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By Richard Chojnacki

The western united States is not usually noted for the production of fluorspar; however, many significant fluorspar districts do occur in the Rocky Mountain region and constitute a resource of sizable dimension and major potential. This is particularly true within the area of the West served by the rail lines of the Union Pacific Railroad (see Figure 1). Fluorspar deposits near the Union Pacific have produced over 1.3 million tons of finished fluorspar products from 2.3 million tons of ore. Approximately 80% of this production was of acid-grade and 20% of metallurgical-grade fluorspar. Production of ceramic-grade was negligible. Through the years substantial production has come from eight mining districts. Five of these have produced metallurgical-grade and three acid-grade. The best-known fluorspar producing area in the West is the Jamestown Mining District. It was one of the first producers of fluorspar in the western United States and is estimated to have produced over 500,000 tons of finished fluorspar from over a million tons of ore. The district encompasses approximately 36 square miles in central Boulder County, Colorado, about 9 miles northwest of the City of Boulder. Although small shipments were made from the district as early as 1873 or 1874, significant sustained production was not achieved until 1940 when the General Chemical Company, now a division of the Allied Chemical company, acquired the Alice, Burlington, Chancellor,

Jan 1, 1971

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, the National Institute for Occupational Safety and Health (NIOSH) conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the re-search, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This paper highlights NIOSH?s research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan and if appropriate training is provided.

Jan 1, 2009

By Verya Nasri

This paper will present the design and construction of a deep underground station of the Réseau Express Métropolitain (REM) project; the Édouard Montpetit station. The Édouard-Monpetit station is an interchange station that will connect the deeply sitting REM tracks to the existing metro station of the same name located closer to the surface. Édouard-Montpetit station is expected to be the deepest in North America, surpassing the famous Forest Glen Station. The various challenges and solutions put forth for the successful completion of this underground work are presented to serve as a valuable example for future deep excavation performed in urban area, in the close vicinity of highly sensitive structures.

Jun 13, 2021

By J. R. Dyni

The lacustrine Green River Formation of Eocene age in the Green River Basin, southwest Wyoming, contains the world's large resource of natural sodium carbonate in bedded trona (Na2CO3? NaHCO3? 2H2O). In this study, 126 billion tons are estimated to be present in 22 beds, ranging from 4 to 36 feet in thickness. These 22 beds underlie areas of about 50 to more than 775 square miles at depths ranging from about 650 to more than 3,000 feet below the surface. The total resource of trona ore in the basin for which drilling information is available is estimated to be about 149 billion short tons. The undeveloped deeper trona beds in the southern part of the basin may be exploitable by solution mining. Additional unevaluated sodium carbonate resources are present in disseminated shortite in strata interbedded with the trona and in shallow sodium carbonate brines in the northeast part of the basin.

Jan 1, 1995

By A. A. Zatout, G. H. Sedahmed, T. M. Zewail, M. H. Abdel-Aziz, B. S. Ibrahim, E-S. Z. El-Ashtoukhy

In this work, the possibility of intensifying the cementation process in stirred vessels was studied by using the perforated baffles as turbulence promoters; the cementation reaction of Cu+2 on Zn was selected as a model. Zn was used in the form of a sheet lining the inner wall of an agitated vessel. Parameters considered are initial concentration of Cu+2, solution temperature, impeller rotation speed, and impeller geometry. Within the present range of parameters studied, the rate of cementation was found to increase with increasing initial concentration of Cu+2, solution temperature, and impeller rotation speed. At the same rotational speed, a flat turbine gave a higher rate of cementation than a 45° pitched turbine. The present suggested that baffles’ geometry gave superior performance in terms of mass transfer of copper cementation compared to the conventional baffle geometry. All parameters that affect the rate of cementation were correlated in the form of dimensionless equations suitable for the design and performance prediction of the agitated vessel. Potential applications of the obtained results in the field of hydrometallurgical processes and wastewater treatment were discussed.

