Vibrating-wire earth pressure cells are often used to measure soil pressure in fills and embankments or contact pressure between soil and buried structures. Instrumentation companies provide each cell with a formula to calculate pressure based on frequency and temperature readings. This paper presents the calibration work that was carried out on a series of 76 mm diameter cells and four 228 mm diameter cells with temperatures ranging from 10 to +30 °C with and without the effect of applied pressure. Based on this work and additional data from two field sites, it was found that temperature calibration factors given on the calibration sheet specific to each cell largely underestimated the temperature effect. It was also found that the correction factors were dependent not only on temperature, but also on the pressure applied to the cell. The temperature calibration factor, which is given as a linear correction on the calibration datasheet, becomes parabolic as a pressure is applied on the cell. Based on the findings, recommendations are provided for minimizing the temperature effect on pressure cell readings and improving the accuracy of the temperature calibration factor.Key words: earth pressure cells, soil pressure, temperature calibration, instrumentation.
Development of Gas Viscosity Measurement System with Vibrating Wire Method
