concept of operation: unmanned maintenance dredging · 2018. 11. 23. · dredging gabriel pereira...

Concept of Operation: Unmanned Maintenance Dredging

Gabriel Pereira Perdigao

Master Thesis

presented in partial fulfillment

of the requirements for the double degree:

“Advanced Master in Naval Architecture” conferred by University of Liege

"Master of Sciences in Applied Mechanics, specialization in Hydrodynamics,

Energetics and Propulsion” conferred by Ecole Centrale de Nantes

developed at West Pomeranian University of Technology, Szczecin

in the framework of the

“EMSHIP” Erasmus Mundus Master Course

in “Integrated Advanced Ship Design”

EMJMD 159652 – Grant Agreement 2015-1687

Supervisor:

Dr. Maciej Taczała, West Pomeranian University of

Technology, Szczecin

Reviewer: Prof. Robert Bronsart, University of Rostock

Szczecin, February 2018

P2 Gabriel Perdigao

Master Thesis developed at West Pomeranian University of Technology, Szczecin

Concept of Operation: Unmanned Maintenance Dredging P3

“EMSHIP” Erasmus Mundus Master Course, period of study September 2016 – February 2018

Declaration of Authorship

I declare that this thesis and the work presented in it are my own and have been generated by

me as the result of my own original research.

Where I have consulted the published work of others, this is always clearly attributed.

Where I have quoted from the work of others, the source is always given. With the exception of

such quotations, this thesis is entirely my own work.

I have acknowledged all main sources of help.

Where the thesis is based on work done by myself jointly with others, I have made clear exactly

what was done by others and what I have contributed myself.

This thesis contains no material that has been submitted previously, in whole or in part, for the

award of any other academic degree or diploma.

I cede copyright of the thesis in favour of the University of …..

Date: Signature

P4 Gabriel Perdigao




List of Figures Figure 1 - Volume maintenance dredging a year in the Botlek area. Retrieved September 07,

2017 from Source: (3) ............................................................................................................... 18

Figure 2 - River and Sea influence in Port Area. Retrieved September 01, 2017 from Source:

(1) .............................................................................................................................................. 19

Figure 3 - Sea Influence in Port Area. Retrieved September 01, 2017 from Source: (1) ......... 19

Figure 4 - Criteria diagram for dredging device. Source: Author ............................................. 20

Figure 5 – Sediment transport processes. Retrieved December 10, 2017 from Source: (4) ..... 22

Figure 6 - Vertical profiles of cohesive sediment concentration and velocity. Retrieved

December 10, 2017 from Source: (4) ....................................................................................... 24

Figure 7 - Soil consistencies and Attenberg limits. Retrieved December 10, 2017 from Source:

(9) .............................................................................................................................................. 25

Figure 8 - Casagrande's plasticity chart. Retrieved December 10, 2017 from Source: (11) .... 25

Figure 9 - Rheological models. Retrieved December 10, 2017 from Source: (12) .................. 26

Figure 10 – Geographical breakdown open dredging market in 2015. Retrieved September 17,

2017 from Source: (16) ............................................................................................................. 28

Figure 11 - Dredging divided by end-market in 2011 (EUR). Retrieved September 17, 2017

from Source: (15) ...................................................................................................................... 29

Figure 12 - Top 10 Dredging contractors by country - Graphic Representation. Source: Author

................................................................................................................................................... 31

Figure 13 - Levels of Autonomy with emphasis on human interaction. Retrieved September 04,

2017 from Source: (23) ............................................................................................................. 44

Figure 14 - Levels of Autonomy proposed by Sheridan. Retrieved September 04, 2017 from

Source: (24) ............................................................................................................................... 44

Figure 15 -- Dredger discharging material in the sea. Retrieved September 06, 2017 from

Source: (2) ................................................................................................................................. 46

Figure 16 - Schematic of Grab Hopper Dredger. Retrieved August 31, 2017 from Source: (43)

................................................................................................................................................... 48

Figure 17 - Schematic of Backhoe Dredger. Retrieved August 31, 2017 from Source: (44) ... 48

Figure 18 - Schematic of Bucket Ladder Dredger. Retrieved August 31, 2017, from Source:

(45) ............................................................................................................................................ 49

Figure 19 - Schematic of Plain Suction Dredger. Retrieved September 01, 2017 from Source:

(46) ............................................................................................................................................ 50

P6 Gabriel Perdigao


Figure 20 - Schematic of Cutter Suction Dredger. Retrieved September 01, 2017 from Source:

(47) ............................................................................................................................................ 50

Figure 21 – Schematic of Trailer Suction Hopper Dredger. Retrieved September 01, 2017 from

Source: (48) ............................................................................................................................... 51

Figure 22 - Schematic of Water Injection Dredger. Retrieved September 01, 2017 from Source:

(49) ............................................................................................................................................ 52

Figure 23 - Example of Water Injection Dredger. Retrieved September 01, 2017 from Source:

(50) ............................................................................................................................................ 52

Figure 24 – Risk distribution between contractor and employer for each type of contract.

Retrieved November 22, 2017 from Source: (1) ...................................................................... 53

Figure 25 - Illustration of the stability of bottom-heavy (left) and top-heavy (right) ships with

respect to the positions of their centres of buoyancy (CB) and gravity (CG). Retrieved

November 29, 2017 from Source: (52) ..................................................................................... 55

Figure 26 - Representation of COLREG parts. Retrieved September 15, 2017 from Source: (63)

................................................................................................................................................... 66

Figure 27 - The Autonomous Ship, as it understood in the MUNIN project, is a symbiosis of

the Remote Ship and the Automatic Ship. Retrieved December 04, 2017 from Source: (64) . 67

Figure 28 - MUNIN's concept to solve the Unmanned Navigation. Retrieved December 04,

2017 from Source: (64) ............................................................................................................. 67

Figure 29 - Yara Birkeland projection. Retrieved December 04, 2017 from Source: (65) ...... 68

Figure 30 – Scale model of the final design of the autonomous vessel. Retrieved December 04,

2017 from Source: (66) ............................................................................................................. 69

Figure 31 - The ReVolt DNV G Lateral view. Retrieved December 04, 2017 from Source: (67)

................................................................................................................................................... 70

Figure 32 - The ReVolt DNG GL Back view. Retrieved December 04, 2017 from Source: (67)

................................................................................................................................................... 70

Figure 33 - Remote Operating Centre designed by Rolls-Royce view 1.Retrieved December 05,

2017 from Source: (68) ............................................................................................................. 72

Figure 34 - Remote Operating Centre by Rolls-Royce view 2. Retrieved December 05, 2017

from Source: (68) ...................................................................................................................... 72

Figure 35 - DARPA Sea Hunter concept. Retrieved December 12, 2017 from Source: (72) .. 73

Figure 36 - DARPA Sea Hunter view. Retrieved December 12, 2017 from Source: (73) ....... 73

Figure 37 – Base Principles of Water Injection Dredging. Retrieved December 10, 2017 from

Source: (1) ................................................................................................................................. 74



Figure 38 - Concept schematic for autonomous water injection dredger. Source: Author ....... 75

Figure 39 – Concept schematic for autonomous suction dredger. Source: Author .................. 76

Figure 40 - Concept schematic for autonomous submerged dredger with floating hopper.

Source: Author .......................................................................................................................... 77

Figure 41 – General Arrangement for AWID - Lateral view. Source: Author ......................... 86

Figure 42 – General Arrangement for AWID – Superior view. Source: Author ...................... 86

Figure 43 – Mud sedimentation scheme in harbour basin next to sea. Source: Author ........... 89

Figure 44 - Waypoint mode representation. Source: Author .................................................... 90

Figure 45 - Autonomous mode representation. Source: Author ............................................... 91

Figure 46 - Swarm mode representation. Source: Author ........................................................ 92

P8 Gabriel Perdigao


List of Tables Table 1 - List of dredging companies by country. Source: Author .......................................... 31

Table 2 - Final results for the multi-criteria analysis. Source: Author ..................................... 81

Table 3 - Main data for AWID concept. Source: Author ......................................................... 83

Table 4 - Overview of WID dredgers as per June 2010. Adapted from PIANC (1). Source:

Author ....................................................................................................................................... 85

Table 5 - Production rates during WID projects. Retrieved December 10, 2017 from Source:

(1) .............................................................................................................................................. 87

P10 Gabriel Perdigao


Contents ListofFigures..........................................................................................................................................5

ListofTables............................................................................................................................................8

1. Introduction..................................................................................................................................14

1.1. Motivation.............................................................................................................................14

1.2. MasterThesisStructure........................................................................................................16

2. ProblemDescription......................................................................................................................17

2.1. MaintenanceDredgingandSedimentation..........................................................................17

2.2. Requirementsfordredgingdevice........................................................................................19

2.3. Mudcharacteristics...............................................................................................................21

2.3.1. Classificationandcompositionofmud.........................................................................21

2.3.2. Mudappearanceinwatercolumn................................................................................23

2.3.3. Plasticityindexandwatercontent................................................................................24

2.3.4. Rheology........................................................................................................................26

2.3.5. Consolidation.................................................................................................................27

3. FeasibilityStudy.............................................................................................................................27

3.1. Marketresearchstudy..........................................................................................................27

3.2. Technical&OperationalFeasibility.......................................................................................32

3.3. LegalFeasibility.....................................................................................................................33

3.4. FinancialFeasibility................................................................................................................34

4. Stakeholders..................................................................................................................................34

4.1. Definingthestakeholders.....................................................................................................34

4.2. Stakeholdersanalysis............................................................................................................36

5. LiteratureReview..........................................................................................................................43

5.1. Human-RobotInteractionandLevelofAutonomy...............................................................43

5.2. Dredging................................................................................................................................45

5.2.1. Definition.......................................................................................................................45

5.2.2. Historical........................................................................................................................46

5.2.3. TypesofDredgingworks...............................................................................................47

5.2.4. Dredgingmethods.........................................................................................................47

5.2.5. TypesofContract..........................................................................................................52

5.3. ShipStability..........................................................................................................................54

5.4. MarinePropulsion.................................................................................................................57

5.5. ShipMaintenance..................................................................................................................64



5.6. Mooring.................................................................................................................................64

5.7. CollisionAvoidanceatSea.....................................................................................................65

6. OverviewofUnmannedVessels....................................................................................................66

6.1. Initiativesandresearchesunderdevelopment.....................................................................66

6.1.1. MUNINProject..............................................................................................................66

6.1.2. YaraBirkeland................................................................................................................68

6.1.3. TheReVolt.....................................................................................................................69

6.1.4. AdvancedAutonomousWaterborneApplicationsInitiative(AAWA)...........................70

6.1.5. DARPASeaHunterUnmannedSurfaceVehicle............................................................72

7. Conceptofoperations...................................................................................................................74

7.1. Comparisonofconcepts........................................................................................................74

7.1.1. Autonomouswaterinjectiondredgingdevice..............................................................74

7.1.2. Autonomoussuctiondredgingdevice...........................................................................75

7.1.3. Autonomoussubmergedwalkingdredgerwithfloatinghopper..................................77

7.2. ConceptchoicebyMulti-criteriaanalysis..............................................................................78

7.3. Firstdesign............................................................................................................................81

7.3.1. MainparticularsforAutonomousWaterInjectionDredging........................................82

7.3.2. Propulsionchoice..........................................................................................................83

7.3.3. CurrentWIDfleetbyPIANC...........................................................................................84

7.3.4. GeneralArrangement....................................................................................................85

7.4. Productioncapacityestimation.............................................................................................86

7.5. Operationalconcept..............................................................................................................88

7.5.1. Operatingmodes...........................................................................................................90

8. Conclusions...................................................................................................................................93

9. References.....................................................................................................................................95



ABSTRACT

The term autonomous and unmanned ship comprises many different approaches having

advantages and disadvantages depending on the point of view adopted. Some studies written

about the topic show few applications that are in operation nowadays. Most of all are small-

unmanned surface vessels collecting data and performing hazardous tasks in a variety of

difficult areas to access. Moreover, there are several potential local applications for unmanned

navigation such as dredging, firefighter crafts, tugboats, fishing vessels, ferries, skimmer boats

and even fully autonomous submarines. On the one hand, we have stakeholders who are putting

a lot of effort to make it real and they state that we are ready to go to the next level; however,

on the other hand, some are sceptical about crewless ships and how they will affect the marine

industry. Overall, this study go through technical, regulatory and economical challenges

regarding the possibilities for using an unmanned vessel to emulate the current ship operational

mode and somehow improve the whole process to convince the stakeholders to put their money

on it. The outcome intended to become a solid material for further discussions to make

unmanned operation a reality.

Keywords: unmanned, autonomous, crewless, dredging, water injection.



1. Introduction

1.1. Motivation

The terms autonomous and unmanned vessels seem to be the same, passing unnoticed to

the audience not used to the words in question. In general, autonomous means the system has

certain or even full autonomy to take decisions based on knowledge acquired from a complex

algorithm. It can promptly choose for example, what is the best path or speed, avoid collision

by detecting any move not compliant with COLREGS, even inform how the maintenance

routine is or if any failure detected and how to solve it. On the other hand, unmanned navigation

means explicitly that no one will be on board, however it is possible to have an unmanned vessel

guided by cables or even towed by a pushing boat, and for those there is no need to deploy an

autonomous architecture.

Considering that, 70% of the earth’s surface is covered by water and we can send and

bring back people from the space in safety, people should not overreact when the term

unmanned is discussed among the stakeholders. Many experts state that today we must say

WHEN rather than IT when we talk about vessels going on sea without anyone on board. There

are several common-sense advantages to going crewless, although there are also real

disadvantages for our society in a long term.

Nowadays, the most prominent use for unmanned operation is found in military and ocean

survey with small to medium crewless surface vehicles built in with systems capable of take

certain decisions and when the system cannot decide what to do, one can take over control the

vessel and operate it by remote control. Concepts planning to go further and merge technology

and new efficient ways to transport goods, people and support to dangerous tasks are the initial

motivation to think that marine industry can overcome the label of antiquated and conservative

among others means of transportation.

The main reason behind this piece of work is to find gaps in applications and propose a

new concept for traditional solutions to replace current vessels into units that can work

autonomously for a fraction of money deployed today. Although, in theory the one can only see

advantages of using ships without crew, it is necessary to bear in mind that there are dozens of

stakeholders involved and is not simple to persuade them to buy the idea of something

innovative. In an analogical manner, it is possible to mention many examples the society has

technology to go further but due to constraints prefer going conservative even though the

method used is more expensive, slower and less efficient.



