sciencetech-blog

comments

What happens when an unstoppable force meets an immovable object? It is probably a little like driving a 7.5 ton truck into a 25 ton granite boulder.

The US government has funded a series of tests to smash a series of vehicles into giant pieces of rock - all in the name of science.

Researchers at Penn State University conducted the experiments to help them model how pieces of rock are able to withstand collisions.

Scientists smash trucks into giant rocks in the name of Science

They have been developing a method of determining whether naturally occurring boulders can be used as security barriers around government buildings.

By filming the collisions with high speed cameras, they were able to study the impact and see how much the boulder moved.

Perhaps unsurprisingly, the outcome of the collisions depended upon three variables - the size of the boulder, the speed and size of the truck and the soil the boulder was embedded in.

They found that when a medium-sized truck weighing around 7.5 tons and travelling at 30mph crashes into a five ton boulder of American black granite burined four feet deep, the boulder becomes dislodged from the soil and the truck continued travelling over the top of the boulder.

However, when faced with a larger 25 ton boulder of Rockville white granite, buried about seven feet deep, the boulder moved only slightly and stopped the truck.

The team were able to use their model to predict the outcome of the crashes.

However, they found that if the boulder was hit at an angle and it had not been buried enough, it would rotate out of the way and allow the truck to continue.

The researchers now say that their model is ready for use in the field by officials at the Depeartment of State to help them find ways of protecting embassies abroad.

Scientists drove a 7.5 ton truck into a 25 ton white granite boulder (above) with some rather predictable results

The US Department of State funded the work to help protect its embassies abroad, but many like this US Embassy in Tel Aviv, Israel, use man-made barriers and anti-ram technology to protect the buildings

Dr Tong Qiu, a civil engineer at Penn State University who led the study, said: 'We provided a tool for the Department of State to be able to size a boulder for embassy protection.

'It's a quick assessment tool so they can do it very quickly.

'You can design all kinds of systems, but then the system has to be deployable overseas.

'For the Department of State, sometimes they just want to have a quick evaluation. They want to come up with things maybe on the fly, as a first approximation.'

Using a smaller five ton granite boulder, seen above, meant the rock rolled and launched the truck into the air

Their findings are published in the International Journal of Impact Engineering.

They hope they can be used to help officials find anti-ram barriers that can be quickly installed outside public buildings.

While some government buildings adopt expensive artificial barriers specifically designed to stop vehicles in their tracks before they can get close, others have tried to use local rocks.

However, predicting how these will respond to an impact is less predictable, so the Department of State asked the Penn State team to investigate.

The 25 ton boulder moved slightly but not much was left of the truck after the crash as can be seen above

Using the Penn State Larson Institute Crash Safety Research Facility, they installed the two boulders on a track before smashing the vehicles into them.

Alexander Allen Brown, one of the authors of the study who is now at Lafayette College in Pennseylvannia, told Popular Science: 'Watching crash tests is a harrowing experience, just the sound and the vibrations from it as you're standing on the sideline, it's so percussive it shakes you to your core.

'It turns out that in order to have a boulder buried in sand and have it work, it needs to be big. Really really big.'

The 25 ton granite boulder moved only slightly when it was hit by the truck travelling at 30mph in tests (above)