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By R. Riding

Degussa Corporation's peroxide-assisted leaching (PAL) process was evaluated in the batch concentrate leach circuit at Hecla Mining Company's Republic Unit. The product leached in this batch circuit is a high grade gold-silver sulfide (predominately pyrite) flotation concentrate. The primary objectives of the test program were to determine the effects of dilute hydrogen peroxide addition on leaching kinetics, sodium cyanide consumption and precious metals recovery. The results of the testing demonstrated that using dilute hydrogen peroxide produced the following benefits: - 1. Batch leach time requirements decreased by 80%. - 2. Sodium cyanide consumption in concentrate leach reduced by 55%, which translated to an overall plant reduction of 20%. - 3. In the concentrate leach process, gold recovery was increased by 1 to 2%. Because of the excellent metallurgical results achieved with the use of dilute hydrogen peroxide, as well as an economic incentive, PAL has become standard practice in the concentrate leach circuit operation. A complete description of the Republic PAL plant evaluation and performance is provided in this paper. In addition, process chemistry considerations in regard to the role of hydrogen peroxide are discussed.

Jan 1, 1992

By Brandon Barnes, Michael Haggerty

"Around Minneapolis and Saint Paul, Minnesota, the local geology includes the St. Peter Sandstone, which is easily minable and has facilitated construction of interceptor tunnels for storm water and sanitary tunnels since the 1800s. The elevation of the geologic units allowed gravity-driven flows from the downtown areas all the way to the Mississippi River. Through many years of service, some of these tunnels have experienced degradation and require maintenance. Additionally, increased stormwater surface runoff can result in internal pressurization of the tunnels, accelerating degradation. Because structural failure or collapse of any of these interceptor tunnels would create a significant repair challenge, the city of Minneapolis has been inspecting and designating tunnels in its system for periodic review and repair. One of these, the St. Mary’s/Hiawatha tunnel, was rehabilitated using a grouting program. A hydrologic model was also used to improve understanding of pressurization events during some storms, leading to construction of a near-surface pressure dissipation chamber to provide increased hydraulic capacity. BACKGROUND The St. Mary’s/Hiawatha tunnel in Minneapolis has three segments; the first two were constructed in 1942 and the third was added in 1987 (Figure 1). Segment 1 is approximately 4,700 feet in length and outlets to the Mississippi River. Segment 2 intersects Segment 1 approximately 3,500 feet upstream of the river outlet and continues for approximately 2,500 feet in a southeasterly direction. The third and newest segment is approximately 500 feet long. There are four different cross sections of tunnel along the entire system.Originally, tunnel construction often consisted of mining the St. Peter sandstone with a pressurized water lance and constructing wood lagging support (Payne, 1967). An underdrain was generally installed below the invert during construction; this resulted in localized dewatering and provided groundwater control during construction. Non-reinforced concrete liner sections were cast in place. Often void space existed between the tunnel liner and the native sandstone bedrock. These voids, particularly in the crown, prevent direct contact between the liner and the bedrock."

Jan 1, 2016

By Narendra N. Khatri, Michael Deutscher, Jozef F. Zurawski

Five sewer connections were required to divert Combined Sewer Overflow (CSO)from existing outfalls to an old underutilized large diameter brick sewer (the Easterly Interceptor). The connections were part of an on-going CSO control program by the Northeast Ohio Regional Sewer District (NEORSD) in the City of Cleveland, Ohio. Each connection was made by pipejacking and hand-mining a fiberglass-reinforced polymer (FRP) pipe through soft glaciolacustrine clays and silts. Jet grouting was utilized to stabilize the soils and fill the voids surrounding the interceptor prior to making the underground connection. Reinforced concrete liners were constructed inside the aging brick sewer to provide structural stability during ground improvements and connection work. The project also involved micro tunneling two approximately400 foot lengths of FRP pipe through soft ground using a slurry pressure balanced machine.

Jan 1, 2005

By Werner Burger

The last decade has witnessed a rapid development and application of slurry and EPB type tunnel boring machines. Both soft ground types are able to excavate tunnels in unstable ground conditions below the water table with positive face support. The most significant component of the excavation process is the cutterhead and tool con-figuration were the excavation and face support meets the geological challenge. The TBM downstream processes cannot take place unless the cutterhead and tools effectively do their job. This paper will review the current state of the art design for both slurry and EPB cutterheads and highlight both common as well as geological specific design features.

