Interpretation of SPT and CPT Data

Result obtained from standard penetration test (SPT) and cone penetration test (CPT) may be used to provide us some insights on the soil properties. This was made possible by using correlations developed by various researchers over the years.

Based on the type of sand, we can estimate its relative density, friction angle and saturated unit weight based on the normalized N70 values, as presented by Bowles (1996). As for the cohesive soil, we can use N60 to estimate its consistency index and unconfined compressive strength (Das, 2007). Alternatively, we may apply formulae to determine these parameters (Meyerhof, 1957; Cubrinovski & Ishihara, 1999; Peck et al., 1974; Wolff, 1989; Schmertmann, 1975; Kulhawy & Mayne, 1990; Hatanaka & Uchida, 1996; Hara et al., 1971; Mayne & Kemper, 1988).

Robertson (1990, 2005, 2016) has rigorously studied the ways to classify soil based on their behaviour type using CPT data. Based on normalized cone resistance and sleeve friction, one can easily estimate how would the soil behave. Various formulae are available to aid us in calculating the relative density and friction angle of cohesionless soil as well as undrained shear strength for cohesive soil using measured cone resistance (Kulhawy & Mayne, 1990; Lancellotta, 1983; Jamiolkowski et al., 1985; Ricceri et al., 2002; Mayne & Kemper, 1988; Anagnostopoulos et al., 2003).