Large diameter cone penetrometers: What is an appropriate location for the transition to the rod diameter?

15 cm² cone penetrometers are typically pushed to depth by means of 10 cm² rods. Therefore, a transition in diameter will be present at a certain distance from the cone shoulder. Although the standards give a requirement for the position of this transition, cone penetrometer configurations that don’t meet this requirement are often preferred by CPT sounding companies and are being used in practice. This raises a dilemma. In order to fuel discussion, a first step was made by performing two series of 9 CPTs with different penetrometer geometries. The effects of the penetrometer designs on the measured quantities were investigated. From a preliminary analysis of the results no systematical differences between the different penetrometers were observed. When these preliminary findings are better understood and validated, the standards can be updated.