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By R. Aliberti, E. Comis, M. Wone

DC Water’s Clean Rivers (DCCR) program involves the construction of approximately 29 km (18 mi) of CSO tunnels in Potomac Group soils in the Washington DC area. Soils include an upper predominantly over-consolidated fine grained plastic material facies (P/A) and lower predominantly coarsegrained facies (PTX). As earth pressure balance (EPB) tunnel boring machines (TBMs) are mainly used in such soils, the correct approach to soil conditioning can make a considerable difference in TBM performance. Soil conditioning laboratory tests are often completed during the planning phase prior to TBM excavation to develop a baseline for soil conditioning, reduce risks, minimize costs, and improve performance. However, only a few basic tests are standardized to date, and conditioning regimes are fine-tuned during the mining phase. The paper illustrates the effort carried out to identify the correct soil conditioning regime for both PA and PTX facies to improve TBM overall performance and reduce ground movement during the excavation of the Northeast Boundary Tunnel (NEBT) in Washington DC.

Dec 1, 2022

By N. A. Abdel-Khalek

An experimental study was carried out to compare the results of laboratory column flotation versus conventional flotation for the cleaning of fine coals of different rank and their oxidized samples as well as discrete size fractions. Surface oxidation caused a significant reduction in the flotation yields achieved with both methods. However, the column flotation produced concentrates? of lower ash content. The recovery -size curve achieved with column was similar in shape to that obtained with conventional cell, with superior results in the region of fine fractions. The influence of some column operating parameters was also discussed.

Jan 1, 1990

By J. Armstrong, J. Bourgeois, S. Warren

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

Mar 2, 2022

By T. Foster

The continuous operation of decanters in the mining industry relies heavily on the use of synthetic flocculants. Today, as plants seek to lower production costs by increasing throughput it is necessary to obtain optimum performance from the flocculant. Factors affecting such optimization include charge and molecular weight selection, and efficiency of mixing the highly viscous polymer solution with the feed slurry. Beyond maximizing dilution of the solution, the last factor is often ignored. This paper describes a series of calculations, based on fundamental transport theories, that have been used to describe flow conditions within decanter feed wells and to help select flocculant addition points. Examples are shown for the case of hydroxamated polyacrylamide flocculants in the Bayer Process, where proper selection of the addition points can result in lower flocculant dosage and better control of the decanters.

Jan 1, 1996

By D. Castillo

The effectiveness of a flotation column is due principally to the addition of wash water to the froth phase. The wash water flow rate can be significant, especially so for systems yielding a high weight recovery of fine solids, e.g. zinc sulfide flotation. Therefore, it is critical to recognize and assess the impact of the water addition upon upstream separation stages. This paper examines column flotation circuit configurations using data from a portable 2 t/day pilot plant. The objective is to provide an improved basis for column design, either as a retrofit or as part of a new circuit.

Jan 1, 1990

By Theodore Feldsher, Seung Han Kim, Mourad Attalla, John Roadifer, Chu-Chieh Jay Lin

Lifelines in seismic regions of the world seldom can escape crossing active faults. Cities in California have been mitigating this risk by constructing improved fault crossings. This paper discusses the analyses and design of the lining for a tunnel carrying a water conveyance pipeline through a fault that can potentially displace during a major earthquake event. The paper presents expected fault displacement, fault width and orientation respective to the tunnel, characterization of the ground surrounding the tunnel and its interaction with the lining, and performance required of the lining. Several other fault crossings will also be presented and discussed

Dec 1, 2022

By G. H. Harris

The flotation behavior of two high sulfur coals using a non-ionic surfactant as collector from two series of compounds containing oxygenated functional groups was studied in detail using a 2-liter Denver flotation cell. The performance of these reagents was compared with that of an oily collector, namely dodecane. The results showed that at the same coal recovery, a much lower dosage of these non-ionic surfactants was required as compared with that of dodecane. More import was the performance of these compounds as promoters for oxidized as well as un oxidized coal. Mechanisms of interaction of these compounds with the coal are suggested.

Jan 1, 1993

By R. R. Dorfler

The existing regrind circuit at the Climax Operations uses sodium cyanide and Nokes reagent to reject pyrite, copper, and lead minerals. Laboratory flotation studies were performed using feed to flotation following first-stage regrinding. The effects of conditioning time, pH, and the concentration of depressants such as Nokes reagent and sodium cyanide on the rejection of pyrite, lead, and copper minerals were investigated. The metallurgical results indicate that, in the presence of depressants, the rejection of copper is strongly dependent on the pH. Preliminary mill testing confirmed the finding. The rejection of impurities is also dependent on conditioning time. The recovery of molybdenite is independent of the variables investigated.

