Recent developments in equipment and interpretation of cone penetration test for soil characterization

Over the last decades cone penetration testing has become the most widely used in-situ testing technique for stratigraphic profiling and site characterization. As a consequence of such extensive use, which has also rapidly spread to many new areas of application, a considerable amount of research has been carried out in terms of equipment, testing procedures, analysis of the penetration mechanisms and methods for data interpretation. This paper aims at providing a general picture of the major trends in CPT research carried out over the recent years, by presenting the most significant emerging innovations in instrumentation and the latest advances in the analysis of tests on sediments other than “standard” clays and sands and thus referred to as “non-standard” or “unusual” geomaterials. Attention is especially focused on intermediate sediments, such as silts, sandy silts, clayey sands and other sedimentary soils having very scattered grain size distributions and therefore potentially affected by partial drainage effects during cone penetration tests. The body of knowledge on such effects, as accumulated worldwide from both laboratory and field research, is reviewed and discussed, with special emphasis on the experimental results obtained from variable rate piezocone tests carried out in a few intermediate soil deposits in northern Italy. It is shown that the efforts of many researchers have mainly focused on the identification of cone penetration velocities required to ensure fully drained or fully undrained testing conditions, with reference to different soil classes or macrofabrics. Indeed, the preliminary identification of drainage conditions is a key step in order to avoid misinterpretation of field measurements and thus to develop interpretation procedures that could lead to a rational selection of soil parameters and economical design.