Geotechnical study in Tortosa

In Tortosa, the predominant geotechnical subsoil is made up of fine sands and silts, occasionally accompanied by calcareous formations, dolomites, marbles, as well as gravel and compacted sands. This composition implies variable geomechanical behaviour: while fine sands and silts exhibit moderate bearing capacity and require particular attention to settlement control, episodes of carbonate materials can increase ground strength, offering more favourable options for foundations. It is essential to accurately identify the location of muds or masses of water, as these represent points where it is not advisable to support isolated footings or slabs.

The seismicity of Tortosa, with 23 events in the last 30 years and a moderate maximum magnitude (Mmax 2.6), is considered to be of intermediate level, so it is worth paying attention to, but without extreme constraints in structural design. The risk posed by karstified ground due to the presence of limestones and dolomites makes it necessary to verify any underground cavities before carrying out any foundation works, in order to avoid unexpected subsidence. Likewise, detecting gypsum and salts in the subsurface introduces the possibility of dissolution-related phenomena that must be analysed during the geotechnical study phase. As no expansive clay soils are identified, the risk associated with expansivity is ruled out, leaving the need to control the existence of karstified zones and associated dissolutions as the main constraint.