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By R. Brändle, R. Luis-Fonseca, R. Cornejo, G. Fischer, G. Von Rickenbach, J. Jarufe

Rock damage around underground excavations has been an important hazard in mines and tunnels. Rock dilation generates buckling that needs to be contained before it causes damage to equipment or safety concerns to mine workers. In seismically active mines, rockburst occurrence has been widely recognized as one of the most important hazards in deep mines and tunnels. While there is a wide range of cases where rockburst hazard can be mitigated through dedicated excavation sequences, reentry procedures or exclusion zones, there are still many situations where large unexpected rockbursting may occur, relying only on rock support as the last mitigation measure to prevent production and safety losses. Considering the previous situations, surface support as mesh, plays a major role containing the failed/ejected rock and providing a safe working environment to the underground operations. While there have been considerable achievements in improving mesh resistance, with more than 26Kj/m2 of energy dissipation capacity, there is still a lack of research in the overlapping mechanism and load transfer between contiguous mesh elements. This paper presents the state of the art in static and dynamic analysis of welded and rolled mesh overlaps, based on experimentation carried on by Geobrugg in their Research Center, leaving clearly established that the difference in meshes is not only in levels of energy absorption, but also concluding that in the case of high resistance rolled meshes overlapping is not necessary and the transmission of stresses can be fully guaranteed by using suitable connecting elements. All these characteristics, supported by operational advantages as light weight and mechanized mesh installation, provides a considerable improvement in safety and productivity, improving the economic value of the project

Apr 26, 2022

By John E. Shively, Tracy K. Lundin, Francis Fong

The Superconducting Super Collider (SSC) features two 20 TeV counter rotating proton beams which will be housed in 87 km (54 miles) of tunnel. Four additional lower energy particle accelerators will be housed in 26 km (16 miles) of tunnel and underground structures. Physics experiments will be conducted in two underground detector halls approximately 67 m (220 feet) deep with footprints measuring about 30 m (100 feet) by 100 m (330 feet). Definition and design of underground facilities is advanced with construction of approximately one-third of the SSC program underway. This paper presents an overview and status of the SSC project.

Jan 1, 1993

By E. A. Barrett, L. L. Rethi

Throughout all segments of the United States mining industry, 163 independent contractor employees were fatally injured between 1990 and 1997. Factors that contributed to these injuries were identified after reviewing descriptive information contained in Mine Safety and Health Administration fatality reports for each of the incidents. Thirty-three unique contributing factors were identified and multiple factors were noted for each fatality. Those most frequently discerned were "failure to follow `standard operating procedures"', (35% of the fatalities), "poor positioning of employee" (26% of the fatalities) and "failure to maintain equipment" (23% of the fatalities). Contributing factors were then associated with the accident and job classifications of the victims. Factors having the highest frequencies in the top five accident classifications where most fatalities occurred were as follows: powered haulage - "failure to maintain equipment"; machinery - "poor positioning of employee"; slip/fall of person - "inadequate fall protection" and "failure to wear safety line"; electrical - "equipment contact with power line"; and falling/rolling/sliding rock - "poor positioning of employee. " Among the job classifications in which most fatalities occurred, leading contributing factors were as follows: truck driver - "failure to follow standard operating procedures" and "poor positioning of employee"; laborer/utility man/pumper - "poor positioning of employee"; mechanic/ repairman and welder - "failure to follow standard operating procedures." Recommendations for utilizing contributing factor information as a basis for safety training are proposed. Training programs may be developed that inform independent contractor employees of factors which, in the past, have contributed to fatal injuries in their job classifications. Then, by combining this information with contributing factors identified in "related" accident classifications, a truly focused training intervention that addresses very specific workplace hazards may he developed.

Jan 1, 2002

By James P. Savely

This paper describes the development of a trim blast design to improve the stability of a final pit wall. Description is given of the effects of rock characteristics, rock type, and pit plans on the blast design. Currently, six benches have been mined with trim blasting. A more stable final wall has resulted and the successful program has reduced mining costs over an extended time period. Low cost blast monitoring and field observation were used to determine peak particle velocity and blast damage. Using criteria developed from this relationship, trim blasts were designed and evaluated.