Many applications aroused the interest before defining one, and the type chosen, which

may not be the most adequate if seen by a different point of view. It demonstrates features and

potential, fitting the scope regarding unmanned navigation. Following this chain of though, the

application chosen is a dredging vessel. This type of vessel has a considerable level of

automation and their demand is for very specific jobs. Today, those tasks are performed for

large and costly ships, which need to be deployed periodically in locations where a port basin,

waterway suffers from sedimentation.

Opportunity Definition

Some development in the field of autonomous ships are undergoing at a slow pace,

however many are betting that today is possible to state WHEN rather than IF about crewless

crafts. Following this idea, unmanned dredging vessels emerge as an opportunity to replace

large vessels into smaller ones that are permanently available and able to remove sediments in

all conditions.

Today, dredging focus on high production to compensate the elevated costs of operation,

working as less as possible and dredging as much as possible material to save resources,

including fuel and workforce. Developments in the autonomous systems can change how the

dredging projects contracted and executed.

For this reason, an opportunity to use small and inexpensive dredging devices are treated

in this report. A lot of effort is put into this work by detailing possibilities and merging

knowledge about existing techniques and new developments.

The thesis is based on opportunities seen from the field and questions must be asked to

select the right scope for the project. Below is possible to see how the problem is defined and

what the boundary conditions for this work are:

• Why dredging companies would be interested in removing sedimentation using an

unmanned device?

• What are the existing current techniques used by traditional dredging vessels?

• What would be the most prominent method to develop an inexpensive and small

dredging vessel?



• What are the possibilities for removing sediments and widening ports and waterways?

• How big should it be?

• Is it possible to add other features to this vessel and become it into a multi-purpose?

• Is it possible to power the vessels by renewable energy?

• Is it feasible to replace large dredging vessels by multiple small autonomous ones?

The questions above are the foundations to determine the constraints for the scope of the

research:

1. The device should have the main particulars appropriate for the application.

2. The device should use efficient techniques to remove material from a determined area.

3. The device should be to operate autonomous or remote controlled by a shore control

centre.

4. It should be able to operate along the coast (ports and waterways).

5. It should be able to dredge layers of mud.

6. The vessel must have a low maintenance budget.

7. Energy efficient must be considered and a solution based on renewable energy is

preferred

8. It should be ready to attach equipment to exert further complementary applications.

1.2. Master Thesis Structure

The piece of work initially covers in chapter 1, the motivation behind the willing to do

this research, what are the opportunities regarding this type of vessel, defining the constraints

the project must follow to become something feasible and appeal the stakeholders to buy it.

In chapter 2, the problem describes what kind of dredging proposition is acceptable for

this research and what the principles for sedimentation and maintenance dredging are. The

chapter 3 deals with a feasibility study regarding potential market, technical, legal, operational

and financial viability. Going to the next chapter 4, which includes a tentative to determine the

stakeholders, defining their influences, roles and impact on the project. These three chapters

close the introductory block.



Chapter 5 brings an extensive literature review based on relevant topics to the unmanned

operation, serving as foundation to prepare the concept desired by the author. The next chapter

6, attached to this research as an additional material, regards a briefing of the overview of

unmanned operation and what researchers, universities, companies have developed so far and

for sure, as long as this material get older, some of them will be already a reality in the next 15

to 20 years. These two chapters try to create the foundation to explain how the topics combined

are important to design a concept of operations.

Going to the concept for the unmanned maintenance dredging, chapter 7 brings the

concept of operations itself. This chapter will develop a model for the application, defining the

appropriate device for such application in an unmanned operation point of view. In addition,

the form factor of the vessel, the material to be dredged, the dredging equipment and what

conditions this system will be exposed are part of the scope. A multi criteria analysis is carried

to led the best alternatives for which point described above.

Concluding the thesis, in chapter 8, the main conclusions and recommendations for

further studies are presented.

2. Problem Description

2.1. Maintenance Dredging and Sedimentation

Siltation is a continuous phenomenon that takes place in most of our ports and waterways.

In order to guarantee the desirable water depths on a continuous basis it is necessary to carry

out regular maintenance dredging. Especially for the smaller projects, this means heavy

financial burden on the port management as dredging becomes generally spoken more efficient

with increasing size of the port especially when using the more traditional dredging techniques.

(1). Furthermore, human development disturbs the natural balance by building ports, navigation

channels, harbours, marinas, and sheltered areas to protect the vessels against waves, increase

the safety and efficiency. Therefore, nature will always try to re-establish their natural balance

by filling up those areas created by human occurring sedimentation and thus obstruct traffic.

Maintenance work is inevitable to help the economy within the maritime industry,

especially because ships are getting bigger and bigger in size to transport more cargo in one

time, and thus lower the costs, raise demand and attract more investments. According to (2) in

1980, the largest vessels could ship 4100 TEU’s. By 2012 that number had risen to 15,000

TEU’s and nowadays with the addition of Maersk’s “Triple E”, the largest ships in the world

have a capacity of 18,000 TEU’s



Considering that dredging is a complex activity, every job has different characteristics,

and sometimes is necessary to use a rudimental device to complete the task, even though the

efficiency is at the bottom. This specific feature, forces dredging companies to diversify their

fleet to meet the needs of their customers.

Seeking to indicate the volume of material dredged, the Figure 01 provides an overview

from 1995 to 2010 of the yearly amount of material removed in the Botlek Harbour in the Port

of Rotterdam.

Figure 1 - Volume maintenance dredging a year in the Botlek area. Retrieved September 07, 2017 from Source: (3)

It is important to investigate where the sediment comes from. The port can be situated

alongside a river, with sediment coming from land by this river, as demonstrated in Figure 02.

A port can also be situated directly at sea without an inland river connection (see Figure 03).

Ports are in both cases dead end water arms where water does not run through, but where water

and sediment enters and leaves through the same port entrance. This makes many ports a low

energy environment (L.E.E) with low current, whereas the area directly outside the port is more

likely to be a high-energy environment (H.E.E). (1)



Figure 2 - River and Sea influence in Port Area. Retrieved September 01, 2017 from Source: (1)

Figure 3 - Sea Influence in Port Area. Retrieved September 01, 2017 from Source: (1)

2.2. Requirements for dredging device

As discussed previously, dredging is a complex activity and the main goal of this material

is to propose an unmanned solution to remove material in a port basin. Seeking for the right

selection of the dredging method, a set of criteria is thus, indispensable to find the best solution

for the proposed dredging task.



The application is designed to remove thin layers of material from the bottom of channels

and harbours, being small, autonomous and able to work all-year round.

A diagram pointing out characteristics seeking to define the most appropriate device is,

then proposed below:

Figure 4 - Criteria diagram for dredging device. Source: Author

1. Stability: The dredging process should be stable and be able to work for hours

without human interference.

2. Maintainability: The device needs to have a well-detailed maintenance plan,

uploading reports with the actual status.

3. Reliability: The system has to be reliable to minimize the risk on delays and

failure.

4. Safety: Since other vessels can be around the dredging device, a collision

avoidance system coping with all the regulations is essential to keep the safety

along the working area. The system must be capable of see the difference between

the different vessels around and take a decision to avoid collision.



5. Capability: The device should be able to deal with debris found along the way.

Moreover, the device should be able to work at depths of 10-20 m.

6. Energy supply: The future is demonstrating a promising change from fossil fuels

to renewable energy. This way, the device should be ready to cope with changing

sources, although the main system needs to go for the most cost effective

propulsion system.

7. Size and Workability: It has to be as small as possible and work all-year round to

optimize its efficiency.

8. Operational costs: In order to be feasible, the concept needs to be less expensive

than the ordinary process.

9. Building costs: The building costs will be substantially more expensive, however

they need to be reduced as much as possible.

10. Supervision: The concept is tagged as “unmanned’, although some human

supervision must be allocated for the initial set up.

2.3. Mud characteristics

This chapter brings an overview about the properties of mud and how much influence it

has on dredging works. In special, the book Hydrodynamics and Water Quality: Modelling

Rivers, Lakes, and Estuaries written by (4) and following into account (5), (6), (7), (8) for the

information necessary to compose this subchapter.

2.3.1. Classification and composition of mud

Mud term defines a liquid or semi-liquid mixture of water with weak soil mixtures of

clay, silt, or in some cases sand. The properties will vary depending on the composition of the

material. (4) Classifies sediments as:



• Non-cohesive particles: It indicates no cohesive forces and attraction forces, being

comparatively coarser particles. E.g.: silt and sand;

• Cohesive particles: It refers to sediment in which antiparticle bonding is primarily

a result of physicochemical attractions between particles. E.g.: clay and organic

material;

A conceptual model of sediment transport processes extracted from (4) is illustrated in

Figure 05

The shear strength indicates the resistance against breaking the coherence between its

particles. In order to destroy the coherence, a value of shear strength as large as the cohesion of

the mud is necessary.

The conceptual design must be able to handle mud, which is mainly related to cohesive

particles. PIANC (1) Claims that is economically feasible to turn a soil into a mixture when the

cohesion is below 10kPa. In addition, states that soils presenting higher figures will only

partially go into suspension, remaining soil in lumps at the bottom.

Figure 5 – Sediment transport processes. Retrieved December 10, 2017 from Source: (4)

Mud behaviour is dependent on the components presented in the mixture, it makes

essential to study the mixture in order to obtain good input values for calculations.

In his thesis (5) claims the properties of mud divides in two groups, the first one is

structure-dependent, pushing to be determined in-site. On the other hand, the structure-



independent can be determined from stirred soil samples. The second group is mainly used to

identify and classify mud. Such properties are described in (5) as follow:

• Composition of solid matter: mineralogy and organic content;

• Composition of pore water

• Particle properties: grain distribution, specific surface, density, electric charge;

• Flocculation parameter: parameter for the occurrence of flocculation;

• Attenberg limits;

• Stirred rheological properties;

• Water and gas content.

2.3.2. Mud appearance in water column

Considering the mud as cohesive particles, (4) defines three distinct regions of the

following layers:

1. The uppermost region or suspension layer has a relatively low sedimentation

concentration;

2. The thin fluid mud layer is differentiated from the mixed layer by a steep

concentration gradient termed “lutocline’;

3. The bottom region is a consolidated bed with high concentration of sediments; this

layer has accumulated over time, thus density and strength increased.

Figure 06, brings the representation of the vertical profiles of cohesive sediment

concentration S(z) and the corresponding flow velocity u(z).



Figure 6 - Vertical profiles of cohesive sediment concentration and velocity. Retrieved December 10, 2017 from Source: (4)

2.3.3. Plasticity index and water content

Plasticity for cohesive soils is driven by the Attenberg limits. It relates the state of the

soil with the amount of water content. The water mass divided by the grain mass defines the

amount of water content in the mixture:

𝑊 =𝑊#$%&'

𝑊('$)*+

Fine-grained cohesive soils can have four types of consistencies: solid, semi-solid, plastic

and liquid. The boundaries between each consistency is known as the so-called Attenberg limits

described by (5) and (7):

• Shrinkage limit (SL): is the water content at which there is no more volume

change in the soil due to reduction in water; (9)

• Plastic limit (PL): is the lowest water content at which the soil exhibits plastic

behaviour; (9)

• Liquid limit (LL): is when the soil represents a near liquid state. (9)



Figure 7 - Soil consistencies and Attenberg limits. Retrieved December 10, 2017 from Source: (9)

The plasticity index is used to compare soils to each other. It is simply the difference

between the liquid limit and the plastic limit. As a matter of quantification, the finer the soil the

greater is the plasticity index.

Plasticity index (PI) = Liquid Limit (LL) – Plastic Limit (PL)

The plasticity chart as in Figure 08 was proposed by (10) in order to classify cohesive

soils based on their plasticity among their mineralogical composition, particle surface and

organic content.

Figure 8 - Casagrande's plasticity chart. Retrieved December 10, 2017 from Source: (11)



2.3.4. Rheology

By definition, the term rheology describes the material’s deformation related to the forces

exerted on these materials. Therefore, from the relation between Shear stress and Shear rate is

possible to characterize a fluid. When the relationship has a linear behaviour, the fluid is

considered as a Newtonian fluid. However, there are others models non-Newtonian. Those

models do not follow Newtonian fluid such as Bingham, dilatant and pseudo plastic models.

Figure 9 - Rheological models. Retrieved December 10, 2017 from Source: (12)

Mud does not follow the Newtonian fluid linear path, and its rheological properties are

changing often during in-situ and sampling experiments. For this reason, Bingham model

mainly used to model mud. (13) Defines the following formula for this model:

𝜏 = 𝜏- + 𝐾𝛾*

Where,

𝜏 = shear stress;

𝜏- = yield stress;

𝐾 = fluid viscosity;

𝛾 = shear rate.



2.3.5. Consolidation

According to (14), the definition for consolidation is a process of floc compaction under

the influence of gravity forces with a simultaneous expulsion of pore water and a gain in

strength of the bed material. Three stages are established:

• Initial stage (days): This stage consists of hindered settling and consolidation. Flocs

are fresh and grouped in an open structure with large pore volume. The bed surface

sinks with time t;

• Secondary stage (weeks): At the second stage consequently the pore volume between

the flocs are further reduced. The pore water will escape through thin vertical pipes.

The bed surface sinks with 𝑡3.5 or log(𝑡);

• Final stage (years): In the last stage, the pore volume is reduced at one point that flocs

will break down. The bed surface sinks withlog(𝑡).

Extracted from (14). For the consolidation of the mud layer, it will depend on:

• Initial thickness of the mud layer;

• Initial concentration of the mud layer;

• Permeability of the mud layer, depending on sediment composition and size,

content of organic material, salinity and temperature.

3. Feasibility Study 3.1. Market research study

The first step towards the feasibility study is to map the main dredging companies around

the globe in order to understand whom the key players, the market share, size of their fleet,

services offered and main customers. Some market research studies on dredging market are

periodically ordered by organizations interested in having a forecast of future market and thus,

define how much money should be invested on each sector. Moreover, due to the contents in



those reports, their availability are restricted to corporations and the material attached in this

report is effort of research on articles, websites, and periodic reports from organizations and

associations specialized in dredging market.

Another important aspect to state is the way that dredging market is divided into two

markets. As the author (15) says, the dredging market is split into an open and closed market.

