This standard details the methodology for measuring earth pressure in-situ using a hydraulic pressure cell. It specifies the apparatus characteristics, calibration procedures, installation techniques, observation recording, and calculation methods for determining pressure in soil or on structures.
Method for measurement of earth pressure by a hydraulic pressure cell
Quick Reference Values
Cell aspect ratio (diameter to thickness)20 to 40
Maximum central deflection of cell membrane1/1000 of the cell diameter
Calibration pressure increments10 to 20 % of the design pressure
Thickness of sand pocket for installation2 to 5 mm
Key Formulas
P = P' + C — where P is earth pressure, P' is observed pressure, and C is the cell constant
Practical Notes
Complete de-airing of the hydraulic fluid and tubing is absolutely critical for obtaining accurate and responsive pressure readings.
The placement and orientation of the cell must be precise to measure the pressure component in the intended direction (e.g., normal or parallel to a structural surface).
Backfilling around the cell must be done carefully to match the density of the surrounding soil to avoid creating an artificially high or low-stress zone around the instrument.