Geotechnical study in Llagostera

In Llagostera, the soils formed by granite, gneiss and other igneous rocks predominate, accompanied by gravel and compact sands in smaller proportions, as well as occasional slates and schists. These materials are generally hard and have low fracturing, providing excellent bearing capacity and allowing conventional shallow foundations to be designed, except in specific areas that are altered or where less competent residual soils are present. The low permeability of these formations limits the circulation of groundwater, although local aquifers may exist in more superficial levels, which is relevant for the management of drainage in building projects.

The seismicity observed in the municipality of Llagostera is moderate: 42 events have been recorded over the last 30 years, with a maximum magnitude of 3.1, a value that does not impose demanding constraints for structural design. The non-clayey bedrock in the area rules out any risk related to soil expansiveness, thereby simplifying the selection and implementation of foundation systems. Consequently, geotechnical monitoring should focus essentially on identifying specific areas of superficial alteration; the rock type and its degree of weathering are the main factors to take into account in the local geotechnical study.