ABSTRACT
The cone tip load cell needs to be calibrated before the cone penetration test (CPT) data in soil can be used to interpret the soil properties. The cone tip load cell is routinely calibrated through cone tip axial loading test. In this study, the CPTs were conducted in fully saturated layered clay deposits in a centrifuge. The net cone resistance was found to be negative by using the calibration factor obtained through axial loading test. This is illogical. Further CPT calibration was performed in water in the centrifuge under 150 times earth gravity. The CPT calibration factor under ambient pressure in water was found to be different from that obtained through axial loading test. By using both calibration factors from axial load test and under ambient pressure, the net cone resistance was recalculated. The interpreted soil undrained shear strength using the recalculated net cone resistance was consistent with that from a parallel ball penetrometer test. Since the soil overburden pressure acts on the cone tip as an ambient pressure, the cone tip load cell should be calibrated under ambient pressure to provide logical interpretation of CPT data.
