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By Gerald Pinter, David Nitsche, Márton Bredács, Markus Haager, Andreas Frank

"The reliable prediction of service lifetime of tunnel constructions is of essential technical and economic interest. Polymers used for tunnel liners have to fulfill the requirement of 100 years lifetime. However, today no reliably proven test method is available which confirms such long lifetimes. The current paper introduces a recently started research project which focuses on lifetime prediction of highly flexible, very low density polyethylene (VLDPE) for tunnel geomembranes. Different PE grades in combination with different antioxidant packages are conditioned at elevated temperatures and immersed in different media. Initial results confirmed significant material aging of unstabilized resins already after exposure of up to 34 weeks, at least at the highest exposure temperature of 80 °C. To consider application relevant material properties the material characterization was done by means of tensile tests and dynamic oxidation induction temperature tests. High pressure liquid chromatography was used for further investigation of antioxidant consumption kinetics. 1. INTRODUCTION For a reliable service of modern tunnel constructions a sustainable proofing against water infiltration is essential for the lifetime of the structure. Geomembranes made of polymeric materials have been used successfully for tunnel lining since several decades. Whereas previous geomembranes usually were made of plasticized polyvinylchloride (PVC-P), due to several technical advantages today very low density polyethylene (VLDPE) has become a more and more popular material for such applications. For modern geomembranes, current guidelines expect minimum lifetimes of at least 100 years (ÖBV-Richtlinie 2012). In contrast to this requirement it must be considered that today no test methodology is available which reliably confirms such long lifetimes of polymeric materials."

Jan 1, 2016

By J. Scheepers, P. Smith, G. (Yunfei) Qiao

High pressure acid leach (HPAL) and pressure oxidation (POx) or pressure leaching extraction processes occur in autoclave vessels operating at elevated temperature and pressure, acidic conditions with abrasive mineral slurries. The harsh process conditions require specialized severe service metal seated ball valves to support operation of the vessels. Over several decades thermally sprayed titanium dioxide (TiO2) and chrome oxide (Cr2O3) coatings have been applied to extend the service life of the ball valves and other high wear critical components. Variability in the coating application quality control and severe process conditions can result in spalling, coating failure and premature failure of the component resulting is decreased autoclave circuit availability. In 2012 MOGAS, together with BRENCO, initiated research and development for ML-381, metallurgically bonded coating. This paper includes the historical development of severe service ball valve coatings, success of the trials and increasing industry adoption of the ML-381 coating for ball valves and other critical autoclave circuit components.

Mar 2, 2022

By MATTHEW HART, THOMAS BAMFORD, Kamran Esmaeili, MICHAL KOWALCZYK, FILIP MEDINAC

Improved haul road conditions can positively impact mine operations resulting in increased safety, productivity gains, increased tire life, and lower maintenance costs. For these reasons, a monitoring program is required to ensure the operational efficiency of the haul roads. Currently, at Bald Mountain mine, monthly site severity studies, ad hoc inspections by frontline supervisors, or operator feedback reporting is used to assess road conditions. These methods are subjective and provide low temporal resolution data. This case study presents novel unmanned aerial vehicle (UAV) technologies, applied on a critical section of haul road at Bald Mountain, to showcase the potential for monitoring haul roads. The results show that orthophotos and digital elevation models can be used to assess the road smoothness condition and to check the road design compliance. Moreover, the aerial mapping allows detection of surface water, rock spillage, and potholes on the road that can be quickly repaired/removed by the dedicated road maintenance team.

Sep 15, 2020

By Y. Luo

Based on the concept of slope stability analysis, a formula for determining an important parameter required in the mathematical model for the prediction of mining subsidence in hilly terrain has been proposed. The slope geometry and soil physical and mechanical properties of the surface natural slope can all be considered in the formula. Incorporation of this new formula into an existing mathematical model provides an integrated approach in studying ground movement in hilly regions.

