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By Enrique Rubio Esquivel, Matías Fuentes Bustamante

The transition from open pit to underground mining represents a key strategic challenge in modern mine planning. This paper presents a multicriteria and multivariable methodology to plan such a transition, integrating technical, economic, environmental, and social considerations. The proposed framework focuses on risk reduction (de-risking) through the identification of alternative development paths, the use of stochastic simulation to model geological and technical uncertainty, and different mining strategies such as methods, production rates, sequence, etc. for ultimate underground implementation. The study summarizes the limitations of traditional planning methods—which usually treat the open pit and underground mine designs as independent processes—, also often it considers a single mining method and production rate for the underground option. Instead it is proposed an integrated approach that leverages synergies between both mining methods and scalable production rates. Also the proposed methodology incorporates the definition of critical variables (geotechnical, economic, and social, among others), the construction of multiple operational and technological transition paths, and the evaluation of each path under criteria of economic attractiveness and practical do-ability (capacity to be executed). Using simulation tools (SIMPLAN for operational performance and SIMVAL for economic evaluation), probabilistic distributions of the different path are obtained, enabling the quantification of the project’s Value at Risk (VaR). A subsequent multicriteria analysis weights the expected profitability against the feasibility of execution of each alternative, producing a decision matrix that provides a framework for evaluating the different project path. As a result, the proposed approach identifies OP→UG transition strategies that maximize business value by capturing remaining resources while minimizing financial and operational risks. Finally, strategic conclusions and recommendations for the industry are provided, emphasizing the importance of early transition planning even challenging the open pit sequencing of the latest push backs by introducing early underground operations. Future work includes strengthening the methodology—such as integrating real-time analysis and adaptive decision-making—and providing recommendations for its application in various mining operations. In summary, this paper delivers a technical and professional framework to guide mining companies on when and how to carry out a successful transition from open pit to underground mining, balancing resource recovery with financial, operational, and social security.

Feb 22, 2026

By F. M. Doyle, Jiang Tao, Xu Shi, Chen Jin, E. Peters

Tafel curve technique and leaching tests have been applied to study the kinetics of gold leaching with thiosulfate. Results show that cupric ions and ammonia play the part of catalysts in the leaching of gold with thiosulfate. The activation energy of gold dissolution is calculated as 27.99 KJ/mol in the absence of both cupric ions and ammonia. However, the energy is reduced to 15.54 KJ/mol in a solution of 0.01 mol/L Cu (NH3)2 4* and 0. 5moVL total ammonia. The reaction order of Cu (NH,) g is one in the range of 0.001~0.1mol/L. These results support the electrochemical-catalytic mechanism pro- posed by the authors and explains the behavior of cupric ion and ammonia (Jiang Tao, et al., 1993)

Jan 1, 1993

By L. Yuan

To reduce fire hazards from spontaneous combustion of coal in longwall gob areas, a series of computational fluid dynamics (CFD) simulations were conducted by National Institute for Occupational Safety and Health (NIOSH) to model the spontaneous heating of coal in longwall gob areas. The previous modeling results demonstrate that spontaneous heating of coal usually occurred behind the longwall shields and along the face with a bleeder ventilation system. Assuming a stationary longwall face, the spontaneous heating could turn to a spontaneous fire in several days for the most reactive coal under favorable conditions. When the longwall face advances, the spontaneous heating process will be significantly affected. In this study, the effect of longwall face advance on the spontaneous heating in the gob area is investigated using the CFD model developed in previous studies. One longwall panel with a bleeder ventilation system is simulated. The width of the panel is 300 m, while the length of the panel is changed between 1,000 to 2,000 m. The same permeability and porosity profiles are used for gobs with different lengths. The spontaneous heating first develops in the gob when the longwall face is stationary. Then, the face advances at a certain rate. The face advance is simulated as a series of discrete movements, and the effect of the face advance on the maximum temperature developed during the face stoppage is examined. Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

