The conepenetration test or CPT consists in thedriving a conepieceintothesoil, linked to a load cell which measures, in a continuousway, soilresistance to penetration of theconetip (qc). It also measures simultaneously resistance of lateral friction (fs) that presents the soil when passing a cylinder piece placed immediately over the cone tip. A drawing and a photo of these measuring elements can be observed in Figure 1.

The technique of drive rods on the ground with geotechnical purposes is a very antique practice used at the beginning for soft soils to find the depth of a firm stratum. First versions of this probe were developed in Sweden in 1917 and it consisted of driving a helical tip, by means of static load and byrotation. As known nowadays the CPT with mechanical tip began to be used in Holland in 1934 to evaluate load capacity of driven piles. Later, in 60’s, the electric CPT emerged in which resistance of tip (qc) and sleeve friction (fs) are electrically measured through two load cells mounted with “strains gauges”. From the beginning this test began to be used as a habitual tool in geotechnical researches in field, as [1] expresses, especially to establish the subsoil profile quickly and economically.

According to [2] , the CPT has three main applications: 1) determining subsoil profile and identifying soils types present, 2) interpolating subsoil conditions between control boreholes, and 3) evaluating geotechnical parameters to estimate load capacity and settlements. Identification of soils types will be treated in this work. Determination of geotechnical parameters is made by the use of empirical correlations. Alternatively, direct methods, without previous determination of parameters, are used to estimate load capacity and settlements. Besides these applications that are routine in geotechnical practices, in recent years they began to be employed to determine composition and distribution of pollutants in soils [3] .

One of the major uses of CPT is to identify the soil profile. With this test, it is posible to obtain better results than others made with conventional methods. Many researchers have proposed to identify soils types as a function of tip resistance (qc) and friction ratio (Rf = fs/qc), and for this they proposed the use of graphics or charts in empirical correlations (e.g. [4] - [8] ).

These classifications are based on earlier observations made in Holland, which indicated that sand soils tend to produce high tip resistance and low friction ratio, whereas soft clayey soils tend to produce low tip resistance and high friction ratio.

In this sense, studies made using the mechanical CPT were initiated by [4] and continued later by [5] . In Reference [6] , he incorporated results of a great number of tests proposing a classification graph as a function of (qc) and (Rf) magnitudes using the mechanical CPT. For the case of electric tip with standardized geometry, [7] proposed a graph whose correlations are based on a great number of results from tests on the West of the United States. Later, based on an expanded database, [8] presented a soil type classification chart that is broadly used at present and reproduced in Figure 2.

Reference [2] remarks the necessity of continuing deepening the study of soil identification by the CPT through comparison of obtained results with direct identification in a sampling borehole. He even emphasized that local experiences could differ from studies already made in other places.

Local experience regarding the use of CPT may be said too recent, since it was incorporated in the half of the 90s. However, its continuous and systematic use in geotechnical studies makes that nowadays database can be gotten bigger enough to verify application of international correlations to local soils.