SLOPE INDICATOR - TOTAL PRESSURE CELLS

Application

The total pressure cell measures the combined pressure of effective stress and pore-water pressure. Typical applications include:

• Monitoring total pressure exerted on a structure to verify design assumptions.

• Determining the magnitude, distribution, and orientation of stresses.

Operation

The total pressure cell is formed from two circular plates of stainless steel. The edges of the plates are welded together to form a sealed cavity, which is filled with fluid. Then a pressure transducer is attached to the cell. The cell is installed with its sensitive surface in direct contact with the soil. The total pressure acting on that surface is transmitted to the fluid inside the cell and measured by the pressure transducer.

Installation

Total pressure cells are embedded in fill or mounted on structures. In fill, cells are often installed in arrays. Each cell is placed in a different orientation and covered with hand-compacted fill. On structures, the cell is typically placed into a recess so that its sensitive side is flush with the surface of the structure.

Advantages

Conformance: To minimize bridging effects, the total pressure cell has a low profile and a modulus similar to that of a typical soil. Fluid in the cell is de-aired to maximize sensitivity.

Accurate Calibration: The total pressure cell is calibrated under fluid pressure in a custom-designed test fixture.

Pneumatic or Vibrating Wire: The total pressure cell is available in a pneumatic or vibrating wire version.

Manual or Automatic Readout: The vibrating wire version can be read manually with a portable indicator or automatically with a data logger. The pneumatic version must be read manually.