Jan 1, 1998

By Helmut Westermayr, Michael Tergl

DESCRIPTION OF PROJECT Geographic Setting The Kops II plant is a pumped storage scheme of the hydroelectric power producer ‘Vorarlberger Illwerke AG’ which is currently under construction in the Austrian Province of Vorarlberg. The plant is located at the end of the Montafon valley and will be fed with water coming from the Silvretta mountain range (Figure 1) Description of Plant The Kops II plant shall be operated as a pumped storage plant with three highly flexible and quickly controllable power generating units. Each unit shall have a capacity of 150 MW and shall be equipped for both turbine operation and pump operation. The Kops II plant uses the existing Kops Lake as upper storage reservoir and the existing Rifa balancing reservoir as lower storage reservoir. All major plant components of the Kops II scheme are located below ground. Total investment costs areapprox. 360 million Euro. Construction Lots The construction works for the Kops II plant, which were subdivided into three lots, were launched in September 2004. It is planned that the first power generating unit shall go on line in the year 2007. The completion of the overall project and the operation start-up of the second and third unit are envisaged for the year 2008. Lot 1—Pressure Tunnel. The 5.5-km-long pressure tunnel forms the connection between the Kops Lake and the beginning of the pressure shaft. The tunnel was excavated by the use of a double-shield TBM. Lot 2—Pressure Shaft and Surge Chamber. The approx. 1.1-km-long pressure shaft was excavated by TBM, advancing from bottom to top. Featuring an inclination of80%, the pressure shaft overcomes a difference in height of approx. 700 m. Lot 3—Power House Cavern and Tailrace Structure. The power house cavern, which is being built approx. 150 m inside the mountain, forms the core of this plant. The power house is designed to accommodate three power generating units, and the transformer cavern is forseen to accommodate three transformer units. The tailrace structure serves the purpose of conveying the water to the lower storage reservoir during turbine operation and as water intake during pump operation (Figure 2).

Jan 1, 2007

By Erich J. Jacob, Volker O. Meldner

INTRODUCTION Our company has made persistent efforts to utilize the very latest cost-saving technology in tunnel design and construction. However, we were relatively late in joining the clan of slurry shield tunnelers. The challenge came in 1973, when our company was low bidder on a major sewer tunnel in Hamburg, West Germany. The tunnel was to be driven under the harbor region through coarse and fine sands with up to 60 ft hydrostatic head of water. Outer diameter was 15 ft, and length was 2.9 miles. This contract appeared right to enter the new field of slurry face tunneling. We gathered a design-engineering team to develop the machine, called it "Hydroshield", and used it on the project. The good performance of the prototype machine encouraged us to improve and modify the equipment design. The very latest model is now in use on a subway tunnel in Antwerp, Belgium. This tunnel is 21 ft outer diameter and 2.4 miles in total length. In terms of excavated volume it is the world's largest slurry shield contract. While the drive is still in full swing, we are currently preparing for 3 further Hydroshield applications, with diameters ranging from 12 to 32 ft. This paper describes the Hydroshield's salient design features, operational characteristics, construction reliability and performance levels, as experienced in West Germany and Belgium.

Jan 1, 1979

By Douglas B. Silver

"Editor’s note: Douglas B. Silver, Portfolio Manager, Orion Resource Partners, was the keynote speaker at the 2017 SME Annual Conference & Expo in Denver, CO on Feb. 19, 2017. He also gave the keynote address to the SME Annual Conference in 2008. The following is his 2017 keynote address with a few of the slides that were presented. The full speech is available on YouTube https://www.youtube. com/watch?v=uF0qwGJIX3UIn 2008, I had the privilege of giving SME’s keynote address. At that time the financial markets were on the verge of collapse and my presentation described the issues. Unfortunately I was correct, and global markets went into a steep nosedive, creating the largest economic downturn since the Great Depression.In hindsight, there were plenty of signs that this was coming. The Supercycle had created massive new wealth. This wealth was largely invested in the United States due to the country’s political stability and credit worthiness. In 2004, the large investment banks convinced the U.S. Securities Exchange Commission (SEC) to allow them to triple their borrowing leverage ratios. This made the banks more vulnerable to market volatility. The banks then lent money to NINJAS - people with no income, no job and no assets. Even worse was the fact that these unqualified home owners used adjusted-rate mortgages (ARMs) which they, of course, intended to refinance prior to interest rates rising. These mortgages were then bundled up by the banks and sold to investors as “safe” investment products. The money flowed into these products because the rating agencies gave these instruments high marks. These same agencies earned their fees from the very same banks seeking high ratings. (No conflict there). Private debt exploded and peaked out in 2008.These mortgage products were sold in an unregulated shadow banking system and the ARMs came due. Toxic mortgage default rates skyrocketed and the mortgage-backed securities collapsed in value. This house of cards had a negative feedback loop that accelerated the market crash and resulted in more than $1.5 trillion being lost in the securitization sector, a 47 percent decline in the Dow Jones Industrial Average, foreclosure rates skyrocketing and housing prices collapsing. The financial markets were in a nosedive."

