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By Roussos Dimitrakopoulos, Liam Findlay

Semimobile in-pit crushing and conveying (IPCC) systems can help reduce truck haulage in openpit mines by bringing the crusher closer to the excavation areas. Optimizing a production schedule with semimobile IPCC requires integrating extraction sequence, destination policy, crusher relocation, conveyor layout and truck fleet investment decisions. A mining complex with multiple mines and IPCC systems should be optimized simultaneously to find an optimal schedule for the entire value chain. An integrated stochastic optimization framework is proposed to produce long-term production schedules for mining complexes using multiple semimobile IPCC systems. The optimization model has flexibility to select the crusher locations and conveyor routes from anywhere inside the pits. The framework uses simulated orebody realizations to consider multielement grade uncertainty and manage associated risk. A hybrid metaheuristic solution approach based on simulated annealing and evolutionary algorithms is implemented. The method is demonstrated using an iron ore mining complex

Nov 1, 2024

By C. G. Snavely

Martin County Coal Corporation produces coal from seven continuous miner sections in two coal seams which are often interlaced with rock partings. Because of high clay content and coal oxidation, all minus 100 mesh material is discarded in the preparation process. We began experimenting with various drum lacings on continuous miners in 1983 to improve product size consist and increase machine cutting rates. To date, + 6.35 mm material has increased from 61 to 73% of mined product, minus 0.15 mm material has decreased from 6% to 4% of product, and machine cutting rates have increased by 50 percent.

Jan 1, 1985

By Lewis L. Oriard

The authors outline the development and application of blasting methods put into use 11 years ago at the Berkeley Open-Pit Mine, Butte, Montana. The blast design uses a very short delay (5 milliseconds) between detonation of explosives charges, a feature challenged several times in principle despite its success for Anaconda. Concern is expressed over the categorical rejection of very short delay blasting which can make the difference between success and failure of major mining operations. There is ample evidence to show that the method can be used successfully and not violate the concerns of the public.

Jan 1, 1980

By Morgan M. Sears

The LaModel program is widely used to calculate stresses and displacements on thin tabular deposits, particularly when multiple seams or complex mining geometry is encountered. The program itself allows the user to create multiple mining steps to show a progressive sequence of mining. However, LaModel considers each individual step as an independent steady-state condition, and any previous loading conditions of the materials are not tracked. It also does not consider any sort of dynamic stress change during the mining process. In certain circumstances, especially in multiple-seam situations, modeling a scenario of the seam of interest without considering the previous mining sequence in the off seams can potentially lead to inaccurate results. The primary objective of this paper is to present a situation where a potentially dynamic, unstable mining condition was encountered. It was not evident until the previous loading conditions in the off seams and the impact of dynamic stress changes in the active seam were considered. It is important to make the mining community aware of these potential modeling scenarios where the path-dependent nature of the mining sequence is of key importance. This paper presents a case history where room-and-pillar retreat mining was being conducted in a relatively deep cover stress regime where multiple seam interactions were present from both undermining and overmining. Mining in the active seam was being conducted with roomand- pillar mining techniques consisting of a series of parallel production panels being successively developed and retreat mined along a set of Mains. In this situation, the traditional global LaModel analysis without any path-dependent adjustments did not fully identify the area of poor conditions that were encountered. This paper explores the impacts of mining in the active seam on the lower seam which, in turn, has a negative impact on the active seam. This provided a solid foundation for the subsequent analysis of the three seams simultaneously. Based on the calibrated model, it is likely that retreat mining in the active seam resulted in increased stresses in the underlying seam that conceivably resulted in additional convergence and, most likely, additionally convergence of the pillars under the panel being developed. This in turn could have caused active subsid- The LaModel program is extremely useful for analyzing multiple-seam mining scenarios. As multiple-seam situations become even more prevalent, the potential for encountering a path-dependent mining scenario also increases. To successfully model path-dependent mining scenarios, the ground control engineer will be required to make sound judgments on the condition of pillars in sub-adjacent seams. These engineering judgments should be based not only on the current state of stress, but also on any prior or future states of stress. This means considering the stresses from over or undermining as well as stresses applied to the sub-adjacent seams from actively mining the seam of interest.