Jan 1, 2009

By Jerry C. Tien

Without a doubt, the scope of China?s coal boom has been nonstop. Despite the world economic slowdown, China?s year-on-year gross domestic product (GDP) jumped 10.3 percent year-on-year in 2010, boosted by a faster than expected 9.8 percent expansion in the fourth [ ] quarter. And, the first quarter of 2011 expanded another 9.7 percent. According to a frequently cited statistic, the country is building two mid-sized coal plants each week. This amounts to a yearly increase equivalent to the entire power grid in the United Kingdom. China?s coal production was doubled in the last 10 years, from 1.044 Gt (1.15 billion st) in 1999 to 3.2 Gt (3.52 billion st) in 2010. This is 3.2 times the U.S. production (986 Mt or 1.085 billion st) and nearly half (46.3 percent) of the world?s total coal production (6.91 Gt or 7.6 billion st). This rapid increase of demand for coal has made China the world?s largest coal importer in 2009. With the economic situation improving, this trend is expected to continue.

Jan 1, 2011

By Gh. Crutu

During exploration and exploitation of complex ores, waste dumps that contaminate severely the environment and in particular soils and waters, are genetated. The most hazardous pollutants are heavy metals and metalloids (e.g As, Mo, Pb and Cu) as well as radionuclides (e.g U and Ra).

Jan 1, 2008

By James J. Olson

Most of the projects summarized in this paper are funded under the Bureau's Advancing Metal-Nonmetal Mining Technology program and are part of the in situ mining subprogram coordinated at the Twin Cities Mining Research Center. The borehole mining equipment development, are funded under the Bureau's Advancing Coal Mining Technology program, is essential to accelerated progress in the in situ mining subprogram, and some background information on this concept is included. The initial in situ research projects started in 1971-72 evaluated some of the critical blast design parameters for in situ copper leaching. The present program totals about $1 million per year and includes in-house research projects, cooperative (cost-sharing) projects with the mining industry, and research and development contracts. Two different extraction schemes are under investigation: inplace leaching and borehole (or slurry) mining. The principal commodity targets for the Bureau's improved in situ mining technologies include copper, uranium, coal, and potash. The principal purpose of this paper is to inform the mining industry of the in situ mining research recently completed or being conducted by the Bureau of Mines. In addition the Bureau encourages companies to comment on the program accomplishments as well as offer suggestions on top priority research needs for improving the in situ mining methods described in this paper.

Jan 1, 1977

By Hendrick A. D. Kirsten, A. Clayr Alexander

Stillwater Mining Company is currently developing a second underground palladium and platinum mine approximately 21 km (13 miles) west of their existing Nye operation in the Bear tooth Mountains of southern Montana. Portals for the two access tunnels required at the new site were excavated in limestone talus to accommodate4.6 m (15 feet) diameter tunnel boring machines. A review of the technical design, field conditions and construction of the portals is presented.

Jan 1, 2001

By E. D. Attanasi, M. W. Bultman

Most statistical measures of mineral exploration continued downward in 1986. Prospects in 1987, however, appear to have brightened for exploration as the overall economic health of the mineral industry improved. The Society of Economic Geologists (SEG) survey of US and Canadian firms documents the marked decline in US mineral exploration since the early 1980's. From 1981 through 1986, the total exploration expenditure by US firms declined by more than 73% (Fig. 1). Exploration expenditures by US firms declined by 66%%. US based professional exploration staffs were slashed by 70% (Fig. 2). Also, many firms have written off some reserves because of weak markets or have not delineated new reserves to replace production. The Canadian government reported that between 1981 and 1986 Canadian molybdenum re¬serves had declined by 30%, lead and zinc reserves by 20%, and nickel and copper reserves by 15%. The SEG survey also shows the immediate impact of the decline in the dollar on US exploration expenditures abroad. Between 1981 and 1986 the share of the exploration dollar spent by US firms outside of the country declined by nearly one-half and exploration acreage abroad declined by 69%. The downward trend of the last six years may finally be near the end as a leaner and more efficient minerals industry starts to gear up for a period of increased activity. An industry survey reported to Mine Development Bimonthly (Metals Economics Group) indicates that mining firms were expected to increase exploration expenditures in 1987 by at least 10% above 1986 levels. Worldwide expenditures for 1987 by companies covered by the report were expected to top $800 million. It is the first time since 1984 that an increase in exploration expenditures was expected. Also, the US Bureau of Land Management reported a 30% increase in new mining claims for fiscal year 1987 over fiscal year 1986. The bulk of the increase in claims was in states having intense gold exploration, particularly Washington and Oregon. Much of the optimism is undoubtedly due to the increases in metal prices that occurred in 1987. Some of these increases include gold, average price up about 20%; copper, average price up 24%; aluminum, average price up 26%; and nickel, average spot price up 20%. The SEG survey shows precious and base metals accounting for 89% of the exploration expenditures in the US in 1986, up 52% from 1981. The US Bureau of Mines estimates that 80% of US exploration activity in 1986 was directed entirely at gold (1986 Minerals Yearbook). Worldwide exploration plans indicate the continued dominance of gold exploration. New programs were announced for Ghana, Malaysia, and Indonesia. Major new exploration programs were also launched for lead-zinc sulfides in Morocco, platinum and palladium in northwest Brazil, rare earth minerals in Greenland, diamonds in Indonesia, and heavy minerals off-shore Australia. Significant gold discoveries were made at Angels Camp in Oregon; South Africa, near Potchestroom; India, in the Chitradgra district; Northern Ireland near Mt. Speerin; Chile, San Cris-