The largest closed markets are China and the USA. Regarding USA, the Jones Act protects the

US dredging companies, obliging to use equipment built in the USA, use American employees,

and owned by US citizens. Yet, open markets accounts for 57% of the total global market

according to report issued in 2012 by International Association of Dredging Companies –

IADC.

International dredging market movements roughly EUR 11bn yearly. However, as

mentioned previously, China and United States are closed market and thus, there is a

monopolization of local companies in those areas. For this reason, this piece of work

contemplates only open markets, where there is international competition seeking to increase

their role in the market share. Figure 10 represents the turnover of open markets by region in

2015.

Figure 10 – Geographical breakdown open dredging market in 2015. Retrieved September 17, 2017 from Source: (16)

The dredging market is huge, and their applications may be divided into end-markets as

presented in figure 11 below:



Figure 11 - Dredging divided by end-market in 2011 (EUR). Retrieved September 17, 2017 from Source: (15)

Listing dredging operators is not a spontaneous task; however, the work will attempt to

focus on the major ones, determining 10 companies, which have been instrumental in

propagating the furtherance of this marine activity.

The rank is based upon the following aspects:

• Annual Revenue

• Total Capacity in m3 (Trailing Suction Hopper Dredgers)

• Total Capacity in kW (Cutter Suction Dredgers)

• Total Capacity in m3 (Backhoe and Grab dredgers)

• Number of employees

1. Jan de Nul: Started in the late 1930s, Jan de Nul is a familial Belgian dredging

corporation. Though the company’s original operational stream was civic

constructional activities, its latter conversation as a dredging contractor has resulted

in getting the conglomerate, a worldwide professional recognition. (17)

2. Royal Boskalis Westminster: The Dutch conglomerate started in the year 1910, in

the over-100 years of the company’s start, the corporation has established its presence

in 50 nations across the world. Its steady focus on dreading, right from the start of its

establishment, has helped Royal Boskalis Westminster to amass a dredging fleet that

is unparalleled in the world. (17)



3. Van Oord: Jointly owned by an investment conglomerate – NPM Capital, the Van

Oord business family line and the construction giant Royal BAM, the Van Oord is a

Dutch dredging company. It is also perhaps one of the oldest in this compilation,

having been established in the year 1868. At present, the company has a huge

international presence with exponential success stories substantiating the same. (17)

4. DEME: Abbreviated for Dredging, Environmental and Marine Engineering, DEME

is a Belgian dredging consortium and predates back to the 1800s. The company’s

inaugural year of operations though is specified as 1991. (17)

5. CHEC (China Harbour Engineering Company): Giving credible claim to the

Chinese domination in the dredging sector is CHEC. The company, started in the year

1980, has risen amongst the ranks of world dredging players to become the leading

dredging contractor in China. The company is an ancillary of the CCC – China

Communications Construction Company ltd. (17)

6. Great Lakes Dredge and Dock: An American dredging operator, the Great Lakes

Dredge and Dock started its operation in the year 1890. Located in Illinois, the

company is at present United States’ largest dredging contractor, though it does have

a presence in the international dredging domain. (17)

7. Weeks Marine Inc.: Featuring amongst the top 100 dredge operators in the world.

The American dredging conglomerate was started in the year 1919 and has presence

not just in the United States, but also in Canada. With a wide repertoire of dredging

success, the company is one of the biggest dredging companies in the whole of the

United States. (17)

8. National Marine Dredging Company: A Middle eastern enterprise, the National

Marine Dredging Company was established in the year 1976 and is headquartered at

the city of Abu Dhabi. The conglomerate is an ancillary of the leading petroleum

corporation of Abu Dhabi. It has been carrying out several noteworthy operations in

the Middle Eastern region. (17)



9. Inai Kiara: A Malaysian giant, the Inai Kiara was started in the year 1997. In the

over 10 years, since the company was established, it has taken great strides in putting

Asian dredging operators on the world map. (17)

10. Hyundai Engineering and Construction: The Company was formed because of a

merger between Hyundai Engineering and Hyundai Construction in the year 1999.

The South Korean giant has been responsible for various singular and construction

works, not just in South Korea but also across the world. (17)

Among the ten biggest dredging companies listed, Netherlands and Belgium companies

control the first four positions, establishing themselves as the key players in the dredging

market. Moreover, it is possible notice by figures that European dredging companies have at

least 66% of market share in worldwide open markets.

Table 1 - List of dredging companies by country. Source: Author

Country Dredgingcompanies

US 2

Belgium 2

Netherlands 2

SouthKorea 1

China 1

UAE 1

Malaysia 1

Figure 12 - Top 10 Dredging contractors by country - Graphic Representation. Source: Author

20%

20%

20%

10%

10%

10%

10%

Top10DredgingcontractorsbyCountry

US

Belgium

Netherlands

SouthKorea

China

UAE

Malasyia



3.2. Technical & Operational Feasibility

From the technical and operational point of view, the present equipment catalogue

available in the market is already robust; however, improvements regarding autonomous

navigation are necessary to have smart vessels able to avoid obstacles and perform a vast range

of tasks on water. It already is possible to notice autonomous cars and aerial vehicles being

advertised as the future of the transportation. In addition, maritime industry is still in slow pace

and only few local applications are in operation nowadays.

Humans are building vessels at least since 3000 BC, being the first models made of

wooden planks transformed into a hull, since then, many studies developed new designs,

materials, and ways to transport goods, people and perform essential tasks to analyse and

maintain the water state. Crewless devices are already a trend among others means of

transportation and specialists claim that in a period of 10 to 20 years it will happen in the

maritime industry as well. Few companies are already putting money and a lot of effort to be

the first to develop a system capable of taking actions better than human.

Those smart crewless vessels in question do not have the same constraints encountered

as seen in the manned vessels, making design office, shipbuilders to have more freedom when

developing new state-of-art concepts. After research and gathering information from different

sources is possible to notice aspects from the technical point of view where unmanned

navigation is ready to go and points that still need to be discussed and developed in order to

create a reliable control system to work in different situations.

Nowadays, as mentioned above, some companies are developing such intelligent systems

for Autonomous Surface Vessels. The company ASV Global -Unmanned Marine System seems

to have one of the most promising Autonomous System in the market. Their control system is

the ASView, a system able to work autonomously or remote-controlled. Moreover, the system

has five different operating modes: Remote mode, Automatic mode, Mission mode,

Autonomous mode and External mode. (18) It is possible to notice that each operating mode

has a different level of autonomy, and it starts from being fully controlled by human to the

autonomous mode, consisting of artificial intelligence, thus making decision to avoid collision

and achieve mission goals. For this level of autonomy, the operator overrides only if required.

Another essential point is safety; the unmanned vessel must be at least as safe as the

manned, emergency stop button, return to base behaviour on loss of communications, cyber-

security against web pirates are trivial for such type of navigation. One setback regarding

communications is the fact that if the embarkation is going beyond 30 nautical miles data



transfer through narrow and wide radio band links is not possible. Therefore, the

communication to satellite links is the option available, which can represent raise in the costs

of operation, with the use proximity sensors such as high definition cameras, Infrared cameras,

LIDAR, RADAR and AIS; the transfer of this data in real time is a real concern. On the other

hand, some methods to reduce the transfer date during autonomous and stand-by are applicable.

As a conclusion from technical point, unmanned vehicles may still face challenges

regarding a reliable avoidance collision system, development of system standards, reliable

cyber security system, how would be the operating control centre, operating modes,

communications shortcomings for long distance journeys and a universal framework in order

to have further develop to other applications rather than military and hydrographic survey.

3.3. Legal Feasibility

The approach regarding unmanned vehicles must be against what is available right now.

For now, all the rules and standards take into account people on board, and for instance,

unmanned vehicles need to have freedom to develop their own concepts instead of following

has is present in the market. This chapter will be responsible to list some major issues and if

they are feasible or not.

The first major issue is the fact considering the present rules is mandatory to have crew

on-board in order to sail into open sea. The term unmanned means people are controlling the

vessel someway far away from the vessel. Therefore, while this requirement does not change,

an unmanned vessel is a drone and can sail only in territorial waters or under military services,

where special license waive them to operate for mission tasks.

As of July 2016, the classification society Lloyd’s register has issued a guidance, where

six ‘autonomy levels’ are classified and had been seen among marine community as one further

step to classification of autonomous ships. The guidance by Lloyd’s register states autonomous

levels (AL) from ‘AL1’ through ‘AL6’ denoting a fully autonomous ship with no access

required during a mission. According to Lloyd’s (19) the ‘AL’ system of levels provides clarify

to designers, shipbuilders, equipment manufacturers, ship owners and operators, enabling

accurate specification of the desired level of autonomy in design and operations.

On the same hand, something that can become a huge setback is the fact employers will

want to reduce their costs with manning, consequently unions and workers will want a further

discussion to understand what types of applications are eligible for unmanned vehicles. From



this point of view, local applications are low profile, where investments and risks are low, and

not drawing much attention. For this reason, local applications like autonomous tugs, work

boats, dredging devices are a perfect scenario to start the unmanned navigation wave that can

change the way how services and goods are transported and executed.

3.4. Financial Feasibility

Considering building costs, manufacturing a regular vessel to unmanned navigation

would have similar investment for the hull, superstructure and main propulsion system. On the

other hand, equipment for communication, control system, auxiliary systems, automated

mooring, and avoidance collision system or situation awareness would require more

investments, especially because of the need of experts to develop robust and reliable suite of

software integrated to hardware in order make the unmanned vehicle take decisions and excel

in a range of complex situations. It is hard to estimate values, but it is clear that not all

applications are eligible for unmanned navigation. Applications such as coastal tankers and dry

bulkers, for example have very low freight rates and innovative technologies are not on the

budget. Unlike, containers feeders for short sea shipping demonstrated high potential if possible

to have a feeder system not requiring workers to do the job of loading and unloading.

The main outcome regarding the potential for a hypothetical unmanned dredging market

states that the money invested to develop unmanned dredger would not be a problem. It is

logical that customers would be glad to reduce their operational expenses with maintenance

dredging. However, the dredging market having very few key players around the world, and

after trying contact to most of them, it is possible realize that they are not keen in reduce the

price of their contracts of let port operators take over a technology redundant and simple to use

on daily basis.

As conclusion, unmanned vehicles can change the game how people are doing the

navigation for centuries, but is clear that some stakeholders would have to cede benefits in order

to make this happen.

4. Stakeholders 4.1. Defining the stakeholders

A stakeholder is a party that has an interest in a company, and can affect or be affected

by the business. The primary stakeholders in a typical corporation are its investors, employees



and customers. However, the modern theory of the idea goes beyond this original notion to

include additional stakeholders such as a community, government or trade association. (20)

Being objective, it is possible to divide the stakeholders into two main areas: internal and

external stakeholders. Therefore, internal stakeholders are entities within a business (e.g.,

employees, managers, the board of directors, investors). Employees want to earn money and

stay employed. Owners are interesting in maximizing the profit the business makes. Investors

are concerned about earning income from their investment. (20)

Meanwhile, external stakeholders are entities not within a business itself but who care

about or are affected by its performance (e.g., consumers, regulators, investors, suppliers). The

government wants the business to pay taxes, employ more people, follow laws, and truthfully

report its financial conditions. Costumers want the business to provide high-quality goods or

services at low cost. Suppliers want the business to continue to purchase from them. Creditors

want to be repaid on time and in full. The community wants the business to contribute positively

to its local environment and population. (20)

The first brilliant idea that can come to your mind may be something innovative and

unique; however even though you are a billionaire and can make people work for you, the

project will need collaboration from many different areas. As an example if the major

stakeholder is the government, it will follow standards procedures, which can take more time

than expected and interfere with the quality of the outcomes. The example above is a sample

that projects are an interactive process and all parts need to have their roles, how they can

contribute and affect to boost or kill the project.

It is evident that some projects are well known among the stakeholders and for those

cases, less sensibility is noticed to develop the project in question, years of experience doing

similar projects may explain those situations.

For this report, the idea behind the project is something new, and it may impose a

challenge to persuade the stakeholders to impact in a way to support it. This way, it is essential

to map the major stakeholders, defining external and internal ones, their roles and ways to make

them collaborate to take it out the paper and go to operational and production lines. For this

reason, the following sub-chapter 4.2 details they ones involved through a stakeholder’s

analysis.



4.2. Stakeholders analysis

The process of mapping stakeholders is not as intuitive as it may look. There are dozens

of people involved in any project and sometimes at the first sight, their importance are ignored,

however they can influence the project to the failure if not treated in a correct way. In this work,

the author’s role relates to a researcher proposing a new concept for a traditional maintenance

dredger operation, seeking to find a way to please the stakeholders to converge to the same a

shared objective.

A stakeholder’s analysis presents, identifying and proposing strategies for engaging all

parts to one single objective. For this analysis, questions are proposed and their answers are

essential to adapt the initial idea into something palpable.

The first two questions have objective answers varying their impact and influence from

Very Low to Very High. The following four questions of the questionnaire have subjective

response depending on the holder. The last one outline the most appropriate strategy for

engaging the specific stakeholder to cooperate with our proposed scheme.

Below is possible to check all 6 questions answered to compose the stakeholder’s

analysis:

1. Impact: How much does the project affect them?

2. Influence: How much influence do they have over the project?

3. What is important to the stakeholders?

4. How could the stakeholder contribute to the project?

5. How could the stakeholder block the project?

6. Strategy for engaging the stakeholders.

• Dredging companies

1. Impact: Very High

2. Influence: Very High

3. Provide their services and fleet to do the appointed job, keep or/and increase the

number of contracts.

4. Propose new systems, materials, shapes and ways to help customer save money

and time

5. Deciding that this is not for now, postponing the development of unmanned

systems;



6. Look for motivations in the market that port terminals are looking for ways to

reduce costs, and open to choose unmanned vehicles rather than a manned one.

• Ship designers

1. Impact: High

2. Influence: High

3. Design the vessel according to customer demands

4. Propose new systems, materials, shapes and ways to help customer save money

and time

5. Deciding that it is too expensive developing unmanned systems and not

engaging specific team to do it.

6. Finding motivations that the customer would choose an unmanned vessel rather

than a manned one and gathering teams to design those new designs.

