Blasting and subsequent landslide at Steinvik, Tana, Norway

Abstract This work documents the construction of a road project in Tana, Norway, where a landslide occurred following nearby rock blasting. The project aimed to upgrade the existing road network and involved extensive blasting, including at Steinvik, adjacent to a slope with highly sensitive clays. For this section, it was identified during the design stage that uncareful blasting could have detrimental effect on the adjacent slope and even cause a landslide. Despite this knowledge, blasting activity on 18.04.2021, threw a large quantity of rock debris on top of the slope which is thought to have eventually triggered the slope to fail. A key observation is that the slide occurred several hours after the blasting. The slide destroyed 50 m of the road section, and the landslide debris moved around 600 m out into the sea. The applicability of regulatory documents developed to avoid vibration induced slides is re-examined. Learning points from this case study are decisive to understand and deal with similar challenges in the future and to update relevant regulatory documents. This article presents and discusses key aspects of the project including design considerations, risk communications, interpretation of guidelines, measurements and post-slide analysis. It includes analysis of vibrations data, numerical simulations and stability analyses to quantify impact of blasting. Possible reasons and series of unfortunate events that led to the slide, despite attempts to avoid the negative effect of blasting, are explored. This work aims to systematically document this special case to convey key learning points and provide basis for future advanced numerical analyses of the case.