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What decision making tools and methods are available to a project owner when there is no clear differentiator between construction alternatives? A team led by a joint venture of Parsons Brinckerhoff and PGH Wong Engineering (PB/Wong) has been providing preliminary engineering services to the San Francisco Municipal Transportation Agency (SFMTA). The SFMTA and PB/Wong team developed several alternative construction methods for the tunnels and stations of the San Francisco Central Subway Project, none of which could be judged clearly better than another using traditional approaches and metrics. The team employed a risk assessment and analysis frame-works as a means of comparative analysis, drawing upon the knowledge of industry experts in the geotechnical, tunneling and construction fields to assist in the effort. This paper presents the approach and results of a cost and schedule risk analysis for two such analyses designed to answer two different questions regarding the advisability of different construction approaches. These assessments paved the way for key decision making in the preliminary engineering phase of the project and formed the foundation for continuing risk management efforts on the project. The focus of this paper is primarily the first two stages of risk management?identification and assessment?and some of the organizational dynamic issues that arise in such efforts.

By F. F. Peng, Y. Xia

In modeling of hindered-settling bed separators, the published separation mechanisms are based on differences of particle density and size distributions, without the details of complexity of particles-liquid interactions. A fluid dynamic model for the separator is developed using Euler-Lagrange approach of Computational Fluid Dynamics (CFD). Fluid motion is obtained from solving the movement of liquid governing equations. The damping effect on flow pat-terns caused by the movement of particles resulted in liquid-particle coupling is included in the model. Effects of particle size, and particle density compositions, feed rate, feed water flow rate, upward fluidizing water flow rate, etc., are simulated in the 2-D separation model. Flow pattern effects on the separation of fine particles in the separators with center downward-flow and side cross-flow feed systems are investigated.

Jan 1, 2004

By Steven W. Hunt, Steven B. Fradkin, Roger J. Maurer

During the 1980s and 1990s, twenty deep shafts were constructed in Milwaukee to depths from 85 to 91 m (280 to 300 feet) through soil and weak rock thicknesses ranging from 37 to 69 m (122 to 227 ft). Adjacent compressible soils, settlement sensitive structures and high groundwater levels required that shafts be constructed without dewatering. Contractors attempted several methods of ground support and groundwater cutoff. Significant problems developed during construction of 11 of the 20shafts. One shaft collapsed; groundwater blow-ins occurred at five of the shafts; and seepage caused unfrozen windows at three of the freezewalls. Ultimately, combinations of grouting and ground freezing were utilized to complete all of the shafts into bedrock. This paper discusses the main design and construction challenges experienced and the lessons learned.

Jan 1, 2003

By E. S. Peterson, M. K. Harrup, K. A. Dolbeare, J. E. Wey

Efficient methods for removal of copper from heap leach solutions without mobile organic phases are a current mining industry need. To satisfy this need a selective, high-capacity, durable solid material is required. The INEEL has developed a set of materials based upon current solvent extraction chelates that provide selective copper concentration in the presence of high concentrations of iron. In contrast to conventional solvent extractions, our strategy anchors the chelators to a non-polymeric solid substrate through the use of a custom designed linker molecule. The fundamental synthetic routes to these materials have already been established and attachment to the solid surfaces achieved in an efficient manner. Our continuing research is focused on the optimization of the synthetic pathways to these solid materials and the evaluation of their copper capturing capabilities.

Jan 1, 2002

By Jerry C. Tien

An overcast is a form of air bridge which permits one air current to pass another without mixing. It is an essential and indispensable ventilation device for underground air distribution in horizontal mineral deposits. Overcasts are also a major source of shock pressure loss under- ground. However, a well thought out overcast plan, and a well constructed overcast, will give minimum shock loss, which in turn can save money (Tien, 1986). So far, most research on shock losses has been concentrated on splits and junctions, and bends and turns, or on underground regulators. Practically nothing could be found in the literature regarding losses caused by overcasts (see reference on shock losses). In this investigation, shock losses are quantified for an overcast with different configurations, which will give useful clues toward an aerodynamically designed overcast.

