BENEFITS RELATED TO APPLICATIONS OF MASS BLAST IN OPEN CUT MINING José Vergara, Carlos Muñoz, Natalia Ortega. Advanced Technology Solutions, Orica Mining Services – Latin America jose.vergara@orica.com, carlos.munoz@orica.com, natalia.ortega@orica.com, David Avilés Drill & Blasting Manager, CAP Minería – Mina Los Colorados. daviles@cmp.cl FRAGBLAST 24 - 26 August 2015 Document reference

Mass blast concept Traditional Blast Mass Blast Traditional Blast Blasting Production with a seperate wall control blast. Mass Blast Blasting entire bench cutback width “toe – crest”. Traditional Blast Mass Blast Mass Blast

Mass blast concept Mass Blast influences on increasing productivity: Reduced number of blast events. Reduced damage to walls. Larger drilling and excavation areas. Reduced blast delays and evacuations. Increased excavation rates. Improved fragmentation.

Los colorados Mass blast case study

Cap Los colorados CAP Los Colorados: Kiruna Iron Ore Deposit in the Atacama Region of Northern Chile. 84 Mtons/Year open-cut operation producing 10.4 Mton Iron Ore (Magnetite). Explicar dondfe está ubicada mina Los Colorados y aspectos generales.

Mass blast TECHNICAL SOLUTIONS Both trials were designed, fired and monitored using: Computer based blast design, sequencing and advanced finite vibration prediction modeling. Near field vibration monitoring. Software for electronic programming unique timing hole by hole. Bore Hole Camera inspection of rock mass before and after blasts. Trial Tonnes Description 1 850.000 Separate production & trim blast. 2 950.000 Blasting entire cutback width “toe – crest” 950 Kth 850 Kth Production Production Trim Trim

Mass blast Vibration prediction modelling Traditional Blasts High impact in the rock mass, generated cracking in the failure zones. Exceeds the tensile strength of the intact rock. Mass blast Mass blast does not generates new fractures in the failure zones.  Traditional Blast Mass blast The model doesn’t necesary represnts the reality, nevertheless works to compare the levels of strain generated with the 2 types of blasts. Traditional blasting, specially Wall Control, do not have breaks and also do not have the sufficient width to manage vibrations, the impact in the rock is high because exceeds the tensional resistance of the intact rock. The blast that occupies the width of the bench, considering rests, is easier to orientate the trainwave so the level of strain do not exceeds the resistance of the intact rock.

technical solutions timing design for geotechnical factors Bench Presplit Presplit fired 1000 ms prior to initiating combined production and trim blast. Timing design applied 500ms “breaks” in blasting sequence to create separate panels. 300 ktonne panels used to reduce peak vibration levels. Blast sequencing is possible using specialised electronic detonator timing. Buffer Mass blast 500 ms 500 ms 500 ms Presplit Bench

Example of mass Panel Blasting for Vibration Control

technical solutions drill & blast design Trial 1 Trials design parameters: Measurement Trial 1 Trial 2 Diameter 26 cm 31 cm Bench height 15 m 16 m Burden 7.5 m Spacing 10.5 m Charge factor 200 gr/tonne Total Energy 3.53 MJ/tonne Bulk Product Fortan Extra 50 Priming per hole 3 x EBS 3 X EBS Trial 2

Mass blast trials 1 & 2 wall control Measurement Method Application of presplit and buffer row. Maintained the trim blast to a width of 35m. Nearfield vibration monitoring (GT, GT2) with disposable triaxial geophones. Borehole camera inspections for near-field damage (BH1, BH2, BH3, …, BH9). To Blast GT Presplit Important to note how monitoring was conducted before and after presplit Borehole Inspection Holes Borehole Inspection Holes GT2 Wall

Mass blast trial 1 & 2 Measurement Results for wall control Presplit filters reduced near field vibrations PPV 47 - 50% before and after presplit. Borehole camera inspections indicated no damage inside all monitoring holes. PPV in front of presplit PPV behind presplit BH 6 (10m) Before mass blast BH 6 (10m) After mass blast 12

Mass blast trial 1 & 2 fragmentation results Photo Image Analysis of Free Face for Trial Blasts. Fragmentation image analysis demonstration decrease of the P80. P80 (inch) Baseline 7.4 Trial 1 6.6 Trial 2 6.9

conclusions Mass blasts demonstrated increasing from 300 up to 950 ktonnes possible without increasing damage to walls. Mass blasts maintained near field PPV 500 mms/sec meeting geotech design limit of 720 mm/sec while improving fragmentation versus baseline. Pre and post borehole examinations demonstrated no difference in damage behind presplit line. Mass blasts replaced up to three or more traditional blasts increasing productivity in mine. Mine avoided losing service guarantees on Shovels due to excessive repositioning for blasts. Industry standard practice of separating production and trim blasts determined not to be required – was phased out of standard practice for mine. Mine operation estimates total benefits for mass blast technique over US $ 2,000,000 per annum after D&B costs due to increased productivity.