The mining world has been inundated with statistics outlining the horrific events we’ve seen from tailings dam failures. Vale’s Brumadinho (2019) and Mariana (2015) dam disasters have been in the press again recently after the mining giant agreed to pay US$ 6.8 billion to help repair the environmental and social damages from the Brumadinho dam failure that killed almost 300 people and released around 12 million cubic meters of tailings into the nearby communities.
What’s worse about these tailings dam failures – and others like them – is that they are completely avoidable. Tailings storage is an essential component to safe mining practices making the safe construction and monitoring of tailings dams critical to the industry. To keep tailings dams safe requires a comprehensive monitoring program that addresses the key reasons why tailings dams fail:
- Seepage. Tailings Dams are permeable; the extent of seepage has a direct impact on the stability of the structure. Good drainage design can help prevent leakage, but monitoring is critical.
- Foundation Failure. Tailings dams are among the largest engineered structures on earth. Instability of the foundation, or the geology surrounding the structure, can cause shifts – that produce voids – and result in unsafe structural conditions.
- Flooding. Heavy rainfall can cause the water level of a dam’s reservoir to rise above the height of the embankment increasing the risk of slope stability through erosion.
- Seismicity. Earthquakes and other seismic events can impact the stability of the tailings dam structure as well as cause liquification of the tailings sand.
As tailings dams are built to last forever – mine waste needs to be stored permanently – preventing catastrophic failure requires a comprehensive monitoring program. There is a vast range of technology available to help mining companies ensure their tailings facilities are secure – and, in the event of an issue – that they receive ample advanced warning to allow for corrective action.
- To effectively monitor the performance and safety of tailings dams, a comprehensive instrumentation program is required, that may include: piezometers for measuring pore pressures, extensometers for measuring ground deformation, inclinometers for monitoring displacement, load cells or pressure cells for monitoring tension and rain gauges and water level sensors among others to monitoring the contributing factors to potential failure.
- With an instrumentation program in place, additional more advanced monitoring is advisable to provide a more holistic view of what’s happening in the structure – a view that cannot be guaranteed via ‘point instruments’ alone. Real-time geo-resistivity monitoring has recently become possible via a new monitoring solution referred to as a Geo Resistivimeter for Time Lapse Analysis, or GReTA for short. GReTA enables the permanent geo-electric monitoring of soil conditions on a large-scale helping to detect water infiltration and voids in earthen structures.
- Other advanced technologies for monitoring tailings dams are also available, such as distributed temperature measurements via fibre optic sensing using the natural seasonal temperature variations that occur in all surface water to detect seepage along an embankment.
- Bringing the instrumentation and monitoring technologies together with a reliable persistent sensor network – wireless and battery powered – and a purpose-built software platform – to managed thresholds and alarms in real-time – completes the technology setup required to fully and safely monitor a tailings dam.
If your mine is interested in introducing a comprehensive Tailings Dam Monitoring program, please contact your nearest Ramjack Technology Solutions office for more details on how we can assist with your technology selection, your technology implementation and all your technology support requirements.