Deep Open Pit Research Articles

Изменение подхода к проектированию горнотехнических систем при открытой разработке месторождений на базе совершенствования принципов управления качеством горной массы

The main effect in transition of deep open pits to the In Pit Crushing and Conveying (IPCC) system of rock mass transportation is achieved through cutting the costs of rock mass hauling. Independence of the transportation system throughput from the haulage distance makes it possible to increase the boundary stripping ratio and extend the service life of the open pit. Transition from the cyclic to the In Pit Crushing and Conveying (IPCC) system of rock mass hauling still leaves insufficiently studied the issues related to assessment of the minimum commercial and cut-off grades of valuable components and contaminants in ores, the permissible thickness of the ore bodies when justifying the feasibility study of conditions, as well as management of the rock mass flow quality, optimization of the rock mass reduction ratio at the stage of its preparation for conveyor hauling from the open pit to the ore stockpiles and, further, to the ore hoppers of the processing plants, and many other challenges. The paper systematizes the results of other research by the authors as well as other data and it shows that the placing the crushing equipment and the belt conveyors within the boundaries of the open pit offers additional opportunities to manage the quality of rock mass flows, i.e. the ore mass and the overburden due to variations in the logistic and hauling schemes of the open pit due to transition to the In Pit Crushing and Conveying (IPCC) system. The above approaches to implementation of the rock mass haulage system in open pits remove the boundaries between mining and processing of minerals, expand the possibilities of targeted formation of technogenic deposits, and potentially expand the range of marketable products of the mining company. In fact, the mining and processing facility is considered as a unified technological process of the complete production cycle carried out in a single technological environment. Implementation of the proposed technological schemes will require changes in the regulatory and legal framework.

Multi-criteria analysis of deep pits sustainable development strategy

Relevance. Long periods of development of steeply dipping deposits necessitate multiple adjustments of mining and technical system throughout an open pit life cycle. The decisions made determine the development strategy of a mining enterprise for a long period. The complexity of making such strategic decisions depends on numerous influencing parameters. These parameters have a different impact, have a variety of units of measurement, target values, and are not only quantitative but also qualitative. There is a need for new approaches to the choice of development strategy of the mining and technical system of an open pit, as well as its main subsystem – the opening-up of an opencast system. It is proposed to base these approaches on multi-criteria decision-making methods that consider many influencing parameters. Aim. Development of a methodology for choosing a strategy for sustainable development of the deep open pit mining and technical system based on multi-criteria decision-making methods and assessment of the opening system parameters. Objects. Mining enterprise, mining and technical systems, opening system. Methods. Literature review, system analysis, multi-criteria decision making. Results. The authors have determined the main strategies for development of the mining and technical system for deep open pits. These strategies aim at achieving the sustainable development of the mining and technical system: adjustment of the current stage mining parameters; transition to a new stage of mining; transition to a combined open-underground mining; mine closure. The key role of the opening system in the structure of the mining and technical system is substantiated to ensure its sustainable development. The authors systematized the main parameters for evaluating the pit opening system and set target values for each parameter. A review of the main multi-criteria decision-making methods used to solve various problems in the mining industry is made. A rank coefficient is proposed for choosing the mining and technical system development strategy. The calculation of this coefficient is based on a combination of the fuzzy AHP and CRADIS multi-criteria methods. A method was developed for selecting a strategy for sustainable development of the mining and technical system of deep open pits. A case study was conducted on the conditions of the Maly Kuibas open pit. The obtained results strongly suggest that the best strategy with the highest ranking is the transition to the combined development method.

Комплексный анализ результатов мониторинга устойчивости уступов карьера с использованием геофизических методов исследования

