Slope deformation monitoring in the Jiufenershan landslide using time domain reflectometry technology

Abstract

This paper assesses potential slope movement in a landslide area using a grouted cable of time domain reflectometry (TDR) technology compared with data from an inclinometer and bore logs. The paper quantifies the magnitude of a TDR coaxial cable by laboratory shear and extension tests. The maximum and average magnitudes of cable deformation by laboratory shear failure were 60 mm and 47 mm, respectively. Then, in the paper, the results of the laboratory testing were applied to a case study where there were two inclinometers and two TDR monitoring stations. Based on laboratory shear and extension testing, differences in TDR-reflected waveforms can be regarded as locations of cable deformations. Meanwhile, the magnitude of cable deformations can be measured by the regression equation of the relation between reflection coefficients and shear displacements. Finally, the working limit of the cable for potential slope movement can be determined at 210-mρ reflection coefficient in laboratory and field testing. When a grouted cable ruptured, the TDR technology can detect a reflection coefficient at 210 mρ corresponding to the potential shear displacement at approximately 47 mm, which means that a localized slope deformation significantly occurred at the location of the cable rupture.