Jan 1, 1986

By Alain A. Sonntag

The MBS Solvent Extraction System utilises a unique design of mixer- settler having very high capacity per unit area and great flexibility. The development of the mixer-settler is traced through its various stages wherein the independence of mixing and pumping, reduction in settler area requirements and simplicity of plant layout were achieved. The laboratory, pilot plant and full scale tests contributing to the development of the machine are described. The existing KREBS SX plants in Europe and Africa are described as well as the plants presently under design. Results of recent testwork are also given.

Jan 1, 1981

By G. Castillo, J. Mortensen

"INTRODUCTION Molybdenite is typically produced as a co-product in the copper ore flotation process. At the Rio Tinto Kennecott Concentrator (RTKC) in Copperton, Utah, the molybdenite is initially floated with copper sulfides and other value minerals producing a Cu-Mo concentrate. This is then separated in the molybdenum plant by depressing copper sulfides and pyrite and floating only molybdenite. The molybdenum plant in RTKC comprises the rougher circuit and several stages of cleaning to achieve a certain grade requirement of Mo. The rougher circuit is where the first stage of separation occurs. Cu sulfides and pyrite are depressed in the rougher circuit by adding NaSH under nitrogen and in the cleaner circuit by adding NaSH under air. The depression of Cu sulfides (and pyrite) by NaSH is related to the redox activity1. It is important therefore to maintain a reducing potential in the circuit in order to achieve effective Cu-Mo separation. If the rougher circuit is under air, like RTKC’s molybdenum cleaner circuits, it is harder to maintain the target redox potential because NaSH oxidizes rapidly in the presence of air thereby increasing NaSH consumption significantly. CU-MO SEPARATION AND ROLE OF PULP POTENTIAL The collector adsorption on copper sulfide minerals is through an electrochemical mechanism2. The collector changes the surface chemistry of the Cu mineral allowing it to float. Molybdenite, or MoS2, on the other hand, floats readily in the presence of a frother as it is naturally hydrophobic. Usually, hydrocarbon oil extenders such as diesel or burner oil are added to enhance Mo recovery. In order to effectively separate Cu from Mo, the collector complex on the copper surface needs to be destabilized or desorbed using a reducing agent such as NaSH or Nokes. As long as the circuit is under highly reducing conditions, the collector remains detached from the sulfide mineral surface allowing Cu sulfide depression. Therefore, it is important to measure the oxidation-reduction potential (ORP) continually and maintain the reducing condition with addition of NaSH. For a given collector each mineral will have a characteristic potential or electrochemical window for flotation to occur3, therefore, it is necessary to reduce the potential outside of this window in order to effectively separate Cu and Fe sulfides from MoS2 minerals2. In RTKC plant, the target reducing condition is between -450 to -550 mV to effectively destabilize the collector and depress Cu and Fe minerals. Typically the dosage of NaSH used in the molybdenum plant could range from 6 to 30 gallons/min (gpm). The high dosage of NaSH could pose risk of H2S exposure. RTKC wanted to evaluate alternatives to NaSH in order to reduce its consumption and minimize risk of H2S gas generation."

Jan 1, 2016

By D. Hodouin

Abstract. Dynamic experiments were performed in a continuous open-circuit 40x40 cm ball mill using a pseudo-random binary sequence of the feed rate and measuring the variations of the discharge particle-size distribution. The impulse response is calculated by a cross-correlation technique. Then a model involving a discrete transfer function and a time-series stochastic equation is calibrated using maximum likelihood methods. Based on this empirical model. a minimum variance controller with constrained input is designed and its performances are compared. by simulation, to the performances of a conventional PID regulator.

