Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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Application of Time Domain Reflectometry to the Monitoring or Rock Mass Deformation with Coaxial Cable

동축 케이블을 이용한 시간영역 반사법의 암반변위 계측에의 적용

  • Published : 1996.12.01
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Abstract

This paper presents an application of the TDR(Time Domain Reflectometry) to the monitoring of the deformation of rock mass with grouted coaxial cables through laboratory tests. The grouted cable can easily deform together with the rock mass movements, and the deformed cable loses its original capacitance and the reflected waveform produced along the deformed cable consequently represents a change of voltage pulse. Therefore, it is possible to monitor the deformation of rock mass by measuring the changes in these reflection signatures. Shear test of the cemented mortar containing a specimen of coaxial cable showed that the shear deformation correlated linearly with the reflection coefficient, so the TDR was effective to monitor the displacement of the rock mass. Bending test were carried out in order to determine the influence of the crooked cables on the monitoring of rock mass movements. Controlled cirmping and shearing test upon a cable of 50 m long, 12.7 mm diameter showed not only the fact that the reflection amplitudes decreased as the cable length increased but also the proper crimping depth, width and interval between two adjacent crimps. Two coaxial cables-one 100 m long and other 175m long-were installed and grouted into the separate boreholes drilled in a sedimentary formation. The behavior of the cable was monitored with metallic TDR cable tester to measure rock mass deformation based on the interpretative techniques developed through laboratory tests.

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References

  1. Engineering Design News no.November Time Domain Reflectometry-Theory and Applications Moffitt, L. R.
  2. Water Resources Research v.16 no.3 Electromagnetic Determination of Soil Water Content: Measurements in Coaxial Transmission Lines Topp, G. C.;Davis, J. C.;Annan, A. P.
  3. J. Phys. Chem. v.79 no.149 Evaluation of Dielectric Behavior by Time Domain Spectroscopy, 1, Dielectric Response by Real Time Analysis, 2, Complex Permeability, 3, Precision Difference Methods Cole, R. H.
  4. RI 8585, U. S. B. M. Monitoring Ground Movements Near Caving Slopes - Methods and Measurements Panek, L. A.;Tesch, W. J.
  5. Int. J. Rock Mech. Min. Sci. & Geomch. Abstr. v.25 no.5 Principles of Time Domain Reflectometry Applied to Measurements of Rock Mass Deformation Dowding, C. H.;Su, M. B.;O'Conner, K. M.
  6. Rock Mech. and Rock Engng. v.22 Measurement of Rock Mass Deformation with Grouted Antenna Cables Dowding, C. H.;Su, M. B.;O'Conner, K. M.
  7. Symp. and Workshop on Time Domain Reflectometry in Environmental, Infrastructure, and Mining Applications Measurement of Localized Failure Planes in Soil with Time Domain Reflectometry Dowding, C. H.;Pierce, C. E.
  8. Symp. and Workshop on Time Domain Reflectometry in Environmental, Infrastructure, and Mining Applications Use Of Time Domain Reflectometry to Detect Bridge Scour and Monitor Pier Movement Dowding, C. H.;Pierce, C. E.
  9. Symp. and Workshop on Time Domain Reflectometry in Environmental, Infrastructure, and Mining Applications Effects of Multiple Crimps and Cable Length on Reflection Signatures from Long Cables Pierce, C. E.;Bilaine, C.;Huang, F. C.;Dowding, C. H.
  10. Symp. and Workshop on Time Domain Reflectometry in Environmental, Infrastructure, and Mining Applications Telemetric and Multiplexing Enhancement of Time Domain Reflectometry Measurements Huang, F. C.;Dowding, C. H.