Conclusion
Mechanical properties of soils determined in situ

Penetration tests and pressuremeter tests are recommended for soil investigation with a view to sizing foundations. To varying degrees, they can be used to quantify the properties of the soil in place and, consequently, either to guide the study at the preliminary design stage, or to determine the final dimensions of the foundations.

As a general rule, they lead to dimensionings that are closer to reality than those deduced from conventional laboratory tests.

On the other hand, they will be inoperative or unreliable for solving certain specific problems requiring, for example, knowledge of the soil's internal angle of friction $\text{ϕ}$ or its compressibility and consolidation characteristics. This is the case for slope stability problems, backfill...