Jan 8, 2017

By R. Wu, R. Howell, J. Dase

Turquoise Ridge is an underground gold mine located in the Potosi Mining District, approximately 64 km northeast of Winnemucca, Nevada. Turquoise Ridge Underground is accessed via two shafts and a system of internal ramps and utilizes underhand drift and fill mining methods with cemented rockfill. The mine also employs mechanical mining as well as sill benching as mining methods. Ground conditions at Turquoise Ridge Underground are poor, and the Rock Mass Rating (RMR) may be less than 20, or very poor, in ore headings. Current production rate is 2,700 tonnes of ore per day. Key challenges in increasing production levels and reducing costs are the development of sufficient stoping areas and the transition from top-cut development to undercut stoping. Completion of the infrastructure development in the North Zone is necessary to achieve and optimize higher production levels. The #3 Shaft project is well underway and is expected to be commissioned in mid. 2022. The shaft will drastically decrease the haulage requirements in the North Zone

Mar 2, 2022

By D. Hongjun

In this paper, the flotation rule and behaviors of kyanite-group polymerphous minerals were studied in modified Hallimond tube in detail. Furthermore, the energy change of collector/mineral systems before and after adsorption and the net charge densities of the atoms on the minerals surfaces were calculated by use of quantum chemistry. The flotabilities in minerals were successfully explained.

Jan 1, 1995

By Christopher Newman, Andrew Minckley

With underground stone operations developing in deeper and more geologically complex conditions, accurate pillar stability analysis becomes for the evaluation of engineering design. This paper provides engineering-based recommendations for applying LaModel to evaluate multiple-level room-and-pillar stone mines in both shallow and deep cover. It provides practical guidance on model calibration using field observations, selection of input parameters, and interpretation of results to inform design and operational decisions. The analysis demonstrates LaModel’s effectiveness in simulating pillar load transfer, stress redistribution, and failure mechanisms in complex mining geometries where empirical methods may be inadequate.

Feb 22, 2026

By Howard V. Sears

Prospecting in its modern context means simply the gathering of information on which, to base plans for the utilization of our mineral resources. One prospecting system familiar to T. V. viewers is the pan of the old gold prospector which, while he prospected, could produce the wealth which financed him in his search. Present day geophysical "prospecting" systems, which are based on the real or supposed responses of an ore specimen, to various stimuli finder controlled laboratory conditions, are promoted as means of reducing the cost of prospecting. The universal drawback to all geophysical systems is that they yield "soft" data which are only presumed to be analogous to ore mineralization until they can be calibrated, by conventional prospecting systems, to each actual mineral environment being tested. By this time the system usually is no longer cheap. Since the raw data are too esoteric to be used until interpreted by geophysicists, usually in the light of their own personal theories and experience, the certainty of multiple interpretation is introduced. The concept of prospecting, at St. Joe Minerals Corporation's Viburnum, Fletcher and Brushy Creek mines in the new Missouri Lead Belt, encompasses surface diamond drilling for preliminary exploration, the sub¬sequent development of ore body tonnages and grades and the establishment of mining parameters. The predominantly flat-lying mineralized formation is mined by room and pillar stoping. In an operating mine, jackhammer holer are drilled in backs and bottoms of stopes, and chip samples are taken for assay, concurrent with mining. Thus irregularities in ore bodies or nearby discontinuities are not overlooked which are above or below the general mine

