Geotechnical study in Tafalla

In Tafalla, the dominant geological substrate is mainly composed of sandstones, conglomerates and flysch—materials that provide adequate bearing capacity and predictable behaviour in shallow and near-shallow foundations. Occasional outcrops of limestones, dolomites and marbles are also observed, which may indicate the presence, in specific locations, of more competent ground. The minority occurrence of gypsum, anhydrite and salts requires assessing the local risk of dissolution in projects sited on these lithologies. The generally high soil permeability, due to the extensive presence of aquifers, promotes drainage but means the possible interaction between foundations and the groundwater table must be considered.

Seismic activity in Tafalla is significant, with 113 recorded events over the last 30 years, although with a moderate maximum magnitude (Mmax 2.4), which implies periodic monitoring but without needing exceptional seismic-resistant structural measures. The absence of expansive clays rules out risks associated with ground expansivity. As a specific constraint, it is essential to check for karstification in calcareous or dolomitic areas before constructing, given the associated risk of voids and subsidence. Verification of karst becomes the main aspect to analyse in the geotechnical study in this municipality.