Geotechnical study in Congosto

In Congosto, the geotechnical substrate is formed mostly by sandstones, conglomerates and flysch, representing more than two thirds of the local soils. These materials generally exhibit favourable bearing capacity and allow conventional foundation solutions, such as strip footings or rafts. The occasional presence of slates, schists and hard clays can be found, while the levels of compact gravel and sand—although less frequent—can also provide suitable founding conditions. The occurrence of masses of water or fine sands and silts is scarce, minimising the risks associated with soft or saturated soils.

From a seismic standpoint, the locality shows a very low level of activity, with only two events over thirty years and a low maximum magnitude, which has hardly any influence on structural design. The expansivity analysis confirms that the non-clayey substrate rules out swelling risks. Thus, the main geotechnical constraint in Congosto will be the precise characterisation of the dominant materials and the identification of areas with soft or saturated soils, to ensure a safe and efficient foundation design.