Jan 1, 2007

By F. W. DeVries, O. B. Mathre

Addition of Kastone® peroxygen compound and formaldehyde to cyanide gold extraction process effluents, containing at least 5 mg soluble copper per liter, will oxidize acid-dissociable cyanide to levels less than 0.2 mg per liter, without appreciable oxidation of thiocyanate. Most of the copper precipitates and is removed by filtration of the treated solutions. The treatment can be completed in less than 2 hours when the excess of hydrogen peroxide over the cyanide is about 75-100 mg per liter. The excess hydrogen peroxide destroys residual formaldehyde and then is catalytically decomposed by the copper-containing solids that separate, so it will not interfere with subsequent operation. A pilot plant using this technology has been operated for more than four months at rates from 1-2 gpm. Clear, filtered effluent containing less than 0.2 mg acid-dissociable cyanide per liter has been produced.

Jan 1, 1981

By G. T. Lineberry

Horsepower requirement is recognized as a most important equipment characteristic. Other critical equipment characteristics will be isolated and analyzed by traditional operations research techniques, using off-highway trucks as an archetype. A computer search technique has been developed, employing various production and cost analyses. With this model, the optimum combination of horsepower, capacity, and velocity can be found, minimizing handling cost per ton. An example of the program's use and interpretation of its results will conclude the paper.

Jan 1, 1984

By N. F. Sather

Results of comprehensive trace element analyses of samples of Illinois #5 and #6 seam coals and the unquenched ashes obtained from gasification of these coals in a Lurgi reactor are reported and discussed. Areas where additional background information is needed for assessment of the environmental impact of trace element emissions from coal gasification are identified.

Jan 1, 1976

By Martin Langenderfer, Catherine Johnson, Alexander Douglas

Mine haul roads degrade rapidly due to extreme loads on suboptimal construction materials. Unmanned aerial vehicles (UAV) are suited to quantify large-area road-network conditions, such as surface roughness, defects and grade to optimize remediation of poor conditions and reduce overall costs. Mine haul roads present unique challenges, such as material type and edge characteristics, to automatic road detection that often fails, requiring manual road input. This research work proposes a new method using the road center determined by the principal curve of a haul truck’s path. Analysis grids were created from this center line. A dense point cloud from UAV photogrammetry was generated and multiple linear regression analysis was conducted on each individual grid. The root-mean-square error in each grid indicates the surface roughness, and the change of slope between grids indicates the road grade inconsistencies. This method was applied to 26 road sections, and the results were validated by images taken from the truck operator’s vantage point. Critical defects were identified including excessive pothole formation, corrugation, depressions retaining water, and narrowing of travel lane. The results demonstrate this is a valid method of road identification and quantification of road defects at a mine site.

Apr 1, 2024

By S. J. Schatzel, V. Gangrade

A ventilation research study was conducted by the National Institute for Occupational Safety and Health and a cooperating trona mine in the Green River basin of Wyoming, USA. The mine operation uses the longwall mining method in trona bed 17, a commonly mined unit in the region. The longwall face length is 228 m (750 ft), and caving on the face occurred up to the back of the longwall shields. The mine is ventilated using a main blowing fan and a bleeder shaft. For this study, sulfur hexafluoride (SF6) tracer gas was released in two separate monitoring experiments. For the first experiment, tracer gas was released on the face, this test focused on airflow along the longwall face of the active panel. Face test showed the airflow patterns to be more complex than just head-to-tail flow in the main ventilation air stream on the active panel. For the second experiment, tracer gas was released 2 crosscuts inby the face on the headgate side, this test focused on gas transport in the mined-out portion of the same active panel. Gob test showed a pathway of movement through the front of the active panel gob that moved outby from the tailgate corner. The primary pathway of tracer gas movement in the active panel gob was towards the headgate and tailgate bleeders and out of a bleeder shaft. The rate of movement towards the back of the gob was measured to be 0.19 m/s (37 fpm).

