Comparison of CPT charts for soil classification using PCPT data: Example from clay deposits in Jiangsu Province, China

Geotechnical engineers worldwide practice a variety of in-situ techniques to classify soils in order to obtain their physical and engineering properties. An electric piezocone, which is an advanced version of the cone penetrometer, is capable of measuring cone resistance, sleeve friction and pore pressure. The piezocone testing data not only provide valuable information on soil types but are also useful in deriving correlations with the engineering properties of soil for the purposes of analysis and design of foundations. In a view to establish a region-specific correlation between piezocone penetration resistance and soil properties, piezocone penetration tests (PCPT or CPTu), borings, and other in situ tests were carried out at seven locations in Jiangsu Province, China. PCPT data were first used for classifying soil; thus the data were fully analyzed and validated for providing a reasonable soil classification. Several available CPT based classification charts are used to determine soil types; these results are further validated with the soil classification determined from the field samples and basic soil test results. This paper summarizes these analysis results, including description of the available charts and their performance in soil classification.

Research highlights
► The CPT classification methods are capable of interpreting the subsurface soil type.
► Robertson et al. (1986) method correlates well with the USCS results.
► Zhang and Tumay (1999) method provides similar results with Robertson method.
► Pore pressure correction appears to be important for fine-grained soils.