Geotechnical site investigation is the first and most decisive phase of any engineering project that interacts with the ground. Its goal is to characterize stratigraphy, mechanical and hydraulic properties, and geological hazards of the subsurface, through a planned combination of indirect exploration (geophysics), direct exploration (boreholes, test pits) and in-situ testing to reduce design uncertainties.
Rotary core drilling allows undisturbed sampling and direct observation of stratigraphic contacts. SPT and CPTu tests, performed during drilling, deliver continuous profiles of resistance and drained/undrained behavior. Exploratory test pits complement surface information, especially for lightweight foundations, pavements or buried utilities.
Geophysical methods —seismic refraction, MASW, electrical resistivity tomography, GPR— cover large areas with low impact and reasonable cost, identifying stiffness contrasts, bedrock depth and anomalies. Their interpretation is calibrated with localized boreholes to reduce uncertainty in the final geological-geotechnical model.
The investigation program must be proportional to project complexity and risks identified during planning. Integration with historical background analysis, regional geomorphology and seismic hazard assessment ensures a robust geotechnical model, the solid basis for all subsequent design, structural calculation and construction decisions.