Jun 25, 2024

By G. T. Adel

The application of automatic control to mineral processing operations has been gaining momentum during recent years. Many strategies are being developed for controlling crushing, grinding and flotation circuits, however, their implementation in industrial plants is being slowed down because of the costs and difficulties in evaluating these strategies in a systematic manner. An interactive computer simulation package, developed at the University of California, provides the capability of analyzing the process dynamics of mineral processing circuits. This paper presents an overview of the simulator and its application to the case studies of grinding and flotation.

Jan 1, 1983

By Charles C. L. Smith

A review and comparison is made of the circuitry utilized for dc crane control systems. Anti-parallel three phase full wave thyristor bridges for dc motor reversing and speed control are compared with a single three phase full wave thyristor bridge for speed control and either contactor or static switching for reversing control to obtain complete four quadrant operation for crane material handling. In recent years the Harnischfeger Corporation has developed a solid state adjustable voltage control system to control the speed and direction of dc motors for crane applications and handling materia1.1 Shunt wound dc motors are utilized and speed is controlled in the motor base speed operating region at constant torque by a thyristor, silicon controlled rectifier (SCR), adjust- able armature voltage supply. The three phase thyristor bridge is the power controlling element of the dc adjustable voltage control. ELECTROTORQUE is the Harnischfeger Corporation registered trade name for this type of drive system. By controlling the gating signals or firing pulses to the thyristor bridge SCR's the dc output voltage can be varied over a wide range. This range is limited only by the magnitude of the ac applied voltage. To obtain operation of the motor in both directions two thristor bridges are connected in an anti-parallel arrangement. A typical schematic for two anti-parallel connected three phase SCR bridges is shown in Figure 1.

Jan 1, 1973

By V. K. Karra

An improvement in the present day screen sizing methods calls for knowledge on i) how material in the size range: 0.5 x 1.5 times the through-fall opening of the mesh on a deck, splits between the oversize and undersize streams of the deck, and ii) how near-mesh content of the feed affects the screening performance. In the throughput based sizing method given here, this is accomplished through the introduction of a generalized partition curve and a near-mesh factor. A newly developed efficiency factor is employed in addition to the traditional screen sizing factors.

Jan 1, 1979

By L. Frost

The establishment of a retreat system of longwall mining in this submarine coal field has been under study for many years and, although in special cases there have been limited local applications of this method of mining, there has been no attempt until quite recently to establish a uniform system of longwall retreating' in this area (see Figure 1) Where retreat walls were established, it was strictly as a result of physical, rather than economic conditions. In some of the operations- of the Corporation, where the coal was liable to spontaneous combustion- or the area subject to bumps as in No. 2 Mine of the Cumberland Railway and Coal Company in Springhills the recovery of the coal on a retreat system was more or less a necessity.

Jan 1, 1964

By Peter Zhang, Daniel Su, Bo Hyun Kim

Shale gas wells drilled in longwall chain pillars are influenced by longwall mining. Longwall mining on each side of the chain pillars can create overburden movements and induce deformations in gas well casings. If the deformations result in a casing breach, intrusive shale gas could leak into the longwall mine with serious safety consequences. This study concerns five shale gas wells in the chain pillars between two adjacent longwall panels in the Pittsburgh coal seam under a cover depth of 670 ft and a mining height of 7 ft. The gas wells were constructed with typical casing design, but a casing cementing alternative with uncemented production casings was practiced. Four production casings were uncemented, and one production casing was unintentionally cemented with good quality cement to a 535-ft depth and low-quality cement stringers from a 444- to 535-ft depth. The longwall faces passed by the shale gas wells as each adjacent longwall panel retreated. Production casings were surveyed by a multi-finger caliper after each panel was mined. No deformation was detected in the four uncemented production casings, but small deformations were detected in the partially cemented production casing. The maximum measured deformation in the cemented production casing was 0.05 in. after first panel mining and 0.06 in. after second panel mining. The casing deformations were also predicted by the FLAC3D model set up on site-specific overburden geology. The predicted deformations were in good agreement with the measurements in terms of deformation locations and magnitudes. All five shale gas wells resumed normal production after being temporarily plugged during the period of mine-by. This study provides a successful demonstration of the effectiveness of a casing cementing alternative for decoupling production and intermediate casing, and thus minimizing the influence of longwall mining in the shale gas wells drilled through longwall chain pillars.

