Open Pit Mining Operations Research Articles

Parameter inversion and location determination of evolutionary weak layer for open-pit mine slope

In light of the complex and dynamic mechanical properties of evolving weak strata in open-pit mines, and the consequent difficulty of determining their mechanical parameters, this study uses the ultimate balance theory, along with the back analysis method combined with monitoring data on field displacement, to carry out parameter inversion using the FLAC3D numerical simulation software. The edge slope of a working pit of the Weijiamao open-pit mine was used as research object to this end. As the results obtained by the constitutive model were consistent with the field monitoring data, the evolving weak strata in the slope and the position of the landslide in the mine could be obtained. The landslide was directed northeast. The mechanism of the edge slope of the working pit was identified as unloading shear failure, and the feasibility of the method of parameter inversion was verified. The internal friction angle ϕ and cohesion C of evolving weak strata in the slope of the open-pit mine were also obtained, where this compensated for the deficiency of laboratory tests and enabled the transformation from qualitative to quantitative analysis. This can provide a reliable basis for the safe operation of open-pit mines.

Reliability-based performance analysis of mining drilling operations through Markov chain Monte Carlo and mean reverting process simulations

In recent years, commodity prices have swiftly decreased, narrowing the profit margin for many mining operations and forcing them to find effective cost management strategies to respond to low prices. Given that equipment is one of the most significant assets of a mining company, efficient equipment utilization has strong potential to reduce costs. This paper focuses on the relationship between the number of available drilling machines based on reliability analysis and the number of holes to be created on a bench of an open pit mining operation. Since equipment availability is random in nature, a range of holes to be drilled corresponding to a specified probability level was determined. To assess the performance of the proposed approach, a case study was carried out using two stochastic modeling techniques. Evolutions of reliabilities of 10 rotary drilling machines over a specific time were simulated by Markov chain Monte Carlo and mean reverting processes, using historical data. Multiple simulations were then used for risk quantification. Results show that the proposed approach can be used as a tool to assist production scheduling and assess the associated risk.

Simultaneous stochastic optimization of production sequence and dynamic cut-off grades in an open pit mining operation

An open pit mining operation is a complex system that constitutes several components or processes. An optimal production sequence that defines timing of extraction and a dynamic cut-off grade policy that defines the supply of materials from sources to destinations within the system are crucial to the success of an operation. In current practice, separate sequencing and cut-off grade models achieve these important milestones as part of strategic planning. This paper presents a mathematical model that derives the optimal extraction sequence and cut-off grade policy simultaneously considering grade uncertainty and stockpiling. A framework of genetic, maximum flow and cut-off grade algorithms solves this complex non-linear problem. An application of the method at realistic copper and gold mining operations reveals the value (up to 29% increase in discounted value) of stockpiling as well as risk quantification under uncertainty.

3D free fall rock size sensor

The energy efficiency of the grinding process is less than 1%, and it consumes about 40% of the energy in a typical open-pit mine operation (CIPEC, 2005). One of the causes of this low energy efficiency is the high variability of the run-of-mine ore hardness and size distribution, which must be measured accurately in order to develop process control strategies that will minimise their impact on mill efficiency. On-line rock hardness sensors are still unavailable and 2D rock size sensors show important limitations under uncontrolled outside lighting conditions. A rock hardness sensor based on primary crusher data analysis has provided interesting results but it requires a more accurate size measurement of the run-of-mine ore, which is a key information for evaluating the reduction ratio and compute the rock hardness index accordingly.Recently, laser 3D profiler has been identified as an interesting technology for measuring rock size distribution over a conveyor belt and they are now commercially available. This paper discusses the extension of this application to the measurement of ore size distribution as it is dumped into the primary crusher. The objectives are (1) to provide an accurate evaluation of the reduction ratio at the primary crushing stage and to allow the development of a rock hardness sensor, (2) to quantify the quality of the blast before any crushing size reduction, and (3) to address the measurement error of the fines associated with the conveyor belt system.A first prototype of the 3D rock sizing technology was evaluated in a rock quarry environment. The prototype was then improved based on the findings. The most important upgrade is a free fall rock- speed evaluation technique, which is based on the spectral analysis of a line-scan image of the rock flow. Despite some accuracy enhancement over existing 2D technologies, the 3D free fall rock-sizing sensor is still, in its industrial arrangement, limited to the measurement of a surface based rock size distribution. This limitation is due to the intrinsic depth sampling error of the 3D sensor, which sees only the front layer of the rock flow and, as a result, overestimates the percentage of coarser rocks. A full volumetric 3D free fall rock-sizing sensor was built in parallel at laboratory scale to overcome this limitation: it measures the entire volume of each piece of rock as they fall in a monolayer flow between two facing laser scanners. The resulting volumetric rock size distribution was found to be coherent to the size distribution measured by sieving, unbiased and, therefore, more accurate than any surface based rock size distribution. The volumetric 3D free fall rock-sizing sensor is proposed for upgrading commercial 2D imaging technologies, which are now used as an alternative to rock sieving in laboratory. A few industrial application scenarios, including its potential integration into an ore-sorting process, are also being investigated.

