P8 Vibrating Wire Jack Out Pressure Cell
The Vibrating Wire Jack Out Pressure Cells are used to measure pressures on diaphragm walls during excavation.
They are installed within the diaphragm wall cage. An optional piezometer within the unit allows the measurement of pore water pressure and therefore the derivation of effective pressure.
The cell is mounted onto one end of a hydraulic ram via a swivel joint and at the other end is a reaction plate.
The cells are normally used to validate design assumptions and to give adequate warning of soil pressures in excess of those which a structure is designed to withstand.
- Uses proven Vibrating Wire technology
- Accurate, reliable and robust design
- Various ranges of size and pressure available
- Suitable for manual or remote monitoring
- Accurate, repeatable readings over long cable lengths
- Long working life with long-term stability
- Design prevents case stresses from affecting readings
- Over-voltage surge arrestor protects against electrical damage
The ram and cell assembly is installed into the reinforcement cage with the cell and reaction plate positioned on either side of the cage with the ram passing through the reinforcement. The assembly is loosely supported in the cage by tie wires and/or locally welded rods to form a cradle to provide free lateral movement of the unit. This arrangement allows the ram and cell assembly to centralise itself within the trench when the ram is extended. When the cage is lowered into the slurry-filled trench to the specified level, the ram is hydraulically pressurised to force the cell and reaction plate outwards to bear onto the sides of the trench.
The ram pressure is increased to ensure good embedment into the trench wall. The swivel joint behind the cell allows for some misalignment.
Ram pressure is maintained throughout the pour and curing of the concrete.
Vibrating Wire Jack Out Pressure Cells are installed within diaphragm walls to determine the distribution, magnitude and directions of total pressure. They can also be installed with a integrated piezometer to calculate effective pressure.
Typical applications include:
- Diaphragm walls