The Response to challenges related to safety in open-pit mining of mineral deposits is based on continuous monitoring of the pit wall stability as a whole as well as the stability of problematic areas of the pit wall and individual benches. Control of the geomechanical state of the adjacent rock mass using local geophysical methods plays an important role in the overall monitoring of stability of the open-pit elements. The control allows studying in more detail the state of benches and groups of benches in critical areas of the open-pit and developing measures to ensure production safety on this basis. One of the main interdependent factors affecting the pit wall stability is, on the one hand, the size of the disturbed zone that depends on both natural and mining-induced rock fracturing; on the other hand, the level of ground water changing over time depending on the season. The importance of joint account of the factors above has stipulated to propose a comprehensive methodical approach to study water saturation and structural disturbance of rocks in the wall of a deep open-pit. The method consists in periodic, seasonally synchronized, geophysical studies using seismic profiling and GPR sounding and allows identifying the areas of high water saturation and disturbance in the adjacent rock mass. The methodological approach makes it possible to estimate the effect of the main time-varying impact factors (water saturation, natural and mining-induced disturbance, anomalies of physical properties of the rock mass) on the slope stability and provides a scientific and technical basis for developing engineering measures to improve the safety of deep open-pit mining.

Stability analysis of a deep and large open pit based on fine geological modeling and large-scale parallel computing: a case study of Fushun West Open-pit Mine

Accurate input of geological elements is essential for evaluating or predicting natural hazards such as subsidence, landslides, and earthquakes. This paper proposes an approach to carry out an open pit’s overall and whole-process mechanical analysis with complex geological conditions, using precise modeling and large-scale parallel calculation techniques. Taking the Fushun West Open-pit Mine (the largest open-pit coal mine in Asia) as an example, through the elaborate multi-method geological investigation, the interfaces of interbedded shales and mudstones, the unloading zones, and the small structures were identified, a detailed 3D geological model was built and finely meshed in full-size with 100 million degrees of freedom, large-scale parallel numerical simulation was then performed, the results agree well with the InSAR monitoring data and in situ observations. Besides, the simulation can replicate the landslides in recent years. Through the simulation, it is possible to locate the potential landslide area, and targeted backfilling schemes for stability treatment were put forward and further simulated. The results indicate that the proposed approach can more effectively and reliably evaluate the Fushun West Open-pit Mine’s overall slope stability and closure plan.

Influence of Recirculation Flow on the Dispersion Pattern of Blasting Dust in Deep Open-Pit Mines.

The recirculation within a deep open-pit mine is a significant factor contributing to the deterioration of the atmospheric environment. However, the underlying mechanisms of how recirculation influences the dispersion pattern of dust clouds within the deep open-pit mine have not been clearly elucidated. In this research, the dispersion patterns of blast dust clouds were investigated in a deep open-pit mine located in northern China. This research initially conducted a similar experiment to verify the existence of recirculation flow in the experimental mine, which can cause dust particles to aggregate toward the upwind slope. In response to the dust pollution issue in deep open-pit mine blasting operations, this study conducted a numerical simulation analysis based on on-site measurement data to investigate the effects of varying natural wind velocity, natural wind direction, and blast location on the diffusion pattern of blasting dust. The results indicate that natural wind velocity (v), natural wind direction (α), and blast location (d) affect the distance between the blast location and the recirculation center point (Drecir), subsequently influencing the diffusion pattern of blasting dust. The recirculation flow effect influences the diffusion of dust toward the upwind slope under smaller Drecir values, leading to widespread and long-term pollution within the mine. Under larger Drecir values, dust diffuses toward the downwind slope with the straight flow of wind, resulting in less pollution within the mine. Through orthogonal experiments, the equation Drecir = -120.61v2 + 237.27v + 0.82d - 0.07α2+ 6.75α + 151.08 was established in this deep open-pit mine, which provides a basis for predicting the diffusion pattern of blasting dust and control strategy in this deep open-pit mine.

Determining the Safe Distance for Mining Equipment Operation When Forming an Internal Dump in a Deep Open Pit