Jan 5, 1988

By A. Bascetin

Waste materials caused by mining activities are an important environmental problem. Paste technology is a good alternative for waste management because it has many benefits in the aspects of environment, cost and safety. Disposal of process wastes in paste form is an attractive option for waste management, as it eliminates or reduces the risks associated with conventional methods. Due to the geotechnical characteristics of the paste, it is very similar to soil materials. So determining the geotechnical properties of the paste material is essential to durability of the paste. The some important geotechnical properties are compressive strength, porosity, shear strength, hydraulic conductivity, water content, consolidation, etc. In this study, the important parameters and the relation between them were investigated and obtained some results which will affect for optimum design of waste management.

Jan 1, 2012

By Andre Vien, SANDRO DAVID DI, Frank Laroche

In 1994, Claude Bazin presented a novel method for linking size data from milling models to the feed input of flotation models. It was achieved with the simple addition of a metal/mineral distribution–size distribution relationship. This allows grade and recovery predictions from a varying mine plan through product size distribution predictions. 

By M. J. Hrebar

In the summer of 1990, a study was conducted to document large tractor (i.e., Caterpillar Dl1N) utilization in surface coal mining. The tractors were found to be utilized as primary production machines and in combination systems with blast casting and draglines and blast casting and excavator/truck systems. In addition, dozers were used to prebench ahead of a primary dragline system. The study also established ranges and averages for Dl1N operating costs and mechanical availability. Based on simulated production of various tractor dozing applications, the potential for low cost coal stripping was suggested (Hrebar, 1991). A follow-up study, also funded by Caterpillar Inc., was conducted in the summer of 1991 to determine actual production rates in two dozer stripping applications. These actual production rates would then serve as a foundation for estimates of stripping costs. This paper presents the results of the studies in a contour and a cast application.

Jan 1, 1992

By Mahiyar Nasarwanji, Jonathan K. Hrica, Jonisha P. Pollard, Lydia M. Kocher, Brianna M. Eiter

Within the metal/nonmetal mining sector, fall-related incidents account for a large proportion of fatal and nonfatal injuries that occur in mining in the United States. However, the events and contributing factors leading up to these incidents have not been fully investigated. To help provide a clearer picture of these factors, an analysis of imminent danger orders issued by the U.S. Mine Safety and Health Administration (MSHA) from 2010 through 2017 at both surface and underground metal/nonmetal mine sites revealed that most orders are associated with fall risks. Of these cases, 84 percent involved the workers not using fall protection, fall protection not being provided or the improper use of fall protection. Fall risks for workers most frequently occurred when standing on mobile equipment, performing maintenance and repairs on plant equipment or working near highwalls. In most cases, a single, basic, corrective action — such as using fall protection — would have allowed workers to perform the task safely. Overall, these findings suggest that a systematic approach is needed to identify, eliminate and prevent imminent danger situations. Furthermore, to protect mineworkers from falls from height, frequently performed tasks requiring fall protection should be redesigned to eliminate the reliance on personal fall protection.