Jul 1, 2023

By Peter Joralemon

I want to limit my remarks to epigenetic ore deposits, but do not necessarily subscribe to the classic theories of hydrothermal ore deposition. I will consider an epigenetic deposit as a primary deposit in which the economic minerals have been introduced subsequent to the formation of the enclosing rock, regardless of the source. Past ore discoveries have been made to a great extent by prospecting techniques that have remained relatively constant over the last many decades. In many cases the discoveries have been enlarged or enhanced with the use of technical tools such as geophysics, but theoretical geology, which should serve as a foundation for exploration, has shown little progress of practical importance since the turn of the century.

Jan 1, 1967

By Vasiliki Founta, Andrew J. Whittle

"This paper describes the development of a 3D finite element model for predicting ground movements caused by construction of 7.1 m diameter twin bored tunnels for the Crossrail project in London using Earth Pressure Balance (EPB) machines. The model uses the commercial FE code, Plaxis 3D, to represent the face pressure, conical shield, grouting process and activation of precast segmental concrete lining systems through a set of boundary conditions that advance through the soil mass along a prescribed trajectory. Soil behavior is described using the Mohr-Coulomb soil model with input parameters calibrated from laboratory element tests. The analyses focus on the performance of the EPB tunneling machines in greenfield conditions beneath Hyde Park, where the tunneling occurs within deep layers of relatively uniform London Clay. The model predictions are in good agreement with surface and sub-surface vertical settlements measured at a well-instrumented section, but tend to overestimate the measured lateral displacements towards the tunnel. Ongoing studies are focused on the role of soil behavior and the approximations in FE model predictions of tunnel-induced ground deformations. Introduction Since their introduction in the 1970’s, closed-face Earth Pressure Balance (EPB) machines have become widely used for soft ground tunnel construction. The EPB design relies on a screw conveyor system to regulate the pressure of the excavated soil/spoil within the head chamber and hence control stability at the face of the machine. One of the key design issues in the application of EPB machines is to establish how control parameters, including the advance rate, face pressure and grouting processes (used to compensate for the tail void at the rear of the shield and to infill gaps between the precast lining rings and surrounding soil) affect and/or control the far-field ground movements. For closed-face systems, short-term deformations are associated with ground losses at the face, overcutting and ploughing of the shield and poor control of grouting in the tail void; while long-term deformations can occur due to consolidation and creep within the surrounding soil (and are closely connected to the seepage boundary conditions;e.g., Laver & Soga, 2012). The control parameters for advancing the EPB machine can have a significant effect on the magnitude and distribution of the far-field deformations. Therefore, analyses of the ground response to tunneling require accurate modeling of the soil stratigraphy and constitutive behavior as well as the construction process. Finite element (FE) methods have been used to simulate tunnel construction since the early 1980s, but only a few studies involved three-dimensional modelling of mechanized tunneling (e.g., Finno and Clough 1985; Bernat and Cambou 1999; Swoboda and Abu-Krisha 1999; Dias et.al. 2000; Melis et.al. 2002; Kasper and Meschke 2004; Möller 2006). In order to get a better understanding of the effect of the construction process and soil properties on the development of the ground deformations more comprehensive models of tunnel excavation and tunnel support are required in order to capture the 3D nature of mechanized tunneling and the effect of construction parameters such as advance rate, face and grout pressure."

