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By Paul Russell, M. M. Kimberley, Erick F. Welland, Louis Cope, C. C. Mosher, William M. Shepard, William C. Larson, Graham Closs

Exploration activities in 1980 felt the effects of unstable economic conditions and oscillating metal prices. In the cyclical, boom-or-bust precious metals and uranium markets, precious metals activity flourished and uranium was definitely in a slump. By November last year, the price for vellowcake was down nearly $20 from two years earlier. Many mining and milling operations closed, particularly in Wyoming, New Mexico, and Colorado. Decreasing emphasis on nuclear power continued to impact the market, as did the Three Mile Island accident of 1979. Earlier forecasts estimated that 10 to 12 reactors would be ordered per year by US utilities throughout the 1980s, but current forecasts suggest that it may be 1983 or 1984, or even later, before any new US plants are ordered, according to Thomas A. Boyden, vice president of Nuclear Exchange Corp. "Without those new plants, the consumption loss to industry is 4 to 5 million pounds (1.8-2.3 kt) of uranium per year. The cumulative loss to the industry is currently estimated at 25 to 30 million pounds (11.3-13.6 kt)," Boyden said in a May 1980 presenta¬tion. Despite the plunging market, there were a few notable uranium explora¬tion programs: •Exxon expanded uranium exploration in New Mexico, where the company reportedly took preliminary steps toward acquiring mineral rights to a 22-km2 prospect, 19 km south of Santa Fe. • Mountain States Resources began the second phase of an exploratory drilling program on its Sinbad/ Solo prospect in Utah. • Also in Utah, Cotter Corp. drilled its first exploratory hole in the Dirty Devil River district. Exploration for precious metals in 1980, however, appeared to tend toward the opposite extreme. High prices sparked near feverish searches in Alaska, California, Colorado, and Nevada. Numerous mines abandoned years ago were revived with some signs of success. Significant gold finds were reported in California and Nevada: • Homestake Mining Co. announced a gold discovery in California estimated to contain over 5 Mt with an average grade of about 5.8 g/t. Because the deposit consists of finely disseminated particles not visible to the eye, many speculate that prospectors bypassed the area during the 1849 California gold rush. • Newmont Mining Corp. discovered two gold ore bodies-Maggie Creek and Gold Quarry. Maggie Creek reportedly contains an estimated 13.7 t of gold in 4.3 Mt of ore, and Gold Quarry contains about 31.1 t of gold in 9 Mt of low grade ore and 2.3 Mt of higher grade ore. Highlights of this year's exploration review include articles on the modest growth recorded in geophysical activity, technical developments in exploration geochemistry, the variety of new instruments being tested or made available for exploration, and a state-by-state exploration review for the year.

Jan 5, 1981

By Murat Erdemoğlu, Turan Uysal, Thierno Saidou Barry, Mustafa Birinci

The rapid development of the global alumina and aluminum industry is straight coupled with the demands and the needs of these materials. Nowadays, the only well-known accessible resources to produce alumina and aluminum are bauxite ores. But bauxite ores are limited, and the remaining exploitable reserves do not have high contents in alumina. In countries where there is little or no bauxite reserves or where the recovery of existing bauxite ores to produce alumina with the Bayer process are not economic, alternative resources for alumina have been explored. The most attractive resources for replacing bauxites are aluminosilicate clay minerals and coal fly ash. The important processes developed for the recovery of alumina from these sources are acid leaching and alkaline leaching processes. The acid leaching is known as the most efficient in which thermal and mechanical activation are included for improving the performance of the process. The objective of this review is to give a comprehensive insight on the production of the alumina from thermally or mechanically activated clays and coal fly ash by hydrochloric, sulfuric, and nitric acid leaching processes.

