Preconditioning Implementation On Rock Bulks In Codelco Chile And Its Results

5th International Conference and Exhibition on Mass Mining, Luleå Sweden 9-11 June 2008

MassMin 2008

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Preconditioning implementation on rock bulks in Codelco Chile and its
results
R. E. Molina Civil Mining Engineer, CODELCO CHILE GCPMS
C. B. Cerrutti Civil Mining Engineer, CODELCO CHILE Subsidiary IM2
J. O. Henriquez Civil Mining Engineer, CODELCO CHILE GCPMS
R. F. MoralesCivil Mining Engineer, CODELCO CHILE El Teniente Division
R. A. Apablaza Civil Mining Engineer, CODELCO CHILE Andina Division

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Preconditioning implementation on rock bulks in Codelco Chile and its
results
R. E. Molina Civil Mining Engineer, CODELCO CHILE GCPMS
C. B. Cerrutti Civil Mining Engineer, CODELCO CHILE Subsidiary IM2
J. O. Henriquez Civil Mining Engineer, CODELCO CHILE GCPMSR. F. Morales Civil Mining Engineer, CODELCO CHILE El Teniente Division
R. A. Apablaza Civil Mining Engineer, CODELCO CHILE Andina Division

Summary
The exploitation of deeper and mass ore bodies, results in having to operate complex rocks, exposed to
higher stress, increasing its difficulties regarding the caving, fragmentation and in some particular cases of
relevant seismicity. Codelcohas been researching for alternatives that allow to improve the underground
exploitation of own resources. Codelco has developed several Preconditioning tests (PC) on bulk rock,
through hydraulic fracturing technology and confined blasting and through a combination of both
techniques
The current paper summarizes several experiences of rock mass preconditioning carried out on the threeunderground mines of Codelco Chile, describing the characteristics of the sectors of implementation, their
designs and the results obtained. By way of conclusion, the learning method of the technology for the
capitalization of the benefits of the applications with the Block/Panel Caving exploitation method it is
showed as key.

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Introduction

In hard rock underground mining, the most low-costmethod is “Block / Panel caving”, see figure 1, that use
gravitational caving and to extract the ore from lower level.
Caving method has been used in mainly Codelco underground mines that because the ore bodies were placed
in fractured rock, a favorable condition for this method. However, nowadays the ore rocks characteristics are
few fractured, sealed fractures and hard filling so the cavingmethod don’t have the same performance.

Figure 1

Block caving method isometric

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Figure 2

Codelco underground production plan profile

The Codelco plans considers a increasing of underground mining production, since 200 Ktpd in actual
productive sectors, until productions that could be triple during the next 20 years (see Figure 2), who are
placed on deeper ore bodies, rock massvery competent, high stress and lower grades of cupper. Conditions
more complicate to use the conventional caving methods.
To improve the exploitation outcomes with more strict conditions, several innovative processes are being
carried out to have new technologies to be considered in future projects so to maintain or improve the current
productivity levels and costs of the current method. Oneof these development lines is the rock bulk
preconditioning technology (PC).
The main objective for the development of the PC technology has been to build a technically efficient
process that allows trying in situ and before the exploitation, the hard rock mass, to transform them into a
material with a better caving, fragmentation, seismic response with high standards of safety andproductivity
within environments of high stress, hardness, as well as with competitive operational costs.

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Description of the Techniques

The development technological alternatives to carry out the PC are: Preconditioning with Hydraulic
Fracturing (PCHF) and Preconditioning with Explosives (PCE), and a combination of both; this is, to
produce a first fragmentation using HF and right after, to...