Draw Control Optimization along the Production Drift in Sublevel Caving Mines Shekhar, G.(1), Gustafson, A. (1), Boeg-Jensen, P. (2) and Schunnesson, H. (1) 1. Luleå University of Technology, (Division of Mining and Geotechnical Engineering), Sweden. 2. LKAB, LKAB Kiruna, Sweden. Improved resource efficiency through dynamic loading control, is a joint project between Luleå University of Technology, LKAB, ABB, Boliden Mineral AB and Agio System och Kompetens AB Division of Mining & Geotechnical Engineering Lulea University of Technology Research Areas: Mining & Rock Engineering Kiirunavaara mine, LKAB Largest underground iron ore mine Introduction Mine design Grade calculations Model Results Conclusions Loading process in SLC Courtesy LKAB Loading process in SLC Continuous mixing of ore and waste Courtesy LKAB Loading process in SLC Continuous mixing of ore and waste Flow of material from a restricted opening Courtesy LKAB Draw control regulates loading process Draw control regulates loading process Amount of material to be loaded Draw control regulates loading process Amount of material to be loaded When to stop loading Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Ore grade Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Ore grade Research focus Factors Draw control Optimization Parameters Ore geometry and geology Ore grade Mine design and layout Final extraction ratio Research focus Factors Draw control Optimization Ore geometry and geology Mine design and layout Parameters Ore grade πππ‘ππ πππ‘πππππ ππππππ πππππππ π‘ππππππ Final extraction ratio Introduction Mine design Grade calculations Model Results Conclusions Kiirunavaara mine- a typical ring Silo shaped ring Kiirunavaara mine- a typical ring Hole length: 22m-52m Side angle: 73° Borehole diameter: 4.5 inch (115mm) Hole length Side angle Simplified diagram of Kiirunavaara ore body Production drift Drill design variation Drill design variation Horizontal section for first blast Drill design variation Drill design variation Better fragmentation in transition zone Drill design variation Cave breach point Cave breach ring Drill design variation Cave breach point Cave breach ring Drill design variation Cave breach point Cave breach ring Drill design variation Cave breach point Cave breach ring Drill design variation Cave breach point Cave breach ring Bucket weight LHD bucket arm cylinder Pressure transducer Bucket weight LHD bucket arm cylinder Pressure transducer Hydraulic pressure Bucket weight Bucket grade Principle for grade calculation at Kiirunavaara mine: Iron ore (4.6 t/m3 ) has a higher density than waste (2.7 t/m3 ) Bucket grade Inputs : οFully filled bucket with waste οFully filled bucket with ore Principal graph Bucket grade 47,733 sample points Inputs : οFully filled bucket with waste οFully filled bucket with ore Principal graph Bucket grade Bucket weight (t) Bucket grade (Fe% Or waste%) WOLIS - Wireless Online Information System (LKAB) Ore grade plotted against extraction ratio Introduction Mine design Grade calculations Model Results Conclusions Grades used for analysis Average grade Moving average grade (last 20 buckets) Grades used for analysis Average grade Overall ore grade of a production ring Moving average grade (last 20 buckets) Grades used for analysis Average grade Overall ore grade of a production ring Moving average grade (last 20 buckets) Ore grade of the material being loaded Introduction Mine design Grade calculations Model Results Conclusions Proposed model for zonal division Proposed model for zonal division Zone 1 Rings not connecting with cave Safety loading Proposed model for zonal division Zone 2 Rings with ore recovery potential Proposed model for zonal division Zone 3 Normal rings Proposed model for zonal division Zone 4 Rings with internal dilution Total number of rings = 5903 Percentage of rings in each zone 9% Zone 1 (near Hanging wall) 28% Zone 2 36% Zone 3 27% Zone 4 (near Footwall) Draw point distribution Model assumptions Average mine grade 45% Model assumptions Average mine grade 45% Model assumptions Average mine grade 45% Model assumptions Shut-off grade 30% Model assumptions Shut-off grade 