19 November 2008

Alesund landslide – the verdict

Posted by Dave Petley

Back in April I posted extensively about a landslide that occurred in the town of Alesund in Norway. This slide occurred on 26th March, when a large block slipped into an apartment block, pushing it forward by up to seven metres and collapsing the lower floors. Five people were killed.

This week, the outcome of the commission of inquiry has been released. The key points are as follows:

  • Blasting of the cliff during the construction of the apartment block was responsible for the failure;
  • This blasting, which was intended to create the platform for the building, weakened the hillslope;

It is clear from this image that the failure occurred on a pre-existing joint that favoured instability. It is not clear how this was missed in the original site investigation.

Presumably the blasting removed the toe of the block, destabilising it. If so then this looks to be an error of the site investigation and design. Given that the report has been handed over to Ministry of Justice, I would imagine that those involved in the original work will be somewhat uncomfortable now.