MEASUREMENT OF TAILINGS CONSOLIDATION USING TDR TECHNOLOGY

TDR is based on the principle of cable radar and is used with a variety of probes and coaxial cables to measure volumetric water content. In the case of saturated tailings, changes in the volumetric fluid content occur as the tailings solids displace pore fluids and recent studies with segmented probes at two mines have shown that may provide a reliable means for monitoring tailings consolidation and the impact on operating storage capacity and long term closure. Laboratory tests have been performed using a Georgia kaolin slurry with an initial void ratio of 4.7 that was consolidated under self-weight to a final void ratio of 2.35. This corresponds to a decrease in volumetric water content from 0.825 to 0.72. The propagation velocity profile was measured using a MoisturePoint segmented probe during the test, and using the default algorithm, the measured Vp decreased from 5.2 to 4.8. Considering such a small change in Vp over a very large change in void ratio, the sensitivity of TDR is much less than that which is possible from gravimetric measurements of water content. Although the qualitative trend is promising, it will be necessary to do a more fundamental analysis of changes in the TDR waveform rather than simply using the default algorithm in order to improve the sensitivity.

Dobroslav Znidarcic  
Dept of Civil, Environmental and Architectural Eng., Univ of Colorado at Boulder

Gordan Gjerapic
Dept of Civil, Environmental and Architectural Eng., Univ of Colorado at Boulder

Don A. Poulter
The Glasgow Engineering Group

Kevin M. O'Connor
GeoTDR, Inc.