Interfels Push-In Vibrating Wire Pressure Cell is normally installed in vertical boreholes and measures total horizontal stresses. They are often installed in stiff clay (shear strength of approximately 300 kN/m) behind and in front of retaining walls, in soft puddle clay cores of old embankment dams and in glacial till adjacent to sea cliffs.

The cells can also be installed in horizontally drilled boreholes for example from tunnels and cliff faces. In these situations both horizontal and vertical stresses can be measured by the appropriate orientation of a number of cells. The cells may be used as a site investigation tool to measure the in situ stresses in the ground prior to any disturbance.

Manufactured incorporating Interfels 30 years of expertise in vibrating wire instrument technology, the Push-In VW Pressure Cell consists of a pointed rectangular spade shaped oil filled chamber formed from two sheets of steel welded around their periphery. A short length of steel tube connects the oil filled cell to a vibrating wire pressure transducer, thus forming a sealed hydraulic system.

The incorporation of a VW Piezometer in the instrument enables pore water pressure to be measured and therefore the effective stress can easily be determined. Furthermore the cells are fitted with thermistors for correcting the effects of temperature variations on pressure readings.