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By F. G. Heivilin

We are no longer short of viable Rare Earth deposits. As little as 2 years ago China mined and produced 97% ofthe world?s rare earths. Only a few deposits were in an advanced stage of exploration and development. Now Technical Metals Research (TMR) Gareth Hatch *5 reports that 347 deposits are being developed by 265 companies down from 440 on July 6th. Their Index of Advanced projects lists 45 projects in 14 countries. They will sustain the world for centuries to come and many good deposits are yet to be found. The problem is mining 14 elements in balance. Each of the deposits listing production in the chart has a unique set of minerals which they think will give them a cost advantage. Which of these will make it to production is a question. Most of the Advanced won?t be mined soon, but which ones? China is still in the driver?s seat in Light Rare Earth production (LREO) with one deposit with 35 million ton Baiyunebo deposit in Inner Mongolia which is part of a working iron ore deposit. The number of HREE deposits have been reduced and they attempting to eliminate unpermitted mines. This report will tell you what a Rare Earth is, how rare they are, why they are important, and where they are being developed which includes Australia, the United States, Africa, Greenland, Brazil and Canada.

Feb 27, 2013

By John Reilly

Costs of complex/underground projects have been consistently underestimated and delivery on time and on budget has been problematic. This has been attributed, to inadequate cost estimates and unidentified and/or insufficiently managed risk. Use of probabilistic cost estimates like the Washington State Department of Transportation?s CEVP® process (developed by the author and others) has produced more realistic cost estimates, explicitly identified and quantified risk (as input to risk management plans) and early awareness of key project issues. This paper updates previous work (NAT 2004), adds implementation detail for probalistic cost estimating as used by WSDOT, FHWA and other agencies and will address key issues in risk management, as related to probalistic cost estimates.

Jan 1, 2008

By W. G. Pariseau

"BACKGROUND The Crandall Canyon Mine (CCM) is located in the Wasatch coal field in central Utah. Extensive longwall mining at CCM preceded a decision to recover coal left in barrier pillars on each side of a set of main entries extending far into the mine. During mining in March, 2007, a major bump occurred that led to cessation of mining in the barrier pillar on the north side of the mains and to begin mining in the south barrier pillar. Subsequent loss of ground control in August, 2007, through coal pillar bursts had tragic consequences with loss of six miners and shortly afterwards three rescue team members. An MSHA report describes the events in detail (MSHA, 2008). An important lesson to be learned from CCM is the need to select a computer program suitable for pillar design. Computer programs are engineering tools; selecting the right tool for the job is essential. In this regard, a minimum program requirement is capability for computing stress distribution within a pillar and adjacent roof and floor strata. The reason is simple: strength of rock is stress dependent; both vary from point to point in pillars and adjacent strata. Preferably, one should follow the evolution of stress as the mining plan is executed from start to finish to assure safety or to warn of a potentially hazardous situation developing as mining progresses. The approach to the problem posed by barrier pillar mining at CCM is conventional in the sense of applying well known finite element modeling techniques to analysis of a proposed mining plan. The engineering purpose is to evaluate the mining plan with respect to ground control questions including roof, floor and pillar safety. Results of previous two dimensional finite element analysis indicated pillar safety was by no means assured (1, 2, 3). Geometry of barrier pillar mining is limited in two-dimensions, for example, crosscuts are not seen in vertical cross sections. While three dimensional analyses are preferred, even moderately sized regions often lead to very large problem sizes that exceed computer capabilities. However, a recent development in finite element modeling of tabular deposits allows for whole mine analysis in three-dimensions. This technique involves a dual node – dual mesh concept. Both have been used separately in much earlier work, but are only now are used in combination. Estimation of subsidence at a kilometer scale and details of stress, strain and displacement about barrier pillars, main entries and pillars, and so on at a meter scale are possible (4). No compromise involving empirical formulas or similar guess work is required. Indeed, all calculations are based on first principles: physical laws, kinematics, and material laws. Effects of joints and in situ variability or uncertainty in strata properties, elastic moduli and strengths, may be included for greater realism. An important objective of the present study is to assess the role of three-dimensional pillar geometry in arriving at conclusions regarding barrier pillar mining versus two-dimensional results."