• Shipbuilders


2. Influence: Low

3. Be able to build units using their manufacturing processes

4. New facilities able to build state-of-art units

5. Not investing in high skilled workforce and machineries

6. Sign a memorandum of understanding, presenting ways to improve the

production processes if unmanned vehicle chosen.

• Fleet owners

1. Impact: High

2. Influence: High

3. Own the fleet and able to charter or use them

4. Contracting the design office to develop new ideas regarding unmanned

operations.

5. Not considering unmanned operation feasible, taking it out of the agenda.

6. Offering ways to decrease the operational costs and increase the Return on the

Investment in a medium term.

• Operators


2. Influence: High

3. Save as much as possible the costs and use the fleet to comply with the contract

requirements



4. Operators as the name suggests, they have control over the ships to navigate

and do specific activities, therefore they can put pressure on regulatory,

environmental organizations to discuss new innovative ideas to help control the

outgoings and strengthen the market

5. Neglecting autonomous operation and keeping the market as the usual, thinking

only in the present, not in the future.

6. Congress, Symposiums, Meetings are important to expose how technology can

provide support to change the marine/maritime industry.

• Classification societies


2. Influence: High

3. Being able to class the dredgers and provide further technical assistance in

accordance with the regulations.

4. Engage teams to study, develop, and adapt the rules in vigour to autonomous

systems.

5. Not engaging workforce to study the topic or providing any technical assistance

to stakeholders willing to class their ships.

6. Regular meetings, presenting simulations and convincing studies regarding the

theme.

• Equipment manufacturers



3. Provide parts, equipment, engines, technical assistance, etc.

4. Developing new systems that can work without human interference, such as a

robust Shore Control Centre, Sensors, Cameras, Software, etc.

5. Not engaging the Research & Development department to spend hours on

developing new products.

6. Defining the plans and what are the demands regarding the topic.

• Environmental regulators

1. Impact: High


3. Keep the emissions as low as possible to preserve the environment

4. Issuing informative reports, and setting strict rules to use cleaner fuel sources

5. Postponing the deadlines and easing the rules



6. Keeping in touch, attending meetings, studying the regulations and proposing

ways to reduce the impacts in the environment.

• Universities

1. Impact: Medium

2. Influence: High

3. Research and provide workforce and solutions to the industry be more efficient.

4. Focusing their researches on this specific topic, being able to provide enough

data to encourage companies to buy the idea.

5. Not giving a special attention to the project and not providing reliable data as an

outcome.

6. Funding projects, looking for researches and universities who want to develop

such kind of project.

• NGOs

1. Impact: High

2. Influence: High

3. Keeping the environment preserved, researching activities and information on

oceanography and marine environment and provides advices and guidance to

other organizations.

4. Studying about the topic, gathering reliable data, organizing seminars to spread

the idea among the stakeholders.

5. Ignoring the project, no public initiatives, not allocating a specialized staff to

work on it

6. NGOs have substantial capability to contribute to the work of IMO, for this

reason, becoming a member of NGOs and contributing to the work is a way to

disclose the project among the members and others organizations driven to make

the project a reality.

• Government

1. Impact: High

2. Influence: High

3. Receive taxes provided by the industry, increase the flow of money around the

port and increase the job offers. Moreover, in some markets, government is the

major costumer.



4. Defining ambitious goals to reduce airborne pollutants in the next years and

providing tax waiver to organizations who want to develop new autonomous

systems.

5. Blocking new contracts and favouring local companies to win the contract over.

6. Maintaining a good relationship with the government, paying all the taxes,

keeping the jobs and present the advantages of the new project.

• Costumers



3. To have the task done, spending less time and money possible with safety.

Another aspect is to preserve the environment and human lives, following

regulations and standards imposed by specialized branches.

4. Being open to discuss new solutions to do the work using unmanned system.

5. Denying new solutions and going for the traditional way.

6. Approaching the customers and offering them ways to reduce their operational

costs, aiming to distinguish from other competitors and provide new innovative

solutions where both parts can earn.

• Insurers

1. Impact: High


3. Be able to detail a profile, charge for it and issue an insurance policy to the asset

in the event of loss or damage.

4. Assessing researchers, reports, standards and rules regarding the safety of

unmanned systems.

5. Not insuring the unmanned fleet or even demonstrating interest in issuing

insurance policies for this type of operation in a near future.

6. Creating a framework for autonomous operation to insurers assess the liability.

If proven that this new system is safer, companies will see as a niche to gain

more, reducing the accidents and damage.

• Media

1. Impact: Low

2. Influence: Medium

3. Publish the news to the community, attracting as much as possible audience.



4. Posting articles in different means of communication where the advantages are

clear to the customer, drawing attention and making them to look for more info

about the project.

5. Press can post biased articles to influence the audience that this topic is

dangerous and impossible to happen.

6. Create and maintain a solid network with important journals, magazines,

websites, and communities. Also is extremely important to provide

presentations, give interviews, and answer the questions and doubts about the

project.

• Maritime Community

1. Impact: Medium


3. Community is seeking for new solutions and ways to engage the stakeholders to

a new era, where man can stay on shore and just control over the air the

machinery.

4. Technical research, specialized papers, conferences to develop and create

awareness about a universal regulatory framework. In addition, the benefits for

fleet owners and what are the breaches that need to be minimize the legal

implications.

5. Not engaging into further discussion, in a way that fleet owners, design office

and operators do not feel that is wise put money into this new way to

navigation.

6. Development of case studies, papers, annual conferences, technical meetings,

articles in specialized magazines and attendance of key companies during all

events proposed by the maritime community

• Employees



3. Keeping their job posts, transparency policies, good work conditions, wages

paid correctly, and opportunities to get a promotion in the company.

4. Understanding the demand for such type of vessel and the importance for the

industry keep the growth.

5. Going on strike, drawing attention of public opinion, pressuring government and

unions.



6. Gathering all parties involved to discuss the certain benefits and the possible

drawbacks and ways to maximize and reduce them, respectively. This way is

possible to have an agreement in order to have a gain-gain situation.

• Unions



3. Keep the jobs and avoid people being fired because of autonomous operations

4. Not blocking the discussions about the topic

5. Going on strike, Drawing public attention

6. Meetings and discussions to find a good solution to insert innovation and keep

the posts

• Port terminals



3. Reduce operational costs and increase the revenue, being able to receive as much

as possible vessels, reducing the idle time to load and unload.

4. Providing their needs in order to the team designing be able to attend all the

requirements and save money doing in-house rather than going for a

subcontractor.

5. Not assuming such duty as part of their services, keeping the contracts for

maintenance dredging.

6. Keeping in touch with small sized ports, marinas and sites where maintenance

dredging compromises a reasonable part of the expenses. Customers should have

the chance to test the service and check if the quality is as expected.

• Oil Producers

1. Impact: Medium

2. Influence: High

3. Maintaining the fleet using fossil source as much as possible;

4. Not pushing the price of oil to the bottom;

5. Creating a boycott against new ways to generate energy, controlling the prices

to keep it still attractive;

6. Have talks about the importance of fuel efficiency.



• Competitors


2. Influence: High

3. Own the knowledge of state-of-art control system, software, process or

equipment in order to make profit and increase the annual revenue;

4. Sharing their ideas to have a pool of new ideas and proposals in the further

market;

5. Doing research about the field, patenting new systems but keeping all the

blueprints away from the community;

6. Competitors must understand that marine industry needs a boost and

cooperation is essential to keep growing along the years.

• Investors



3. They want to multiply their income by making good investments or/and reduce

the losses in the whole process.

4. Funding the project with amount of money necessary to design, build and

operate it.

5. Being conservative and not funding the project.

6. Meetings to define what and how is possible to achieve, providing really

arguments to the investor put their money on it.

5. Literature Review 5.1. Human-Robot Interaction and Level of Autonomy

Often referred as HRI by researchers. Human-robot interaction is a multidisciplinary field

with contributions from human-computer interaction, artificial intelligence, robotics, natural

language understanding, design and social sciences. (21)

Perhaps the most strongly human-centred application of the concept of autonomy is in

the notion of level of autonomy, or LOA as known among researchers. Levels of autonomy

describe to what degree the robot can act on its own accord. Although many descriptions of

LOA have been seen in the literature, the best and most widely cited description is by Tom

Sheridan. (22). In Sheridan’s scale, the author defines ten different levels of autonomy, starting



from the point that the device is totally controlled by a person, until the last level of autonomy,

which comprises being completely independent and not needing any input or approval of its

actions from a human before taking actions. See figure below to see the levels of autonomy

proposed by Sheridan.

Figure 13 - Levels of Autonomy with emphasis on human interaction. Retrieved September 04, 2017 from Source: (23)

Figure 14 - Levels of Autonomy proposed by Sheridan. Retrieved September 04, 2017 from Source: (24)

Variations of this scale have been developed and used by various authors (25) and (26).

Authors have noted that such scale may not be applicable to an entire problem domain but are

rather most useful when applied to each subtask within a problem domain (27). For this reason,

one simple way to consider autonomy to reality is by defining what is the level of interaction

human and robot can perform and the degree level each is capable of autonomy.

The scale presented in Figure 13 gives an emphasis to mixed-initiative interaction, which

has been defined as a “flexible interaction strategy in which each agent (human and robot)

contributes what it is best suited at the most appropriate time” (28). It is possible to detect that

on the direct control side, the issued are developing a user interface that can provide support

the operator and reduces the cognitive load. On the other side, the issues regard how to design

robots with enough cognitive skills to flawlessly interact with a human.



Autonomy is implemented using techniques from control theory, artificial intelligence,

signal processing, cognitive science and linguistics. A common approach is sometimes referred

to as sense-plan-act-model of decision-making (29). This model is typified by artificial

intelligence techniques, such as logics and planning algorithms (30).The model can also

incorporate control theoretic concepts, which have been used very successfully in aviation,

aeronautics, and missile control (31)

In the mid-1980s, Brooks, Arkin, and others revolutionized the field of robotics by

introducing a new autonomy paradigm that came to be known as behaviour-based robotics. In

this paradigm, behaviour is generated from a set of carefully designed autonomy modules that

are then integrated to create an emergent system (32), (33) and (34). One important aspect to

state is that this model was accompanied by hardware development, allowing autonomous

modules to be implemented in small applications regarding robotics.

Nowadays, many researchers create hybrid architecture based on sense-think-act and

behaviour-based models. In these systems, the low-level reactivity is separated from higher

level reasoning about plans and goals (35). Some have developed mathematics and frameworks

that can be viewed as formalizations of hybrid architectures and which are referred to as theories

of intelligent control (36) and (37).

Relating to marine field, autonomous vehicles are already state-of-the-art in many land

based transport models. There are many examples of automated subways, self-driving intra

logistics vehicles or automated guided vehicles (AGV) on modern container terminals. There

are also very wide-ranging approaches of autonomous control concepts in modern aviation.

Unfortunately, the use of autonomous systems is not related only to technology and many

parameters must be discussed before those systems going out to the market.

5.2. Dredging 5.2.1. Definition

A general definition for dredging is as a process of removing sediments or part of the

seabed with a goal of creating or extend harbours, basins, canals, marinas for the purpose of

navigation or related with construction projects.

The device used for excavation and scraping of the seabed is called the Dredge and the

ship or vessel a dredge is fitted to be known as a Dredger. (38)



Figure 15 -- Dredger discharging material in the sea. Retrieved September 06, 2017 from Source: (2)

5.2.2. Historical

Dredging is an ancient art but a relatively young science. Traces of man’s work involving

primitive dredging techniques have been discovered in many places, dating back to thousands

of years BC (39). In such instances, the vessel was probably little more than a raft and the

excavating means a man with a bucket. The development of this method of excavation into the

spoon and bag dredger and the subsequent proliferation of dredging machines had been well

described (40).

With the development of powerful dredging machinery, there was a corresponding

increase in the scope and complexity of engineering projects, which could be executed by

dredging. For a considerable time the art of using this equipment was known only to small

groups of men who passed their knowledge and experience on from one generation to the next.

With the advent of the Industrial Revolution, which transformed many arts into sciences, the

dredging process was subjected to greater scientific analysis (41)

The development of dredging methods has been influenced by geographical

characteristics. Whereas the major developments in mechanical excavating methods in the 19th

century probably occurred in the lowlands of Europe, the development of hydraulic dredging

techniques, and the Americans pioneered using the centrifugal pump. The latter had numerous

sites suitable for reclamation by pipeline dredgers, whilst the European sites were more often

confined, necessitating transport by barge to open sea. In due course, the slow mechanical



methods were largely replaced by suction dredgers and hydraulic dredging became

commonplace worldwide. (41)

5.2.3. Types of Dredging works

Dredging works are classed in one of two categories: capital or maintenance. The

formation of a new bed configuration by dredging, whether the configuration is stable or not,

is known as capital dredging, the implication being that the work involves the payment of a

single capital sum. Any other dredging work would be recurrent and, since it is performed to

maintain the desired bed configuration, it is known as maintenance dredging. (41)

5.2.4. Dredging methods

Dredging used in the marine industry for a variety of navigational purposes ranging from

routine maintenance of small marinas and harbours to the creation and deepening of navigation

channels and berths at major ports. The choice of dredging plant is largely dependent on

environmental conditions such as the hardness and quantify of material to be dredged, site

exposure, the method of disposal, etc. (42)

Different types of dredging equipment and techniques are employed to achieve the

required project outcomes in the most efficient way. There are three main dredging methods,

which are based on the physical processes involved in the excavation and transport of the

dredged material. (42)

These processes are described below:

• Mechanical dredgers:

o Use of mechanical excavation equipment to loosen the seabed sediment and

raise it to the surface. There are three main subgroups of mechanical dredger,

grab dredger, backhoe dredger and bucket ladder dredger. (42)

• Grab dredger: A revolving crane, fitted with a grab, placed on a hopper vessel or

pontoon is known as a grab dredger. As the name suggests, it picks up the sediments at

the seabed with a clam grabbing motion and discharges the contents. Often used for

excavating bay mud it also is useful to pick up clays and loose sand. (38)



Figure 16 - Schematic of Grab Hopper Dredger. Retrieved August 31, 2017 from Source: (43)

• Backhoe dredger: Like some onshore excavators, Backhoe dredgers have a digging

bucket attached to it, which digs through a wide range of materials, and when it is

excavated, it is brought out and placed on the on-board barges. Although they have few

limitations, where deep dredging is concerned but with some recent modern dredgers,

deeper excavation is made quite easy. (38)

Figure 17 - Schematic of Backhoe Dredger. Retrieved August 31, 2017 from Source: (44)

• Bucket ladder dredger: The bucket ladder dredgers use a series of buckets that are

mounted to a wheel, which then using mechanical means pick up the sediments. They

can be used for wide variety of materials including soft rock material and are powerful



enough to rip out the corals as well. However, because of their low production, high

level of noise and the need for anchor lines, their use has hugely diminished in the recent

times. (38)

Figure 18 - Schematic of Bucket Ladder Dredger. Retrieved August 31, 2017, from Source: (45)

• Hydraulic dredgers:

o Use a centrifugal pump and pipe system to raise loosened material in suspension

to the surface. There are three main types of hydraulic dredger, suction dredgers,

cutter suction dredgers and Trailer suction hopper dredgers. (42)

• Plain suction dredger: Known as plain suction dredger, this type of dredger has no tool

at the end of the suction pipe to disturb the material. The principles are the same

applicable to the trailing suction dredger, however the plain suction does not hold the

dredged on-board, and all material is discharged instantaneously through a pipeline.