By F. L. Pirkle

A heavy-mineral deposit about 1.6 kilometers (I mile) in length and averaging about three meters (10 feet) in thickness is exposed approximately130 kilometers (80 miles) east of Denver, along Interstate 70, in Elbert County, Colorado near the town of Limon. The deposit is exposed in a geomorphic feature known locally as Titanium Ridge. The dominant heavy minerals, accounting for about 70% of the total heavy mineral suite by weight, are ilmenite, garnet, and zircon. The mineralized zone appears in a series of visually interpretable facies that are stacked vertically and represent subtidal, forebeach, backbeach, washover fan, and aeolian depositional environments. These paleoenvironments are analogous to depositional environments represented by a modern heavy-mineral bearing facies tract on St. Catherines Island, Georgia. Thus, Titanium Ridge provides evidence that heavy-mineral accumulation models for late Cenozoic deposits in the Georgia and Florida coastal plains are applicable to heavy-mineral deposits of the Western Interior subsurface and, by implication, the Western Interior Seaway, extending from Mexico to the Canadian Arctic.

Jan 1, 2011

By W. F. McDermott

The transportation of solids by pipeline is not new. In 1891 a United States patent broadly covering a method of pumping coal with water was granted to W. C. Andrews. His pilot plant was constructed on what is now the site of the New York Public Library in Manhattan. His process was applied to pumping coal mine waste back into the worked out portion of coal mines. On October 26, 1967, the world's first long distance iron ore slurry line was put into service by Savage River Mines. The commissioning of this 5.0 million dollar installation climaxed three years of development, testing, and construction and proved the Company's faith in pioneering this unique transportation method for iron ore. This paper will discuss some of the more pertinent items in connection with that three- year period. Also to be discussed will be the operation of this line during the past eleven months.

Jan 1, 1968

By Verya Nasri, Agustin Rey

Once completed, the Montreal Réseau Express Métropolitain (REM) will be the fourth largest automated transportation system in the world. The REM represents construction costs of approximately 7.0 billion Canadian dollars. The project consists of 67 km of twin tracks over four branches connected to downtown Montreal. The project includes 26 stations with 3 underground stations in downtown Montreal. One of the underground stations was built using the NATM method with thin permanent shotcrete initial and final liners separated by a sprayed on waterproofing membrane. The 2 other underground stations were built with the cut and cover approach including one using permanent secant pile wall with permanent walers and struts as the support of excavation and the final perimeter wall of the station. The project also includes the rehabilitation and enlargement of the Mont Royal Tunnel. This 100-year-old double track tunnel is about 5 km long. The REM also consists of 3.6 km new TBM tunnel connecting downtown to the Montreal International Airport through saturated soft ground and karstic rock. By the time of RETC, the construction of REM underground structures will be completed. This paper presents the design and construction aspects of the underground structures of this mega project.

Jun 13, 2023

By T. Burchett, F. Stanley, K. McGough, G. Luttrell

The vast majority of U.S. coal preparation plants utilize screen-bowl centrifuges to dewater their fine clean coal products. In light of this popularity, researchers at Virginia Tech have engaged in a variety of laboratory and industrial field test programs to develop technological enhancements that have the potential to further improve the performance of this important solid-liquid separation process. These enhancements, which include simple design modifications and new reagent packages, have been shown to significantly improve solids recovery and reduce product moisture in several experimental trials.

Jan 1, 2006

By Graham Davis

The future of the world's minerals industries is often painted as bleak. Peter Drucker has repeatedly proposed that the demand for minerals has become "uncoupled" from world economic growth.' This implies that, while mineral demand was in the past linked to the growing demand for and consumption of goods and services, further world development will not require substantial mineral inputs. Lester Thurow noted that for these reasons the US minerals industry is diminishing in scale and economic importance.2 There is some documented evidence of such uncoupling, and the demand for minerals may indeed diminish in the future. But such announcements are, to this point, no more than speculation. For instance, is it not just as likely that renewed environmental concerns will cause increased demand for the relatively innocuous environmental properties of metals, replacing plastics? And even if the prophesied demand decreases do occur, a sufficient fall in metal prices due to technological advances could increase the quantity of minerals demanded above current levels, in spite of leftward shifting demand curves. Thus, worldwide mineral production activity may increase or decrease in the future and no one can say whether more or fewer of the earth's citizens will become involved in the extraction and processing of minerals.

