A case of man-induced ground subsidence and building settlement related to karstified gypsum (Oviedo, NW Spain)

This paper presents the research carried out to shed light on a sudden settlement and its consequences that occurred in the city of Oviedo. Ground subsidence in the Ventanielles area led to severe damage and the subsequent demolition of two buildings with 362 flats, resulting in losses of 18 million euros. The investigation allowed the identification of a buried sinkhole, filled with up to 13 m of fluvial sediments, linked to the dissolution of a Paleogene gypsum unit with a maximum thickness of 18 m and containing metre-sized cavities. The triggering process that reactivated the paleosinkhole was found to be the pumping of water from a confined aquifer, related to excavation work during the construction of a nearby underground parking lot; this extraction modified the natural hydrological regime. The compaction and migration of alluvial sand towards the karstic cavities were the main subsidence mechanisms responsible for the structural damage, aggravated by the poor quality of the buildings and the geotechnical behaviour of the supporting ground.