Pit Limit Research Articles

Enhancing the performance of integer models for addressing the long-term production planning problem in open pit mines by decision variable fixation based on parametric analysis of the final pit limit

Enhancing the performance of integer models for addressing the long-term production planning problem in open pit mines by decision variable fixation based on parametric analysis of the final pit limit

Ultimate Pit Limit Optimization Method with Integrated Consideration of Ecological Cost, Slope Safety and Benefits: A Case Study of Heishan Open Pit Coal Mine

The ecological impacts of mining and the instability of slopes are the key factors restricting the safe, efficient, and low-carbon production of open-pit mines. This study focused on the ultimate pit limit (UPL) optimization under the concept of sustainability by integrating consideration of the economic benefit, ecological impact, and slope geometry. The integrated UPL optimization model based on the floating cone method was proposed by establishing a quantitative model for ecological impacts arising from open-pit coal mining in arid or semi-arid weak ecological land and a cost calculation model of slope reinforcement based on the Monte Carlo method. The case study revealed that steepening the slope angle of given regions resulted in random variations in the quantity of ore rock and the limit morphology. There was an average economic profit rise of USD 9.54M with every 1° increase in slope angle, but the probability of slope instability and the reinforcement cost grows exponentially. In the arid or semi-arid weak ecological land, the ecological costs exceeded 20% of the mines’ average pure economic gains. The proposed optimization method contributes to obtaining an integrated optimal UPL, improving the benefits and the ore recovery rate.

Open pit limit optimization considering the pumped storage benefit after mine closure: a case study

Repurposing a closed mine as lower reservoir is a cost-effective way for the construction of pumped storage hydropower (PSH) plant. This method can eliminate the expenses of mine reclamation, reservoir construction, and land acquisition, resulting in significant cost savings and benefits for the PSH project, known as the PSH benefit. The construction of PSH plants within a closed mine is divided into surface mode and semi-underground mode in this paper. Through a general comparison of two in-situ cases, the finding highlight that the surface mode can achieve a larger potential installed capacity and lower construction cost. Furthermore, the PSH benefit is quantified and internalized as an economic parameter in the ultimate pit limit (UPL) optimization by allocating it into unit ore. Taken an undisclosed open-pit iron mine as example, the UPL is optimized by considering the PSH benefit. The internalized PSH benefit is calculated to be 6.59 CN¥/t when the installed capacity is 2000 MW, and ore amount within the optimized UPL is increased by 1.4%. The results indicated that the PSH benefit does influence the shape and size of UPL, but not significantly. Besides, converting several bottoms in a single open-pit into lower and upper reservoirs presents more challenges for UPL optimization, which further explorations is needed.

RANCANGAN SEQUENCE PENAMBANGAN PADA BLOK A4 PT. ADHI KARTIKO PRATAMA DESA LAMERURU KECAMATAN LANGGIKIMA KABUPATEN KONAWE UTARA PROVINSI SULAWESI TENGGARA


 Adhi Kartiko Pratama is a private company which operates in the nickel mining sector and has a Mining Business License covering an area of 1975 Ha. To maintain the company's production, currently PT. AKP plans to open a new mining location in Front Block A, especially in Sub Block A4, with a production target of 100,000 tons per month. This research aims to design a mining sequence based on production targets in Block A4. The design created is an estimated ore distribution. Minable reserves based on the mining pit limit design in Block A4 are 466,383.36 bcm with a total tonnage of 769,532.54 tons with an average Ni content of 1.76%, and including mining recovery parameters of 90%, it is 419,745, 02 bcm and a tonnage of 692,579.29 tons with an average Ni content of 1.74%, then the estimated mine life in Block A4 PT. Adhi Kartiko Pratama will last approximately 6 months. Based on the production target in Block A4, the mining sequence design is divided into 6 stages carried out using a level plan system or following excavation levels, where mining will start from topography with the highest level of 180 meters above sea level to topography with the lowest level of 135 meters above sea level.

