The Hole Problem

Local readers may well be aware of the Big Black Hole in Sydney. For the rest of you, welcome and allow me to explain...

Basically, what happened is that at approx 2am AESST yesterday, there was a rock collapse in the construction of the Lane Cove Tunnel, leading to a 10 metre crater in the ground...with a block of apartments, situated above the construction site, left hanging over the hole. More on the story
here; it's a pretty good overview, although I normally use ABC news for my links. This is a temporary link.

The hole below the apartment block.

Have you ever stood on the top of a high diving platform? And looked all the way down to the water? That's how deep 10 metres is...over 30 feet. It's a big hole.

An aerial view of the apartments, perched above the hole.

All the residents were immediately evacuated, and no one can say when they might be allowed back in; although there have been assurances that the building is not about to collapse, yesterday there was hourly updates on the news of the balcony at the front corner of the building, which you can see in the lower left-hand conrner of the above photo. Hour by hour, we watched it sag further and further, as the surrounding walls cracked, until finally at 18:30 AESST yesterday, it collapsed into the hole.

The balcony gives way.

This morning on the breakfast TV shows, they broadcast slo-mo "action replays" of the balcony collapse, which I though was just dreadful. It wasn't just the balcony that collapsed, but the entire front room; you could see people's personal possessions falling along with the balcony. Sure, it may make for great TV - I've heard commentators remarking on the "amazing footage" and "spectacular scenes" - but these are real people who lived in this building, about 50 of them, who had to suddenly flee their homes in the middle of the night, with no time to collect any possessions, and who face the prospect of losing everything if the building does collapse or require demolition (the latter is looking more likely at this stage).

The scene after the collapse

Engineers are pouring thousands of cubic metres of quick-drying concrete in an effort to fill the hole, but as I've pointed out, that's one big hole. Now I never studied engineering at uni, nor even physics at high school, and I know nothing at all about it. You could tell me that the Opera House is built on a foundation of fencing wire, and I'd believe you. But I've grown up in an area prone to mine subsidence and earthquakes, and I've seen quite alot of buildings under construction. So I'm left to wonder...why aren't the engineers putting up solid metal struts, to secure the walls of the building which are still on solid ground?

This has caused yet more tunnel related problems for the State Government. Not least, because this building is situated on one of Sydney's major arterial roads, leading to traffic chaos - there's no word on when the road will re-open.

Well, I'll continue to update the situation as it comes to hand (or you can follow the news links to see what's happening during the 18 hours a day when I'm not online...)