Wednesday, December 7, 2011

Rutting in the Pavement

I bet you can't.  I had to ask, so I'm pretty certain you won't be able to guess.  But just in case you haven't been hanging out talking dirty with the pavement guys behind the buildings in the Advanced Pavement Technology Center at UC Davis, I'm going to give you the opportunity to submit your answer.


I first saw this square-eyed, three-lipped head with tiny ears and a very long tail two years ago.  My husband's work is in pavement testing and design.  Yearly he takes his testing equipment to be calibrated (just like the scales in the grocery store have to be checked regularly and certified that they are accurate).  Today I'm with him again at the calibration center in Davis, California, and am just generally tickled pink to pay a visit to this faded orange HVS as one of the Things I get to do today.

Here's the question:  What is this monster piece of equipment and what is it used for?

This big beasty and its brother on the far distant right were designed and built in South Africa by Dynatest, a Danish Company.  They were shipped here about four years ago.  HVS (here's your answer) stands for Heavy Vehicle Simulator.  Their purpose:  to simulate wear on pavement from heavy vehicles and to break the road as quickly as possible.

Pressure wheel on underbelly of HVS

This wheel exerts 15 tons of load on the pavement and travels back and forth over the road section about 600 times an hour.  Highways with heavy truck and bus traffic get the same treatment but over an extended period of time.  And sure enough, the roads break.


What really made my curiosity itch was the presence of a new and shining HVS that had a much friendlier profile--closer to Thomas The Tank Engine instead of something out of Star Wars.

Rutting from heavy load--just like your highway

As I stood snapping pictures, suddenly there was a rumble, and the monster wheel began moving back and forth under the belly of Thomas.  It put so much pressure on the pavement that one could actually see the road move up and down as the wheel made repeated passes.  The equipment operator told me it was true.  So one of the other Things I get to do today is share this fascinating testing process with you.  Next time you hit a bit of rough road, know that pavement can actually last a long time because somebody somewhere is making ruts in the pavement with "Thomas" and his brothers from South Africa.

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