In the surface mining of mineral deposits, land resources suitable for agricultural purposes are inappropriately spent in large volumes. When mining deep open pits, overburden rocks are mainly transported to the surface. The optimal solution for reducing the area of disturbed lands is the placement of overburden rocks in internal dumps in the open pit. This is especially suitable when mining a mineral deposit with several open pits where at least one of them is depleted. Therefore, it is important to assess the feasibility of building an internal dump, based on the stability parameters of its slopes and the safe distance for placing mining equipment within its boundaries, which was the focus of this research. Numerical modeling with Slide 5.0 software was used to determine the stability of the dump slope inside the open pit and the safe distance from the upper slope edge for placing mining equipment. This reflected the geomechanical situation occurring within the boundaries of the dump formed in the open-pit field with a high degree of reliability. It was determined that the maximum standard safety factor values of the open-pit slopes are within the limits when the overburden rocks border on the hard bedrock (Ks.s.f ≥ 1.2). Under the condition where the dump slope bordered on sedimentations represented by clays, loams, and sands with a strength of 2–3 on the Mohs scale, the safety factor decreased by 22%. It was determined that the minimum safe distance from the outer contour of the dragline base to the upper edge of a single-tier dump was 15.5 m with a safety factor of 1.21. The maximum safe distance values in the range of 73.5–93 m were concentrated within the boundaries of sections 5–9, with a safety factor from 1.18 to 1.28. When the dragline was located within the boundaries of section 7, the dump construction works should be conducted only if the dump exist for up to 3 years. Based on the identified parameters, on the example of using the ESH-11/70 walking dragline, a technological scheme of its operation was developed with the allocation of safe boundaries for its placement when forming an internal dump. The results obtained are useful for the development of projects for the reclamation of depleted open pits.

Technical and technological solutions regarding the development of pillars during final mining of deep open pits

When mining operations achieve the total depth of open pits within their boundaries, a significant share of balance ore reserves remains in pillars under transport communications as well as under reloading points. Liquidation of the available transport communications should follow by the development of the new ones. Hence, mining stages of a steep-grade field and periodicity of a pillar initiation within both working open pit flank and temporarily nonworking one have been studied. Нannivskyi open pit has been taken as an example to substantiate the expediency to extract balance reserves occurring under crushing and reloading point within ±0 m level. The substantiation of technical and technological solutions concerning the development of a protective pillar involved cuts of geological ore formation which supported the idea of availability of the preserved reserves and topicality of the selected problem. Operation schedules to mine the pillars have been developed for general conditions; the required equipment set has been analyzed. New technological solutions have been obtained using current excavating and transportation machinery. Engineering solutions as for possibility to open the pillars and liquidate them in terms of the limited technical and technological potential have been substantiated. The technological schemes of pillar mining have been systematized depending upon the technological processes, taking place in the open pit, and the applied equipment set. Scientific significance of the paper is the developed systematization of facilities in terms of operation schedules of pillar mining. Practical significance is the developed operation schedules to mine and liquidate the pillars. Technical and technological expediency to use skip hoist while reactivating temporarily nonworking open-pit walls for rock mass transportation from the pillars up to the surface has been substantiated. It has been proved that during final mining operations in an open pit, complicated by difficulties in electricity delivering to the preservation pillar, it is expedient to apply loaders in one operation schedule. Use of loaders and skip hoist to mine the preservation pillar is the optimum strategy. It has been substantiated that the proposed procedure is more advantageous to compare with the conveyor transport.

Probabilistic assessment of slope stability at ore mining with steep layers in deep open pits

Purpose. A methodology development for predicting the geomechanical situation when mining an ore deposit with steep-dipping layers, taking into account the uncertainty in determining the rock properties, which is a consequence of the rock mass heterogeneity. Methods. The assessment of the open-pit wall stability is based on a combination of numerical simulation of the rock stress-strain state (SSS) and probabilistic analysis. The finite element method is used to determine the changes in the SSS that occur at various stages of mining operations due to design changes in the overall open-pit slope angle. The elastic-plastic model of the medium and the Mohr-Coulomb failure criterion are implemented in the codes of the 3D finite element analysis program RS3 (Rocscience). Stochastic simulation is used to assess random risks associated with natural object state variations. Findings. The distribution of maximum shear strains, which localizes the real or potential sliding surfaces in the open-pit wall at various stages of ore mining, has been identified. Based on the Shear Strength Reduction procedure, the open-pit wall Strength Reduction Factor (SRF) has been determined. The probabilities of open-pit wall stability loss, as well as the decrease in the strength reduction factor below the standard level at all stages of the ore body mining, have been revealed. Originality. For the first time, for real mining-geological conditions of a deep ore open pit, the dependence of the strength reduction factor on the overall wall slope angle, which changes during mining of each steep layer, has been determined. For each stage of mining operations, for the first time, the probability of a decrease in the open-pit wall stability below the standard level has been determined based on stochastic simulation. Practical implications. The ratio between the open-pit contour characteristic (overall slope angle) and the probabilistic safety factor is the basis for practical solutions to ensure the efficiency and safety of mining at various stages of friable and hard overburden excavation, ore extraction, as well as for the subsequent optimization of the open-pit design contours.

