Thursday 12 May 2011

Destroying LOFAR — Load #9

Our vendetta against this LOFAR HBA tile continues. Will the polar caps disappear before we find enough snow to crush this thing? Here the digger drives up with another tonne of snow.

The snow goes on and there is no collapse. The total mass on the tile now exceeds seven-and-a-half tonnes.
Load   Mass    Total
#1 400kg 400kg
#2 550kg 950kg
#3 950kg 1900kg
#4 1050kg 2950kg
#5 850kg 3800kg
#6 1400kg 5200kg
#7 500kg 5700kg
#8 1050kg 6750kg
-100kg 6650kg
#9 1000kg 7650kg

But wait! Just after the load goes on, there is an ominous 'CRACK'. It was not clear if that was part of the HBA failing, or whether it was the settling of the packed snow. We switch off the digger to wait and listen.

After all the noise of the great machine, there is deathly silence. This part of the world can be so still and tranquil. And yet there is a palpable tension in the air.

Like every load, we check the tile from different angles and take photographs. But now there is a hint that something might have happened.

However, despite the sound the tile looks intact. There is no partial collapse of the wall and the mound looks intact, as if there was no deformation. But then we notice the underside of the tile.

Around the location of Cell 10 and 11 (an HBA tile comprises 16 cells), there is slight bulge that was not there after the application of Load #8. The displacement seems to only be about 5cm, but this is the first deformation that we have seen since the testing started.

The catastrophic failure hadn't happened. But at least were were now seeing some form of distortion due to the loading. It was also noted that the distortion was occurring in a single place, which was more-or-less directly under the location where the digger was placing the snow. As a consequence, this was also the area where the snow had been piling up the highest so it was no surprise that the flexing was only being seen there.

But then what happened next took us all by surprise.

Tune in tomorrow for the report!

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