Jan 1, 1987

By J. R. Sturgul

A dynamic input-output model for a coal power enterprise that now includes four underground coal mines, three coal washing plants, a power plant and a railway transportation system was developed. The model is applied to analyze investment alternatives for long-term development, including the expansion of existing mines, the opening of new mines, the construction of new coal washing and power plants and the upgrading of the railway system. As a result, the optimal investment strategy with capital schedules and projected sector outputs is obtained. Also, the importance of the new power plant to the strategic development of the company is demonstrated. It is concluded that, without applying a dynamic input-output model, it would be much more difficult or impossible to conduct such a systematic and compete analysis.

Jan 1, 1999

By John L. Watson, Suren Mishra

Many of the wastes produced by modern steel plants are pulps or sludges containing significant concentrations of iron and displaying some ferromagnetic characteristics. These waste materials are often suited to treatment by magnetic cycloning to produce a high solids content underflow and a clean water overflow. Alternatively in the classification mode, the magnetic cyclone can produce a high iron underflow product for recycling by discarding fine non-magnetic material to the overflow. Results for the treatment of a variety of steel plant wastes in 5.0cm, 2.5cm and 1.25cm diameter cyclones, operating with and without an applied magnetic field, are presented. It is demonstrated that the magnetic cyclone increases solids recovery to the underflow product, especially at finer particle sizes and for higher solids content feed pulps.

Jan 1, 1992

By A. Bhagavatula, M. Rezaee, M. J. Kiser, R. Q. Honaker

"A field study of the coal preparation plant fleet in the eastern United States was undertaken to determine if quantify of rare earth elements (REEs) present in the product streams are large enough to justify further concentration. Representative composite samples were taken from the clean product, coarse refuse, and fine refuse streams from 20 coal preparation plants. Each stream was then separated into various size and density classes and analyzed for ash and REE contents. The large database showed that coarse refuse contained the largest amount of REEs, although the ratio of heavy to light REEs was greater for the clean coal products. The concentration of REEs was also compared to that typically seen in the earth’s crust. This enrichment ratio ranged from approximately 1.5 to more than 4.0 as the ash content varied. The database also showed that a linear correlation existed between La and Ce for many REEs of interest, although there were several notable exceptions for some of the high-value REEs. INTRODUCTION Worldwide energy demand is expected to grow by as much as 37% by 2040 according to the International Energy Agency (2014). This growth, coupled with a decrease of the reliance on coal to generate energy, means that it is more important than ever for countries to secure the materials necessary to meet its energy projections. For the United States, the U.S. Energy Information Administration (EIA) predicts that total domestic electricity use will increase roughly 25%, from 3,836x109 kWh in 2013 to 4,797x109 kWh in 2040 (EIA, 2015). In the EIA’s reference case, coal’s contribution to electricity generation drops from 39% in 2013 to 34% in 2040. On the other hand, renewables share of electricity generation grows from 13% to 18% for the reference case. Compared to its current state, renewable energy electricity production is predicted to grow as little as 50% to as much as 121% over this time period, depending on the economic case being examined. This growth will largely be seen in the wind and solar sectors (EIA, 2015). The focus on viable renewable energy resources will be crucial to the future of fueling American growth. Many of the renewable energy technologies, such as wind turbines and photovoltaic films, rely on materials and supply chains outside of the United States. The lack of a reliable and low-cost domestic supply could pose a threat to the growth of the renewable energy markets in the United States. This potential vulnerability recently led the United States Department of Energy (DOE) to create a Critical Materials Strategy Report. In this report, 15 elements were identified as critical for the continued growth of the renewable energy market. Eight of these elements were rare earth elements (REEs). Five REEs (dysprosium, neodymium, terbium, yttrium and europium) were identified as highly critical and vulnerable to shortages (Bauer et al., 2012)."

Jan 1, 2016

By Deepak Gupta, Brij M. Moudgil

Attempts were made to improve the recovery of coarse phosphate particles by adding selected frothers or precoated fine particles. A number of frothers for floating, specifically coarse coal and metallic minerals, were examined. Two of the frothers increased the flotation recovery of coarse phosphate by 3% on bench scale. Plant evaluation yielded improvements in overall phosphate recovery in the presence of these frothers. Addition of fine particles was also found to enhance coarse flotation under given conditions. Size, amount, and hydrophobicity of the fines added was determined to have a major influence on the coarse flotation efficiency. The grade of the product with and without frothers and particulate additives remained the same. Change in froth stability and viscosity are believed to be the primary reasons for enhanced recovery of coarse phosphate particles.

