Annika Bjelkevik - Academia.edu (original) (raw)

Papers by Annika Bjelkevik

Proceedings of the International Conference on Mine Closure, 2011

The International Commission on Large Dams (ICOLD) is a non-governmental international organisati... more The International Commission on Large Dams (ICOLD) is a non-governmental international organisation that was established in 1928 as a forum for the exchange of knowledge and experience in dam engineering. This organisation is made up of various subcommittees, one of which is the Committee on Tailings Dams and Waste Lagoons. Formed in 1928, this subcommittee has produced a number of bulletins related to tailings dam design. The next bulletin, "Sustainable Design and Post-Closure Performance of Tailings Dams", will be published in 2011/12 for tailings dam designers intending to achieve sustainable development. Sustainable development in this paper is defined according to the Bruntland Report (UNWCED, 1987): "development that meets the needs of the present without compromising the ability of future generations to meet their own needs". This means that mining projects, including tailings management facilities (TMFs), should be financially viable, technically appropriate, environmentally sound and socially responsible (ICMM, 2008). In order to fulfil that brief, closure of TMFs need to be managed carefully. This new ICOLD Bulletin is intended to be a guide in this process. The Bulletin is compiled into three major sections, with in-depth discussion on the following:  Sustainable closure principles, covering closure objectives, closure design life, the influence of deposition methods, financial principles, regulations and risk management principles.  Sustainable design considerations, covering consequence classification at closure, long term physical stability, ecological and social stability.  Long-term monitoring: covering instrumentation and control after remediation has taken place. This paper sets out some of the guiding principles and details that will be contained in the new ICOLD bulletin.

Mining activities have been ongoing for thousands of years within Sweden. As the results of previ... more Mining activities have been ongoing for thousands of years within Sweden. As the results of previous activities are evident today, i.e. for example acid mine drainage (AMD), the focus and interest ...

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Tailings impoundments are designed and constructed for disposal of mine waste, i.e. tailings, env... more Tailings impoundments are designed and constructed for disposal of mine waste, i.e. tailings, environmentally safe in a long-term perspective. Tailings dams are raised along with a mines production ...

Sustainable and Safe Dams Around the World, 2019

Proceedings of the 11th International Conference on Mine Closure, 2016

Tailings storage facilities (TSFs) will, after closure of the mine, have to be stable in a long-t... more Tailings storage facilities (TSFs) will, after closure of the mine, have to be stable in a long-term perspective (e.g. 1,000 years or more). In many cases, due to the characteristics of the tailings, a high phreatic surface is required to keep the tailings saturated in order to prevent, or minimise, the process of oxidation. Due to this the slope stability of the embankment, or the land form slope, is critical as any material exposed to a hydraulic gradient is exposed to a load. So, the question is: Is the embankment, or landfill slope, that is exposed to a hydraulic gradient safe in the long term with respect to the actual design and material properties? In order to answer that question, an understanding of the structure, its stability and level of actual safety during operation is necessary. This paper will therefore discuss slope stability for embankments during operation and the long-term perspective and how the factor of safety (FS) can be verified. Practice today for dam stability is that a certain FS is required, i.e. a safety margin (in Sweden FS>1.5), and for that condition we design the embankment. The design includes the geometry of the structure, material properties, water management/water levels and requirements for compatibility between different materials, as well as for construction and operation. The FS can, however, not be physically measured on, or in, the actual embankment. What can be measured is seepage, pore pressure and movement (vertical and horizontal displacements). But how can the readings be used to verify the actual FS? In order to illustrate this, an example from a TSF in northern Sweden is presented where readings have been taken through numerical modelling (PLAXIS), comprehensive geotechnical investigations, lab testing and inclinometers. In order to predict how an embankment, or landform slope, will behave in the long-term phase and what the actual FS will be, the authors believe it is necessary to understand the behaviour of the structure during operation. The method used for the example illustrated in this paper shows a method to gain an understanding for a structure, which is absolutely crucial for understanding the actual FS and for the possibility to predict the level of safety in the long term.

When a mine comes to an end and the operation closes down the whole site will be abandoned. Thus ... more When a mine comes to an end and the operation closes down the whole site will be abandoned. Thus there is a need for remediation of the tailings storage facility (TSF), where the fine (crushed and ...

Proceedings of the International Conference on Mine Closure, 2008

Fäboliden is a planned new Swedish goldmine, owned by Lappland Goldminers AB. A permit granting c... more Fäboliden is a planned new Swedish goldmine, owned by Lappland Goldminers AB. A permit granting commencement of operations was issued in December 2007, but was subsequently appealed by the Swedish Environmental Protection Agency and some stakeholders in January 2008. New Supreme Court negotiations took place in May 2008. Some of the main issues during negotiations, and the reasons that the Swedish Protection Agency appealed the granting of the permit, are related to closure and financial security for remediation works. Other issues during negotiations, and the reasons for appeal by some stakeholders, are related to the operation itself. These latter issues, however, are not dealt with in this paper. This paper describes design issues, and the design process for this new mine, with a focus on closure. This includes the objectives of the company (Lappland Goldminers AB), requirements of the authorities, and the philosophy regarding mine closure in Sweden. The focus on closure of mining operations, and specifically tailings facilities, has increased during the last decade. Experience and research have not progressed at the same rate, resulting in some issues remaining in a "Catch 22" situation. Using Fäboliden as an example, this paper summarizes the issues requiring further attention in the field of mine closure and remediation of tailings facilities in order to increase knowledge and experience regarding long-term (more than 1000 years) development of these facilities. One of these issues is the long-term stability of tailings dams. Developments in fields relating to this issue are important for existing and new mines, not just in Sweden, but for the mining industry as a whole, where remediation incorporates water cover or residual high hydraulic gradients within the tailings dams. This paper discusses the most important design issues for tailings dams, with a focus on closure as well as the process of developing the design of Fäboliden. This includes the objectives of the company (Lappland Goldminers AB), requirements of the authorities, and the philosophy regarding closure in Sweden. The focus on closure of mining operations, and specifically of tailings facilities, has increased during the last decade. Experience and research have, however, not progressed at the same rate, resulting in some issues remaining in a "Catch 22" situation. Specific fields of research are therefore discussed. 2 Definitions The most important definition for this paper is that of long-term. In a philosophical context in Sweden, the phrase long-term closure of tailings facilities means permanent or at least to the next glacial period, which will take place in approximately 10,000 years. However, a time period that is practically manageable, and in line with the practice in many other countries, is defined as 1000 years. https://papers.acg.uwa.edu.au/p/852_27_Bjelkevik/

