Metallic Time Domain Reflectometry
Metallic Time Domain Reflectometry

Metallic Time Domain Reflectometry

Metallic Time Domain Reflectometry (TDR) is a simple and economical way of detecting and interpreting rock and soil mass response to underground and surface mining using coaxial cables grouted in boreholes.

Product Features

  • Economic installation
  • Low data acquisition costs
  • Ability to monitor deformation along the entire length of the borehole
  • Can be used with RST’s FlexDAQ Data Loggers, GeoViewer Software, and GeoExplorer
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Description

Metallic Time Domain Reflectometry (TDR) is a simple and economical way of detecting and interpreting rock and soil mass response to underground and surface mining using coaxial cables grouted in boreholes. TDR
can be used effectively to locate rock and soil mass movements.

TDR involves the installation of a coaxial cable in a borehole filled with grout that matches existing soil or rock conditions. A TDR unit is employed to generate a voltage pulse along the cable and receive reflections. Reflections are generated by cable deformations, abrasions and severing. Crimps at known locations along the cable are used to provide depth datum.

As movement occurs, the reflections along the cable change as the cable deforms. By connecting the TDR200 to a PC through Type A Micro B USB cable, TDR reflections can be interpreted by software, thereby inferring location, type and rate of earth movement. TDR systems can be combined with data loggers and multiplexers to allow remote readings of multiple cables.

Spesification

Item  Specification 
Tensile Strength 113 kg
Maximum Tensile Force 1100 N (247 lb)
Maximum (Recommended) Clamp Spacing 0.6 / 1 m (2 / 3.25 ft)
Minimum Bending Radius, Single Bending 70 mm (3 in.)
Minimum Bending Radius, Repeated Bending 125 mm (5 in.)
Bending Moment 6.5 Nm (4.79 lb-ft)
Installation Temperature – 40 to +60 °C (-40 to 140 °F)
Operation Temperature – 50 to +85 °C (-58 to 185 °F)
Storage Temperature – 70 to +85 °C (-94 to 185 °F)
Inner Conductor Copper-Clad Aluminium Wire, 4.8 mm (0.19 in.)
Dielectric Foam Polyethylene, 11.9 mm (0.47 in.)
Outer Conductor Corrugated Copper, 13.8 mm (0.54 in.)
Jacket Material Polyethylene, PE 15.8 mm (0.62 mm)
Weight 0.2 kg/m (0.14 lb/ft)
Characteristic Impedance 50 ± 1 Ω
Relative Propagation Velocity 88%
Capacitance 76 pF/m (23.2 pF/ft)
Inductance 0.19 μH/m (0.058 μH/ft)
Maximum Operating Frequency 8.8 GHz
Jacket Spark Test RMS 8000 V
Peak Power Rating 38 kQ
RF Peak Voltage Rating 1950 V
DC Resistance, Inner Conductor 1.57 Ω/km (0.45 Ω/1000ft)
DC Resistance, Outer Conductor 2.7 Ω/km (0.82 Ω/1000ft)

Applications

Time Domain Reflectometry is commonly used for:

  • Monitoring rock and soil movement.
  • Monitoring subsidence above abandoned underground mines.
  • High wall slope monitoring in open-pit mines.

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