Jan 12, 2021

By Terry McNulty

DOUG HALBE: I've decided that we're going to change tactics here and we're going to be nice to people from now on. [Co-chair makes gesture of intense disbelief; laughter] I've also decided who's not going to be a co-chair next year. [laughter] We thought we'd get a couple of experts for our next presentation: some people with a lot of experience. We've asked them to tell us some of the things that all of you operators out there might be able to apply immediately to your plant. Our next two speakers have a tremendous amount of experience, and I think you'll find what they're going to say is highly pertinent to most plants. I looked through their paper and found some things that I could have used in the plants I operated in the past. Our first speaker is Terry McNulty. A lot of you know Terry. He was with Anaconda for a number of years as director of research. He then was president of Hazen Research. I'm going to continue with our new custom of saying nice things. Terry is the guy that I call when I don't know something, and he's always got the answer. SPEAKER: Who do you work for, Doug? [laughter] DOUG HALBE: Remember that we're being nice to people here, Joe. I know that's a stretch. [laughter] TERRY McNULTY: Thank you, Doug. I'm a little bit mystified by this sudden switch of tactics just before I get to the podium. Doug's been a good friend for a lot of years so I guess I do have to be nice. I won't say anything deprecatory about him, but I would have to comment that the observations made by earlier speakers have been far too generous. [laughter] During nine years of consulting as a mineral processor and extractive metallurgist, I have often conducted audits of the performance of client's plants. Usually these audits have been ordered by the plant management in hopes of identifying opportunities for improving processing efficiency or reducing costs. Some of the audits, however, have been financed by the Electric Power Research Institute (EPFU) and member utilities with the objective of

Jan 1, 1998

By M. du Plessis, J. P. Gouvea

Mesh based areal support is commonly applied in South-African deep-level gold mines. It forms part of an integrated support system that can cater for both rockfall and rockburst incidents. The application has been successfully applied over many years. Operations have different geotechnical conditions and practical considerations, which has led to the development of various types of mesh and integrated mesh-based support systems (i.e. meshing and lacing versus welded or chain-link mesh sheets). Typically rolls or sheets of mesh is pinned with rockbolts to the surface of an exposed excavation. Applications vary from hangingwall coverage in a conventional stope gully to complete excavation coverage in footwall drives of conventional mines or on-reef drives in massive mechanised mines. It is however critical to understand the behaviour of the rockmass and apply suitable support systems.

Apr 26, 2022

By G. Mei

"This study explores froth flotation and selective flocculation methods to recycle waste phosphors containing several rare earth elements, namely, yttrium (Y), europium (Eu), cerium (Ce) and terbium (Tb). The effects of the presence or absence of collector and of flocculant and their dosages, as well as the pH, were investigated. Reverse flotation resulted in concentrates with grade of 27.03 percent and recovery rate of 71.36 percent, while flocculation resulted in concentrates with grade of 31.43 percent and recovery rate of 91.28 percent. The flotation and flocculation behaviors were further analyzed by X-ray diffraction analysis, zeta potential measurements, particle size distribution and other methods. The successful separation of rare earth minerals by flotation was attributed to the selective adsorption of the collector onto quartz, making it particularly recoverable by reverse flotation so as to be separated from the valuable materials. The analysis of the particle aggregation process indicated that its better flocculation performance was due to the selective adsorption of flocculants onto the unwanted materials, enlarging the flocculant sizes by forming aggregations and facilitating the separation of rare earth minerals from waste materials based on different settling rates. IntroductionBecause waste phosphors pose the problems of heavy environmental burden and high risk to human health (Hu and Cheng, 2012) as a result of containing heavy metals such as mercury and manganese (He et al., 2006; Lucas and Emery, 2006), they have received added attention as urban mining resources for extracting rare earth elements (REEs) like yttrium (Y), europium (Eu), cerium (Ce) and terbium (Tb).At present, chemical processes such as acid leaching, alkali fusion, roasting and extraction are the primary methods for recovering REEs from waste phosphors (De Michelis et al., 2011; Li et al., 2012; Li, 2010). With these strategies, phosphors can be effectively decomposed and their REEs extracted. After the removal of impurities, the REEs can be efficiently precipitated by adding an H2C2O4 solution (Porob et al., 2012). Although relatively high recovery rates are achieved, those processes entail high energy consumption and can cause severe environmental pollution."