Jan 1, 2016

By Ehsan Alavi, Glen Frank, Michael DiPonio, Mike Mooney, Lisa Mori

"A study was conducted on the N125 project in Seattle to investigate the use of apparent density as an assessment tool for the effectiveness of soil conditioning. The formation of an air bubble as well as the plugging of cutterhead and excavation chamber can be a result of improper soil conditioning. Both air bubble formation at the top of the excavation chamber and developing plugging issues can be identified by analyzing the apparent densities in the excavation chamber. In this study, apparent densities less than unity were observed in the upper portion of both northbound and southbound TBMs, suggesting the presence of an air bubble. Apparent densities greater than the in-situ soil density were observed in the lower portion of the excavation chamber. Particularly high values of apparent density were coincident with clogging observed at multiple locations along the alignment. The combination of less than unity upper chamber apparent density and very high apparent density in the lower portion of the chamber are related, and indicate the inability of the TBM to effectively condition and mix the soil in the chamber.INTRODUCTIONProper soil conditioning in EPB tunneling offers many advantages to the quality and productivity of the project. There are few operational parameters that can be used to assess the soil conditioning performance such as advance rate, torque, thrust, chamber pressure signature, etc. One of the other parameters that potentially can be used is the apparent density. The apparent density of the material in the chamber was introduced by Guglielmetti et al. (2003) as the vertical chamber pressure gradient calculated from the physical relation between the horizontally measured chamber pressures and the vertical distance between the pressure sensors. Guglielmetti et al. (2003) introduced apparent density as a measure to ensure the excavation chamber is filled with material. To guarantee face stability the authors suggest to keep the apparent density over a certain limit so the material is able to transfer effective stress to the virgin soil, and thus provide support of the excavation face. They implemented this method at the Metro project in Porto, Portugal.Comparing the vertical gradient of the horizontal chamber pressures to the densities of excavation chamber samples, Bezuijen et al. (2005) discovered that the gradient is not necessarily representative of the muck density. They assumed that the yield stress of the muck as well as the adhesion between the muck and the cutterhead and bulkhead material have an influence on the vertical gradient during mining (Bezuijen et al. 2005, Bezuijen & Talmon 2014)."

Jan 1, 2016

By J. Kallioinen

The paper describes industrial size experiments with a 100 m3 flotation cell validating the Size Specific Flotation concept and the Tank Cell design. It discusses some variables affecting the flotation of coarse particles. The results were good. The flotation recovery of coarse particles increased up to 50%. In finer sizes the flotation improvement was 5-15% The enhanced flotation of especially the coarsest particles increased the total recovery close to 10%-units compared to conventional cells in a porphyry copper flotation. The related power draw was only 50-80% of the power of conventional cells.

Jan 1, 1995

By P. C. Thakur

Horizontal drilling in coal mines is a relatively new technology. The earliest recorded drilling in the United States was done in 1952 at the Humphrey Mine of Consolidation Coal Company for degasification of coal seams. Spindler and Poundstone experimented with vertical and horizontal holes for eight years. They concluded in 1960 that horizontal drilling in advance of underground mining appeared to offer the most promising prospect (for degasification) but effective and extensive application would be dependent upon the ability to drill long holes, possibly 300-to 600 m, with reasonably precise directional control and within practical cost limits.(1) Mining Research Division of Continental Oil Company, the parent company of Consolidation Coal Company, began a research program in the early 1970's to achieve the above objective. The technology needed to drill nearly 300 m in advance of working faces was developed by 1975 and experiments on advance degasification with such deep holes began in 1976. Preliminary Its of this research have already been published.(2) To date nearly 4500 m of horizontal holes have been drilled for advance degasification and earlier results were reconfirmed. In summary, these are: 1) The greatest impact of these boreholes was felt in the face area where methane concentrations were reduced to nearly 0.3 percent in course of two to three months from original values of nearly 0.95 percent.

Jan 1, 1979

By W. J. Martin

At the termination of mining, the quality of ground water in the ore-zone aquifer must be returned to a condition predetermined by the permitting agency. To immobilize the redox-sensitive elements (e.g., uranium, arsenic, selenium, molybdenum), it has been suggested that a reducing agent be circulated through the leached ore zone. We have conducted laboratory experiments to test the ability of sodium sulfide as such a reducing agent. Sodium sulfide lowered the redox potential of the effluent such that insoluble minerals containing the redox-sensitive elements should be stable. The uranium concentration of the solution decreased by more than three orders of magnitude. In column experiments, by the time ten pore volumes of the sulfide solution had flowed through, sulfide minerals were forming. The experimental results indicate that the addition of sodium sulfide should cause the chemical reduction of the leached sediments, thereby producing long-term stability of the ground-water/sediment system.

