Geotechnical study in Benasque

In Benasque, soils formed by slate and schist predominate, accompanied secondarily by granite, gneiss and some carbonate rocks and dolomites. These rock formations offer a high bearing capacity, which makes them suitable for shallow foundations, particularly when they rest on unaltered material. Hard clays and hard marls appear occasionally and can be considered valid options for founding provided they are well characterised, whereas compact gravels and sands, although less common, can also present good conditions for foundation design. Permeability is generally low, so the problems associated with drainage are limited except where there are localised shallow groundwater levels.

Seismic activity in Benasque is classified as notable, with 121 events recorded over the last 30 years and a maximum magnitude of 3.6. Although this does not reach critical values, it requires careful analysis of local seismic response in the geotechnical study. Given the presence of calcareous and dolomitic ground, it is essential to rule out active karst processes before proceeding with any foundation, as these may affect ground stability. On the other hand, the non-clayey substrate present rules out risks linked to expansivity. The most relevant factor for design will therefore be verifying the existence of karst cavities in the calcareous sectors, together with adequate characterisation for structural calculations under moderate seismic actions.