Simplified Calibration Procedure for Total Earth Pressure Cells: Fid-Bau Portal

Simplified Calibration Procedure for Total Earth Pressure Cells

Baker, William J. / Meehan, Christopher L.

Earth pressure cells (EPCs) are typically utilized to measure total soil and water pressures in situ. Installed EPCs exhibit an active stress arching phenomenon in which the stress sensed by the EPC is smaller than the stress in the soil surrounding the EPC. Unfortunately, the hydrostatic calibration factor provided by the manufacturer cannot account for this phenomenon, resulting in the need to independently calibrate a given EPC in the laboratory before it is installed in situ. Though other researchers have conducted their own independent laboratory calibration of EPCs in dry sand, the custom testing setups that have been developed for this calibration procedure have required special apparatus fabrication, which makes these procedures difficult to replicate. In the current study, a simplified testing apparatus and method were developed to calibrate EPCs in dry sand, which utilize standard equipment that is commonly found in most geotechnical testing laboratories. Three 1-MPa-range semiconductor EPCs were calibrated in dry sand at various sand column heights ranging from 5 cm to 30 cm by subjecting them to ten loading cycles at each column height. The goal of this study was to examine the influence of sand column height and load cycles on the EPCs’ associated sensitivity ratio. Overall, the results observed in the current study were consistent with results presented by previous researchers for EPCs calibrated at the same sand column height using larger and more sophisticated testing setups; this indicates the potential utility of the simplified calibration procedure that is described in the current paper for independent calibration of EPCs.