Evaluation of a Piezoelectric Load Cell for Use on Cone Penetrometers

The diversified applications for soil penetrometers imply a need for improved load-sensing capability. The feasibility of using a piezoelectric transducer as a load-sensing device on a soil cone penetrometer was investigated. A miniaturized piezoelectric load cell (piezocell) was calibrated in a stand-alone mode using known static loads. The response of the load cell to loading cycles in this mode was also observed. The piezocell was integrated into the lower end of a penetrometer shaft such that it measured resistance sensed immediately at the base of the cone. A strain gauge load cell was integrated to the upper part of the penetrometer shaft to measure penetration resistance for comparative purposes. Penetrometer resistance was measured in soil columns in the laboratory using this penetrometer configuration. Piezocell resistance measurements compared well with the measurements by the strain gauge load cell in both calibration sensitivity and in time response. The physical and performance characteristics of the piezocell showed that it was well suited for use on cone penetrometers.