1. 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
David Avilés
Drill & Blasting Manager, CAP Minería – Mina Los Colorados.
FRAGBLAST August 2015
Document reference

2. 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

3. 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.

4. Los colorados Mass blast case study

5. 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.

6. 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
Separate production & trim blast. 2
Blasting entire cutback width “toe – crest”
950 Kth
850 Kth
Production
Production
Trim
Trim

7. 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.

8. 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

9. Example of mass Panel Blasting for Vibration Control

10. 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

11. 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

12. Mass blast trial 1 & 2 Measurement Results for wall control
Presplit filters reduced near field vibrations PPV % 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

13. 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

14. 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.