A Genetic algorithm scheme for large scale open-pit mine production scheduling

ABSTRACT Due to the large size of open-pit mines’ long-term production scheduling (OPMPS) problem in large-scale deposits, it is challenging to solve that problem as the mixed integer linear programming (MILP) model. This study used an approach of the genetic algorithm (GA) to tackle this challenge. So, in a small hypothetical deposit, based on the blocks in the ultimate pit limit and scenarios with 2–6 phases, net present values (NPV) and computational times obtained from the GA and MILP model were compared to evaluate the GA. Also, the GA was applied to a large-scale deposit to determine the efficiency of the GA in real deposits. The maximum NPV was obtained for the four-phase scenario in the hypothetical deposit and the six-phase scenario in the large-scale deposit. Although the GA’s NPV decreased slightly compared to the global optimum solution from the MILP model, the computational time was significantly reduced.

Mine Design of Laterite Nickel Ore Based on Pit Limit Optimization with Floating Cone Method at Meranti Pit of PT Ang and Fang Brother

PT Ang and Fang Brother Site Lalampu is a nickel laterite mines company located at Lalampu Village, Morowali Regency, Central Sulawesi Province. The purpose of research is to determine the ultimate pit limit using floating cone method and calculate the net present value (NPV), to design the ultimate pit limit at Front 8 of Meranti Pit (one of the company’s fronts), to calculate the mined laterite nickel reserves and the overburden based on the pit design. The data used are block model data, topography, capital and operating costs, commodity price, density, geotechnical data, mine recovery 85%, cut-off grade 1.3%, and the company's production target of 50,000 tons/month. Data processing generates Pit Shell 9 as the ultimate pit limit with ore recovery of 264,375 tons from 284,063 tons of Front 8 resources. Based on the design using Micromine 2021 software with an area of 5.25 hectares, a total of 234,142 tons laterite nickel ore obtained by stripping 389,063 BCM of the overburden, and it still economical with stripping ratio value (1.66 BCM/ton), smaller than the BESR value (6.32 BCM/ton). The amount of nickel laterite reserves produced based on mine recovery of 85% is 199,021 tons so the life of mine lasted 3.98 months.

An Optimized Open Pit Mine Application for Limestone Quarry Production Scheduling to Maximize Net Present Value

This study involves a working limestone mine that supplies limestone to the cement factory. The two main goals of this paper are to (a) determine how long an operating mine can continue to provide the cement plant with the quality and quantity of materials it needs, and (b) explore the viability of combining some limestone from a nearby mine with the study mine limestone to meet the cement plant’s quality and quantity goals. These objectives are accomplished by figuring out the maximum net profit for the ultimate pit limit and production sequencing of the mining blocks. The issues were resolved using a branch-and-cut based sequential integer and mixed integer programming problem. The study mine can exclusively feed the cement plant for up to 15 years, according to the data. However, it was also noted that the addition of the limestone from the neighboring mine substantially increased the mine’s life (85 years). The findings also showed that, when compared with the production planning formulation that the company is now using, the proposed approach creates 10% more profit. The suggested method also aids in determining the desired desirable quality of the limestone that will be transported from the nearby mine throughout each production stage.

The effect of carbon tax and optimal slope profiles on profitability and emissions of open pit mines

ABSTRACT This paper investigates the financial and environmental consequences stemming from the introduction of a carbon levy applied to mining and processing activities. The novelty is twofold: (1) the effect of a carbon tax, proportional to the emissions produced by all relevant mining activities, is accounted for in the determination of the Ultimate Pit Limit (UPL), i.e. the environmental costs are not applied a posteriori to pit optimization but included concurrently to Net Present Value (NPV) maximization, allowing to investigate the relationship between carbon tax value versus NPV, amount of ore extracted and carbon emissions; (2) we use a new software, OptimalSlope, to automatically determine geotechnically optimal profiles for the mine pitwalls. The Marvin copper deposit (block model data publicly available from MineLib repository) was adopted as a case study. Several pit optimizations were performed based on four different values of carbon tax and adopting either traditional planar or non-linear optimal pitwalls. It emerges that the relationships between carbon tax value versus NPV, amount of ore extracted, and carbon emissions exhibited linearity in both cases of planar and optimal pitwall profiles. Moreover, the adoption of optimal profiles realizes gains up to 215 million AUD, without compromising the safety of the UPL.

