Effects of Multiple Crimps and Cable Length on Reflection Signatures from Long Cables
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2002-03-19
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NTL Classification:NTL-HIGHWAY/ROAD TRANSPORTATION-HIGHWAY/ROAD TRANSPORTATION
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Abstract:The accuracy of time domain reflectometry (TDR) measurements of rock shearing with cable lengths greater than 60 m has not been adequately documented. This paper presents the results of controlled crimping and shearing of a 530 m long, 22.2mm diameter coaxial cable for comparison with theory and the existing data from cables up to 60 m long. Effects of both single and multiple deformities along transmission lengths of 94m, 268m, and 530m were investigated. The Northwestern University TDR Signature Analysis (NUTSA) program was employed to track and analyze reflection spikes in the waveforms produced by controlled deformation. The results show that pulse attenuation has a significant effect on signal reflections. Reflection amplitudes were reduced by 500% as cable length increased from 94 m to 268 m. Signal reflections produced by downstream deformations are slightly decreased (amplitude reduction <) when single or multiple deformations are applied upstream on the cable. Deformation-reflection relationships can be characterized as bi-linear or exponential, and show that shear deformation can be effectively correlated with TDR reflection amplitude at distances up to 268 m.
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