Jan 1, 2017

By B. A. Carbon

Western Australia is the largest state in Australia with an area one and three quarter times the size of Texas. Most of the State is desert or semi-desert, and only the southwest corner is heavily populated. The State has a population of one and a half million people, and one million of these live in and around the city of Perth. Perth is located on the narrow Swan Coastal Plain and is flanked by the Indian Ocean and the Darling Plateau. The Darling Plateau is an ancient peneplain rising some 300 metres above sea level, and forms an important resource base for the population.

Jan 1, 1984

By D. J. Bryden, J. W. Oberholzer

In response to the need for enhanced precautionary measures to safeguard mine workers in collieries from the consequences of methane ignitions in a heading, the coal mining industry has ex- pressed the desire for the development and testing of active on board suppression systems. As overseas systems cannot be used directly in the bord and pillar geometry it is necessary to adapt overseas and local technology to suit local mining conditions, as well as to test such developed systems for their compliance with the expressed needs. As the systems have to be tested in a specific roadway configuration, a facility was developed to enable the testing in South Africa. A surface test facility has been established which can be used to develop and test suppression systems on continuous miners and roadheaders. This facility consists of a tunnel wherein compliance tests can be conducted in simulated underground conditions. A number of methane explosion tests have been conducted in the test facility. The explosions conducted varied in CH,/air concentration (7,5 to 9 percent) and volume (26 to 88 m3). At lower concentrations there was a marked reduction in explosion strength and flame speed. Tests carried out with the Explostop system successfully suppressed the propagation of methane ignitions in both scenarios tested.

Jan 1, 1997

By J. David Gunn, Richard W. Lawrence

Gold and silver often occur finely disseminated in sulphide minerals such as pyrite. The use of biological leaching to dissolve pyrite and liberate gold has been extensively studied for a concentrate from the Porgera deposit, Papua New Guinea. The successful operation of a continuous bioleach circuit has been demonstrated. Bioleach residues were cyanide leached to extract gold and silver, and unreacted pyrite recovered for recycle to the bioleach. A 26 day steady state continuous bioleach test on a concentrate assaying 14.3 g/tonne Au and 87.0 g/tonne Ag produced residues with an average 73.5% weight loss and a pyrite oxidation of 88%. Cyanidation and recovery of pyrite from the cyanide residues for recycle gave overall recoveries of 92.1% gold and 74.6% silver. A proportion of the remaining precious metals was found in the bioleach solutions and may be recoverable. Losses to tails were 3.0% gold and 8.1% silver. Final tails represented 14.3% of the feed weight and averaged 1.84 g/tonne Au. A description of the continuous bioleach circuit and bioleach residue handling procedures, and the results of the study are presented. The features and advantages of biological oxidation as a pretreatment for refractory precious metal ores and concentrates are discussed.

Jan 1, 1985

By L. H. Michaud

A mining company plans to extend its surface coal-mining operations in central Pennsylvania. Although the proposed site contains pyritic material, the results of the acid-base accountings for the site shows an overall Neutralization Potential to Maximum Potential Acidity Ratio (NP:MPA) of 4.26:1 for the entire site. The pyritic material is, however, associated with the lower of the three seams to be mined. If traditional dragline-mining methods are used, this would result in the acidic material being placed at the top of the spoil piles, exposing it to air and water, and therefore to the formation of acid mine drainage (AMD). Further concerns are associated with the fact that the alkaline material is not distributed evenly over the mine site. To prevent the formation of AMD, the company has proposed to mine the area using truck-shovel mining methods. This technique offers a more flexible alternative for cut sequencing and for the selective placement of waste material. Working with the Department of Mineral Engineering at The Pennsylvania State University, amine plan was developed for this site. This plan results in the layering of the alkaline and acidic spoil to achieve an overall net alkalinity in all spoil areas. Therefore, mining this site should not result in the formation of AMD.

