Dolosse: The Unpatented South African Invention Protecting Global Coasts
Dolosse – a South African invention used over the world
I explore the story of the dolosse, a massive concrete structure invented in South Africa to protect coastlines from erosion. These unique, interlocking blocks, weighing up to 80 tons, allow water to flow through them, dissipating wave energy far more effectively than standard concrete blocks. Despite their global use in harbors and breakwaters, the original inventors received no payment or recognition because they were employees of the South African Railway & Harbour Services and never filed a patent.
The dolos is a South African invention for which the inventors received no payment or recognition.
- nusq
Finnally something I have knowledge of. Dolosse were invent in South Africa many years ago, but they are only one type of concrete block for wave dissipation and protection. Many others exist and some of them are patented and require the payment of royalties to be used. Anyway, in Portugal we do not use dolosse ever. We used it once in Sines deepwater breakwater, which suffered a catastrophic collapse in 1979. The promise of dolosse is that the blocks work together because of their shape and thus the individual block can be lighter and cheaper. This does not work in practice, at least in high energy seas. The ocean is unforgiven. What happens is that if only a few blocks break the whole structure will quickly collapse during a storm. And things can break due to a series of problems and risks. Concrete is only good at resist compression stresses and reinforcement with rebar is almost always a bad idea in ocean conditions, so complex shapes are hard to make and to move without introducing unwanted stresses that reduce the design strength conditions. Other types of blocks rely mostly on their design weight and density, and the shape is just used for increasing energy dissipation and overtopping. For example, tetrapods can be moved with only compression forces on the block.
- mk_stjames
Interestingly the author shows a photo of a spot in Cape Town where there are two distinct structures in use - close up, in the photo, are actually Tetrapods - as pointed out in other comments, these are an earlier invention from France and also used quite extensively throughout many parts of the world (including... right here where the Dolosse were invented).
Further down that jetty are structures with the actual Dolos geometry. It would be interesting to know if, specifically, those geometries were chosen specifically to be placed in those two parts of the wall as they are for specific properties, or if came down to having certain quantities made on hand and their distributions matched the shape of the wall required, or what.
You can see what I mean, this distinction in the exact location where that photo is taken on google maps, here:
https://maps.app.goo.gl/Vn3tGhM81oMqPVpm9
-33.899126, 18.412751
Mouille Point, Cape Town, 8005, South Africa
- duggan
Interesting. Been to South Africa a bunch but never clocked that they were different from the more common antecedent, the tetrapod[1].
- walski
In Germany (on the island Sylt) they recently removed all of these structures again after decades of them being a staple on Sylt's beaches. They were found to have no positive effect on protecting their shores.
I'm having a hard time to find a good source to quote but look for: "sylt tetrapoden" if you want to dive deeper.
- liotier
Save yourself the blogspam, go directly to https://en.wikipedia.org/wiki/Wave-dissipating_concrete_bloc... and enjoy the whole collection !