Figure 19 - Schematic of Plain Suction Dredger. Retrieved September 01, 2017 from Source: (46)

• Cutter suction dredger: They have a cutter head at the suction inlet, which helps to

loosen the earth and take it to the suction mouth. Used for hard surfaces like rock, this

type of dredger sucks up the dredged soil with the help of wear-resistant pump and then

discharge it through a pipeline or a barge. (38)

Figure 20 - Schematic of Cutter Suction Dredger. Retrieved September 01, 2017 from Source: (47)

• Trailer suction hopper dredger: It is suitable mostly for harbour maintenance and pipe

trenching; a hopper dredger is a self-propelled vessel that holds its load in a large on-

board hold known as the hopper. They can carry the load over large distances and can

empty it by opening the bottom doors or by pumping the load offshore. Hopper dredgers



mostly dredge the soft non-rock soils and because of their high production, rates can

carry out land reclamation projects easily. (38)

Figure 21 – Schematic of Trailer Suction Hopper Dredger. Retrieved September 01, 2017 from Source: (48)

• Hydrodynamic dredgers:

o Use the re-suspension of sediments and their transport away from the dredge

area by means of natural forces. The term “Hydraulic dredging” if often used to

group the following dredging techniques, water injection dredgers, forms of

agitation dredgers, that use mixing to make a density current and underwater

plough dredgers, which stir or rake sediments into suspension. (42)

• Water Injection Dredger: Often choice for environmentally sensitive projects, water

injection dredgers work by fluidizing the material by pumping water into the bed

material. Once it is fluidized, it either is moved by a second burst of water or is carried

away by natural current. (38)



Figure 22 - Schematic of Water Injection Dredger. Retrieved September 01, 2017 from Source: (49)

Figure 23 - Example of Water Injection Dredger. Retrieved September 01, 2017 from Source: (50)

5.2.5. Types of Contract

This subchapter is dedicated to expose the types of contract clients and contractors often

use to close a deal. The following contracts are widespread among dredging companies and the

elements are similar to both capital and maintenance dredging.

The list contemplates four general types of contract, which are common in dredging

projects arrangements, these are:

• Lump sum contract

• Re-measurable contract

• Charter contract

• Target cost contract on an alliance or partnership basis



Figure 24 – Risk distribution between contractor and employer for each type of contract. Retrieved November 22, 2017 from

Source: (1)

The figure 24 captured from (1), illustrates the risks related to contractor and employer to

such dredging contracts. Further explanation for each commitment is presented in the following

topics.

For this subchapter, the report issued by PIANC works as a database to explain the

contracts regarding maintenance dredging. All the information extracted from the referring

report is duly mentioned as part of the bibliography and parts not written by author carry formal

citation.

5.2.5.1. Lump sum contract

A lump sum contract is aimed at achieving the contractually stipulated minimum depths

for a fixed price or “lump sum”. The contractor will be paid on an interim basis on the partial

achievement of the maintenance goal. Therefore, correct determination and evaluation of the

seabed height is vital. This form of contract is well suited for areas of operation, which have an

established history of maintenance dredging. (1)

5.2.5.2. Re-measurable contract

A re-measurable contract involves dredging to lines and levels specified by the client

based on indicative quantities for which the contractor is reimbursed at unit prices. The

invoicing is based on specified unit prices/m3, which may vary depending on the soil class.

Therefore, correct recording of the dredged quantities is necessary. The re-measurable contract



is a universal form of contract for dredging since the contractor is effectively paid only for the

work done. (1)

5.2.5.3. Charter contract

A charter contract involves hiring of the dredging equipment in order to carry out

dredging at the dredging site. Invoicing is based on unit prices/hour, while at the same time a

distinction can be made between dredger operation times, sailing times and non-working time.

The required equipment capacity should be specified. The charter contract is primarily meant

for construction works that primarily generate hourly costs. PIANC (1)

5.2.5.4. Target cost contract or an alliance or partnerships basis

In a target, cost contract the target costs are priced by potential contractors at tender stage

and based upon the bids a successful contractor is then chosen and is paid their actual costs plus

a fee throughout the contract period. The contractor is not paid the amounts in the Bill of

Quantities or activity schedule as these serve only as the target total cost. The difference

between the cost and target is shared according to a predetermined formula when the final

payment is assessed. PIANC (1)

5.3. Ship Stability

Ship stability principles are very important to understand why a ship tends to float and

why a solid cube measuring same dimensions and made of same material will sink instead of

floating on the water. The answer relates to Archimedes principle, which states, “A body wholly

or partially immersed in a liquid is subject to an up thrust equal to the weight of the liquid

displaced by the body.” Archimedes mentions two important keywords respectively, up thrust

and liquid displaced, and they are essential to understand his principle.

In the past, ship stability calculations were complex due the lack of further studies

regarding fluid dynamics, pushing shipbuilders to replicate one heavily tested common stability

design, often copying from one generation to the next, making only minor adaptations. Even

nowadays, some design offices rely on rule of the thumb to perform the stability calculations;

however CFD (Computational Fluid Dynamics), ship basin tests are alternatives to achieve

improved results.

The knowledge regarding ship stability is often divided into two major parts. Intact

stability is the first major area, dealing with the stability of a surface ship of intact hulls, hence

no compartment or watertight tank damaged or freely flooded by seawater. The second part,



damaged stability studies the identification of compartments that may compromise the

buoyancy of the ship, monitoring and predicting the trim and draft conditions.

Damaged stability, however, cannot be understood without a clear understanding of intact

stability, and the interesting scenarios related to it (51). For this reason, this topic will first focus

on intact stability, describes the concepts and then move on to damaged stability.

The concept of metacentre allows understanding how to proceed with the intact stability

calculations, which in a simple manner has the goal to identify all the centres of mass of objects

on the vessel and then obtain the centre of gravity of the vessel, and the centre of buoyancy of

the hull. According to (52) in the vast majority of vessels, the centre of gravity is well above

the centre of buoyancy. The ship is stable because as it begins to heel, one side of the hull begins

to rise from the water and the other side begins to submerge. This causes the centre buoyancy

to shift toward the side that is lower in the water. The job of the naval architect is to make sure

that the centre of buoyancy shifts outboard of the centre of gravity as the ship heels. A line

drawn from the centre of buoyancy in a slightly heeled condition vertically will intersect the

centreline at a point called metacentre. As long as the metacentre is further above the keel than

the centre of gravity, the ship is stable in an upright condition. The figure 25 illustrates the

common concept about stability of the vessels.

Figure 25 - Illustration of the stability of bottom-heavy (left) and top-heavy (right) ships with respect to the positions of their

centres of buoyancy (CB) and gravity (CG). Retrieved November 29, 2017 from Source: (52)

Moreover, the intact stability conditions is divided into four different loading conditions

as follows:

• Light displacement: The vessel is complete and ready for service in every respect,

including permanent ballast, spare parts, lubricating oil, and working stores but is



without fuel, cargo, drinking or washing water, officers, crew passengers, their

effects, temporary ballast or any other variable load. (53)

• Full displacement: Along with all the lightship loads, this conditions takes into

account all fresh water, cooling, lubricating, hydraulic, fuel, tanks, piping, fluids

and crew. All consumables like provisions, portable water and fuel are at full

capacity and draft at the maximum limit.

• Standard condition: Along with all the lightship loads, the vessel has all systems

charged. It means that all fresh water, cooling, lubricating, hydraulic and fuel

service header tanks, piping and equipment system are filled with their normal

operating fluids. Crew and effects are at their normal values. Consumables

(provisions, portable water and fuel) are at 50% capacity. This condition is

normally used for range and speed calculations. (54)

• Light arrival: This condition considers lightship loads, all systems charged,

including fresh water, cooling, lubricating, hydraulic and fuel tanks, piping and

equipment systems are filled with their normal operating fluid (54). Compared to

standard condition, this one has consumables (provisions, portable water and fuel)

at 10% of full load.

The calculations regarding damage stability are more complex than the ones from intact

stability, since your hull has some flaws, the behaviour is not so easy to predict and specialized

computational software utilizing numerical methods are usually used because the areas and

volumes may vary, making other methods too time consuming to find a reasonable solution.

In damaged stability, the vessel is analytical assessed as “Worst Intact Condition” by

opening various combinations of watertight compartments to the sea. The number of

compartments and their location are dictated by IMO regulations, SOLAS conventions, or other

applicable rules. Typically, these conditions are identified by the compartment(s) damaged.

(52)

As of 1880s, merchant ships were introduced to transverse and longitudinal waterproof

bulkheads, which can prevent a breach in a hull, flood the entire length of the ship. According

to (52) Transverse bulkheads, while expensive, increase the likelihood of ship survival in the

event of damage to the hull, by limiting flooding to breached compartments separated by



bulkheads from undamaged ones. Longitudinal bulkheads have a similar purpose, but damaged

stability effects must be taken into account to eliminate excessive heeling.

5.4. Marine Propulsion

Marine propulsion is the mechanism or system used to generate thrust to move a ship or

boat across water. While paddles and sail are still used on some smaller boats, most modern

ships are propelled by mechanical systems consisting of an electric motor or engine turning a

propeller, or less frequently, in pump-jets, an impeller. (55).

The decision regarding the ship propulsion is a strict process that must meet particular

requirements related to the application the project is designed to perform, ensuring a cost-

effective project aligned to safety standards, fuel source availability, reliable engine system,

and an accessible maintenance routine. For this reason, it makes this item as one of the most

important equipment, especially because it will influence all the other aspects related to the

general arrangement and so on.

One aspect to bear in mind is that this list is has not the purpose of classify in every tiny

detail the ways how to create thrust to the craft, but rather demonstrate the physics principles

supporting the marine systems, pointing out their advantages and disadvantages.

Some of the various types of propulsion systems and fuel sources are enumerated as

follows:

1. Diesel Propulsion: This system is the most commonly used propulsion system. It

works converting mechanical energy from thermal forces. This type of system can be

used in almost all types of watercraft.

Advantages:

• Diesel fuel is abundant available;

• Fuel price is steady for the next years;

• Robust in terms of maintenance and durability;

• Several equipment manufacturers in the market;

• Capital investment is reliable and easy to estimate.

Disadvantages:

• Often replacement of oil and wearing parts;

• Higher emissions of pollutants in the air;



• No flexibility in general arrangement;

• Due to the shaft is directed connected to the engine, vibration to the cabin crew

and hotel system is a constant concern;

• Manoeuvrability is dependent on bow thruster.

2. Nuclear Propulsion: This propulsion system is mainly used for naval vessels. It

works from a nuclear fission process, which is a closed system heating a steam

generator by nuclear reactors, making a turbines spin, and thus working as fuel to the

vessel. Of course, the whole system is highly complex and safety is one aspect, which

makes this system still sceptical about the usage on merchant ships, although some of

them are planned to be constructed with this propulsion system.

Advantages:

• System can last for long periods before being refuelled;

• High efficiency system, small volume of fissionable material is enough to the

system;

• Low CO2, neither particulate matter nor sulphur dioxide;

• Ideal for navy fleet, built to endure in dangerous and long missions;

• Maintenance and operational cost are lower given the lack of need of need for

fuel supplies for the main engines.

Disadvantages:

• Public opinion is not favourable due to past accidents involving land power

plants;

• High capital investment;

• Fuel source is not widely available in the market;

• Robust cool water system needed to keep the system steady;

• May experience problems of operation under shaking and vibrations.

3. Gas fuelled propulsion: This type of propulsion has the LNG (Liquid Natural Gas)

as the main source; however, the most effective arrangement includes a diesel bunker,

giving the system the chance to interchange what is the best option at a specific

condition. The use of natural gas propulsion is becoming an option for the shipping



companies, although the low prices of the petrol has postponed the expectations to

LNG becomes the main fuel source in the next 20 years.

Advantages:

• Same scheme of diesel propulsion;

• Only considering the technical point of view, only few modifications are

needed to use LNG as fuel source, although the major concern is develop an

equipment able to meet the requirements proposed by IMO framework;

• A way out for tightening emission regulations;

• Flexibility to retrofit built ships to use LNG;

• Reduction of sulphur and carbon dioxide by 90% and 20% respectively;

• Reports indicate LNG as the main fuel for the next decades;

Disadvantages:

• Availability of LNG is restrict and heavily linked to pipelines to distribute the

fuel;

• Need of new systems on board to mitigate associated risks;

• Arrangements of system is also one concern, essential to increase safety and

avoid explosions due to collisions;

• Necessity of training the crew to handle this new design system;

• LNG is heavier, requiring more space as compared to bunker oil.

4. Diesel-Electric Propulsion: In objective terms, this schematic is a type of hybrid

propulsion that uses the combination of an electric generator attached to a diesel

motor. (56) The technology has been in use since the early 1900s. Nowadays,

submarines and merchant ships incorporate the diesel-electric propulsion system to

propel themselves.

Advantages:

• Lower fuel consumption and emissions;

• Reduction of machinery space;

• General arrangement design is flexible;

• Excellent manoeuvrability;

• Lower propulsion noise and reduced vibrations.



Disadvantages:

• Installation cost is much higher;

• Skilled crew prepared to manage with complex systems;

• Need of isolation for the system devices in case of short-circuit;

• Redundant system seeking to avoid accidents and fires;

• Requirements regarding system failure are stricter.

