ii) Cutter Head Dredger:
HYDRAULIC DREDGERS
(iii) Dust-pan Hydraulic Dredger:
    • These dredgers are similar to the cutter head
      pipe line dredge except that in the former
      horizontally spread suction heads, similar to a
      dust-pan or a vacuum cleaner nozzle, are
      employed.
    • Instead of a rotary cutter, high velocity water
      jets are mounted in the suction head to loosen
      the material.
HYDRAULIC DREDGERS
(iii) Dust-pan Hydraulic Dredger:
     • The suction head may be as wide as 9.7 m.
       (32ft.) and is provided with nozzles, through
       which water is pumped at 1.8 kg. /sq. cm. (25
       1b./sq. in. ) to agitate the material so that it
       can be more easily picked up.

     • This dredger is commonly used on the
       Mississippi River for the maintenance of
       navigation channels.
HYDRAULIC DREDGERS
(iii) Dust-pan Hydraulic Dredger:
HYDRAULIC DREDGERS
(iv) Hopper Dredger Hydraulic Type:
     • It is equipped to operate as an anchorless
       hydraulic dredger for transporting and
       dumping the excavated material without the
       assistance of auxiliary plant such as tugs,
       barges, etc.

     • This dredger is capable of operating in rough
       water where pipe line dredgers are
       unsatisfactory because of the breaking of the
       pipe line.
HYDRAULIC DREDGERS
(iv) Hopper Dredger Hydraulic Type:
HYDRAULIC DREDGERS
(iv) Hopper Dredger Hydraulic Type:
     • It is particularly suitable in busy and
       crowded harbors, whereas pipe line
       dredgers, with their long anchor cables
       and pipe lines, occupy much space and
       are slow, impeding harbor traffic.
     • The principal elements of the hopper
       dredger are the pump, the drag hoist
       and hopper bins.
HYDRAULIC DREDGERS
(iv) Hopper Dredger Hydraulic Type:
Dredging and River Bank Protection

• Dredging is getting popular day by day as a
  means of river training work to improve the
  navigational depth as well as attain channel.
  stabilization



                        Focus of Interest
Dredging and River Bank Protection

        Stabilization


          Leads to
     State of Equilibrium

                            Very difficult
     Protected River Bank     to Attain
Dredging and River Bank Protection

 • The combined use of dredging, dikes and the
   disposal of dredged material in the dike fields can
   introduce major changes in the cross sectional
   characteristics of a river.
 • The dredging and contraction reduce the width-to-
   depth ratio of a river upto an extent.
 • They increase the channels capacity for transport
   of suspended portion of bed material.
 • It decreases the capacity for transport of bed load.
Dredging and River Bank Protection

 • Dredging can significantly altered river
   characteristics when employed as an agent for
   morphologic changes in support of engineering
   requirements for river system development.
 • Dredging and open water disposal of dredged
   material in support of channel maintenance
   implies the moving of alluvial sediments from
   the mail channel or thalweg region toward the
   periphery of the channel.
Dredging and River Bank Protection

 • This continued lateral redistribution of
   sediments not only interrupts the natural
   downstream movement of sediment in a system
   but also affects the local channel morphology.
Dredging and River Bank Protection

   • The lateral redistribution of sediment
     by dredging combined with the
     contraction works not only affect the
     local    channel     morphology    but
     indirectly retards the movement of bed
     load through the system.
Dredging and River Bank Protection


Channel Morphology               Change in
                                 Behavior



                      DREDGING
Sediment Movement
                                  Needs
                                 Extensive
 Hydraulic behavior              Research
     of Channel
Dredging To Deepen Critical Sections
Dredging To Deepen Critical Sections
IMPACTS OF DREDGING
Dredging activities have the potential to change
the environment.
At the sites of dredging and disposal the seabed
and associated communities are disturbed and for
some distance, suspended sediment may cause
turbidity in water and increased sedimentation on
the bottom.
Depending upon the nature of the dredged
material, its disturbance from the sea bed may lead
to changes in the chemical composition of the
water.
IMPACTS OF DREDGING

