Personal – Discover Dredging

Personal Announcement: Going Back To School To Cut Some Clay

Learning early or later in life, studying is always a joy when you make it practical

‘Never too old to learn’ is my motto. Everyday I look around me and I wonder how this beautiful world fits together. Whether it be the stars in the sky, the waves at sea or life as we know it, there is always something to be learned about it. At school, I was not a great pupil, but I was always curious to learn more. For my master thesis at the Delft University of Technology, I investigated the performance of a dredge and made recommendations to improve its operation1. As the project was more focussed on mixture forming (and turbidity) and the redesign of the auger head, there was no attention for the soil mechanics involved in the cutting process.

Fully covered cutter head in sticky clay

Now is the time to get that straight. In my daily business, I came across several projects where the clay cutting was a real problem. This was one of the triggers that sparked my interest in sticky clay and made me pursue a more detailed investigation into this nasty stuff. I am very grateful my management was willing to grant me time to go back to the university and start a PhD project with professor Cees van Rhee to learn more about clay.

Synthesis of clay and the relevant properties for dredging

Clay is a completely different material than sand or rock. Those are either plastic and non-cohesive or elastic and cohesive. Clay is the worst of both worlds: plastic and cohesive. It can be described with certain soil parameters as e.g. undrained shear strength and internal friction angle. The failure model is based on Mohr’s circle etc. But those are all continuum approaches2. When you zoom in to the particle level of clay, a whole new world opens up. I already wrote about the interesting particle interaction in a previous post3.

Boltzmann strain rate function in clay cutting

It appears, that the consistency, deformation and failure of clay is related to the tiny electric charges distributed over the platelet crystals. The movement along the charges needs energy. The model to describe dislocation energies along electric charges has been studied by Ludwig Boltzmann4,5. His model governs a wide range of applications, ranging from cosmology to particle physics. I really plunged into the deep end of science with just simple clay. It already took some time to get my head around the concepts involved. Slowly it dawns on my what possibilities there are to improve our understanding of the cutting of clay and possibly to improve our products eventually.

Gallery of my dredging professors (l) prof. de Koning, (m) prof. Vlasblom, (r) prof. van Rhee

My ‘old professor’ de Koning was a proponent of ‘thinking with your hands’6. Professor Vlasbom encouraged me to graduate on a practical problem and also my current professor van Rhee suggested to do some preliminary experiments with sticky stuff to get some feeling about what I am going to study. Of course I took some clay home to play with it. But the best suggestion was by my colleagues, who thoughtfully gave me stroopwafels7. The ultimate representation of sticky non-Newtonian stuff between layers of latticed disks.

Fresh supply of stroopwafels for practice and celebration

References

2021: Muddling Along To A Healthy Year In Dredging

Calendar picture of a sunny dredging site

Dear readers, I sincerely wish you all the best for this new year. As things are looking positive on the vaccine front, we should keep testing negative this year. There are lots of items and events to look forward. Last year was not quite what we’ve hoped for and wished each other.

I do hope all of you are OK and are still together with your loved ones. I am fortunately in that respect. So, next to the Covid situation, there were a lot of other noteworthy items. Most of them have been featured here on Discover Dredging. My trip to Bangladesh, just before all the lockdown measures. The graduation of Carsten1 and Omar2 that were completely over Teams. Some attention to our Damen Dredging Experience3. And some other items. Did you enjoy the Donald Duck review?4

Opening scene of ‘Muddy Fine Business’ or ‘Success Test’ (Credit: Disney)

One sad event was, the last issue of Dredging and Port Construction5. We’ve had to say goodbye to our trusted DPC. Although by now, there has been a kind of digital revival on the CEDA Website6. They opened up a section for Industry News, edited by Namrata Nadkarni. It stands out from the other online media covering dredging as there has been some attention to smaller topics, that would normally not get covered. As I think it is a good initiative, I urge you to subscribe and also participate by sending them any noteworthy news items for publication. Not specifically the usual company press releases, but also the more thought provocative opinions and perspectives on the activities of our dredging community. Active participation could make this CEDA Industry News flourish this year.

Announcement of the CEDA Industry News section (Credit:CEDA)

Further personal activities within CEDA are the Dredging Management Commission7 and I am looking forward to the exciting new concept for the CEDA Dredging Days8. Will you participate? Also, I already took the course on ‘Dredging for Sustainable Infrastructure’9, but you should keep an eye out on the next instalment, coming soon10.

A continuation from last year on my Discover Dredging will be some more articles on our Damen Dredging Experience. There are still some exhibit left to review and teaser:… There are some new exhibits arriving! Hope to have that covered when the pandemic will fizzle out we can show you around through our museum. And I hope to continue on pump and dredge technology.