Jan 1, 1989

"The adsorption of mixed cationic/anionic surfactants with different molar ratios onto quartz was investigated. The cationic surfactant used was dodecylamine bromide (DDA), and the anionic surfactant was sodium oleate (NaOL). The critical micelle concentration values for the individual surfactants and their corresponding mixtures were determined using a platinum plate. The adsorption mechanisms of mixed surfactants on quartz were studied using contact angle measurements, flotation tests and adsorption amount measurements. At alkaline condition, NaOL depresses DDA flotation of quartz without depressing the adsorption of DDA. The molar ratio of mixed surfactants is found to be a key factor in the orientation of alkyl chains and thereby the flotation response of quartz. A mixture of 1/2 or 1/3 DDA/NaOL forms on the surface of quartz when the concentration of NaOL is higher than that of DDA. The adsorption of the mixture decreases the wetting of quartz since the alkyl chains are in chaotically orientation with a conceivable number of head groups directing towards the solution phase. These results provide important insights into the adsorption of mixed surfactants onto quartz surface. INTRODUCTION Froth flotation is known as an effective method of separating mineral particles on the basis of their surface chemistry, specifically their hydrophobicity. [1]. The hydrophobic particles will attach to the bubbles and rise to the top of the containing vessel to form a froth that flows over the lip of the vessel. The hydrophilic particles remain in the liquid [2]. In the process, surfactant is often used as collectors for surface modification in order to change the wetting properties of mineral particles. The primary long chain alkyl ammonium salts are the most widely used as collectors for the flotation of oxide minerals, such as quartz, muscovite, hematite, phosphate and feldspar [3, 4]. Adsorption mechanism of alkyl ammonium salts on oxide minerals has been extensively analyzed [5, 6]. Generally, the ammonium salts are adsorbed through electrostatic interaction of the polar group of the molecules with the surface of these minerals [7]. Despite many obvious advantages of the ammonium salts in low temperature resistance and hard water resisting, however, their unavoidable drawbacks, such as high sensitivity and poor selectivity for slimes, relatively high cost, have limited their applications [8]. In recent years, mixed surfactants have drawn much attention due to their superior physicochemical and surface properties than single surfactants [1, 9-11]. They have been used in many industrial processes such as dispersion/flocculation, flotation, detergent, corrosion inhibition, cosmetics, foods, paints, chemical mechanical polishing, enhanced oil recovery, and nanolithography [12]. Most of the mixed surfactants have synergistic advantage in reduction of the surface tension and critical micelle concentration (CMC); therefore, they exhibit spurious properties, like excellent surface/interfacial activities, and are less expensive than single mixed surfactant systems [13, 14]."

Jan 1, 2016

By V. I. Lakshmanan

Crystalline Flake Graphite is a strategic mineral. Since 1954 nearly all North American consumption has been imported from offshore. The Bouthillier Project in Quebec, Canada, is Orrwell Energy's bid to enter the market. Milling of flake graphite is considered easy, yet more problems have been encountered in flowsheet and plant design than in most other minerals. A fresh approach to existing technology was taken, giving results that are highly satisfactory. The key to graphite liberation without flake deterioration is found to be in autogenous grinding. In addition to producing marketable coarse graphite by such autogenous grinding, flotation and tabling, super purity fines can be produced using repeated regrinding, elutriation and flotation. This paper discusses the design of a 500 TPD plant based upon the results obtained from bench and pilot plant studies.

Jan 1, 1984

It was shown previously that chalcopyrite could be floated without using a collector when the ore samples were treated with small amounts of sodium sulfide (Na2S). The role of this reducing agent was considered to be one of a cleaning agent to remove the hydrophilic surface oxidation products. It was later found, however, that the collectorless flotation could be obtained only under slightly oxidizing conditions. This might suggest that collectorless flotation is not due to the clean surface but to the elemental sulfur which may be present as an incipient oxidation product. Therefore, a search for the presence of elemental sulfur has been made by means of ESCA, mass spectrometry, and solvent extraction followed by W spectrophotometric analysis. On the basis of these results, the mechanisms of collectorless flotation are discussed.

