Time Domain Reflectometry (TDR) is increasingly being used in geotechnical applications for deformation monitoring in soils and concrete. It provides accurate location information for faults and can provide indication of the static or dynamic nature of the faults. It is typically used to monitor slope movement of embankments including highway cuts, rail beds, bridge abutments and open pit mines.

In TDR applications the signal is an electrical pulse broadcast down a coaxial cable, and changes in the impedance of the cable, either inductive or capacitive, cause reflections to be returned to the signal generator. The resultant reflections are measured and presented as a function of time, the time is translated to distance based on the known propagation velocity of the cable being utilized. In geotechnical applications the cable typically takes the form of a rugged coaxial cable with a diameter of 12mm (0.5”). The cable is usually grouted into a borehole drilled into the embankment to be monitored. Any movement of the embankment will crimp the cable, and the reflections indicate approximate magnitude of the crimp and the location. The resolution is related to the number of samples of data being collected.