Mining operations produce huge volumes of waste products. Tailings, the fine grained waste materi... more Mining operations produce huge volumes of waste products. Tailings, the fine grained waste material, is often managed in tailings management facilities (TMFs) surrounded by dam structures, i.e. tai ...

Swedish tailings : comparison of mechanical properties between tailings and natural geological ma... more Swedish tailings : comparison of mechanical properties between tailings and natural geological materials

Managing tailings facilities often includes stability and deformation analyses from both short- a... more Managing tailings facilities often includes stability and deformation analyses from both short- and longterm perspectives. Behind these analyses, geotechnical theories are applied on the studied material. Design for closure is often considered to cover a period of 1,000 years, during which time the closed tailings facility should be stable, both physically and environmentally. Since the use of tailings facilities only covers about 100 years back in time, there are still no data on how tailings behave in the long term. In Sweden, correlations to natural formations have been used to predict the long-term stability of tailings dams. Natural formations that have been stable since the latest ice age (approximately 10,000 years ago) are considered good examples of long-term stability. These are mainly formed by glacial till, a natural material that has been subject to erosion, transportation, and sedimentation processes. Tailings material, however, is artificially created and differs in s...

Tailings dams are necessary for efficient mineral and metal production and need therefore to be c... more Tailings dams are necessary for efficient mineral and metal production and need therefore to be constructed, operated, maintained and closed in a safe and acceptable manner. In this context “safe and acceptable” means a level agreed upon by all stakeholders. It is prudent to assess the causes of past incidents and failures, learn from the experiences and apply this knowledge to current and future operations (Strachan 2002). Trial and error have been used to improve and develop technology throughout history, but to learn from the experience and make use of the knowledge is today often underestimated or forgotten. This paper therefore intends to improve the knowledge of tailings dams safety by investigating the history of events (failures, incidents and event driven maintenance) at Swedish tailings dams. This will be of value not only for Swedish and international mining companies, but also for the county administration, consultants and contractors working within Sweden as well as int...

Electronic Journal of Geotechnical Engineering

A curved embankment (corner) of an upstream tailings dam was analyzed with the finite element met... more A curved embankment (corner) of an upstream tailings dam was analyzed with the finite element method to identify possible zones of low compressive stresses susceptible to hydraulic fracturing that might initiate internal erosion. The embankment was also analyzed as a straight section, with the same cross section as in the corner, in order to compare compressive stresses in the corner and the straight section. The analysis showed that in comparison to the straight section of the dam, the compressive stresses in the corner were (i) much lower above the phreatic level, in the rockfill banks and the filter zones, and (ii) fairly lower below the phreatic level. The rockfill and the filter contain coarse materials, which are not sensitive to hydraulic fracturing and internal erosion. An increase in radius of the corner is proposed to avoid too low compressive stresses that may develop due to future raisings. The slope stability analysis showed that the corner is currently stable, but an additional rock fill bank on the downstream toe is required for future raisings.

Canadian Geotechnical Journal, 2013

The consolidation process could be slow in an upstream tailings dam; therefore, the stability can... more The consolidation process could be slow in an upstream tailings dam; therefore, the stability can reduce due to an increase in excess pore pressures when the dam is raised. The safety of the dam can be enhanced by constructing rockfill berms on the downstream side. This paper presents a case study on the strengthening of an upstream tailings dam with rockfill berms. The finite element analyses were performed for modelling the staged construction of the dam and for optimizing the volume of the rockfill berms. The dam was raised in 11 stages; each stage consisting of a raising phase and a consolidation phase. The study shows that the slope stability of the dam reduced due to an increase of excess pore pressures during the raising phase. The stability of the dam was successfully improved by utilizing rockfill berms as supports on the downstream side. A technique has been presented to minimize the volume of the rockfill berms so that the required stability can be achieved at minimum cos...

Proceedings of the 14th International Conference on Mine Closure, 2021

Mining operations have a big environmental impact wherever they are located. Unsuccessful operati... more Mining operations have a big environmental impact wherever they are located. Unsuccessful operation and/ or inadequate planning for closure has in several cases increased the impact, causing costly environmental liabilities without finance. The consequence is, generalized, difficulties to get permits, in some countries more or less impossible. Metals and minerals are, however, necessary for our society and even more so with the “green transformation”, i.e. the change from fossil fuels to sustainable sources of energy (windmills, solar power, electrical cars etc. etc.). Mining has developed over centuries. With time, extraction processes have been refined resulting in a (still) increasing amount of waste materials, such as waste rock and tailings. The mining industry is the industry, globally, moving the largest volumes of materials. These materials are generalized a problem, a waste. Traditionally, mining operations are run by engineers using logic, “straight lines”, effective proce...