Jan 1, 1983

By G. Bezuidenhout

The newly developed Bateman Flotation Machine has proven its versatility in roughing and cleaning flotation circuits. This mechanical flotation machine has the dual performance capability of suspending solids and dispersing air at relatively low power inputs without compromising these two important fundamentals. This new development has been successfully marketed to a wide cross section of concentrator mineral processes. The mechanical design of the flotation mechanism has been optimised to reduce operational costs and to lower manufacturing costs. Production process environments were utilised for verification of the scale-up of each cell volume size rated mechanism. These thorough investigations produced performance data which could be accurately quoted. This paper is a historical account of the Bateman Flotation Machine. Technical details of the development are covered with descriptions of the operational applications.

Jan 1, 1995

By P. R. McOllough

The Colorado Department of Highways awarded a contract to construct the Second Bore of the Eisenhower Tunnel in August, 1975. The contract was completed June 29, 1979, nine days ahead of schedule, with¬out major claims or delays. The tunneling involved complex construction through difficult ground conditions. The contract, plans and specifications were specifically planned to more equitably share the risks involved and to minimize adversary relationships. The Department produced a detailed tunnel design and maintained responsibility for the design. The contract employed some new provisions; e.g., a review board for settlement of claims and disputes; escrow documents (contractor's bid documents) to determine the contractor's basis of bid when determining adjustments. The tunnel contract, plans and administrative efforts employed by the owner and contractor were very successful in this project.

Jan 1, 1981

By C. Newman, N. Schaefer

"As underground mining continues to operate at deeper depths and in more complex geologic and geometric conditions, there has been an increased demand for mine designs to better reflect site-specific conditions, measurements, and observations with respect to ground control safety and stability. During the past 20 years, the National Institute for Occupational Safety and Health (NIOSH) has developed, validated and distributed a number of free software packages (ALPS, ARMPS, AMSS, ARBS, etc.) specifically aimed at providing the industry with ground control design tools for the evaluation of underground stability in coal mines. While these programs were initially developed as stand-alone software packages where all data reside on an individual or workgroup computer, modern day web applications have begun to migrate toward a “multiple-tier” architecture, allowing multiple users to access an application by means of an Internet connection.This article introduces a new Web-based platform for ground control software applications, webGroundControl (webGC). webGC provides users with a platform through which one can access NIOSH and other ground control design software utilizing a Webbased, multiple-tier architecture. This provides users with easy access to ground control designs, the ability to perform on-demand calculations, as well as increase online collaboration between operational personnel and engineers through a web server. The basic framework and, more specifically, the user-interface of webGC are defined and outlined within this paper. It is expected that the mining industry will rapidly embrace this new product and webGroundControl will be a new paradigm for mining engineering computer applications. Platform architectureAs Web-based computing technologies continue to advance and cloud computing gains momentum, web-based platforms for software applications are growing in popularity across all industries due to ease of product accessibility and distribution as well as data security. With the expansion of Internet connectivity on the surface and underground, there is an industry need to develop Internet-based applications for mine and ground control design (Barczak et al., 2016). Cloud-based products are already available for many industries and are slowly being developed for the mining and geotechnical industry. A notable example is the drillysis package, which is a cloud-based borehole logging database (Geosysta, 2017) or the Dynonobel package for on the fly blasting calculations (Dyno Nobel, 2013)."

