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By A. M. McKim

6, 7.3 meter diameter autogenous mills at Wabush Mines are undergoing conversion from a radial configuration of pulp discharger to a curved design. Improved discharging efficiency has effectively lowered the pulp level in the mill. The low level operation enhances the grinding efficiency netting a 12% power reduction. Significant reductions to rate of wear has been a spin off benefit. The design incorporates features for holding the assembly solidly in place thus eliminating bolt hole damage and leakers. Preliminary work in one 11 meter mill at Hibbing Taconite did not indicate that all the same advantages were available in their process.

Jan 1, 1982

By Luis R. Bittencourt

Research efforts have been made to characterize a refractory Brazilian bauxite ore composed basically of gibbsite, kaolinite and quartz. Detailed polished-section microprobe analysis of the unbroken ore has been used to describe the liberation characteristics and the association between mineral phases. The linear grade distributions for selected particle size fractions were determined by means? of a particular implementation of King's Random Fracture Model that uses the exponential model for the distribution of linear intercepts through both dispersed (kaolinite) and continuous (gibbsite) phases. The corresponding volumetric grade distributions were then determined by means of a constrained optimization technique for the solution of the transformation equation. Batch flotation experiments were carried out to determine the kinetics for particles of different sizes and the results correlated with the liberation spectrum for each size class.

Jan 1, 1991

By Billy W. Parks

This paper reports on the first 2 years in operation of a special-purpose coal handling rig which provides blending, temperature reduction, and continuous, automatic mechanical sampling as part of midstream barge to ship coal transfers. Briefly reviewing some of the characteristics of coal handling peculiar to midstream transfers, the paper discusses how the most beneficial aspects of midstreaming were enhanced through the design of this blending and sampling rig.

Jan 1, 1986

By Andrew Thomson, Peter Wright

"A section of a London Underground expanded segmental lined tunnel constructed in the 1970’s progressively deteriorated after 2001, with extensive radial joint spalling and mid-segment cracking. As part of the PPP contract Tube Lines Ltd and their partners carried out various analyses of the tunnel, including analysis of laser scans of the tunnel, geotechnical testing through the tunnel walls, geotechnical desk studies, real-time monitoring and even full-scale segment testing. This paper discusses the behaviour of the tunnel lining in this setting, the causes of failure and the lessons that can be learnt from this rare example of a tunnel which was progressively failing in service. It is finally noted that a replacement tunnel lining was installed during night-time possessions and completed in 2015. INTRODUCTION In 2003, Tube Lines Ltd. was established under a Public-Private Partnership (PPP) scheme to provide maintenance services and upgrade projects for London Underground (LU). The Deep Tube Tunnel Knowledge and Inspection Programme comprised the assessment of all tunnels, shafts and other underground structures. This included a number of lengths of tunnel constructed using segmental concrete linings. First used by LU in the 1960s, the savings both in cost and speed of construction led to concrete linings replacing cast iron for new tunnel construction in all but a few cases. During the initial scoping phase of this programme, inspections identified potential issues with the expanded concrete segmental linings on the Jubilee line. The inspections found a number of segments with surface spalling (Figure 1a), which did not appear on the post-construction defect records. These were generally relatively shallow, up to 40mm deep, spread over a wide area of segment. These were different to spalls caused by handling damage, which are typically localised at segment corners. Subsequent inspections over the following years identified an increasing number of segments with these types of spalls as well as an increased incidence of longitudinal mid-segment cracking (Figure 1b). The increasing occurrence of these defects was hypothesised to be caused by tensile stresses developing in the vicinity of the joint."

