Geotechnical study in Listen

In the municipality of Oia, formations of sandstones, conglomerates and flysch materials predominate, complemented by less frequent outcrops of slates and schists. These soils, characterised mainly by detrital and metamorphic materials, generally offer good bearing capacity for shallow foundations, with low deformability and scant presence of soft soils. The low proportion of fine sands, silts, and hard clayey or marly materials limits the occurrence of differential settlements, while also facilitating the design of supports in stable areas. However, the identified groundwater bodies and the low permeability of the strata suggest the possible presence of shallow aquifers, which must be taken into account in relation to drainage and moisture control during the construction phases.

Seismic activity in Oia is very low, with hardly any recognised event in the last 30 years and a maximum recorded magnitude of 2.3, which allows seismicity to be ruled out as a relevant factor in the municipality’s structural planning. No risk of karstification or significant presence of soluble materials such as gypsum or salts has been identified. Likewise, the absence of relevant expansive clays, confirmed by the substrate composition, rules out the possibility of volumetric expansion phenomena. As the main constraint, low permeability and the presence of shallow aquifers will be the key aspects to monitor during the foundation phase, particularly to prevent problems associated with water accumulation or unexpected drops in the water table.