Jan 1, 2015

By Jan Van Greunen, Mark Vanderzee, David Haug, Geoffrey Hughes, Yiming Sun, Roozbeh Geraili Mikola

"The Sanitation Districts of Los Angeles County is planning to construct a new, approximately 7-mile-long (11.3 km) effluent outfall tunnel to be excavated by TBM and lined with precast concrete segments. Anticipated net operating pressures within the tunnel are expected to approach 3 bar. To counteract joint opening and exfiltration leakage, an approach has been investigated to post-tension the precast concrete tunnel lining with steel tendons. The tunnel alignment crosses several seismically active fault zones, at which installation of steel pipe is proposed as a secondary inner lining to mitigate potential offset displacements. This paper discusses the tunnel lining design approach and methods used to address these unique challenges.INTRODUCTION The Sanitation Districts of Los Angeles County (Sanitation Districts) is planning to construct a new 18-foot-diameter (5.5 m), approximately 7-mile-long (11.3 km) tunnel from the Joint Water Pollution Control Plant (JWPCP), located in the City of Carson, to the existing White Point outfall manifold structure at Royal Palms State Beach (RPSB) (Figure 1). The project is part of the Sanitation Districts’ Clearwater Program, which will improve overall system reliability through the repair and replacement of the existing aging infrastructure. The existing system includes two 6-mile-long (9.7 km) tunnels, 8- and 12-feet in diameter (2.4 and 3.7 m), and four ocean outfall pipes with a maximum capacity of approximately 675 million gal/day (MGD) (2.6 billion L/day). Addition of the new parallel tunnel will increase overall capacity to accommodate peak wet weather wastewater flows of up to 1,262 MGD (4.8 billion L/day) and will allow inspection and repair of the existing tunnels. The new outfall tunnel will be excavated using a pressurized face tunnel boring machine (TBM). Shafts at the north (JWPCP Shaft) and south (RPSB Shaft) ends of the proposed alignment will connect the tunnel to the existing wastewater treatment plant and existing ocean outfalls manifold and during construction act as launch and receiving shafts for the TBM. The tunnel will be excavated from north to south as a single heading."

Jan 1, 2016

By C. L. Lin

A PC image-based, on-line instrument for the measurement of coarse particle size on a conveyor belt is under development. Both the hardware and software required to implement such a system are discussed, including the interface for the special image acquisition hardware. The system concept is given with examples to illustrate the step-by-step procedure for the implementation of image-processing algorithms.

Jan 1, 1992

By G. M. Wilemon

The U.S. Bureau of Mines has conducted investigations on extracting phosphate values from wastes generated during the mining and beneficiation of phosphate matrix. These wastes may contain up to one third of the phosphate originally present in untreated ore. Samples of wastes were air-dried and leached using 93 pct sulfuric acid in the presence of methanol. Evidence for the formation of a calcium sulfate hemihydrate coating that hinders complete dissolution of phosphate is presented. Solid-liquid separations were enhanced when flocculation was effected using poly(ethylene oxide) (PEO) in conjunction with hydroxypropyl cellulose (HPC) or hydroxyethyl cellulose (HEC. A conceptual flowsheet for a proposed process using an acid-alcohol leaching technique is presented.

Jan 1, 1990

By H. L. Lovell

The growing production of fly ash with the many attendant problems of economics, disposal and potential uses suggests an urgent need to consider those properties which are basic in its beneficiation. Fly ash is extremely variable and heterogeneous in all respects except its fine size. Because of its production in huge quantities, it becomes significant as a potential raw material. Detailed data are presented describing particle size and shape, density distribution and magnetic characteristics. The major components include combustible residuals, magnetite and silicates. These data are discussed in terms of beneficiation processes and uses, The results of air classification to produce a uniformly fine-sized low combustible product are encouraging. It is proposed that major increases in the future use of fly ash, must involve some form of beneficiation. Both the coal producing industries and the consuming utilities would benefit from increased utilization.

