ABSTRACT
As the ISSMFE was unable to standardize the method and equipment to be used for the SPT internationally, the SPT Working Party o f the ISSMFE Technical Committee on Penetration Testing proposed the “International Reference Test Procedures on SPT”, at ISOPT-1, Orland in 1988. A method using stress wave equation analysis was introduced in Document 4-Calibration Methods for the adjustment o f the N-values in the SPT to account for different magnitudes o f driving energy, as a means o f quality control for the SPT. The method was established by referring to studies made by Uto et al. (1974), Schmertman et al. (1979) and others. In the author’s opinion, the calibration methods are unable to account for a difference in the size o f equipment, however, this could be corrected by calculations and the formula to be applied for the adjustment o f A^values should be revised.
