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By D. Scott Barr

The Zarafshan/Newmont Joint Venture operates the Muruntau heap leach project, located in the Kyzylkum desert of central Uzbekistan. The mine produces more than 12.4 t/a (400,000 oz/year) of gold from low-grade oxide ore stockpiles adjacent to the Muruntau open pit. It is op¬erated by the Navoi Mining and Metallurgical Combine and is one of the largest gold resources known (Fig. 1). Since commissioning in 1995, total heap leach production has exceeded 21 t (675,000 oz). The joint venture uses four-stage crushing and screening to produce a final product for heap leaching, Merrill-Crowe processing and local refining.

Jan 1, 1998

By J. N. Hartley

Uranium mill tailings, waste products of uranium extraction, contain hazardous constituents that if released into the atmosphere and groundwater could threaten our health and environment. To provide for safe disposal and control of these tailings, Congress enacted the Uranium Mill Tailings Radiation Control Act of 1978 (Public Law 95-604). Subsequently, the Environmental Protection Agency (EPA) established standards for tailings disposal that limit radon emission into the air to 20 pCi m-2s-1 on an annual average basis (EPA 1983). The design life of the impoundment is to be 1000 years where practicable, but 200 years at least. To facilitate the design of containment systems that will meet the EPA standards, the Nuclear Regulatory Commission (NRC) and the Department of Energy (DOE) are sponsoring research at the Pacific Northwest Laboratory (PNL)* to develop the necessary technology. Earthen and asphalt materials have been evaluated for use as radon barriers (Hartley 1983) and as liners to minimize leaching (Buelt 1983). Herbicide and rock barriers against biological intrusion have been evaluated (Cline 1982). Surface stabilization techniques have been investigated to maintain the long-term effectiveness of a containment system that must be protected from wind and water erosion, chemical and physical degradation, and biological disturbance.

Jan 1, 1984

By J. Rao Mokka

Extensive exploration has resulted in delineation of a massive sulfide district on the north flank of the east-central Alaska range. The district covers approximately 400 square miles and contains numerous stratiform; transported and some replacement type sulfide deposits ranging in size from less than 1 million tons to 20 million tons. Five types of ores were sampled for the study. Mineralogical analysis revealed that the minerals are too fine grained for conventional grinding and beneficiation. Hydrometallurgical studies were con-ducted using ferric chloride as a lixiviant. Ore microscopic studies as well as electron microprobe analyses of minerals in the raw samples and leach residues explained the low recoveries for certain elements as well as sources of impurities that need to be eliminated from the process streams.

Jan 1, 1991

By K. Kim

A site characterization strategy formulated for the probabilistic design of underground structures is presented, which takes into account the variability of rock properties and the stochastic nature of the rock failure process. It entails determining probability distributions of rock properties by utilizing the theory of extremes and Monte Carlo simulation. Laboratory and field test data are analyzed and presented to illustrate the methodology. The results indicate that the distributive characteristics of rock mass properties can be estimated using empirical relationships currently available. This results of analyses can be incorporated into the design of underground structures, and then, the relative uncertainties of the failure probability of the structures can be assessed.

Jan 1, 1995

By Andrew W. Jenike

The first significant studies of problems related to the handling and storage of bulk solids were reported at the end of the nineteenth century. Early work originated from the necessity to store large quantities of grain and was concerned mainly with pressures affecting the structural design of silos and bins. The Janssen formula (about 1898) and the work of Ketchum [1] form the highlights of that period. In more recent years, progress in mechanization, increasing plant capacities, and rising costs of labor have focused the attention of engineers on the problem of gravity flow of bulk solids. A great deal of work has been done with models, and flow patterns obtained in small scale bins have been described in several publications, for example [2, 3]. An attempt to develop a theory of flow of bulk solids was reported in 1954 [4, 5, 61 and presented to the in a paper [7] in the same year. AIME recommended the continuation of this work and, as a result, Engineering Foundation granted a sum of money to set up a Bulk Solids Flow Laboratory. Two and a half years ago the project gained the support of the University of Utah and a laboratory was set up on the campus of the University. This project is now in progress, it has received the support of the American Iron and Steel Institute and of Kaiser Engineers, Division of Henry J. Kaiser Company. The results obtained to date are summarized in this report.

