Time domain reflectometry (TDR) is performed as a complement to the monitoring methods in subsurface deformation in slope together with the global positioning system (GPS) to monitor ground deformation of high-altitude landslides in Li-shan. Four TDR cables were installed in drill holes near the monitoring stations in the landslide area. According to the recorded TDR waveforms, there were shear and tensile zones under the B-5, B-9, C-1, and C-2 stations. A comparison of the TDR waveforms with the monitored data and boring log revealed that the subsurface sliding occurred between layers of colluvium and strongly weathered slate. Three GPS receivers were installed to measure ground displacement in the landslide area. The results from the GPS were compared with the surface extensometers data on-site. The two initial baseline lengths were 451,188.10 and 908,212.4 mm, respectively. The optimal data reduction achieved used a 3 h session with moving average for each hour's GPS data. The standard deviation values of the GPS were 2.16 and 2.44 mm, respectively, on-site. The results of TDR and GPS measurements showed their applicability in the deformation monitoring of high-mountain landslides
SummaryTechniques presented herein show how reflected voltage pulses from coaxial antenna cable grouted in rock masses can be employed to quantify the type and magnitude of rock mass deformation. This measurement is similar to that obtained from a combined full profile extensometer (to measure local extension) and inclinometer (to measure local shearing). Rock mass movements deform the grouted cable, which locally changes cable capacitance and thereby the reflected wave form of the voltage pulse. Thus, by monitoring changes in these reflection signatures, it is possible to monitor rock mass deformation. This paper presents laboratory measurements necessary to quantitatively interpret the reflected voltage signatures. Cables were sheared and extended to correlate measured cable deformation with reflected voltage signals. Laboratory testing included development of grout mixtures with optimum properties for field installation and performance of a TDR (Time Domain Reflectometry) monitoring system. Finally, the interpretive techniques developed through laboratory measurements were applied to previously collected field data to extract hitherto unrealized information.
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