Jan 1, 1971

By M. Sadegh Safarzadeh, Erich U. Petersen, Jan D. Miller

"An acid bake-leach process has been identified and applied to an enargite concentrate containing ~67% enargite, ~27% pyrite (FeS2), ~3% chalcopyrite (CuFeS2), ~6% sphalerite (ZnS) and <1% galena (PbS). Sulfuric acid baking of this concentrate resulted in the transformation of the concentrate to S8, As2O3, HFe(SO4)2•4H2O, PbSO4 and Cu0.47Fe0.53SO4•H2O, all of which (except elemental sulfur and PbSO4) dissolved during the water leaching step. More than 87% Cu and 64% As were leached when the concentrate was baked at 200°C over 7 hours with a sulfuric acid-toconcentrate weight ratio of 1.6. Less than 1% As was lost to the gas phase. Upon water leaching, copper and arsenic were released to the solution at a concentration ratio of about 3:1. While enargite is very reactive during the sulfuric acid baking reaction, other minerals present in the concentrate such as pyrite, galena and sphalerite may compete to consume sulfuric acid and be converted into their corresponding sulfates at different concentrations. The purpose of this paper is to present our examination of the effects of sulfuric acid dosage on the extractions of Cu, Fe, and As from an enargite concentrate. In this regard, the concentrate, baked concentrate, and the leach residues are characterized and a conceptual process flowsheet is described for the acid bake-leach process for the treatment of enargite concentrates.IntroductionThe occurrence of enargite (Cu3AsS4) in copper ores and concentrates and the associated high arsenic values in such resources have resulted in a considerable decrease in the demand for such concentrates because they cannot be economically processed using conventional technologies such as smelting and atmospheric leaching (Mihajlovic et al., 2011). The exploitation of such problematic deposits through competitive treatment strategies will be required in the near future in order to satisfy increasing pressure from the copper market. It is expected that the average arsenic grade of copper concentrates will increase from 0.17% in 2008 to 0.22% by 2020 (Mayhew et al., 2011).The acid bake-leach process was identified and selected for further investigation at the University of Utah as a possible process alternative for the treatment of enargite concentrates. In this case, adequate amounts of concentrated sulfuric acid are mixed with the concentrate and heated to the temperature range 150-300°C. Subsequently, the baked material is leached with water/weak acid and the acid bake-leach process has some advantages over conventional sulfuric acid leaching (Prater et al., 1970). During water leaching, metal sulfates are released in solution, after which they can be extracted through well-known hydrometallurgical techniques. While the majority of the work has been done on oxide minerals, there is a limited record of sulfuric acid baking of sulfides."

Jan 1, 2015

By H. L. Holden

The single line grinding circuit at Bond Gold&apos;s Colosseum mine consists of variable speed drive semi-autogenous (SAG) milling and secondary grinding with a fixed speed ball mill. There are several advantages and disadvantages of operating SAG mills with variable speed drives. Discussion in this paper will focus on the effects of variable speed SAG milling in relation to mill liner wear, grinding media consumption, and mill operating availability. Operating experiences, corresponding mill data, and pertinent design changes are also presented.

Jan 1, 1991

By E. Tarshizi

This research project demonstrates the application of a mine system simulation and animation model in enhancing the efficiency of a truck-shovel operation and reducing the haulage environmental impact in an open-cut coal mine. In any mine, a key objective is to have enough equipment for production and not have excess to where it is counterproductive. Due to the advent of responsible mining, environmental regulations, and eco-friendly practices, these factors must also be considered in the analysis. The over-trucked situation at a mine will be discussed, i.e. when the number of trucks exceeds the optimum number of trucks a mine should have for the most productive/profitable mining operation. When the system has an excess number of trucks, truck utilization is reduced which impacts mine operation, capital costs and the environment, through unnecessary truck purchase, energy use, air pollution etc. A hypothetical surface coal mine layout was used for the simulation model.