Jan 1, 2016

By R. S. Hearon

The image of the open-pit miner in the eyes or the Environmentalist has never been very outstanding. The phosphate industry, whose history in Florida reaches back to the late 1800's, can-not be credited until recently with a large number or accomplishments in terms of protection or the environment to change this image. This lack of action was not deliberate or in opposition with the desires of the public. In the formative years, there was little or no public and the companies found it necessary to build towns to house their employees and their families, towns which remained in existence until the late 50's and early 60's or formed the core of present large communities. Neither these pioneers nor most subsequent resource developers considered themselves un-thinking spoilers, nor were they so regarded by their contemporaries. Instead, they acted in a manner consistent with their environmental circumstances and intellectual heritage. Early Americans did make mistakes in using the land but the mistakes became apparent only in the opinion of later generations. Over the past five to ten years, there has been a new self-awareness in the industry with regard to environmental responsibilities brought about, in part by a continuing onslaught of new regulations with jurisdiction over our activities. Part of the new regulations are aimed at industries as a whole while many, particularly state regulations, pertain specifically to the phosphate mining industry. Why all the new regulations? The reasons are encased in a complex web of activity but stem primarily from a new public awareness of its environment. More and more of our youth have become interested in the environmental science areas such as biology and ecology. The tremendous growth rate in both the population and industry has made personal issues out of subjects such as atmospheric inversions and water shortages which previously were abstract concepts. The State has grown from a population of 1,500,000 in 1930 to approximately 9,000,000 people today. This personal impact and general lack of knowledge on the part of the public concerning economics has resulted in big business no longer being held in awe, often in contempt and generally in suspicion where environmental concerns are encountered.

Jan 1, 1978

By E. A. Rychkun

Mining and environmental objectives have traditionally been in conflict. This conflict reflects a delicate balance between the need to spend money to protect the environment, and the need to save money by extracting minerals efficiently. In an increasing number of cases, profit margins diminish rapidly with new environmental regulations and reactionary measures. Forced cleanups and increasing restrictions are unwelcome expensive processes. A practical solution lies in planning rather than reacting. This requires the ability to precisely quantify and qualify environmentally sensitive problems by providing effective engineering tools to model, visualize and analyze subsurface conditions. Prevention of environmental conflicts, and effective cost control are both rooted in the mining company's ability to construct accurate models, monitor changes, assess contamination risks and to design effective remediation plan. This paper presents a case study where these issues are addresses through the application of a new and innovative technology.

Jan 1, 1993

By T. H. Ueng

Solving ventilation networks of natural air splitting is a classical problem in mine ventilation. A common approach to this problem is to formulate it based on Kirchhoff's voltage and current laws and obtain the solution by an iterative technique known as the Hardy Cross method. In this paper, it is shown that the problem can be formulated and analyzed as an unconstrained optimization (minimization) problem. The computational experience with the method of conjugate gradients is also discussed.

Jan 1, 1984

By A. A. Campoli

A stress control design strategy was developed to minimize the explosive failure of highly stressed pillars, during room-and-pillar retreat mining conducted between stiff immediate roof-and-floor strata. A confined core coal pillar strength model was based on in-mine geotechnical evaluations of successful room-and-pillar and longwall bump control designs. Tributary area and linear shear angle approaches were used to estimate development and gob side abutment pillar loads for supercritical section widths. Subcritical width sections separated by barrier pillars to control stress within total extraction panels were optimized with the boundary element program MULSIM/NL.

Jan 1, 1994

By Donna Wallace

Past EPA groundwater monitoring programs required that contamination not leave the boundaries of a disposal facility. New regulations under the Resource Conservation and Recovery Act (RCRA) require that once hazardous waste constituents are detected beyond the limits of the disposal area, a program to define the rate and extent of contaminant migration must be instituted. Future regulations are likely to include even more stringent groundwater protection criteria. The implications of both the existing and probable future groundwater protection and monitoring requirements in terms of using geologic containment as a means of disposing of hazardous waste are explored in this paper.

Jan 1, 1981

By David M. Koogler

If you are contemplating starting a small coal mining operation there is a good possi¬bility that you can not afford it. If you, have already started, you may be on the road to bankruptcy. If you are a small but well established operator you may be trading dollars, or even dissipating your capital, equipment and other assets. A bleak outlook? Yes! Meant to be discouraging? No! Just a reminder that, with todays costs of doing business, high interest rates, rapidly increasing costs and decreasing sales prices, a small businessman/miner had best watch closely or he will be mired in something worse than a soft bottom - namely a cash and credit shortage, and in too many instances In recent times, bankruptcy. We will not dwell on what happens once you are that far gone, though I could cite a good example. But, let us look at what should be done to avoid such a catastrophe.

