TY - BOOK

T1 - A theoretical and numerical approach to investigate critical aspects of ore-flow in deep cave mining

AU - Koch, Lukas

N1 - embargoed until 08-07-2026

PY - 1800

Y1 - 1800

N2 - Ore-flow can decide about efficiency, profitability and safety of a cave mine operation. The target of this thesis was to create a tool to investigate critical points of ore-flow in large mines. Therefore, the discrete element method (DEM) was chosen, which uses contact models based on physical laws to compute particle interactions and the overall bulk behavior in the mine. A common limit with real-scale DEM models is the necessary computational demand. Simplification measures need to be applied, whose limitations are often not known. The material in the software needs to be calibrated, which is often either not done due to the lack of calibration approaches or not described in research papers. This is especially the case for very large DEM models with material that is unsuitable for common laboratory experiments due to its size or large variety in the fragmentation. In this thesis, large stopes filled with several million particles should be simulated. The simplification measure `artificial shear modulus reduction¿ was tested with simple material in a stope and could be implemented within its limits. Further, the particle upscaling method was tested for a simple and a more complex fragmentation and was successfully implemented in the simulations. The computation with GPU was tested for its suitability and limit to exchange the common CPU computation, leading to its utilization in this thesis. Combining these measures, the computation time could be lowered by a multiple. A parameter study was conducted on how to achieve a realistic bulk density in the setup of a large DEM model. Subsequently, a novel calibration method was established for large DEM simulations in mining applications. The basis for the calibration is formed by measurements from draw-points in the mine and empirical flow data from block cave mines. This led to a successful calibration of a representative material, which could consequently be applied for research purposes on a novel mining method. The application example of the developed tool was on the novel Raise Caving (RC) method, under joint development with LKAB Kiruna, Sweden. Available material data was taken from Kiruna mine to establish a connection to its iron ore. Meanwhile the interaction parameters were calibrated to guideline values from block caving (BC), as the free flow situation resembles the one in RC. As the first point, the influence of the extraction dynamics, as well as a different wall structure on the result were tested. Further the influence of the draw-bell inclination on the ore-flow was successfully simulated to find a favorable angle. The draw-point spacing was subsequently simulated to find the optimal distance for a complete extraction by simultaneously little amount of infrastructure. Thereby, the results suggest an advantage of the large draw-bell design compared to conventional BC draw-bells. Different draw-point patterns were introduced and concepts of draw-bell and draw-point design were proposed. A horizontal cross-cut additionally showed elliptical flow zones instead of perfectly circular ones. This was already discussed by researchers in literature, it is however not yet considered in BC guidelines. Investigations on the shape of the brow were conducted. The obtained findings are especially important for a correct positioning of draw-points in mine planning. It was further found that there is a correlation between the direction of the draw-point towards the draw-bell and the center of the draw-zone. Finally, the necessary extraction amount for the free surface on top of the bulk material pile was investigated. The free volume needs to be ensured for blasting gases and the swell volume of the blasted material. A simple calculation of the swelling layer might underestimate the needed extraction mass and a constant monitoring from the raise is seen as essential. Finally,

AB - Ore-flow can decide about efficiency, profitability and safety of a cave mine operation. The target of this thesis was to create a tool to investigate critical points of ore-flow in large mines. Therefore, the discrete element method (DEM) was chosen, which uses contact models based on physical laws to compute particle interactions and the overall bulk behavior in the mine. A common limit with real-scale DEM models is the necessary computational demand. Simplification measures need to be applied, whose limitations are often not known. The material in the software needs to be calibrated, which is often either not done due to the lack of calibration approaches or not described in research papers. This is especially the case for very large DEM models with material that is unsuitable for common laboratory experiments due to its size or large variety in the fragmentation. In this thesis, large stopes filled with several million particles should be simulated. The simplification measure `artificial shear modulus reduction¿ was tested with simple material in a stope and could be implemented within its limits. Further, the particle upscaling method was tested for a simple and a more complex fragmentation and was successfully implemented in the simulations. The computation with GPU was tested for its suitability and limit to exchange the common CPU computation, leading to its utilization in this thesis. Combining these measures, the computation time could be lowered by a multiple. A parameter study was conducted on how to achieve a realistic bulk density in the setup of a large DEM model. Subsequently, a novel calibration method was established for large DEM simulations in mining applications. The basis for the calibration is formed by measurements from draw-points in the mine and empirical flow data from block cave mines. This led to a successful calibration of a representative material, which could consequently be applied for research purposes on a novel mining method. The application example of the developed tool was on the novel Raise Caving (RC) method, under joint development with LKAB Kiruna, Sweden. Available material data was taken from Kiruna mine to establish a connection to its iron ore. Meanwhile the interaction parameters were calibrated to guideline values from block caving (BC), as the free flow situation resembles the one in RC. As the first point, the influence of the extraction dynamics, as well as a different wall structure on the result were tested. Further the influence of the draw-bell inclination on the ore-flow was successfully simulated to find a favorable angle. The draw-point spacing was subsequently simulated to find the optimal distance for a complete extraction by simultaneously little amount of infrastructure. Thereby, the results suggest an advantage of the large draw-bell design compared to conventional BC draw-bells. Different draw-point patterns were introduced and concepts of draw-bell and draw-point design were proposed. A horizontal cross-cut additionally showed elliptical flow zones instead of perfectly circular ones. This was already discussed by researchers in literature, it is however not yet considered in BC guidelines. Investigations on the shape of the brow were conducted. The obtained findings are especially important for a correct positioning of draw-points in mine planning. It was further found that there is a correlation between the direction of the draw-point towards the draw-bell and the center of the draw-zone. Finally, the necessary extraction amount for the free surface on top of the bulk material pile was investigated. The free volume needs to be ensured for blasting gases and the swell volume of the blasted material. A simple calculation of the swelling layer might underestimate the needed extraction mass and a constant monitoring from the raise is seen as essential. Finally,

KW - Cave mining

KW - Mine design

KW - Ore-flow

KW - Discrete Element Method

KW - Bruchbau

KW - Bergbauplanung

KW - Erzfluss

KW - Diskrete Elemente Methode

M3 - Doctoral Thesis

ER -