As well as toxicants, the nutrient elements,
particularly nitrogen and phosphorus, which
control the rate of marine plant growth can also
be released from sediments during dredging,
with a risk of triggering algal blooms.
Another biological risk from dredging involves
the transport of species in dredgers from one
port (or even country) to another.
IMPACTS OF DREDGING
MORPHOLOGICAL AND HYDRAULIC RESPONSE
         DUE TO DREDGING

   • Dredging effects the morphological and
     hydraulic behaviour of a channel section.

   • Due to initial deepening or capital dredging of
     a channel, the river bed is degraded until the
     balance between the sediment load supplied
     to the river reach and the sediment transport
     capacity of the flow is restored.
MORPHOLOGICAL AND HYDRAULIC RESPONSE
         DUE TO DREDGING

    • In the long term the result will be
      degradation to a more gentler slope and a
      greater depth downstream of the point of
      dredging.
    • Degradation will also occur in upstream
      which leads to lowering of river bed with
      initial slope.
Dredging in Bangladesh
• Two types of dredging are conducted in
  Bangladesh:

Capital Dredging
    (Example: Gorai River Project by BWDB)

Maintenance Dredging
    (Example: Paturia and Daulatdia Ferry Ghats
        by BIWTA)
Dredging in Bangladesh
Gorai river project:
Dredging in Bangladesh
Gorai river project:




         Aerial view of the cutter suction dredger at work in
         Gorai river project
Dredging in Bangladesh
Gorai river project:




         Aerial view of the cutter suction dredger at work in
         Gorai river project
Dredging in Bangladesh
Gorai river project:




         Aerial view of the cutter suction dredger at work in
         Gorai river project
Dredging in Bangladesh
Gorai river project:




       The dredging continues in Gorai river project
Dredging

Contenu connexe

Tendances (20)

Spillway gates
Spillway gatesSpillway gates
Spillway gates
 
Reservoir
ReservoirReservoir
Reservoir
 
Tunnelling
TunnellingTunnelling
Tunnelling
 
Power shovel
Power shovelPower shovel
Power shovel
 
Introduction to dredging
Introduction to dredgingIntroduction to dredging
Introduction to dredging
 
Earthen Dams
Earthen DamsEarthen Dams
Earthen Dams
 
DRAG-LINE CONSTRUCTION EQUIPMENT
DRAG-LINE CONSTRUCTION EQUIPMENTDRAG-LINE CONSTRUCTION EQUIPMENT
DRAG-LINE CONSTRUCTION EQUIPMENT
 
Docks & harbors construction
Docks & harbors construction  Docks & harbors construction
Docks & harbors construction
 
Types of earth dams
Types of earth damsTypes of earth dams
Types of earth dams
 
Design of tubewell
Design of tubewellDesign of tubewell
Design of tubewell
 
Dredging psa 22
Dredging psa 22Dredging psa 22
Dredging psa 22
 
Geotechnical investigations for tunnelling
Geotechnical  investigations for tunnellingGeotechnical  investigations for tunnelling
Geotechnical investigations for tunnelling
 
Investigation for bridge construction
Investigation for bridge constructionInvestigation for bridge construction
Investigation for bridge construction
 
Tunnels, types & importance
Tunnels, types &  importanceTunnels, types &  importance
Tunnels, types & importance
 
Reservoir sedimentation
Reservoir sedimentationReservoir sedimentation
Reservoir sedimentation
 
Docks and their classification
Docks and their classificationDocks and their classification
Docks and their classification
 
Grouting
GroutingGrouting
Grouting
 
Canal headworks
Canal headworksCanal headworks
Canal headworks
 
Failure of weir and barrage
Failure of weir and barrageFailure of weir and barrage
Failure of weir and barrage
 