Surface and subsurface material selections influence the early outcomes of boreal upland forest restoration

Soil is an essential component supporting the growth and maintenance of forests, providing anchorage, water, and nutrients for a diversity of plants. In Canada's boreal forest, surface soils differ widely in their chemical and physical conditions, ranging from coarse to fine textured mineral soils in the uplands to organic soils in the lowlands. Industrial disturbances in the boreal region require the selective salvage of surface and sub-soils from low- and upland areas during open pit mine operations, which can be used to reconstruct different soil profiles by arranging the materials in variable layers and thicknesses. The type of materials and their configuration in the reconstructed soil profile can have a profound effect on early forest establishment in reclaimed areas. We compared the growth of trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), and white spruce (Picea glauca Moench.) on sites that had different reconstructed soils caps using varying surface soil materials (salvaged lowland peat and upland forest floor material (FFM)), placement depths (10 or 30 cm for peat, 10 or 20 cm for FFM), and subsoil material types determined by salvage depth (Bm, BC, and C). Early seedling establishment and growth and soil and climatic parameters were monitored over a five-year period. Generally, seedling growth was greatest on FFM and appeared to be related to phosphorous availability, while peat as a surface soil reduced growth, likely due to delayed soil warming in the spring and cooler soil conditions that potentially limited resource availability. However, the greater water holding capacity of the organic matter in peat also provided a benefit for seedling growth that was apparent during water limiting climatic conditions. The underlying subsoil material also influenced growth, particularly later in establishment when roots occupied the deeper subsoils. Aspen growth was greatest when the subsoil was shallow salvaged and represented a weathered subsoil (Bm) compared to the more deeply salvaged, less weathered subsoils BC and C. Aspen and pine seedlings, with their larger roots systems, may have benefited from small increases in the silt fraction of the subsoils, likely due to the greater water holding capacity of these otherwise coarse textured sandy soils. Spruce regeneration responded marginally to soil treatments because of its overall slow growth-strategy and tolerance to resource limitations. Our results indicate that different soil capping strategies affect the performance of forest regeneration during post-mining site reconstruction, and boreal forest species may vary in responses according to their ecological life strategies.

Determination of the working area of a hydraulic excavator

The article discusses the mechanisms of walking used on dragline excavators. The disadvantages of each mechanism are identified and based on this, the most promising movement mechanism is selected – a three-legged walking mechanism with a hydraulic drive. For this mechanism, the main disadvantages are also identified. The following is a technical solution that allows you to save this mechanism from the main drawback – the need to raise the center of mass of the excavator to a significant height to ensure the maximum step value. The technical solution includes the presence of a flat hydrostatic support that allows to increase the efficiency of the mechanism in open-pit mining operations. The calculation of oil consumption through a flat hydrostatic support in the conditions of its use on quarry soils with different bearing capacity is made.

Investigation of Bishop’s and Janbu’s models Capabilities on Slope Stability Problems with Special Consideration to Open Pit Mining Operations

One of the most effective parameters in economics of open-pit mines is the pit slope angle, so that the slope angle more than the optimum value increases the probability of a large failure in the pit wall and the slope angle less than the optimum value leads to increasing stripping ratio and reducing net present value of mine. Therefore, in this paper, considering the limit equilibrium methods of modified Bishop and modified Janbu and numerical models of the slope stability analysis, the effect of overall slope angle on the Economics of open pit mines was investigated. In addition, it was shown that selecting the overall slope angle less than the optimum value leads to reducing the depth of open-pit mining (the ultimate pit depth) and consequently, reducing the net present value of mine. Finally, in homogenous and Isotropic media, the results of Bishop and Janbu and numerical modeling are close together.

