SLOPE INDICATOR - RADIAL & TANGENTIAL PRESSURE CELLS FOR TUNNELS

Application

The VW total pressure cells from Interfels are designed to monitor radial or tangential stress in tunnel linings.

Operation

The total pressure acting on the sensitive surface of the cell is transmitted to the oil inside the cell and measured by the VW transducer.

Shotcrete Installation: Cells are installed after excavating the tunnel but before applying the shotcrete. Radial cells are placed at the interface between the excavated ground surface and the shotcrete lining. Tangential cells are attached to the reinforcing cage or some other support so they will be embedded in the shotcrete lining. Once the cells are positioned, shotcreting takes place. After the shotcrete cures, tangential cells are pressurized by crimping the cell's pressurization tube, which forces oil from the tube into the cell. The influx of oil causes the cell to inflate, forcing the sensitive side of the cell into contact with the surrounding shotcrete material.

Precast Installation: Cells can be cast directly into lining segments at the casting yard.

Superior Construction: Cells are made from two oval stainless steel plates. The edges of the sensitive top plate are turned over the base plate and laser welded to form a sealed cavity which is later filled with de-aired oil. This construction minimizes tangential stiffness and prevents stiff weld joints and sharp edges.

VW Sensor: The VW pressure sensor eliminates hydraulic lines, provides more consistent readings, and has an RTD temperature sensor.

Small Height to Width Ratio: The small height to width ratio of the cell provides superior performance, even in stiff media such as concrete.

Manual or Automatic Readout: The VW transducer can be read manually with a VS or VWP Indicator, or automatically with a data logger.