Jan 1, 1987

By T. P. Meloy

In the last decade increased and prolonged interest has been displayed in the use: of tunneling or rapid excavation to solve many of the urban and industrial problems confronting our society. There has been talk and action on the interurban rapid transit systems for major cities, and even preliminary designs for a Boston to Washington interurban transit system. Much of this interest stems from the search to the solution of our increasingly complex urban problems, where the surface area must be given over more and more to the inhabitants, and the subsurface for transit, utility and other services. While tunneling is not a panacea to urban ills it holds a real solution to many existing problems. There is also, among the tunneling experts, a growing confidence that technical problems of rapid tunneling can be solved. To solve these problems, R & D money must be invested. If it is to be money invested either by private industry or governments, there must be significant returns on the investment to justify the research and development need to bring about the breakthrough that will make tunneling a major contribution to the solution of urban problems. To make these economic studies more extensive and more accurate tunneling demand figures were needed. To this end, the Organization of Economic Cooperation & Development - OCED - included in its Conference on Tunneling a section on tunneling demand. As a result of the conference the organization for Economic Cooperation and Development issued a report entitled "The Advisory Conference on Tunneling - Report on Tunneling Demand 1960-1980. " This report was presented at the OCED Conference on Rapid Excavation, held at Washington, D.C. To obtain the data in the Report, questionnaires were sent to the OCED countries and 18 replies were received from Australia, Austria, Belgium, Canada, Denmark, France, Germany, Ireland, Italy, Japan, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom, and the United States. While it is true, that data were missing, that sometimes the definitions were confused, and that several countries provided no cost estimates at all, in general, this report contains the most comprehensive gathering of data that ever existed in the field. All data in the OECD report is expressed in terms of meters or cubic meters, and costs are in U.S. dollars.

Jan 1, 1970

By N. Arbiter

Evidence for the floatability of sulphide minerals without collector is analyzed and it is shown that results obtained with ores, in contrast to those with single minerals or mineral mixtures, depend on many additional variables, some identified and others not. Because of the prevailing low levels and costs of collectors for most sulphide ores, it is unlikely that collectorless flotation will have commercial applications, so that continued research on the subject may be justifiable on theoretical but not on practical grounds.

Jan 1, 1993

By Robert K. Jones

Filter media can be defined as that material which effects the removal of finely divided solids from a fluid. Thus the removal of dust from air or turbidity from water, for example, can be the result of passing the fluid through a properly supported filter media. Since filtration in one form or another has been practiced since pre¬historic times filter media have been made from an extremely wide variety of materials. Vegetable and synthetic fibers (used loose, or formed into papers, felts or cloth) sand, ground coal, diatomite, perlite, wire cloth, porous metal, and bonded aluminum oxide are among the more important materials used today.

Jan 1, 1961

By I. Fafoutis

Laboratory column studies were conducted in order to assess the effectiveness of slag and red mud reactive barriers for cleaning up leachates generated at mining and waste disposal sites and loaded with copper and manganese. Solutions containing the metals of concern were prepared by dissolving the required quantities of CuSO4?5H2O and MnSO4?H2O in distilled water so that Cu concentration was 100 ppm and Mn 20 ppm. Flow rates of 25 mL.h-1 for Cu solution and 75 mL.h-1 for Mn solution were used in order to simulate aquifer water velocities of 1 ft/d and 3 ft/d respectively. Solutions were pumped upflow, in Plexiglas laboratory columns filled with each reactive medium, using peristaltic pumps. Measurements of middle and outflow column pH, redox potential, conductivity and elements concentration were performed to provide information regarding removal mechanisms for both elements and exhaustion/inactivation rates for each reactive medium. Both reactive media showed fairly good removal efficiency over the period studied. Copper was mainly removed by precipitation and formation of Cu(OH)2 while removal of manganese was due to precipitation of Mn(OH2).

