PT Freeport Indonesia – The transition to underground production

Casten, Tim; Johnson, Matthew H.; Zimmer, Cínthia Gabriely; Mahayasa, Made

doi:10.36487/acg_repo/2063_0.03

Cited by 4 publications

(7 citation statements)

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“…• Long development times before achieving planned production and associated high upfront costs: In order to achieve a high production and productivity, significant amount of infrastructure pre-development and preparatory activities, such as preconditioning or undercutting are necessary before production can commence. Consequently, the capital costs are high and the lead time, until stable production meeting the set target is achieved, is long; see for example Araneda (2020) or Casten et al (2020).…”

Section: Specific Challenges Faced In Cave Miningmentioning

confidence: 99%

Raise caving: a novel mining method for (deep) mass mining

Ladinig¹,

Wimmer²,

Wagner³

2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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Raise caving is a novel mining method, which is based on the raise mining method. Raises are central and utilised for different purposes. Here only those directly related to the extraction of the orebody will be discussed. The main objective of raises is to utilise them for creating de-stressing slots, large drawbells and large stopes in an efficient manner. Remote-controlled or automated machinery is operated in raises. Further objectives of raises comprise monitoring and preconditioning. Depending on the field of application two different variants of raise caving can be distinguished, namely a de-stressing variant and a block caving variant.In the de-stressing variant, narrow slots are created first with the objective of providing stress shadows for mining activities in the subsequent production phase. Creating the slots in the de-stressing phase is high stress mining. Hence, massive pillars are left between slots to control the stress situation for de-stress raise development and mining-induced seismicity. After the de-stressing phase is completed, large-scale mineral extraction commences in de-stressed zones. In the production phase large drawbells are developed from raises and large stopes are extracted. During stope blasting only the swell of each blast is mucked so that blasted rock mass provides temporary support to the stope walls. After blasting is completed, the stope is drawn empty and the hanging wall is allowed to cave and caved hanging wall rock mass fills up the stope successively. The massive pillars are extracted in the course of large-scale stoping in the production phase too.In the block caving, variant raises are utilised for drawbell development, undercutting, preconditioning and monitoring purposes. Large drawbells are developed from raises. As drawbells are developed in upward direction, the roof area of the drawbells is enlarged constantly until continuous caving is initiated. Due to the integration of several key activities the block caving variant of raise caving is also referred to as integrated raise caving. This paper highlights the background and motivation for raise caving and it describes both raise caving variants. Steps for the implementation of the methods are outlined and advantages of the individual methods are outlined briefly. Key issues for the implementation of raise caving are highlighted and discussed, and an outlook on currently ongoing research and development activities, which include in situ tests of the method and machinery, is provided. Dedicated accompanying papers provide more information on the ongoing research and development.

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Section: Specific Challenges Faced In Cave Miningmentioning

confidence: 99%

Raise caving: a novel mining method for (deep) mass mining

Ladinig¹,

Wimmer²,

Wagner³

2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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“…The Grasberg mining complex, operated by PT Freeport Indonesia (PTFI), is located in the southern area of Jaya Wijaya Mountains, West Papua, Indonesia. Four mines are currently operating: three caving operations at the DOZ, Deep Mill Level Zone (DMLZ) and Grasberg Block Cave (GBC) mines, and the Big Gossan stoping mine (Casten et al 2020). In addition, PTFI has several potential future operations, including the Kucing Liar and Gajah Tidur resources.…”

Section: History Of Wet Muck Spills At the Deep Ore Zone Minementioning

confidence: 99%

“…The DOZ mine is the third lift of the block cave mine in the East Ertsberg Skarn System (EESS), after the Gunung Bijih Timur (GBT) and Intermediate Ore Zone (IOZ) mines. By 2019, the DOZ mine had produced 300 million tonnes of ore since it opened in 2000 (Casten et al 2020). The extraction level is at a depth of approximately 1,200 m below the surface and includes 1,347 drawpoints across 39 panels with column heights up to 750 m. The extraction level was constructed with an offset herringbone layout to minimise wet muck flow distances.…”

Section: History Of Wet Muck Spills At the Deep Ore Zone Minementioning

confidence: 99%

Development of a wet muck spill susceptibility tool for short-term prediction through a logistic regression approach