Jan 1, 1964

By R. W. Smith

The electrokinetic and flotation behavior of the green alga Chlorella vulgaris was studied in the absence and presence of Pb(II), Al (III) and flotation collectors. It was found that the presence of Al (III) is necessary for good flotation of the organism whether or not Pb(II) is present when dodecylammonium chloride or sodium dodecylsulfate is used as collector. Best flotation using dodecylamine is at about pH 8 and best flotation when using sodium dodecylsulfate is at about pH 4. It appears because of the small size of the organisms that the Al (III) is necessary for flocculation to enhance bubble-cell contact and C. vulgaris removal from water. When N-dodecyl-2-aminoproprionic acid is used as collector good flotation occurs at about pH 4 without the addition of Al (III).

Jan 1, 1990

By Jr. Flynn

The filtration process has long been utilized in the mining industry and typically associated with processes where clear solutions are required. One definition of filtration states that it is utilized to affect a more complete separation of liquid and solid phases than is possible with settling alone. The development of Diatomaceous Earth filter aids has added a new dimension to filtration technology in the mining industry. It makes possible the filtration of slimes with almost perfect clarity, and at rates that become economical.

Jan 1, 1980

By Richard E. Barrett

The relationship between coal characteristics and power plant performance has become a matter of increasing interest to utilities. This relationship can affect the value of coals, decisions as to coal washing, setting penalties for delivery of coal that fails to meet specifications, and justifying buying better coals (at higher costs) before public utility commissions. The study described in this paper was directed to identifying how coal characteristics impact on boilers and related coal and gas handling systems. TVA data for the period 1962-1980 was the basis for the study. Models were developed for boiler efficiency, boiler availability, and maintenance costs as a function of such coal characteristics as ash, sulfur, and moisture content and boiler age. Boiler load and maintenance efforts were considered as variables in some of the models, but were found not to be statistically significant. Although the results of this study are strictly applicable to only the TVA system, they can serve as guides or first approximations for other utilities.

Jan 1, 1983

By Rushikesh Battulwar, Javad Sattarvand, Joseph Seamons, Masoud Zare

In the last decade, new developments took place in the area of indoor positioning (or localization). Since the Global Navigation Satellite System (GNSS) cannot be used in underground mines, other technologies are needed for localization. Positioning and communication options today primarily include Wi-Fi, Bluetooth Low Energy (BLE), Ultra-Wideband (UWB), Radio Frequency Identification Device (RFID), etc. Smartphones and tablets currently have an array of sensors and radios, which can provide valuable information to allow indoor localization via various methods. Where mineworkers could keep smartphones with them, they can be highly effective at enabling localization and navigation. Recent applications of these technologies in underground mines have been thoroughly reviewed and examined for the likelihood of their utility for accurate localization where no other means exist. Some critical challenges and gaps that need to be addressed in future research have been identified.

Sep 5, 2021

By William E. Lamont

As a part of the Department of the Interior's rutile and titaniferous materials development program conducted under the Defense Production Act, the Bureau of Mines investigated the potential for producing national stockpile grade rutile from plant products of phosphate beneficiation plants operating in the central Florida pebble phosphate district. The potential for producing ilmenite, zircon, and monazite concentrates from the plant products was also investigated. Results of these studies indicated that 3,000 to 6,000 tons of rutile, 28,000 to 55,000 tons of ilmenite, 9,000 to 19,000 tons of zircon, and 400 to 800 tons of monazite passed through the plant circuits annually. All of these minerals are presently being sent to waste ponds. Beneficiation of a bulk heavy mineral concentrate separated from the amine flotation tailing (froth product) of numerous plants in the district showed that it was possible to produce a rutile concentrate containing over 94 percent Ti02. Additional studies showed that over 70 percent of the Ti02 in the rutile concentrate could be isolated in a product containing 98.0 percent Ti02. The studies also showed that it was possible to produce ilmenite concentrates containing 63 percent Ti02, zircon concen¬trates containing 65 percent Zr02, monazite concentrates containing over 85 percent monazite [(Ce,La,Y,Th) (P04)], and xenotime concentrates containing over 35 percent xenotime (YPO4).

