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By Anita Wu

"GENERAL BACKGROUND/CONTEXT The £300 million Bond Street Station Upgrade project will provide essential congestion relief and step-free access to an important interchange and destination station in the heart of the London Underground network. In 2010 London Underground (LU) let a design & build contract to Costain Laing O’Rourke (CoLOR), with the works to be completed in early 2017. CoLOR’s lead designer is Halcrow-Atkins JV (HAT). The station upgrade works comprise the following principal elements: •,A new satellite ticket hall on the North side of Oxford Street •,Two additional escalators and stairs providing congestion relief to the Jubilee line platforms •,Four lift shafts to provide step-free access between the different levels of the station •,Additional stairs to Central line platform level •,Tunnelled connection to the Crossrail station immediately to the south •,Connecting passageways, including ten connections to existing station tunnels. To achieve this, an existing property at 354-358 Oxford Street has been purchased and demolished, and the basement deepened to make provision for the new ticket hall. From this basement two circular shafts have been sunk, providing construction access for the tunnelled passages and lift and escalator shafts. The tunneling is principally in the London Clay stratum, which is widely recognized as a favorable tunneling medium, although the deepest parts of the works extend into the Lambeth Group strata which consist principally of stiff clays at this level but also contain water-bearing sands. The majority of tunneling has been carried out using mechanical excavation and sprayed concrete linings but other techniques have been used in areas where SCL is not practicable.A key challenge for design and construction of the works has been spatial constraint, in particular due to: •,The existing underground station layout •,The Limits of Deviation for the works •,The small construction site at 354-358 Oxford Street •,Overlaying Third Party assets including Listed buildings, sewers and water mains."

Jan 1, 2016

By Q. Xu

The new process consists of the selective coalescence of fine hematite particles by fine magnetite. The gangue minerals are dispersed by some dispersant; thus it can be separated by desliming. This process is particularly suitable for fine-grained hematite/magnetite-type deposits.

Jan 1, 1989

By J. G. Nalven

On July 1, 1999, most domestic metal mines will have to report releases of toxic chemicals into the environment for the first time as required by SARA Title 313. Some of these reportable releases will appear huge in relation to reports by other industries. The reasons for the potentially large reportable releases, special considerations for mining operations, and strategies for dealing with the reports are described. Data composited from experience with several mining companies is presented in the context of a typical gold mine.

Jan 1, 1999

By Joseph F. Shirley

Introduction Inorganic depressants are chemicals added to the froth flotation process to maintain or produce hydrophylic surfaces on one or more minerals so they will remain in the pulp rather than attach to the air bubbles. Whether a depressant will be effective in depressing a given mineral depends on how it is used and the environment in which it is used. Some depressants must be added and conditioned into the pulp before the collector is added. Other depressants can be added in the presence of previously added collectors and effectively depress the desired minerals. Often the concentration of depressant relative to the collector concentration is critical to making an economic separation. It should be noted that some depressants will only work when specific collectors have been used. Some reagents such as sulfuric acid and hydrogen peroxide essentially act as depressants by altering the previously added collectors so that they are no longer effective. Some depressants such as sodium ferrocyanide are only effective in a very limited pH range and an essentially collector free environment. Major Depressants CaO Milk of Lime is by far the most used depressant both in tonnage and dollar value. Although it is most commonly listed as a pH modifier, it is also an important depressant for pyrite in copper and copper molybdenite flotation plants. Although a simple pH adjustment will often depress pyrite, there are times when grinding with fresh milk of lime is required to obtain optimum depression. Lime is also a molybdenite and gold depressant. NaSH Sodium hydrosulfide is by far the most commonly used reagent to depress copper and iron sulfide minerals in by-product molybdenite flotation plants. NaSH also depresses gold, silver sulfides and silver chloride. ZnSO4 Zinc sulfate is commonly used to depress sphalerite in lead-zinc and copper-lead- zinc flotation plants. It has also been used to effectively depress talc in by-product molybdenite circuits at a pH of 6.5.