By I. Iwasaki

Precious metals are commonly believed to be recovered along with sulfide minerals in flotation, but a few neutron activation analyses showed that the recoveries of gold and silver were unexpectedly low. Recoveries of platinum group metals remained unresolved due to interferences in the analyses. Electron micro-probe, scanning electron microscope and scanning auger microprobe analyses have identified nickel arsenide minerals in the ore and confirmed a close association of platinum group metals with the arsenide minerals as minute inclusions. These results indicated a need for re-evaluation of flotation procedures which have so far ignored special problems related to arsenide minerals. The electrochemical and flotation behaviors of nickel arsenide and their implications to the flotation recovery of arsenide minerals from copper-nickel bearing Duluth gabbro are presented.

Jan 1, 1985

By G. Caron, M. Boisclair

In 2005, CANMET-MMSL used its pool of expertise in ground control, open pit and underground mine engineering, mineral processing, information technology and applied mineralogy to launch a mine-to-mill research project. The objective of the project was to optimize the distribution of rock breakage energy among blasting, crushing and grinding activities, thereby maximizing the efficiency of energy utilization within comminution processes. Tests were designed to demonstrate that this approach could reduce the energy consumption, thus contributing to the reduction of Green House Gas (GHG) production in the Canadian mining industry. The project was accomplished in collaboration with DynoConsult and Dyno Nobel Canada Inc., a world leader in commercial explosives. Data analysis from 12 blasts (six with electronic and six with pyrotechnic detonators) in three different geological formations of a quarry (soft, medium and hard rock) shows that electronic blasting technology increases rock fragmentation by 15% (in hard rock) to 20% (in soft rock). A more uniform rock fragment size distribution is also obtained. The impact of the improved quality blast product on downstream processes of the quarry is a productivity increase of 5% in rock excavation and transportation, an energy reduction of 10% at the primary crusher and an increase of 15% of the primary crusher throughput. A soft-sensor prototype, based on primary crusher data (i.e. energy consumption, throughput, feed and product size distribution) and a simplified computerized process model, was developed for on-line measurement of the rock operating work index. Additionally, 385 rock samples and specimens were collected and prepared to determine the tensile and compressive strength of the rock material, to evaluate the aggregate crushing work index, and to examine the development of micro- and macro-fractures by means of binocular and SEM microscopy. Blast-induced rock damage was evaluated at the end of the laboratory testing program. Even though a reduction of rock hardness of around 30% was observed after blasting, the impact of the blasting method (i.e. use of electronic or pyrotechnic detonators) on the induced rock damage could not be observed. It is either absent or not perceptible with the accuracy of the measuring techniques and the number of samples analyzed.

Jan 1, 2007

By T. Hayashi

A sophisticated process of extracting ultrafine sulfide mineral particles of under 1µm size suspended in clay slurry has been developed through studies of electrochemical properties of particle surface. Experimental procedure and data of the process applied to some clay ores containing sphalerite and pyrite, and molybdenite and other sulfide minerals are reported. Discussions concentrated on the function of process reagents, particularly on various modifying reagents, and on the effect of dispersed or flocculated state of ultrafine particles in slurry which affect significantly the performance of the process.

Jan 1, 1982

Computerized financial models can be used in all phases of the mineral industry from setting exploration targets to projecting profit plans for producing mines. In this presentation, I will use the example of an exploration company entering a new district to trace the application of financial models through the following intermediate phases. 1. Hypothetical analysis and strategy 2. First encounter of mineralization 3. Preliminary drill results - decision process 4. Feasibility studies 5. Post-feasibility negotiations 6. Producing mine 7. Acquisition of producing mines or mineral properties. I will conclude with a brief discussion of the mechanics of the financial models that we use at Wright Engineers Limited. As we progress through the seven phases, the availability and accuracy of the data will parallel the complexity and application of the financial models. However, the same basic financial models are utilized throughout the seven phases. I will begin by suggesting that the exploration group is somewhat autonomous and has the mandate to explore in Western Canada.

