Geotechnical study in Iruña Oka/Iruña de Oca

In Iruña Oka/Iruña de Oca, the predominant subsoil is formed by limestones, dolomites and marbles—carbonate materials that represent 66.8% of the ground and provide good bearing capacity for shallow foundations on sound rock. The smaller deposits of fine sands and silts, although less frequent, require specific assessment due to their less competent behaviour. The minor presence of water masses must be taken into account in order to avoid saturated zones that could reduce bearing capacity. In general, the impermeability of these materials limits the circulation of groundwater, but shallow aquifers may develop locally; identifying these is key in the geotechnical study phase to adapt the foundation solution.

Seismic activity in the municipality is very low, with only 5 events over 30 years and a maximum magnitude below 4.4, so it does not constitute a relevant constraint for structural design. However, the karst nature of the limestones and dolomites makes it necessary to check for the absence of cavities or dissolutions in the ground before carrying out any foundation, as these could seriously affect the stability and safety of the building. Since the subsoil is non-clayey, risks of expansivity are ruled out. The main geotechnical constraint in the area is the possible presence of karst phenomena associated with carbonate materials.