Working Group ‘Sand’ Visits Damen: Perspectives On Sand From Micro to Macro Scale

Working Group ‘Sand’ visiting the Dredging Experience at Damen Dredging Equipment
Working Group ‘Sand’ visiting the Dredging Experience at Damen Dredging Equipment

You may already know, that I am very interested in this miniscule particle that is the foundation of our business. To learn more about this element, I joint the Working Group ‘Sand’ of the Dutch Association for Geological Activities1. It is a colourful group of enthusiasts that collect, photograph and research sand in all its splendour. During the relaxed Saturday afternoon meetings, the members gradually noticed, I had a slightly different, professional interest in sand. They boldly asked if they could visit our company for their annual excursion. Maybe my presentation, by at least the excellent weather made for a very successful event.

Measuring the grain density of sand
Measuring the grain density of sand

One aspect of the sand grains we wanted to measure was the buoyancy of the particles. This is done by measuring the density of the grains. You have a tube of water with a known volume. You add sand with a known mass. And just as Archimedes2 predicted, the water will rise with the displaced volume of the grains. Dividing the mass by the displaced volume yields the density of the grains. Surprisingly, this method is quite accurate. For a static condition this is perfectly satisfying. However, in most dredging situations, the grains are dynamically jostled around in slurry transport or breaking up sediment at the cutter.

Effective grain density due to adherent fluid
Effective grain density due to adherent fluid

When a solid grain is moving through a fluid, it is usually considered as a perfect sphere. Nothing is perfect in nature and grains do have a range of shapes, that at best are similar to potato’s. A very jagged grain will have lot’s of nooks and crannies filled with the fluid. This fluid is moving with the particle and contributes to the mass and volume of the particle. This adherent fluid is much more reliably assumed to be a sphere. Fluids in a zero gravity situation tends to behave like a sphere. The diameter of the sphere can be taken as the maximum diameter of the grain that can be measured.

Measuring the effective volume of sand grains
Measuring the effective volume of sand grains

Through a microscope, you will only be able to see the lateral area or the cross-section of a grain. Both area and volume have a relation to diameter. So, the measured area is reduced to an equivalent round area with an equivalent diameter and consequently an equivalent volume. The volumes and masses of that equivalent volume of sand and the shell of adherent water will yield an apparent density of the moving particle.

Effect of apparent density on dredge performance
Effect of apparent density on dredge performance

In the end, my objective was to learn through the microscope the effect the shape of the sand had on the performance of our dredges. As seen in a calculation in our production estimating program, the effect can be significant. Certainly an influence we want to know and assist our customer with appropriate advise3. My visits to the meetings of the Working Group ‘Sand’ were a real benefit in understanding sand. But, to my surprise, through the working group I also learned to appreciate the beauty of the all the different sand minerals that can be found.

Picture of various sand grains in an interesting mixed sample
Picture of various sand grains in an interesting mixed sample

References

  1. Werkgroep Zand, Stichting GEA
  2. Archimedes, Wikipedia
  3. In house R&D Department, Damen Dredging Equipment

See also

Digital Microscopes, Dino-Lite

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