2018 SME Annual Conference & Expo and 91st Annual Meeting of the SME-MN Section

February 25 -25, 2018

The 2018 SME Annual Conference & Expo and 91st Annual Meeting of the SME-MN Section provides a forum for more than 6,000 industry professionals from across the world to share innovative ideas, best practices and cutting-edge research in more than 120 technical sessions along with an expansive marketplace of more than 550 exhibiting companies. This combination is a unique opportunity for you to hear from and interact with these leaders as you work to put the tools and initiatives in place that will enable you to adapt to this new reality.

Itascan Technical Papers & Presentations

A Strategic Rock Mechanics Study for the Kevitsa Open Pit Mine

J. Sjöberg1, J. Switala1, R. Ortiz2, A. Bergman3 and P. Bergström4
1Itasca Consultants AB, Luleå, Sweden; 2Itasca S.A., Santiago de Chile, Chile; 3Boliden, Boliden, Sweden and 4Boliden Kevitsa, Petkula, Finland

Tuesday, February 27, 9:45 am, Room 101A, Mining & Exploration: Geology: Open Pit Design Geology

The Boliden Kevitsa open pit mine in northern Finland is currently revising its strategic plan. A new pit optimization project is undertaken to investigate an increase in production. In conjunction with this, the geotechnical slope design parameters for the final pit depth, including a possibly deeper pit, need to be analyzed. This paper presents the assessment of slope stability for future open pit mining at Kevitsa for all scales — from benches to over-all slopes, including: (i) total slope angles for final pit depths, (ii) interramp slope angles, (iii) maximum interramp height, (iv) bench slope geometries, (v) recommendations on slope depressurization, and (vi) recommendations for slope monitoring and further data collection. The paper demonstrates the current state-of-the-art for both large-scale stability analysis (2D and 3D modeling) and kinematic analysis for benches and interramp slopes, incorporating acquired experiences and knowledge from large open pits world-wide. For the bench and interramp slopes, a combined analysis considering spill length, catchment criteria, and kinematic stability was conducted, and validated against the as-built geometry of the current pit.

Limits to Underground Mining at Depth

C. Fairhurst
Itasca Consulting Group

Tuesday, February 27, 10:25 am, AUDITORIUM ROOM 1, MPD: Comminution

Hostile environmental and ground control conditions are key factors limiting the depth of underground mines. Development of autonomous mining systems increases worker safety, and places greater focus on ground control. Recent innovations in numerical modeling of (i) mining in fractured rock under high stress conditions; (ii) rock fragmentation; and ongoing developments in high speed computing provide new practical tools for better assessment of ground control, and innovation in rock excavation systems. The paper will provide practical examples of these innovations. Greater commitment to Research and Development in Mining by industry is essential to achieve maximum practical benefit to be realized.

Mining & Exploration: Operations: Bridging the Chasm: Successful Implementation of Applied Research in Mining

J. Vatcher1, S. McKinnon2, J. Sjöberg1 and J. Töyrä3
1Itasca Consultants AB, Luleå, Select One, Sweden; 2Queen’s University, Kingston, ON, Canada and 3LKAB, Kiruna, Sweden

Tuesday, February 27, 2:45 pm, Room 101B, Mining & Exploration: Operations: Bridging the Chasm: Successful Implementation of Applied Research in Mining

A fundamental change in assumptions about mine-scale rock mass behaviour at Luossavaara-Kiirunavaara AB’s (LKAB) Kiirunavaara Mine has occurred as a result of recent research. This new understanding is important to future production at the mine, through enabling increased safety via informed engineering design. Initially, mine-scale faults were hypothesised to be the root cause of seismicity near production, so called “fault slip” events. Historic analyses, in particular of the mine’s seismic data, supported this hypothesis. As research progressed, however, this plausible and relatively common hypothesis was overthrown in the light from methodologies and techniques developed to evaluate conventional and unconventional data related to the rock mass. Results showed the mine-scale importance of a geomechanical characteristic that was previously overlooked, clay alteration. This paradigm shift in the understanding of the rock mass provides an obligatory foundation for future rock mechanics analyses related to planned production at the Kiirunavaara Mine.

Impact of Shear Stresses on Pillar Strength

T. Garza-Cruz1 and M. Pierce2
1Itasca Consulting Group, Inc., Minneapolis, MN and 2Pierce Engineering, Minneapolis, MN

Tuesday, February 27, 4:25 pm, Room 101B, Mining & Exploration: Operations: Bridging the Chasm: Successful Implementation of Applied Research in Mining

Empirical pillar design methods assume that pillar capacity and demand are directly a function of its width-to-height ratio, rock mass strength, overburden thickness and the pillar’s tributary area. While this assumption is generally valid for pillars in flat seams underneath a flat topography, it is not for cases in which the pillars are to be subjected to shear stresses arising from dipping seams or in-situ stress rotations (i.e. due to mountainous terrain). This paper describes the detrimental effect shear stresses arising from non-vertical pillar loading have on reducing pillar confinement and, as a consequence, pillar load carrying capacity. A series of pillars with different width-to-height ratios were modeled using the bonded block model approach in 3DEC and loaded under varying normal and shear stress conditions to gain insight into the pillar damage condition (i.e. spalling) and ultimate strength as a function of such stress demand. The results are presented as a series of normalized charts.

Determination of Properties of a Geological Fault Through Back Analysis Using 3D Numerical Modeling

L. Lorig
Itasca, Minneapolis, MN

Wednesday, February 28, 9:45 am, Room 101A, Mining & Exploration: Geology: Mining Geotechnical I

Numerical modeling has become a powerful tool for stability assessment of planned mining situations, etc. However, reliability of the outcome lies on appropriate input, including properties of the rock mass and those of major geological weak planes. In recent years, many tools have been introduced to convert laboratory scale rock properties to rock mass scale. However, obtaining properties of the geological faults has been a challenge. For making robust pit slope designs, the role of geological structures cannot be ignored as it may lead to not only serious interruption in business plans but severe safety threats also. One way of acquiring properties of geological faults is through three-dimension back-analysis of some instability events through numerical modeling. In this line, a fault triggered instability at Rampura Agucha Mine has been back-analyzed to acquire its properties using 3DEC software. For model calibration, two benchmark events- (a) crack generation at the slope crest and recording of the movement by a set of 15 prisms and, (b) extent of failure predicted by radar and that observed in field are matched with those predicted by the model.

VENUE

Minneapolis Convention Center
1301 2nd Ave. South
Minneapolis, MN 55403
United States