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By Rafael C. Castro, Paul V. Savard, Kathleen M. Murtagh

Preliminary design is underway for the Massachusetts Water Resources Authority’s (MWRA) next major tunnel program, the Metropolitan Water Tunnel Program (MWTP). The MWTP is the latest part of MWRA’s ongoing efforts to achieve redundancy for its metropolitan water transmission system including its historic deep rock City Tunnel, City Tunnel Extension and Dorchester Tunnels. The MWTP comprises several deep rock tunnels that will be approximately 10-foot to 12-foot finished diameter totaling just over fourteen miles long and ten connections to existing large diameter surface piping and pumping stations. This paper will present an update on current engineering and permitting efforts, packaging schemes, and the schedule to complete the MWTP.

Jun 13, 2023

By Sam Lo Grasso, Carlos Herranz Calvo, Stuart Warren, Ted Giesing, Charles Marchesano

Mott MacDonald and Project Management Advisors are providing Technical and Project Management services for San Diego County for the Courthouse Commons Project. The Courthouse Commons Project involves the redevelopment of three downtown blocks owned by San Diego County and construction of an Inmate Transfer Tunnel between the County Central Jail and the San Diego Central Court. The tunnel will be 327 feet long, crosses the San Diego Fault and is being constructed using the Sequential Excavation Method (SEM). This paper discusses the history and procure‑ ment strategy for the project, the technical aspects of the transfer tunnel and the con‑ struction progress of the tunnel to date.

Jun 13, 2021

By Klaydison Silva, Pedro Silva, Letícia Damet

The current situation of the global mining economy is increasingly focused on the utilization of materials previously discarded in the mining process. The waste from the past, through new processing routes, is gaining new contours for use as high-value-added products. The strategic mine planning process has consequently had to adapt to the new economic reality. In standard scenarios, the focus was primarily on mine sequencing aimed at the highest economic return, with all infrastructure allocated as a necessity of mining. This work aims, in strategic planning, to configure and select the best composition of mining structures. The entire Mine-Plant-Waste-Tailings-Products chain will be considered as a factor in the sequencing of a multimine complex, to achieve the most sustainable utilization of the current mines’ waste. The sequencing is based on concurrent flows of process configurations and capacities, structure sharing, and flexibility of feed types. These factors will guide the sequencing, which will be constrained by components such as waste and tailings disposal rates, lithology feed relationships, and especially product composition through market specifications, all while respecting product shipping capacities.

Feb 22, 2026

By Yuemin Zhao, Daniel Tao, Rick Honaker, Maoming Fan

"Froth flotation is the most widely used method of separating fine coal, especially coal with coking properties. However, froth flotation is not efficient for treating ultrafine coal and coarse coal particles. Our previous fundamental test results demonstrated that cavitation-generated nanobubbles around 700 nm in diameter can significantly improve coal and phosphate flotation performance over a wide particle size range. In this study, the effect of nanobubbles on the flotation performance of different particle size fractions of coal was investigated using a bank of 10-L flotation cells, a specially designed 50-mm inside diameter column and a 152-mm inside diameter column. It was found that nanobubbles that were either directly formed on or subsequently attached to the surface of coal particles during the froth flotation process improved flotation efficiency. The use of nanobubbles in a bank of mechanical cells flotation and column flotation significantly increased the flotation recovery at a given product grade. Nanobubbles increased the flotation rate constants of different coal particle sizes. The presence of nanobubbles in flotation slurry could extend the lower and the upper particle size limits for effective coal flotation.IntroductionFor minus 0.6 mm fine coal or minus 0.15 mm ultrafine coal particles, froth flotation is known to be the most efficient and the most cost-effective separation technique. However, flotation efficiency decreases sharply with ultrafine and relatively coarse coal particles. Studies have shown that the low flotation efficiency of ultrafine particles is mainly due to the low probability of bubble-particle collision (Yoon et al., 1989; Ralston and Dukhin, 1999). Enhanced flotation of fine and ultrafine coal can be achieved by increasing collision and attachment probabilities.The top size of particles that can be recovered by flotation depends on the combination of mineral properties and flotation devices. Turbulence in flotation devices is an important factor that affects the stability of bubble-particle aggregates. Even in the flotation of fine particles, bubble-particle detachment can significantly influence the kinetics of flotation taking place in mechanical cells, which provide intensive turbulent agitation (Deglon et al., 1999). Coarse particle flotation is more difficult, because increased agitation is required to maintain particles in suspension and coarse particles are more likely to detach under turbulent conditions (Mankosa and Kohmuench, 2002; Soto and Barbery, 1991). More efficient attachment of particles and improved flotation rate has been observed when tiny bubbles coexist with conventional-sized flotation bubbles (Attalla et al., 2000; Tao et al., 2010; Fan et al., 2010a, b, c, d; Fan et al., 2012)."