Jan 1, 1959

"A fire design innovation of the concrete lining of the Ohio River Bridges East End Crossing Tunnel has been developed. As a result from a fire suppression and tunnel ventilation system, the project design Heat Release Rate (HRR) was able to be constrained from 300 MW to about 50 MW. With this reduced HRR, concrete lining without passive fire protection may be acceptable, if the tunnel concrete lining will not result in explosive spalling during the designed fire event. Concrete explosive spalling test was proposed to verify this assumption. Since no standard concrete fire explosive spalling testing procedure exists, a project specific testing procedure was developed and fire tests conducted. From fire test results, it is concluded that the proposed tunnel concrete lining, in conjunction with the proposed fire suppressing and ventilation system, will not experience explosive spalling and does not require a passive fire protection system. INTRODUCTION The Ohio River Bridge East End Crossing Tunnel is part of a Public Private Partnership project, which connects transportation network between Louisville, Kentucky and southern Indiana. Located in Louisville, Kentucky, the twin-tube highway tunnel provides northbound and southbound lanes of the Kentucky approach to a new bridge across the Ohio River. Tunnel lengths are approximately 1,675-ft and 1,685 for the northbound tube and the southbound tube, respectively. Connected by two cross-passages, both tubes have a roadway width of 40-ft, for 3-lane traffic, and a vertical clearance of 26.5-ft.The Tunnel was constructed by drill and blast method with shotcrete and rock dowels as initial ground supports. The final tunnel lining consists of 16 inches cast-in-place concrete lining and 20 inches invert slab, with a waterproofing system around the tunnel perimeter. Two (2) tunnel side drains and one (1) invert drain were provided for each tube. This paper describes the rational in assessing fire design requirements of the tunnel final concrete lining, to answer the question whether a passive fire protection system is needed or not."

Jan 1, 2016

By Jack S. Watson, Rasika Nimkar, Robert M. Counce, Matthew Gordy, Patrick Zhang

Waste phosphatic clay presents a difficult disposal problem and a significant loss of P2O5. Recent developments make this study on the use of phosphatic clay as a feed material for H3PO4 production worthwhile. (a) New data from Florida Industrial and Phosphate Research Institute (FIPR) suggest that the Bclay^ waste can be effectively treated by improved solid separation coupled with flotation to produce feed material for recovering additional phosphate. (b) The use of BOLI Flowsheet^ provides capability to predict performance of aqueous-based processes for a range of possible operating conditions. Using the new FIPR data and BOLI Flowsheet^ enabled the design of a new process that can potentially extend the usefulness of current P2O5 ore deposits. Predictions using OLI Flowsheet were able to identify process conditions that effectively overcome the difficulty of high Mg content of phosphatic clay. Estimated manufacturing cost in the current study lead to valuation of the P2O5 content of the phosphatic clay recovered/utilized at 60 to 70% of that of the phosphate rock feed material currently used. Phosphatic clay should be considered as a valuable material that is currently given zero value. The new FIPR data and BOLI Flowsheet^ enables the design of a new process that can potentially extend the usefulness of current phosphate ore deposits by extending the fraction P2O5 of recovered

By VIVEK KASHYAP, EVODY TSHIJIK KARUMB, PATRICK TAYLOR

Zinc ferrite is considered an integral phase of zinc residues as their presence can render the processing of zinc and critical metals difficult. It is a refractory phase, formed at high temperature in the presence of zinc (Zn) and iron (Fe) during oxidative roasting in zinc processing plants. Because it is refractory to efficient leaching, unreacted zinc ferrite gets concentrated in the final zinc residue, making it a viable source of zinc and indium extraction. The refractory nature of zinc ferrite makes the extraction of associated critical metals difficult. In order to explore a potential economic and carbon-neutral zinc ferrite processing technique, our previous study proposed the partial reduction of zinc ferrite followed by sulfuric acid leaching of the roasting product [1-3]. As demonstrated in our previous studies, partial reduction of zinc ferrite results in a mixture of ZnO, Fe3O4 and FeO, which can be further subjected to leaching for efficient extraction of zinc and critical metals such as gallium and indium.

Dec 1, 2022

By Arash Dahi Taleghani, Pooyan Asadollahi

Slurry walls, also known as diaphragm walls, are commonly used as temporary and/ or permanent support of excavation for construction of shafts in soft ground. Through case history, this paper demonstrates economical benefits of disregarding long-term structural contribution of the slurry walls particularly in severe environmental condition. In addition, for temporary slurry wall shaft systems, possibility of using steel fiber, synthetic fiber or additives in lieu of temperature/shrinkage reinforcement is discussed with detailed analysis. Finally, the paper will be concluded by introducing unreinforced slurry wall shaft system using newly developed/patented concrete additive.