Jan 1, 2006

By E. J. Wade

My subject is gold price forecasting and monitoring as an important aspect of gold marketing. While I 'm specifically addressing gold, it is understandable that many other commodities could be readily substituted. Gold marketing must be studied as three distinct processes, and it is my intention to cover each of these processes in turn. First I?ll cover the process of gold price monitoring and forecasting in some detail. In order to select a method, or combination of methods, to be used to sell gold a determination of the future price profile is essential. The profitability of the sales effort will be determined, to a large extent, by how accurately the future price behavior of the gold market has been forecast.

Jan 1, 1985

By Rajiv Hadkar, M. D. McKinley, J. B. Hiskey, B. J. Scheiner, G. W. Warren

Flyash from municipal solid waste incinerators containing roughly 13 to 15% Zn, 2% Pb and 0.2% Cd is an attractive material for simultaneous metal recovery and detoxification. Results have shown that Pb in flyash is present as PbSO4 and PbC12 and that about 70% of the Zn is present in the form of soluble amorphous compounds. Leaching results in a number of acid and basic lixiviants show that acid leaching is clearly more effective than basic leaching which is limited by low solubility of Cd and Zn. Cementation in acid solution with pH < 1 promotes redissolution of the precipitated metal. Successful zinc electrowinning from chloride leaching solutions has also been demonstrated, although Pb2+ and Na+ can be potentially detrimental. The presence of Pb2+ can prevent deposition of metallic Zn, forming zinc oxychloride, ZnC12.4Zn(OH)2, instead. High concentrations of Na+ can also result in precipitation of NaCl. This investigation has shown that hydrometallurgical treatment of MSW flyash through leaching, cementation and electrowinning is a potentially feasible method for simultaneous detoxification and recovery of metal values. Several issues have also been identified which would require further investigation for final process development.

Jan 1, 1993

By Brenton Cook, Nate Long, Larry Applegate, Aaron K. McCain

"The Northgate Link Extension project is the third phase of the Sound Transit master plan to extend light rail throughout the greater Seattle metropolitan area. When completed, the Northgate Link Extension will extend the existing light rail system north by about 7 km (4.3 miles) from the University of Washington to the Northgate neighborhood. A general overview of the project alignment is provided as Fig. 1. The project was funded by a combination of federal grants and allocations from local taxes. The general contractor on the project was JCM Northlink LLC (JCM), a joint venture between Jay Dee Contractors, Frank Coluccio Construction Company and Michels Corp. SoilFreeze, Inc. was retained as a subcontractor to provide ground freezing design and construction services.The project involved the construction of two parallel 5.5-m, 25-cm (18-ft, 10-in.) (inside) diameter tunnels using earth pressure balance (EPB) tunnel boring machines (TBM) and precast segmental concrete tunnel liners. The two tunnels maintained roughly the same elevation along the alignment and were spaced roughly 12 m (40 ft) apart (centerline to centerline). A total of 23 cross-passages connecting the two tunnels were included at approximate 244-m (800-ft) intervals. Cross passage excavations were elliptical in shape with dimensions of approximately 5.6 m (18.5 ft) in height and 5.3 m (17 ft) in width. The cross-passages were 5.8 to 6.1 m (19 to 20 ft) long as measured between the exterior of the tunnels at springline elevation. Cross passages were intentionally located directly beneath public right-of-ways thus avoiding buildings. Many of the cross passages were located beneath narrow roads in residential neighborhoods with mature vegetation, existing utility structures and piping and limited parking areas. Excavation and support for each cross passage was completed using the sequential excavation method (SEM).The subsurface soil and ground water conditions at the cross-passage locations were described in the Northgate Link Geotechnical Baseline Report (GBR) prepared by Jacobs Associates and the Northgate Link Geotechnical Data Report (GDR) prepared by Shannon and Wilson, Inc. Soils along the project alignment were glacially overridden and characterized as very dense or hard. Subsurface soils consisted of cohesionless sand and gravel (CSG), cohesionless silt and fine sand (CSF), cohesive clay and silt (CCS) and till and till-like deposits (TLD)."