By Osvaldo Bascur, Barun Gorain, Jaco Steyn

"The last few decades have seen some remarkable advancement in information technology, but recently various digital technologies have resulted in several synergies to deliver innovation in diverse applications. The mining industry has been relatively slow in adopting these technologies compared to the other industries, but this scenario is changing fast.Challenges. Mining companies globally are going through a series of challenges such as declining ore grades with complex metallurgy, increasing depth of ore bodies, high capital and operating costs, lower productivity, shortage of technical resources, significant pressure from stake-holders to deliver, along with growing environmental and corporate social responsibility issues. Improvement in profitability would need significant improvements in operational performance.Consequently, over the last few years, there has been a major focus among some mining companies to imbibe operational excellence. This has been only possible because of the replacement of a silos-based approach by an integrated view of the organization. Such an integrated view is now possible via the evolving digital technologies. Even so, such a transformation calls for a change in culture, which, for most organizations is not trivial. Attempts in the past to integrate functions, such as through mine-to-mill initiatives in the mining industry, have demonstrated significant benefits to many operations (McKee, 2013). Still, sustaining these benefits has clearly been a challenge due to manpower turnover and lack of proper systems and structures that integrate information between business functions within an operation and between operations and the corporate level.Opportunities. The advent of digital technology has opened up opportunities to integrate interdepartmental information for a unified understanding across an entire organization. The advances in instrumentation, equipment control systems, supervisory control systems (SCADA/ Historian) and industrial networks have helped in the direction of enterprise- wide integration. The availability of real time information across an enterprise has given rise to numerous possibilities to improve organization performance. As suggested by Seshan and Gorain (2016), some of the potential opportunities are as follows:"

Jan 9, 2018

By K. Huttu, A. van Wageningen

"The Kittilä underground mine in northern Finland is extracting one of the largest known gold deposits in Europe. Kittilä achieved commercial production on May 1, 2009, becoming Agnico Eagle’s first mine to open outside of Canada. The Kittilä orebodies were initially mined from two openpits – Suuri and Roura – and underground operations were added in October 2010. The pits were mined out in November 2012, so mining is now entirely underground in the Suuri and Roura deposits. Additional, small openpits will mine any remaining near-surface reserves in the future.The Kittilä Mine is located in the Lapland region of northern Finland, approximately 900 km (560 miles) north of Helsinki and 150 km (93 miles) north of the Arctic Circle. With a mine life estimated through 2034, Kittilä is Agnico’s longest-life mine.The mine’s proven and probable reserves contain 32 Mt (4.7 million oz) at 4.6 g/t (0.13 oz/ st) gold. Ore has been mined from underground since 2010. The original 3 kt/d (3,300 stpd) operation underwent an expansion project to increase the throughput capacity of the mill by 1 kt/d (1,100 stpd), starting by the end of 2014.The region around the Kittilä Mine is underlain by mafic volcanic and sedimentary rocks of the Kittilä Greenstone Belt oriented nearly vertical. This greenstone belt is similar to those hosting Agnico Eagle’s Canadian deposits in Quebec’s Abitibi region and Nunavut. At the contact point between ironrich and magnesium-rich rocks lies a 100- to 200- m (330- to 660-ft) thick structural zone known as the Suurikuusikko Trend. This trend hosts the Kittilä deposit, where multiple mineralized zones have been traced over a strike length of more than 25 km (15 miles).Most of Agnico Eagle’s work has focused on a 4.5-km (2-mile) segment of the Suurikuusikko Trend that hosts the five main zones of the known gold reserves and resources. From south to north they are: Ketola, Etela, Suuri, Roura and Rimpi.The ore at the Kittilä Mine is refractory, making gold extraction relatively difficult because the gold is generally locked inside the two main sulfide minerals – arsenopyrite and arsenic-rich pyrite. Only about 4 percent is very fine-grained “free gold” (not locked in sulfide grains) and easier to extract. Most of this free gold is found in the outer, oxidized or eroded sections of the ore."

Jan 1, 2015

By R. F. Balazik

By March 2001, shrinking global markets, reduced consumer spending and declines in domestic manufacturing and industrial output ended the longest economic expansion in US history and pushed the nation’s economy into its first recession in a decade. Aggravated by the terrorist attacks of Sept. 11, the recession led to large reductions in the domestic production of processed mineral materials. Some of the most significant production declines in the US metals industry were registered by aluminum, copper and steel producers. They faced strong foreign competition, higher energy costs and lower prices for their products. However, homebuilding and other domestic construction sectors — major users of nonmetallic mineral products such as cement, brick, glass and stone — remained strong enough to help raise the output of industrial mineral materials slightly above previous year levels. A strong US dollar continued to weaken the competitive stance of US metal and nonmetallic mineral materials companies alike against foreign producers in markets at home and abroad.

