Abstract

Tailings dams are massive structures designed to contain the waste slurry remaining after processing ore at open pit and underground mines. These structures fail far more regularly than normal water-storage dams. In recent years, catastrophic tailings dam failures have occurred, causing significant damage to the environment and even loss of life. To mitigate these catastrophic events in the future, there is an urgent need to develop cost-effective methods to monitor the structural stability of these constructions over time. The lack of current cost-effective monitoring methods prompted us to investigate whether ambient seismic noise can be used to detect internal changes in a tailings dam wall during a period of heavy rainfall. We recorded three weeks of continuous seismic data with 10 short-period geophones at a tailings dam in Tasmania, Australia. Seismic interferometry was used on ambient noise to create virtual seismic sources. With these virtual source signals, small changes in seismic velocity were measured daily and compared to rainfall, seepage flow rates, and fluid pore pressure. The observed velocity changes were driven by fluid saturation, ground water level, increased loading from increased dam water level, and a sudden increase in fluid pore pressure in a section of the dam wall. The results suggest that this relatively inexpensive method can be used to monitor and locate small changes in the interior of the tailings dam wall, providing a valuable tool to remotely monitor the structural stability of tailings dam walls over time.

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