This study shows change in the relative density of the ground calculated from the cone penetration resistance (CPR) of the ground around the pile after rotation penetration of a steel pile with flat plate wings into dry sand ground. As a result of these experiments with the relative density of original soil and wing diameter as parameters, a region occurred where the CPR decreased as the diameter of wings increased; this was particularly pronounced in high relative density soil. The complicated distribution of the CRP after pile penetration was discussed using the advancement ratio.