Design principles and requirements of harbours
Design principles and requirements of harboursDesign principles and requirements of harbours
Design principles and requirements of harbours
 

Similaire à Dredging

Offshore mining
Offshore miningOffshore mining
Offshore miningAbhiRam152
 
EXCAVATION AND EARTHMOVING EQUIPMENTS
EXCAVATION AND EARTHMOVING EQUIPMENTSEXCAVATION AND EARTHMOVING EQUIPMENTS
EXCAVATION AND EARTHMOVING EQUIPMENTSsauravchandel1
 
Advance Construction equipment's reports
Advance Construction equipment's reports Advance Construction equipment's reports
Advance Construction equipment's reports ssuser061280
 
Drag line excavator
Drag line excavatorDrag line excavator
Drag line excavatorParth Desani
 
ppt%20act.pptx
ppt%20act.pptxppt%20act.pptx
ppt%20act.pptxModiDeep2
 
construction equipments.pptx
construction equipments.pptxconstruction equipments.pptx
construction equipments.pptxzaindeen6
 
13surface mining
13surface mining13surface mining
13surface miningArun Kumar
 
Civil Engineering Technology (Fawzan Fahry)
Civil Engineering Technology  (Fawzan Fahry)Civil Engineering Technology  (Fawzan Fahry)
Civil Engineering Technology (Fawzan Fahry)FAwzan Mohamad
 
Construction equipments - Introduction and Classification
Construction equipments - Introduction and ClassificationConstruction equipments - Introduction and Classification
Construction equipments - Introduction and ClassificationSagar Radadiya
 
building construction,ppt
building construction,pptbuilding construction,ppt
building construction,pptPawankumarm65
 
construction equipment
construction equipment construction equipment
construction equipment Purav Patel
 
Chapter-1 Introduction to Construction Equipments (1).pptx
Chapter-1 Introduction to Construction Equipments (1).pptxChapter-1 Introduction to Construction Equipments (1).pptx
Chapter-1 Introduction to Construction Equipments (1).pptxMubarekTeshome1
 
Construction equipment
Construction equipmentConstruction equipment
Construction equipmentPRIYANKAAKULA6
 

Similaire à Dredging (20)

Offshore mining
Offshore miningOffshore mining
Offshore mining
 
DREDGING
DREDGINGDREDGING
DREDGING
 
EXCAVATION AND EARTHMOVING EQUIPMENTS
EXCAVATION AND EARTHMOVING EQUIPMENTSEXCAVATION AND EARTHMOVING EQUIPMENTS
EXCAVATION AND EARTHMOVING EQUIPMENTS
 
Topic 7-mining methods-part iii -surface mining- placer mining
Topic 7-mining methods-part iii -surface mining- placer miningTopic 7-mining methods-part iii -surface mining- placer mining
Topic 7-mining methods-part iii -surface mining- placer mining
 
Types of excavating tools and machine
Types of excavating tools and machineTypes of excavating tools and machine
Types of excavating tools and machine
 
Advance Construction equipment's reports
Advance Construction equipment's reports Advance Construction equipment's reports
Advance Construction equipment's reports
 
Dredging with THSD
Dredging with THSD Dredging with THSD
Dredging with THSD
 
Drag line excavator
Drag line excavatorDrag line excavator
Drag line excavator
 
earth moving equipments
earth moving equipmentsearth moving equipments
earth moving equipments
 
ppt%20act.pptx
ppt%20act.pptxppt%20act.pptx
ppt%20act.pptx
 
construction equipments.pptx
construction equipments.pptxconstruction equipments.pptx
construction equipments.pptx
 
13surface mining
13surface mining13surface mining
13surface mining
 
Civil Engineering Technology (Fawzan Fahry)
Civil Engineering Technology  (Fawzan Fahry)Civil Engineering Technology  (Fawzan Fahry)
Civil Engineering Technology (Fawzan Fahry)
 
Oc mechanical excavation
Oc mechanical excavationOc mechanical excavation
Oc mechanical excavation
 
