Geotechnical study in Villava/Atarrabia

In Villava/Atarrabia, the predominant geological substrate is made up of limestones, dolomites and marbles, materials very common in the area and recognised for their high bearing capacity, which in most cases makes it possible to opt for direct shallow foundations. Groundwater levels and secondary layers of fine sands and silts are also identified; their compaction may require specific studies to prevent differential settlement. The presence of surface aquifer formations is occasional due to the generally low permeability of the ground, but their precise location is relevant for defining the optimum foundation support depth.

Seismic activity in Villava/Atarrabia is high, with more than 200 events in 30 years and a maximum recorded magnitude of 5.2; therefore, seismicity must be incorporated without fail into the structural design of buildings. Although the risk of expansivity due to clays in the matrix is mentioned, it is considered low as there are no predominant expansive clays. The main constraint for the geotechnical study in this municipality is represented by the seismic consideration; it is essential to size the foundation in accordance with these regulatory requirements.