PIT Design Area 206 Ha at PT Semen Padang Indarung

PT. Semen Padang is a mining company engaged in quarry (limestone) mining. The company is located in Bukit Karang Putih – Indarung, Padang City. Mining in this company uses the Type Side Hill Quarry system. For production in the 206 Ha mining area using a combination of mechanical devices in the form of Excavators and Dump Trucks. With supporting tools in the form of a D9R Bulldozer and a GC-02 Motor Grader. The target of this activity is to optimize mining production in the 206 Ha pit area. Efforts were made to optimize mining production in the Exit Area and PIT Limit from 2014 – 2016 by combining Excavator and Dump Truck mechanical devices to the crusher loading area with a volume of 24,872,835 tons, 28,304,505 tons and 26,029,609 tons. Whereas in 2017 – 2020 only the PIT Limit area will carry out mining production, this is because the reserves in the Existing area have run out. PIT Limit production from 2017 – 2020 is 21,864,874 tons, 20,981,407 tons, 20,831,837 tons, and 20,662,775 tons.

Technical Blasting and Ripping of Overburden to Reduce the Effect of Ground Vibration on Slope Stability and Residence around Coal Mine

The coal mining method at the West Banko Pit 1 North is carried out in an open pit using a shovel-dump truck system. The overburden consists of topsoil and claystone with a strength of 0.2 – 3 MPa. The digging force of the Komatsu PC 2000 excavator is 0.697 MPa, so to optimize the productivity of the excavator, it must be carried out using a Komatsu D375A ripper and blasting. Considering that the pit limit in the west is close to residential buildings, it is necessary to design the mining area to be ripping and the area to be blasted as well as blasting technical design to reduce the impact of ground vibration on slope stability and damage to buildings in residential areas around the mine. Based on the results of the analysis of overburden blasting at the West Banko Pit 1 North on the stability of static and pseudo-static slopes with the simulation of the optimal Berm, the maximum Berm is 12 m with a safety factor (SF) of 1.5, while the overburden blasting was based on research at West Banko pit 2 because the material conditions were relatively the same. The number of safe explosives for predicting the Peak Vector Sump (PVS) value 3.5 mm/second is 50 Kg/ Delay with a minimum distance of 500 m from residential areas. The analysis results of the area to be blasted are 112.59 Ha, and the area that remains ripped is 134.04 Ha.

Open Pit Optimization Using the Floating Cone Method: A New Algorithm

Three-dimensional block models are the most frequently used tool for estimating mineral resources and reserves within a mineral deposit. In open pit mining, the basis of mine design and the long term mining schedule is calculation of the ultimate pit limit. The ultimate pit limit is the pit with the highest profit value. Over the years, different algorithms have been developed that enable us to calculate the final pit: floating or mobile cone, floating cone II and its corrected forms, floating cone III, the Korobov algorithm and its corrected form, the Lerchs–Grossmann 2D algorithm (dynamic programming), and the Lerchs–Grossmann 3D algorithm (graph theory). All these algorithms have advantages and disadvantages. The floating cone method stands out for its simplicity, speed, and easy implementation, even for calculating a pit with a variable slope angle. The main drawback of this method is that it is unable to examine all possible combinations. For this reason, the algorithm does not consistently give optimal results, which is why it has required improvements over time. However, the improved methods still have some problems. To overcome these problems, a new algorithm called the floating cone IV method will be demonstrated in this paper.

Mining design and short-term production scheduling by using 3D modeler in Coal mining at PT. Internasional Prima Coal, Palaran District, Samarinda City, East Kalimantan Province

PT. International Prima Coal is a subsidiary of a combination of two companies, namely PT. Bukit Asam (Persero) Tbk and PT. Mega Raya Kusuma which is engaged in coal mining in East Kalimantan, with an area of 3,238 hectares of Mining Business Permit in Bantuas and Handil Bakti Villages, Palaran District, Samarinda City which is planning to open a new block, namely North Eagle 3 block for the sustainability of coal production. This is the background for the author to research mining design and production schedule. This study aims to analyze resources and reserves, design mining, determine the combination of tools and monthly production scheduling. The research method used is qualitative and quantitative methods. the quantitative method will produce data such as the value of resources and reserves, slope geometry, SR (Stripping Ratio), and the amount of production per month. The qualitative method will produce data such as haul road designs, mining methods, mining sequences. Based on the results of modeling of coal deposits in the northern pit eagle 3 has 3 seams (Q050, Q070, Q080) with a total measured resource calculated by the polygon method is 726,898 tons. The design of the mining pit limit at an elevation of 0 masl is the contour of the Q070 seam structure with a total coal reserve of 66,516 tons and OB 651,952 bcm with SR 10. The haul road is made of 2 lanes with a straight road width of 9 m and a bend road width of 18 m. The form of drainage that is made is a channel with a trapezoid shape and a settling pond. The mining method used is open pit with down-dip excavation. Mining sequences and production schedules are divided into 4 mining sequences to obtain a production target of ±16,000 tons/month.