Jan 1, 1986

By R. Gilliam

The Jewett Mine is located in two East Central Texas Counties, Leon County and Freestone County. The area is primarily suited for agriculture with approximately 90% of its agricultural income coming from beef cattle and hogs. In addition to livestock both of these counties produce hay, oats for grazing, pecans and corn. There are 1,101 farms and/or ranches in Freestone County consisting of 381,248 acres. Less than 15% of this acreage is harvested croplands. Leon County has 1,227 farms and/or ranches for a total of 442,387 acres, of which less than 13% is harvested cropland. Total annual agricultural sales for Leon County are approximately $36 million and Freestone County has approximately $21 million. Ninety percent of the annual agricultural sales derive from livestock.

Jan 1, 1992

By Edmund W. Murphy

At the first workshop on Surface Subsidence Due to Underground Mining (1 981 ) , Yarbrough delivered a paper (1 ) describing the mine subsidence insurance program in Illinois operated as the Illinois Mine Subsidence Insurance Fund (IMSIF) . In this paper we will present claims data and describe changes that have occurred in the Illinois Insurance Code during the first six years the IMSIF has been in existence. The change in the original Illinois Public Act 80-1 41 3 that most affected the public was an amendment increasing the maximum amount of mine subsidence insurance avail- able on a structure from $50,000 to $100,000. Seventy-two counties in Illinois have been undermined for minerals, primarily bituminous coal. In Franklin County (.in the southern part of the state) 36 percent of the land area has been undermined for coal extraction. In St. Clair and Madison Counties , two counties that include the St. Louis Metropolitan area along the western border of the state, 10 percent and 7 percent of the land surface have been undermined. Most of the undermined area in the two counties is beneath urbanized land. In 34 counties, approximately 1 percent or more of the land surface has been undermined (2). The first shaft mine in Illinois was sunk in the city of Belleville (east of St. Louis) in 1842, and the mines of early vintage have initiated the majority of the mine subsidence claims. Data compiled from the first six years reveals that most Illinois mine subsidence events that affect structures occur over abandoned mines where early methods of high- extraction mining practices were used. Maps of these mines operated in the 1800s reveal irregular development of room and pillar areas and poorly defined production areas (panels). Rooms in the mines varied from 15 to 40 feet in width and the pillars varied in width from 5 to 40 feet. The pillars were often long and narrow. Recovery rates in mines that operated prior to 1900 generally averaged 50 per- cent, and extraction rates as high as 80 percent have been documented (2). Some pillar robbing occurred.

Jan 1, 1986

By J. B. Fletcher

Miami Copper Company has used conveyor belts underground since 1947, At that time, the draw level for a portion of the orebody was only 25 feet above the haulage level To get the main haulage drifts as far away as practical from under the stoping area, 301, belt conveyors were used for lateral transfer, If the haulage drift was kept in good ground., a satisfactory draw of these stopes could be effected in that repairs to the conveyor drifts could be accomplished while drawing ore from the stopes. Some 7,400,000 tons of ore were mined with the 301d belt conveyor at a belt cost of approximately $0,004 per ton of ore. When the mining plan for a new section of the mine was laid. out in 1953, it was decided to use belts to collect the ore from the higher draw levels, and. move the ore laterally to centrally located concrete ore passes for transfer to the main haulage level (See Cut #1), The final plans used belt conveyors too collect from 3 stopes: on the 570 level, 2 stopes on the 720 level, and one stope on the 900 level. The six stopes to be mined in this manner would produce about 8 million tons of ore, and the sequence of mining was such that not more than four 400 feet conveyors would be in use at one time, Four conveyors using 36 inch, 4 ply belting were designed by the mine engineering office and fabricated at the mine shop, so that no piece was longer than 10 feet, and. the heaviest piece was the 25 horsepower motor, The head drive section, and the tail-pulley-takeup section were of bolted construction so they could be broken down for easing moving, Due to the size of the mine openings, the belt had to be transported into the mine in 400 feet rolls, requiring two splices for an installed belt. A torque arm speed reducer was used with a V -belt drive which made it possible to change the speed of the conveyor by changing the diameter of the V-belt pulley (See Cut #2).