Multi-objective evolutionary algorithms for the truck dispatch problem in open-pit mining operations

Multi-objective evolutionary algorithms for the truck dispatch problem in open-pit mining operations

Uncertainty quantification of structural and geotechnical parameter by geostatistical simulations applied to a stability analysis case study with limited exploration data

There are many uncertain factors impacting stability analyses of rock structures. Quantification of these factors significantly impact the engineering decision making process. Some of these factors are spatially distributed within the geological domain, and the quantification of the spatial uncertainty is beneficial for stability analysis of the structure. This paper proposes an integrated methodology for a stability analysis of rock structure by incorporating spatially varying factors. This research models two key factors: one categorical structural parameter (fault zones) and one continuous geotechnical parameter (rock quality designation (RQD)). Two geostatistical simulation algorithms i.e., sequential indicator simulation and sequential Gaussian simulation are applied to quantify the spatial uncertainty by generating multiple equiprobable simulation maps of fault zones and RQD values. A slope stability analysis is performed by modeling the spatially varying fault zones and RQD. The proposed method is validated using a synthetic data set. The results from the synthetic data show the stability value of the synthetic data closely match with stability value calculated from simulated data. Finally, the proposed method is applied to a slope stability analysis for an open pit mine design where limited exploration data is available. Geostatistically simulated RQD maps from the case study mine are analyzed to determine a safe slope angle of 44° for the open pit mining operation. The proposed method can be applied for quantifying other geotechnical risk and integrated within any stability analysis framework.

Multi-objective evolutionary algorithms for the truck dispatch problem in open-pit mining operations

This work is concerned with the efficient allocation of trucks to shovels in operation at open-pit mines. As this problem involves high-value assets, namely mining trucks and shovels, any improvement obtained in terms of operational efficiency can result in considerable financial savings. Thus, this work presents multi-objective strategies for solving the problem of dynamically allocating a heterogeneous fleet of trucks in an open-pit mining operation, aiming at maximizing production and minimizing costs, subject to a set of operational and physical constraints. Two Multi-objective Genetic Algorithms (MOGAs) were specially developed to address this problem: the first uses specialized crossover and mutation operators, while the second employs Path-Relinking as its main variation engine. Four test instances were constructed based on real open-pit mining scenarios, and used to validate the proposed methods. The two MOGAs were compared to each other and against a Greedy Heuristic (GH), suggesting of of the MOGAs as a potential strategy for solving the multi-objective truck dispatch problem for open-pit mining operations.

Concurrent open-pit mine production and in-pit crushing–conveying system planning

Optimally planned In-Pit Crushing and Conveying (IPCC) systems could resolve the transportation challenges of open-pit mining operations. There is a direct correlation between IPCC planning, Open-Pit Mine Production Scheduling (OPMPS) and the haul fleet sizing problems. Solving each said problem individually does not result in global optimum, nor does it produce a practical solution. This paper develops a new mix-integer linear programming model (called M1) to integrate these problems. The model was validated by comparing it against two other benchmark models where both omit the IPCC planning. The second model (M2) combines OPMPS and truck fleet sizing, but the third one (M3) is a conventional model that deals with OPMPS and fleet sizing, separately. The results indicated that the proposed model outperforms the conventional OPMPS by adding the in-pit crushing values to the project and improving the NPVs by 3.3 and 2.4% for the hypothetical examples.

Influence of underground mining of Taseevskoye field on landscape and open-pit remining

The Baley ore body unites Taseevskoye and Baleyskoye gold mines. The internal structure of Taseevskoye field is defined by the system of longitudinal and cross deformations splitting the Baleyskaya depression into a series of large blocks. One of the main features of open-pit remining of the First ore zone of Taseevskoye field is that mining operations will continuously happen in a zone dangerous in terms of caves. Caving systems in underground mining lead to displacement of some mineral resources to underlying horizons. Hence, the main provisions are defined to study regularities of earth surface displacement within a field. Depending on the correlation of parameters the earth surface is not deformed or deformed as failures, cracks or smooth movements. The development of depression in the direction and speed increases towards the second mining. Thus, within the contours of the designed pit the rock massif is located in the zone of deformations with developed displacement under the influence of underground mining operations. Contours and sizes of dangerous zones are defined for open-pit mining operations in the zone of displacement.