Jan 1, 2002

Multilevel-multiseam hardcoal mines on the European continent usually consist of a huge network of underground openings, sometimes more than 200 km long in total, with some longwalls operating down to a depth of 1,500 m. While operating several longwalls simultaneously, these mines are making use of a number of stationary and mobile measurement- and analysis units in their main ventilation passes combined with atmospheric measurements on the surface. This paper provides an overview over the systems and technology used and describes the typical set-up of a measuring net. To detect and monitor underground fires through fire gases measurement and -analysis, a mobile underground testing laboratory collects data locally in the area of the fire. These laboratories have proven to be extremely useful not only during the actual fire fighting but also for the long-term gas measurements in critical mine areas. They have repeatedly detected starting fires and have thus given the mine the opportunity to react early and to avoid larger damage. Therefore several mobile laboratory units have now been installed for long-term testing in a number of German mines and similar units are being used in the Czech Republic and Poland.

Jan 1, 2012

By Rick Coleman

PT Freeport Indonesia’s (PTFI) latest expansion has increased total mill throughput to 125kt/d (137,700 stpd). The most recent expansion included the installation of a semiautogenous mill (SAG) designed to treat more ore than any other single SAG mill currently operating in the world. Also included in the expansion were two large ball mills, rougher and cleaner flotation, including conventional and column cells, and a regrind circuit. All equipment is supported by a modern distributed control system. PTFI’s operations are located in the Ertsberg mining district of Irian Jaya’s Jayawijaya Mountains, the eastern-most province of the republic of Indonesia on the Island of New Guinea. PTFI, the operator, is owned by Freeport McMoRan Copper and Gold (81.3%), the government of Indonesia (9.4%) and private Indonesian investors (9.3%).

Jan 1, 1996

By Brad Murray

Evaluating the performance of a shielded tunnel boring machine (TBM) can be difficult because the ground cannot be observed directly and in relation to the TBM attitude within the excavation. It is difficult to determine whether performance problems are caused by ground loading, steering issues, fine muck packing against the shield, or migration of annular grout around the shield. The Arrowhead Tunnels Project in Southern California uses strain gauges on its shielded hard rock TBMs to detect shield strains early and correlate them with tunneling conditions, thereby increasing the chances that problems will be correctly diagnosed and addressed to optimize TBM performance. The frequent automatic measurement of shield strain has also been valuable by confirming whether remedial methods used to free the machine after stoppages are effective. This paper discusses the qualitative interpretation of characteristic strain patterns on the Arrowhead Tunnels TBM shields and discusses installation details and special considerations for setting up a strain measurement system.

Jan 1, 2008

By Peter Haller

Introduction The impact of the Comprehensive Environmental Response, Compensation, and Liability Act, or Superfund, as well as the Resource Conservation and Recovery Act (RCRA) and their state counterparts underscore the intention of the nation's lawmakers to reduce the risk from hazardous substance to American society. The promises and requirements embodied in these laws, together with their prospects for liability, will continue to have a very substantial impact on decision making in the mining industry. These laws present the prospects for staggering liabilities, often of an unquantifiable nature in terms of time and amount. It is therefore necessary to keep them in clear focus. This is particularly true in light of President Reagan's signing into law the Superfund amendments on Oct. 17, 1986, and in light of the Environmental Protection Agency's (EPA) major policy pronouncement of July 3, 1986, regarding solid wastes from extraction of ores and minerals. This article examines the general trends as well as the specific provisions of these laws in an effort to assess the prospects of liability for the mining industry of releases of hazardous substances into the environment. Hazardous substances vs. hazardous wastes The distinction between the terms "hazardous substances" and "hazardous wastes" is important to appreciate for the purposes of assessing the potential for liability for a mining operation. Hazardous substance is a term that appears in and is defined in the Superfund Act. In Superfund, it is defined by reference to other substances that have been declared to be hazardous under other federal environmental statutes, such as RCRA, the Clean Air Act, and the Clean Water Act. Hazardous waste is a term that is less all-encompassing than hazardous substance, as that term is defined by RCRA. Hazardous substances do not need to be wastes to be considered hazardous for the purpose of Superfund liability. A "release" of a hazardous substance into the environment can bring about potential liability under Superfund. Many mining wastes, even though they are not considered hazardous wastes by EPA under RCRA, have been determined by that agency to be capable of bringing about liability under Superfund if they contain chemical substances, such as the heavy metals copper, lead, mercury, zinc, silver, and others. Therefore, it is not sufficient for the mining industry to be able to answer whether one has hazardous waste at a mining site. That question only goes partway in addressing the potential for liability. The next question is, do one's solid or liquid mining wastes contain hazardous substances that could bring about liability under Superfund? Superfund 1980 law: A review Some provisions of Superfund as it existed before its recent amendments must be considered. The law provides that the owners and operators of mining sites, together with those who transport hazardous substances to such sites, can be held jointly and severally liable for the cost of cleaning up the site. The concept of joint and several liability means that one party, as among many, can be held totally responsible for the costs of cleanup. This is particularly true where the harm done by many parties to the envi-