Jan 1, 1979

By Michael Gauna

A high seam geologic condition exists at Jim Walter Resources No.4 mine which requires immediate rib support after a continuous miner cuts a place, High seam mining heights are typically 2.4 to 2.6 m (8 to 9 it) and a thick rock layer is present in the upper portion of the coal rib side. The 610 m (2000 ft) mining depth at No. 4 mine induces horizontal rib line movement after excavating an entry. Horizontal rib movement greater than 30.5 cm (12 in) have been noted. When lateral movement occurs in the high seam areas, the thick rock layer, and the coal above the rock layer, become fractured and tend to roll into the entry. If not adequately supported, large rib rolls develop in the place being bolted as well as in previously mined areas which endanger men and equipment. To control this situation rib support must be installed in the roof bolting operation as the bolting crew works towards the face. A rib control system has been developed for this high seam mining condition utilizing a mechanical anchor bolt placed at an angle in the rib and installed with a modified Fletcher DDFI- 15 bolting machine. Over 120 km (75 mi) of entry have been supported with angle rib bolts. These angle bolts constitute 43 to 60% of the total roof and rib bolt footage in the high seam port- ions of No.4 mine. The angle rib bolting system has proven safer, more effective, and more efficient than the earlier support method employing bolts installed horizontally into the rib. No rib roll accidents have occurred since the angle drill bolting machines were placed in service in 1981. By securing the broken rib material with an angle bolt anchored above the coal pillar, a more effective means of rib control is achieved. Angle rib bolting does not interfere with continuous miner productivity. In addition, bolting crews are now reduced from three to two people and the total drilling supply costs are approximately 60% the previous cost, when compared to the previous support method using horizontal rib bolts.

Jan 1, 1983

By John Carr

The tremendous growth in grinding mill size and horsepower during the '70s demanded advancements in gear cutting technology and equipment for the '80s. Computers are used as an aid in the design and selection of the mill drive system; sophisticated computer graphics are used to create manufacturing drawings; and a new generation of gear cutting machines are used to manufacture the gears. These new gear cutters can generate-cut gears over 40' (12.2 m) in diameter at an AGMA quality level exceeding the currenty acceptable standards. The precision of the resulting gear assures maximum tooth contact, which will result in longer gear set life.

Jan 1, 1981

By P. C. Fletcher, E. Kaya

The Bond grindability testing procedure has been standardized to measure the same grindability values, i.e. Bond work index (BWi), for the same ore when tests are performed in different laboratories or by different operators. This is accomplished by the standardization of mill dimensions, tumbling speed, grinding ball charge weight and distribution, sample ore charge weight in the mill and operating practice. The results of this investigation reveal that the Bond work index grindability values may differ substantially with different standard Bond ball mills. This paper will review the results.

Jan 1, 2002

By J. Harrison Daniel

Were the legislators and politicians responsible for the closing of the U.S. Department of the Interior?s Bureau of Mines (Bureau) in March 1996 fully aware of what they were doing? Throughout the United States? history, the domestic mining and minerals industry has been largely responsible for the nation?s growth and prosperity that had made it a world leader. The mining and minerals industry made it possible for the young nation to catch up with Europe during the Industrial Revolution, played an essential role leading to victories in World Wars I and II and was a core ingredient for continued economic growth. For a number of decades, America?s import dependency on non-fuel mineral materials has continued to increase. (USGS Mineral Commodity Summaries). Developing domestic resources to meet current and future demands ? particularly those resources considered to be of strategic and critical value to national security ? is necessary. Federal involvement is required since many of these resources are located on public lands. Another reason for federal involvement is that the success of the industry depends on long-range research programs and advances that may take up to 25 years to become commercially available. This situation requires federal partnership to coordinate the programs necessary to collectively involve the industry, individual mining companies and colleges and universities. So, how was it possible to close a federal agency that had contributed so much to the nation?s welfare in a mandated 90-day period, with more than 1,200 employees losing their jobs?

Jan 4, 2010