Determining relative density of sands from CPT using fuzzy sets

Significant discrepancy exists among the available correlations that are commonly used for determining relative density using cone penetration test (CPT) data. These correlations recognize the difference in sand compressibility and its effect on CPT data. Experience has indicated that compressibility is not a well-defined parameter. Current knowledge on the subject of sand compressibility and its effect on CPT data is limited and qualitative. A new approach that aggregates some of the available correlations for the determination of relative density using CPT data is developed. The new approach uses a weighting scheme that relates the compressibility, measured by friction ratio and expressed as a fuzzy number, to the base correlations. Field CPT data are used to examine and demonstrate the new approach. Results of the limited cases studied show that relative density can be determined reliably from CPT data using the proposed model.