Advanced DINSAR analysis on dam stability monitoring: A case study in the Germano mining complex (Mariana, Brazil) with SBAS and PSI techniques

This work presents an investigation of detection and monitoring of surface motions using Advanced Differential SAR Interferometry (A-DInSAR) with SBAS (Small Baseline Subset) and PSI (Persistent Scatterer Interferometry) techniques in the Germano iron mining complex region (Mariana, Brazil), after the collapse of the Fundão tailing dam occurred on November 5th, 2015. The research was carried out aiming to provide useful information about ground movement monitoring, planning and risk assessment in the area after the tragic event. The analysis was performed using 46 TerraSAR-X images and a Digital Elevation Model (DEM) obtained by Pleiades data. A-DInSAR processing provided the removal of the atmospheric phase artifacts, baseline related errors, DEM height error estimation and finally the ground displacement determination. The results pointed out that with both techniques it was possible to assess the stability conditions of the Germano mining assets, particularly the main structures of the Germano dam and the detection of small settlements in the mining tailings storage, pointing out that these may be an important components for risk management of open pit mining operations, including tailings dams.

Risk assessment of blasting operations in open pit mines using FAHP method

The authors would like to thank Mining Engineering Department, Islamic Azad University (South Tehran Branch) for supporting this research.

Sequential glory hole approach as a new mining method for sustainable operations

Some mines use shafts to outflow the material mined by surface methods aiming to reduce the average distance of haulage. However, this application is restricted due to the unavailability of a methodology devoted to integrating the underground structures with surface mining plans. This mismatch implies an intensive use of trucks for haulage operations. How can open pit mining operations with mobile equipment be developed without using trucks? The present study aims to develop a mining method that integrates underground structures, for material outflow, with the surface mining development reducing the truck fleet. Considering this innovative mining geometry, haulage can employ alternative equipment or even adopt the truckless concept. After the geometric simulations using mine planning software tools, the proposed method has reached a strip ratio reduction of 8.3%. In addition, the method allowed the stacking of waste rocks and dewatered tailings in mined areas during the mining of subsequent pushbacks. These results make mining more sustainable, since it reduces area affected by waste piles and tailings dams.

Estimating PM10 Concentration from Drilling Operations in Open-Pit Mines Using an Assembly of SVR and PSO

Dust is one of the components causing heavy environmental pollution in open-pit mines, especially PM10. Some pathologies related to the lung, respiratory system, and occupational diseases have been identified due to the effects of PM10 in open-pit mines. Therefore, the prediction and control of PM10 concentration in the production process are necessary for environmental and health protection. In this study, PM10 concentration from drilling operations in the Coc Sau open-pit coal mine (Vietnam) was investigated and considered through a database including 245 datasets collected. A novel hybrid artificial intelligence model was developed based on support vector regression (SVR) and a swarm optimization algorithm (i.e., particle swarm optimization (PSO)), namely PSO-SVR, for estimating PM10 concentration from drilling operations at the mine. Polynomial (P), radial basis function (RBF), and linear (L) kernel functions were considered and applied to the development of the PSO-SVR models in the present study, abbreviated as PSO-SVR-P, PSO-SVR-RBF, and PSO-SVR-L. Also, three benchmark artificial intelligence techniques, such as k-nearest neighbors (KNN), random forest (RF), and classification and regression trees (CART), were applied and developed for estimating PM10 concentration and then compared with the PSO-SVR models. Root-mean-squared error (RMSE) and determination coefficient (R2) were used as the statistical criteria for evaluating the performance of the developed models. The results exhibited that the PSO algorithm had an essential role in the optimization of the hyper-parameters of the SVR models. The PSO-SVR models (i.e., PSO-SVR-L, PSO-SVR-P, and PSO-SVR-RBF) had higher performance levels than the other models (i.e., RF, CART, and KNN) with an RMSE of 0.040, 0.042, and 0.043; and R2 of 0.954, 0.948, and 0.946; for the PSO-SVR-L, PSO-SVR-P, and PSO-SVR-RBF models, respectively. Of these PSO-SVR models, the PSO-SVR-L model was the most dominant model with an RMSE of 0.040 and R2 of 0.954. The remaining three benchmark models (i.e., RF, CART, and KNN) yielded a more unsatisfactory performance with an RMSE of 0.060, 0.052, and 0.067; and R2 of 0.894, 0.924, and 0.867, for the RF, CART, and KNN models, respectively. Furthermore, the findings of this study demonstrated that the density of rock mass, moisture content, and the penetration rate of the drill were essential parameters on the PM10 concentration caused by drilling operations in open-pit mines.

