Geotechnical study in Villafranca del Bierzo

In Villafranca del Bierzo, soils formed by slates and schists predominate, accompanied in smaller proportions by sandstones, conglomerates and flysch. These materials, mostly of low permeability, provide good stability conditions and usually offer an adequate bearing capacity for building, although they may show a certain anisotropy in the case of slates. Compact gravels and sands, although infrequent, also provide acceptable values for foundation design. However, it is necessary to avoid using isolated areas of fine sands and silts as a bearing level due to their lower stability.

Seismicity in the municipality is moderate, with 16 recorded events over 30 years and a maximum magnitude of 3, which does not imply any special requirement in structural design. The non-clayey substrate eliminates the problems associated with expansivity. Given the potential presence of karst phenomena, it is essential to check for cavities or dissolutions at depth before deciding on the type and depth of the foundation, since this may be the main geotechnical condition to analyse in the area.