Jan 1, 1996

By Walter Steiner, Claus Becker

INTRODUCTION General Switzerland is a densely populated country in the heart of Europe. With its total surface of 41.300 km2 and a population of 6,8 million in 1986 the average population density is 163 capita / km2. The population density is lower than in Germany (245 capita/ km2) or the Netherlands (355 capita/km2). The USA have a population density of 26 capita/ km 2. However, sixty percent of the Swiss surface is covered by the Alps and another ten percent by the Jura mountains the remaining thirty percent of the surface is covered by the Swiss plateau where the majority of the population lives. The population in the inhabitated areas is thus substantially higher and may possibly reach those in major metropolitain areas. Due to the high population density in Europe in general and Switzerland in particular future traffic demands cannot be fulfilled sole by car or plane. Environmental and land-use constraints lead to the third option for growing transportation needs: High-speed rail (Bovy, 1990). Switzerland has developed its own approach to promote public transportation and in particular rail transportation: "Rail 2000" (Stalder, 1990). The system "Rail 2000" is based on a series of hubs distributed over Switzerland where easy connections can be made.

Jan 1, 1991

By Robert E. Gray

The vat leaching operation at the Yerington Mine was started in October, 1953. The original plant facilities consisted of primary and secondary crushing, eight leaching vats, precipitation launders, sulfuric acid plant and the necessary maintenance, warehouse and administrative facilities. By 1961, 35,000,000 tons of oxide ore had been removed from the mine exposing the underlying sulfide ore body. A 5,000 ton per day concentrator was constructed and put into operation to treat the sulfide ore in November, 1961. The original crushing plants were used for both oxide and sulfide ores. By adding a third crushing shift for six days per week, the treated ore was increased from 12,000 to 17,000 tons per day. To balance the oxide and sulfide ore reserves, the concentrator was expanded to 13,500 tons per day in 1967. Again, no additional crushing facilities were added. It was anticipated that the treatment rate of oxide ore would be reduced from 12,000 to 9,000 tons per day. Instead, the addition of two crushing shifts per week, and improved operating procedures, increased the treated ore to 26,500 tons per day, 13,000 tons to the vat leaching and 13,500 tons to the concentrator.

Jan 1, 1975

"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 Arvid E. Anderson

The paper describes the unique operating features of the Lebanon Concentrator Plant wherein both magnetic concentration and froth flotation are used. Chalcopyrite is selectively floated by the use of dual collectors, Aerofloats and secondary butyl xanthate. Both potassium ethyl xanthate and sodium isopropyl xanthate (dual collectors) are dissolved and emulsified with pine oil for the flotation of the pyrite. Sketches describing the plant operations are presented and plant operating metallurgical results obtained are also given. The optimum production of minerals by the froth flotation process is normally achieved [ ] smooth operating conditions, The process, because of its many variables, becomes an art as well as a science. Therefore, any phase of the operation which will aid the operator in his control of the numerous variables will help produce a smoother operating plant, One of the most important variables which the operator deals with is the addition of reagents, These are usually costly items and should be used discretely with minimum amount of waste, The danger is that ,this emphasis may reduce the reagent amount to a point below that required, or, on the other hand an excessive amount is added, Both conditions usually yield poor results. The drea of the metallurgist is to provide the operator with the tools enabling him to produce a good mineralized froth at all times. Normally the operator has no control concerning the type of reagents which he must use. This has usually been worked out for him in the laboratory and by plant-scale tests. He does have limited authority to control the amounts of the reagents at his disposal. This, I believe, is as it should be. However, the operator should be provided with the best combination of reagents for his particular job. The providing of this combination of reagents for his particular job, The providing of this combination is often difficult, yet it is very important in order to yield good results, With this in mind, the dual collector idea was introduced for the selective flotation of chalcopyrite, and also later for the flotation of pyrite at the Concentrator Plant of the Bethlehem Cornwall Corporation in Lebanon, Pennsylvania, Supplying several types of collectors has given the operator an additional effective tool, even though great variations are encountered in ore tonnage treated and in ore composition, This paper deals with the use of the dual collectors and with the addition of the reagents in the form of a pine oil emulsion, or more accurately, a pine oil suspension. It is hoped that other operators may find the ideas helpful. There does not seem, to me, to be definite scientific fact which would substantiate the necessity for the use of dual collectors. However, in actual operations, the metallurgical results at Lebanon became more uniform with the use of dual collectors, I look upon it as an "insurance policy" which greatly aids the operator during those periods when he is having trouble, One theory has been advanced, i.e. one collector has a greater tendency to float the coarser minerals, whereas the other one may float the finer ones. Consequently, a combination of the two collectors will result in optimum recoveries, There has been some evidence that this is true, but it is not conclusive, on the other hand, the use of a xanthate-pine oil suspension (or emulsion) should speed up the surface reaction of the collector with the sulfide minerals, result¬ing in more uniform flotation, This has definitely happened in our particular case. A more interesting unexplainable observation has also occurred; i.e., the xanthate solution does not appear to lose its strength as rapidly when it is in the form of an emulsion (or suspension), This was first observed when a 50 gallon drum of a 20% ethyl xanthate solution was taken to Wilmington, Delaware, for a laboratory test, using a homogenizer to produce the xanthate-pine oil emulsion. Upon arrival, the drum of xanthate had developed a considerable internal pressure, The relief of this pressure was accompanied by a strong odor, When the emulsion was returned to Lebanon for the plant test orders were issued to release the pressure prior to emptying the emulsion. Nopressure had developed within the drum and there was no unusual odor present, Since this time it has been observed that xanthate pine oil suspensions have greatly decreased the possible decomposition of the xanthate solutions. In fact, suspensions have been exposed for more than a month without apparently effecting their reactions in the flotation plant. On the other hand, we found that the regularly mixed concentrated xanthate solutions, after standing for several days, did not give the same results as the freshly made ones. This effect was greatly reduced by the use of xanthate pine oil suspension (or emulsion)

