Editing Time-domain reflectometer (section)

=== In geotechnical engineering ===
Time domain reflectometry has also been utilized to monitor slope movement in a variety of [[geotechnical engineering|geotechnical]] settings, including highway cuts, rail beds, and open pit mines (Dowding & O'Connor, 1984, 2000a, 2000b; Kane & Beck, 1999). In TDR stability monitoring applications, a coaxial cable is installed in a vertical borehole passing through the region of concern. The electrical impedance at any point along a coaxial cable changes with deformation of the insulator between the conductors. A brittle grout surrounds the cable to translate earth movement into an abrupt cable deformation that shows up as a detectable peak in the reflectance trace. Until recently, the technique was relatively insensitive to small slope movements and could not be automated because it relied on human detection of changes in the reflectance trace over time. Farrington and Sargand (2004) developed a simple signal processing technique using numerical derivatives to extract reliable indications of slope movement from the TDR data much earlier than by conventional interpretation.

Another application of TDRs in geotechnical engineering is to determine the soil moisture content. This can be done by placing the TDRs in different soil layers and measuring the time of start of precipitation and the time that TDR indicates an increase in the soil moisture content. The depth of the TDR (d) is a known factor and the other is the time it takes the drop of water to reach that depth (''t''); therefore the speed of water [[infiltration (hydrology)|infiltration]] (''v'') can be determined. This is a good method to assess the effectiveness of Best Management Practices (BMPs) in reducing [[stormwater]] [[surface runoff]].