30% Model assumptions Shut-off grade 30% Ideal draw point performance Introduction Mine design Grade calculations Model Results Conclusions Zone 2 - 1379 production rings Zone 2 - 1379 production rings Zone 2 - 1379 production rings Percentage of total rings in Zone 2 Zone 2 - 1379 production rings Percentage of total rings in Zone 2 having ο average grade between 35% to 55% ο Grade when ring was closed less than 30% Comparison between zones Zone 2 Zone 3 Zone 2 Zone 3 Zone 2 Zone 3 Controlling early closing of rings reduced ore loss Introduction Mine design Grade calculations Model Results Conclusions Conclusions 1. Average grade of a ring must be considered along with shut-off grade Conclusions 1. Average grade of a ring must be considered along with shut-off grade 2. Zone 2 & Zone 4 has potential to increase ore recovery Conclusions 1. Average grade of a ring must be considered along with shut-off grade 2. Zone 2 & Zone 4 has potential to increase ore recovery 3. Using real time data for efficient decision making at LKAB ACKNOWLEDGMENT LKAB are gratefully acknowledged for financial support of this project. Thanks are due to the staff and management of the Kiirunavaara and Malmberget mine for their support and valuable inputs to the study. Agio System och Kompetens AB, Boliden Mineral AB and ABB are acknowledged for valuable input to the project. Vinnova, The Swedish Energy Agency and Formas are acknowledged for financing this project through the SIP-STRIM program. Thanks Grades calculation for analysis Average grade Moving average grade (last 20 buckets) π π=1 πΊπ Aπ£πππππ πππππ = π Gi = Bucket grade n = Number of buckets loaded from a ring Grades calculation for analysis Average grade Moving average grade (last 20 buckets) πππ£πππ ππ£πππππ πππππ(πππ π‘ 20 ππ’ππππ‘π ) = m = mth bucket loaded from a ring G (m-i) = Bucket grade for bucket number (m-i) 19 π=0 πΊ(πβπ) 20 Draw control strategy Increase ore recovery Improve safety Objective Minimize costs Minimize dilution Factors influencing draw control Material flow Mine design & layout Ore geology and geometry Proximate draw points Production planning Draw control Cut-off & shutoff grades Dilution behavior Factors influencing draw control Material flow Mine design & layout Ore geology and geometry Proximate draw points Production planning Draw control Cut-off & shutoff grades Dilution behavior Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Brow width Width Height Ore grade Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues πππ‘ππ πππ‘πππππ ππππππ πππππππ π‘ππππππ Fragmentation Ore grade Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Hang-ups, brow failure etc. Ore grade Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Assessment via image analysis, material sieving method & boulder count method Ore grade Draw point performance parameters Draw point dimension Final extraction ratio Loading stoppage issues Fragmentation Iron % in the material loaded Ore grade Model Target for a ring β’ Final extraction ratio target β 105% β’ Average grade between 35% Fe to 55% Fe to achieve an overall mine average grade target of 45% Fe β’ Moving average grade between 30% Fe to 45% Fe to maintain the shut-off grade target for a given draw point of not less than 30% Fe. Introduction SLC at Kiirunavaara Mine Methodology Model Results Zone 1 β Draw point distribution (%) (Near Hanging Wall) Many rings were closed early causing ore loss Introduction SLC at Kiirunavaara Mine Methodology Model Results Zone 2 β Draw point distribution (%) Reduced ore loss Potential for ore recovery from upper levels Introduction SLC at Kiirunavaara Mine Methodology Model Results Zone 3 β Draw point distribution (%) Efficient loading Timely closing of Draw points Introduction SLC at Kiirunavaara Mine Methodology Model Results Zone 4 β Draw point distribution (%) (Near Footwall) Potential for ore recovery Balance Overloading is a prevalent problem Special loading conditions Near hanging wall Poor performing rings Near footwall Safety Loading issues Ore recovery No loading in open cavern Stop loading Higher extraction ratio targets
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