Jan 1, 2015

By ERIK CHARRIER, HUGH MILLER, JOSEF BOURGEOIS

In this study, a unique excavation system was characterized, utilizing waterjet technology as the primary tool for material removal during rehabilitation of reinforced concrete and shotcrete structural liners. Through empiric testing, this research seeks to validate the hypothesis that waterjet removal of these support systems will result in less unintended damage than conventional removal methods. The intent is to develop a viable technology that will reduce the collateral damage caused to surrounding liners during excavation, improve the adhesion between shotcrete and the substrate for longer lasting ground support, and improve overall safety for workers in underground environments. An analysis on the fracture mechanisms and operating parameters of each method was completed. Instrumented shotcrete panels were physically tested and examined through visual inspection and ground penetrating radar (GPR) to compare substrate damage according to each testing method. After testing was completed, the data strongly indicates that waterjet cutting causes less collateral damage to the surrounding intact liner and substrate when compared to that of conventional impact hammers. This research is intended to provide a scientific basis for additional applied research in the rapid excavation and repair of shotcrete support systems.

Sep 23, 2021

By Sunny Schoone, Maximilian Getz, Felix Leaman, ELISABETH CLAUSEN

Jan 5, 2023

By Steve Karl

"The International Tunnelling and Underground Space Association (ITA) held its 42nd General Assembly along with the 2016 World Tunnel Congress (WTC) April 22-28 in San Francisco, CA. The event was co-organized by the Underground Construction Association of SME (UCA). This was the first time the event has been held in the United States in 20 years.As cities demonstrate strong needs in tunnels and underground spaces for public transportation, subway stations, hydroelectric infrastructures and other underground infrastructure needs, the WTC 2016 provided the 2,319 attendees from around the world a unique occasion to discover the latest state-of-the art innovations in urban planning and underground construction projects in the United States and worldwide.The Congress, held in lieu of the UCA’s North American Tunneling Conference, included an exhibit that attracted 226 exhibitors in 298 booths. The exhibit had on display the latest in technical equipment and services from some of the largest and best companies in the international tunneling industry. The exhibit hall was also the place where participants were able to interact with the authors of the 168 posters and receive answers to various topics directly concerning civil engineers: innovative procurement processes, cost and risk management, contractual methods, BIM technologies and examples of innovative underground infrastructures built worldwide. And the technical program included 353 technical presentations – 185 podium and 168 posters.What is ITA?ITA-AITES is a nonprofit, nongovernmental organization that promotes greater use of underground space as a key instrument in sustainable development. Established in 1974 and based in Lausanne, Switzerland, ITA-AITES is made up thousands of professionals involved in the tunnel and underground space industry, including engineers, project owners, town planners, architects, industrial designers, companies specialized in public works and major structures, suppliers of construction site facilities and equipment, lawyers, politicians, researchers and academics, economists, financial experts and other stakeholders.ITA-AITES consists of 73 member nations and 300 affiliated members, including 15 major sponsors and 60 donors. The association is run by an executive council made up of 15 members elected by the 73 member nations, each representing a different dimension of the tunnel community."