Jan 1, 1958

By H Sohn, R. R. Fernández

Microscopic gold inclusions in sulfide minerals cannot typically be extracted by conventional cyanidation. The gold ore must be pretreated to oxidize sulfide minerals associated with gold and to remove other minerals and chemical compounds that interfere in the cyanidation leaching process. The recovery of gold from refractory sulfidic-carbonaceous ores after roasting pretreatment was studied. With the addition of an oxygen-containing gas (e.g., air or oxygen-enriched air), sulfides of iron, zinc. copper and other metals are tramformed into solid oxides or sulfates and gaseous sulfur dioxide at elevated temperatures (e.g., 400° to 800°C). When the sulfides are oxidized, individual particles lose internal volume and become porous, allowing leaching solutions access to the gold. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent on the roasting conditions and roasting method. The optimum combination of particle size, roasting temperature, reaction time and oxygen concentration in the off-gas was determined for a typical refractory sulfidic-carbonaceous ore from the Carlin Trend in Nevada. The tests were run using a 150-mm laboratory rotating tube furnace and 160- and 200-mm.fluid-bed pilot roasters. Laboratory results indicated that the maximum gold extraction was 92%, with the head and the leach residue containing 5.7 and 0.4 g/t (0.166 and 0.013 oz/st) Au, respectively. The maximum extraction was achieved under the following roasting conditions: a top particle size of 150 yin, a residence time of 2 hrs, a roasting temperature of 475°C and with 40% oxygen (by volume) in the off-gas. Similar results were obtained from circulating fluid bed (CFB) pilot-plant testing. The maximum gold extraction was 90%, with the head and leach residue containing of 5.1 and 0.5 g/t (0. 149 and 0.015 oz/st) Au, respective) v. These results were achieved with the same particle size and oxygen concentration as in the laboratory testing but with the roasting temperature of 500 ° to 525°C and a residence time of 30 min.

Jan 1, 2000

By Z. Kowalski

In the non-operational ?Górka? quarry, there are situated both a waste disposal site of an area of 6.7 ha, containing approximately 1 million ton wastes from high aluminium content materials (incl. about 400000 t of wastes from aluminum hydroxide production), and a pond of an area of roughly 3 ha, up to 15 m deep, with about 400000 m3 of polluted water and infiltrates from the disposal site mentioned. The basic problem related to the effluents in the Górka pond is both their high alkalinity (pH 12-13.4) and a variable analysis of pollutants whose level increases appreciably with the pond?s depth. The solution offered provides, first of all, remedial pumping and a treatment of effluents retained in the Górka reservoir. Effluents would be treated in a reverse osmosis plant according to a process verified so far on a quarter-commercial scale. The treatment process by-product, a brine solution (containing about 25% NaCl) whose amount may reach up to 100000 m3 might be supplied to the Debiensko Mine, which produces technological salt from salt-bearing mine waters. In parallel, an intake of underflows of infiltrates would be provided (previous geochemical identification) in order to take them away from the high aluminum site (by means of deep wells, and possibly girdling ditches). Such effluents would be subject to treatment. The successive stage is the utilization of approx. 50000 m3 of bottom slurry, left in the emptied reservoir, in the production of self-solidifying mixtures, which would be then used for sealing the bottom and the banks of the Górka reservoir. The empty and sealed reservoir would be filled up with a volume of approx. 600000 t of ashes, coming from coal burning in the thermal-electric power station. For the last stage, instead, is scheduled the rehabilitation of the entire waste disposal site in the Górka quarry. The site will be drained, covered with a leveling, sealing and rehabilitating layer, which will allow to introduce plants on the rehabilitated waste site. Later on, the area could be turned into a town park

