Search Documents

By Sarah Wilson, John Kaplin

Plans are underway to extend commuter rail service underground into downtown San Francisco. The Salesforce Transit Center (STC) was completed in 2018 and will serve as a new transit hub, including a commuter rail station after two future connecting tunnel segments are completed. The northern segment, known as the Caltrain Downtown Extension (DTX), which will extend the rail line from its current terminus at 4th and King Streets to the STC, is currently in Preliminary Engineering. The southern segment, the subject of this paper, is a 1.6-mile tunnel known as the Pennsylvania Avenue Extension (PAX), which is currently in the pre-environmental planning stage, with alternative alignments under evaluation including single bore versus twin bore options. This paper discusses project challenges, including highly variable tunneling conditions in soil and rock, a congested urban project site with limited space for construction staging, alignment crossings of large existing buried infrastructure, and complicated interfaces with future and existing rail operations.

Dec 1, 2022

By Gary Peach, Peter Mason

Planning and estimating progress rates and costs for tunnelling is always best done based on experience and historic precedent. Much precedent is available but the use of data monitoring, data mining and other retrieval techniques on modern TBM machines can enable this to be further expanded and refined. Advance rates can be related much more closely to rock types as can associated rock bolt and mesh/ shotcrete requirements. This in turn can lead to a further refinement in best likely combinations of equipment, such as shotcrete jumbos, better selected for the anticipated conditions, rather than the potential advance rates of the machine. Efficient and timely construction of the tunnel will also be linked to times needed for finishing work, such as contact and void grouting and to how this can be initiated while the TBM is still in operation, in order to save overall construction time. Indeed, this in turn may affect the most preferable layout and construction details of the permanent tunnel. Considerable experience has been gained in the use of two large diameter TBM tunnel drives through the Himalayas at the Neelum-Jhelum hydropower project in Pakistan. All the above aspects will be discussed in the paper based on the considerable experience and data which came from that operation, including appropriate measures in highly stressed areas potentially subject to rock burst.

Jun 13, 2021

By R. H. . T. Garnett

Contributed remarks on paper published in the Transactions, Mining industry section, vol. 100, September- December 1991, A121--45

Jan 12, 1992

By Seung Han Kim, Andrew Yu, Carlos Jaramillo, Chu-Chieh Jay Lin

The Penstock Access Tunnel (PAT) concrete plug is a reinforced concrete plug separating the pressure tunnels from the personnel accessible tunnels and has leaked since the first filling at the Helms Pumped Storage Plant located in Fresno County, California. A grouting program was successfully implemented in 2009 to reduce the leakage from PAT concrete plug from over 1,000 gpm to 25 gpm. Recent observations indicated increasing water leakage through new pathways, leading to a decision to execute a high-pressure grouting and waterproof membrane installation program in 2017. The high-pressure grouting and membrane installation program was successfully executed in the areas adjacent to the PAT concrete plug where most of the inflows originated and the largest hydraulic gradients are suspected to present. It reduced the leakage from over 300 gpm of inflow to less than 20 gpm.

Jun 13, 2021

By Ben DiFiore, Richard DePew, Nate Long, Adrian Naranjo-Castillo, Chris Petta, Robert Auber

The Walworth Run stream was brick-culverted in the 1800s, converting it to a 16-ft diameter sewer. This Cuyahoga River tributary contributed to the infamous burning river that became the catalyst for USA’s environmental movement. The NEORSD has been working hard to reduce CSOs here, most recently by diverting Walworth Run’s 882 MGD of flow to the new Westerly Tunnel. This had to consider structure age/size, alluvial/glaciolacustrine deposits (requiring several ground support systems, groundwater control), and maintenance of massive flows. This paper examines challenges identified during design that supported the contractor in development of a risk-mitigating plan, culminating to successful implementation.

Dec 1, 2022

By Joaquín Copaja

Highly fertile magmatic conditions for porphyry copper formation, such as high water content, can be recognized in zircon trace element chemistry using proxies as the 104(Eu/Eu*)/Yb ratio. Due to their resistance to alteration and long-distance transport, zircons hosted in sedimentary sequences can be used to assess fertility over large detrital source areas. Herein we present a study based on LA-ICP-MS analyses of zircons derived from post-Oligocene sedimentary sequences cropping out across the Paleocene-Eocene Cerro Colorado district of Northern Chile. U-Pb dating on individual detrital zircons yielded ages ranging from Jurassic to Miocene, concordant with the district geology. Subsequent fertility assessment recognized several peaks in the magmatic hydration over time.