Jun 1, 2016

By I. H. Warren

The high temperature lubricant molybdenite, MoS2, is usually produced by a complex sequence of processes involving mineral dressing of molybdenite concentrates followed by leaching with hydrofluoric acid to remove abrasive impurities such as silica (1). Many attempts have been made, mostly by techniques involving, direct fusion of molybdenum compounds with sulphur, to produce synthetic molybdenite. However, apart from some experiments of geochemical interest (2) in which aqueous solutions of sodium sulphomolybdate, Nat MoS4, were decomposed under pressure at temperatures between 300°C and 700°C, no attempts to produce the mineral by hydrometallurgical procedures have been reported. Since molybdenite is nominally a compound of tetravalent molybdenum with sulphur, and the most common state of molybdenum is +6, production of molybdenite is likely to involve reduction and sulphidization. The present study, therefore, describes the reduction, with hydrogen and carbon monoxide, of molybdenum in the hexavalent state in alkaline aqueous solutions containing sulphide ion. In these

Jan 1, 1972

By Kenneth Deaton

"A packaged cooling system is being developed for refuge alternatives (RAs) that will meet U.S. Mine Safety and Health Administration (MSHA) qualification guidelines for deployment in coal mines. This system will allow full occupancy ratings of deployed refuge alternatives to be maintained by keeping the apparent temperature inside the RA from exceeding 35° C (95° F).Research investigations sponsored by the National Institute for Occupational Safety and Health (NIOSH) have shown that heat buildup caused by occupants in mobile RAs will result in apparent temperatures that exceed the 35° C (95°F) limit established in 30 CFR 7.504.Figure 1 shows the temperature rise in an inflatable RA having an occupancy rating of 23 people at an 27° C (81°F) mine air temperature. This plot shows the need for either heat mitigation or occupancy derating in warmer mines.The Refuge Alternative Environmental Control System (RAECS) will be designed to provide enough heat mitigation to eliminate occupancy derating due to heat buildup over the 96-hour refuge period.This article describes testing of a prototype cooling system that uses proven vapor compression technology powered by batteries to keep the RA interior below the 35° C (95° F) limit for a minimum of 96 hours. Testing of this prototype cooling system was conducted in December of 2015 and January of 2016 at the NIOSH test mine in Bruceton, PA. December testing was conducted at the prevailing mine ambient temperature — approximately 15.5° C (60° F). The January testing was done with the mine ambient temperature in the immediate vicinity of the RA artificially elevated to 29° C (85° F). Realistic heat gain from RA occupants was provided by human simulators developed by NIOSH. These simulators add sensible heat corresponding to human metabolic processes and latent heat generated by respiration and perspiration. Heat generated by CO2 scrubbers was also added. Results of cooling system performance using these simulated loads at the two ambient conditions are described. A comparison of the apparent temperature in the RA using two different control techniques is also presented. This work documents the ability of the cooling system to meet the established apparent temperature limit at the full occupancy rating of a six person RA. A new cooling system intended for use with existing RA deployments and having greater cooling capacity is currently in development and will be described.Expendable desiccant modules were also used to provide supplemental water vapor removal and their role in mitigating cooling load is addressed."

Dec 1, 2016

By Muhammad Azeem Raza, Samuel Frimpong

Underground mining environments are inherently hazardous and can lead to emergencies where effective rescue and self-escape become critical. Missouri University of Science and Technology is pioneering new technologies for effective self-escape. The rescuers and miners need to be trained in these new technologically driven environments. Previous research in fields like aviation, medical surgery, and oil and gas drilling has demonstrated the effectiveness of virtual simulation training, but the mining sector has yet to fully adopt advanced tools such as eye-tracking and immersive training modules. This research proposes a comprehensive training infrastructure incorporating these technologies to enhance situational awareness and decision-making during emergencies. The novelty lies in the application of advanced miner escape and communication technologies, specifically designed to monitor and enhance cognitive responses in high-stress situations. By leveraging these technologies, the proposed training infrastructure aims to prepare the next generation of underground miners and operators, by equipping them with the necessary skills to manage emergencies effectively.

