Design of an economically feasible support for the replacement of pillars in Providencia Mine, Antioquia - Stage 1

Claudia Yasmin Montaño-Chinchilla,Ludger Oswaldo Suarez-Burgoa,Elkin De Jesús Ceballos-Guerra,Jorge Martin Molina-Escobar

doi:10.19053/01211129.v28.n51.2019.9199

Claudia Yasmin Montaño-Chinchilla, Ludger Oswaldo Suarez-Burgoa + Show 2 more

Open Access

https://doi.org/10.19053/01211129.v28.n51.2019.9199

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Abstract

Pillar replacement in mining works is a technique of using the pillars that are part of the support structures having a high degree of mineralization, which attracts economic interest. The technique consists of replacing the support pillars of the mineral matrix that contain appreciable and beneficial quantities of mineral by artificial pillars that provide geomechanical structure to the operations, generating support and safety benefits greater than or equal to those provided by the original pillars and thus maximizing the intrinsic economic value of the available rock in the operation. Based on the literature regarding design techniques for the assembly of pillars used in underground gold mining, daily and continuous field inspections were conducted for two months, taking the necessary data for the proposed design following ISRM standards for data collection. The proposed pillars must consider a set of operational economic requirements and meet the geomechanical performance required to guarantee the safety and stability of the site. The design consisted of a combination of two types of pillars, one of concrete and one of mesh, cables and sterile material (granodiorite and dyke). The measurements consisted of RMR determination, the dimensions of the current pillars, and the geomechanical condition using detailed scanlines. Subsequently, the information was refined and correlated, and the degree of fracture and safety factor of the original pillars versus those proposed in the new designs were calculated. As a result, the optimal design for the construction of the replacement pillars should have dimensions of 2 x 1.7 x 1.7 meters, achieving a safety factor of 1.36, complying with the geomechanical requirements of safety and stability and yielding a profit of 405 % as a cost-benefit ratio in replacing the original pillars by those proposed in the design; the sterile material and mesh pillars would have dimensions of 2 x 2 x 2 meters.

Highlights

A pillar is an in situ rock column that is left to prevent a zone or level of excavation from collapsing inside an underground mineral extraction operation
In cases where the pillars have an appreciable degree of mineralization and their extraction is considered economically and technically viable, these pillars are replaced by artificial support pillars, commonly hybridized concrete with wall rock associated with the vein, which maintains or improves the geomechanical performance provided by the original pillar; this performance depends on the particular requirements of the intervening areas, preventing the collapse of the supported areas
The main product of the project is the design of the pillars, which are made of sterile material with reinforced steel mesh and cables that confine and reinforce each pillar; a combination of designs using concrete pillars is sought

Summary

INTRODUCTION

A pillar is an in situ rock column that is left to prevent a zone or level of excavation from collapsing inside an underground mineral extraction operation. In cases where the pillars have an appreciable degree of mineralization and their extraction is considered economically and technically viable, these pillars are replaced by artificial support pillars, commonly hybridized concrete with wall rock associated with the vein, which maintains or improves the geomechanical performance provided by the original pillar; this performance depends on the particular requirements of the intervening areas, preventing the collapse of the supported areas. The pillars of the area are below the ramp, which is a work in development, a main access The grade of this vein is four times the cut-off grade of the mine (as previously mentioned), the vein thickness is 0.7 m, and the estimated weight is 1218 ounces. The nature of the project falls under a framework of geomechanics and economics, where the main objective is to arrive at a design of stable replacement pillars with costs that can be assumed by the operation without affecting its economic stability. The scope of the project is to achieve a pillar design that complies with the premise of being stable and providing safety to the mine and at the same time allowing the recovery of the mineralized pillars at a low cost

INSTRUMENTATION AND METHODS

RESULTS

Cost analysis

DISCUSSION AND CONCLUSIONS