Jan 2, 1987

By Robert A. Clifton

It seems probable that more and more minerals will be used in plastics as time goes on. This must occur because the minerals will; aid in processability, enhance the engineering properties, reduce the cost, and above all conserve large amounts of petroleum based chemicals. This paper examines the advantages and disadvantages of using the minerals and the ability of the domestic minerals industry to support this possibly very large undertaking. In the author's opinion, it can. This talk is excerpted from a forthcoming Bureau of Mines Information Circular.

Jan 1, 1985

By H. Hejny

"The mine of the future will exploit mineral raw materials at greater depths than today, requiring completely different approaches compared to today’s deep mines, in order to get mineral rights. Only these eco-efficient mines will contribute to improved access to domestic mineral resources, secure the sustainable supply of mineral raw materials for Europe and reduce the import dependency. IntelliMine will contribute to realise these concepts of invisible, zero-impact and safe mines. The mine of tomorrow will run an integrated concept in order to guarantee the desired level of sustainability. All operations necessary for the eco-efficient provision of the minerals including waste management will be carried out underground. This will drastically reduce the volumes being transported, minimising above ground installations and thus the environmental impact. IntelliMine will develop necessary innovative methods, technologies, machines and equipment for the safe, eco-innovative, intelligent and economic exploitation of mineral raw materials in the EU, especially at greater depths."

Jan 1, 2011

By C. C. Jobes

Operating large face equipment, such as continuous mining machines, is one of the most basic and most dangerous elements of an underground coal mining operation. The operator usually performs cutting and tramming tasks in a restricted workspace with reduced visibility. During the execution of these tasks, operators often cannot see all of the locations needed to safely operate the continuous mining machine (CM ), which has sometimes resulted in accidents. In an effort to prevent these accidents, researchers at the National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory, examined the continuous mining machine operator?s current information cues, or visual attention locations, so that risk of injury relative to the task, equipment and workplace environment can be evaluated in the future. The eventual goal is to develop interventions to enhance the information cues, and thereby increase the safety and health of machine operators. This paper details the operator interview process, determination of visual attention locations (VALs) and simulation of various mining scenarios.

Jan 1, 2011

By Steve Kral

As the mining industry watches commodity prices continue to soar, the question on most everyone’s mind is how long will this upcycle last. The con-census among speakers and attendees at the SME Annual Meeting and Exhibit is that this cycle is sustainable. The buzz at the meeting was, of course, the current boom cycle the industry is in. Most agree that China’s huge appetite for mineral commodities is part of the force driving the upturn. But the improving economies of other developing nations also plays a role. However, along with the good times come challenges. Speakers at the keynote session addressed some of the challenges and offered their opinions on the sustainability of the boom.

Jan 1, 2006

By Georgene Renner

At the beginning of the 1990s, Communism fell and signaled the end of the Cold War. The world rejoiced but also watched and waited to see how those countries would restructure themselves. The 1990 SME Annual Meeting was held at the Salt Palace Center in Salt Lake City, UT. The keynote session featured Alistair Frame, chairman of RTZ; Paul Queneau, professor of metallurgy at the University of Utah; and TS Ary, director of the U.S. Bureau of Mines. The SME Board of Directors voted to hire a Manager of Public Information and Education to be the GEM Program coordinator. This person was to collect and disseminate information that could be used by individual members and Local Sections to interface with government personnel and the general public.

Jan 1, 2007

By John B. Gustavson

This paper describes a case history of geochemical prospecting. An area of known mineralization was available for an orientation survey which led to the selection of elements and criteria for a reconnaissance survey in the area offsetting the known mineralization. Certain anomalies were found which were then made subject of confirmation sampling and of rock geochemical investigations. Inasmuch as the geochemical prospecting technique specifically led to a detailed area which now serves as a target for drilling and other exploration efforts, the geochemical prospecting part of the program is considered successfully concluded and, therefore, reported on here. Whether the target area will turn out to host the deposit or not is, of course, of utmost importance to the Company, but is of less importance to this paper. We will describe the concepts, the planning, the execution, the analysis and the interpretation of this typical geochemical prospecting case. A number of people on the staff of International Oil & Gas, Inc. have participated in this prospect, as have students from Southeast Missouri State University and their professor, Gary M. Lowell. In addition, the Missouri Geological Survey has been most helpful with records and letters on the century-old prospecting and mining in the general area. Many valuable discussions have also been held with geologists from the industry who, from time to time, have visited the area, examined the property and reviewed the status of the project. The support and interest from all these parties has made it possible to pursue and expand this exploration concept from one of being just "more of the same kind" to the most chal-1enging and exciting with which this author has ever been involved, namely the prospect for tin porphyry deposits in the mid-continent United States.