Models of simulation in the making of decisions in the mining operation

In open pit mining, the loading, unloading and hauling system can represent a high percentage of the operating cost. The objective of this document is to provide an overview of the different approaches in the application of simulation models as an alternative applied to open pit mining operations that can help in decision making to optimize resources. It talks about the different types of simulation models that can be applied in mining operations such as stochastic, deterministic and discrete events. The underlying idea of this text is to highlight that with the increase in competitiveness, mining companies are in need of using simulation techniques to reduce costs, time and risks when making decisions, since simulation allows the creation of scenarios that approximate reality. In the end, the document concludes that simulation models are a tool to help in decision-making, for the optimization of resources, increased improvement and efficiency of the processes of loading, transport and unloading in open pit mines.

Open pit mine production schedule optimization using a hybrid of maximum-flow and genetic algorithms

Production scheduling is a critical activity for the long-term production planning of open pit mining operations. It deals with the effective management of resources and maximizes cash flows to generate higher profits over the life of a mine. Production scheduling problems determine that blocks be mined and processed over a number of periods subjected to mining and processing constraints, which makes the problem more complex. The complexity is further increased due to the uncertainty in the input parameters. In this study, the maximum flow algorithm with a genetic algorithm is used to generate the long-term production schedule. The graph structure for maximum flow is created for multiple periods under uncertainty, and the flow in the arcs is controlled by a genetic algorithm to develop a production schedule. Numerical results for realistic instances are provided to indicate the efficiency of the solutions.

Turning Filling Material into Proppant for Coalbed Methane in Poland—Crush Test Results

The search for unconventional energy resources such as coalbed methane (CBM) is on the rise in Poland due to the demand for energy resources and protection of the environment. CBM production has a lower impact on the environment when compared with coal production. Its development is known to be cost effective due to its use of shallow depths with large gas quantities. Sand is one of the by-products (waste) from open-pit mining operations. Conventional disposal of this material is achieved by storage in heaps and its deployment as landfill as well as filling material for mine pits. This paper investigates the potential use of sand (filler) as a proppant for hydraulic fracturing in coalbed methane formations in Poland through crush test measurements in both single and cyclic loadings. The crush test helps to identify proppant strength under various load applications. Test results show that the sand qualifies for the 4 K (maximum allowable stress is 27.58 MPa) and 3 K (maximum allowable stress 20.68 MPa) crush classifications under single and cyclic conditions, respectively. This finding shows the viability and potential of the investigated sand as a proppant for hydraulic fracturing in shallow coalbed methane formations in Poland. Furthermore, its use could help filler-providing companies to maintain their production level and save jobs. Notably, it would contribute to the reduction of environmental problems associated with the management of waste, such as that from open-pit mining operations.

Evaluation and Risk Analysis of Open-Pit Mining Operations

Mining of raw materials is a process that consists of several stages. In open-pit mining, material with high compressive strength is extracted by drilling and blasting and material with low compressive strength is extracted by e. g. a bucket wheel excavator. Most important influencing factors for crusher decision are compressive strength, moisture content, capacity of crusher, abrasiveness, and feed size. Depending on sequence of mining, fixed, semi-fixed, semi-mobile, or fully-mobile crusher stations can be applied. Compressive strength, tensile strength, cleavage, fracture behaviour, and stickiness are the most significant influencing factors for bucket wheel excavator selection. The waste removal and dumping associated with mining must be handled very well, so that the environmental impacts are as low as possible and dump stability is guaranteed. Essential are dump foundation properties, design of dump, and construction of dump. Open-pit mining operations harbour risks which can lead to project delays, operation standstill, injury to personnel, damage to equipment, or negative impacts on the environment. Therefore, risk identification and prevention of risks is essential.