Jan 1, 1986

By C. E. Brechtel

Bench cut-and-fill stopes with heights between 85 and 105 ft are being excavated in the lower levels of the B-NEATH Zone. Estimates of pillar strength and pillar loading indicated a high probability of pillar failure. Some changes in mining practice were made to minimize impacts of pillar failure and a rock mechanics instrumentation program was employed to monitor stability during mining of the first stopes. Limited pillar failure, in the form of destressing, was observed in the initial stopes; however, global stability during mining was good. Instrumentation data indicated that predictions of pillar strength and stress were quite close to field results.

Jan 1, 1989

By M. A. Bouchat

The Kipushi deposit, where the Prince Leopold Mine has been installed, belongs to Union Miniere du Haut-Katanga and is located in the Belgian Congo, 20 miles SW of Elisabethville, at the vicinity of the Northern Rodhesian Border. The deposit is of the hydrothermal metasomatic vein-type; mineralisation took place, through the limestone of the, lower Kundelungu. This is a special fea¬ture of the deposit, compared to the other copper deposits of the neighbourhood, both in the. Belgian Congo and in Rhodesia. Actually, the primary mineralisation of these other deposits; is directly related to the stratigraphic systems: schistous dolomitic in the Belgian Congo and Roan in Rhodesia. Both facies are older than the Kundelungu and separated from this formation by a tectonic cataclysm. The valuable elements occuring at Kipushi are principally copper; and zinc. The deposit also contains smaller quantities of lead, precious metals and other elements including germanium.

Jan 1, 1960

By L. W. Swent

Dr. Emrick, honored guests, distinguished speakers, ladies and gentlemen, I am Langan Swent, Vice President for Environmental Affairs and Occupational Safety and Health, of Homestake Mining Company. Today, I appear on behalf of the American Mining Congress, as chairman of its uranium mine health subcommittee. The American Mining Congress is a trade association of several hundred members, which include the producers of a large proportion of the nation's uranium. I've been asked to make a statement of principles for the uranium industry. There are two types of principles that apply to industry in general, and specifically to the uranium industry. Some have external origins and apply regardless of what industry does or thinks. Others are generated by industry itself and serve as goals for the industry. I'll discuss some of each type. I'll limit my statement to those principles related to the subject of this conference--radiation hazards in mining. I won't take your time trying to explain some of the unrelated principles that we must all contend with, such as Parkinson's Laws, Murphy's Law, and the Peter Principle. First and foremost, industry has a sincere interest in the well-being and health of its employees. There are two basic reasons for this. One is a basic respect for human lives, especially those of people we see and work with every day. No one in management wants to carry the lifelong burden of blame for a life lost due to poor working conditions. Most uranium and other mining is done in small communities. Production workers, maintenance workers, service workers, shift bosses, foremen, superintendents and managers all live in the same community. They attend the same churches. They serve together in civic activities. Their children go to the same schools. If one employee in such a community loses his life due to poor working conditions, those remaining know in a daily and intimate way the resulting personal tragedy, usually of a bereaved widow and fatherless children. This sad experience makes the community, including industry management, intensely sensitive to the need for maintaining good working conditions in the mines. But what about the segment of industry that does not live in the mining communities? Corporate and owner's offices are frequently hundreds of miles from the communities where the mining takes place. Many of these people are not personally acquainted with the workers, and there are few close personal ties between the two communities. The distant staff are, however, still human beings and motivated by the same basic human respect for life. Mr. Manuel Gomez of MSHA and a member of the planning committee for this conference summed this point up expressively when he told me: "No one group has a corner on compassion." In addition to compassion, there is another factor. In both communities the basic assignment to everyone is to produce profits. In carrying out this assignment, supervisory and management people are acutely aware of the high cost of illnesses and accidents. Their objective of maximizing profits is advanced significantly by minimizing illnesses and accidents at the mines. A business that has illnesses and accidents generally suffers from poor employee morale and high employee turnover, both of which detract from profits. Next, I would like to talk about what industry has done in the field that is the subject of this conference. We have worked at all sorts of methods to reduce exposure of employees since the exposure standards were first introduced and then lowered. Other speakers will go into details of technology, and I'll simply comment on exposure results. These are best shown in Table 1. The table shows the average WL to which miners in U.S. underground uranium mines have been exposed since 1937 through 1980. The trend of decreasing radon daughter concentrations throughout the period is obvious. Figure 1 presents this data graphically and shows the trend at a glance. This record begins in 1937 when uranium, as such, really wasn't being mined or sought. The concentrations given by the U.S. Public Health Service were for a few small vanadium mines which carried uranium as a by-product. A few years later, when the Manhattan project to develop the atomic bomb was begun, these mines became the first U.S. uranium mines and the vanadium became the by-product! The radiation hazard then also received attention and the average concentrations began to decline. As knowledge of the reality of the hazard spread, conditions improved. The search for uranium in the U.S. turned up new and larger ore bodies that had to be mined by large underground mines. These mines involved ventilation planning from the beginning, and when they came into production in the late 1950's they lowered the average concentrations greatly. Then in 1960 the American Standards Association adopted a standard setting 1 working level as a satisfactory condition, and several action levels up to 10WL, at which point removal of people from exposure was called for. As a result of the uranium producing states governors' conference in December 1960, state mine inspection agencies, in the early 1960's, began to adopt and enforce the ASA standards. As a result, average concentrations again declined. In 1967, the Federal Radiation Council recommended an annual limitation of 12 WLM per individual. This represented a great change in the methods of