Jun 13, 2021

By JUAN DIAZ, Kray Luxbacher, Steven Schafrik, Dionissios T. Hristopulos, Zach Agioutantis

Methane gas is emitted during both underground and surface coal mining. Underground coal mines need to monitor methane gas emissions to ensure adequate ventilation is provided to guarantee that methane concentrations remain low under different production and environmental conditions. Prediction of methane concentrations in underground mines can also contribute towards the successful management of methane gas emissions. The main objective of this research is to develop a forecasting methodology for methane gas emissions based on time series analysis. Methane time series data were retrieved from atmospheric monitoring systems (AMS) of three underground coal mines in the USA. The AMS data were stored and pre-processed using an Atmospheric Monitoring Analysis and Database Management system. Furthermore, different statistical dependence measures such as cross-correlation, autocorrelation, cross-covariance, and variograms were implemented to investigate the potential autocorrelations of methane gas as well as its association with auxiliary variables (barometric pressure and coal production). The autoregressive integrated moving average (ARIMA) time series model which is based on auto-correlations of the methane gas is investigated. It is established that ARIMA used in the one-step-ahead forecasting mode provides accurate estimates that match the direction (increase/decrease) of the methane gas emission data.

Aug 2, 2022

By Jorge Armstrong, Sean Warren, JOSEF BOURGEOIS

The application of statistical analysis software programs has proven useful for the investigation of rockfall runout distance along a designed slope. Rockfall modeling programs are continually being upgraded with more sophisticated analysis tools, such as the use of the rigid body versus lump mass models. Engineers at mine sites utilizing the software may have varied experience related to these models, their associated input parameters, and how to interpret the generated results. To address this concern, researchers at the Spokane Mining Research Division (SMRD) of the US National Institute for Occupational Safety and Health (NIOSH) investigated the influence of slope height, slope angle, slope material, and rock size for both rigid body and lump mass models in a 2-D statistical analysis program. Based on a literature search and industry input, specific ranges common to that of an open pit mining environment were chosen for each of the input parameters to determine 90% rock runout distance as well as their sensitivity to change. Data collected from this numerical analysis and simulation will be compared to empirical rockfall data gathered through the duration of the Highwall Safety project conducted by NIOSH from 2022–2026.

Jun 18, 2023

By D. R. Tesarik, T. C. Trancynger, W. G. Pariseau

The Davis detector cavern was excavated on the 4850 Level of the former Homestake Mine in the mid- 1960s to house a novel neutrino detector developed by Nobel Prize winner Dr. R. Davis. The original cavern was about 9.1 x 16.8 x 9.7 m high, excavated in a Precambrian amphibolite known as the Yates unit and enlarged in 2010. In 2009, the National Science Foundation selected the site for development as a national Deep Underground Science and Engineering Laboratory (DUSEL). This retrospective rock mechanics study of the Davis cavern is intended to inform design of the much larger caverns and laboratory rooms being considered for the same 4850 Level. Provision for rock mass variability, sequential excavation, jointing and wall damage from blasting are included in analyses that were done using two different computer codes and methods (FLAC3D and UTAH3). The results are in agreement with observations and show that cavern stability is indeed the case. The main conclusions are: (1) if conventional scaling of laboratory rock elastic moduli and strengths is done, then 0.25 and 0.50 scale factors are reasonable, (2) measured statistical and spatial variability in rock properties should be incorporated into geomechanical analyses to better reflect reality, (3) discontinuities (“joints”) are essential to reliable analysis of excavation safety and when properly taken into account eliminate the need for empirical “scaling” of laboratory rock properties, (4) major geologic features such as rhyolite dikes and breccia zones may be important to excavation safety at Homestake and should be explicitly represented in analyses and (5) quantifying wall blast damage is important to engineering design of underground excavations.

Jan 1, 2012

By John A. Riddle

Some of the pitfalls and problems in selecting and applying corrosion-resistant materials in uranium plants are discussed, together with some suggested solutions. Includes some cost data.

Jan 1, 1979

By ETHAN FUSTER, Richard Ray Jr, STEPHEN LEE

The abstract states that horizontally-mounted jet fans are commonly used to ventilate vehicular tunnels due to their space and cost savings compared to fully ducted systems. It highlights the successful use of vertically-mounted jet fans in exhaust ventilation shafts for a passenger rail overbuild in New York City. The paper compares shaft dimensions, jet fan placement, and measured airflows, also comparing these measurements to predictions from computational fluid dynamics (CFD) simulations.

Mar 16, 2022

By R. W. Lake

The decision to develop an ore body can lead to multi-million dollar profits, or equally substantial losses. Accordingly, the effort required to adapt a valuation model to the specific proposal at hand, or even the development of a new model from basic principles, is clearly warranted. In the formulation of a model of this nature, one is faced with some major questions. For example, with the long term obligations that it implies, on what basis should a decision to initiate mining operations be made? Furthermore, how can the vagaries of inflation and the uncertainties that shroud the future be accommodated? Beyond the general principles by which mineral deposits are evaluated, specific cost behaviour is a function of the geology of the deposit, and of the mine design. Moreover, mine design, during the life of the mine, must be a continuing process somewhat akin to dynamic programming. An initial, apparently optimal, design is selected and mining commences. With production, a continual process of information updating leads to revisions. Thus if the maximum value is to be obtained, the mine design must be adjusted to conform to the changed conditions.