Jan 1, 1981

By Y. C. Guan

The leaching kinetics of chalcopyrite in ammonium iodide solutions with iodine has been studied using rotating disc. The variables studied J include the concentrations of lixiviants, rotation speed, pH of the solution, reaction temperature, and reaction product layer. The leaching rate was found to be independent with the disc rotating speed. The apparent activation energy was measured to be about 50 kJ/mole from 15°C to 35°C, and 30.3 kJ/mole from 35°C to 60°C. Experimental findings were described by a kinetic model, and the overall rate was found to be: (formula)

Jan 1, 1997

Gold cyanide equilibrium adsorption isotherms in the loading range typical of operating carbon-in-pulp/carbon-in-leach plants have been established and the effect of various cations and the presence of copper cyanide species quantified. It was found that the equilibrium loading of gold was enhanced by the presence of sodium or calcium, with calcium having an order of magnitude stronger effect. The presence of copper has an adverse effect on the equilibrium loading of gold. A unified model was developed to predict the effect of sodium and calcium concentrations in solution and the competitive carbon adsorption of copper on the equilibrium loading of gold on carbon. A satisfactory agreement between the measured gold equilibrium loadings and the model results was obtained over a wide range of solution conditions.

Jan 1, 2010

By H. Dho

The role of sodium silicate in the anionic flotation of a Florida phosphate ore was investigated using laboratory continuous flotation tests, frothability tests and SEM observations. In the absence of sodium silicate, Ca++ promoted the unwanted activation of quartz by forming calcium bearing precipitates. The addition of sodium silicate enhanced the flotation efficiency through: (1) the removal of impurity minerals and calcium-bearing. precipitates from quartz surfaces by dispersion, (2) drier and more persistent froths stabilized by oily droplets containing calcium silicate precipitates, and (3) higher specific flotation rates of phosphate relative to quartz, leading to faster flotation rates and increased selectivity of separation.

Jan 1, 1990

By Devan Naik, Matthew Stokes, Andy Nigro

This paper describes the surgical removal of a 24 ft dia. Slurry Shield TBM entombed beneath one of the country’s busiest commuter rail interlockings, the Harold Interlocking in Queens, NY, and the construction of the interface to a cut/cover tunnel which extended the mined tunnel section. A sophisticated SOE was built around the TBM to support active track loads within 8ft. of the excavation. Once the TBM head and guts were removed, a full round CIP lining was installed connecting the existing precast tunnel liner to the C/C tunnel under construction. All this construction was done on a narrow island of land without road access nestled between 7 mainline LIRR/Amtrak rail lines.

Jun 13, 2021

By A. B. Cecala

An evaluation was recently performed on a district recirculation system at a trona mine in Granger, Wyoming. A 1.52m (5 ft) diameter, 37.3kw (50 hp) vane axial fan was installed in a crosscut between the intake and return airways and recirculated approximately 31.4 m'/sec (66,578 ft'/min) of air back into the intake. This amounted to a recirculation factor of approximately 20 pct of the return air. This air was part of the primary ventilation to three different continuous miner sections at operating distances of between 6l0m (2,000 ft) and 1,829m (6,000 ft) from the recirculation fan. The mine environment was constantly monitored for respirable dust, methane, and carbon monoxide in the operating sections and in the main intake and return entries. In addition, air samples were taken with and without the recirculation system during the evaluation and analyzed using gas chromatography. The results of this study showed only small increases in dust, while all other mine contaminants remained at such low levels that it was impossible to determine any relative changes from the recirculation system. Because of this, a brief SF. tracer gas analysis study was subsequently performed to more precisely determine an increase in a mine contaminant with the recirculation system.

Jan 1, 1991

By Z. Yu

Dewatering of a -0.5 mm fine coal has been studied extensively. Deep cleaning requires however fine grinding, and dewatering of such ultrafine products presents a great challenge. Several coal samples finely ground and characterized by different wettabilities have b.een used in the filtration tests. Vacuum and press filters have been employed. In this paper only the results obtained with different flocculants (totally hydrophobic. semi-hydrophobic and hydrophilic polymers) are included. The results reveal the effect of coal surface properties and flocculant type on filtration of ultrafine coal.

Jan 1, 1994

Ferric (Fe3+) ions are omnipresent in flotation circuits. Depending on pH and the nature of the ore body, Fe3+ ions may play a role in the adsorption of thiol collectors on sulfide minerals. To investigate this possibility, a two-compartment galvanic coupling cell was designed. This cell was used to monitor changes in contact angle of a sulfide mineral in one compartment, while varying concentrations of the Fe3+ ions in the other. The results showed that Fe3+ ions promote xanthate adsorption as indicated by the increase in contact angle. Implications of this finding in sulfide mineral flotation in general will be discussed.

