Post on 02-Jun-2018
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Asiex 2012
NEW METHOD TO OBTAIN OPTIMUM PRE-
SPLITTING DESIGN CRITERIA CONSIDERING
THE ROCK MASS PROPERTIES
Alvaro Gonzalez, Car los Muoz1, lvaro Andrades
South Region Technical Services, Orica Mining Services-LATAM1carlos.munoz@orica.com
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Wall Control is directly related to:
Sustainability
Mining Costs
Mining plans and opportunity costProductivity
Mine profitability
Why Wall Control?
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Typical Wall Control values
>15 MUSD/Year
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The influence of rock blasting in the slope stability
Pre-Split &
Buffer rows
Vibrations
& resonance in the far fiel
?!
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The influence of rock blasting in the slope stability
Typical blast damageover benches
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The influence of rock blasting in the slope stability
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The Pre-Splitting practice-An introduction
Is the most used technique in the named controlled blasting. Basically it consist in to obtain a pre-split plane that permit to
control the rock blasting damage.
To control and reduce seismic vibrations from the rockblasting.
To reduce back break and reopening of preexisting geologicalstructures.
Safety of people and equipments working around benches.
Maintain integrity of benches, final highwalls and overall pit
slope angle. To reduce bench remediation costs.
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The Pre-Splitting practices-An introduction
Pre Split design is directly related to buffer row design
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Basically the pre-split practice consist of detonates twosimultaneous de-coupled explosives charge spaced to a S distance
The detonation of the explosive charges produces a stress that it is transmitted to the rock
massif in form of shock wave and gas pressure. The last one is considered as the responsible
for the creation of the pre-split planes.
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The objectives is to obtain a pre-split plane that permit to
reduce damage related to rock blasting
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The Pre-Splitting practices-An introduction
The most used formula for to obtain the S distance between two de-coupled charges at
which the pre-split plane can be obtained is based on Sanden (1974)
Current methods consider only the static
tensile strength and a constant decay of
borehole pressure with the square of
distance.
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The Pre-Splitting practices-An introductionCurrent methods can not be scaled to rock massif
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Dynamic method for pre-splitting design
The dynamic method to pre-split design follows the work developed for Liu and Katsabanis
(1993) and Onederra et al (2004)
The pressure decay proposed by Liu and Katsabanis;
Ror
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Relation between Vp and Pre-Split Spacing
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Anlisis para un macizo fracturado con Vp < 3,000 m/s, RQD
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2.3 ton/mt
2.6 ton/mt
2.8 ton/mt
4.7 ton/mt
Mtodo canadiense
Relation between density and Pre-Split Spacing
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Current pre-spli t spacing = 2.2 m
Dymanic method=1.8-1.9 m
Application of dynamic method, case study n1
Pre-split design in argilic andesites
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BANCO 480
BANCO 495
Application of dynamic method, case study n1
BANCO 465
Case study area
Current pre-split design
Filtro de precrote 65%
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Application of dynamic method, case study n2
Pre-split design in chlorite metandesites
Current pre-spli t spacing = 1.8 m
Dymanic method=1.2 m
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Current pre-split design
Case study area
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Application of dynamic method, case study n3
Pre-split design in Qz-Sericite Granodiorite
Current pre-spli t spacing = 0.9-0.7 m
Dymanic method=1.3 m
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Results with S=1.8 m
Results with S=1.3 m (Dynamic method)
Design achieved with S=1.3 m
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The new method proposed considers Vp and Ed as a relevant variables into the
borehole pressure decay factor. Therefore geotechnical properties are contemplate.
Geotechnical properties of rock massif can be evaluated by cross hole techniques
(Vp).
The spacing of pre-split holes can be obtained for different geotechnical domains
follow the dynamic method.
Dynamic methods demonstrates Improvements in bench quality and bench design
achieved.
Conclusion
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T H A N K Y O U