Geotechnical study in Sant Joan de Labritja

In Sant Joan de Labritja, limestone, dolomites and marbles predominate; these materials provide excellent bearing capacity, while significant areas of compact gravels and sands are also observed, with good conditions for foundations. Sandstones, conglomerates and flysch appear in isolated locations, adding some lithological variability. The minor presence of gypsum, anhydrite and salts indicates that there is a risk of dissolution that must be assessed in foundation projects, although the clay levels present are hard and do not predominate, which facilitates greater stability in construction. The local aquifers, despite their moderate permeability, need to be taken into account in projects involving excavation below the water table.

In terms of natural hazards, seismicity is moderate, with 24 events in the last 30 years and a maximum recorded magnitude of 3.2, which suggests a low level of influence on structural design. The karstic nature of the calcareous substrate is a key constraint to verify before undertaking any foundation, due to the possible presence of underground cavities or localised subsidence. The absence of expansive clays and clayey substrate allows significant expansivity problems to be ruled out. In conclusion, thorough verification of the karst and assessment of the risk of salt dissolution constitute the main geotechnical constraints in Sant Joan de Labritja.