Construction equipments - Introduction and Classification
Construction equipments - Introduction and ClassificationConstruction equipments - Introduction and Classification
Construction equipments - Introduction and Classification
 
building construction,ppt
building construction,pptbuilding construction,ppt
building construction,ppt
 
construction equipment
construction equipment construction equipment
construction equipment
 
Chapter-1 Introduction to Construction Equipments (1).pptx
Chapter-1 Introduction to Construction Equipments (1).pptxChapter-1 Introduction to Construction Equipments (1).pptx
Chapter-1 Introduction to Construction Equipments (1).pptx
 
Machineries and Maintenance Question Patterns for Mining students
Machineries and Maintenance Question Patterns for Mining studentsMachineries and Maintenance Question Patterns for Mining students
Machineries and Maintenance Question Patterns for Mining students
 
Construction equipment
Construction equipmentConstruction equipment
Construction equipment
 

Dernier

The basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxThe basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxheathfieldcps1
 
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxAUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxiammrhaywood
 
How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17Celine George
 
Benefits & Challenges of Inclusive Education
Benefits & Challenges of Inclusive EducationBenefits & Challenges of Inclusive Education
Benefits & Challenges of Inclusive EducationMJDuyan
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxDr. Santhosh Kumar. N
 
How to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesHow to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesCeline George
 
5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...CaraSkikne1
 
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxPISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxEduSkills OECD
 
Human-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesHuman-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesMohammad Hassany
 
Clinical Pharmacy Introduction to Clinical Pharmacy, Concept of clinical pptx
Clinical Pharmacy  Introduction to Clinical Pharmacy, Concept of clinical pptxClinical Pharmacy  Introduction to Clinical Pharmacy, Concept of clinical pptx
Clinical Pharmacy Introduction to Clinical Pharmacy, Concept of clinical pptxraviapr7
 
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfMaximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfTechSoup
 
Practical Research 1 Lesson 9 Scope and delimitation.pptx
Practical Research 1 Lesson 9 Scope and delimitation.pptxPractical Research 1 Lesson 9 Scope and delimitation.pptx
Practical Research 1 Lesson 9 Scope and delimitation.pptxKatherine Villaluna
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxraviapr7
 
Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.raviapr7
 
How to Make a Field read-only in Odoo 17
How to Make a Field read-only in Odoo 17How to Make a Field read-only in Odoo 17
How to Make a Field read-only in Odoo 17Celine George
 
UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE
 
Patterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxPatterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxMYDA ANGELICA SUAN
 
Quality Assurance_GOOD LABORATORY PRACTICE
Quality Assurance_GOOD LABORATORY PRACTICEQuality Assurance_GOOD LABORATORY PRACTICE
Quality Assurance_GOOD LABORATORY PRACTICESayali Powar
 

Dernier (20)

The basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptxThe basics of sentences session 10pptx.pptx
The basics of sentences session 10pptx.pptx
 
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptxAUDIENCE THEORY -- FANDOM -- JENKINS.pptx
AUDIENCE THEORY -- FANDOM -- JENKINS.pptx
 
How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17How to Add a many2many Relational Field in Odoo 17
How to Add a many2many Relational Field in Odoo 17
 
Benefits & Challenges of Inclusive Education
Benefits & Challenges of Inclusive EducationBenefits & Challenges of Inclusive Education
Benefits & Challenges of Inclusive Education
 
Finals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quizFinals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quiz
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptx
 
How to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 SalesHow to Manage Cross-Selling in Odoo 17 Sales
How to Manage Cross-Selling in Odoo 17 Sales
 
5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...5 charts on South Africa as a source country for international student recrui...
5 charts on South Africa as a source country for international student recrui...
 
