Enhancing the safety and surveillance of tailings storage facilities in cold climates

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

University of Oulu, Linnanmaa, auditorium L10

Topic of the dissertation

Enhancing the safety and surveillance of tailings storage facilities in cold climates

Doctoral candidate

Master of Science Anne Tuomela

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Civil Engineering (CIV) Research Unit

Subject of study

Civil Engineering

Opponent

Professor Leena Korkiala-Tanttu, Aalto University

Custos

Professor Rauno Heikkilä, University of Oulu

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Enhancing the safety and surveillance of tailings storage facilities in cold climates

The mining industry, both in Finland and worldwide, generates a lot of unused by-products. One of the most significant by-products is tailings, Tailings is a generic term for material that is formed as a surplus in the enrichment process when the most economically viable compounds, such as precious metals, have been separated from ore.

Sustainable mining aims to reduce the load on the environment and find ways to exploit the materials of the side streams. However, northern conditions, such as the presence of snow and ice, create their own challenges for exploitation.

The doctoral dissertation investigated the behaviour of tailings in cold climate areas. The study analysed how tailings from metal ore mines freeze and how their disposal can be improved from a geotechnical perspective. The examined tailings samples behaved like natural materials during freezing, and the frost-susceptible classifications developed for natural materials were suitable for use in the tailings studied as well. In one tailings storage facility (TSF), the penetration of frost in the tailings pond was measured over the winter. The functionality of the one-dimensional simulation model was verified with the help of the measurement results. The model can be used to assess, for example, a disposal method’s risk of generating permafrost layers in a pond. In addition, a method was developed to select an appropriate test method for estimating the frost susceptibility of mine tailings.

The use of drones was also tested in several ways. In this work, unmanned aerial vehicle measurements were used to monitor changes in a tailings storage facility at one of the mines from 2015 to 2017. Drones were found to be a practical tool for monitoring and collecting tailings surface elevation data with an accuracy of about a decimetre. Surface maps generated from the data were useful for tracking settlements and patterns. The method was found to have several possibilities and can be used in the future, for example, in planning, designing, and dimensioning of TSFs and managing the filling during the use of facilities.

In addition, the study collected information from the literature on composite structures used in the bottom of tailings ponds, which in Finland have attracted much debate because of leaks. According to the previous research, high-quality foundation structures reduce leakages into the environment. In this study, a framework of action was developed to improve the construction process by designing the most qualitatively functional structures. The results obtained in this dissertation can be used extensively in the mining industry.
Last updated: 6.6.2022