Determination of drained friction angle of sands from CPT

Existing methods commonly used for determining drained angles of the internal friction of sands using cone penetration test (CPT) data are examined and interpreted in this paper, with emphasis on the influence of the compressibility of sands. The methods examined are based either on the bearing-capacity theory or on the cavity-expansion theory. This paper emphasizes the development of an empirical approach, based on the cavity-expansion theory, for determining the drained friction angle of sands from CPT data. To this end, a new empirical correlation for determining the volumetric strain, which is required in the Vesic method for determining the drained friction angle, is developed through calibrations with methods based on the bearing-capacity theory. Using this new empirical correlation, the volumetric strain can be obtained solely from CPT data without additional laboratory tests such as the triaxial test. Field CPT data are used to examine and demonstrate the new approach, and the results show that the drained friction angle can be consistently determined using this approach.