Happy 2019!

Post card picture of a Damen CSD500 at work.

Happy New Year! First of all, I would like to wish you: health, happiness and a year full of dredging action. And there will certainly be some dredging action. We will start this year with closing our ¡VAMOS! project and we will close off with another CEDA Dredging Days1, just as with which this blog started one year ago with a new year’s resolution.

Further topics will include the upcoming WODCON conference in Shanghai2, more CEDA Dredging Management Commission, some interesting book reviews and whatever happens along the way. Maybe I can get back on working on articles that explain interesting phenomena in dredging technology. Or just some funny experiences I had in our beautiful profession. There are so many memorable moments worth sharing for the general benefit.

And George Santayana has warned us to learn from the past: ‘Those who cannot remember the past are condemned to repeat it.’3 I don’t fancy that this site will be a monumental source of reference for posterity. There are much better institutes to store and share dredging knowledge. e.g. the CEDA comes to mind. It’s ‘a forum for all stakeholders involved in the dredging industry’4 and there are many working groups were the current knowledge is shared and stored in publications.

A much better place to look at a condensation of knowledge over a longer time span is the National Dredging Museum5. You might have noticed, that I am very fond of museums. I like to dwell through their expositions, relive the past and see the origins of current technologies. When I am trying to hatch some new sort of gizmo or gadget to perform a very peculiar dredging requirement, I can relate to all those branches of the technology tree, that are out there and see if there is something that can be combined in a new contraption.

Model of a ‘Krabbelaar’ or ‘Scratcher’ at the National Dredging Museum.

Sometimes you can recognize some technology in an exhibit, that was ahead of its time. Take this ‘Krabbelaar’ or ‘Scratcher’. It loosens the top layer of the sediment and expected it to flush out at the outgoing tide. Considering the enormous forces for cutting and internal friction, that have to be delivered by sail power, I doubt the production would make a viable business case. Nowadays, you would employ a dredge plough behind a tug6. Modern propulsion delivers the thrust needed for all requirements. Ploughing, scraping and smoothing has become much easier and modern hydrological simulations will give a better idea about the possible production and where the sediment will end up.

Example of a modern dredge plough, fitted on a Damen Stan Tug 1606.

Possibly our modern dredge plough technology will be surpassed by even better concepts. Maybe, regulations or fuel economy would direct us back again to a sustainable form of dredging management and the old scratcher makes a comeback in a modern form. And then, you know to find the origins in the National Dredging Museum.

I think, it is very important, we cherish our dredging heritage. For ourselves and for our posterity. Just as we support our trade associations, we should support the dredging museum. So, now I come back to my ‘new’ new year’s resolution: I will become patron7 to the National Dredging Museum. It is not much, but if it inspires you to do the same, we can make a difference together.

Collection of dredges.

References

  1. CEDA Dredging Days 2019, CEDA
  2. WODCON XXII, CEDA
  3. George Santayana, Wikipedia
  4. Our mission and strategy, CEDA
  5. National Dredging Museum
  6. Scrabster Harbour takes delivery of Damen Stan Tug 1606, Damen
  7. Sponsoring 2018, National Dredging Museum

See also

Ploughs, Beams and Rakes, IADC

 

 

 

Exhibition ‘Sand On The Move’ At The National Dredging Museum

Flyer for the exhibition ‘Sand on the move’ (Credit: National Dredging Museum).

As we’ve seen in my last post, sand is one of the commodities most in demand1. Here in the Netherlands, there is a whole industry built on the extraction and distribution of sand. One of the most used extraction methods is dredging, something we’re well acquainted with. One of the most used distribution methods is barge transport. And the National Dredging Museum has opened an exhibition on these complementary trades: ‘Sand on the Move’2.
Last Thursday was the opening of this new exhibition of the museum. For the occasion, there were two speakers invited. Kees van der Veeken, director Consortium Grensmaas showed us the current practice of sand mining. Tjeerd Roozendaal, head engineer – program director projects and maintenance of Rijkswaterstaat had the honour to open the exhibition. Afterwards, there was a dinner buffet available for the guests. An excellent opportunity to learn, hear opinions and build on your (dredging) network.

Panoramic view of the ‘Sand on the move’ exhibition.

Our modern infrastructure was only made possible by the application use of sand as foundation of roads and fill material in concrete and tarmac. At the exhibition, there are displays of four big projects about sand mining: ‘Betuweroute’3, ‘Kraaijnbergse Plassen’4, ‘IJsseloog’5 and ‘Grensmaas’6. Each highlighting a certain aspect of sand mining in the Netherlands.
Another part of the exhibition revolves around the distribution of sand. And this posed a chicken and egg problem: in order to build roads, you need roads to transport the sand. So, in the early days, before there were roads, sand was being delivered over water by barge. There was a short period, where numerous small enterprises, mostly family owned, filled the gap of transporting sand by barge, taking the place of delivery trucks. Also my family had a motor vessel for sand transportation, ‘Excelsior’. And my grandfather told me many times of his adventures on board and his relative happy times. As this was hard work for sure.

