IS 12208:1987 is the Indian Standard (BIS) for method for measurement of earth pressure by a hydraulic pressure cell. 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
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Cell Aspect Ratio (Diameter/Thickness) | Suggested to be not less than 20 to minimize arching. | No specific ratio is mandated; performance-based approach emphasizes matching cell stiffness to the ground to minimize inclusion effects. | ISO 18674-5:2020 |
| Over-range Capacity | Cell should withstand 1.5 times the design pressure. | Sensors should have an over-range protection of at least 150 % of the full-scale output (FSO). | ISO 18674-5:2020 |
| Hydraulic Fluid | Recommends de-aired oil or a mixture of ethylene glycol and water. | Specifies de-aired, non-gassing, low-viscosity, frost-resistant fluids (e.g., glycol-water mixtures). | ISO 18674-5:2020 |
| Tubing Material | Suggests twin nylon tubing of 3 mm internal diameter. | Mentions metal (e.g., stainless steel) or high-pressure polymer tubing, with an emphasis on durability. | ISO 18674-5:2020 |
| Readout System Accuracy | Bourdon gauge accuracy should be ±1 percent of the maximum dial reading. | Focuses on 'system uncertainty', which for high-consequence applications (Class 1) may be required to be <2% FSO. | ISO 18674-5:2020 |
| Maximum Diaphragm Deflection | Suggests maximum center deflection should be about 0.025 mm. | No specific value given; requires 'high stiffness' or 'low volume change' to ensure the cell measures stress, not strain. | ISO 18674-5:2020 |