Geotechnical study in Boltaña

In Boltaña, the predominant subsoil is made up of sandstones, conglomerates and flysch, which account for the majority of the ground and stand out for their compactness and good bearing capacity. Formations of limestone, dolomites and marble provide favourable characteristics for shallow foundations due to their strength, although in some sectors they may present a certain degree of heterogeneity. The low percentage of clays and hard marls implies a limited occurrence of deformable soils, which makes it easier to select the foundation type, usually of a direct type unless there are specific adverse conditions. The ground’s permeability is low, although the presence of shallow aquifers cannot be ruled out in certain areas.

Seismic activity in Boltaña is very low, with just 4 events in 30 years and a maximum recorded magnitude of 2.8, so it does not represent a conditioning factor for structural design. Since the subsoil is mostly non-clayey, the risk of ground expansivity is ruled out. However, the presence of limestone and dolomites requires a prior check for karst-related phenomena before considering any foundation, as these can create voids or instabilities that are not visible from the surface, making it the main geotechnical conditioning factor in the area.