Jan 1, 2006

By C. Anderson, B. Schug, C. Cristoffanini, S. Nazari

The Haile Gold Mine in South Carolina is increasing the automation level of their processing plant in order to improve operational stability. One step towards this goal is the application of a Digital Twin concept to provide Virtual Instruments. Haile has engaged ANDRITZ to implement Virtual Instruments at their grinding area hydrocyclones and at their tailing thickener underflow pump. These virtual instruments provide density values in a traditionally difficult location for reliable slurry density measurement. The Digital Twin is a first principles IDEAS1 ™ simulation model, connected in real time to the control system. Results have been promising, with the virtual instrument values matching the physical instrument under normal operating conditions, and showing better prediction under upset conditions. Haile plans to use the virtual instruments as optional process control parameters. INTRODUCTION OceanaGold’s Haile Gold Mine is located near Kershaw, South Carolina, about 50 miles southeast of Charlotte, North Carolina. This location was first mined in 1827, and has produced gold through several operating periods since then, including a heap leaching operation from 1985 through 1992. In October, 2015, OceanaGold acquired Romarco Minerals, the previous owner of the Haile Operation. The current operation began in 2017 as an open pit mine with additional underground resources. The nameplate throughput is 6,350 tpd ore, and 2017 production was 118k oz gold, with 140 to 155k oz gold expected in 2018. Proven and Probable reserves exceed 3 Moz. The process, as shown in Figure 1, includes a primary jaw crusher, comminution with a Semi-Autonomous Grinding (SAG) mill and ball mill circuit, flash flotation, rougher flotation, regrinding, pre-aeration, carbon in leach (CIL) leaching, carbon elution and regeneration, cyanide recovery, electrowinning and refining. The Haile Operation’s inaugural gold pour took place January 20, 2017. Mine life is expected through at least the year 2030. Based partially on prior experience of some key OceanaGold personnel with automation services from ANDRITZ on other projects, OceanaGold decided to include ANDRITZ on the Haile project. The scope of these services for Haile included design and supply of the process control application software, an ANDRITZ dynamic process simulator for operator training, and ANDRITZ Advanced Control Expert (ACE) ®2 systems for the SAG mill, ball mill, and rougher flotation areas. Since startup, ANDRITZ has continued to provide services for the site, particularly related to PLC and HMI equipment, programming and support, ACE system expansion, and the implementation of Virtual Instrumentation. The implementation of this new Virtual Instrumentation technology at Haile is consistent with Haile goals: increased automation, a change in the role of the operator from interactor to monitor, and improved stability by removing human error.

Jan 1, 2019

By P. W. Hynes

Tg Soda Ash has operated a shortwall mining system in the Green River, WY trona district since August 1982. The system has proven to be highly productive. In an effort to reduce the amount of relatively expensive development mining and improve mine planning flexibility, a method to mine the return air tailgate during the shortwall retreat was tested beginning in April 1987. As of June 1988, four shortwall panels had been completed using the advancing tailgate, producing more than 739 kt (815,000 st). This paper discusses the effects of the advancing tailgate on shortwall production, development mining requirements, costs, strata mechanics, and ventilation. Shortwall mining is a hybrid extraction method combining the self-advancing hydraulic roof supports from longwall mining and continuous mining machines (Fig. 1). The technique has been only marginally successful at the majority of the nearly 20 installations worldwide. At present, the face at Tg Soda Ash Inc. is the only shortwall operating in the United States and the only noncoal shortwall in existence. Despite the method's record of limited success, the staff at Tg Soda Ash determined that the conditions in its trona mine were well suited for shortwall mining. The commitment to install a shortwall was made in late 1981 and the first panel commenced in August 1982. Between that time and June 1988, about 3.33 Mt (3.67 million st) of trona have been mined with the system from 15 panels. Annual average productivities have ranged from 818 t/shift (902 st per shift) in 1982 to 1.4 kt/t shift (1591 st per shift) in 1987. Overall, the system has produced an average of 1.3 kt/ shift (1450 st per shift). In April 1987, a method of mining the return air tailgate during shortwall retreat was tested (Fig. 2). The objective was to determine if a return airway could be established and maintained by mining a series of rooms and pillars about 7.6 m (25 ft) past the face support line. The method would allow a barrier pillar to be left between shortwall panels without requiring the mining of a separate return air tailgate.

