LICENTIATE T H E SIS Department of Civil, Environmental and Natural Resources Engineering Division of Mining and Geotechnical Engineering ISSN 1402-1757 Mine at the Kiirunavaara Mine-scale Rock Mass Behaviour Vatcher Jessica Mine-scale Rock Mass Behaviour ISBN 978-91-7583-365-1 (print) ISBN 978-91-7583-366-8 (pdf) at the Kiirunavaara Mine Luleå University of Technology 2015 Jessica Vatcher LICENTIATE THESIS MineǦscaleRockMassBehaviouratthe KiirunavaaraMine Jessa Vatcher Luleå University of Technology Printed by Luleå University of Technology, Graphic Production 2015 ISSN 1402-1757 ISBN 978-91-7583-365-1 (print) ISBN 978-91-7583-366-8 (pdf) Luleå 2015 www.ltu.se Prefaceandacknowledgements The work presented in this Licentiate thesis was carried out as part of a larger Doctor of Philosophy project at the Division of Mining and Geotechnical Engineering at the Luleå University of Technology (LTU). Generous financial support of this project has been provided by 1) Luossavaara-Kiirunavaara Aktiebolag’s (LKAB) via the Hjalmar Lundbohm Research Centre (HLRC) fund, and 2) the Centre of Advanced Mining Metallurgy (CAMM) at LTU. A significant reason for the success of this work can be attributed to my supervisors, Professor Steve McKinnon (Queen’s University, Kingston, Canada and LTU) and Adjunct Professor Jonny Sjöberg (Itasca Consultants AB, Luleå, Sweden and LTU). I am exceptionally grateful for their technical input, revisions, guidance, humour, and friendship. Steve’s large dreams and wide perspective provide me with much inspiration and courage. Jonny’s attention to detail and enthusiasm about interesting results encourages me to take my work to a higher standard. I am thankful for Ms. Christina Dahnér (LKAB) in her many roles associated with this project; as a fellow doctoral student, as a member of the Project Group working on understanding the seismicity at the Kiirunavaara Mine, and as my mine contact. Her time, dedication and expertise have greatly improved these research efforts. Her commitment to quality data has improved not only our respective Ph.D. projects, but many more projects to come in the future. Tack Christina! My gratitude is extended to the remaining two members of the Project Group, Professor Savka Dineva (LTU) and Dr. Björn Lund (Uppsala University). Their insightful contributions to discussions encourage all of us to think beyond our respective disciplines. For their technical contributions, project management advice, and perspective from the Kiirunavaara Mine, I thank the members of the Steering and Reference Group. Individuals in this group from LKAB include: Dr. Lars Malmgren, Mr. Jimmy Töyrä (Tech. Lic.), Dr. Carlos Quinteiro, Mr. Stig Fjellborg, and Dr. Ulf B. Andersson (Docent). I appreciate how questions from the mine’s perspective fueled this research. Individuals in this group from LTU include: Prof. Erling Nordlund (formerly active in the group), and Dr. Ping Zhang (currently active in the group). I am particularly indebted to Mr. Jimmy Töyrä. As an LKAB employee, Jimmy has promptly reviewed all works written and presentations related to this work intended for public eyes. Most often, on incredibly short notice. Despite this, he i has always managed to provide useful, constructive, and thoughtful feedback. Tack Jimmy! For additional discussion and access to data external to the Steering and Reference Group meetings, I offer my sincerest thanks to Dr. Ulf B. Andersson. His insightful and lively discussions about geology and underground visits have been invaluable to me. Ulf also generously provided me with much exercise running around the badminton court. Tack Ulf! Particular thanks must be given to Dr. Henrikki Rutanen, who has kindly updated my geological data numerous times, offered many insightful discussions, and given this project a significant amount of space on the core logging table, not to mention in the warehouse. I am also grateful for Henrikki’s friendship and support. Tack Henrikki! There are several people without whom this work would not have been possible. For their assistance with data access and acquisition, thought provoking discussions, site visits, friendship, and acceptance of my unique Swedish dialect I am grateful. These individuals include (LKAB unless otherwise indicated): Ms. Mirjana Boškoviü, Ms. Helena Sturk, Ms. Britt- Marie Stöckel, Ms. Karola Mäkitaavola, Ms. Karin Lindgren, Ms. Stina Hallinder, Ms. Anousheh Abdollahpour, Dr. Johan Berglund (Vattenfall), Mr. Tomas Björnell (Norconsult), Mr. Håkan Krekula, Mr. Åke Öhrn, Mr. Sakari Liikavainio, Mr. Mikael Bohm, and Mr. Ville Törnman. I offer many words of thanks to my colleagues at LTU in the Division of Mining and Geotechnical Engineering. I appreciate their support and interest in this work. I look