Automatic penetration test in geotechnical engineerin
The cone penetration or cone penetrometer test CPT is a method used to determine the geotechnical engineering properties of soils and delineating soil stratigraphy. It was initially developed in the s at the Dutch Laboratory for Soil Mechanics in Delft to investigate soft soils. Based on this history it has also been called the "Dutch cone test". Today, the CPT is one of the most used and accepted soil methods for soil investigation worldwide.
Geotechnical characterization of natural soils by in situ testing
Standard Penetration Test
It provides assessment of soil properties and foundation design parameters. The N SPT index depends not only on the soil properties and the SPT setup characteristics, but also on the energy delivered to the string of rods and to the SPT sampler during the hammer impact. This paper presents the results of SPT tests performed with two instrumented subassemblies, one placed at the top and the other one at the bottom of the string of rods. This instrumentation allowed the assessment of the amount of energy transmitted to the string of rods, at sections just below the anvil and just above the sampler. Results show that the developed instrumentation is suitable to predict the amount of energy, at different sections, during the sampler penetration into to the soil.
It is similar to CPT in that a metal cone is advanced into the ground to continuously characterize soil behavior. However, unlike in CPT, where the cone is driven into the ground at a constant rate by varying amounts of force, in DCP, the cone is driven by a standard amount of force from a hammer, and how far the cone moves with each blow is used to determine the soil density and properties at that level. In DCP testing, the pushing force is applied by manually dropping a single or dual mass weight called the hammer from a fixed height onto the push cone unit. The resulting downward movement is then measured. Unlike CPT systems, basic DCP equipment is hand-portable and may be limited to test depths of feet: this makes it a good choice for shallow testing applications such as road bed construction and maintenance.
In situ testing plays a crucial role in the subsoil geotechnical characterization. Significant efforts have been put on the refinement of testing procedures as well as on the improvement of data interpretation. Our recent research activity in this field has been mainly focused on the CPTU-based characterization of silts and other intermediate soils, such as clayey sands, silty sands or silty sands with clay, having very scattered grain size distributions and thus falling in the so-called intermediate permeability range i. Indeed, cone penetration test response in similar deposits is, in all probability, affected by partial drainage effects and the preliminary identification of the drainage degree is a key step in order to avoid misinterpretation of field measurements and, thus, invalid estimates of soil parameters. In order to analyse the effect of partial drainage on measurements and to identify probable consolidation patterns during cone penetration, in last years a large number of variable rate CPTU tests have been carried.