Jan 1, 1977

By Erika Moonin, Jim Nickerson, Claudio Cimiotti, Roberto Bono

"In response to the severe drought on the Colorado River basin and in order to preserve existing water capacity to the Las Vegas Valley, the Southern Nevada Water Authority contracted a new deep-water intake (Intake No. 3) located in Lake Mead. The current project (Contract No. 070F-01-C1) includes 5 km (3 miles) of tunnel with very difficult geological conditions and a 200- m (650-ft) deep shaft and marine works. This paper will present the current status of the design-build contract being constructed by Vegas Tunnel Constructors and the challenges and problems faced and the innovative solutions developed to handle the difficult conditions encountered during tunneling with up to 15 bars of pressure.ProjectbackgroundThe Las Vegas Valley receives the majority of its water from Lake Mead, which is located approximately 30 km (20 miles) east of the Las Vegas, NV metropolitan area. Due to the severe drought that has hit the southwest region of the United States, the water level in Lake Mead has receded from its high water level of 372 m (1,221 ft) above mean sea level (amsl) to a low of 330 m (1,076 ft) amsl in June 2015. Should the lake level continue to fall, at elevation 320 m (1,050 ft) amsl, the current water intakes will not be able to draw enough water to meet the needs of the local area. The risk of losing water capacity has prompted the construction of a new deeper intake. Not only is the new Intake No. 3 situated at a lower elevation in the lake at 262 m (860 ft) amsl, the new Intake No. 3 is also located to draw better quality (Fig. 1).Project challengesThe project has had several difficult challenges to overcome:• The work consisted of a 1.2 kt (1,300 st) structure constructed on a barge and lowered 100 m (330 ft) into Lake Mead anchored with 9,200 m3 (12,200 cu yd) of tremie concrete.• The drill-and-blast starter tunnel was impacted by three inflow events, resulting in a one-year project delay.• One of the main challenges was selecting the tunnel boring machine (TBM) and excavating the tunnel with expected hydraulic head pressure of as much as 17 bar (16 bar was the highest pressure recorded during the drive), crossing faulted areas, low rock cover and the risk of tunnel instability due to direct connection with the lake.• Extensive pre-excavation grouting with a constant head pressure ranging from 12 bar to 15 bar.• Structural repair of the cutterhead in difficult hydrogeological conditions [water inflow of approx. 800 m3/hr (4,000 gpm)].• Complete repair of the cascade sealing system for the main bearing and two replacements of the pinion bearings.• The TBM approach to the intake structure."

Jan 1, 2015

By Nick Karl, David Wilburn

"The mission of the U.S. Geological Survey (USGS) National Minerals Information Center (NMIC) is to collect, analyze and disseminate information on the domestic and international supply of and demand for minerals and mineral materials essential to the U.S. economy and national security. Understanding mineral exploration activities and trends assists government policy makers, minerals industry decision makers and research entities in identifying where future sources of mineral supply are likely to be discovered, the amount and type of these resources and factors that may affect exploration and development.This review summarizes significant exploration trends related to active sites and budgets, mineral commodities and regional factors for the years 2001-2015. Data were compiled by specialists in the USGS-NMIC, and reported annually in the USGS-NMIC Minerals Yearbook series and in the May issue of Mining Engineering magazine. External data for these analyses were derived from industry sources, published literature, and SNL Metals & Mining, an offering of S&P Global Market Intelligence (New York, NY).The USGS-NMIC compiled exploration site data for more than 80 mineral commodities, focusing on base metals, diamond and precious metals. More than $138 billion constant U.S. dollars were budgeted by the minerals industry from 2001 through 2015 to explore more than 16,000 mineral deposits globally (SNL Metals & Mining, 2016a). Annual analyses identified where mineral exploration took place by principal commodity target, ranked the magnitude of activity in each region, identified the factors that most affected changes in exploration activity and highlighted developments that led to changes in global supply or increased diversity of supply to the United States. Geographic classifications noted in this report were Africa, Australia, Canada, China, Latin America, Pacific, Russia, United States and Rest of the World."

