Soil Nail Launcher

I read an interesting article the other day about how World War II technology is being used to stabilize earth around highways in flood-damaged southern Minnesota. A company called Soil Nail Launcher, Inc. uses an air cannon first developed in 1945 to fire nerve gas against Nazi forces. The launcher originally could be used to fire the gas canisters a distance of 7 miles. Now, outfitted to fire 20-foot steel rods into the earth to help stabilize the area, the launcher shoots these rods at speeds of 220mph. Once these rods have been put in place on the grid (of three feet apart, horizontally and vertically), then a concrete-like or mortar substance or natural grass system is used to keep it together.

I don't know why, but I think this is a fascinating use of old technology. At times I think that all the technology from the 40s and 50s is outdated since we've expanded upon it so much, if not out-right replaced it. But then a story like this comes along.

One of the reasons it's being used in southern Minnesota is because to get fed'l relief $$$ for the flooded areas with slope failures, the repairs must be done from already-owned right of ways. This equipment has been performing from the highways themselves, and cuts down on environmental costs (since there's no need to go off-road with heavy machinery for prep work or stabilization). Add to it the fact that they get the job done much more quickly than manual methods, and costs 30-50% less than manual methods, this seems like a pretty ingenious method to re-use technology.

From their website:

The Soil Nail Launcher is a declassified British military cannon that can accelerate a 1.5 inch diameter, 20 foot long steel bar to 220 miles per hour. As these high speed projectiles enter the earth, a shock wave is generated at the tip that causes the soil particles to “jump away”. The bar enters the earth without significant abrasion. The soil particles then collapse onto the bar, providing surprisingly high pullout resistance -- many times greater than for driven bars and rods.

The Soil Nail Launcher is typically mounted on a tracked excavator. It can be mounted on about any vehicle or crane basket frame. It weighs about 2 tons, making it portable and able to reach remote locations.

About any type of bar can be shot into the ground. We can use solid steel, threaded bar or hollow bars that can act as drains and also provide tensile capacity. We can galvanize the bars. We can shoot fiberglass nails. We can pump grout into hollow bars to add capacity and strength. We can
add mesh and plates to a Launched Nail array or spray on a shotcrete facade.

My favorite line from their website is the one about it weighing "2 tons, making it portable..." For some reason, that makes me laugh.

To read more about it and see a pretty cool picture of it hanging over the ocean, check it out here.