The use of the observational approach in the risk management of an excavation slope on the A1 Motorway near Condeixa, during the operation phase

This chapter examines the use of the observational approach in the stability assessment of a soil excavation slope along the A1 motorway near Coimbra, operated by Brisa Concessão Rodoviária (BCR). The study follows a landslide that occurred during the road construction in 1980. The landslide involved substantial mass movement exceeding over 150 m in length and reaching a depth of approximately 20 m. Any intervention intended to cease the ongoing movements observed post-initial stabilisation measures would incur exorbitant costs. Since these movements remained minimal and progressed at a relatively constant rate, it was considered that the risk was compatible with the use of the observational approach. Stabilisation measures or evacuation of potentially affected individuals would only be implemented if the displacement rate increased. After 40 years, intervention measures have been restricted to short-term, inexpensive actions that primarily focused on improving the slope’s internal drainage.