Apr 1, 2017

By Mingyang Li, Yan Lv, Xiaolong Ma, Xudong Gao, Jie Zhao, Yingyi Zhang

The reduction process of pre-oxidized ilmenite concentrate powder in 30%CO–70%N2 atmosphere was characterized by thermogravimetric and differential thermogravimetric (TG-DTG) analysis system at the temperature from 1073 to1223 K. The isothermal reduction results show that the reduction process is divided into three stages and the corresponding apparent activation energies are obtained by iso-conversional method and model-fitting method, respectively. For the first stage, the conversion degree increases sharply with increasing time, and the reduction process is controlled by the random nucleation and subsequent growth model (A2 model). For the second stage, the conversion degree increases slowly with increasing time, and the reduction process is controlled by the diffusion of carbon monoxide in the reduced layer (D1 model). For the third stage, the reduction processes at different temperatures are controlled by the diffusion of carbon monoxide in the reduced layer (1073 K and D1 model), phase boundary chemical reaction (1123 K and R2 model), random nucleation and subsequent growth (1173 to 1223 K, A2, and A3 models), respectively. For the whole reduction process, the apparent activation energies obtained by iso-conversional method and model-fitting method are 71.72 and 31.92 kJ mol−1 , respectively

By Mingyang Li, Yan Lv, Xiaolong Ma, Xudong Gao, Jie Zhao, Yingyi Zhang

The reduction process of pre-oxidized ilmenite concentrate powder in 30%CO–70%N2 atmosphere was characterized by thermogravimetric and differential thermogravimetric (TG-DTG) analysis system at the temperature from 1073 to1223 K. The isothermal reduction results show that the reduction process is divided into three stages and the corresponding apparent activation energies are obtained by iso-conversional method and model-fitting method, respectively. For the first stage, the conversion degree increases sharply with increasing time, and the reduction process is controlled by the random nucleation and subsequent growth model (A2 model). For the second stage, the conversion degree increases slowly with increasing time, and the reduction process is controlled by the diffusion of carbon monoxide in the reduced layer (D1 model). For the third stage, the reduction processes at different temperatures are controlled by the diffusion of carbon monoxide in the reduced layer (1073 K and D1 model), phase boundary chemical reaction (1123 K and R2 model), random nucleation and subsequent growth (1173 to 1223 K, A2, and A3 models), respectively. For the whole reduction process, the apparent activation energies obtained by iso-conversional method and model-fitting method are 71.72 and 31.92 kJ mol−1 , respectively

By Vinícius Resende Domingues, André Pacheco de Assis, Bernardo Cascão Pires e Albuquerque

"The increasing demand for underground works in urban centers, and in particular the need to build undercrossing tunnels, requires constant evolution in building techniques in order to achieve success and safety. In the case of Brasilia, capital of Brazil, in order to preserve an important avenue (Eixo Monumental), where are located many historical monuments, the construction of a tunnel was envisioned as an option to interconnect the National Stadium (on one side of the avenue) to the Convention Center Ulysses Guimarães (on the other side). The excavation design is comprised of a coverage smaller than one diameter, height of 7.5 m, width of 9.0 m and length of 25 m. In order to enable a negligible influence on the avenue’s usage, the structure is designed as a portico system composed of pipe canopy. In this context, this study presents the portico analytical solution computed with the aid of the software Mathematica and a numerical solution using the software ABAQUS. INTRODUCTION Undercrossing tunnels are increasingly common in urban centers as alternative roads or as access to underground works of large dimensions (stations and parking lots). The geomechanical conditions of the soil mass, not always favorable, and the low distance between tunnel’s ceiling and the surface require intense treatment of the soil massif and execution of a rigid support system. The importance of the road just above the undercrossing tunnel emphasizes the need for a highly competent monitoring system because existing structures require minimum allowable displacement and do not allow the interruption of traffic. The soils that are excavated for the construction of undercrossing tunnels are composed, in most cases, of layers of fill and / or soft soil or weak rock, showing stability problems when subjected to tunneling operations. The combination of low coverage and week ground is solved by soil improvement techniques and strengthening of the excavated cross-section with further advance with the so-called New Austrian Tunneling Method (NATM). Another option is to build structural frames that support the surface. In this research, and based on the context of a case study, we propose the study of the construction technique comprising a portico structure composed of pipe canopy. For this paper, the technical standards used are the Brazilian ones as the case study refers to this country."

Jan 1, 2016