Jan 1, 1990

By B. Simser, T. Butler

Glencore’s Nickel Rim South Mine, located in Sudbury, Ontario, Canada, is a primary/secondary blasthole operation with ore zones lying between 1,100 and 1,700 m below surface. One of the main benefits of the primary/secondary mining method in high stress ground is that up to 50% of the mining will take place in secondary stopes that should be in a yielded rock mass state. Every future secondary mining stope begins as a primary stope abutment pillar. As with many mines, the stress loading history and rock mass conditions can vary considerably in space and time. Safe mining practices cannot allow for an assumption that the planned secondary stopes are indeed yielded. An incorrect assumption can result in mining development and stoping taking place in high stress ground rather than the expected yielded rock mass conditions. This can result in higher levels of seismicity than expected and incorrect ground support recommendations in areas where workers could be exposed. Seismic monitoring is the mines’ premier tool to track the actual rock mass response to mining. Yielded zones have a reasonably clear seismic signature/pattern over time that is visible in the collected data. The ability to accurately locate small magnitude seismic events can help define and delineate different stages of rock mass failure. The vast majority of the seismic data recorded by the microseismic monitoring system is below moment magnitude (Mw) 0.0. Examples are provided showing how small seismic events (Mw < -1.5) can help provide feedback from the rock mass deformation that allows the ground control engineer to gain a better understanding of how the rock mass is responding to mining processes.

Apr 26, 2022

By R. Freer

Recent developments in expanded PTFE membrane filter cloths offer high flow rates and sub-micron particle removal. These high strength, industrial grade filter cloths can be tailored for tubular filters, leaf filters and rotary vacuum drums. Filtration techniques using tubular filters make possible filtration of difficult slurries with the elimination/reduction of filter aids and chemical additives. This paper describes principles of surface filtration, applying the membrane filter cloth and comparisons to gravity separators. Benefits to the mining industry include clear effluent, enhanced solids recovery and accelerated cost payback.

Jan 1, 1996

Interstate 70 running into the mountains west of Denver, CO is the main access to the state?s numerous ski areas and other tourist attractions. As such, the highway is a vital part of Colorado?s economy. Due to the mountainous terrain in which it winds, I-70 is limited to two lanes in either direction. And, during the past few decades, the volume of traffic has increased to the point where motorists encounter major delays, particularly on Friday evenings and Saturday mornings heading west from Denver, and then again on Sunday evenings heading east. In the past, those delays occurred mostly during the ski season. However, many of the mountain towns have been successful in turning their resorts into year-round vacation destinations. A good move economically, but the pressure added to I-70 has caused even greater traffic delays, sometimes to the point where some Front Range residents avoid trips to the mountains.

Jan 1, 2013

By Jeramy B. Decker, Paul H. Madsen

"During the excavation of the north bound tunnel of the Devil’s Slide Tunnel project, deformation (convergence) was measured after passing through Fault Zone B. The tunnel convergence was not symmetrical, but was larger on the left side of the profile. It was determined that a shear zone nearly parallel with the tunnel drive was contributing to the uneven deformation. This paper will discuss how it was determined that the shear zone existed and how multi-point borehole Extensometers (MPBX) were used to verify that a significant amount of the deformation was occurring due to movement along the shear zone as the excavation was advanced. In addition, performance of the shotcrete liner in the area of the convergence will be examined. Finally, the paper will consider the means and methods that were utilized to ultimately control and stabilize the deformation. INTRODUCTION The Devil’s Slide Tunnel Project consisted of excavating two 1,250 meter tunnels each with a profile of 80 m2 utilizing the New Austrian Tunneling Method (NATM) or otherwise known as the Sequential Excavation Method (SEM). The tunnels are part of the California Coastal Highway south of Pacifica, CA, a suburb of San Francisco. The tunnels were opened to traffic in March of 2013. Geological Setting The tunnels run north-south through the San Pedro Mountain ridge, which is part of the Santa Cruz Mountains. The tunnel lies within the San Andreas Fault system and is 7.2 km west of the surface trace of the San Andreas Fault and 2.8 km east of the surface trace of the San Gregorio Fault. The 10 km strip between these two faults is referred to as the La Honda structural and terrain block (Decker et al. 2010; Amini et al. 2005; Earth Mechanics Inc. 2003). Locally, the tunnel passes through three blocks representing different geological conditions: South Block, Central Block, and North Block (Figure 1) (Decker et al. 2010; HNTB Corporation et al. 2005). The South Block consists of Mesozoic aged granodiorite and quartz diorite. The South Block also contains many local shear zones and a low angle thrust fault (Fault A). The South Block ends at Fault B, which is the southern border of the Central Block."