Jan 1, 1981

Laboratory tests were conducted to evaluate the silica collection efficiency of flooded-bed scrubbers with six different filter panel designs and at two operating velocities. Test results indicated that reductions in filter density negatively impacted respirable dust collection. Silica collection efficiency for the least dense filter was as much as 33 % lower than the collection efficiency of the densest filter. At the low operating velocity, the least dense filter allowed over 40% of the respirable silica dust in the scrubber intake air to pass through the unit, where it would be discharged back into the mine environment. Operation of the scrubber at the higher test air velocity increased silica collection efficiency, regardless of the filter panel tested. The density of the filter panels also impacted the quantity of air that is moved through the scrubber, with higher density filters reducing scrubber airflow. For each filter, the relationship between dust collection efficiency and air moving capacity must be considered to determine overall effectiveness for specific mine applications.

Jan 1, 1998

By Robin G. Burn

An orebody is a mining company's greatest asset; without it there can be no mine. Yet, by the very nature of the industry, orebodies are wasting assets whose progressive depletion must be balanced by continued discovery of new ore to enable both the industry to survive and the raw material demands of society to be satisfied. Although mineral exploration may be viewed as any activity which leads to the creation of investment opportunities in the mineral industry, ultimately new ore can only be generated through discovery. The process leading to discovery may involve a long chain of independent and interdependent events. It will almost always be repetitious and require the examination of many prospects or trials before the goal, a commercially successful discovery, is satisfied. Long term survival of a mining company through regular discovery of new ore, requires a continued commitment of funds and effort to mineral exploration.

Jan 1, 1984

By B. E. Davis

A technique was devised by the Bureau of Nines to recover coarse (plus 1.7 m) North Carolina phosphate now discarded as waste. Concentration utilizes the difference in particle sphericity between the relatively flat calcite and the rounded phosphate pebbles. Sizing, treatment in a continuous hydraulic classification system, and grinding upgraded a 17.0-pct-P205 reject to 24.5 pct P205 with a phosphate recovery of 63 pct.

Jan 1, 1985

By Raymond E. Zimmerman

The cleaning of coal by the use of jigs is one of the oldest methods of separating coal from its impurities. Although in many situations jigs have been replaced by other methods, by far the largest percentage of coal today is still being cleaned by some form of jigs. Some piston- or plunger-type jigs are still in use throughout the world; however, the greater number are air pulsated, generally called the Baum jig, named after the original inventor, Fritz Baum of Germany. This standard jig, with slight modifications, has been in use for over 75 years. Up until recently, however, it has had certain limitations in obtaining the high performance and efficiencies required in modern coal preparation practice. TO improve its performance, some radical modifications have been made in its design and operation SO that there is now a Baum-type jig giving much higher performance in terms of capacity, efficiency and sharpness of separation- This new jig is called the Batac, and the purpose of this paper is to describe its characteristics and present data giving its performance in treating coarse and fine sizes of coal.

Jan 1, 1974

By Dirk van Zyl

Pad construction costs can impact the overall economics of heap leach projects. Pad construction costs for single-and double-lined pads, using various designs, are listed for a typical small and large project. Double-lined pads are now more often required by regulatory agencies. Unless such designs reduce the risk of site specific contamination significantly, the extra costs cannot be justified from an economical viewpoint. Specific attention is given to the short project life (typically five years) of heap leach projects. A few numerical examples are presented to demonstrate the overall economic impacts of these costs on economic parameters.

Jan 1, 1990

By K. P. Stricker, H. Keddeinis, K. Grebe

Recent investigations by Mannesmann Research have shown that disintegration of sinter with widely varying quality levels is subject to a much more complex set of influences than was previously assumed. It was confirmed that disintegration at temperatures between 300° and 600°C (570° and 1,110°F) is triggered by the degradation of hematite. The specific tendency of hematite to disintegrate is, however, not constant: sinters containing the same amount of hematite can show widely differing disintegration tendencies, depending on structural homogeneity, porosity, and gangue quantity. Sinters with heterogeneous structures transmit stress to the hematite phase and this favors disintegration. Another factor is the brittleness of the glassy silicate phase, which can be influenced even by small modifications of minor gangue constituents.

Jan 2, 1984

By G. A. Kordosky

LIX® 34 liquid ion exchange reagent, one of a totally new class of metal extractants, is discussed in terms of its properties. Specifically, these properties include improved selectivity for copper and greater recovery. Some comparisons to the well known General Mills' LIX® 64N have been made. Particular emphasis is given to treating solutions containing very low copper values and high impurity levels.