Jan 1, 1958

By G. I. Mathieu

Research and development studies were carried out at the Canada Centre for Mineral and Energy Technology to produce a synthetic forsterite sand from asbestos tailings for Les Sables Olimag Inc. The National Research Council of Canada also supported and collaborated to the project. Theoretically, the technological approach consists of a heat at over 1300°C; however, the process without additive would result in the production of an enstatite-rich product (MgSiO3) having a fusion temperature less than 1600°C. The purpose was to foster the formation of forsterite (Mg2SiO4), a more refractory compound. The fabrication of the forsterite product requires pre-agglomeration of serpentine-MgO with a binder, which is stable at high temperature, to prevent the loss of the powdered magnesium oxide as dust in the kiln off gases and to maintain the mixture homogeneous during the process. Characterization of the end products with respect to mineral composition and thermal resistance are described. The synthetic forsterite in sand form was tested with success under a bath of liquid steel maintained at 1700°C for up to two hours. The advantages of the new sand and its potential applications will be reviewed.

Jan 1, 1992

By Chamila Jinendra Nanayakkara, Nimila Dushyantha, Amila Sandaruwan Ratnayake, Gayithri Niluka Kuruppu

Rare earth elements (REEs) are key ingredients in many advanced materials used in energy, military, transportation, and communication applications. However, the prevailing geopolitical dynamics and the rising demand for REEs have rendered the reliance on primary REE resources susceptible to future supply disruptions, posing a substantial risk to the availability of these elements for numerous applications. Therefore, it is imperative to undertake substantial initiatives in the extraction of REEs from secondary sources on a large scale to ensure the resilience of the supply chain. Permanent magnets, lighting phosphors, and nickel-metal hydride (NiMH) batteries are among the secondary sources with high potential for sustainable REE extraction. This review assesses the extraction potential of REEs from the aforementioned three secondary sources and their leaching kinetics and thermodynamics aspects. More importantly, state-of-the-art different existing kinetic models employed in rare earth (RE) leaching were well discussed for a better understanding of the REE leaching reactions. Furthermore, the optimized leaching parameters related to this kinetics were described, and various RE recovery methods were comprehensively summarized. These processes facilitate to managing one of the fastest-growing solid waste streams by minimizing environmental impacts and producing critical metals, including REEs via circular economy approaches. The recovery of REEs from secondary sources aligns with numerous United Nations Sustainable Development Goals (SDGs), particularly in the renewable energy sector for climate change mitigation. Consequently, this trash-to-treasure urban mining concept to transforming e-waste into a valuable resource for REE recovery emerges as a pivotal element within the REE industry.

