MY WATER RESOURCES ENGINEERING TERM PAPER

1. DREDGING PROCESS AND ITS EFFECT
PRESENTED BY INDRANIL BANERJEE
ROLL NUMBER- 001930301008
DEPARTMENT OF WATER RESOURCES ENGINEERING
JADAVPUR UNIVERSITY
2ND SEMESTER, SPRING 2020

2. CONTENTS
• INTRODUCTION
• NECESSITY
• TYPE OF DREDGER
• MECHANICAL DREDGERS
• BUCKET LADDER DREDGER
• GRAB DREDGER
• BACKHOE DREDGER
• HYDRALIC DREDGERS
• SUCTION HOPER DREDGER
• CUTTER SUCTION DREDGER
• TRAILING SUCTION HOPPER DREDGER
• SITE INVESTIGATION
• VERIOUS SURVEYING
• CASSIFICATION OF SOILS
• DREDGER SELECTION
• DUMPING GROUNDS
• FIELD SURVEY
• EFFECTIVENESS
• IMPACT
• OPERATION AND MAINTENANCE STATUS
• ENVIRONMENTAL EFFECT OF DREDGING
• CONCLUSION
• REFERENCES

3. INTRODUCTION
• it is the subaqueous or
underwater excavation of soils
and rock. The process consists of
four phases:
 Excavation
 Vertical transport
 Horizontal transport
 Placement or use of the material
dredged.
 A dredgers is a piece of
equipment which can dig,
transport and dump a certain
amount of under water laying soil
in a certain time. The quantity of
soil moved per unit of time is
called Production.

4. NECESSITY
• to create a new harbor, berth or
waterway, dredging is to be done
mandatory
• Sea bed mining is also an
important part where dredging is
being done
• affected by chemical spills
• underwater foundation works for
bridge piers requires dredging to
be carried out.
• To maintain navigable waterways,
• Construction and Reclamation
• Beach nourishment
• Environmental remediation
• Flood control
• Mining

5. TYPES OF DREDGER
• Depending upon the
method used to
transport loosened
material from the sea-
bed to the surface
they may be classified
as:
a) Mechanical dredgers
b) Hydraulic dredgers
c) Other types
Mechanical dredgers
Hydraulic dredgers

6. MECHANICAL DREDGERS.
• a) Bucket ladder dredger
• b) Grab dredger
• c) Backhoe/dipper dredger

7. BUCKET LADDER DREDGER

8. WORKING METHOD

9. BUCKET LADDER DREDGER
PARAMETER

10. GRAB DREDGER

11. VARIOUS TYPE OF GRAB

12. BACKHOE DREDGER

13. HYDRAULIC DREDGERS
•a) Profile or plain suction dredger
1.Barge Loading suction dredger
2.Standard plain suction dredger
3.Deep suction dredger
•b) Cutter suction dredger
•c) Trailing suction hopper dredger

14. SUCTION HOPER DREDGER

15. CUTTER SUCTION DREDGER

17. TRAILING SUCTION HOPPER DREDGER

18. SITE INVESTIGATION
1. Characterization of the material to be dredged
2. Determination of the total volume to be dredged
3. Topographic Survey for shore controls land areas
reclamation
4. The hydrographic of the dredging and disposal
locations
5. Bathymetric surveys to determine bed levels
6. Geotechnical investigations to assess the nature of the
material
7. Geo-physical investigations
8. Environmental surveys_Geo-physical investigations
Meteorological Oceanographic

19. • Topographic Survey
Bathymetric surveysTopographic Survey
Multi Beam Echo Sounder survey
single Beam Echo Sounder survey
Magnetometer Surveys
VERIOUS SURVEY IMAGE

20. CASSIFICATION OF SOILS
• In order to form an opinion as to the most suitable equipment
for dredging under water, and to estimate performance of
dredging equipment, it is vital to know the nature, location,
transportation and disposal quantities of materials to be
dredged. The soil classifications as per Indian Standards .

21. DREDGER SELECTION
ideal dredge varies between dredging projects.
Dredge selection depends on availability and cost,
and various physical characteristics

22. DUMPING GROUNDS
• The effects of the disposal of such wastes include the
physical blanketing of the bottom. In addition, these
spoils may be contaminated with heavy metals, oil,
or oreganos chlorine compounds, causing adverse
effects on fish populations and marine biology.