Jan 1, 1969

By Jiang Su, Michal Uhrin

"The use of composite linings, consisting of permanent sprayed primary and secondary linings with a sandwiched spray applied waterproofing membrane is expected to improve efficiency and reduce lining thickness, but it also brings complex primary-secondary lining interaction. This issue is further complicated by the uncertainty regarding the long-term behavior and parameters of the sprayed concrete–sprayed membrane interface.This paper aims to address this issue by presentation of a series of numerical analyses of a typical shallow SCL tunnel in soft ground with a range of design assumptions on the interface behavior: (1) compression only; (2) compression and tension; and (3) compression, tension, and shear.The results demonstrate that the assumed interface behavior has a significant impact on the primary-secondary lining interactions. A design approach of ignoring the tension and shear bond at the interface may not be conservative particularly for serviceability. This paper explains the rationale behind these conclusions and discusses the implications for design.INTRODUCTIONSprayed Concrete Tunnel Lining SystemsSprayed concrete linings (SCL) have been used in conventional tunneling for decades. However, details of SCL systems may differ to a large extent depending on ground conditions and specific tunneling methodologies.In hard rock conditions, for example, drill and blast excavation is typically supported by rock bolts and sprayed concrete (NGI 2014). Such tunnels are usually designed fully drained and the above-mentioned support elements considered permanent without the need for a further inner liner. Therefore, there is no structural interaction between separate lining shells to consider.In conventional tunneling in the European Alps, a double shell lining is typically utilized, consisting of an outer (primary) sprayed concrete lining and an inner (secondary) cast-in-place concrete lining, separated by a waterproofing system. The primary lining normally includes rock bolts and may include other support elements. The waterproofing system is usually based on a plastic membrane and a geotextile fleece. The tunnel may be designed fully or partially drained or fully undrained. Although there are two structural lining shells interacting, investigation of such interaction is generally irrelevant to designers because the primary lining is considered only temporary (fully sacrificial in the long term). An overview of reasons for this assumption is given, for example, by Lemke (2014). The secondary lining is designed to resist all foreseeable loads on the tunnel. The primary lining may, in reality, interact structurally with the secondary lining during the life span of the tunnel. However, since the secondary lining design must cover all possible (extreme) scenarios, investigation of such interaction does not bring any value to the design."

Jan 1, 2016

By M. E. Rossi

Reconciliation of long-term block model reserves and mine production frequently shows significant discrepancies. This reconciliation can be done comparing the long-term block model reserves against a grade control model (generally, a model based on blast holes or production data). in this paper called an FI factor for tonnages, grade, and ounces; and also it should be done comparing the grade control model to the mill feed (or loaded to heaps) tonnages, grades and ounces (called an F2 factor). The long-term model usually contains blocks with dimensions larger than the size of the selective mining unit (SMU) of the operation. The smoothing effect of an estimator such as kriging will generally result in a grade-tonnage curve that does not match the grade-tonnage curve of the SMU's to be recovered. This problem is partly to blame for the reconciliation discrepancies found. In addition, in-pit perfect selection is impossible. and therefore the grade-tonnage predictions based on blast holes also need to be assessed, considering both unplanned dilution and the errors of estimation of the grade control model. This paper will focus on using conditional simulations to assess the uncertainty of the predicted grade-tonnage curve in terms of minable reserves, and in the framework of long-term mine planning. Quantifying the uncertainty in no uncertain terms is done in conjunction with a popular pit optimizer, which will yield not one, but several possible minable reserves, and therefore a range of possible minable tonnages and grades per pit shell or scheduled phase. This is a step further from the usual sensitivity analyses that are performed for deposit evaluation or development planning. Specifically, this approach takes into account the volume-variance relationship, the selectivity of the mining operation, planned and unplanned dilution. and carries the local uncertainty implicit in grade estimation into the mine design and mine planning phases. The motivation for the approach is discussed through an example, as well as a description of the procedures and steps involved.