Assessment of energy conservation potential and cost in open-pit metal mines: Bottom-up approach integrated energy conservation supply curve and ultimate pit limit

Mitigating energy consumption and greenhouse gas (GHG) emissions in the metal mining industry heavily depends on the employment of energy conservation technologies in each individual metal mine. However, predicting the energy conservation potential and associated cost for a specific mine is difficult, especially considering the interaction between technology employment and open-pit limit variation. Therefore, this study integrates the conventional energy conservation-supply-curve (CSC) approach with the ultimate-pit-limit (UPL) analysis in the estimation of energy conservation potential and cost due to technology application. The results from the case study show that conventional CSC analysis provides overestimated potential with underestimated cost under market-based promotion policy. On the other hand, a target-responsibility-system-based (TRS-based) provides underestimated potential with overestimated cost. Sensitivity analysis shows that energy price has the largest impact on the energy conservation potential and associated cost. The policies that raise energy and carbon prices contribute not only to mitigating energy consumption, but also to reducing associated costs, even though they are accompanied by a reduction in mineral supply. This study suggests that the policy that subsidizes conserved energy should be integrated with a TRS-based policy to mitigate the elimination of energy conservation potential due to expansion of the open-pit limit.

Stochastic Final Pit Limits: An Efficient Frontier Analysis under Geological Uncertainty in the Open-Pit Mining Industry

In the context of planning the exploitation of an open-pit mine, the final pit limit problem consists of finding the volume to be extracted so that it maximizes the total profit of exploitation subject to overall slope angles to keep pit walls stable. To address this problem, the ore deposit is discretized as a block model, and efficient algorithms are used to find the optimal final pit. However, this methodology assumes a deterministic scenario, i.e., it does not consider that information, such as ore grades, is subject to several sources of uncertainty. This paper presents a model based on stochastic programming, seeking a balance between conflicting objectives: on the one hand, it maximizes the expected value of the open-pit mining business and simultaneously minimizes the risk of losses, measured as conditional value at risk, associated with the uncertainty in the estimation of the mineral content found in the deposit, which is characterized by a set of conditional simulations. This allows generating a set of optimal solutions in the expected return vs. risk space, forming the Pareto front or efficient frontier of final pit alternatives under geological uncertainty. In addition, some criteria are proposed that can be used by the decision maker of the mining company to choose which final pit best fits the return/risk trade off according to its objectives. This methodology was applied on a real case study, making a comparison with other proposals in the literature. The results show that our proposal better manages the relationship in controlling the risk of suffering economic losses without renouncing high expected profit.

Open pit limit optimization considering economic profit, ecological costs and social benefits

Pit limit design has, up to date, focused mainly on maximization of economic profit alone, with environmental and social issues largely ignored. This paper focuses on incorporating both environmental and social issues in the pit limit design process and provides an approach to pit limit optimization that is in compliance with sustainable development. The case study demonstrates that ecological costs have a substantial down-sizing effect and social benefits have a substantial up-sizing effect on the optimal pit limit. When the ecological costs are factored in, the optimal pit limit is 37.5% smaller than the economically optimal pit limit. However, when the social benefits are factored in, the optimal pit limit is 48.3% larger than the economically optimal one. The overall optimal pit limit, with the economic profit, ecological costs and social benefits simultaneously considered, is a result of balancing conflicting goals of maximizing economic profit, minimizing ecological cost, and maximizing social benefit.

Determination of the optimal transition point between a truck and shovel system and a semi-mobile in-pit crushing and conveying system

One of the most challenging aspects in semi-mobile in-pit crushing and conveying (SMIPCC) system design is determining the optimum depth at which to change from a purely truck-based haulage system to a conveyor-based haulage system. We used scenario analysis to determine the optimum transition depth between a truck and shovel (TS) system and a SMIPCC system. Traditional pit-limit algorithms were used to generate the final pit limit on a copper deposit, which was then divided into four pushbacks. The final operating pushbacks (phases) were designed for both TS and SMIPCC. The end depths for each phase are viewed as candidate transition points to switch from the TS to SMIPCC haulage system. Economic calculations were applied for five different scenarios, including adopting SMIPCC from the outset (pure SMIPCC), after the first, second, and third phases, and finally not using the SMIPCC system (pure TS) at all. The analysis indicates that the second scenario, at a depth of 335 m, results in the lowest cumulative discounted cost (CDC). In this case, the CDC is 17.6% lower than that for the pure TS scenario and 10.7% lower than for the pure SMIPCC system scenario.

