Geotechnical study in Vitoria-Gasteiz

In Vitoria-Gasteiz, the predominant subsoil is composed of limestones, dolomites and marbles—materials with high mechanical competence and good characteristics for supporting shallow (direct) foundations, provided that there are no significant fractures or important voids. The secondary presence of fine sands, silts and some sandstone or flysch formations may require localised studies in specific projects. The usual bearing capacity of these materials is typically high, but the possible presence of shallow aquifers within impermeable strata makes it necessary to consider suitable drainage and a detailed analysis of the groundwater table in underground works.

Seismicity in the municipality is considered moderate, with 17 recorded events over 30 years and a maximum magnitude of 3.6; therefore, although seismic risk is not high, it should be taken into account in situations involving distinctive buildings or sensitive infrastructure. It is essential to verify the existence of karstification phenomena, given the dominant calcareous nature and its propensity to develop underground cavities, which can compromise the stability of foundations if not properly identified. The absence of clayey subsoils rules out expansivity risks, with karst being the main geotechnical conditioning factor in the area.