Magnetic probe extensometer available at Geomotion Australia

Magnetic Probe Extensometer

Extensometers

Magnetic Probe Extensometer GXM system monitors settlement and heave typically in deep excavations, dams, foundations, and embankments.

An access casing with multiple positioned magnetic targets on the exterior coupled to the surrounding soil is installed into a location to monitor movements down or up as settlement or heave occurs. A reed switch probe is lowered down the access casing to monitor the relative position of the magnetic targets via an activated buzzer and responding depth indicated on the tape.

Data obtained identifies the total amount, position and depth of the settlement that occurred. In stable ground the reference for depth of each magnetic target is the datum magnet fixed to the bottom of the access casing, in unstable ground the depths of the targets is referenced from the top of the casing, which is surveyed prior to readings being obtained.

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Product Features

  • Versatile system with a variety of magnetic targets to suit different applications
  • Measures settlement and heave
  • Oversized targets are available to use with inclinometer casing
  • Magnetic extensometer probe is available with various tape lengths
  • Access tube can be extended through fill material
  • Gives audio and visual indication of magnetic targets

Product Benefits

  • Reliable and accurate measuring system that is easy to read
  • Any number of targets can be monitored in a single borehole
  • One probe reads at many locations; only the access tubing and magnet targets are permanently installed in the ground

Operation

The access tubing is installed to the length required, by coupling together successive three-metre lengths. Magnetic targets are installed as needed along the tubing, to the required depth.

Fixed joints or telescoping should be used if large amounts of ground movement in the axis of the tubing are expected.

Measurements are taken by lowering the suspended probe down the access pipe and using the graduated tape to measure the distance from the top of the access pipe to each magnetic target.

By taking repeated probe measurements of each target over a period of time, this shows any displacement of the ground being measured. Changes in this distance relative to the datum magnet near the base of the pipe will reflect the rock and soil movements along the axis of the access casing.

Alternatively, readings may also be made relative to topographic survey measurements taken from the measuring point at the top of the access tubing.

Applications

The Magnetic Extensometer System is installed at locations where monitoring of settlement or heave is needed.

Typical applications include:

  • Excavations
  • Foundations
  • Dams
  • Embankments
  • Retaining structures, such as sheet piles and slurry walls
  • Tunnels and shafts
  • Surcharge sites.

Related products

Geomotion offers installation and monitoring services to support this system. For more information, please email info@geomotion.com.au or contact any of our locations.

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