Jan 1, 1998

By James H. Barks

Commercial development of the mineral resources of southwestern Missouri began about 1850 and spread into southeastern Kansas and northeastern Oklahoma, forming the Tri-State Mining District with Joplin as the urban center (fig. 1). The value of the Tri-State mineral production from 1850 to 1950 exceeded one billion dollars, and until 1945 the region was the world's leading producer of lead and zinc concentrates, accounting for one-half of the zinc and one-tenth of the lead produced in the United States (Gibson, 1972 1). By 1950 most of the rich ores had been extracted, and mining and milling operations declined during the 1950's and ceased in the 1960's. The sulfide minerals, mainly galena and sphalorite, were mined from cherty limestones at depths of 25 to 75 m (meters). Crude ores were brought from the mines to the surface where they were milled into lead and zinc concentrates. , Barren rock was discarded in piles while the ore-bearing rock was crushed and ground into fine gravel. The minerals were separated from the rock by a jigging process and the tailings were skimmed off and discarded in large piles. Ground-water flooding of the mines was controlled by constant pumping. When pumpage declined in the 1950's and 1960's tile abandoned mine drifts and shafts filled with water. At present (1977) numerous tailings piles and flooded mines remain as visible evidence of the mining era and as a threat to the quality of ground and surface waters of the area. In 1976 the U.S. Geological Survey in cooperation with the Ozark Gateway Council of Governments made a study of the effects of the mines and tailings piles on water quality in the Missouri part of the Tri-State District. The study area covers approximately the southwestern quarter of Jasper County, an area of about 725 km2 (square kilometers), and is bounded by long 94 o 15' w.' and the Missouri-Kansas state line, and lat 37 o 15 N., and the Jasper-Newton County line.

Jan 1, 1977

By Daniel de la Rosa, Juan Manuel Mayoral, Damián Vital

"This paper presents a numerical study regarding the loads, and the corresponding damage, taken by the primary and secondary lining of a tunnel built in cemented fine-grained stiff soils. This study aims at establishing more rational design criteria that take into account explicity the lining performance. A 3.5 km long tunnel to be built in a densely populated northwest area of Mexico City, was considered as case study. Series of three-dimensional finite difference models, developed with FLAC3D, were used to simulate the tunnel construction, and to compute the ground settlements, internal forces, bending moments, and displacements acting both on the primary and secondary tunnel linings. Interaction diagrams were used to study the lining performance. Several advancement lengths, and tunnel covers were considered to establish their impact on the loads transferred to the tunnel lining. A practice-oriented damage criterion for tunnels was proposed based on the interaction diagram analysis. INTRODUCTION Lining performance during conventional tunnelling, CT, as defined by the International Tunnel Association, ITA (ITA 2009) is strongly affected by the construction procedure. Special attention must be taken in cemented fine-grained materials, such as those found in the northeast portion of Mexico City, due to the potential of fragile failure (i.e. the soil fails suddenly without important deformation) that these soils may exhibit. During CT, it is assumed that the ground strength contributes to the stability of the excavation, as long as the lining is built correctly. It is common practice to consider two structures, which together form the tunnel support: 1) A primary lining, which is a flexible support, which allows excavation walls to deform to mobilize part of its shear strength, and thus contributes to the tunnel self-stability, and 2) A secondary lining. Commonly, the primary lining consists of several layers of shotcrete. In this case the installation method guarantees perfect contact between the lining and the excavation perimeter. The secondary lining, if required, is used to withstand the load conditions in the long term and also has an esthetic function. This paper presents a numerical study aimed at establishing a performance damage criterion for the primary and secondary lining design in cemented fine-grained stiff soils. Due to the lack of data, the strength and deformation parameters were established through empirically-derived relationships. Three-dimensional finite difference models were developed to simulate the tunnel construction, and compute ground settlements, internal forces, bending moments and displacements acting both on the primary and secondary tunnel linings. Interaction diagrams, along with a damage criterion were used to study the lining performance. From the results gathered insight was gained regarding tunnel lining performance during CT."

