Geotechnical study in Carballo

In the municipality of Carballo, strata formed by slate and schist predominate, representing around 69% of the soils, accompanied by a significant presence of granite and gneiss. These lithologies, of hard and compact nature, provide excellent bearing capacity for the foundation of all types of buildings. The occasional occurrence of sandstones and conglomerates may locally modify strength; however, in general, the soils of Carballo are characterised by being poorly deformable and stable, allowing the design of shallow surface foundations in most cases.

The seismicity in Carballo is classified as moderate, with 24 recorded events over 30 years and a maximum magnitude of 3.3, indicating low seismic activity that usually has no significant impact on conventional structural design. Since the substrate is mostly non-clayey, the risk associated with expansivity is ruled out in this setting. The main geotechnical constraint in Carballo will therefore be the competency of the rock materials and their low permeability—factors that favour safe foundation support, provided that the absence of significant alterations or areas with superficial fill is verified.