ABSTRACT
Cone penetration test (CPT) started being used for soil investigation almost four decades after the standard penetration test (SPT). Despite their differences, both tests estimate the resistance of the soil against penetration of a probe. Although it is expected that the results of these tests are comparable and directly correlated, different driving mechanisms (static versus dynamic), sensitivity, type and frequency of measured parameters, operational errors, among others, compromise such correlations. In addition, the diverse nature of soils in terms of grain size, packing and fabric, shear strength, permeability, and other soil characteristics also limit the derivation of a unique correlation between CPT and SPT. Many authors have studied these in situ tests, recognizing that such correlation would be valuable, as it would enable the use of design methods and other libraries of correlations available for each individual test. A variety of formulas and charts has been proposed in the literature to describe this relationship, which demonstrates that this is a complex, not a global and simply predictable correlation. In this research, some of the most usual CPT-SPT relations are evaluated for a large dataset of field measurements from a pilot site on liquefiable soils, near Lisbon in Portugal. The extensive analysis of these data showed that the application of previously established, tested, and published correlations, available in the literature for specific sites, requires great care. One of the requirements is the verification of applicability, by comparison between the type of soils under study and those in the literature. Specific correlations for each geological condition must be defined before making engineering estimations based on correlated parameters.