Jan 1, 2016

The National Institute for Occupational Safety and Health (NIOSH) conducted a monitoring field study to optimize the rib control plan in a room-and-pillar coal mine. The study mine is located in the Central Appalachia coal basin. Two monitoring sites were selected at different sections in the study mine. The selected sites have different overburden depths and geologies. The instrumentation plans at study sites include borehole pressure cells installed at various depths in studied pillars, rib and roof extensometers and load cells mounted on number of the rib bolts. The instrumentation results and observed geology for one of the study sites showed great potential for optimizing the rib bolt plan at that section of the mine. Therefore, a rib support optimization study was followed using numerical modeling technique. A calibrated threedimensional model was developed using the instrumentation results of the optimization section. The calibrated model was used to determine the optimum rib support for expected overburden depths and rib heights. Baseline rib bolt patterns were assumed for the optimization study. Additional rib bolts, above and beyond the baseline bolting parameters, were outlined and identified as solutions to contain the rib fracturing identified by the modeling results.

Jul 28, 2020

By G. T. Homce

Most electric motor predictive maintenance methods have drawbacks that limit their effectiveness in the mining environment. The U.S. Bureau of Mines is developing an alternative approach to detect winding insulation breakdown in advance of complete motor failure. In order to evaluate the analysis algorithms necessary for this approach, the USBM has designed and installed a system to monitor 120 electric motors in a coal preparation plant. The computer-based experimental system continuously gathers, stores, and analyzes electrical parameters for each motor. The results are then correlated to data from conventional motor-maintenance methods and in-service failures to determine if the analysis algorithms can detect signs of insulation deterioration and impending failure. This paper describes system design and implementation. At this writing, however, installation is still underway, and field data analysis results are not yet available.

Jan 1, 1994

By Elimame Elaloui, Kais Elghniji, Constantin Virlan, Aurel Pui, Chaima Ouled Amor

Separation and identification of minerals composing the Tunisian silica sands have been conducted by acid etching and hot filtration/sedimentation (HFS) without affecting the quartz component. It was found that the hot acid etching process is an effective method to separate quartz and clay minerals in the silica sand. The SEM micrographs of the silica sand show rough surface and some cracks with irregular shapes. The surface becomes clean and smooth after acid etching process. After chemical dissolution, the clay minerals were recovered by hot filtration following by sedimentation at low temperature. FT-IR, EDS maps, and secondary electron (SE) analyses of separated clay minerals reveal the presence of Fe2O3, montmorillonite, and kaolinite minerals. The LIBS analysis of clay minerals shows the presence of Al, Fe, Ca, Al, and Mg. The sequential etching process can be introduced in the purification methods as an effective way to separate quartz from clay minerals.

Jul 29, 2020

By J. Dubbert, T. H. Jones

"This paper describes a rib-control methodology that uses standing support to provide most of the lateral resistance to the rib. The method is analyzed, and its boundary conditions for rib control are described. In this method, an animal-fencing mesh product covers 80 percent of the rib surface and is sparsely bolted to the rib. Can supports or other similar stiff supports are installed primarily as roof support for the entry. As the rib spalls and dilates, the mesh catches the material and expands, pressing against the standing support. Mining proceeds, and vertical roof loads increase the normal force on the Can supports, causing friction at the top and bottom of the support to go up, thereby improving lateral resistance to rib swelling.At one mine in the western United States, this method has proved excellent at preventing the buildup of rib spall. It substantially reduces the number of bolts used for screen installation, improves installation efficiency, reduces manual labor and provides more rib coverage than many screening methods. Because standing support is typically part of the roof-control plan in longwall tailgates, no additional standing-support costs are incurred. IntroductionRib safety in underground coal mines is an oft-studied topic because ribs are high-hazard areas. An overview of early rib safety research can be found in Jones and Mohammed (2014). There is a significant difference between rib support and rib control. Support improves safety through the installation of strengthening elements, such as bolts and dowels, designed to reduce rib spalling. Although spall reduction is preferred, controlling how the rib fails is enough to ensure safety in some situations. Rib control uses external elements to provide confinement, thereby holding sloughed material in place, or to prevent falling rib material from striking mine personnel. This paper presents a study of a control method used on the pillar side of a longwall coal mine tailgate in the western United States."

Jan 1, 2015