23. TUTICORIN PORT DREDGING PROJECT
Field Survey: August 2003
Objectives
The project’s objectives were to alleviate draught*3 restrictions by dredging port water and approach channels at Tuticorin
Port in southern Tamil Nadu, and to improve the efficiency of port operations by increasing per vessel payload, and thereby
contribute to economic growth in the state.
Outputs
The outputs of this project were as follows:
1) Dredging of approach channel
· Dredged sand volume: 580K m3
· Channel length: 2.7km (currently 1.4km)
· Channel width: 183m (virtually identical to current width)
· Design water depth: 12.5m (currently 10.2-11.4m)
2) Dredging of harbor basin
· Dredged sand volume: 1.22m m3
· Diameter of basin: 688m
Dredging to increase water depth of zones fronting individual berths (Berth VII, etc.)
· Design water depth: 11.9m (current depth of basin: 10.6m; current depth of other frontal water zones: 9.5m-11.3m)
3) Vessel types targeted
· Bulk (dry) cargo vessels: length 230m × width 32.5m × draught 10.7m
· Bulk (liquid) cargo vessels: length 235m × width 32.5m × draught 10.7m
· Container vessels: length 220m × width 30.0m × draught 10.7m
4) Civil engineering works
· Dredger model: Cutter suction dredger
· Dredge sand disposal: to be dumped in two dumping grounds within port precincts
Shore protection of areas peripheral to the dumping grounds
· Other works: greening/planting port areas

25. EFFECTIVENESS
• Changes in Cargo Handling Volumes, etc.
• Indices relating to the operational efficiency of the port prior to
and after the implementation of the project (shaded sections
represent the actual implementation period) are as shown
below

27. Impact
• Initially Projected Impacts- port carriers have
become more active.
• Environmental Impacts - A report was obtained
via the fishery company also contains no adverse
impacts on the fishery industry.
• Other Socioeconomic Impacts (effects on local
residents) Other Impacts
• the volume of trade – increased rapidly from 59
thousand tons in fiscal 1999 to 326 thousand tons
in fiscal 2001 (i.e. an increase of approximately
5.5 times), since larger vessels can be used now
because of the dredging work.

28. Operation and Maintenance Status
• 1.Tuticorin Port receives physiographic protection from Sri
Lanka, and because of its structure, accumulation of sand
due to tides and winds is difficult, and (2) the bedrock on
the ocean floor is very hard and this is not a river port.
Therefore dredging is not generating any maintenance
costs.
• To summarize the above, the project succeeded in securing
the planned water depths in the approach channel and
harbor basin, and the port is functioning as expected.
• Moreover, no maintenance costs are being generated since
no special work is necessary to maintain the water depth
thanks to the port’s geographical advantages. The
executing agency is not facing any particular problems
either organizationally or financially, and the overall
sustainability of the project is deemed to be high.

29. ENVIRONMENTAL EFFECT OF DREDGING
 Development projects have some common problems
related to the environment. The primary categories
can be summarized as being__
Water-Related Effects(sattlement,blasting ,altered
bathymetry, changing shoreline
Land-Related Effects(dust and other airborne
emissions)
Air-Related Effects(especially hydrogen sulphides)
Placement of Dredged Material(Material
contamination)
Socio-cultural Effects(work practices, site selection)

30. CONCLUSION
• it can be stated that every type of dredger has its own
applied working area in which its production is
optimal in a technical way as well as in an
economical way. It will be clear that the boundaries
of these applied working areas are not strictly
determined, but are also determined by other working
conditions, which can differ from lob to job. In order
to accomplish dredging process ,different survey,
dredger selection, and environmental impact need to
be calculated, through the proper dredger selection.

31. REFERENCES
• 1.>http://sagarmala.gov.in/sites/default/files/dredgeguidelinesAugust2016-30146365.pdf
•
• 2.>https://www.jandenul.com/sites/default/files/activity-category/brochures/Dredging_and_Marine_Works.pdf
•
• 3.>https://www.damen.com/-/media/Products/Images/Clusters-
groups/Dredging/Documents/Brochure_Damen_Dredging.pdf
•
• 4.>https://www.researchgate.net/publication/271443986_Dredging_Processes_The_Loading_Process_of_a_Traili
ng_Suction_Hopper_Dredge_Lecture_Notes
•
• 5.>https://www.engr.colostate.edu/~pierre/ce_old/classes/ce717/2_OverviewofDredgingandDMD_Welp.pdf
•
• 6.>https://www.epa.vic.gov.au/~/media/Publications/691.pdf
•
• 7.> http://bit.ly/2XTuGoq
•
• 8.> http://www.fao.org/docrep/013/i1883e/i1883e06.pdf
•
• 9.> https://nptel.ac.in/courses/114106035/
•
• 10.> http://www.imcbrokers.com/blog/overview/detail/types-of-dredgers
•
• 11.> https://dredging.org/documents/ceda/downloads/vlasblom1-introduction-to-dredging-equipment.pdf

32. THANK YOU