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxPISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
 
Human-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesHuman-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming Classes
 
Clinical Pharmacy Introduction to Clinical Pharmacy, Concept of clinical pptx
Clinical Pharmacy  Introduction to Clinical Pharmacy, Concept of clinical pptxClinical Pharmacy  Introduction to Clinical Pharmacy, Concept of clinical pptx
Clinical Pharmacy Introduction to Clinical Pharmacy, Concept of clinical pptx
 
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdfMaximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
Maximizing Impact_ Nonprofit Website Planning, Budgeting, and Design.pdf
 
Practical Research 1 Lesson 9 Scope and delimitation.pptx
Practical Research 1 Lesson 9 Scope and delimitation.pptxPractical Research 1 Lesson 9 Scope and delimitation.pptx
Practical Research 1 Lesson 9 Scope and delimitation.pptx
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptx
 
Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.
 
Prelims of Kant get Marx 2.0: a general politics quiz
Prelims of Kant get Marx 2.0: a general politics quizPrelims of Kant get Marx 2.0: a general politics quiz
Prelims of Kant get Marx 2.0: a general politics quiz
 
How to Make a Field read-only in Odoo 17
How to Make a Field read-only in Odoo 17How to Make a Field read-only in Odoo 17
How to Make a Field read-only in Odoo 17
 
UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024
 
Patterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptxPatterns of Written Texts Across Disciplines.pptx
Patterns of Written Texts Across Disciplines.pptx
 
Quality Assurance_GOOD LABORATORY PRACTICE
Quality Assurance_GOOD LABORATORY PRACTICEQuality Assurance_GOOD LABORATORY PRACTICE
Quality Assurance_GOOD LABORATORY PRACTICE
 

