Geotechnical study in Bilbao

In Bilbao, formations of limestones, dolomites and marbles predominate, accounting for almost half of the ground and providing excellent bearing capacity for foundations, although locally they may present discontinuities and some complexity in the geotechnical study. This is complemented by a significant presence of sandstones, conglomerates and flysch, as well as occasional deposits of fine sands and silts, which may require specific attention in the design of shallow or deep foundations depending on their distribution. The low presence of urban anthropogenic fill materials and bodies of water implies a limited risk associated with differential settlements, provided that the thicknesses and continuity of the deposits are adequately characterised.

Seismicity in Bilbao is notable, with 94 events over 30 years, although the maximum recorded magnitude, Mmax 3.7, does not represent a critical structural constraint; however, it does suggest that a specific check is advisable in accordance with the current regulations. The absence of karstification rules out risks associated with cavities or dissolution, and, since no clayey substrate is found, the possibility of ground expansiveness is eliminated. The main constraint of the geotechnical study in Bilbao will therefore be the correct lithological and structural characterisation of the rock substrate, which will enable a safe and efficient foundation design.