Geotechnical study in Membrilla

Within the municipal term of Membrilla, soils formed by limestones, dolomites and marbles predominate, representing more than 60% of the local lithology, which gives the substrate high strength and an adequate bearing capacity for shallow foundations. Occasionally, gypsum, anhydrite and salts may also be found, as well as compact gravels and sands, which must be characterised individually to rule out the risk of dissolution in the case of gypsum and salts, and to check the compactness in the case of granular materials. Slate and schist are very infrequent and, unless present locally, their influence on bearing capacity is limited.

Seismicity in Membrilla is very low, with a small number of events and a maximum magnitude of moderate level, so this factor does not represent a relevant constraint for structural design. However, as it is an area where karst may occur in carbonate materials, it is essential to investigate the possible presence of cavities, sinkholes or karst conduits before designing and carrying out any foundation works. The non-clayey substrate rules out the risk of expansivity, so the main geotechnical focus should be on the characterisation of the karstified formations and on checking stability against possible dissolution processes, particularly in areas where gypsum, anhydrite or salts outcrop.