Dredging

  • 3. WHAT IS DREDGING? Dredging is the term given to digging, gathering, or pulling out material to deepen waterways, create harbours, channels, locks, docks and berths, desilt lakes and keep river entrances and approaches to boat ramps clear. The material removed during dredging can vary greatly and can be any combination of rocks, clays, silts or sands.
  • 4. WHY DREDGING? To maintain the depth in existing ports, harbours and channels to provide ready and safe passage for commercial and recreational vessels. To create new or deeper access or berths for vessels. This may mean the deepening and widening of channels and anchorages as well as the excavation of basins and marinas from areas of previously dry land. To provide material for specific purposes, eg. beaches in coastal areas subject to erosion are sometimes ‘renourished’ with sand dredged from other areas. To bypass an artificial structure , such as a breakwater, that is an obstacle to the normal pattern of sediment movement along the coast. Dredging prevents a build up of material to be deposited down stream of the obstacle to allow the natural sediment transport process to occur. To place a structure inside water bodies
  • 5. DREDGING PROCEDURE Dredging procedure can be classified as:  Pretreatment,  Extraction and  Disposal.
  • 6. DREDGING PROCEDURE Pretreatment : Pretreatment means treatment of the ground before the dredging operations. It usually consists of a separate operation carried out independently of other dredging. There are two basic methods of pretreatment: chemical and mechanical and both are applied to rock or cemented soil.
  • 7. DREDGING PROCEDURE Extraction: The extraction process involves the movement of the spoil from its natural pretreated position into vertical transportation and its delivery to the transport system. Extraction processes are often a combination of at least two operations: the primary operation which disintegrates or dislodges the soil and the secondary operation which moves it. The first of these operations is performed either mechanically or hydraulically.
  • 8. DREDGING PROCEDURE Disposal : Disposal facilities are consist of bottom discharge, grab, scrapers, pipelines, land based unit, natural processes.
  • 9. DIFFERENT TYPES OF DREDGING Dredging can be classified as: 1. Mechanical Dredging 2. Hydraulic Dredging
  • 10. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Mechanical dredging involves removal of material by a bucket, placement of the material in a scow or on a barge, and towing that scow or barge to a disposal or transfer area.
  • 11. DIFFERENT TYPES OF DREDGING Mechanical Dredging: oIf a scow is used with open water disposal, the doors would open at the disposal site, releasing the material to fall through the water column to the bottom. oIf a scow or barge is used with any other type of disposal, it would be towed to the disposal or transfer site where another bucket machine would remove the material from the scow or barge and transfer it onto a vehicle or directly into a near shore disposal area.
  • 12. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Aerial view of Mechanical Dredging
  • 13. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Aerial view of Mechanical Dredging
  • 14. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Dredged materials being pulled out
  • 15. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Dredged materials are being stored on a barge
  • 16. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Dredged materials being transported to disposal area
  • 17. DIFFERENT TYPES OF DREDGING Mechanical Dredging: Dredged materials being disposed
  • 18. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Hydraulic pipeline dredging involves use of a hydraulic (suction) dredge, most commonly for either beach nourishment of suitable sands, or deposit into an upland containment area (for dewatering or direct disposal).
  • 19. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Hydraulic dredging provides the cleanest and least obtrusive method for sediment removal without damaging the sensitive environment.
  • 20. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Typically the dredge uses a cutter head on the end of the suction arm to loosen the material while the dredge pump suctions the loosened material through the arm to the pump in a slurry of about 75 to 90 percent water and 10 to 25 percent sediment. The slurry is pumped through a pipeline to a disposal site or dewatering/transfer area.
  • 21. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: A hydraulic dredge floats on the water and excavates and pumps the material through a temporary pipeline to an offsite location, often several thousand feet away. This dredge acts like a floating vacuum cleaner that can remove sediment very precisely.
  • 22. DIFFERENT TYPES OF DREDGING Hydraulic Dredging:
  • 23. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Dredge is dropped into the water using a crane
  • 24. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Aerial view of barge with hydraulic dredging equipment removing ash from the navigation channel
  • 25. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Ash and water are pumped though this pipeline
  • 26. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Relay pump in the middle of the pipeline