Jan 1, 1994

By Rudy Scarabelli, John R. Wagner

At one time explosives were the only economical means of rock tunnel excavation. Except in relatively long tunnels in the right rock explosives are still the cheapest means of rock excavation where they can be used. Today the most economical means of rock tunnel excavation is increasingly not the choice of the contractor. A good part of our work is for public agencies in urban areas and the public today is increasingly less tolerant of the disruption caused by our efforts. Owners in many cases have to direct their engineers to write specifications which severely restrict noise and vibration levels during construction. Sometimes specifications allow drill-and-shoot for starter tunnels only or even eliminate powder by fiat. Recent advances in the use of explosives such as sequential firing have made blasting more palatable to the public but are not enough in all situations. Thus the roadheaders on construction projects. In recent work I have seen the Alpine Miners, a Paurant Miner and the Robbins Mobile Miners used in several rock formations and now believe this type of equipment has a place in the tunnel constructor's choice of equipment. Rudy and I have not attempted to present a formula for choosing the best alternative excavation method in any given case because, of course, of the variables involved. We have simply tried to describe our experiences on a particular project and hope our observations will be of some value to tunnel constructors.

Jan 1, 1987

By Daniel Connor, O&apos

The Cal-Sag Relief Sewer is a 2.6 m (8 ft 6 in.) diameter 9.1 km (5.7 mile) rock tunnel bored in dolomite for the Metropolitan Sanitary District of Greater Chicago. Included in the project are 18 shafts varying in depth free 70 m (230 ft) to 41 m (135 ft). This paper discusses how Healy/Vanessa reduced costs by eliminating conventional hand excavation by hoisting muck from a high production Robbins TBM (Tunnel Boring Machine) through small diameter drilled shafts and using a trailing rail-utility backup system.

Jan 1, 1985

By T. W. Camm

Some of the defining characteristics of narcissists include a grandiose sense of self-importance, preoccupation with success and power, a sense of infallibility, and a supreme confidence in their ability and intelligence. Ironically, many of these characteristics are rewarded in business organizations, which may explain why there seems to be so many narcissists in management positions. Assuming we will be dealing with narcissists throughout our career, it makes sense for us to understand what makes them tick, and more importantly what we can do to work with them in a constructive manner.

Feb 23, 2014

By J. Villeneuve

Steady-state simulation has proved to be a very useful aid in designing new plants and optimizing existing ones. The algorithms and data definitions of existing simulators often, however, require a great deal of expertise for implementing a simulation-based methodology. The constraints imposed by conventional simulators are explained and the advantages of a new algorithm, the Objective-Driven Simulation, are shown. These advantages are a) an improvement in the simulation results, which enables simplifications of the methodologies used, and b) the possibility of taking into account economic objectives for plant operation, thus extending the range of application of steady-state simulation.

Jan 1, 1992

By Robert E. Murray

The title of my paper, "A Company's Response to Federal Coal Leasing," brings to mind a picture of a dog chasing its tail. This is what the coal industry, has been doing since the Federal coal leasing moratorium went into effect in 1971. We've gone around in many circles, but we are only very slowly, if at all, getting closer to catching our tails, i.e., efficient, economical, and rational Federal coal leasing. My companies, The North American Coal Corporation and its four Subsidiaries, The Falkirk and Western Plains Mining Companies and The Coteau and Missouri Valley Properties Companies, together hold in excess of 4.5 billion tons of lignite reserves in North Dakota. Some of our North Dakota properties are substantially interspersed with Federal coal, with the government holding title to the minerals in every other section. This checkerboard pattern of Federal ownership has made it difficult to develop and market some of our reserves, and, as a result, it has become imperative that we be familiar with and active in the Federal Coal Leasing Program.

Jan 1, 1982

By Gunjan R. Bhattarai, Kumar Bhattarai

Recently, there has been an enormous increase of interest in artificial intelligence (AI), machine learning (ML), and their applications by researchers, government agencies, and the underground construction industry. Ultimately, these tools have the potential to automate the design and construction processes and boost productivity, safety, quality, and operational stability. This paper presents ongoing research and applications of artificial neural networks (ANNs), robotics, and 3D technologies in ground characterization, tunnel ground support prediction, risk projection and reduction, and productivity enhancement in TBM operations. The paper further investigates potential uses of AI, robotics, and 3D technologies in the underground construction industry

Dec 1, 2022