Calibrations of the Innovative S₃F Sensor for Normal Stress Measurements in Soil

Surface stress sensitive film (S3F) sensor uses the 3D deformations of an elastic film to determine the applied normal and shear stresses over the sensor surface. Using such innovative sensors in geotechnical engineering applications promises accurate measurement of the normal and shear stresses. In this study, a method for the normal stress calibration of S3F sensor was proposed. The effect of the loading area on the normal stress calibration curves was investigated. And the performance of the sensor in measuring the normal stresses in the soil was assessed. The test result revealed that the slope of the normal stress calibration curve has inverse relationship with the diameter of the loading area as long as the loading area is equal or larger than the measurement area. The S3F sensor also showed its ability to measure the normal stresses within the soil mass with a good agreement with the theoretical stresses.