Block Cave Operation Research Articles

A Discrete Element Method Calibration Approach for Large Ore-flow Applications

The major constraint for large discrete element method (DEM) simulations is the high demand for computation power. To keep the model in a feasible range of simulation time and to conduct the numerical calculations efficiently, the implemented material can be simplified and upscaled. After this, a calibration of the material is inevitable and sets the link between the simulation model and reality. Therefore, an alternative calibration approach is established in this contribution to mimic the flow behaviour of the original material with multi-spherical DEM particles. The calibration approach utilises flow zone dimensions, which were observed in block-caving operations. Additionally, a passive draw-point is used to calibrate the angle of repose. Applying the calibration approach for Kiruna iron ore showed that, with the help of the calibration approach, the material in the simulation could successfully reproduce the targeted flow zone and angle of repose.

Operational mine planning in block cave mining: a simulation-optimisation approach

ABSTRACT Block cave mining operations face challenges to meet daily operational production targets. The optimistic long-term and medium-term plans along with uncertainty and the synergistic effect of the mechanical and structural failures in operational levels of the mine cause a significant deviation from production plan targets. The on-site tuning of the mining production targets in real time are neither the best practice nor the optimum approach to compensate for shortfalls in production. The objective of this paper is to develop a methodology that generates practical and near-optimal short-term mine plans for block caving operations in the presence of operational uncertainty. To accomplish this goal, we propose a simulation-optimisation approach using a Monte Carlo simulation model and a multi-objective non-linear goal programming model that takes into consideration operational constraints and uncertainties. In a case study, we compare the results of the proposed methodology against the mine plan and the historical production data of a copper block cave operation. The strengths and weaknesses of the model are presented and discussed.

Draw rate management system using mathematical programming in extraction sequence optimisation of block cave mining

Planning of caving operations poses complexities in different areas such as safety, ground control and production scheduling. Draw control is fundamental to the success of block-cave operation. Although some complex theories and mathematical draw control systems have been applied in block-cave mines, most of them did not have an exact production rate curve (PRC) to manage draw rates of drawpoints and are too complex to provide a solution for real block-caving mines. This paper presents a mixed-integer linear programming (MILP) model to optimise the extraction sequence of drawpoints over multiple time horizons of block-cave mines with respect to the draw control systems. Four draw rate strategies are formulated to guarantee practical solutions. Furthermore, dilution and caving are improved indirectly, because the method considers the draw rate strategy. Application and comparison of the four models for production scheduling based on draw control systems are presented using 298 drawpoints over 15 periods.

Draw rate management system using mathematical programming in extraction sequence optimisation of block cave mining

Planning of caving operations poses complexities in different areas such as safety, ground control and production scheduling. Draw control is fundamental to the success of block-cave operation. Although some complex theories and mathematical draw control systems have been applied in block-cave mines, most of them did not have an exact production rate curve (PRC) to manage draw rates of drawpoints and are too complex to provide a solution for real block-caving mines. This paper presents a mixed-integer linear programming (MILP) model to optimise the extraction sequence of drawpoints over multiple time horizons of block-cave mines with respect to the draw control systems. Four draw rate strategies are formulated to guarantee practical solutions. Furthermore, dilution and caving are improved indirectly, because the method considers the draw rate strategy. Application and comparison of the four models for production scheduling based on draw control systems are presented using 298 drawpoints over 15 periods.

An application of mathematical programming to determine the best height of draw in block-cave sequence optimisation

Planning block-caving operations poses complexities in different areas such as safety, environment, ground control and production scheduling. The objective of this paper is to develop a practical optimisation framework for production scheduling of block-caving operations. A mixed-integer linear programming (MILP) formulation is developed, implemented and verified in the TOMLAB/CPLEX environment. In this formulation, the slices within each draw column are aggregated into selective units using a hierarchical clustering algorithm and the mining reserve is computed as a result of the optimal production schedule for each advancement direction. This paper presents a model application of a production schedule for 102 drawpoints with 3457 slices over 14 periods. The results show in order to obtain the maximum net present value (NPV), only 88% of the reserve is extracted. Also, the solving time for the presented method is 78 times faster than method without slice aggregation.

In situ monitoring of rock fracturing using shear wave splitting analysis: an example from a mining setting

SUMMARY Changing stress conditions are well known to cause rupturing of rock. This is well constrained on a small scale from laboratory experiments and inferred on a much larger scale from tectonic earthquakes. Here, we present a study of rock fracturing induced by changes in stress state during block-caving operations in an Australian mine. This intermediate-scale study provides further evidence of the scalability of processes involved in rock fracturing and thus helps to link laboratory and seismological observations. We analyse the temporal evolution of rock fracturing during a production cycle using the analysis of fracture-induced anisotropy. Fracturingoftherockmassismonitoredusingevidenceofseismicanisotropyfromestimates of shear wave splitting and their subsequent inversion for fracture parameters. The data set consists of more than 40 000 three-component seismograms recorded by an array of sensors, which provides excellent ray coverage. We applied a novel automatic quality assessment technique to handle this large data set and find that anisotropy, and thus fracturing, correlates strongly with the excavation process. We then perform a grid search over a series of synthetic models based on rock physics to invert the splitting parameters for fracture orientation and density. Finally, by applying a sliding window on our results, we are able to identify production related fracture evolution. During production the fracture density increases, with horizontal fracture density being stronger than the vertical fracture density. This can be explained by the removal of the supporting rock during caving. During short intervals of reduced production, the horizontal fracture density decreases, whereas vertical fracture density increases. We relate this to change in stress regime with reducing overburden mass during cavity collapse. This scenario is similar to a collapsing caldera or the inverse of an inflating magma chamber.