Geotechnical study in Santa Brígida

In Santa Brígida, the predominant soils are of igneous origin, mainly granite and gneiss, which together account for more than 60% of the geological substrate, accompanied by sandstones and conglomerates in a significant proportion. These materials are characterised by a high bearing capacity, which allows for the design of direct shallow or semi-deep foundations with high reliability, provided that the contacts between lithological horizons are properly identified and that altered or weathered zones are not located. The existence of aquifers with moderate permeability and output suggests that there may be groundwater circulation at certain points, which must be verified in order to rule out the risk of internal erosion that could affect the foundation.

With regard to geotechnical risks, the recorded seismicity is very low—only one event in thirty years with a maximum magnitude of 1.5—which implies that this factor has a practically negligible influence on local structural design. No risks associated with karstification or expansive clay soils are identified either, since the dominant lithology is resistant and stable. The main geotechnical constraint is related to the correct characterisation of sound rock and the possible presence of aquifers, as these factors can influence the choice and sizing of the foundation.