May 10, 2023

By Mirko Martini, Marcelo Benaglia, Andrea Codalli

Riachuelo Lot 3 forms part of a sanitation programme being implemented in Argentina to relieve the Riachuelo river basin from its current contamination. The programme, by far the most important in its kind in the country during the last decades, will expand the sewage capacity of Buenos Aires and will benefit an area of 4.3 millions inhabitants by intercepting a number of waste water discharges and conveying them to a new treatment plant prior to final discharge into the Rio de la Plata. The project foresees amongst other works the construction of an onshore 48 m deep shaft at the outlet of the treatment plant plus a 4,3 m inner diameter outfall tunnel of 12 km length. The last 1.5 km of the alignment is fitted with 34 vertical risers jacked from inside the tunnel to allow the discharge and dilution of the treated effluent into the Rio de la Plata. This paper describes the peculiarities and challenges, both in terms of design and in terms of construction, of the outfall tunnel, which was entirely bored under the Rio de la Plata using a 5.2 m cut diameter Tunnel Boring Machine (TBM). On one hand, the tunnel segmental lining was designed to work in tension during the system flow rate peaks while on the other the tunnel excavation faced a variety of complex conditions, such as crossing water bearing permeable soft ground formations and advancing at face pressures in excess of 3,5 bars for the entire route.

Jun 13, 2021

By B. Sonmez, B. Aksanl, S. Ersaym, I. F. Erkal, S. L. Ergun

The comminution circuit at the plant has experienced severe problems arising from a feed containing much larger amounts of clay and having a higher moisture content than expected. Three solutions were proposed: replacement of the crushing circuit by tooth roll-type crushers; using washing drums; and introducing primary autogenous/semi-autogenous millling instead of crushing. Computer simulations studied the effects of the first two solutions on the circuit capacity. Laboratory and industrial scale ball mill batch grinding tests were carried out. The parameters of a kinetic model were determined. The ball mill circuit was sampled and operating model parameters were calculated. The ability of batch grinding parameters to represent the operating conditions was studied. Tests failed to find acceptable model parameters, but parameters from an industrial size batch mill were found to be suitable for simulation studies. The simulations indicated that a continuous feed of -12 mm provided by tooth roll crushers would maintain the desired capacity. Increasing the feed size to -25 mm would reduce the capacity by 8-15%. The use of washing drums could also solve the capacity problem, but small fluctuations in water flow rates might result in problems of excess water in the grinding circuit.

Jan 4, 1993

By Lauro Lacerda

Shotcrete is a highly adaptable and widely used underground construction material at infrastructure and mining projects around the world. In fact, many projects could not have been completed without its utilization. As underground projects became larger the use of mechanized wet-mix spraying gradually replaced manual dry-mix shotcrete applications. This paper details some of the reasons for that and provides information on the equipment and operational factors including safety and productivity required to successfully complete underground shotcrete projects.

Jun 13, 2021

By Stefan Mede

Automation in segment production doesn’t necessarily mean the use of robots. Several other aspects of automation in the process are available. Herrenknecht has collected many experiences in the automation process of carousel systems for segment production, implemented several robot systems and launched new artificial intelligence-based camera system supporting the production team in the quality control This paper is a follow up of the presentation on Automation in Segment Production held in 2021 at the RETC.

Dec 1, 2022

By Roland Arnold, Richard Gradnik, Martin Zeindl

This paper presents the details of the Kramer tunnel project in the Federal State of Bavaria, Germany. This road tunnel, which has been under construction since December 2019, is the key component of the western bypass of the town of GarmischPartenkirchen. Once completed, it will relieve the town’s central district from enormous volumes of traffic. The contractor is the joint venture named ARGE Kramertunnel consisting of BeMo Tunnelling and Subterra. The whole project will be completed and handed over to the project owner, Staatliches Bauamt Weilheim, in 2023. The opening of the entire bypass section including the tunnel to traffic is planned for 2024. The tunnel, with a total length of 3,609 m (2.24 miles) and an estimated cost of EUR 178 million (incl. VAT), is designed as a single-tube, double-lane structure with one traffic lane for each direction of travel. The safety issue that exists for single-tube tunnels is solved by a parallel escape tunnel passable for vehicles. All tunnels and ducts are excavated according to the principles of the New Austrian Tunnelling Method (NATM). In order to reduce the geological risk for the owner, the escape tunnel was supposed to be completed before the design process for the main tunnel ever began. The exploratory tunnel was awarded to a competitor with an separate contract.