Jan 10, 2017

By K. Hansson, A. Jedborn

Background In the mining industry, conversion of fine particles into a slurry is often part of the normal processing of the ore. Therefore, from a system's point of view, slurry transporta¬tion would be considered as a natural alternative, all the way from the working face to the final processing. In underground mines, there is sometimes a considerable inflow of ground water that has to be pumped out. When the mine dewatering installations are integrated with a hydraulic hoisting system, the cost of power needed to pump out the ground water can be excluded from the cost of hoisting, compared with other modes of transporting the solids to the surface. The chief advantage of hydraulic hoisting is that the hoisting capacity can be increased at comparatively low total cost without necessitating the sinking of new shafts. Alterna¬tive examples include deepening of the existing mechanical hoisting system, truck, or conveyor belts transport in ramps to the present level. These often become very expensive. The economic effectiveness of hydraulic hoisting and hydraulic design considerations have been discussed by Kostuik (1965) and Sellgren (1985, 1986) for both small shallow mines and large deep underground mines. Objective and scope The objective of this study was to demonstrate the feasi¬biliy of hydraulic hoisting in hypothetical examples of mine deepening. Underground grinding to a maximum particle size of about 700 um (about 25 mesh) is considered. The pumping of ground ore products with positive displacement plunger or membrane type of pumps at working pressures of up to 15 MPa (2200 psi) is a thoroughly tested technique (Venton, 1986). Hydraulic hoisting system A hydraulic hoisting system is described schematically in Fig. l . The ore is mined, handled, and crushed conventionally. It is then ground wet underground. The slurry is then tempo¬rarily stored in an agitated tank and pumped to an agitated receiving tank on the surface. The ore is then further processed in the concentrator. The capacity of a pipeline is very high. For example, an annual production of 500 Kt (550,000 st) of ore can be handled in a 100-mm-diam (4-in.-diam) pipeline. Systems layout - economic effectiveness Schematic mine layouts are presented that represent situ¬ations where hydraulic hoisting often is the most economical alternative. A situation where the ore is trucked to the level of the existing hoisting system is shown in Fig. 2 (following page). With hydraulic hoisting, only a shaft for ventilation, pipe¬line, and personnel are needed. In a first phase (Fig. 2), a hydraulic hoisting installation with crushing and grinding units, storage facilities, and pumps has been located at a level of about 400 to 600 m (1310 to 1970 ft) below the surface. With further development of the mine, the hydraulic hoisting

Jan 1, 1989

By John W. Rushton

Maintenance and inventory are usually the last items considered in mine development. They need to be addressed properly and early. The micro-computer brings sophistication within the reach of even the smallest mines. Maintenance and inventory programs, if properly installed, will reduce costs 15 to 25% and allow management time to address the mining and metallurgical problems at start up. Shops and warehouses are rarely designed properly. Large engineering firms spend 5 to 20 times more than is necessary for first class facilities. There is an optimum design, size, and layout. Take the time necessary to assure you get the right people, programs, and facilities in that order. Maintenance, inventory, and inventory control must be addressed early if a small mine is to have a chance at optimizing costs during the first two years of operation. This is hard work and is usually put on the back burner until the mine is in some degree of trouble. Hiring an experienced maintenance superintendent is important but it is not the complete solution. Maintenance systems, design of facilities, and use of computers are not skills that maintenance people usually have. In addition, the work of ordering spare parts and working with erection people is a full time job and any maintenance people on site during construction are quickly recruited. The end result is that few mines start up with an adequate Maintenance or Inventory System in place. The months, and in some cases years, that the mine attempts to operate without a system are both painful and expensive. Designs of successful integrated maintenance and inventory programs are virtually 100% supported with some outside assistance. Our system is the approach that we are most familiar with and this paper will isolate how Rushton International would go about setting up systems and designing support facilities. Micro-computers are the only way for a small mine to go. ~ini-computers cost more originally and operating costs are many times higher than even the most sophisticated micro system. Micro- computer software is developed further and recent advances in hardware makes medium priced units equal to most mini's in RAW COMPUTER POWER. Mines in general, and especially small mines, have no need for main frame power. MAINTENANCE A good maintenance program has: 1. Equipment Master List a. Equipment Detail Reports 2. Work Order and Backlog Control Program 3. Component Control Program 4. Tire Program 5. Wear Materials Program 6. PM Control Program 7. Maintenance History Program 8. Performance Program We also track miscellaneous items such as MSHA training and inspections, timekeeping, etc. Rather than going through the program step-by-step, it makes more sense to go through a typical Maintenance Day and show how the programs are used. The first thing maintenance supervision needs to know is "how we are doing." We