Dec 1, 2018

By Ralph L. Merklin

One of the most commonly employed set of calculations in mill design and research is the material balance, known in wet beneficiation plants, as an Ore and Water Balance. For mill designers, the balance is one of the principal requirements in determining the proper size of launders, pipelines, process equipment, etc. In process development, one of the major goals is the establishment of an optimum balance. The usual procedure for calculating a material balance involves a manual technique utilizing reference tables, pre -obtained data, and a slide rule or desk calculator. With these, the engineer must perform a series of calculations which are repetitious in nature and time consuming. Figure I is the flowsheet of the grinding and flotation circuits for a copper concentrator. The initial ore and water balance was calculated manually and required approximately 24 manhours. Later, a number of changes were made in the balance, each of which required an average of 8 manhours.

Jan 1, 1967

By Ross W. Whipple

Applying geophysical techniques in potential geothermal areas has received: little attention in the United States, though it is widely used and accepted in New Zealand and Italy. In those countries it has been demonstrated that geophysical surveys can be useful in locating new geothermal areas and in directing test drilling programs. Geophysical studies in a thermal region can provide structural information and, if conditions are right directly; locate subsurface hot waters. They can give indications of sub-alluvial rock types and of the thickness of alluvial cover. In certain cases they can be used to estimate the power potential of a hydrothermal system.

Jan 1, 1963

By Richard A. Brown

The direct precipitation of uranium with hydrogen peroxide has been known since 1877. Commercial use of the process began in the 1960&apos;s. During 1967 the Bureau of Mines assisted the Climax Uranium Co., Grand Junction, Colorado in the development of a uranyl peroxide precipitation process to control a molybdenum impurity problem (1). Atlas Minerals, Moab, Utah has used hydrogen peroxide to control vanadium and sodium levels in their uranium concentrates since 1969 (2). Recently, the use of hydrogen peroxide by the uranium industry has grown, particularly since the increased demand for uranium has led to the processing of low grade ores. Impurities present in low grade ores can be concentrated with the uranium during milling and will substantially complicate the refining of uranium yellowcake concentrates. Consequently, commercial nuclear fuel processors have imposed stringent specifications and penalties to control these impurities. The ability to produce a pure uranium yellowcake can eliminate penalty or reprocessing costs. Hydrogen peroxide precipitation of uranium is specific and quantitative, producing a very high purity product.

Jan 1, 1980

By S. P. Singh

In order to understand the intricate nature of blast damage mechanism and to counter the associated problems, small scale blasting experiments were performed on hydrostone, concrete and granite. This was followed by a 2.4 m x 2.7 m (8&apos;x 9&apos;) drifting operation in a quartzite quarry. Interior as well as exterior damage was assessed by different techniques. On the basis of the experimental results, the effect of explosive characteristics on the damage was examined.

Jan 1, 1992

By M. J. Laurila

On-line analyzers have made possible the use of Fuzzy Logic Control (FLC) for local control applications in coal preparation plants. This includes FLC control of complete circuits such as heavy media vessels, cyclones and froth flotation. These circuits can be controlled in real time in a feedback control loop with an on-line analyzer. Control strategies can be readily developed using Statistical Process Control (SPC) techniques which are first applied off-line in manual mode through the use of control charts and then this process is brought on-line using FLC in conjunction with an on-line analyzer to fully automate the circuit. This paper outlines the types of control strategies employed and presents examples of automatic verses manual control.

Jan 1, 1997

By D. J. MacKinnon

Smooth, compact, dendrite-free, 24-h zinc deposits have been electrowon from zinc chloride electrolyte using a diaphragm cell. The cell consisted of sealed anode compartment con- taining DSA anodes which were separated from an open cathode compartment by Dynel cloth membranes. Fresh electrolyte was fed to the cathode compartment where zinc deposition onto an aluminum cathode was aided by air-sparging. The catholyte passed through the diaphragm into the anode compartment from which chlorine gas and spent anolyte were withdram.

Jan 1, 1980