Vibrating Wire Push-In Pressure Cells can be used as a site investigation tool to determine the in situ stress state, both vertical and horizontal, depending on the direction of installation. In addition, it can be used to monitor the change in active and passive pressure around retaining structures such as diaphragm walls, or used for monitoring the injection grouting process, as well as other earthworks projects. 

Typical installations are in fine grained cohesive soils, including very soft to stiff clays to allow for a push-in installation method.
Construction consists of two longitudinal stainless steel plates welded together around their periphery in a spade shape. The annular space between these plates is filled with de-aired glycol. A port and filter for pore water pressure measurement are located on one of the flat sides of the support plate behind the pressure sensitive section of the cell.
The pressure cell and the port for the pore water pressure are connected via stainless steel tubes to two vibrating wire pressure transducers inside in the sensor assembly. A thermistor for temperature measurement is also incorporated in the cell.
The installation method consists generally in drilling a pilot hole slightly shorter than the planned installation depth, and then to push the pressure cell about 1 meter past the bottom of the pilot hole using standard drill rods or CPT rods that will be left in place or retrieved at a later stage after measurements are completed. Push rods and push adapters can also be used if the cell is to be installed and left permanently in place, with retrieval of the installation rods (see ordering info or contact our sales team to discuss what is best for your application).

Product features

• Integrated pore pressure and total pressure measurement
• Reduces the need for multiple sensors
• Typically used to monitor stress change adjacent to retaining walls or stress redistribution around tunnels in soils
• Can be installed via retrievable or non-retrievable methods