Substantiation and development of innovative container technology for rock mass lifting from deep open pits

Purpose. The research purpose is to substantiate the rational parameters of innovative container technology for transporting mine rocks in open pits with account of technological advantages. Methods. The winding machine normal operation was determined by calculation performed. The container metal structure was designed in the environment of the Compass-3D software complex. The structural elements were tested for normal operation using computer modeling methods in the APM WinMachine 9.7 program, which gives the possibility to obtain the strength calculation values. Findings. The results of modeling the stresses on the wall of the container and the frame, as well as the yield strength are presented. The test calculation confirms the technical feasibility for operating the dragline-based mine winding machines. The influence of the container capacity on the performance of the winding machine has been determined and the dependence of the economic efficiency of the container technology introduction at the open pit depth has been revealed. Originality. For the first time, on the basis of computer modeling, the parameters of stress distribution on the container wall have been substantiated when performing a strength calculation. It has been determined that the maximum stress in the container wall is 117.52 N/mm2; the principal stress value is 83.85 N/mm2. The safety factor for yield strength is 1.8. The maximum load acting on the structure is 957.5 kgf, which does not exceed the calculated value. Practical implications. The practical importance is to improve mining efficiency, reduce the cost of transporting rocks and ensure automatic container unloading. The use of replaceable containers in open pits can significantly change the formation principles of shovels and transport complexes, increase their performance and the efficiency of shovels in the main processes.

Features of using equipment for in-pit crushing and conveying technology on the open pit walls with complex structure

Purpose is to substantiate the use of an in-pit crushing and conveying technology at the open pits with complex structure of the working zone, which technological complex includes inclined and steeply inclined conveyors for improved economic efficiency of mineral mining at deep levels. Methods. The study applies a complex method including: technical-economical analysis of the practice of mining enterprises, experience of using conveying units at concentration plants and open pits; mining-geometrical analysis in terms of open pit sections – to identify the structure of the working zone of a deep open pit wall and its features along the depth; structural developments – to improve the design of a steeply-inclined conveyor; simulation modelling of the technological processes – to select optimal technical solutions. Findings. Basing on the performed studies, it has been identified that transfer to a new trend of the in-pit crushing and conveying technology, considering the structural features of the working zone of a deep open pit, is rather prospective. In this context, it is expedient to use inclined conveyors or deep-trough conveyors on the sites of an open pit wall with the inclination angle of 10-18°; in case of sites with the inclination angle of 30-36°, it is recommended to use steeply inclined conveyors. Originality. For the first time, a relation between the working zone of a deep open pit and formation of the structure of technological complexes has been identified. Dependences of the boundary inclination angle αn of a pipe conveyor on the angle of non-filling θ of its belt with the cargo at different coefficients of cargo-belt friction have been defined. Practical implications. The obtained results make it possible to widen the application sphere and increase the efficiency of mineral mining with the use of in-pit crushing and conveying technology.

A technology for non-mining flanks formation at deep kimberlite open pits

Research objective is to develop a technology for non-mining flanks formation at deep open pits to reduce the amount of stripping operations and increase the scope of diamond fields mining by the open-pit method. Research relevance. The non-mining flanks formation and reduction of their additional excavation from the main openings is one of the most pressing problems in the development of deep kimberlite open pits. In the deep zone of kimberlite open pits, the stable slope of the flanks can reach 75°–80°, while according to the condition of ramps placement it is 48°–60°. This results in increased overburden volumes and limits the maximum depth of open pits. Methods of research. A technology has been developed for forming non-mining flanks and giving them a convex (cissoidal) profile with a gradual increase in slope angles. The technology consists in phased transition starting from a certain depth from the traditional overburden removal method to one with steeply inclined ramps and a spiral marginal tunnel passing behind the shear zone. A method for calculating the design angles of non-mining flanks when opening deep quarries with spiral ramps is substantiated. The main regularities of opening parameters effect on the slope angle of non-mining flanks are established. The results of experimental studies of rock physical and mechanical properties are used, as well as the methods of economic and mathematical modeling and technical and economic analysis. Results. By the example of Nyurba mine of Alrosa PJSC, it was found that the proposed technology allows increasing the resulting angle of non-mining flanks from 45°–48° to 54°–63°, reducing the amount of overburden removal operations by 3–8 times and effectively mining the open pit to a depth of 750 m corresponding to the depth of explored reserves. Scope of results. The proposed technology and method for calculating the design slope angles of non-mining flanks can be used not only in kimberlite open pit development, but also in the development of non-ferrous and precious metal deposits, represented by steeply dipping rounded deposits, by the open-pit method.