Jan 1, 2016

By William Gleason

The Dulles Corridor Metrorail Project is a $3-billion project that will link Dulles International Airport with the downtown center of Washington D.C. by way of a single seat train ride. The project is mostly above ground, but it does include two short, yet complex, tunnels through the area of Tyson?s Corner. The project is being completed in two phases. The Dulles Transit Partners (DTP), led by Bechtel, was awarded the first phase, a $1.6-bil-lion phase that includes 17 km (11 miles) of track with five stations. At Tyson?s Corner, the project includes twin 730-m- (2,400-ft-) long, 6-m- (20-ft-) diameter tunnels. Bechtel is self-performing construction for the $1.6-billion design-build job. Gall Zeidler Consultants was hired by DTP as designer for the NATM tunnel portion of Phase 1, and Beton-und-Monierbau was hired as tunnel subcontractor. Tyson?s Corner is an affluent and congested area that sits 152 m (500 ft) above sea level. To get through the area, it was decided that tunnels would be the best option with the least amount of disturbance to the surrounding areas. However, with extremely shallow groundcover above some points as well as soft soil throughout, the tunnels are also the most complex aspect of Phase 1. About 213 m (700 ft) was constructed utilizing the cut-and-cover method. The remaining 518 m (1,700 ft) is being constructed using the New Austrian Tunneling Method, which integrates the principles of the behavior of rock and soil masses under load, and monitoring the performance of underground construction during construction. ?The tunnel only falls 2 m (7 ft) from one end to the other and we pass through two soil conditions, they are both soft ground,? said Dominic Cerulli, tunnel task manager for Bechtel. ?Soft ground is very tricky because you have to close the ring in a timely manner to minimize settlements at the surface. If you don?t close the ring quickly to achieve a round structure that?s good in compression, the tunnel could start necking and squatting and the ground above it will settle. We are under major roadways, so excessive settlement would be a bad thing.?

Jan 1, 2011

By P. R. La Pointe, H. C. Ganow

The production of both over- and undersized coal fragments is a constant problem to open pit operators in the Powder River Basin. Operators strive to achieve production blasts that economically minimize the weight percentage of over- and undersize coal. However, natural fractures influence blast fragmentation, and can impose limits on the final fragment size distribution. ARCO&apos;s Anaconda Minerals Company studied the limits placed by natural fracturing as part of a wider geotechnical study of the Wyodak Coal in the eastern Powder River Basin, Campbell County, Wyoming. Measurements of fracture orientation, size and spacing were made at ARCO&apos;s Black Thunder Mine. These data were used to form statistical distributions for natural fracture size, spacing and orientation. An algorithm was created to select fracture properties at random from these distributions and to form hypothetical blocks. The blocks were then numerically "sieved" to derive pos- sible particle size distribution curves. These curves are compared to fragmentation results from samples taken from three test blasts. All test blasts yield very similar lognormal fragment size distributions. The median particle size varies from 1.25 to 2.0 in.(3.2 to 5.1 cm), the mean from 4.0 to 8.5 in. (10.2 to 21.6 cm). The standard deviation was about 1.6 in. (4.2 cm). Coal fines (fragments < 0.25 in. or 0.64 cm) are about 15%. Calculated fragment distributions for the natural fractures predict the median size well but underestimate the variance. Algorithm modifications to account for processes known to occur in the comminution zone near the blast hole significantly improve the match in the fine coal size range. The match suggests that spacing of fractures, rather than fracture length, controls the formation of fine- and medium-sized fragments. On the other hand, the oversize coal is controlled by the fracture lengths, rather than the spacing. Data from subsequent test blasts support this idea. By increasing delay times from 8 msec to 17 msec, engineers were able to reduce fines to 7% - 10% but could achieve no further improvement, despite changes in shot pattern geometry, decking and hole size. The hypothetical fragment distributions show that, even without blast enhancement, about 5% of the natural coal blocks are fine-sized.