Feb 1, 2025

By Stacey Leichliter

The Cripple Creek and Victor (CC&V) Gold Mine (Cresson Project) (Fig. 1) is undergoing an expansion to extend production to the year 2025. This expansion involves building a high-grade ore mill, another valley leach facility (VLF) for heap leach operations and expanding the overburden storage areas. The current operating pits are progressing downward from the oxide ore into a more sulfide and telluride-rich orebody. There is still oxide ore present in the current pits and planned pits not yet mined. There is an increased need for two recovery processes for these two different types of ore. The key component to this expansion is the high-grade ore mill, which has gravity, flotation and carbon-in-pulp (CIP) circuits. The mill will be the main recovery process for the higher grade, more sulfide/telluride-rich ore. This ore type does not recover well on the heap leach pad due to its refractory nature. Geometallurgy is vital for ore characterization for the two recovery methods. Geometallurgy helps develop indices that are used to predict parameters that influence overall recovery and production, such as hardness, crushability, grindability, pH fluctuations, gravity (coarse) gold, flotability and cyanidability. Using geology and mineralogy along with other analytical data, geometallurgical models are constructed and applied to the resource block model for proper planning and extraction of the gold. Geometallurgy aims to analyze the variability in the different responses to the parameters to help reduce risk (costs) and optimize recovery (profit).

Jan 1, 2013

By Evan J. Owen, Virginia T. McLemore

of high specific gravity, resistant minerals that form from mechanical concentration by waves, currents, and winds in marginal-marine environments. These sediments are enriched in critical minerals such as titanium, zirconium, and REE. Cretaceous beach-placer sandstones are found in the Colorado Plateau of northwestern New Mexico. Originally discovered by airborne radiometric surveys for uranium in the 1950s, these beach-placer sandstones are being re-examined with modern methods as potential sources for critical minerals. Selected beach-placer sandstones have been sampled, mapped with ground radiometric surveys, and analyzed with whole-rock and trace element geochemical methods. Mineralogy is being determined with optical methods, XRD, and EMPA. Zircon, rutile, ilmenite, and monazite are the primary heavy minerals of interest found in the studied deposits. Initial results show that the sandstones contain up to 1.4% total REE, 29.4% TiO2, and an estimated 4.9% ZrO2. Chondrite-normalized REE diagrams show distinct light REE and minor heavy REE enrichment, as well as pronounced negative Eu anomalies for each deposit.

Feb 1, 2024

By Haydn H. Murray

Although alumina constitutes about ii percent of the earth's crust, it is expensive to separate and purify for the production of aluminum with the exception off the alumina in bauxite. The United states has a variety of non-bauxite resources that could substitute for bauxite, including high alumina clays, alunite, dawsonite in oil shale, anorthosite, and nepheline syenite. Each of these resources are discussed from the standpoint of geology, geography, processing, potential recovery, and environmental problems. Potential by-products include silica from clays, potash and sulfuric acid from alunite, soda ash from dawsonite, and soda ash and potash from anorthosite and nepheline syenite.

Jan 1, 1982

By A. E. Michon

I am Alfred E. Michon, Vice President- International for Burlington Northern Inc. I work for BN's holding company and my responsibilities include co-ordinating the activities of our eight subsidiary companies as they relate to international commerce--an increasingly important aspect of the overall business of our company. Until last April, I was President of the Fort Worth and Denver and Colorado and Southern railroads, subsidiaries of BN. Prior to that, I headed the marketing and pricing area of BN's coal transportation business. Based on my experience in the energy industry, both domestic and international, I would like to discuss the world-wide trend towards the reliance on low-sulfur coal in lieu of natural gas and oil for the generation of electricity. Since pontification on the energy scene world- wide is best left to consultants with scenario-spitting computers, let me in- stead emphasize this trend through two examples. First I will describe the regulatory and economic factors which have encouraged the replacement of natural gas by low sulfur coal as a boiler fuel in the US. BN's investments in track and equipment were instrumental in this conversion. Secondly, I will show how this same combination of factors has created a large demand for steam coal in the Far East. Again, our company's strategy is to facilitate conversion to coal overseas through timely and sufficient investments.