Jun 13, 2021

By Albert H. Fay

This glossary is published by the Bureau of Mines as a contribution to the mining literature in the belief that it will fill a long-felt need. It contains about 20,000 terms; these include both technical and purely local terms related to metal mining, coal mining., quarrying, petroleum, and natural gas, and metallurgical works; names of useful, important, and common minerals and rocks; and geological terms. It presents in one comprehensive volume the available standard, technical terms relating to the mining and mineral industry, as well as provincialisms that have been or are now in use in English-speaking countries. The glossary also includes many terms relating to ceramics and. the clay industry, glass making, foundry practice, railway and building construction, electrical installation and power-plant equipment, and chemical terms relating to metallurgical practice. Complete lists of terms for each of these allied industries are beyond the scope of this glossary. Paleontological terms, although closely associated with geology, are far removed from mining and metallurgical operations, and for this reason have been omitted.

Jan 1, 1920

By Cissé Kane, Klaus Hieronymi, Mathias Schluep, Gerry Newson, Susanne Dittke

"E-waste is currently the fastest growing waste stream in South Africa as well as in many other African countries. Informal collectors, dismantlers and recyclers based in Africa play an increasingly larger role in the processing of e-waste under generally unacceptable social and environmental conditions. In direct response to this trend, and as part of Hewlett Packard’s international Extended Producer Responsibility, the project “e-Waste Management in Africa” was started in 2007 in cooperation with the Global Digital Solidarity Fund (DSF) and the Swiss Federal Laboratories for Materials Testing and Research (Empa). This project is investigating the e-Waste situation in various African Countries, including South Africa, while actively supporting the development of practical, socially just and environmentally acceptable local e-waste management solutions. To this end, the project has been funding the development of a pilot project in Cape Town, South Africa since February 2008, supporting the start-up of a low tech/highly labour intensive material dismantling and recovery facility (MRF) for the pre-processing of e-waste. The aim is to test the feasibility of an integrated value adding local e-Waste management system, designed to maximize the potential of refurbishment, repair, re-use, dismantling and recycling of equipment, with environmentally responsible disposal as a last resort only. The project also seeks to incorporate the current informal e-waste processing activities, by transforming them into sustainable and environmentally sound operations. The MRF acts as a nucleus, raising awareness, and providing training and education to previously disadvantaged individuals as a means of creating opportunities for entrepreneurship in the technical maintenance, dismantling and waste-to-art project sectors."

Jan 1, 2008

By Philip W. Johnson, Charles D. Haynes

"Abstract - The coalbed methane industry has become a prominent source of domestic natural gas, with its technology having evolved over the past 30 years. Whereas most coalbed methane wells are able to produce without major interruption over their economic lives, wells operating in an underground mining area are subject to being mined-through. If mine-through occurs, the productivity of the well is at least compromised, and may even be terminated. The economic consequences of mine-through may be relatively simple if mineral ownership and extraction rights are common for the coal and coalbed methane. However, if ownership is not common and a superior coalbed methane lease exists, the coalbed methane ownership must be compensated for lost production caused by mine-through. This paper presents a relatively straightforward method to calculate the value of the lost production caused by the mine-through. It uses technology from mining and petroleum engineering, as well as simple economics and financial management techniques.Sommaire - L’industrie de la production de méthane houiller est aujourd’hui une source importante de gaz naturel domestique dont la technologie a considérablement évolué au cours des trente dernières années. Bien que la plupart des puits de méthane houiller peuvent être mis en production durant l’entièreté de leur vie utile sans interruption majeure, les puits implantés en périphérie de mines souterraines sont sujets à être recoupés par ces dernières. Un tel recoupement peut compromettre, ou même mettre fin à la production d'un tel puits. Les conséquences économiques du recoupement par une mine souterraine peuvent être relativement simples quand les droits miniers et les droits d’extraction sont détenus en commun pour le charbon et le méthane houiller. Si toutefois ces droits ne sont pas détenus en commun et qu’il y a eu octroi d’une concession de méthane houiller de qualité supérieure, les détenteurs du méthane houiller doivent être compensés pour la perte de production résultant du recoupement par une mine souterraine. Cet article présente une méthode relativement simple pour calculer la valeur des pertes de production suite au recoupement par une mine souterraine. Cette méthode fait appel aux technologies de l’industrie minière et pétrolière ainsi qu’à des techniques simples d’économie et de gestion financière."

