A portable data collection system for simultaneous cone penetrometer forceand volumetric soil water content measurements

A new mechanism and sensors are described that can improve the quality of s oil penetration resistance data. The electric-motor-driven mechanism pushes the cone into the soil at a constant rate. The force measurement is made w ith a miniature load cell sensor located adjacent to the cone head to reduc e errors caused by friction between the soil and penetrometer shaft. A smal l water-content sensor is located on the shaft just above the load sensor, so that soil volumetric water content measurement is made on the hole walls just after the cone force is measured. The general nature of the electrica l performance of the water content sensor was evaluated for different probe : geometries by optimizing the portion of the electromagnetic energy passin g into the soil compared to that remaining in the probe. Some early field a nd laboratory test results art: shown, which were obtained using a complete prototype instrument. The resolution of each sensor is +/-0.03 m(3) m(-3) for water content, +/-0.0007 MPa for cone penetration pressure (cone index) and +/-0.003 m for depth.