Geotechnical study in Polanco

In Polanco, limestone, dolomites and marbles predominate, together with sandstones and flysch, which implies a rock base with high compactness and strength. Fine sands and silts appear to a significant extent, making it necessary to pay attention to their distribution due to their lower bearing capacity. Although there are small proportions of gypsum, anhydrite and salts —with the potential risk of dissolution—, the predominance of a rocky substrate favours direct or shallow foundations, except in localised areas where the compactness is reduced or where there are soft materials such as sands or silts.

Seismicity in Polanco is notable, with 145 events over 30 years, although the maximum magnitude (Mmax 4) remains within a moderate threshold that does not require exceptional structural conditions, but does require seismic actions to be considered in the design. Given the abundance of carbonate formations, it is essential to verify the existence of karst-related phenomena before defining the foundation, since the presence of voids may entail potential instability. The non-clayey substrate rules out expansivity problems, with control of karst, together with lithological heterogeneity, being the main geotechnical constraint to be assessed.