Jan 1, 2006

By N Weerasekara, M Bird, M Yahyaei, M M. Hilden, M S. Powell, J Franke, P Toor

The combination of new tools with a more rigorous approach to understanding the interaction of mill liners with overall mill performance and economics, forms the basis of an integrated approach to liner management. Based on accurate liner wear measurements, some (limited) physical mill inspections and surveys, accurate calibration of the mill load and analysis of process data, a whole new approach to liner selection, relining intervals and mill control is proposed. Collection and analysis of this information in operating mills illustrates the mill performance improvement which can be attained through this careful measurement and modelling approach.A more holistic approach to liner management is proposed, including a broadening of the current work to cover the potential benefits of improved relining technologies and predictive liner wear modelling. CITATION:Powell, M S, Hilden, M M, Weerasekara, N, Yahyaei, M, Toor, P, Franke, J and Bird, M, 2012. A more holistic view of mill liner management, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 95-104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By Frederick W. Breaks, Andrew G. Tindle, Julie B. Selway

"Abstract - Rare-element pegmatites may host several economic commodities, such as tantalum (Taoxide minerals), tin (cassiterite), lithium (ceramic-grade spodumene and petalite), and cesium (pollucite). Key geological features that are common to pegmatites in the Superior province of Ontario and Manitoba, Canada, and in other large tantalum deposits worldwide, can be used in exploration.An exploration project for rare-element pegmatites should begin with an examination of a regional geology map. Rare-element pegmatites occur along large regional-scale faults in greenschist and amphibolite facies metamorphic terranes. They are typically hosted by mafic metavolcanic or metasedimentary rocks, and are located near peraluminous granite plutons (A/CNK > 1.0). Once a peraluminous granite pluton has been identified, then the next step is to determine if the pluton is barren or fertile. Fertile granites have elevated rare element contents, Mg/Li ratio < 10, and Nb/Ta ratio < 8. They commonly contain blocky K-feldspar and green muscovite. Key fractionation indicators can be plotted on a map of the fertile granite pluton to determine the fractionation direction: presence of tourmaline, beryl, and ferrocolumbite; Mn content in garnet; Rb content in bulk K-feldspar; and Mg/Li and Nb/Ta ratios in bulk granite samples. Pegmatite dikes with the most economic potential for Li-Cs-Ta deposits occur the greatest distance (up to 10 km) from the parent granite.Metasomatized host rocks are an indication of a nearby rare-element pegmatite. Metasomatic aureoles can be identified by their geochemistry: elevated Li, Rb, Cs, B, and F contents; and by their mineralogy: presence of tourmaline, (Rb, Cs)-enriched biotite, holmquistite, muscovite, and rarely garnet.Once a pegmatite dike has been located, the next step is to assess its potential to contain Ta mineralization. Pegmatites with the highest degree of fractionation (and thus the most economic potential for Li-Cs-Ta) contain blocky K-feldspar with >3,000 ppm Rb, K/Rb < 30, and >100 ppm Cs; and coarsegrained green muscovite with >2,000 ppm Li, >10,000 ppm Rb, >500 ppm Cs, and >65 ppm Ta. Pegmatites with Ta mineralization usually contain Li-rich minerals (e.g., spodumene, petalite, lepidolite, elbaite, amblygonite, and lithiophilite) and may contain Cs-rich minerals (e.g., pollucite, Cs-rich beryl). The ore minerals of Ta are commonly manganotantalite, manganocolumbite, wodginite, and microlite; Ta-rich cassiterite is also commonly present. Tantalum mineralization tends to occur in albitic aplite, mica-rich (lepidolite, cleavelandite ± lepidolite), and spodumene/petalite pegmatite zones."