Jan 1, 1982

By A. K. Smith

Overexposure to noise remains a widespread, serious health hazard in the U.S. mining industry. Most other categories of illnesses and injuries associated with mining have improved, with the exception of hearing loss. U.S. Mine Safety and Health Administration (MSHA) coal noise data from 2000-2004 show that the continuous mining machine (CMM) is first among all equipment, accounting for 35% of noise overexposures. Joy Mining Machinery, in collaboration with the National Institute for Occupational Safety and Health (NIOSH), is conducting research to reduce noise generated by continuous mining machines. This paper describes a "JOY Designed for Noise Reduction" (JOY DNR; patent pending) tail section as a noise control for reducing the noise overexposures of CMM operators. Underground testing shows a 45% to 65% noise exposure reduction for the operator when comparing the JOY DNR tail section results to those for a standard machine. Utilizing this newly developed noise control, along with previously proven controls, will provide CMM operators an opportunity to be within the MSHA permissible exposure limit (MSHA-PEL). Mining Engineering, 2011, Vol. 63, No. 7, pp. 83-85. Official publication of the Society for Mining, Metallurgy and Exploration, Inc.

Jan 1, 2011

By Michael G. Zabetakis

Effective accident prevention programs utilize a broad spectrum of activities, including meaningful training programs. In practice, such programs must be directed towards specific, defined needs. These needs are considered here for three categories of employees: new, re-assigned, and experienced.

Jan 1, 1983

By D. W. Gillmore

Numerous orphaned strip mines and old refuse piles scar the landscape, contributing to stream pollution and degradation of the natural environment. Field experiments to reclaim acidic surface-mined spoil and refuse banks with fly ash from bituminous coal-fired powerplants were conducted at several sites in West Virginia. Fly ash served as a neutralizing agent and soil amendment, permitting vegetation of waste lands and disposal of large quantities of ash. Reclamation of land by this method is estimated to cost about $300 per acre of leveled site, depending upon the topography of the land and quality and availability of the fly ash.

Jan 1, 1972

By Wiston Rocher

The Minera Ojos Del Salado (MINOSAL) concentrator is located 20 km (12 miles) southeast of Copiapo, Chile. It processes copper ore provided by its Santos and Resguardo mines at a capacity of 4.2 kt/d (4620 stpd). In 1982, Phelps Dodge acquired the majority interest in MINOSAL to explore the property's potential. At that time, the concentrator plant was a small, antiquated installation with a capacity of 674 t/d (740 stpd). At the time of the pur¬chase, the majority of the ore was produced from the Santos and Resguardo mines, but custom ores of copper, silver and gold were also treated. The acquisition occurred at a crucial time in the copper business, since the price had fallen to nearly 50 cents/ lb. In 1985, Phelps Dodge purchased the outstanding interest in MINOSAL and acquired 100% of the property. Today, after numerous improvements and two expansions, the concentrator is a combination of old and new equipment. The regrind mills, for example, have been in service for about 50 years, while the ceramic concentrate filter represents the latest technology.

Jan 1, 1993

By MATT RENAUD, Mustafa Kumral

Mining corporations have spread their operations worldwide in the last few decades. The reason behind widening operations geographically can be seen as it being part of a risk diversification strategy. Given that the technical, financial and social risks are high, favorable deposits, taxation regimes and legislative frameworks create incentives for international mining operations. On the other hand, international mining activities add the risks of permitting, investing, operating and decommissioning to the corporations. These risks could emerge from defaulting, corruption, resource nationalism, social license to operate, and political and legislative uncertainties and instabilities.

By S. K. Kawatra

The use of inferential particle sizing for a closed wet grinding circuit control has been practiced for several years. This paper presents a review of some inferential sizing equations developed for pilot and industrial plants using regression analysis. An analytical development is then presented showing how the general inferential sizing model arises from the nature of the classifier model. The relation between the general sizing model and the individual equations is then discussed.

Jan 1, 1982