5. Fuel Cell Propulsion: The system uses hydrogen as the main fuel component.

Electricity is created in the fuel cell without any combustion. The main process is

clean and therefore has been regarded as a very important alternative marine

propulsion system. There are various types of propulsion under the fuel cell

propulsion head like PEM (Photon-Exchange-Membrane) and the molten-carbonate

systems. (56)

Advantages:

• The fuel cells stacks are modular and power can be distributed over the ship

without huge losses of energy like the fossil fuels;

• The propulsion system is close to zero emission and may be the future of

ships in a long term;

• Vibrations and noise would be reduced by far due to no presence of movable

parts in the propulsion system;

• Fuel efficiency would increase constantly, reducing the necessity to refuel in

every single journey;

• Great alternative against nuclear energy. Additionally there are already few

prototypes and considerable researches to develop this type of propulsion.

Disadvantages:

• There are at least five different types of fuel cell systems and they differ

substantially from each other;

• Need of infrastructure to meet all criteria needed for safety assessment;

• The systems are complex and still expensive to be used as main power source;

• Hydrogen is the main source to have the fuel cells, making it expensive due to

electrolyse process to obtain the hydrogen itself;



• Lack of robust classification standards providing safe ways to storage and

handling of volatile fuels.

6. Hybrid Propulsion: A hybrid system has the main goal of improve the efficiency by

using two energy sources, one fuelled power source, such as a diesel engine and

another through a stored energy source, like battery banks or electric motor.

Advantages:

• Possibility to mix with many variations, such as connecting the internal

combustion engine connected directly to an electrical generator;

• Improve fuel efficiency by adding batteries, being able to stop the engine and

use the stored energy in the battery bank;

• Flexibility to have the best of each propulsion in just one system;

• System can reach high speed at lower RPM than a normal diesel scheme;

Disadvantages:

• The system will be more expensive due to the accommodation of two distinct

set of equipment;

• May not be appropriate for small boats, where the fuel efficiency is not a major

issue;

• Necessity of complex control systems to handle the new scheme;

• Maintenance may be more complex and expensive due to more items to care,

replace and check during the maintenance program.

7. Solar panel Propulsion: This schematic has the principle of transforming solar

energy into thrust by storing this energy into batteries. However, there are some major

issues regarding this propulsion system. At first, the arrangement and quantity of solar

panels to generate enough energy to move the ship. Lifespan and price of the batteries

is also one important concern. At last, the availability of sunlight is determinant and

this type of propulsion may face shortage of energy during long trips when the

weather is unpredictable, making impossible to generate energy from the sun for

several days if the chosen system on board is only by solar propulsion.



Advantages:

• As clean as wind energy, solar propulsions can generate as high as 40 kW;

• Renewable energy is global trend and do no harm to the environment;

• The fabrication and installation of solar panel is simple and reliable;

• If not used as main power source, can provide energy to hotel

accommodations;

• The use of solar panel, even partially can help to reduce the emission of

harmful soot and particulate pollution.

Disadvantages:

• Necessity of storage system to have energy and use it to produce thrust.

• The uncertainty about solar energy along all year long is one of the major

problems regarding the use of solar as main propulsion, although if used in

cooperation with other systems, solar energy can provide some support in

order to increase the energy efficiency.

• Solar power is variable depending on the global position;

• Solar propulsion rely upon adequate control system installed on board the

ship.

8. Wind turbine Propulsion: This type of system emerged as a renewable alternative

to reduce the huge amounts of pollutants emitted by fossil fuels in the marine

atmosphere. According to Sharda (56) however, the usage of wind turbine marine

propulsion has not started extensively in large commercial ships because of a

requirement of constant windiness. Besides, it encounters the same energy storage

issue and need for batteries on board in order to have the minimum to move the ship

along the way.

Advantages:

• It is free from exhaust pollutants;

• It is basically heat free propulsion, minor energy losses if compared to thermic

propulsion;

• Can help with fuel efficiency and reduction emissions of CO2;

• Wind turbine together with solar propulsion start being feasible to have a

green propulsion scheme;



Disadvantages:

• Since the embarkation is moving, it is hard to storage the energy from wind

turbines;

• Wind turbine may demands large space on board to be installed;

• Wind is unpredictable and can change without further notice;

• Limited quantity generation of power energy;

• Necessity to use batteries to storage the output power energy.

9. Battery-Powered Propulsion: This propulsion scheme brings an electric engine,

powered by battery bank, which are responsible to storage the energy and produce

thrust to move forward the boat.

Advantages:

• It offers a potential solution for small-to-medium sized ships;

• Lithium-ion battery gives a high energy density and possibility to recharge

considerable power over a short period;

• Electricity is a vast power source in almost all areas, even weak electrical grid

can be utilized as power source;

• Due to no movable parts, engine maintenance is less frequent;

• Noise and vibration reach very low levels.

Disadvantages:

• It is limited to short distance travels and very specific applications where the

electricity is generated by a green source;

• Batteries still have limited life span, weighing down the implementation for

all types of applications;

• Grid infrastructure may be needed in order to charge the embarkation after the

certain time

• Operating costs will not justify the investment in cases of big ships;

• Further technical development is still necessary for a full battery propulsion

to gain different niche in the market.



5.5. Ship Maintenance

Maintenance is one thing that keeps any mechanical equipment or machinery going.

Whether it is a small machine or a large structure, efficient maintenance can help with

prolonged life and favourable outcome (57).

In order to understand maintenance, it is extremely important to know the types of

maintenance programs used on ships:

• Periodic maintenance system: In this system, maintenance is carried out based on

a specific calendar of running-hours intervals. The ship and set of equipment

needs to be examined or replaced at exact period. The schedule needs to be

followed without question to ensure that everything is in proper order. (58)

• Corrective maintenance system: It is known as breakdown maintenance, this

scheme does not follow a schedule plan, and the replacement is carried when the

equipment or machinery breaks down. It tends to be used only in emergencies.

(58)

• Predictive maintenance system: This system also has carries the name of

Condition maintenance. It is a proactive approach to solve unplanned

interruptions due to equipment failure. The scheme relies on sensors, which

regularly scan equipment and machinery, checking for problems. (58)

5.6. Mooring

The word refers to any permanent structure to which a vessel may be secured Examples

include harbour basins, quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship

is secured to a mooring to forestall free movement of the ship on the water. An anchor mooring

fixed a vessel’s position relative to a point on the bottom of a waterway without connecting the

vessel to shore. As a verb, mooring refers to the act of attaching a vessel to a mooring (59). This

subchapter will explore the common schemes for mooring and also brings an alternative for an

automated mooring system in order to do everything autonomously without necessity of

workers around to fasten the cables.

There are several known methods of mooring, and the common ones according to (60)

are Mediterranean mooring, Baltic mooring, Running mooring, Standing mooring, Spider



mooring buoys, Single point or single buoy mooring, Conventional or multi buoy mooring,

Ship to Ship Mooring. Additionally, mixed mooring schemes are used when the local conditions

require using more lines than they were designed for.

Being straight forward, an automated mooring system would eliminate the conventional

mooring lines, demonstrating to be an essential equipment for the future prospects of unmanned

navigation. The state-of-art technology is already in the market and according to Port

Technology (61), the company Cavotec SA has developed a system called MoorMaster, which

is a vacuum-based automated mooring system capable of keep the vessel safely moored in even

in hash situations. The technology is currently in operation at bulk and container handling,

passenger ferry in different parts of the planet.

5.7. Collision Avoidance at Sea

For better understanding of collision avoidance, it is necessary to have knowledge about

the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS),

by the International Maritime Organization. Although COLREGS is designed for ordinary ships

operated by people on board, their key elements are the source to develop an automatic collision

avoidance system, either as decision support system for the crew or in autonomous operation.

In an autonomous system implementation, COLREGS implicitly impose requirements on

the information that must be provided by sensor systems, and the correct actions that should

occur in hazardous situations. Automation operation of a ship requires that guidance, navigation

and control is performed with high reliability, fault-tolerance, and safety, including real-time

perception of the ship’s surrounding in order to avoid grounding and collision with other ships,

vessels, people, marine mammals or other obstacles that may be encountered (62).

The first part of this topic emphasizes the explanation of the navigation rules demanded

by International Maritime Organization. The rules of the road at sea are organized into five

parts, as represented by the Figure 26.

As of January 2016, an extra part F has been added in the sea rules book, dealing with the

verification of compliance.



Figure 26 - Representation of COLREG parts. Retrieved September 15, 2017 from Source: (63)

6. Overview of Unmanned Vessels 6.1. Initiatives and researches under development

Some major initiatives are present regarding unmanned navigation, highlighting the

AAWA Project in Finland and the MUNIN Project both in the field of shipping. They are

cooperating among companies, and universities on the EU-level. Besides, other countries

mostly in Europe and US are funding researchers in this field. Regarding the applicability of

unmanned vessels, American navy had already incorporated unmanned solutions to their fleet.

Moreover, some companies are offering advanced autonomous vessels seeking to replace costly

survey vessels into small autonomous devices, capable of working continuously for a fraction

of the price.

6.1.1. MUNIN Project

As mentioned, the initiatives propose concepts to build a standard for unmanned shipping

navigation. Thus, there are different alternatives that combined, will turn into an autonomous

ship. The Maritime Unmanned Navigation through intelligence in Networks (MUNIN) defines

two generic alternatives, which are (64):

• The remote ship where the task of operating the ship are performed via a remote

control mechanism e.g. by a shore based human operator.



• The automated ship where advanced decision support systems on board undertake

all the operational decisions independently without intervention of a human

operator.

Within MUNIN’s idea of an autonomous and unmanned vessel, both generic alternatives

will be combined in a holistic concept. Developing and validating a suitable mixture of remote

and automated technology for ships will be the core task of the MUNIN project. The on-board

systems approach that is implemented in MUNIN is illustrated as the following figures 27 and

28.

Figure 27 - The Autonomous Ship, as it understood in the MUNIN project, is a symbiosis of the Remote Ship and the Automatic

Ship. Retrieved December 04, 2017 from Source: (64)

Figure 28 - MUNIN's concept to solve the Unmanned Navigation. Retrieved December 04, 2017 from Source: (64)



6.1.2. Yara Birkeland

Among all, the project designed by KONGSBERG, Marin Teknikk and supported by

DNV GL for the Norwegian fertilizer company Yara, named Yara Birkland is not anymore only

a concept, programmed to be delivered by the second half of 2018. The first tests with a captain

and small crew are schedules to start by the end of 2018 and fully autonomous operation is

expected in 2020.

The vessel will be the world’s first fully electric and autonomous container ship, with

zero emission. KONGSBERG is responsible for development and delivery of all key enabling

technologies including the sensors and integration required for remote and autonomous ship

operations, in addition to the electric drive, battery and propulsion control systems. It is

programmed to sail within 12 nautical miles from the coast, between three ports in southern

Norway; the whole area is completely covered by the Norwegian Coastal Administration’s VTS

system at Brevik. (65)

As of September 2017, the a six meter long scale model of the Yara Birkland is

undergoing comprehensive tank tests in Trondheim, Norway at SINTEF Ocean facilities.

According to (66) the president and CEO of Kongsberg, Geir Håøy claimed that the initial tests

of the model were successful, proving both concept and the technology.

Figure 29 - Yara Birkeland projection. Retrieved December 04, 2017 from Source: (65)



Figure 30 – Scale model of the final design of the autonomous vessel. Retrieved December 04, 2017 from Source: (66)

6.1.3. The ReVolt

Another project regarding autonomous navigation is the concept developed by DNL GL

since 2013. As mentioned, The ReVolt is just a concept of an autonomous, fully battery

powered and highly efficient general cargo ship but also provides a concrete outcome and

inspiration for design offices and companies eager to develop new systems in autonomous field.

Moreover, DNV GL has built a model scale of 1:20, which is currently being tested in Norway

Sea.

The basic design particulars were optimized to increase the load capacity as much as

possible. The length defined by DNV GL is about 60 m and beam 15 m, featuring a ballast free

design, cargo capacity of 100 TEU, operational range of 100 nm and service speed of 6 knots.

Propulsion system built with twin screw, podded propulsion and two bladed propellers.

One setback pointed out by DNV GL about fully battery-powered ship is the charging

infrastructure necessary on every port in order to make the ship functional for the whole

journey. DNV GL estimated a duration of 4 hours minimum to charge all the packages of

battery. Another remark regards the source of electricity; the vessel can only be considered zero

emission when the electrical energy is generated by a clean source such as wind power, solar

power and hydroelectricity.



Figure 31 - The ReVolt DNV G Lateral view. Retrieved December 04, 2017 from Source: (67)

Figure 32 - The ReVolt DNG GL Back view. Retrieved December 04, 2017 from Source: (67)

6.1.4. Advanced Autonomous Waterborne Applications Initiative (AAWA)

The initiative led by Rolls-Royce, brings together universities, ship designers, equipment

manufacturers, and classification societies to explore the economic, social, legal, regulatory and

technological factors, which need to be addressed to make autonomous ship a reality. (68)

AAWA combines the expertise of some of Finland’s top academic researchers from

Tampere University of Technology; VTT Technical Research Centre of Finland Ltd; Abo

Akademi University; Aalto University of Turku; and leading members of the maritime cluster

including Rolls-Royce, NAPA, Deltamarin, DNV GL and Inmarsat. (68)



For remote controlled and autonomous ships to become a reality, AAWA (69) defines

critical questions to be answered:

• What technology is needed and how can it be best combined to allow a vessel to

operate autonomously and miles from shore;

• How can an autonomous vessel be made at least as safe as existing ships, what

new risks will it face and how can they be mitigated;

• What will be the incentive for ship owners and operators to invest in autonomous

vessels;

• Are autonomous ships legal?

• Who is liable in the event of an accident?

