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Date Created
2001
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An earth pressure cell (EPC) is a device designed to provide an estimate of normal stress in soil. The practice of designing and manufacturing stress measurement devices revolves around the study of the interaction between the measuring device – the earth pressure cell – and the host material. However, distribution of normal stress is not necessarily uniform across a given surface. Consequently, output from an EPC may be different under soil loading conditions than under fluid pressure. In addition, depending upon the design, as the cell deflects, an arching-type phenomenon may develop.
The objectives of this study were to devise a scheme for calibration of earth pressure cells and to recommend a procedure for field installation. A new testing device was designed to permit the application of uniaxial soil pressure to the earth pressure cell using various types of soil and load configurations. Sensitivities computed from soil calibrations varied from those determined from fluid calibrations by as much as 30%.
A field installation procedure was developed from model tests. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand in a medium dense state and the earth pressure cell was placed within the sand. The entire apparatus (earth pressure cell, cylinder, and sand) 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, sand, and geotextile behind. Preliminary field data indicate that the soil calibration and placement procedure provide reasonably accurate measurements of the change in vertical stress.
Content Note: This is the author’s version of a work that was accepted for publication in the Transportation Research Record: Journal of the Transportation Research Board, Issue Number: 1772, Publisher: Transportation Research Board ISSN: 0361-1981. The final version can be found at https://doi.org/10.3141/1772-02.
The objectives of this study were to devise a scheme for calibration of earth pressure cells and to recommend a procedure for field installation. A new testing device was designed to permit the application of uniaxial soil pressure to the earth pressure cell using various types of soil and load configurations. Sensitivities computed from soil calibrations varied from those determined from fluid calibrations by as much as 30%.
A field installation procedure was developed from model tests. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand in a medium dense state and the earth pressure cell was placed within the sand. The entire apparatus (earth pressure cell, cylinder, and sand) 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, sand, and geotextile behind. Preliminary field data indicate that the soil calibration and placement procedure provide reasonably accurate measurements of the change in vertical stress.
Content Note: This is the author’s version of a work that was accepted for publication in the Transportation Research Record: Journal of the Transportation Research Board, Issue Number: 1772, Publisher: Transportation Research Board ISSN: 0361-1981. The final version can be found at https://doi.org/10.3141/1772-02.
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2001MRRDOC010_01-3356.pdf
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https://hdl.handle.net/20.500.14153/mndot.16085