Dec 28, 2023

By MOHAMED WAEL, ANASTASIA GOEVA, ABDULAZIZ TAWFEEQI, IHTISHAM TARIQ, S. M. ZAKIR HOSSAIN, NIAZ ALI KHAN, MUHAMMAD FAISAL IRFAN

Carbon capture and storage (CCS) is an attractive area of research in such fields as CO2 mineral carbonation, global warming and sustainable energy systems. In this study, carbonation efficiency for aqueous mineral carbonation (MC) was achieved through two steps,which include leaching of calciumfrom cement kiln dust (CKD) followed by the reaction of pure CO2 with the calcium hydroxide precipitates formed by the hydroxylation using NaOH. Response surface methodology (RSM) with a Box-Behnken design (BBD) was applied to optimize the calciumleaching yield,while the carbonation efficiency from CKD was assessed using RSMwith central composite design (CCD). Optimization of calcium leaching is highly important, as it is a rate-limiting reaction step in MC and also influences and enhances carbonation efficiency. Different parameters including acid concentration (HNO3), leaching temperature, leaching time, and dose of CKD sample were considered in order to optimize the maximum yield of Ca leaching from the CKD sample. In addition, different CO2 flow rates and temperatures were used as parameters for optimizing carbonation efficiency. Two quadratic regression models were developed for each process, i.e. calciumleaching and carbonation. For calcium leaching, a maximum of 98.55% calcium was extracted under the optimal set of acid concentration 4.13 M, 90 °C, 28 min leaching time, and 13.8 g of CKD sample. For carbonation, the maximum carbonation efficiency of 89.2% was achieved for a CO2 flow rate of 1163 cm3/min at 90 °C. Calcium leaching results indicate that the leaching yield was significantly affected by all the input parameters except leaching time. For carbonation, both factors affected the carbonation efficiency, with the effect temperature shown to be greater than that of the CO2 flow rate. Additionally, the predicted results agreed well with the experimental values for both calcium leaching and carbonation processes, with errors of less than 1% and 5%, respectively.

Jun 5, 2020

By S. N. Chadha

INTRODUCTION The work described here refers to the Genesee River Interceptor Southeast Project. This project is a part of the Combined Sewer Overflow Abatement Program, Phase I, for the Rochester Pure Water District, Rochester, New York. Our contract required the design of a 13,200-feet long main tunnel, 14 feet finished diameter, approximately 100-120 Feet below ground; drop shafts and diversion tunnels to deliver surface flow to the main tunnel; a gate chamber whereby the main tunnel is dropped 35 feet, and provision made for connection to the future tunnel in Phase II, as well as a host of other surface structures. Cross sectional dimensions for the structures involved varied from 16 feet circular to a 20'x50' horseshoe, in a competent rock formation consisting of Lockport Dolomite and Rochester Shale. In the construction of a rock tunnel, the problems of the tunnel designers are as follows: 1. To evaluate stresses in the rock as a result of excavation. 2. Design a temporary support system to prevent any rock failure during the period of construction. Design of this temporary support system is empirical. Design loads given by empirical relations are dependent upon the rock quality and size of opening. Temporary support system may either be steel frames closely spaced along the length of tunnel and tied together, in the case of poor rock, or, an even spacing of rock bolts in the case of competent rock. 3. Design a final lining for the service loads. Service loads, in our case of a water-carrying tunnel, are hydrostatic pressure due to ground water, deadweight of lining) pressure of contained water and time dependent rock loading. The constitutive properties of the rock are extremely complex because of discontinuities, pre-existing stresses due to overburden, material symmetries and changes of initial state associated with the process of excavation. The changes of initial state may be changes of stress fields along with the consequent yield of the material or the extension of existing discontinuities.

Jan 1, 1977