As of 2016, AAWA has introduced the project’s first commercial ship operator: ferry

operator Finferries and dry bulk cargo carries ESL Shipping Oy. The announcement came at a

conference presenting the finding of the initiative’s first year of research at Helsinki’s Finlandia

Hall. (68)

Moreover, Rolls-Royce has developed a concept for a remote operating centre. This state-

of-art operating centre has the goal to redefine the way which vessels are controlled. Instead of

copying existing wheelhouse design, the Remote Operating Centre (ROC) used input from

experiences captains to place the different system components in the optimum place to give the

master confidence and control. The aim is to create a future proof standard for the control of

vessels remotely. (68)



Figure 33 - Remote Operating Centre designed by Rolls-Royce view 1.Retrieved December 05, 2017 from Source: (68)

Figure 34 - Remote Operating Centre by Rolls-Royce view 2. Retrieved December 05, 2017 from Source: (68)

6.1.5. DARPA Sea Hunter Unmanned Surface Vehicle

Military applications are by far the most used for unmanned navigation. As of second

semester of 2016, US Navy has launched a 40 meters long self-driving sub hunter under the

name of Sea Hunter. It sports a trimaran hull shape, designed to travel long journey without a

single man on-board. According to article on Dailymail Online written by Prigg (70), US Navy



has funded 20 million American dollar to develop this surface vehicle. It will undergo two years

of testing in order to assure the safety following international norms to operate at sea.

Most of data available about the DARPA prototype does not have a solid source, and only

few technical details are available to the community. Two diesel engines, reaching speeds of

27 knots, power the vessel; however, no information about the engine displacement is informed.

Sea hunter is also equipped with an array of sensors, radar, and cameras seeking to avoid

collision with other vessels.

Another feature regarding Sea Hunter is mentioned by Fiddian (71) on website article

published by Copybook is the fact it has a fully autonomy suite able to keep the operations in

line with existing maritime laws. The state-of-art hardware and software will be on constant

watch to ensure Sea Hunter can work alongside standard manned craft with no dangers posed.

Figure 35 - DARPA Sea Hunter concept. Retrieved December 12, 2017 from Source: (72)

Figure 36 - DARPA Sea Hunter view. Retrieved December 12, 2017 from Source: (73)



7. Concept of operations 7.1. Comparison of concepts

After all the material presented above, chapter 7 has the main goal of finding a suitable

concept device to dredge mud in a harbour basin. The device should work autonomously,

cutting operational costs and saving time to perform the maintenance dredging. For this work,

the author idealized three different concepts in order to solve the given problem. The properties

of the idealized devices are compared and after a multi-criteria analysis, the most prominent is

chosen for further development.

7.1.1. Autonomous water injection dredging device

PIANC (1) defines the water injection dredging as a technique that injects high volumes

of water with low-pressure pumps through a series of nozzles on a horizontal jet bar into the

sediment. It creates a fluid mud that will have a limited vertically movement from 1 to 3 metres

above the bed and a horizontal movement that will flow the mud to deeper water due to the

density current.

This kind of technique is very cost effective in cases where the soil has cohesive

properties and undrained shear strength not too high, so the material will not settle to quick on

the bed. Some special cases where the soil has non-cohesive properties but the grains are fine;

the employment of water injection dredging is an option.

Figure 37 – Base Principles of Water Injection Dredging. Retrieved December 10, 2017 from Source: (1)



The idea behind of using water injection dredger to perform tasks autonomously is still

new and sounds feasible if small-cheap dredging devices can work as swarm to locate and

sweep the areas that suffer from sedimentation. The form factor would not be limited to a vessel

like normal Water Injection Dredger fleet, although underwater devices would normally require

more attention to keep it stable due to the six degrees of freedom rather than three degrees of

freedom as a regular vessel. Moreover, lack of radio communication, necessity of cables to

transmit data and difficult to locate the device by sight would provoke concerns of collision in

the harbour basin. For this reason, the most feasible form factor is a vessel like as small as

possible.

Below is possible to check out the sketch done by the author regarding an initial concept

for the autonomous water injection-dredging device.

Figure 38 - Concept schematic for autonomous water injection dredger. Source: Author

7.1.2. Autonomous suction dredging device

Unlike the water injection, this technique sucks the sediment through a tube, like a big

vacuum cleaner. Among the suction dredgers, the plain suction dredger, which there is no tool

at the end of the suction pipe is the most common. Furthermore, some others variations like

dustpan suction head, draghead head, cutter-suction and auger suction.

The suction dredgers are widespread among dredging works. They can work with

different soils and the production rate is easier to determine if compared to WID. Since the



sediment is going through the tube, there are two approaches in order to discharge the material.

The first one is attach a discharging pipe in order to transfer the material directly to land, this

way not requiring a storage area for the mud. However, this approach would create some

mobility problems, being not feasible from the technical point of view for a cloud of

autonomous suction devices. On the other hand, using a hopper to storage the material would

force the device to be bigger and heavier than expected, also requiring an auxiliary system to

discharge the material in selected sites. Even though the issues present on the second approach,

it seems to be more feasible, although conservative.

Another point to reminder is what tool would be more appropriate to pick for this

autonomous self-propelled suction device. Cutter head and Auger screw are suitable to dredge

mud, but considering the upward force exerted on the soil to cut the mud layer, a complementary

system with spuds would be required to give proper stability reducing the productivity for a

small-scale vessel. For this reason, use of dustpan suction head would fit for the concept, but

further replacement for a more efficient may be required.

One schematic in Figure 39 was developed by the author in order to idealize a concept

for this dredger proposal.

Figure 39 – Concept schematic for autonomous suction dredger. Source: Author



7.1.3. Autonomous submerged walking dredger with floating hopper

This third concept introduces an autonomous submerged dredger, which will do the

dredging process by cutting the soil, sucking through the pipe to the hopper-vessel. At the first

sight, the concept may look super efficiency, but the fact that the system requires at least three

components, the hopper-vessel, the pipeline, and a bed supported dredger able to walk and

excavate the soil.

Although, the system can be a good option for deep-water depths, where others dredgers

would require a robust set of equipment to do the job it. The major challenge for this concept

seems to be the dredger itself, because for deep-waters, the control over movements from the

surface may be very difficult.

There are others concerns about the system that it would be answered to proof it is

feasibility. The pipeline should be retractable to return the equipment alongside the hull, the

feasibility to have a hatch under the hull to storage the dredger is also an option when moving

to different dredging areas.

An initial idea about the concept for this submerged walking dredging device is presented

below in the Figure 40

Figure 40 - Concept schematic for autonomous submerged dredger with floating hopper. Source: Author



7.2. Concept choice by Multi-criteria analysis

In this chapter, the concepts introduced in the previous paragraphs go through a multi-

criteria analysis to decide which one would be the most promising for the autonomous dredging

of mud.

The set of criteria is presented in subchapter 2.2. The concepts will receive a score from

0 to 10 for each criterion and at the end; the final score will define the right pick according to

multi-criteria analysis. Below a brief explanation for each argument is attached with their

respective grades. In addition, a weight factor from 0 to 5 determining the importance of the

criteria is assigned to make the final sum more fair.

Stability

During the dredging process, stability is fundamentally important to obtain dependable

operation. Thus, this criterion carries a maximum weight factor of 5.

The autonomous water injection and suction solutions have a vessel-like hull; therefore,

the stability for both can be in a way more predictable by using computational tools, but may

require wide bodies to handle the whole set of equipment on board and still be stable. For this

reason both WID and Suction dredger will receive 9 for this criterion. On the other hand, the

submerged walking solution may work properly for shallow waters, but once it gets deeper, the

stability can be a problem, resulting in a grade of 6 for this concept.

Maintainability

This point addresses the easiness to perform maintenance and the period between each

periodical maintenance. Maintainability will not affect much the functionality, considering the

owner follow accurately the maintenance plan. It carries a weight factor of 4

For this criterion, the concept regarding the underwater walking dredger will need more

effort to lift the device, detach to from the pipeline in order to do the maintenance, thus the

grade for this device is 6. Both autonomous WID and autonomous Suction dredger operate on

the water surface, being easier to undergo maintenance. The grade for these two surface devices

is 8.

Reliability

If the company wants someone to buy their product, it needs to be reliable and work as

programmed. For this reason, weight factor of 5 is assigned to this matter.



The underwater device will be more exposed, forcing the designer to care more about

being waterproof and robust. Therefore, a grade of 5 is enough for this concept.

On the other hand, the autonomous WID in theory does not need much further support

from auxiliary systems to work, and Water Injection is a technique already proven by the

market, pushing the grade to 9 points. The suction dredger will require design that is more

complicated, especially because of the loading and unloading conditions. It gets 7 points.

Safety

It needs to go smooth and harmless to people and other vessels around. Essential criterion,

receiving weight of 5.

All the three concepts were idealized in a way that no discharge line is displayed on the

water surface, although the underwater walking one has a pipeline attached to the floating

hopper, which can eventually rupture and provoke an accident, lowering the grade to 7. Both

WID and Suction devices have similar operation, although the WID pumps waterjets as the

main process, and the suction device needs to suck the material, accommodate equally in the

hopper, and sail to discharge the sediments in a specific area. It exposes more the systems to

risks. It gets 9 points and 8 points, respectively.

Capability

This point comprises how much the concept can would be able to produce during working

hours. A weigh of 4 is accounted to be appropriate.

The suction and submerged devices are easier to measure how much of mud was extracted

from the dredging site, getting 9 for both of them. Unlike, the WID needs further studies to

check the production rate, although some models are available in order to measure the figures,

hence, it receives 7 for this subject.

Energy supply

Choosing the energy source is closely related to the cost-benefit of polluting less the

environment and reducing the costs with fuel. Every year the agencies are becoming more and

stricter about fossil fuels, and it is important to have concepts ready for renewable energy

sources. Although, this work does not treat this topic as a key element, pushing the weight factor

to 2.

WID and Suction devices receive 9 points. On the other hand, the underwater one will

require more complicate schematic to power on. It gets 6 points.



Size & Workability

As an autonomous concept, the market would be interested in devices able to work

continuously with a user-friendly interface, being as small as possible. This criterion received

weight of 5.

The water injection dredging is the only one not loading material to any storage area and

since the working area is restricted to harbour basins, the weather should not create much

influence on it. On the other hand, the suction device and underwater dredger may have the

workability reduced due to the hopper attached, which makes the draft vary whenever loading

and unloading is undergoing. No doubts, the size for the WID version is rather than smaller if

compared to the others two schematics. Therefore, the WID gets 8, the suction dredger gets 7

and the underwater one receives 6.

Operational costs

It comprises of measuring how much it would affect the OPEX. Considering the device

will become an asset; it will generate indirect income to the harbour basin, and money is

necessary to maintain it working properly. The weight of 5 is assigned to this issue.

No doubts, the WID concept is the one with the lowest operational costs, with almost or

no auxiliary system necessary to support the system during the time on the water. The others

two concepts necessity more watch in order to do perform the entire process of dredging. WID

gets 10 for this subject, while the others score 7.

Building costs

Unlike the operational costs, this matter relates to CAPEX, which stands for the capital

used by a company to purchase new assets. The final price to build is extremely important,

however innovative concepts tends to be more expensive at the first place. Thus, the weight

factor for this issue is 4.

In a cost-benefit, the concepts with vessel shapes will not face a major problem to build,

but the underwater one is expected to be more complicated to build. WID gets a score of 8,

Suction option gets 7 and underwater device scores 6.

Supervision

For safety reasons, a reduced staff is still necessary to oversee the system through a shore

centre control. At the current state, this criterion is super important and receives a weight factor



of 3. It is expected in 10 – 15 years from now, the supervision will be only required during

emergency cases.

All three concepts are idealized to have just one supervisor in a portable shore centre

control to take over command if any emergency occurs. This way, all ideas receive 8 points.

Final Results for multi-criteria analysis

According to the author analysis, the concept using water injection dredging method is

the most viable solution for further development. This concept will be presented with general

arrangement, production estimation and operational concept for an autonomous operation in a

harbour basin where is necessary to dredge layer of mud periodically.

Table 2 - Final results for the multi-criteria analysis. Source: Author

ID Criterion WeightFactor AWID Suction Underwater1 Stability 5 9 9 62 Maintainability 4 8 8 63 Reliability 5 9 7 54 Safety 5 9 8 75 Capability 4 7 9 96 Energysupply 2 9 9 67 Size&Workability 5 8 7 68 Operationalcosts 5 10 7 79 Buildingcosts 4 8 7 610 Supervision 3 8 8 8 Totalweightedscore 855 781 655 1st 2nd 3rd

7.3. First design

In order to materialize the first design for the AWID device, one subchapter is destined

to develop design concepts according to the basic requirements. Even though, it is important to

reminder that the main goal is not to proceed to structure analysis or design itself, but the

operational concept to dredge layer of mud for an Autonomous Water Injection Dredger.

Considering the device in question needs to be as small as possible, but still stable to

perform the job; in literature a water injection dredger called Odin owned by Van Oord has

particulars close enough for the first design of the autonomous device. The main data of Odin

WID is right below:



• Length Overall: 17,5 meters;

• Width :4,5 m;

• Depth: 1,8 m;

• Draft: 1,45 (loaded);

• Jetting power: 220 kW;

• Engine power: 2*95 kW;

• Total power installed: 410 kW;

• Jet bar width: 4,4 m;

• Dredging depth: 10 m.

7.3.1. Main particulars for Autonomous Water Injection Dredging

Taking into account the Odin dredger as reference, the main dimensions are chosen based

on realistic numbers obtained from PIANC (1). Some important modifications are necessary to

adequate the equipment for a completely new operating system. Odin dredger carries a jetting

power system of 220 kW, and 2 diesel engines with capacity of 95 kW each. The total power

installed is 410 kW. Since there is not further studies regarding the efficiency of the concept

proposed, 500 kW of total installed power is seems to be feasible, by adding more power for

the water jets and keeping the engine displacement as same before.

Being conservative for a stable work, the overall length reduces to 15 m, beam remains

unaltered in 4,5 m, depth and draft slightly change to 1,8 m and 1,6 m, respectively.

The dredger considered as reference has a limitation of 10 m dredge depth; thus, it is

assumed a longer jet beam, able to reach at least 20 m depth, adjusting the equipment to deeper

basins. Equipping the system with a longer beam would need more power, although is expected

that only few minor changes affect the whole schematic. Not less important, the jet bar width

follows the vessel width with 4,5 m. In Table 03 is possible to check main data used to design

the equipment.



Table 3 - Main data for AWID concept. Source: Author

EnergyrequirementJettingPower 310kW

Propulsionpower 2*95kWTotal 500kWMainparticulars

LengthOverall 15mBeam 4,5mDepth 1,8mDraft 1,6m

JetbeamdimensionsJetbarbeam 4,5m

Maximumdredgedepth 20m

7.3.2. Propulsion choice

For this point, the propulsion system list presented in chapter 5.4 will suggest the most

promising propulsion system for a current design. The choice is based on infrastructure

availability, easiness to implement the system, fuel source availability, simple maintenance plan

among others. The final design is supposed to be address to small-medium harbour basins,

where maintenance dredging costs may represent a burden. The choice of green energy source

over fossil source is promising for the future when the latter becomes not viable anymore. At

current moment, the viable options are:

• Diesel propulsion: It represents the present, being reliable and straightforward to

use. One disadvantage regarding internal combustion engines is the lower energy

efficiency if compared to other newer propulsion systems.

