VWIE-RST vibrating wire inline extensometer

Overview

The Vibrating Wire Inline Extensometer is used to determine the stability and movement behavior of soil, rock, and concrete structures inside a borehole at desired depths or elevations relative to a reference point. Its main advantage over conventional multi-point borehole extensometers is that no electrical head protrudes from the borehole.

The system sits flush with the borehole collar or ground surface and measures movement at multiple depths relative to a designated reference point. All displacement transducers are housed within sealed head and anchor assemblies installed inside the borehole, separated by extension kits of varying lengths according to the required measurement depths.

Architecture and operation

The extension sections use rigid 3/8-inch stainless steel rods protected by a 1/2-inch SCH40 PVC sheath. The larger rod diameter, compared with the 1/4-inch rods commonly used in conventional MPBX systems, provides improved accuracy for both extension and compression movement measurement.

Because all displacement transducers are installed in series, the total measurement range of the extensometer equals the sum of the individual transducer ranges. This allows significantly larger movements to be measured than with a conventional MPBX while using lower-cost standard-range transducers.

Operational advantages

• Flush-to-surface installation with no protruding electrical head.
• Can be used as a single-point or multi-point measurement system.
• Suitable for small and large extension and compression movements.
• Can be installed in smaller boreholes than a conventional MPBX.
• Rigid 3/8-inch stainless steel inner rod improves displacement accuracy.

Applications

It is intended for civil infrastructure, energy, surface mining, underground mining, and other geotechnical monitoring projects where internal deformation must be tracked without protruding surface hardware.