Metallic Time Domain Reflectometry (MTDR) is a simple and economical way of detecting and interpreting rock and soil mass response to underground and surface mining using coaxial cables grouted in boreholes. MTDT can be used effectively to locate rock and soil mass movements. 

MTDR involves the installation of a coaxial cable in a borehole filled with grout that matches existing soil or rock conditions. A TDR cable test unit is employed to generate a voltage pulse along the cable and receive reflections. Reflections are generated by cable deformations, abrasions, and severing. Crimps at known locations along the cable are used to provide depth datum. 

As movement occurs, the reflections along the cable change as the cable deforms. By connecting the cable tester to a PC through an RS232 cable, MTDR reflection can interpreted by software, thereby inferring location, type and rate of earth movement. MTDR systems can be combined with data loggers and multiplexers to allow remote readings of multiple cables.

RST Instruments Ltd., 11545 Kingston St., Maple Ridge, BC, Canada V2X 0Z5, Tel.: 604-540-1100, 1-800-665-5599, +1-604-787-9673, e-mail: info@rstinstruments.com