Continuous Rod Extensometer
The Continuous Rod Extensometer system accurately measures settlement and/or heave at single or multiple anchor points in a borehole and at its reference head.
The system employs up to eight rods, anchored along the axis of a borehole, terminating in the reference head at the borehole entrance.
Displacement along the axis of the borehole from the anchor is recorded by measuring movement of the top of the rod relative to the reference head.
The Continous Rod Extensometer is pre-assembled to specified lengths.
A versatile range of options are available for Continuous Rod Extensometers:
- Automatic or manual reading
- Hydraulic anchoring for soil
- Groutable anchoring for rock
- Multiple or single point rod reference
- Rods and anchors are delivered pre-assembled to customer specified length
- Various anchor types available according to soil conditions and installation method
- Manual or remote monitoring
- Remote option uses Vibrating Wire or potentiometric displacement transducers
- Up to 8 measuring points per borehole
- Installation in drillholes or boreholes at any orientation
- Quicker installation than conventional rod extensometer systems
- Fibreglass less sensitive to temperature changes than steel
- Particularly useful in confined areas
- For borehole diameters up to 200mm
Relative movement between the end anchor and the reference tube is measured with either a digital depth gauge, or a displacement transducer inserted through the reference tube and registering on to the free end of the rod.
The ground condition determines the type of anchor to use:
- Groutable anchors for downhole installation in rocks
- Hydraulic type anchors (single or double ended) for soft soils
- Packer anchors for jointed rocks, where there is flowing water, or uphole installations
The extensometers have reference heads with provision for up to eight measuring points per borehole. Borehole diameters may be in the range of 100mm-200mm.
Continuous Rod Extensometers are used to monitor small scale rock and soil movements to a high degree of accuracy, including settlement and heave of foundations, the relaxation or subsidence of rock around tunnels, shafts, caverns and abutments.
Typical applications include:
- Monitoring settlement and heave in foundations
- Monitoring tunnels, shafts, caverns and abutments
- Control of natural and cut slopes, quarry and mining excavations
- Monitoring deformation of retaining walls, bridge piers and abutments