Geotechnical soil investigation, in relation to issues such as foundations, slope stability, retaining structures, and similar, is now being applied more and more attributable both to the increasing requirements for geological safety of structures and to the need to optimize, from a technical and economic standpoint, the sizing of building structures, as well as to comply with current regulations, which require prior knowledge of the technical characteristics of foundation soils. Among the various methods used for carrying out geognostic surveys, the penetrometric test allows for the acquisition of technically reliable information while keeping time and costs contained.
The most commonly used methods are:
- Static penetrometric tests CPT, CPTu, and S-CPTu
- Continuous dynamic penetrometric tests DP
The selection among the different types of tests is made based on the nature and characteristics of the soil to be investigated, as well as the type of structure to be designed.
The CPT test provides highly reliable data in most soil types and, for this reason, is generally considered the most valid in terms of achievable results, particularly in the CPTu and S-CPTu variants. However, it presents difficulties when passing through particularly coarse layers, such as gravels and dense sands, leading to a higher risk of equipment breakage. On the other hand, the dynamic DP test does not allow for easily interpretable data in cohesive soils such as silts, clays, and peats.
As a result, whenever it is necessary to carry out an investigation, the issue arises of choosing which penetrometer to use on site, with the risk of not reaching the required depth or obtaining data of limited reliability. The idea of combining the two types of penetrometers has found application in solutions that favor modularity, integration, wide versatility, and ease of transport.