Varian¹,

McDougall²,

Ghadirianniari³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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The Grasberg mining complex in Papua, Indonesia, consists of three caving operations and an open stope mine. Two of the caves, the Grasberg Block Cave (GBC) and the Deep Mill Level Zone (DMLZ), are ramping up to full production, while the Deep Ore Zone (DOZ) cave will cease operations in 2022. The DOZ has had a history of production interruptions due to wet muck spill events. The newer caves expect to be affected by similar wet muck hazards due to the presence of fines and saturated material at the muck pile, overlying open pit in the case of the GBC and overlying caves in the case of the DMLZ, high annual rainfall, and complex topography at the subsidence that directs surface and groundwater into the cave.To proactively manage this hazard, experience from the DOZ cave mine is being applied to improve the understanding of drawpoint wet muck spill susceptibility. The combination of fines generated through secondary fragmentation from the high draw columns and saturation from the intense surface and groundwater inflow results in wet muck material at the drawpoint, providing the cause while mucking activities provide the trigger. Other contributing factors included in the analysis are the uniformity of draw and neighbouring drawpoint conditions.Although the consequences of wet muck spill events are high, they are still relatively rare, resulting in an imbalanced dataset. To overcome this challenge, cost-sensitive learning is incorporated into the logistic regression model for significant variables selection, thus developing a wet muck susceptibility tool. This tool aims to identify individual drawpoint susceptibility to wet muck spill events based on a simple material classification and measures of draw performance. The approach has been successful in describing historical drawpoint susceptibility at the DOZ. Furthermore, this study provides a concept applicable to other wet muck susceptible cave mines.

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“…The Deep Ore Zone (DOZ) and Deep Mill Level Zone (DMLZ) mines were developed to extract porphyry and skarn style mineralisation (copper and gold). The East Ertsberg Skarn System (EESS) hosts the orebody which has been progressively mined deeper by PT Freeport Indonesia (PTFI) since the 1980s using cave mining methods (Casten et al 2020). As such, the experiences from the DOZ and DMLZ are an excellent example of how geotechnical conditions can change with increasing mining depth, particularly with respect to strainbursting conditions.…”

Section: Case Study: the Doz And Dmlz Experiencementioning

confidence: 99%

“…The mature DOZ block cave mine will soon be decommissioned when the DMLZ cave, with a footprint approximately 500 m deeper, approaches and breaks into it. The dominant controlling geotechnical problem in the DOZ was the occurrence of inrushes of wet muck (Casten et al 2020) but strainbursts were also observed. Strainbursting in the DOZ was an irregular and localised problem, which mostly occurred when the cave was well established.…”

Section: Case Study: the Doz And Dmlz Experiencementioning

confidence: 99%

Abutment loading in deep cave mines: towards understanding susceptibility to strainbursts

Roy¹,

Primadiansyah²,

Eberhardt³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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Deep cave mining is an inevitable requirement to meet the growing global demand for valuable minerals such as copper and gold. The experiences from historical and current deep mining suggest that the rock masses encountered at depth are more likely to be stronger, more brittle, and less jointed. While this may be a favourable condition for some mining and civil projects, under the high abutment loading associated with cave mining, the rock surrounding the mine drifts is susceptible to strainbursting, a sudden and high-energy failure mode. Loading conditions in cave mines can evolve rapidly over the course of mining, which can cause shifts in the susceptibility and triggers for strainbursting. Historical perspective on the strainbursting hazard in deep mining is presented in this paper, as well as a recent case study of the DMLZ mine where data-driven assessments have been applied to better understand the strainbursting hazard under the abutment loading condition. The strainbursting phenomenon can be difficult to manage in a complex cave mining environment. Therefore, tools and strategies for analysis of the occurrence of strainbursting that can be used to better constrain and manage the problem are discussed.

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PT Freeport Indonesia – The transition to underground production

Cited by 4 publications

References 0 publications

Raise caving: a novel mining method for (deep) mass mining

Raise caving: a novel mining method for (deep) mass mining

Development of a wet muck spill susceptibility tool for short-term prediction through a logistic regression approach

Abutment loading in deep cave mines: towards understanding susceptibility to strainbursts

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