Calibration of An Earth Pressure Cell
Brent Theroux, Joseph F Labuz, Andrew Drescher
Report no. MnDOT 2000-34
Projects: Calibration of Earth Pressure Cells
In this study, researchers devised a scheme for calibration of earth pressure cells to observe their response to various loading configurations and to recommend a procedure for field installation. Transducers designed to provide an estimate of normal stress within a soil, earth pressure cells have provided readings that conflict with known loading conditions. Initial calibration tests used hydraulic oil as the pressurizing medium in both hydrostatic and uniaxial pressure conditions, which mimic the manufacturers' procedure for pressure cell calibration. Researchers designed a new testing device to permit the application of uniaxial soil pressure to the earth pressure cells using various types of soil and load configurations. As a result of calibration tests, a field installation procedure was developed and recommended. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand of a known density, and the earth pressure cell was placed within the sand. The entire apparatus was carried into the field and installed in the desired locations. Once in place, the steel cylinder was pulled up out of the ground, leaving the cell and geotextile behind. Preliminary field data indicate that soil calibration and placement procedure provide reasonably accurate measurements.