forward to continuing our careers together. In particular I wish to thank Mr. Mikael Svartsjaern (Tech. Lic.) and Mr. Sraj Banda Umar (Tech. Lic.) for their willingness and eagerness to discuss strategies to better our research. I also wish to acknowledge the support and friendship of the employees at Itasca Consultants AB in Sweden. Through many discussions they have helped both with this work and my own professional development. I appreciate that they’re always happy to lend a listening ear to my over-enthusiastic discussion of algorithms and automation. Specifically, I wish to thank Mr. Fredrik Perman, Mr. Ulf Lindfors (Tech. Lic.), Mr. Erik Storvall, Dr. Diego Mas Ivars, Mr. Abel Sánchez Juncal (now with University of Alberta), and Mr. Axel Bolin. / Jessa Vatcher Luleå, May 2015 ii Publicationsformingthebasisofthisthesis This manuscript is a synthesis of the following three articles. These articles are a product of the research completed by Jessa Vatcher, the author. All analysis was executed by Jessa. All content was written by Jessa. Co-authors of the papers contributed in the form of scientific and editorial feedback. The articles are appended to the end of this manuscript. Paper I: Vatcher J, McKinnon SD, Sjöberg J and Dahnér C (2014) Modelling methodology: structural geology and rock mass behaviour at Kiirunavaara Mine. Rock Engineering and Rock Mechanicsࣟ: Structures in and on Rock Masses. The 2014 ISRM European Rock Mechanics Symposium (Eurock 2014). Vigo, Spain: CRC Press, 643–648. Paper II: Vatcher J, McKinnon SD and Sjöberg J (2014) Mine-scale numerical modelling, seismicity and stresses at Kiirunavaara Mine, Sweden. In: Hudyma MR and Potvin Y (eds) Proceedings of the Seventh International Conference on Deep and High Stress Mining. Deep Mining 2014. Sudbury, Canada: ACG, 363–376. Paper III: Vatcher J, McKinnon SD and Sjöberg J (2015) Developing 3-D mine-scale geomechanical models in complex geological environments, as applied to the Kiirunavaara Mine. Submitted to an international scientific journal. iii iv Summary The interaction of the geological and mining environments leads to a variety of forms of rock mass behaviour, including seismicity and falls of ground. A precise understanding, however, of the role of geology in rock mass behaviour experienced by Luossavaara-Kiirunavaara Aktiebolag’s (LKAB) Kiirunavaara Mine remains unknown. Since late 2008, the sublevel caving mine regularly experiences induced seismicity (Dahnér et al., 2012). Seismic events occur in the footwall, orebody, and hangingwall. Instabilities, sometimes related to specific seismic events, are unevenly distributed throughout the rock mass. Failure mechanisms of these instabilities include structurally controlled failure (sometimes as shake down), strainbursting and spalling, which are typically a result of local stress changes. Occasionally, these falls of ground are rockbursts; violent ejections of rock causing damage to infrastructure and/or personnel that are caused by remote seismic events. Some previous work has been done at the Kiirunavaara Mine for both specific events and specific volumes to better understand the rock mass behaviour (see e.g., Sjöberg et al., 2011, 2012). However, the causes of the uneven distribution of both seismicity and instabilities at the mine are not understood, particularly at the mine-scale. As part of a larger Ph.D. project, this study explores the role of geology in the mine-scale behaviour at the Kiirunavaara Mine. This is done through two approaches: 1) exploratory numerical stress modelling, and 2) development of a geomechanical model of the rock mass. The exploratory numerical modelling of the mine evaluated common assumptions made by researchers and consultants when completing numerical stress modelling of this orebody. A previously estimated virgin in situ stress state was applied in a 3-D model developed of the nearly 5 km long orebody and surrounding host rock. The model had definition between footwall, ore and hangingwall materials. Run as a continuum for this analysis, the stresses from the elastic and perfectly plastic models corresponded to stresses recently measured in situ at two sites using overcoring, indicating that the estimated virgin stress state is consistent at depth. Alternating two commonly used perfectly plastic material properties for the footwall significantly influenced the location of plastic failure throughout the rock mass, including in the hangingwall. A physical alignment of plastic failure from the models and mine v seismicity for the entire rock mass was not found for the plastic properties evaluated. Large magnitude shear events tended to be external to plastic failure. The difficulties relating plastic failure to seismicity can be associated with a number