Geotechnical study in Bossòst

In Bossòst, the geotechnical study reveals that the predominant substrate is composed of phyllites and schists, with a secondary presence of limestones, dolomites, marbles and, to a lesser extent, hard clays, compacted gravels and igneous rocks. This lithic context favours a generally high bearing capacity, particularly in the layers formed by consolidated metamorphic and sedimentary rocks. The low inherent permeability limits the incidence of groundwater, although shallow aquifers may exist in localised points. For foundations, it is usually advisable to reach the horizons of sound rock or the most competent stratum available, thereby optimising the structural behaviour of the buildings.

From the seismic point of view, Bossòst is located in an area of very low activity, with an event recorded over 30 years and a low maximum magnitude (Mmax 1.7), such that seismic hazard scarcely affects the criteria for structural design. The absence of a clayey substrate eliminates the risk of ground expansivity. However, the presence of calcareous and dolomitic formations makes it necessary to check for the possible occurrence of karstification before starting any foundation work, since cavities or dissolution processes could undermine the stability of the structure. The main limiting factor in the area is therefore the potential for karst, which must be ruled out through the appropriate geotechnical investigations.