You might be familiar with barrier transfer machines, also known as zipper machines. San Francisco has recently installed a 1.7-mile long, $30 million flexible barrier on the Golden Gate Bridge to reduce head-on collisions, and one of these machines moves it around from lane to lane every day in just a few minutes, a bit like a giant coat’s zip fastener. Here’s what it looks like:
These machines save vast quantities of time and money. Imagine how long it would take to move a heavy barrier like that by any other means. But these barrier transfer machines only use a two-dimensional “zipper.” What if we could do something similar, but with a three-dimensional structure?
This is what a company called Lock Block has been doing with its Arch-Lock concept. Thanks to a different kind of zipper truck, they’re able to build tunnels made from special interlocking concrete blocks that don’t require mortar, and it takes 90 percent less time than traditional methods. This means that the tunnel costs a fraction of the price, and because there’s no steel in the structure, it’s not impacted by rust and can last indefinitely.
This is the Roman aqueduct in Segovia, Spain. It's made of 25,000 granite block without mortar. (Photo: Zarateman/Wikipedia)
Structurally, the design of the tunnel's arch is similar to Roman arches, which have been around for 2,000-3,000 years, so it truly is a time-tested way to do things. If you don't trust that mortar-less arches are solid, just look at this:
This tunnel is held together by gravity; there's no mortar anywhere. (Photo: Lock Block LTD)
And if you're as fascinated by this machinery as I am, the company has released longer videos that show the zipper truck in action. The first video shows the first time they used it: