Issue 035 Cover

Submerged Floating Tunnels

By Khaled Abou Alfa • 23rd of September, 2020

Sometime around 250 BC, Archimedes wrote On Floating Bodies, the first known work on the topic of hydrostatics. Hydrostatics is a branch of fluid mechanics concerned with fluids at rest and the pressures exerted on an immersed body. On Floating Bodies contains the concept, which later became a principle:

Any body wholly or partially immersed in a fluid experiences an upward force (buoyancy) equal to the weight of the fluid displaced

It was then a reasonable skip and hop, across the centuries, of employing this principle in our relationship with the sea. Archimedes’ principle explains why massive ships are able to float or why submarines don’t sink to the bottom of the ocean. When the weight of a volume can be distributing such that it remain less than the water that is displaces, it will float.

In the built world, this principle is employed from off shore wind farms (issue 027) to pontoon bridges. It is also the basis behind concepts required to enable floating cities (a topic we will cover in a future issue). Unknown to Archimedes, or anyone for that matter, was that this principle would also set in motion a race that continues to this day. The race to building the world’s very first submerged floating tunnel (SFT).

Approach & Technology

The use of an SFT can be justified across multiple reasons. The terrain itself between two points may prohibit the use of a bridge or tunnel due to the extremes, such as fjords that run deep. Limiting environmental impact that is caused by the both the construction and existence of a bridge. Or the use of a bridge would need to be built such that it avoids the disruption of established sea routes. Another advantage of an SFT is how it remains oblivious to the weather. Being at a certain distance below the surface of the water means that it will also be protected against the conditions raging above it.

Anyone who has crossed any mega structure that bridges harsh elements can only marvel at the sheer audacity that humanity displays in taming the natural world to our will. An SFT offers a different proposition entirely. While the audacity remains in copious amounts, the final element is an understated piece of engineering. It remains hidden.

Conceptually an SFT is a number of concrete tubes suspended under the surface of the water. If the overall system has positive buoyancy, then it is tethered to the floor bed below. If it has negative buoyancy, then this is kept afloat with the use of pontoons above. An SFT does not have the same limitations that a bridge might have. In theory, an SFT can snake for as long as is necessary.

Although the concept is over 2200 years old, and even though much of the necessary technology is tried and tested, we have never even attempted this type of structure. In fact this concept hasn’t even been tested as a proof of concept, across short distances.

Maybe then the problem is an issue of perception. Let the concept settle in your mind. Connect massive concrete tubes. Fill these with moving trains, buses and cars. Suspend everything under the surface of the water. Its madness to anyone but a civil engineer. Still, if built, an SFT would be one of the most exciting and also understated marvels of engineering.

And so the race continues…


Submerged Data Centres

Submerged Data Centres

Keeping on theme for this issue, the last time we checked on project Nautilus (Microsoft’s submerged data centre technology), it was churning away somewhere of the coast of Scotland. 2 years later the data centre has emerged from the depths. The experiment, which started out as an employee idea from Microsoft’s ThinkWeek event in 2014, has washed its face by demonstrating itself capable in a number of unexpected areas. While there are many lessons yet to gleaned, the key takes are:

  1. The server failure rate was 1/8 compared with land based equivalent.
  2. The data centre was powered exclusively from renewable grid sources, considered less reliable, yet experienced no loss of power.

These data centres could one day be bundled up with offshore wind farms and deployed across the world.

Battery Day

As discussed back in issue 015, advancements in energy storage technology are capable of transforming the world around us. From our transportation needs, to the energy we use in our homes and everything in between. While Elon Musk is thoroughly in the acts strange department, his company Tesla are a company that continue to push the boundaries of what is achievable with batteries. Last night they held their annual Battery Week event. Meanwhile another favorite of the newsletter, BP released their energy outlook with their prediction and reasons for why we are close to hitting peak oil (for real this time).

These announcements won’t change the world overnight but they are canaries in the coal mine - a signal of things to come. Lower batteries means more affordable electric vehicles; means a further shift away from fossil fuels; means we are capable of changing our world in incremental and meaningful steps.

Publications of Note


Berlin Berlin took writer/artist Jason Lutes over 20 years to create. Rarely does a work of art convey so much within it’s pages. In Lutes’ deft hands the city of Berlin, starting in the 1920, comes alive with facts and nuanced details peppered throughout the story. All presented in glorious black and white. An exceptional achievement, well deserving of your attention.

Two years ago the series got a hardcover collected edition. A paperback edition was released this month. It remains one of the essential works you need on your shelf.

Tools of the Trade

Minimal Watches

Apple recently had their bi-yearly infomercial of their upcoming product lineup. With their executives strutting the preverbal digital catwalk its easy to get caught in the excitement of the shiny and new. While there is much to love, when it comes to watches the analogue tools remain superior in a few key ways. They never turn obsolete, have no software to worry about and no battery to recharge every other day.

Minimal Watches 01

While there is seemingly an infinite number of styles across hundreds of brands, I have been tending towards minimal designs with quality mechanisms. Swatch’s Skinera, Mondaine’s Helvetica, Certina DS-8 or Junghan’s Max Bill offer a minimal aesthetic across price points.

The Stet newsletter explores the ideas, projects and technologies that define our built environment.