Embankment monitoring with time domain reflectometry

Time domain reflectometry (TDR) is used to determine embankment slope movement and piezometric levels easily, safely, and economically. The digital nature of the data allows remote monitoring by telemetry. A cable tester sends a waveform down a coaxial cable embedded in a vertical hole. If the pulse encounters a deformation or the presence of water, it is reflected. The distance to the point of reflection is determined by the cable tester. This is used to locate shear failure in the embankment. The amplitudes of the reflections in a TDR signature indicate the severity of damage to the cable. Changes in amplitude with time correspond qualitatively to the rate of ground movement. Piezometric levels are determined by using a hollow coaxial cable as a standpipe. Water levels are measured by noting the location where the cable displays an electrical fault.