Overview of the Damen Dredging Experience

Currently, there are some students working on their graduation thesis. Their very interesting topics will be highlighted here as well. Some others will start soon. When you are looking for a fun place to have your internship our your graduation, you might consider a visit to our career page11 or contacting Frank Bosman for any opportunities. Although most positions are filled at the moment, later this year we would welcome fresh brains again.

As our offices will be closed for regular work, I will be working from home most of the time. Probably most of you will do likewise. To keep track of the passage of time over the days, you should have a calendar. As a special service to my audience, I was granted the use of a set of beautiful pictures to create a calendar. You can download the file here and with some DIY skills you should have some original wall decoration for this year.

Stay healthy and stay safe. Hope to see you later this year.

References

How A Ship On The Shore Became a Beacon For My Dredging Career

Stranded Yo, us and another vessel to the rescue (Credit: Co Winkelman)

Long ago, we were sailing with my parents and my brother into the Venezuelan archipelago of ‘Los Roques’.1 After clearing customs, we learned that there was another sailing vessel in trouble. It was stranded on the reefs at the east side of the islands. As we had some spare time we decided to lend a hand in getting them afloat. By eyeball navigation through the channel behind the coral reef, we found the stranded English catamaran ‘Yo’, but had to anchor 200m away. First we learned from a Swiss captain on another assisting yacht they had been pulling together with a maxi yacht on a long hawser to pull them off by power and sail. Alas, to no avail.

Location and map of the islands of Los Roques

The next day, the swiss captain had to leave and we undertook the journey by dinghy to visit the crew on ‘Yo’. It turned out to be a couple with their son and two deckhands. They told us that the maxi yacht was ‘Drum’2 and one of the crew was no other than rock star Simon Le Bon3 himself. We just missed them by a day! He did all the best to cheer them up and you can image what a support that visit meant to these people in such a desperate situation.

As my dad was a chief engineer from the merchant marine, he surveyed the damage professionally. ‘Yo’ was sitting exactly on top of the reef. One keel was broken of and the other only half, but was sheared below the wreck and stuck between the coral heads, preventing any movement. After evaluating the state of the boat, the equipment and the location, he actually said: ‘We’re gonna science the shit out of this.’4 Together we devised a cunning plan:

Lift/Float: Remove the rest of the keel. Plug the holes left by the bolts and increase buoyancy of the craft.
Dredge: Lower the rock bottom to increase support from the buoyancy and create a channel to freedom.
Move: Assemble all winches and tackle to leverage the pulling forces. The forces would be so high that we feared we would pull the catamaran in half. So we had to distribute the forces all around the hull.

The structural repairs on the hull were performed by my father. My brother and me were in charge of the winches and tackle. Any spare time was dedicated to cutting the rock below the wreck. For sure, that is a nasty job, we tore our clothes and cut ourselves on the sharp edges of the coral. By practice, I learned the different angles to aim the pickaxe for the best results and the lowest effort: an introduction into Specific Cutting Energy!5 Because we did our calculations careful and our assumptions were right, the boat moved exactly the moment we predicted and in the way we wanted. It was a great moment of revelation: you could actually use all this knowledge from physics classes6 to get you out of a nasty position. It set me on a path where I am now and you are reading this story.

The best home schooling: toolbox meeting for a salvage operation. (Credit: Co Winkelman)

Actually, we did not see them completely get off, as we had other obligations and had to leave. We were confident they would come off, but it was a mystery to us where they did end up. Finally after thirty years, I did a Google search and to my surprise I found they did get off indeed and were even reunited with their first rescuer, Simon Le Bon.7

‘Yo’ is away, but still scars are left behind in the coral where it all happened. (Credit: Google)

That was my own story on dredging and salvage. Currently, there is an interesting exhibition at the National Dredging Museum8 with better documented cases and very interesting displays. Still, the three steps used for ‘Yo’: ‘Lift, Dredge and Move’ can be distinguished for the other cases there, also.

Exhibit of the salvage operation of the ‘Faustus’ from the Rotterdam breakwater

Remarks

Please keep in mind, that these events happened more than thirty years ago and were about saving the lives of five people in immediate danger. Dredging in coral should only be done under very strict conditions with the health of the ecosystem in the first place and in balance with the necessity of the operation.

Category: Personal

Personal Announcement: Going Back To School To Cut Some Clay

References

See also

2021: Muddling Along To A Healthy Year In Dredging

References

See also

How A Ship On The Shore Became a Beacon For My Dredging Career

Remarks

References

See also