Geotechnics for rockfall assessment in the volcanic island of Gran Canaria (Canary Islands, Spain)

The island of Gran Canaria (Canary Islands, Spain) is characterized by a large variability of volcanic rocks, reflecting its volcanic evolution resulting from the built-up process of an intraplate oceanic island. The geological map provided by Geological Survey of Spain at 1:25.000 scale shows more than 109 different lithologies and it is too complex for environmental and engineering purposes. This work presents a simplified geotechnical map with a small number of classes grouping up units with similar geotechnical behaviours. The original lithologies were grouped using about 350 representative rock samples, collected in the seven major islands of the Archipelago. The samples were characterized by laboratory tests and in situ analysis. The geotechnical map was used to model and evaluate rockfall hazard in the entire island of Gran Canaria, where rockfalls are an important threat with a high social, economic impact. The rockfall map was validated with 128 rockfall events, occurred during the period 2010-2016, along the GC-200 road (34 Km), located in the NW sector of Gran Canaria. About 96% of the events occurred along sections of the road where the number of expected trajectories is high or moderate.