Geotechnical study in Sands of San Juan

In Arenas de San Juan, the dominant subsoil widely comprises limestones, dolomites and marbles, which are distinguished by their high bearing capacity and stability for the design of shallow or deep foundations. Occasionally, levels of gravels and compact sands may be encountered, which also favour foundation design; however, the occasional presence of silts and peats of deltaic origin is significant, since, due to their low strength and high settlements, they must be completely ruled out as a support layer. Although infrequent, gypsum, anhydrites and salts introduce a risk of dissolution and chemical alteration; for this reason, their specific location is a priority in the geotechnical study.

The area records high seismicity, with around 200 events over 30 years and a maximum magnitude (Mmax) of 5.1, which requires that the structural design incorporates the current seismic code in order to guarantee safety. In addition, the predominantly limestone nature of the ground implies that specific studies of karst-related phenomena must be carried out before executing any type of foundation, due to the possibility of hidden cavities. The non-clayey subsoil implies an absence of expansivity risk, but the essential condition is the detection and characterisation of karstification and the accurate assessment of the seismic risk for a safe and durable project.