ABSTRACT:

More than 3,000m3 rock slides hit a 6 floor residential building in Aalesund and caused its collapse. Five residents lost their lives, and neighbouring buildings were evacuated. Stability analysis revealed that extra support was needed to cancel the evacuation. The temporary support included rock bolts and concrete piers for underpinning unstable blocks. XRD analysis showed a significant amount of swelling minerals on the failure plane. Results from Odometers test corresponded to a friction angle between 10 and 15 degrees. The final support included 25 rock anchors each on 200 tons and removal of about 250m3 of rock from the top of the slope. The three months support work cost NOK 5 million. This rock slide accident in Aalesund has triggered changes in the new "Planning and building law" and the affiliated regulations for constructions in areas with landslide potential.

1 INTRODUCTION

Early morning 26th of March 2008 a rock slide hit a 6 floor apartment building in Aalesund in western Norway. The slide caused an immediate collapse of the first and the second floor of the building. The slide volume was about 3000m3.The remaining floors were displaced about seven meters in front of the slide. There were five fatalities, all residents in first and second floor. The building at Fjelltunvegen 31 was constructed in a rock cut in 2006. The slide occurred in the cut face immediately behind the building. Two neighbouring buildings, both constructed in rock cuts as the accident site, were immediately evacuated. After the event, Aalesund municipality engaged NGI as a consultant in order to evaluate the stability of the neighboring buildings. The aim was to prevent future damages and to lift the evacuation order. In next phase NGI executed calculating and design of permanent support for the affected area.

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