In contrast to previous works on geotechnical preliminary investigations, the authors have focused on measurements in their considerations because the development of soil mechanics has largely been a matter of theory, leading to a mathematical effort in specialized studies that often exceeds practical needs, yet has not resulted in reliable outcomes. Today, soil mechanics is at a point where progress is more likely to come from measurements. The existing body of knowledge must be verified against observations from experiments or completed structures, and a selection must be made among the theoretical considerations, the value of which remains uncertain. This necessitates not only conducting measurements but also treating the experimental and measurement results as an active area of study rather than a closed chapter.