Browsing by Author "Tang, Shr-Hong"

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An Improved Modeling of TDR Signal Propagation for Measuring Complex Dielectric Permittivity
(2015-12-01)
Lin, Chih-Ping
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Tang, Shr-Hong
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Lin, Chun-Hung
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Chung, Chih-Chung
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土木工程學系
Time domain reflectometry (TDR) is a measurement technique based upon transmission line theory. The solutions of transmission line equations are reformulated in terms of independent physical properties, instead of coupled per-unit-length circuit parameters. The complete TDR response is effectively modeled by a non-uniform transmission line using the non-recursive ABCD matrix approach. Approaches to calibrate line parameters and perform TDR measurements based upon such model are introduced with an example on dielectric spectroscopy. TDR modeling in terms of decoupled physical parameters and non-recursive algorithm allows more convenient calibration of line parameters and facilitates interpretation of TDR measurements.
Comprehensive wave propagation model to improve TDR interpretations for geotechnical applications
(2007-03-01)
Lin, Chin-Ping
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Tang, Shr-Hong
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交大名義發表
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National Chiao Tung University
Time domain reflectometry (TDR) is becoming an important monitoring technique for various geotechnical problems. Better data interpretation and new developments rely on the ability to accurately model the TDR waveform, especially when long cables are used. This study developed an efficient, complete, and general-purpose TDR model that accounts for all wave phenomena including multiple reflection, dielectric dispersion, and cable resistance all together. Inverse analysis based on the TDR wave propagation model is proposed to calibrate the TDR system parameters and determine the TDR parameter that changes with the physical parameter to be monitored. Calibration of TDR cable and data interpretations for various geotechnical applications were demonstrated with laboratory experiments. The excellent match between the simulated and measured waveforms validates the TDR wave propagation model. The results show that the proposed numerical procedure is a relatively simple, efficient and high-resolution tool for probe design, parametric studies, data interpretation, and inverse analyses. This study should provide a sound theoretical foundation for further TDR developments in geotechnical monitoring.
Quantification of Cable Deformation with Time Domain Reflectometry-Implications to Landslide Monitoring
(2009-01-01)
Lin, Chih-Ping
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Tang, Shr-Hong
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Lin, Wen-Chin
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Chung, Chih-Chung
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交大名義發表
Time domain reflectometry (TDR) technology has become a valuable tool for detecting displacements and locating shear planes in rock or soil slopes. It is based on transmitting an electromagnetic pulse into a coaxial cable grouted in rock or soil mass and watching for reflections of this transmission due to cable deformity induced by the ground deformation. Early detection of localized shear deformation in soft soils and quantifying the shear displacement using TDR remains a challenging work. The TDR response due to localized shear deformation is affected by cable resistance, soil-grout-cable interaction, and shear bandwidth. A comprehensive TDR wave propagation model considering cable resistance is introduced to model TDR response to cable deformity. Effects of the influencing factors on the relationship between the reflection spike and the shear displacement are investigated through laboratory tests and numerical simulations. The implications to enhancing TDR response and quantifying shear displacement are stressed. Practical suggestions are made, including procedure for correcting resistance effect, selection of cable and grout, and how to quantify shear displacement using TDR.