Back-analysis of PC1 cave propagation and subsidence behaviour at the Cadia East mine

Sainsbury, Bre-Anne; Sainsbury, David; Carroll, Diana

doi:10.36487/acg_rep/1815_10_sainsbury

Cited by 8 publications

(8 citation statements)

References 3 publications

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“…Once the cave was imported, from FLAC3D the model was stepped to equilibrium and the slip and separation of the structures surrounding the crater were observed. The FLAC3D model used is consistent with that described in Sainsbury et al (2018).…”

Section: Figure 4 Coupling Of Flac3d and 3dec Modelsmentioning

confidence: 99%

“…A successful back-analysis of the cave propagation behaviour of the PC1 Cave at Cadia East was completed by Sainsbury et al (2018). The back-analysis was able to accurately predict the initial yield advance, critical hydraulic radius, interaction with overlying infrastructure (5050 m RL and 5250 m RL levels) including the narrowing of the cave crown and eventual stall on the capping porphyry.…”

Section: Introductionmentioning

confidence: 99%

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A coupled modelling approach for discontinuous subsidence at the Cadia East mine

Sainsbury¹,

Sainsbury²,

Osorio³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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It is known that in addition to the production schedule, a number of orebody, geologic and topographic features can influence the nature and extent of surface subsidence related to a cave mine. Some of these factors include the shape and depth of the orebody/extraction level in plan, strength of the rock mass including the intact blocks, joints and geological features such as faults and dykes, ground surface profile, including historical surface mining and the presence of nearby underground excavations (Sainsbury 2012). Brady and Brown (2006) classify subsidence into two types, continuous and discontinuous. Continuous (or trough) subsidence refers to the formation of a smooth (gradual) change in profile that does not have step changes. Discontinuous subsidence involves large surface displacements (both tension and shear) and the formation of steps/breaks in the surface profile. Discontinuous subsidence is strongly affected by the presence of pre-existing features within the rock mass. As such, it cannot be accurately assessed without the inclusion of such features within a three-dimensional numerical model.A coupled continuous-discontinuous approach has been developed to predict caving and subsidence efficiently and accurately at the Cadia East mine over an eight-year production life (or 150 MT drawn). Numerically simulated results with the coupled approach are compared to in situ observations. It can be seen that in the case of sub-vertical structures within the near-surface rock mass, traditional strain criteria applied alongside continuum models are unable to capture the true shape or extent of cracking and that discontinuum models provide greater accuracy.

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Section: Figure 4 Coupling Of Flac3d and 3dec Modelsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A coupled modelling approach for discontinuous subsidence at the Cadia East mine

Sainsbury¹,

Sainsbury²,

Osorio³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

Self Cite

View full text Add to dashboard Cite

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“…Application of advanced numerical models are therefore essential to adequately analyse and design different geotechnical aspects of cave mining (e.g. Vyazmensky 2008;Elmo et al 2008Elmo et al , 2010Sainsbury et al 2011Sainsbury et al , 2018Beck & Pfitzner 2008;Beck & Putzar 2011). Despite increased modelling ability, full-scale forward modelling of caving processes remains problematic.…”

Section: Introductionmentioning

confidence: 99%

An effective numerical method to understand different aspects of cave preconditioning

Elmo¹,

Rogers²,

Veltin³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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Full-scale forward geomechanical modelling of the caving process, remains problematic, challenging the key principles of numerical analysis applied to rock engineering problems: i) a model is not and cannot be a perfect imitation of reality; and ii) numerical modelling is driven by questions. This paper presents a simpler numerical solution that follows fundamental modelling principles, whereby simple models are used to analyse different aspects of a given problem and to determine which process need to be considered explicitly and which can be represented in an average way. Synthetic cave models (SCM) are introduced as a suitable modelling approach for optimising hydrofracturing design and draw strategy by investigating a range of possible scenarios. The SCMs can be considered a scaled down version of a large, although simplified, mine scale problem. In the current paper, we have used SCM at different scale in terms of the adopted width of the simulated undercut. All modelling scenarios consider the development of a relatively deep cave located at a depth of 1,400 m. Due to their simple and conceptual nature, these models allow us to analyse different aspects of cave mechanics, including cave initiation, cave propagation, effectiveness of preconditioning, draw sequence and caving rates.

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“…Table 1 shows a summary of the applications in cave mining and petroleum but also the objective related to each extraction method. While petroleum engineering application focus on increase permeability, cave mining has exhibited evidence of: better seismic response (Johnson & Martinsson 2018), better cave propagation (Sainsbury et al 2018) and better fragmentation size (Brzovic & Gonzalez 2019).…”

Section: Introductionmentioning

confidence: 99%

Hydraulic fracturing in cave mining: Opportunities for improvement

Rimmelin¹,

Chitombo²,

Valdivia³

2020

MassMin 2020: Proceedings of the Eighth International Conference &Amp; Exhibition on Mass Mining

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Hydraulic Fracturing (HF) in cave mining is commonly used in competent rock under high stresses and seismic conditions, to manage risks associated with induced seismicity and cave propagation. The HF process is done using up holes drilled from the undercut level (e.g. El Teniente -Codelco) or down holes from an upper level (e.g. Newcrest mining). Discrete fractures assumed to be in the order of 20 to 40 m in diameter are then created every 1.5 m or 2.5 m along the drill holes, using water at higher pressures. In comparison, other industry experience such as Petroleum, HF is based on similar principles in terms of the drill hole alignment with the principal stresses and the use of water at high pressures, but more efficient during the process of the creation of the network of fractures. The network of fractures thus created covers a volume rather than discrete fractures and could be as long as 100 m. Currently, petroleum HF process is carried out from the surface down to 3,000 m in depth. Also, the use of additional materials such as "sand" to improve the propagation of fractures is another example of Petroleum practices that can be used in Cave Mining. Another point of discussion relies on the current practices in Cave mining, in which, stress anisotropy is not considered to address important topics such as efficiency of the HF process and spatial distribution of the HF holes, for a better coverage of the rock mass. Hydraulic Fracturing is increasingly becoming an essential enabling tool in deep hard rock cave mining, and some of the current HF practices used in the Petroleum industry offer an opportunity to improve the cave mining HF processes. This paper proposes the use of known rock mechanics principles for the cave mining industry to adopt practices used in the Petroleum to achieve the intended outcomes from HF as currently used in cave mining.

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Back-analysis of PC1 cave propagation and subsidence behaviour at the Cadia East mine

Cited by 8 publications

References 3 publications

A coupled modelling approach for discontinuous subsidence at the Cadia East mine

A coupled modelling approach for discontinuous subsidence at the Cadia East mine

An effective numerical method to understand different aspects of cave preconditioning

Hydraulic fracturing in cave mining: Opportunities for improvement

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