Jan 1, 1986

By John Reilly

"INTRODUCTION Successful management of megaprojects, meaning delivery within budget, on time and according to expectations, is a fundamental requirement. Many projects have been successful, some have not. This paper reviews megaprojects1, drawn from the author’s projects over the last 50 years, with “lessons-learned” and a summary of recommendations that, if implemented, would improve megaproject management and delivery. Characteristics of these projects are summarized – including outcomes related to key factors such as politics, management, organizational structure, contracting methods, cost estimates, risk and other elements. The projects include the Washington D.C. Metro, Boston Southwest Corridor, LA Metro, Toronto Rapid Transit Expansion Program, BART San Francisco, MARTA Atlanta, London Underground and the Washington State Highway megaprojects – including the SR520 Floating Bridge and the Alaskan Way tunnel. Other projects that illustrate successful, innovative management and contracting methods include the Madrid Metro (low-cost delivery), the Sydney Northside Storage tunnel (outturn cost, alliancing) and the Lake Mead tunnel (working in partnership, risk management). KEY ISSUES A characteristic of megaprojects is that their complexity increases exponentially with size (Reilly 2010, Galloway et al. 2012). These projects are very visible politically, have many stakeholders who must be satisfied and generally span many years and political election cycles. To be successful they must meet expectations, function efficiently, and be delivered under, at or close to budget and schedule. There is a widely-based perception that large, complex projects are always delivered late, over budget and with problems. Specific examples include projects such as Tren Urbano in Puerto Rico – $1.28 billion over initial budget (+133%), the Silver Line Transitway Project in Boston – $286 million over budget (+90%), the London Jubilee Line Transit Project – 2 years late and £1.4 billion (+67%) over budget, the Channel Tunnel Rail Project – £3.7 billion (+80%) over budget, Denmark’s Great Belt Link rail and road link (54% over budget), the 2003 Woodrow Wilson bridge tender in Virginia (72% over estimate) and Boston’s Central Artery Project – several billion (perhaps 100%) over what would have been a realistic initial budget and years late (Reilly 2001c, 2004a; Salvucci 2003)."

Jan 1, 2016

By G. Hwang, S. Park, H. Kim, J. Choi, P. Seo

"In the mineral processing, clay minerals have negative effects on the flotation of valuable minerals. In this study, we investigated how the floatability of malachite (CuCO3·Cu(OH)2) is affected by presence of the clay minerals in the fundamental aspects. Flotation experiments were conducted by using Na2S and PAX (potassium amyl xanthate), and the floatability of malachite was compared between the cases in the presence and absence of clay minerals. The results showed that floatability was greater in the absence of clay minerals than in the presence of clay minerals and decreased with increasing weight percent of kaolinite under same conditions applied. In addition to examine how clay minerals affect malachite floatability, we conducted flotation experiment with changing clay adding order. The results indeed showed that malachite floatability was affected by clay adding sequence. INTRODUCTION The demand of copper is growing as industrial development increases, but mineral resources are limited. Therefore, studies for Cu oxide flotation are being conducted to improve their recovery(1-3). However the mining industry is well aware of the difficulty in treating copper ores in the presence of clay minerals(4). Clay minerals have unique properties and these properties may affect flotation. In the previous studies, the effect of slime coating of clay minerals on flotation was investigated(4-6). For example, Zhao and Peng (2014), Peng and Zhao (2015), and Arnold and Aplan (1986) found that clay slime coating on chalcopyrite, chalcocite and coal surfaces through the electrostatic attraction reduced surface hydrophobicity and then depressed the flotation. Other researchers have also reported clay minerals have impact on pulp rheology. Especially in the case of bentonite, pulp viscosity increased with increasing amount of bentonite and the higher pulp viscosity have deleterious effect on copper recovery(7, 8). However, these studies only focus on slime coatings and pulp rheological behavior. Forbes et al. attempted to decoupling rheology and slime coatings effect on flotation but this study has limitation that individual role of two clay species either attached to mineral or suspended in bulk solution was excluded(9). Hence, in this study, we aimed to investigating the effects of individual clay (suspended and attached) on malachite flotation."

Jan 1, 2016

By Enrique Jelvez, Nelson Morales Varela, Christian Ihle, Joaquin Silva

All mineral beneficiation processes require water for its execution. Therefore, the availability and adequate management of water are key to the existence of any mine operation. However, many mines’ operations are affected by water scarcity and risk an increase of operational costs or even production in some cases. This paper proposes a model to minimize the losses of water due to evaporation and re-absorption by adjusting the active and inactive periods of the discharge in different points of the tailing. When applied, the model determines optimal or nearly optimal discharge operation in all the scenarios that were evaluated.

Jun 25, 2023