Tailings dam risk reduction using accurate pore pressure monitoring (2020)

Dr Kym L Morton
KLM Consulting services Pty Ltd

Abstract
The January 2019 Brumadinho tailings dam failure in Brazil which killed over 250 people has created
worldwide focus on what can be done to reduce tailings dam failures. South Africa has had its own
tailings dam failures; notably the Merriespruit failure in Virginia in 1994, where 17 people were
killed and many houses destroyed.
Modern techniques for tailings dam monitoring emphasise the measurement of movement of the
slopes using radar, LIDAR and prisms; however these techniques only measure the reaction of slopes
to instability factors and do not address the causes or assist with reducing risk.
The biggest preventable cause of slope failure is too much water, either in the pond or from the
weight (measured as pressure) of water in the tailings slope faces. Pore pressure monitoring is an
accurate method to measure the weight of water in a slope and enables early intervention to delay
or prevent failure. Pore pressure monitoring methodology and techniques are described with
recommendations on a standardised but bespoke monitoring network for each high risk tailings
dam.
The mechanisms of failure are discussed and the best practice for monitoring required to predict
failure is presented. Open pit slope stability techniques can be used to manage dam wall stability.
The success of accurate monitoring design depends on the location, construction and management
strategy for a tailings storage facility (TSF). Different monitoring networks are required depending on
the type of dam and the impact of the catchment on its water balance.
Pore pressure monitoring is proposed as an effective method to predict instability as it addresses the
cause of the potential failure. Big Data techniques are now available to manage multi-point
monitoring sites and telemetry can transmit real-time information which can then be depicted in a
dashboard to present knowledge and identify risk. This can be used to prevent failures and act as
early warning systems for those that cannot be prevented. An example of a monitoring network,
installation and reporting is given including recommendations for implementation and transmission
of real-time information linked to action.

Morton, K.L. (2020) ‘Tailings dam risk reduction using accurate pore pressure monitoring’, SAIMM Tailings Conference, Johannesburg, 10–13 February 2020.