Jan 1, 1976

By V. Gangrade, J. Addis, S. Vanderslice

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are conducting research to improve the ventilation of large-opening underground stone mines. The mine ventilation in these mines are characterized by: (1) challenges related to keeping airflow velocities high enough to effectively remove or dilute airborne contaminants, (2) low pressure losses needed to move large air volumes of air, and (3) costly stoppings needed to direct ventilation airflows. Each of two field studies was dedicated to specific focus areas. The first focus area was the characterization of underground mine ventilation airflow. The primary means of airflow control in stone mines is through the use of freestanding booster fans. The primary goal of this study was to identify the effectiveness of various fan types and optimize their placement. Both traverse and grid-based airflow readings were taken at various distances from the fans, ranging from 70 ft to 425 ft away from the fan. The air readings were taken using a vane-anemometer and a handheld hotwire anemometer. The data was used to develop precise computational fluid dynamics models. The second focus area was to determine diesel particulate matter (DPM) concentrations in the mine. For large-opening underground stone mines, controlling DPM exposures dictates the design of the ventilation system. Therefore, researchers carried out the DPM sampling campaign to identify potential areas of concern within the mine. The samples collected during the campaign were analyzed using NIOSH Method 5040. The sampling was done using the Mine Safety and Health Administration’s (MSHA) compliance sampling methodology.

Feb 1, 2023

By Sterling S. Cook

The U.S. Bureau of Mines is conducting core leaching experiments with sulfuric acid on oxide copper ores from the Cyprus Casa Grande and ASARCO Santa Cruz deposits in Arizona to further our understanding of the leaching process in supergene copper ores as it relates to in situ mining. Leach solutions from atacamite mineralization contained 5 to 30 g/l copper and few extraneous ions. Leachant from chrysocolla ores, with grades similar to the atacamite, contained 2 to 9 g/l copper and abundant extraneous ions. Quartz and K-feldspar had no impact on leach solution composition at any acid concentration (up to 40 g/l) while illite and sericite had minimal impact. Biotite, calcium-rich clay and limonite have a significant impact on solution chemistry when there is abundant free acid in solution. High acid concentrations increase acid consumption in ores with abundant biotite and limonite gangue. High acid concentrations can be used in ores with quartz, K-feldspar, and sericite gangues without increasing acid consumption per unit of copper removed.

Jan 1, 1988

By A. Ramage

Since late 2010, CH2M HILL has been working with a confidential client who holds a long-term commitment to sustainable development (SD). The commitment is aligned with all three elements of the triple bottom line: people and society, ecosystems and environment, and financial and economic systems. These commitments are carried forward by the firm?s executives, managers, and operational sites, and are evident in materials posted on the company?s public website. These materials include a formal sustainability report prepared in accordance with the Global Reporting Initiative (GRI) guidelines (GRI, 2006), a report that outlines key SD challenges and progress toward the GRI targets, and a delineation of risks and opportunities outlined in the firm?s Form 10-K and Annual Report. In keeping with its commitments to SD targets, our client wished to consider SD issues in its decision processes for facility expansion or new projects. The company engaged CH2M HILL to meet this goal, based on working relationships established through existing contracts and CH2M HILL?s leading capabilities in sustainable solutions.

Jan 1, 2012

By J. E. Urosek

In October, 1990, a fire started in a large underground coal mine in Western Pennsylvania. During fire-fighting activities, an explosion occurred and all personnel were evacuated. Safe re-entry into the mine was not possible and the mine was sealed. Recovery efforts began in January, 1991 and continued until March, 1991, when permanent underground seals were installed between the fire area and the mine openings. This paper describes an extensive atmospheric monitoring program conducted by the Mine Safety and Health Administration (MSHA), Pittsburgh Safety and Health Technology Center (PS&HTC) including the analysis of mine fire gases, natural ventilation, fan pressure and air quantity distribution.

Jan 1, 1993

By G. A. Gruber

A flotation process has been developed to successfully treat ore from the Santo Domingo phosphate deposit in Baja California Sur. The ore contained less than four percent P205 with quartz, silicates, and carbonates as gangue minerals. Flotation of the low grade feed In sea water required that the conventioinal Crago Process, comprising direct anionic flotation, deolling, and inverse cationic flotation be augmented by an anionic cleaner flotation step, phosphate depression, and a calcite flotation step.

Jan 1, 1986