Geotechnical study in Sestao

In Sestao, formations of limestones, dolomites and marbles predominate. These materials exhibit high structural strength and provide a high bearing capacity for the direct foundation of buildings. In areas where fine sands, silts or urban anthropogenic fill are present, it is essential to check the homogeneity of the subsoil and to rule out the presence of compressible or unstable materials before deciding on the type of foundation. The scarce presence of granitic or igneous soils has little effect on the overall ground conditions.

Given the absence of expansive clayey soils and the predominant impermeability of the materials, the risk of expansivity is ruled out in the area of Sestao. Seismicity, with 94 events over 30 years and a maximum magnitude below 4, does not represent a significant threat, although the existence of moderate seismic activity should be taken into account in the geotechnical analysis. The main geotechnical constraint is the local variability of the subsoil with respect to fill and water-affected areas; accurate characterisation is therefore key for the design of the foundations.