Theory and Implementation of the Itasca Constitutive Model for Advanced Strain Softening (IMASS)

Ghazvinian, E.; Garza-Cruz, Tryana; Bouzeran, Lauriane; Fuenzalida, Miguel; Cheng, Zhi‐Lin; Martinez, Christian; Pierce, Matthew

doi:10.36487/acg_repo/2063_30

Cited by 10 publications

(4 citation statements)

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“…Material layering using a Hoek-Brown (HB) fitting envelope as shown in Figure 6. This addresses the challenge that in realistic caving behaviours the confining stress changes the equivalent friction angle (and cohesion) in a non-linear relationship and became apparent when calibrating models with cave heights exceeding 1,000 m. This also provides better comparison with more realistic models such as demonstrated by the Itasca constitutive model for advanced strain softening for caving (Ghazvinian et al 2020) (Figure 5b).…”

Section: Materials Modellingmentioning

confidence: 94%

Investigating economic and risk metrics using design of experiments in fully coupled caving geomechanics simulation

Arndt¹,

Villa²,

Khodayari³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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Technology for fully coupled simulation of the caving process, typically accounting for the flow of material using cellular automata (CA3D) and using non-linear stress-strain analysis (finite element method, FEM) for cave propagation, has been emerging over the last decade. The highest level of autonomy in this domain is achieved with automated model construction and meshing capabilities directly driven from data pertaining block model, geotechnical domains, drawpoints and production schedule, as is the case using a block cave model in the PCBC software from Dassault Systèmes. This process automation enables encapsulating the simulation into advanced 'design space exploration' tools such as design of experiments (DoE) -referring to the ability to quantify the influence matrix of a large range of individual parameters and metrics and search the results space for behaviours of interest or optimise for desired outcomes.Examples of such investigations can include understanding the mechanisms causing cave propagation to stall with the risk of creating an airgap or comparing alternative schedules with different directional scenarios for cave establishment and its impact both on geomechanics, such as fault activation, as well as project net present value (NPV). The encapsulation can extend to more complex downstream processing, such as detailed grade analysis, linking block model information to processing parameters or energy consumption. Importantly, integration with business drivers such as de-carbonisation and sustainability becomes possible.

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Section: Materials Modellingmentioning

confidence: 94%

Investigating economic and risk metrics using design of experiments in fully coupled caving geomechanics simulation

Arndt¹,

Villa²,

Khodayari³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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“…All geological entities were modelled with the strain-softening IMASS (Itasca Constitutive Model for Advanced Strain-softening; Ghazvinian et al 2020) material model. The required inputs are the following intact rock properties:…”

Section: Methodsmentioning

confidence: 99%

Analysis of caving and ground deformations in Malmberget using a coupled CAVESIM-FLAC3D model

Sjölander¹,

Jönsson²,

Figeiredo³

et al. 2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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Large-scale sublevel cave mining (SLC) remains the mining method of choice for efficient underground mining of iron ore at the Luossavaara-Kiirunavaara AB (LKAB) mines in Kiruna and Malmberget, northern Sweden. However, SLC mining ultimately results in ground deformations above active mining areas, thus necessitating relocation of surface infrastructure and/or residential areas within the locations containing large and damaging deformations. Moreover, caving may also affect underground infrastructure and a prediction methodology for both surface effects and underground infrastructure is warranted. A coupled CAVESIM-FLAC3D model was developed for the LKAB Malmberget mine. Initially, a mine-scale model with the centrally located major orebodies was set up for detailed analysis of critical infrastructure. This was followed by an extended model in which all orebodies and production areas (approximately 20 of them) were included. Large-scale geological structures were included in the model, as well as the local geology. The coupled modelling approach enables simulating production and material flow, as well as the rock mass response outside the caved volumes. Production was simulated from the start of mining up until today and the model calibrated against observed cave cratering on the ground surface and inferred cave shapes from seismic monitoring, followed by model validation against measured ground surface deformations. The calibrated model was then run for future mining and a planned production increase, up until the year 2070. The results were evaluated with respect to: (i) surface cave cratering, (ii) ground surface deformations, (iii) strains on the ground surface and (iv) cave shapes and deformations around critical underground infrastructure.Alternative re-locations of underground infrastructure were compared and stability conditions quantified, as input for planning decisions made by the mine. For the ground surface, the model results provided a quantitative prediction of which areas will be affected, both spatially and temporally. For areas within the Malmberget township, these predictions are critical for planning and execution of the ongoing urban transformation. Moreover, the model provided predictions of ground surface affects within and near the industrial area, as input to future location of planned new surface infrastructure. The coupled modelling approach and the extensive calibration process was instrumental in developing reliable and accurate predictions for the continued mining at the Malmberget mine.

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“…Compaction is considered by repeating this process of removing stresses until reaching a target bulking factor within the cave. The simulation of this compaction is possible due to the use of the IMASS model (Ghazvinian et al 2020), which includes two softening modes in the post-peak behaviour. The first, defining the decay from peak to post-peak strength, is controlled by accumulated plastic shear strain.…”

Section: Methodsmentioning

confidence: 99%

Modelling considerations for cave compaction at New Afton Mine

Martinez¹,

Fuenzalida²,

Kamp³

2022

Caving 2022: Fifth International Conference on Block and Sublevel Caving

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New Afton is a block caving mine located 10 km outside of Kamloops, British Columbia, Canada. The mine operates two lifts, Lift 1 and B3, with two separate caves on Lift 1, the West Cave (WC) and the East Cave (EC). Lift 1 and B3 production levels are located approximately 600 m and 760 m below the ground surface. New Afton has a unique combination of geometric geotechnical conditions when compared to other cave mines, including: 1) a narrow and long footprint; 2) faulted and poor ground areas; and 3) a high horizontal induced stress environment.During mining of the EC, where a majority of the poor rock mass conditions exist, after the cave was propagated through to surface, local areas of the footprint experienced severe damage and high tunnel convergence, which led to some areas being difficult to access and routinely mine. Because of this, the caved and fragmented material located on top of these drawpoints has experienced a high degree of caved rock compaction over time.New Afton was able to successfully rehabilitate much of these areas while observing compacted cave material, but in addition, a Front Cave Recovery Level (FC) was designed 20 m below a section of the EC production level with the purpose of mining the reserves below and recovering supplemental reserves left by the drawpoints.Cave propagation within compacted cave material requires additional consideration when being used in modelling. A methodology to consider compaction within the EC was proposed using the IMASS model. Assuming two different degrees of compaction for the pre-existing EC, the FC was then assessed with a coupled modelling approach using FLAC3D and REBOP to simulate both the draw/flow and caving propagation to determine abutment stresses and cave loads induced on the production level as material was drawn. It was found that having different degrees of compaction significantly affected the predicted caving rate and cave geometry, affecting ultimate recovery.

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Theory and Implementation of the Itasca Constitutive Model for Advanced Strain Softening (IMASS)

Cited by 10 publications

References 0 publications

Investigating economic and risk metrics using design of experiments in fully coupled caving geomechanics simulation

Investigating economic and risk metrics using design of experiments in fully coupled caving geomechanics simulation

Analysis of caving and ground deformations in Malmberget using a coupled CAVESIM-FLAC3D model

Modelling considerations for cave compaction at New Afton Mine

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