Jan 1, 1998

By André Vervoort

After the systematic closure of Europe’s coalfields in the late twentieth century, the emphasis is now clearly on industry’s environmental legacy. One aspect of the latter is the longterm surface movement above abandoned coal mines. The analysis of satellite data shows that the subsidence lasts longer than generally assumed. However, a few years after the flooding of the abandoned underground coal mines, a new phenomenon was observed, i.e., the direction of the surface movement was reversed. The phase of upsidence has already lasted for several decades, and only future measurements will tell how long it continues. A key conclusion is that the regions with maximum subsidence do not necessarily correspond to the greatest upsidence. In other words, buildings and infrastructure are subjected to a different loading from this upsidence than during the subsidence phase. The longterm surface movements have an impact on vulnerable structures in the densely populated regions of the former deep coal mining areas in Europe. These movements create additional damage. This new knowledge is also relevant for mines that are still in operation or future mines that are planned.

Feb 1, 2024

By E. McCullough, S. Gaillard

"Diesel particulate matter (DPM) remains a health concern in many underground metal/nonmetal mines, and has been regulated by the Mine Safety and Health Administration since 2002. While the NIOSH 5040 standard method for DPM monitoring is required to demonstrate regulatory compliance, the FLIR Airtec DPM Monitor can serve as complementary engineering tool. It is a handheld instrument that offers near real-time measurements. As part of an ongoing field study, the Airtec has been used to survey elemental carbon concentrations (a proxy for DPM) in an underground stone mine. Via “spot-checking” and more prolonged area monitoring, this effort was aimed at determining spatial and temporal DPM variation in several key locations. INTRODUCTION Diesel particulate matter (DPM) is the solid fraction of the exhaust emissions from a diesel engine. It is largely made up of elemental and organic carbon (EC and OC, respectively), which can be measured as proxies for estimating mass concentrations of DPM. The National Institute for Occupational Safety and Health (NIOSH) considers DPM to be a health hazard and potential carcinogen [1]. It is believed to cause and/or exacerbate respiratory illness upon inhalation, deposition, and retention in lung tissue [2]. Since DPM exists in both the micro- and nano-particulate ranges, it can surpass typical auto-immuno defense mechanisms that keep larger particles out of the respiratory system [2]. Relative to other occupations, the DPM exposure potential for underground miners is high because these individuals work in enclosed environments where diesel powered equipment is frequently used [3,4]. A variety of engineering and administrative controls have been devised to reduce DPM exposures in underground mines, and increased airflow is often a key component of control strategies. In large-opening mines, which are most common in the metal/nonmetal sector, DPM abatement via increased ventilation can be especially complex due to moving and controlling the large air quantities [5]. The Mine Safety and Health Administration (MSHA) has regulated DPM exposure in metal/nonmetal mines since 2002. The final rule limits personal exposure to total carbon (TC, which is the sum of EC and OC) to an eight-hour time weighted average (TWA) of 160 µg/m3. To demonstrate compliance, operators must use the NIOSH 5040 Method [6]. However, the Airtec DPM Monitor (FLIR Systems, Inc., Nashua, NH) was developed as an engineering tool to provide near real-time measurements of both EC and TC for tracking personal exposures [7]. The portable Airtec works by capturing DPM on a filter and successively measuring laser extinction on the filter as DPM accumulates; the EC fraction of the DPM is dark, and so as it accumulates the filter becomes darker and absorbs more laser light [8]. The laser extinction value is directly correlated to EC, but since EC and TC are generally observed in consistent proportions (i.e., TC = EC*1.3), the Airtec is also programmed to display TC as a TWA [9]. There have been multiple studies conducted to validate the Airtec and the instrument has been adopted by some mine operators as a tool for their health and safety programs [3,8]."

Jan 1, 2016

By Alessandro Navarra, Aldo Quelopana

For decades, open-pit mine planning algorithms have incorporated geological uncertainty and other elements or characteristics for increasingly realistic representations. Among these complexities is the detailing of downstream processes that occur inside processing plants. Previous studies have demonstrated that the strategic mine plan and mineral concentrator design are coupled, and should therefore be optimized simultaneously within the same quantitative framework. However, existing frameworks offer limited representation of operational modes. This work demonstrates an approach to resolving this gap, in an optimization based on a parallelized Variable Neighborhood Descent (VND). The resulting algorithm embeds mass-balancing linear programming (LP) using a DantzigWolfe decomposition. A case study of a Zn-Pb deposit is presented to show the performance reached.

Jun 25, 2023