Jan 1, 1987

By Anders Sellgren, K. Hansson, A. Jedborn

In the mining industry, conversion of fine particles into a slurry is often part of the normal processing of the ore. Therefore. from a system's point of view, slurry transportation would be considered as a natural alternative, all the way from the working face to the final processing. In underground mines, there is sometimes a considerable inflow of ground water that has to be pumped out. When the mine dewatering installations are integrated with a hydraulic hoisting system, the cost of power needed to pump out the ground water can be excluded from the cost of hoisting, compared with other modes of transporting the solids to the surface. The chief advantage of hydraulic hoisting is that the hoisting capacity can be increased at comparatively low total cost without necessitating the sinking of new shafts. Alternative examples include deepening of the existing mechanical hoisting system, truck, or conveyor belts transport in ramps to the present level. These often become very expensive. The economic effectiveness of hydraulic hoisting and hydraulic design considerations have been discussed by Kostuik (1965) and Sellgren (1985, 1986) for both small shallow mines and large deep underground mines. Objective and scope The objective of this study was to demonstrate the feasibiliy of hydraulic hoisting in hypothetical examples of mine deepening. Underground grinding to a maximum particle size of about 700 um (about 25 mesh) is considered. The pumping of ground ore products with positive displacement plunger or membrane type of pumps at working pressures of up to 15 MPa (2200 psi) is a thoroughly tested technique (Venton, 1986). Hydraulic hoisting system A hydraulic hoisting system is described schematically in Fig. 1. The ore is mined, handled, and crushed conventionally. It is then ground wet underground. The slurry is then temporarily stored in an agitated tank and pumped to an agitated receiving tank on the surface. The ore is then further processed in the concentrator. The capacity of a pipeline is very high. For example, an annual production of 500 Kt (550,000 st) of ore can be handled in a 100-mm-diam (4-in.-diam) pipeline. Systems layout - economic effectiveness Schematic mine layouts are presented that represent situations where hydraulic hoisting often is the most economical alternative. A situation where the ore is trucked to the level of the existing hoisting system is shown in Fig. 2 (following page). With hydraulic hoisting, only a shaft for ventilation, pipe- line, and personnel are needed. In a first phase (Fig. 2). a hydraulic hoisting installation with crushing and grinding units, storage facilities, and pumps has been located at a level of about 400 to 600 m (1310 to 1970 ft) below the surface. With further development of the mine, the hydraulic hoisting

Jan 1, 1990

By J. C. Yingling, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is over-compacted. Research has shown that excessive compaction in replaced growing media is detrimental to establishment of trees. If trees are to be grown on reclaimed surface mined sites, something must be done to alleviate this excessive compaction. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed growing media. The University of Kentucky has developed test cells on reclaimed sites at a surface mine in eastern Kentucky to determine the impact of tillage (ripping) on soil compaction and tree survival rate. The ripping methods being evaluated include shallow tillage using conventional farm equipment and deep tillage using a dozer with a ripping arm. The impact of organic soil supplements on soil physical properties and tree survival rates is also being evaluated at the site. The organic soil supplements being evaluated include application of hardwood bark and application of straw and mulch. Each test cell has been planted with various species of trees, and for the first two years, data have been collected at these test cells for soil dry bulk density, penetration depth and resistance, and survival rate of trees. These data are currently being correlated to determine how ripping and the application of organic soil supplements affects the relationship between soil compaction and tree survival rate.

Jan 1, 2002

By P. Conrad

Experience has shown that, since the passage of the Surface Mining Control and Reclamation Act, over-compaction of spoil during the reclamation process has severely limited tree growth on reclaimed land. Researchers at the University of Kentucky have conducted a ten-year investigation at a surface mine in eastern Kentucky that monitored the changes in selected spoil physical characteristics for various reclamation and compaction alleviation methods. More specifically, research plots were developed for reforestation that employed three different levels of compaction and two different methods of ripping for overly compacted spoil. Each year measurements were made in the field of dry bulk density, using a nuclear density gage, and maximum penetration depth, using a recording cone penetrometer. In addition to good correlation between tree growth and selected spoil characteristics, the data demonstrated a gradual convergence of the measured spoil characteristic data over the study period.

Jan 1, 2008