• Diesel-electric propulsion: Especially used in modern cruising ships, this

propulsion system uses diesel engines to generate electricity to electric engines

and thus transfer power to the shaft. For small power demands, where the fuel

consumption, vibrations and noise are not major concerns, this propulsion scheme

seems not to be feasible.

• Gas fuel propulsion: Much is being talked about gas fuel propulsions, in special

with the use of LNG as main ship fuel source. However, setbacks as risk of

explosion in case of leakage and need of low temperatures to storage LNG may



jeopardize the use for small-medium vessels, being only feasible for cases where

pollutant emissions are a major concern.

• Battery-Powered Propulsion: Having electric engines, means no movable parts,

less wear and almost maintenance free. Although, batteries as storage power still

have low energy density, and low lifetime estimated in a range of 5-10 years.

These setbacks still keep a battery-powered option counting on further

developments to become the first option.

The diesel propulsion scheme is the most appropriate for the application in order to reduce

operational costs and be able to predict the maintenance plan, but is for sure the most

conservative one. Further developments for the future would probably lead for the use of

electrical non-movable engines powered by batteries in order to have almost maintenance free

equipment and better efficiency.

7.3.3. Current WID fleet by PIANC

From PIANC (1), the report some facts about WID operation. The sailing speeds during

operation are usually between 1 to 2 knots. Moreover, it remembers that some WID vessels

have been equipped with heave compensators to maintain the jet bar at a certain depth. Another

important point is the manoeuvrability, which needs be good, pushing the use of bow thrusters

and double propulsion to perform the work in a more efficient way.

If compared to others types of dredging methods, WID devices are smaller and easier to

carry. Usually auxiliary equipment is not required in most of cases during operation.

Furthermore, the following Table 04 brings an overview from the current WID fleet

extracted from PIANC report about water injection dredging.



Table 4 - Overview of WID dredgers as per June 2010. Adapted from PIANC (1). Source: Author

ID VesselnameMaximumdredge

depth(m)

Jetbarwidth(m)

Jetpumpdieselenginepower(kW)

OwnerCompany

1 Maasmond 21 12 1250 VandeKamp2 Parakeer 26 13,9 1194 DEME3 Dhamra 22 12,6 1012 DEME4 Wodan 20 12 918 VanOord5 Jetsed 25 13,4 852 VanOord6 SagarManthan 28 11 746 VanOord7 Njord 19 12 716 VanOord8 Antareja 28 11 700 VanOord9 HolBlank 21 10,2 662 BremenPorts

10 Steubenhoft 21 10 662 NiedersachsenPortsCuxhaven11 Iguazu 27 12,2 660 VanOord12 Arca 30 12 608 Boskalis13 BT208 21 11 600 WeeksMarinaInc.14 NorhamCamorim 26 11 558 VanOord15 HAM922 20 6 502 VanOord16 DragaTocantins 20 8 447 VanOord17 DragaRioMadeira 20 8 447 VanOord18 Akke 24 11,8 442 Meyer&VandeKamp19 Norma 19 8,8 440 Boskalis20 HolDeep 18 8,1 346 BremenPorts21 Odin 10 4,4 220 VanOord22 Baldur 7 2,5 75 VanOord

7.3.4. General Arrangement

Gathering all information provided in previous chapters, the general arrangement is

developed following the minimum requirements for a small, light, stable and with good

manoeuvrability. The main design sports a mono hull made of aluminium and small

superstructure close to the amidships to fit control systems and equipment necessary to

communicate with the control shore. In order to keep the manoeuvrability in good levels, two

independent thrusters and two bow thrusters are used on board. Since the maximum dredge

depth is 20 m, a retractable jet beam is idealized to reach the required dredge depth according

to required application. Two inlets to provide water to the jet pumps are located under the hull

at the right side of the amidships. Rubber fenders are presented in entire perimeter of the vessel

in order to absorb possible shocks and avoid further damaged on the hull when berthing. Two

diesel engines are located at the stern, followed by two water pumps and fuel tanks at amidships.

Drawings with the concept idea is illustrated in Figure 41 and Figure 42.



Figure 41 – General Arrangement for AWID - Lateral view. Source: Author

Figure 42 – General Arrangement for AWID – Superior view. Source: Author

7.4. Production capacity estimation

In order to state an operational concept, it is extremely important to define what would

be an acceptable production capacity for this autonomous water injection dredger. According

to Swart (5), the production is expressed in two different figures: the mud volume and the

distance the sediments needs to travel. Moreover, the mud travels a limited distance, turning

this point essential to estimate the production capacity of the device.

PIANC (1) reports a table with production rates for different Water Injection Dredging

projects, where is possible to have a first idea of reasonable values for the expected production

rate for the small autonomous water injection dredger. Realistic figures for production rate

range from 500 to 1000 m3/hr according to the Table 05 extracted from PIANC report number

120 – 2013 (1)



Table 5 - Production rates during WID projects. Retrieved December 10, 2017 from Source: (1)

ProjectName SoilDescriptionSedimentVolume(m3)

Duration(hours)

Productionrate(m3/hr)

EponHarbour,Delfzijl,TheNetherlands

Silt&sandD=0,3mm 160000 200 800

HaringvhetHarbour,TheNetherlands Silt/Clay 120960 252 480

CrouchRiverUnitedKingdom Clayedsilt 6480 12 540

UpperMississippiRiver,1992

SandD=0,3-0,4mm 6160 44 140

Calumet,1994 SiltD=0,004-0,05mm 12048 24 502

EastandWestCalumetfloodgates

SiltD=0,004-0,05mm 18360 17 1080

Michoud,2002 SiltD=0,06mm 178656 96 1861

MississippiRiverGulfOutlet,2003 Silt 268800 96 2800

WeserEstuary,Germany,2009

SandD=0,6mm

660000(peryear) 1200 550

ElbeEstuary,Germany,2009

Sand&SiltD=0,05-0,6mm

1500000(peryear) 2000 750

Since the goal of this report is to develop the strategies, standards and constraints

related to the system, the production rate is roughly estimated conservatively. For this task,

Swart (5) adapts in his master thesis a formula from Verhagen (74) to estimate production in

cubic meter per hour for the AWID device:

Pr = 𝑓>&% ∗ 𝑠)*%' ∗ 𝑤B' ∗ 𝑣B' ∗ 3600

Where,

Pr = production rate [m3/hr]

𝑓>&% = jetting factor [-]

𝑠)*%' = effective intrusion depth [m]

𝑤B'= width beam [m]

𝑣B'= hauling velocity [m/s]

The jetting factor varies from 0 to 1 and it is a tentative to correct the fact that the jets are

located at a certain distance from each other, meaning the flow created does not carry the same

amount of mud for every nozzles, consequently reducing the production. Value of 0,5 seems to



adequate to a realistic work. For effective intrusion depth, which according to Swart (5) is an

estimation that describes the limited amount of available mud, a value of 0,3 m is chosen as

found in literature by Van Rijn (14) and Verhagen (74).

The width follows the one defined in the general arrangement, which is 4,5 m. The last

factor to define is the hauling velocity, which changes the behaviour of the system. Swart (5)

describes that when hauling velocity is high, a certain amount of water is spread over a large

area, resulting in a lower amount of water added per unit area. On the other hand, for small

hauling velocities, more jet water is added per unit area, resulting in a mixture with lower

density. The value of 0,5 m/s seems to be realistic according to Verhagen (74)

Applying the values mentioned above, a theoretical production of 1215 m3/h is found.

However, in real life this outcome is exaggerated and due to it is main principles and complex

operational system, an efficiency rate about of 40% takes into account all constraints, like

sailing time, refuelling, maintenance, etc. A net production of 450 m3/hr seems reasonable to

be achieved

7.5. Operational concept

This part of work aims to achieve standards for the conceptual system, specifying the

operational processes, operating modes in different situations, range area of work and, working

hours per day.

In order to find a solution to the proposed concept, it is necessary to solve the unmanned

navigation for the equipment. Unmanned means just that no one is on board, however some

supervision over the air may be require in special occasions. The concept is optimized to work

in small-medium harbour basins in order to mainly dredge fine layers of mud, however further

studies may prove that the concept can be used for others non-cohesive soils.

The equipment in question has an estimation net production of 450 m3/hr, although it not

possible to put the equipment to work 24/7 due to weather, current and light conditions.

Considering 6 hours of work per day, the maximum net production by unit spins around

2,700.00 m3/day. The AWID in question will reach up to 1 knots during dredging works, and

up to 10 knots while is moving around. Moreover, the concept is expected to work only in

territorial waters, no more than 15 km away from shore centre control. An average travel

distance of 1,5 km regarding the transport of sediments from the dredging site to the settling

point is considered feasible.



The concept also contemplates an automated mooring system, which is already available

in the market for some specialized companies, being used in different applications. It is

expected no problems to implement this state-of-art mooring system for the Autonomous Water

Injection Dredger. Moreover, avoiding the requirement of having people at berth to fasten

mooring lines will save plenty of time and make the operating more productive. The mooring

system in question is supposed use suction pads providing real-live data about all loads acting

on the vessel while at berth.

Swarm operation is also included in the concept for cases where the demand is more than

one device to do the job. In the next paragraph is possible to find more explanations about the

proposed operating modes.

For this work, a hypothetical harbour basin situation directly at the sea (Figure 43) has

two Energy Environments. The first known as Low Energy Environment (LE.E), which is

inside the sheltered area. The second, High Energy Environment (H.E.E) works as a supply of

sediments that in this hypothetical case is due to the tidal current.

The main goal is to transport back the sediments in L.E.E to the H.E.E, so the fluidized

soil layer will reach higher currents and the depth will keep navigable inside the harbour basin.

Figure 43 – Mud sedimentation scheme in harbour basin next to sea. Source: Author



7.5.1. Operating modes

Five different of operating modes are proposed to solve the unmanned navigation, being

the following:

• Remote-controlled mode: This mode is related to level 1 of autonomy proposed

by Sheridan (22), which needs someone taking over the total control of the vessel

in order to make the decisions. Therefore, the mode in question is supposed to be

a redundancy, being used in cases where the system cannot handle to perform the

work by itself and needs to return to the base as soon as possible.

• Waypoint mode: It is known as automated mode, being more or less at level 5 of

autonomy, where the working area is completely mapped with waypoints

determining the route path and exact points to be dredge. It is limited and does not

take decision but just perform tasks programmed beforehand the mission. It may

require a supervisor to oversee the progress and if something goes wrong, manual

(remote-controlled mode) is activated. Furthermore, an avoidance collision

system warning the supervisor when unexpected obstacles appear is required to

have a proper use of this mode. (See Figure 44).

Figure 44 - Waypoint mode representation. Source: Author



• Autonomous mode: Even though is just a concept, this mode relies on complex

Artificial Intelligence algorithm to take decisions based on situational awareness,

being able to find efficient ways to do the job. It will not require supervision, and

operator may take over control the operating if the targets outputs are much lower

than expected. The device will be equipped with survey equipment in order to

know the exactly which parts in the harbour basin needs dredging and the

autonomous control system will determine the expected production rate and best

path. (See Figure 45)

Figure 45 - Autonomous mode representation. Source: Author

• Swarm mode: It is a complementation of the autonomous mode. For this mode,

the system will operate as a symbiosis, sharing live data with the fleet engaged to

perform the dredging. This mode can improve the efficiency and reduce the time

necessary to complete the task. On the other hand, more variables need to be taken

into account for this mode and probably a defined range area for each unit is one

solution to avoid any collision. (See Figure 46)



Figure 46 - Swarm mode representation. Source: Author

• Emergency mode: In failure of all operating modes, emergency mode retrieves

the actual location of the device and immediately set the path back to the dock. In

case of breakdown, the device will keep emitting a rescue signal with coordinates

to the centre control forcing the supervisor to request a rescue boat to tow the

device.



8. Conclusions

As conclusion, it is possible to realize that this piece of work attempts to be an initial, but

solid research regarding a new concept in dredging field, considering that no similar concepts

are available publicly. The whole work tries to relate the literature available to become material

useful for the concept of operation idealized for such dredging device.

Keeping the same page, the concept does not focus on structures, but focus on ship

operations to develop a new autonomous concept of operations not explored yet. In addition,

principles extracted from different literature are present to explain what the author proposes.

Lack of data justifies the fact of being conservative during some passages, however with the

help of multi-criteria analysis, the method of Water Injection Dredging demonstrated to be the

most promising to become unmanned, especially because in almost of cases there is no need of

auxiliary systems for the operating.

Furthermore, the author goes through a feasibility study, which visits different important

matters to understand if the dredging market and customers would be a reasonable application

for unmanned vehicles. The outcome is surprising, the breakdown of the dredging market shows

two markets, the first one called “closed market”, where only United States and China are part

of it. On the other hand, few key players rule the global “open market”, who have not

demonstrated desire to share or provide cheap equipment for maintenance dredging. Therefore,

the feasibility demonstrates that is necessary to change the approach, looking for new

investments and people eager to order to introduce such devices in the market.

In addition, the thesis goes through some initiatives about unmanned navigation. Among

all applications, short-sea shipping seems to the favourite of specialists, having the first

autonomous container feeder design built in scale model undergoing tank test in Trondheim,

Norway.

The operational concept is initially designed to perform maintenance dredging in harbour

basins, however further developments can check if the concept is feasible for other sites like

locks and channels. Talking about the main outcome extracted, the author proposes five

different operating modes: remote-controlled mode, waypoint mode, autonomous mode, swarm

mode and emergency mode. Each operating mode has different level of autonomy. A last

important observation states that the autonomous and swarm modes are more difficult to

implement, thus, maybe the current technology still need few years to present significant results.



Further studies must be encouraged in the unmanned field, especially because of the huge

potential to boost maritime sector known for being pragmatic and conservative about changes.

At last, it is important to mind that fact of not much literature available obligated the author

start from the scratch; and further and more detailed study is necessary to unfold new

improvements for unmanned ship operations.



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