Blasting and preconditioning modelling in underground cave mines under high stress conditions
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Date
2021
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Abstract
Cave mining is an underground mass mining technique. The largest projects, which are known as 'super caves', produce hundreds of thousands of tons of ore per day, which involves large footprints with considerable column height, and have a life of mine of over 20-40 years. These operations are typically located deep, under high stresses and in competent rock masses, making initiation and propagation of the caving process harder to manage. These challenges must be confronted by optimizing the fragmentation of the orebody to achieve smaller size blocks that will result in consistent caving and improved flow of the ore from the drawpoints. To achieve better performance from the drawpoints, preconditioning is applied to fragment and damage the material required to cave.
We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models.
Caving operations undermine a massive orebody to initiate the collapse, comminution, and flow of the ore to multiple drawpoints. Cave mining operations are facing greater challenges due to greater depths. In Chile, some mines are up to a kilometre deep, such as the Chuquicamata Underground and the El Teniente New Mine Level copper projects. Besides the depth of the mines, the rock mass presents challenging characteristics, with fewer open structures, or joints filled with cohesive material; both conditions causing difficulties for the mining process, the caving of the ore, fragmentation, and seismicity. The problems associated with the mines operation impact safety, operational continuity, and ultimately business sustainability. To mitigate the difficulties, preconditioning (PC) has been implemented in Chile to weaken the rock mass by hydraulic fracturing (HF), and this has shown favourable results in terms of the seismic response of the cave. In addition to HF, preconditioning with explosives (DDE or dynamic debilitation
We present a proposed design for preconditioning in underground mines, considering the challenges that these large-scale mines are already facing, based on a comprehensive analysis of current design parameters, case studies, and sensitivity analyses using numerical models.
Caving operations undermine a massive orebody to initiate the collapse, comminution, and flow of the ore to multiple drawpoints. Cave mining operations are facing greater challenges due to greater depths. In Chile, some mines are up to a kilometre deep, such as the Chuquicamata Underground and the El Teniente New Mine Level copper projects. Besides the depth of the mines, the rock mass presents challenging characteristics, with fewer open structures, or joints filled with cohesive material; both conditions causing difficulties for the mining process, the caving of the ore, fragmentation, and seismicity. The problems associated with the mines operation impact safety, operational continuity, and ultimately business sustainability. To mitigate the difficulties, preconditioning (PC) has been implemented in Chile to weaken the rock mass by hydraulic fracturing (HF), and this has shown favourable results in terms of the seismic response of the cave. In addition to HF, preconditioning with explosives (DDE or dynamic debilitation
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Keywords
fragmentation, preconditioning, caving, blasting, structures, stresses