  • 27. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Ash and water discharge into holding area . Sediment can then be de-watered and either replanted or trucked off location.
  • 28. DIFFERENT TYPES OF DREDGING Hydraulic Dredging: Ash and water discharge into holding area . Sediment can then be de-watered and either replanted or trucked off location.
  • 29. Types of Dredgers According To Dredging Types Dredgers Are Divided Mainly Into Two Kinds: 1. Mechanical Dredgers 2. Hydraulic Dredgers
  • 30. Types of Dredgers In the Mechanical Dredgers material is conveyed By mechanical contravenes, whereas, in the Hydraulic Dredgers, it is conveyed by water through pipes. They are further classified under various principal types, depending on their mode of operation.
  • 31. Mechanical Dredgers (i) Bucket or Grab Dredger: It is essentially a stiff-leg derrick on a floating platform. By means of a derrick arrangement it lowers an open grab bucket onto the material, fills it there and lifts it. The material is either deposited alongside the channel, or dumped in barges or in hoppers provided on the dredger.
  • 32. Mechanical Dredgers (i) Bucket or Grab Dredger:
  • 33. Mechanical Dredgers (i) Bucket or Grab Dredger:
  • 34. Mechanical Dredgers (i) Bucket or Grab Dredger:
  • 35. Mechanical Dredgers (i) Bucket or Grab Dredger: Mechanical dredgers work best in consolidated, or hard packed materials and can be used to clear rocks and debris. The advantage of the bucket dredger lies in its ability to work in small areas inaccessible to other types of dredgers. It is efficient in homogeneous materials, particularly in stiff mud.
  • 36. Mechanical Dredgers (i) Bucket or Grab Dredger: The digging power of the bucket depends on its weight and its effect is diminished by the lifting tendency of the closing wire. It dose not have sufficient penetration power to obtain a full load in harder material, compacted sand, gravel and clay. Sometimes, the bucket spins twisting the opening and closing wires; the operation is stopped till they are straightened out, resulting in much loss of time.
  • 37. Mechanical Dredgers (ii) Dipper Dredger: • The dredger consists of a floating power shovel, and except for the digging equipment, it is same a bucket dredger. • It should be used only if the material is resistant such as soft rock, boulders’ material consisting of timber etc. • Its unit cost of dredging is higher than for other dredgers.
  • 39. Mechanical Dredgers (iii) Ladder Dredger: • This consists of buckets attached at each end of the frame. • It is suitable to excavate cohesive materials. • These dredgers are used even with self-contained hoppers. When hoppers are not provided, scow (flat-bottom boats) are required to dispose of dredged materials.
  • 40. Mechanical Dredgers (iii) Ladder Dredger: • In river and harbors works, this dredger is suitable for digging stiff, hard and non-homogeneous materials; loose sand and soft mud tend to wash out of the buckets reducing its efficiency for these materials. • This dredger is extensively used in Europe and in the Suez Canal.
  • 42. Mechanical Dredgers (iv) Hopper Dredger: • A self-contained and self-propelled hopper dredger is provided with either a bucket or a dipper. • But its drawback is that a self-contained hopper arrangement generally makes the draft excessive and it cannot be used for shallow dredging. • With this dredger, however, material can either be dumped alongside the channel to be dredged, or in any place where it is required or where it can be carried away by the stream.
  • 44. Mechanical Dredgers (v) Rock Dredger: • Formerly, when rock had to be removed, the materials was broken by blasting, and removed by bucket dredgers. • Of late, where rook is soft, it is removed by means of strong steel claws; where it is hard, it is broken up by the use of heavy rams. • The rock outers have the form of heavy chisel pointed rams, which after being raised, are allowed to drop 3 to 6 m. (10 to 20 ft.) on the rock. • With rams of sufficient weight, hardest rocks can be broken up. The debris is removed by grab.
  • 46. HYDRAULIC DREDGERS (i)Plain Suction Dredger: • This is the simplest hydraulic floating dredger with a centrifugal pump and auxiliary equipment mounted in the hull. • The size and type of the hull depends on the size of the pump used and the amount of power needed to operate the equipment. • The size of the dredger is generally described by the diameter of the discharge pipe, which ranges from 15.2 to 76.2cm (6 to 30inch).
  • 49. HYDRAULIC DREDGERS (ii) Cutter Head Dredger: • It is similar to the suction dredger, except that it has a rotary cutter head which carves clay, breaks off chunks of softer rocks such as coral and shale, and stirs up gravel and sand so that pipe carries material to its capacity. • This dredger is being suitable for channel work, cut-offs, new construction, harbor excavation and making fills.
  • 51. HYDRAULIC DREDGERS (iii) Dust-pan Hydraulic Dredger: • These dredgers are similar to the cutter head pipe line dredge except that in the former horizontally spread suction heads, similar to a dust-pan or a vacuum cleaner nozzle, are employed. • Instead of a rotary cutter, high velocity water jets are mounted in the suction head to loosen the material.