Substantiation of parameters and efficiency of sandwich belt high angle conveyors for deep open pit mines

The article focuses on substantiation of such parameters of heavy-duty sandwich belt high angle conveyors as the belt width to ensure operation without spillage of load, and the hugging pressure with regard to its dependence on the angle and length of the conveyor. It is noted that incorrect estimation of these parameters can lead to the redistribution of forces between the conveying and hugging belts with increasing load applied on the conveying belt. The economic efficiency of the high angle conveyors is considered in comparison to the traditional belt conveyors. It is shown that the cost of a traditional belt conveyor jumps with the increasing height of hoist. It is shown that the operating costs of the sandwich belt high angle conveyors increase almost linearly with an increase in the hoisting height and very slightly depend on the conveyor angle.

Assessing technical capacities and economic efficiency of granulated middling hydraulic transportation as applied to Kursk Magnetic Anomaly deposits development

Introduction. The majority of iron ore open pits in Russia and the CIS belong to the category of deep open pits, same as prospective Kursk Magnetic Anomaly (KMA) deposits (Prioskolskoye, Chernyanskoye, Pogrometskoye, etc.) with the thickness of overburden equal to 100–150 m where the open pits will be deep already at the early stage of mining operations. Research objective is to provide rationale for hydraulic transportation advantage over other types of industrial transport and identify technical capacities and economic efficiency for a new scheme of opencasting and transport of promising fields of KMA at the stage of the pre-project development. Research objects are Prioskolskoye and Chernyanskoye deposits. The main methods of research were the graphic method, graphic-analytical method and method of technical and economical comparison of different options. The basis of the proposal for development of the prospective KMA deposits is a new layout of the industrial site of a miningand-processing facility with location of parts of the crushing and grinding complex in the open pit and hoisting of ore in the form of pulp to the surface by pipeline transport for further beneficiation. Results. In general, the prefeasibility study involving the technical and economical comparison of two prospective KMA deposits shows cost savings with regard to ore transportation from the open pit to the industrial site by hydraulic transport compared to the cyclic-flow technology. The new technology enables reduction of the transportation costs by 1,5–2 times and increase in labour productivity with regard to ore transportation by 2–3 times.

Обоснование оптимального уклона крутонаклонных автосъездов для полноприводных автосамосвалов, эксплуатируемых при доработке алмазорудных месторождений

At present, the design depth of open-cast diamond (kimberlite) mines is increasing through introduction of advanced technologies and new mining and transportation equipment. In 2008-2012 the Yakutniproalmaz Institute and the Institute of Mining developed scientific and methodological principles and design solutions for development of the Udachny and Botuobinsky deep open pit mines using steeply inclined ramps and the CAT-740B articulated dump trucks with the capacity of 39.5 tons. Research was conducted to determine the rational slope for articulated dump trucks in the Udachny open pit and to develop guidelines for safe operation of such dump trucks on steep inclines. The performed experiments demonstrated the ability of articulated dump trucks to safely haul rocks with loads that were close to the nominal capacity using ramps with the slope gradients up to 24% in various weather conditions. In spite of a sufficiently large number of studies on justification of parameters of developing deep open pit levels, many questions still require additional research. This is primarily explained by the limited experience of operating articulated dump trucks in Russian deep open pit mines. In this context, the issue of justifying the optimal slope gradients for all-wheel drive models of motor vehicles remains relevant. The authors of the article have analyzed the existing normative documents and methods to determine the rate of longitudinal slopes. As the result of the study, the physical criterion of the least action is proposed as the optimization criterion for the slope gradients of the in-pit roads when operating all-wheel drive dump trucks.