Jan 1, 1981

By Rory P. A. Ball, Mark Briggs, Martin Dix

"Tunnel professionals should inform project stakeholders on the reality that tunnel projects are not 100 percent devoid of the need for excavations or public inconveniences during both design and construction phases. Competing stakeholder objectives to limit these disruptions must be weighed against the need to mitigate risks and to produce a constructible, operable and maintainable end product. Perhaps the approach we should take with stakeholders, also known as Authorities Having Jurisdiction (AHJs), is sharing memorable case studies that bring to life the potential risks so often buried within lengthy risk registers. This paper provides a sobering case study describing what can occur if the presence and/or location of utilities and other obstructions are not fully understood due to restrictions placed on exploration or mining operations. In this instance, the Microtunnel Tunnel Boring Machine (MTBM) encountered a buried concrete structure, followed by rows of abandoned wood piles, before finally colliding with an active high-pressure gas main under a bustling coastal highway. Multiple stakeholders imposed tight logistical and other work restrictions, compounding the difficulties experienced during the drive. However, the difficulties were effectively managed through the project team’s proactive collaboration and communication with everyone involved. INTRODUCTION Some of the most important decisions that influence the ultimate success or failure of a project may not be made by design engineers. Instead, these decisions are often made by project stakeholders and third-party agencies. Tasked with protecting the best interests of their users, these agencies are cautious of potential impacts associated with project construction and subsequent use. Unfortunately, actions required (or restricted) by stakeholders often result in unwanted ripple effects that negatively affect the very users they are trying to protect. For example, a mandate limiting a shaft site to an unreasonable size may be intended to reduce local business impacts, but may actually increase impacts as more supply and truck hauling is required."

Jan 1, 2016

By J. D. Cooper

Previous research developed guide- lines to restrict the placement of air velocity sensors to areas of Low turbulence in underground nines. Even though these guidelines are theoretically correct, and may be easy to follow in underground coal mines, their application in small underground metal mines is difficult. As a result, study was undertaken at the Colorado School of Mines Experimental Mine to determine if an air velocity sensor could be placed in other locations with acceptable results. It was found chat by applying a variable calibration function to correct for changes in amounts of turbulence, instead of the previously used calibration factor multiplication, the sensor could be used successfully in areas of moderate turbulence.

Jan 1, 1984