Ultimate Pit Limit Determination Using Flashlight Algorithm

In this paper, the flashlight (FL) algorithm, which is categorized as a heuristic method, has been suggested to determine the ultimate pit limit (UPL). In order to apply the suggested algorithm and other common algorithms, such as the dynamic programming, the Korobov, and the floating cone, and to validate the capability of the proposed method, the ultimate pit limit was determined in a cross-section of the Korkora reserve, which is located in Kurdistan province, northwestern of Iran and consists of 3080 blocks. The comparison of the FL algorithm and other methods revealed that same as high accuracy dynamic programming methods, the proposed algorithm could find the optimum value, while the Korobov and the floating cone algorithms failed to determine the optimum limit.

Muruntau gold mining and refining operation: Resources, expansion program and future considerations

The international geological community has acknowledged Muruntau gold deposit as the greatest discovery in the mid-to-late 20th century. Muruntau mine field holds the total appraised resource potential of more than 4.5 thousand tons of gold. Hydrometallurgical plant GMZ-3 implements gold-ore processing by gravitational sedimentation and adsorption. The technological and instrumental modernization of the gold processing circuit toward its higher capacity, gold recovery and thoroughness are the important aspects of production improvement and cost reduction. The developed and introduced ore milling flowchart provides replacement of the second milling stage pumps by higher-capacity pumps backed up with additional cyclones. Aiming to ensure stable gold production at plants GMZ-2 and GMZ-3, Navoi MMC’s experts accomplished the feasibility study of mining operations in Chukurkuduk and Turbai deposits in 2020. The growth prospects for open pit mining in Murunatu–Myutenbai fields after 2060 are estimated using the model of optimized ultimate pit limit design at the gold price of USD 1500/t. The model ultimate pit limit embraces all probable reserves as per the detailed 2D seismic data as of early 2020, including proven reserves intended for open pit and underground mining. The gold ore appraisal and the expansion program elaborated for Muruntau gold mining and refining integrated works in joint Muruntau–Myutenbai field, through implementation of operation phases V and further make it possible to forecast stable performance up to 2030–2050.

Impact of blasting on pit wall rock mass

The paper presents the research findings obtained by the Institute of Mining in drilling and blasting in Dzhetygara open pit mass. The research was aimed at enhanced stability of stationary benches and at cost minimization of drilling and blasting. The research met two objectives. First, in terms of Dzhetygara deposit, perimeter blasting designs were developed, which ensured reduced impact of blasting on adjacent rock mass. Second, the blast-induced PPV measurement procedure was refined and introduced, and the blasting technology was improved for blasting operations at ultimate pit limit. The special technology for ultimate pit perimeter blasting includes: analysis of blast effects on pit wall rock mass; finding of mechanisms of wave processes in rock mass; interaction of perimeter blasts depending on strength characteristics of rock mass; field trial of cutback methods; determination of sequence of blasts when approaching a guarded sites; determination of efficiency criteria of drilling and blasting.

A Framework for Open-Pit Mine Production Scheduling under Semi-Mobile In-Pit Crushing and Conveying Systems with the High-Angle Conveyor

In-pit crushing and conveying (IPCC) systems have drawn attention to the modern mining industry due to the numerous benefits than conventional truck-and-shovel systems. However, the implementation of the IPCC system can reduce mining flexibility and introduce additional mining sequence requirements. This paper investigates the long-term production scheduling and the crusher relocation plan of open-pit mines using a semi-mobile IPCC system and high-angle conveyor. A series of candidate high-angle conveyor locations is generated around the pit limit, with a crusher located along each conveyor line. Each conveyor location is solved independently by an integer linear programming model for making production scheduling and crushing station decisions, aiming to maximize the net present value (NPV) considering the material handling and crushing station relocation costs. The production schedule with the highest NPV and the associated conveyor and crusher location is considered the optimum or near-optimum solution.