  • 52. HYDRAULIC DREDGERS (iii) Dust-pan Hydraulic Dredger: • The suction head may be as wide as 9.7 m. (32ft.) and is provided with nozzles, through which water is pumped at 1.8 kg. /sq. cm. (25 1b./sq. in. ) to agitate the material so that it can be more easily picked up. • This dredger is commonly used on the Mississippi River for the maintenance of navigation channels.
  • 53. HYDRAULIC DREDGERS (iii) Dust-pan Hydraulic Dredger:
  • 54. HYDRAULIC DREDGERS (iv) Hopper Dredger Hydraulic Type: • It is equipped to operate as an anchorless hydraulic dredger for transporting and dumping the excavated material without the assistance of auxiliary plant such as tugs, barges, etc. • This dredger is capable of operating in rough water where pipe line dredgers are unsatisfactory because of the breaking of the pipe line.
  • 55. HYDRAULIC DREDGERS (iv) Hopper Dredger Hydraulic Type:
  • 56. HYDRAULIC DREDGERS (iv) Hopper Dredger Hydraulic Type: • It is particularly suitable in busy and crowded harbors, whereas pipe line dredgers, with their long anchor cables and pipe lines, occupy much space and are slow, impeding harbor traffic. • The principal elements of the hopper dredger are the pump, the drag hoist and hopper bins.
  • 57. HYDRAULIC DREDGERS (iv) Hopper Dredger Hydraulic Type:
  • 58. Dredging and River Bank Protection • Dredging is getting popular day by day as a means of river training work to improve the navigational depth as well as attain channel. stabilization Focus of Interest
  • 59. Dredging and River Bank Protection Stabilization Leads to State of Equilibrium Very difficult Protected River Bank to Attain
  • 60. Dredging and River Bank Protection • The combined use of dredging, dikes and the disposal of dredged material in the dike fields can introduce major changes in the cross sectional characteristics of a river. • The dredging and contraction reduce the width-to- depth ratio of a river upto an extent. • They increase the channels capacity for transport of suspended portion of bed material. • It decreases the capacity for transport of bed load.
  • 61. Dredging and River Bank Protection • Dredging can significantly altered river characteristics when employed as an agent for morphologic changes in support of engineering requirements for river system development. • Dredging and open water disposal of dredged material in support of channel maintenance implies the moving of alluvial sediments from the mail channel or thalweg region toward the periphery of the channel.
  • 62. Dredging and River Bank Protection • This continued lateral redistribution of sediments not only interrupts the natural downstream movement of sediment in a system but also affects the local channel morphology.
  • 63. Dredging and River Bank Protection • The lateral redistribution of sediment by dredging combined with the contraction works not only affect the local channel morphology but indirectly retards the movement of bed load through the system.
  • 64. Dredging and River Bank Protection Channel Morphology Change in Behavior DREDGING Sediment Movement Needs Extensive Hydraulic behavior Research of Channel
  • 65. Dredging To Deepen Critical Sections
  • 66. Dredging To Deepen Critical Sections
  • 67. IMPACTS OF DREDGING Dredging activities have the potential to change the environment. At the sites of dredging and disposal the seabed and associated communities are disturbed and for some distance, suspended sediment may cause turbidity in water and increased sedimentation on the bottom. Depending upon the nature of the dredged material, its disturbance from the sea bed may lead to changes in the chemical composition of the water.
  • 68. IMPACTS OF DREDGING As well as toxicants, the nutrient elements, particularly nitrogen and phosphorus, which control the rate of marine plant growth can also be released from sediments during dredging, with a risk of triggering algal blooms. Another biological risk from dredging involves the transport of species in dredgers from one port (or even country) to another.
  • 70. MORPHOLOGICAL AND HYDRAULIC RESPONSE DUE TO DREDGING • Dredging effects the morphological and hydraulic behaviour of a channel section. • Due to initial deepening or capital dredging of a channel, the river bed is degraded until the balance between the sediment load supplied to the river reach and the sediment transport capacity of the flow is restored.
  • 71. MORPHOLOGICAL AND HYDRAULIC RESPONSE DUE TO DREDGING • In the long term the result will be degradation to a more gentler slope and a greater depth downstream of the point of dredging. • Degradation will also occur in upstream which leads to lowering of river bed with initial slope.
  • 72. Dredging in Bangladesh • Two types of dredging are conducted in Bangladesh: Capital Dredging (Example: Gorai River Project by BWDB) Maintenance Dredging (Example: Paturia and Daulatdia Ferry Ghats by BIWTA)
  • 74. Dredging in Bangladesh Gorai river project: Aerial view of the cutter suction dredger at work in Gorai river project
  • 75. Dredging in Bangladesh Gorai river project: Aerial view of the cutter suction dredger at work in Gorai river project
  • 76. Dredging in Bangladesh Gorai river project: Aerial view of the cutter suction dredger at work in Gorai river project
  • 77. Dredging in Bangladesh Gorai river project: The dredging continues in Gorai river project