Jan 1, 1977

By Eugie Kabwe

Rock bolts are components of tunnel support structures and their efficacy in reinforcement requires the appropriate estimation of the bolt pre-tension. However, cases of ineffective rock bolt application due to loosening are common which leads to the potential failure of the support structures, thus negatively affecting the tunnel stability. The effective employment of pre-tensioned bolt within support structures requires an appropriate installation tension as a result of sufficient bolt head/nut pre-load. Henceforth, this paper presents a load indicator washer (LIW) capable of withstanding assigned static loading as well as provides an appropriate pre-tension. The different LIW breadths are numerically analysed in the finite element code (ABAQUS) to estimate deformation when a designated 60-kN pre-load is applied. The numerical simulation employs a bi-linear isotropic hardening constitutive law governed by the von Mises yield criterion. The simulation also considers the nominal temperature of the nutLIW-rock bolt connection. Therefore, a long-term relaxation effect on bolt pre-tension as a result of stress relaxation is neglected. The compressive force required to achieve the LIW-predetermined deformation is the bolt pre-tension. It is drawn from the simulation results that the 1.5-, 2.0-, 3.0-, 3.5-, and 4.0-mm-thick LIWs are completely flattened when subjected to 28-, 42.5-, 65-, 76-, and 88-kN pre-load respectively.

By M. Kuchta

A linear integer programming (MIP) model to solve the long-and short-term production-scheduling problem for sublevel caving operations is presented. The MIP model is designed as a multi-time-period problem to provide monthly schedules that meet production, blending and sequencing requirements. One of the most important issues during the development of the MIP model was the requirement of sequencing between blocks. In this mathematical model, unique constraints that ensure sequencing of the production from sublevels are developed. A suggested method of handling a large number of variables is also given. The MIP scheduling model was implemented on a data set obtained from the Kiruna Iron Ore Mine located in northern Sweden. The initial MIP model implementation was successful and provided a solution that optimized resource recovery while meeting monthly and yearly production constraints. The scheduling results obtained based on the Kiruna Mine are further presented and discussed.

Jan 1, 2003

By ANGELA NAIR AVELAR, Reiner Neumann, PAULO R. G. BRANDÃO

Three types of apatite were identified by means of cathodoluminescence (CL) images in flotation concentrate and tailing samples from the Catalão Mine in Brazil. They are predominantly blue apatite, followed by green apatite and, less frequently, yellow apatite. The chemical compositions of these types of apatite were determined by electron microprobe analysis and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Blue and green apatite responded well to the process, thus remaining in the concentrate, while yellow apatite remained in the tailings. Yellow apatite has the lowest phosphorus pentoxide (P2O5 ) content and largest anionic and cationic sites substitution, followed by green apatite, whereas blue apatite is the most homogeneous, with highest phosphorus (P) and calcium (Ca) grades and lowest substitution level.

By R. V. Stewart

This chrysotile asbestos orebody is located near the northern tip of the Province of Quebec, Canada. It is some 1818 km (1130 mi) north of Montreal; 480 km (300 mi) north of the tree line and is situated within the zone of continuous permafrost. The open pit ore zone is approximately 0.4 km (1/4 mi) in length some 61 m (200 ft) in width and plunges at 25-30 below surface to a vertical depth of at least 610 m (2000 ft). The orebody was originally evaluated by programs of surface mapping, diamond drilling and bulk sampling. The fibre is semi-crude, possesses excellent strength, and good fibre length distribution.

Jan 1, 1978

By Mostafa Benzaazoua, Bruno Bussière, Mukendi Kongolo

The desulphurization process has been proposed over the last few years for acid mine drainage control at certain mines, which generate low to medium grade sulphidic tailings (-3 to +25 wt% S). The environmental sulphur recovery, which means the sulphur to be floated to produce a non-acid generating final tailings, depends mainly on the intrinsic neutralizing potential of the tailings. However, in some cases the sulphur cleaning is complicated by other parameters which affect the flotation probability of the sulphide particles. In this study, a number of tests were conducted with a Hallimond tube and Denver Cell on both pure mineral and mine tailings. To develop a better understanding of the mechanisms of non-selective sulphide flotation, three types of approach were investigated in this work: (i) pure pyrite at progressive milling degrees, (ii) artificial mix of pyrite and quartz at different calibrated granulometry and (iii) same composition tailings with 26 % wt sulphur at progressive milling degrees. The effect of the granulometry on the sulphide flotation was demonstrated both. The results allow us to define a granulometry model, which can then be considered in the whole desulphurization modeling.

Jan 1, 2000