Motor sand barge ‘Excelsior’ (Credit: Co Winkelman).

Along with old photographs of those sand barges, there are also many models and a video exhibit. Each conveying respect to these men, women and sometimes children, that have been toiling to build the roads and railways that we are now taking for granted in our luxurious times.
Unfortunately, these businesses worked to their own demise. As roads and railways improved, there was less need to transport the sand by barge, but directly hauled to the location where it was needed by road. So, somewhere this typical business dried up. Nowadays, sand is still transported by barges, but they are usually owned by large companies, that own the whole product line from extraction, distribution to application.
There is also a small sand laboratory to experience yourself, how many different aspects of sand are involved in selecting the right sand for the right application. At a small scale and easy to understand steps, this represents how we are evaluating sand in our own laboratory. Next to this laboratory, there are many more kid friendly exhibits in the rest of the museum. I can highly recommend you to plan a visit to the national dredging museum these weekends or during the Christmas holiday.

Mini sand laboratory (Credit: National Dredging museum).

References

  1. The World in a Grain, Amazon
  2. Sand on the Move, National Dredging Museum
  3. Betuweroute, Wikipedia
  4. Kraaijenbergse Plassen, Wikipedia (NL)
  5. IJsseloog, Wikipedia
  6. Grensmaas, Wikipedia (NL)

See also

Don’t rock the boat, don’t tip the boat over

DOP Dredge ‘Roanoke’, Long Island, USA

We were quietly enjoying our dinner on a relaxed evening in our vacation. Suddenly, we were rudely disturbed by rumble and clatter from across the valley. For our eyes developed a rock slide. Just as sudden as it started it was already over. Perplexed, we were too slow to capture the event and put it on social media. Afterwards, I took some pictures of the rubble. As you can see, it was not even a proper rock slide, more the collapse of a retaining wall.

Retaining wall collapse, Sóller, Mallorca, Spain, June 21, 2018

Come to think about it, it was not the first collapse I witnessed. Back in 2006, I was visiting our DOP dredge at Roanoke on Long Island, NY in the USA. I had to do some measurements and general inspection. I was below decks connecting the data recorder to the drive system and had to check something with the dredge master. Just when I climbed on deck, he yelled at me to hold on. Immediately a torrent of water and sand was flung horizontally over the dredge. Some stones cracked a window in the control cabin. Within seconds a tsunami lifted the dredge for about a meter and we kept rocking until the reflecting waves in the pit eventually subsided.

DOP Dredge Roanoke with pit bank in the foreground, before it collapsed. Older bank collapses in the background.

That was one big bank collapse to me. A bank collapse is a known, although undesirable phenomenon in dredging1. It is a result of dredging methods, relying on the development of an active bank to produce a heavy slurry, that is sucked up. However, the sediment does not consist of a uniform block of sand. Usually, the sediment is deposited in different layers, each with their own geo technical properties. These result in varying propagation velocities of the active banks. When a ‘faster’ sand is under a ‘slower’ sand, the upper layer is not supported anymore and collapses. As the bank slumps down, it displaces an enormous volume of water and this often causes a tidal wave of its own. At Roanoke, the effects were aggravated by the fact, that the upper bank ran all the way to above water level.

Progression of an active bank and bank collapse

As this bank collapse can be expected when dredging with active banks and different sand layers, dredging companies are very keen on predicting these nasty consequences. Not only for the safe working condition of the crew, but also to prevent material damage and eventually for a stable and reliable delivered profile. Exactly this is what is being investigated by dr. Askarinejad in the Laboratory of Geo-Engineering at the Technical University Delft2. He has a beautiful rig, where exactly those conditions can be simulated and measured. With a neat trick he tips the whole test facility to form an instable bank. This makes the bank collapse on demand3.

Static liquefaction tank TU Delft (Credit: dr. A. Askarinejad)

Basically, this is exactly what we can demonstrate with the ‘breaching exhibit ‘ in our dredging experience4. Of course you are welcome to come over. For those who are not in the circumstance to visit us, you can also visit the National Dredging Museum as they now have a breaching exhibit of their own5.

Handover of our old breaching exhibit to the National Dredging Museum

References

  1. Breaching Process OE 4626, van Rhee, TU Delft
  2. Amin Askarinejad, TU Delft
  3. Statische liquefactietank , Delft Integraal
  4. Loose sand, how hard can it be?
  5. Baggermuseum krijgt model van Damen Dredging, Binnenvaartkrant

See also