Jan 1, 2005

By A. Dadgar, R. H. Sergent

Changes in the ore types available and increased environmental concern have created a demand for an alternative technology to cyanide for the extraction of gold from ore. Great Lakes Chemical Corporation (Great Lakes) believes that halogen chemistry, in particular bromine chemistry, is the best available alternative to cyanide for gold extraction. Great Lakes is a Fortune 500 chemical company with sales of approximately one billion dollars per year. Great Lakes extracts elemental bromine from naturally occurring brines in Southern Arkansas. Great Lakes has developed a family of proprietary bromine compounds to aid in the extraction of gold. In addition to proprietary bromine compounds for gold extraction, Great Lakes has developed a method of recycling bromide ion in the leach circuit. Various recovery methods, including ion exchange and solvent , extraction are currently being studied.

Jan 1, 1990

By John A. Lombardi

The solutions used in the heap biooxidative treatment of sulfidic refractory Au ores and concentrates generally load free mineral acid and metals and, in time, become bacteria activity inhibiting due to increased acid and/or metals concentrations. The metals­acid loaded, bacteria action inhibiting, solution must then be: (a) processed, prior to re-use, to reduce its metals and/or free acid mineral acid components to bacteria activity compatible levels; or (b) neutralized prior to discharge. The most common solution processing method to adjust acid-metals contents is liming to effect the precipitation of dissolved metals and neutralization of acid sufficient for solution discharge or re-use. The lime treated solution is high in suspended, colloidal precipitates and requires clarification before reuse. Most often the "bleedstream" of biooxidation solution that is lime treated is discharged and req­uisite volumes of fresh water added to the process inventory. Depending on the level of bacterial action in a heap and the acid consumption characteristics of the ore/concentrate being biooxi­dized, the bleedstream taken from the circulating, irrigation on­off, solution, can be large (e.g., 10%-20% and sometimes as much as 50% of the daily solution flow requires treatment-dis­charge). The lime charge for bleedstream treatment is commen­surately large and represents a major operating cost of the bioox­idation process. The patented HW Process Technologies (HWPT) Engineered Membrane Separation (EMS™) method is an alternative biooxi­dation bleedstream treatment method. EMS™ processing removes the multivalent base metals ions in an acid solution to a small volume EMS™ "concentrate" (typically 25% of the feed­stream volume). The EMS™ method coincidentally makes a "clean acid" EMS™ "permeate" (typically 75% of the feed­stream volume). In general, EMSTM processing enables 75% of the bleedstream volume to be recycled; allows up to 2/3 of the bleedstream acid to be recovered as a 10% solution; and delivers dissolved metals in a highly concentrated stream suited to a. metals recovery or b. reduced cost lime neutralization for a given metals precip­itation relative to full bleedstream neutralization (typically a 30% lime use savings). Implicit in the recovery of process water for re-use and reduced reagent addition requirement for metals precipitation is a significant reduction in wastewater-sludge dis­posal facility size.

Jan 1, 1998

By Michael G. Strominger, Anthony E. Gross

The development of precious metals ore agglomeration with a cement binder, by the U.S. Bureau of Mines, has allowed the economical heap leaching of low grade gold ores (<0,05 oz/ton) over the last decade, Even with the Bureau of Mines technology, numerous operations continue to experience channeling and blinding problems. A research project was undertaken at Nalco Chemical to address situations where improved agglomeration is needed, By increasing the incorporation of fines into the agglomerates,the segregation of ore by size which occurs from handling will be reduced and channeling minimized. A stronger agglomerate will reduce fines migration during leaching and prevent blinding of the heap, Both of these changes will give an even flow of barren solution throughout the heap and give solution contact with all of the ore. This paper presents the development of polymeric agglomeration aid, Nalco 9760 which has given a higher rate of and a higher total gold recovery in plant evaluations.

Jan 1, 1990

By Rod Knopp

Each year approximately 5,000 tons of a sulfide concentrate grading 1 ounce gold per ton are produced at this operation. The material is refractory and as shipping costs and custom smelter charges increase, options to process it on site are becoming more attractive. Three methods of treating the ore have been investigated in detail. The first option of ultra fine grinding the concentrate produces a 35% gold recovery with relatively low capital and operating costs. A second option of pressure oxidation is very capital intensive and has high operating costs but recoveries in the order of 95% are achievable. The final option, biological leaching offers both capital and operating costs which are less than pressure oxidation, while still achieving 90% gold recoveries. Bioleaching of gold concentrates has been gaining acceptance but there is a risk factor associated with this or any emerging technology.

Jan 1, 1990