Economic evaluation of materials handling systems in a deep open pit mine

Economic evaluation of materials handling systems in a deep open pit mine

Economic evaluation of materials handling systems in a deep open pit mine

Economic evaluation of materials handling systems in a deep open pit mine

Development of cyclic-flow technologies at high-performance deep open pits with dynamic working area

Development of cyclic-flow technologies at high-performance deep open pits with dynamic working area

OPTIMISATION OF LOCATION AND PERFORMANCE PARAMETERS FOR THE CRUSHING AND TRANSFER STATIONS IN THE DEEP OPEN PIT MINES

When designing the strip mining methods at the deep open pits at the stage of preliminary studies, it is necessary to determine the optimum number and succession of relocation of crushing and transfer stations while developing the open pit. This cuts the transport costs and reduces the number of dump trucks required. An analytical dependence has been established to determine the optimum number of transfer points with their uniform location along the length and height of the open pit working area. The features of changes in the basic technological parameters of truck operation, depending on the number of crushing and transfer stations, the open pit size and output are studied. The conditions for simultaneous use of several crushing and transfer stations, their optimum number and performance have been determined; the economic benefits of using the flowcharts with multiple transfer points have been estimated. Optimisation of the number of transfer points reduces the required capacity of each crushing and transfer plant of up to 10-20 million tons/year. Reducing the required capacity of transfer points makes it possible to equip them with primary jaw crushers.

Effect of the Minor Principal Stress on Crack Initiation Stress Threshold

The rapid expansion of urban and mining infrastructures worldwide over the last two decades has seen an escalation of development in hard rock, including urban tunnels, deep open pits, and underground mines. However, despite many success stories, the pervasiveness of rock burst and spalling remains yet a major unresolved ground control problem in many deep mines and tunnels. Spalling is characterised as a sudden explosion-like rock failure that occurs spontaneously and could affect both the short-term and long-term viability of mining operations. Previous studies strongly show that the spalling strength in low-porosity rocks can be associated with the initiation of internal cracks in the sample. However, very limited studies are available that looks at the effect of all the principal stresses on rock crack initiation stress threshold. This paper investigates the previously ignored effect of the minor principal stress on the crack initiation stress level of sandstone cubes tested under true triaxial loading conditions. The results reveal that the minor principal stress has a profound effect on the crack initiation point. As a result of this study, a new crack mode-changing stress (CMCS) concept is also introduced which is defined as the corresponding minimum principal stress required to change rock fracturing from splitting to a sliding failure mode.

Изменения атмосферного давления как неблагоприятный фактор работы в глубоких карьерах

The need in considering changes (including sharp) of the atmospheric pressure during the operation of deep open pits as one of the unfavorable factors is substantiated. It is believed that the atmospheric pressure in a particular region varies slightly-within 30–40 mm Hg per year. But at the present time, when only in Russia there are five open pits with a depth of 500 m and more, it is impossible to ignore changes in the atmospheric pressure in relation to workers moving, for example, by motor transport, from the surface to the bottom of the open pit and back. In this case, it can change by 50 or more mm Hg in half an hour. To solve the related problems, it is required to find out how atmospheric pressure affects the blood pressure of the open pit workers. The experience of the Dead Sea Clinic located in Israel at the Dead Sea at a depth of more than 400 m below the sea level is taken as a basis. Long-term measurements of the blood pressure in patients of the clinic revealed a tendency to decrease it by an average of 10–20 mm Hg. To prevent the adverse effect of a sharp change in the atmospheric pressure on people working in deep open pits, it is required to provide for appropriate measures of a different nature: technological (provide for changes in the characteristics of the open pit roads to ensure smoother descents and ascents of the dump trucks); technical (use of the conveyor and combined transport); organizational (including changes in the work and rest regimes of the working employees); regulatory (amendments to the relevant safety rules and other normative documents). To apply the results obtained in the open pit mining, it is necessary to conduct appropriate research in the operating deep open pits.