Cone penetration test

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 1950s 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. The test method consists of pushing an instrumented cone, with the tip facing down, into the ground at a controlled rate (controlled between 1.5 -2.5 cm/s accepted). The resolution of the CPT in delineating stratigraphic layers is related to the size of the cone tip, with typical cone tips having a cross-sectional area of either 10 or 15 cm2, corresponding to diameters of 3.6 and 4.4 cm. A very early ultra-miniature 1 cm2 subtraction penetrometer was developed and used on a US mobile ballistic missile launch system (MGM-134 Midgetman) soil/structure design program in 1984 at the Earth Technology Corporation of Long Beach, California.