Feb 23, 2014

By Howard J. Haselhuhn

The effectiveness of selective flocculation and dispersion processes for the concentration of hematite ore are strongly dependent on the ionic content of the process water. It has been noticed that magnesium ions are more detrimental to iron recoveries during gravity separation and flotation processes than calcium. This phenomenon was studied by measuring the zeta potential of hematite ore at various concentrations of sodium, magnesium, calcium, strontium and barium at a pH of 11. Results show that zeta potential inverts from negative to positive at concentrations as low as 0.16 mM of magnesium ions in the solution. It takes a significantly higher concentration (1.25 mM) of calcium ions to achieve the same effect. This difference is attributed to the ability of magnesium ions to adsorb to all surface hydroxyl groups, whereas calcium, due to its larger size, can only adsorb to every third hydroxyl group. This hypothesis was confirmed by results similar to those seen with calcium when this test was repeated with strontium and barium ions. The tendency for calcium ions to adsorb to every third surface hydroxyl group causes higher concentrations of calcium to be less detrimental to hematite concentration processes than magnesium.

May 1, 2012

By W. C. Brice

Minnesota&apos;s mineral resources are widespread and diverse (Figure 1). In addition to the nation&apos;s largest iron and manganese reserves, the state contains sizeable vanadium, copper, and nickel resources. Recently it has been determined that the proterozoic unconformities in Minnesota have a favorable potential for uranium deposits. Finally, major potential exists in Minnesota&apos;s archean greenstone belts for gold, silver, and copper-zinc massive sulfides. Many of the state&apos;s mineral resources have been found in environmentally sensitive areas. This is not surprising since the natural forces associated with the formation of mineral deposits are often the same processes that create unusual landforms. For example, much of the state&apos;s copper-nickel is found within and adjoining the Boundary Waters Canoe Area (BWCA) and Lake Superior. The history of mineral development on the Mesabi Iron Range has also created culturally sensitive areas. Early iron mining development required the workers to live close to their jobs, and mine wastes were dumped as near the mine as possible. Few, if any, foresaw the time when taconite would be economic to mine. Therefore, it is not unusual to find valuable taconite resources located under towns and waste dumps on the Mesabi Iron Range.

Jan 1, 1980

By Nikhil Dhawan, Shrey Agrawal, Ashwini Kumar

The current study investigates sericite clay as an alternative source of potash and alumina. The alumina and potash content in the sericite is approximately 35 and 10%, respectively, compared with 50–55% in bauxite ore. Muscovite and illite phases are stable, and direct leaching is found to be ineffective. Here, planetary ball milling was performed, which provided dissociation of stable phases to relatively reactive phases. The milling led to a five-fold increase in the surface area, resulting in enhanced leaching kinetics even at low acid concentration. The statistical design obtained optimal conditions of 8 h of milling followed by leaching in 1.73 M HCl at 75 °C, yielding 82% alumina extraction in precipitate with 85% purity in γ-alumina form and 63% potassium dissolution in sylvinite phase. The yield of the precipitate was ~65–68%, and the acid leach residue contained primarily silica.

By P. Dhar, H. R. Kota, M. Thornhill

A very high-grade calcite deposit located in northern Norway consists of CaCO3 ore with minor silicate and sulphide impurities. Cationic (Tallow-1,3-diaminopropane, Duomeen T) collector has been used in the purification of calcite by flotation with an aim of achieving calcite concentrate for its use in value-added products in a variety of industries. The feasibility of sulphide flotation from calcite by this cationic collector has been initially judged from Hallimond flotation and zeta potential on pure mineral systems and the results illustrate the removal of sulphide from calcite ore at neutral pH region. The adsorption mechanism of diamine on both the sulphide minerals was found to be the same by zeta potential studies. The variations in zeta potential are in good agreement with the adsorption of diamine molecular and ionic species as a function of pH. FTIR studies also showed the adsorption of diamine species in agreement with the zeta potential and Hallimond flotation results. Furthermore, the removal of sulphide impurities with selective flotation by diamine collector was performed in bench-scale flotation with the calcite ore and the results indeed showed that the calcite concentrate could meet the quality requirements for its use in the paper industry for coating and filler purposes.

By Satoshi Honda, Mitsuru Shimizu, Tatsuji Nagao, Motoaki Kurisu, Hirokazu Izumi, Toshinori Takahashi, Hiroyuki Itoi

"1. INTRODUCTION Grade separation of roads and railway tracks is an effective method for solving traffic-related issues in cities. However, in urban areas where the existing traffic infrastructure is already overcrowded, construction of new roads often faces problems especially in the proximity of existing structures. This paper summarizes the construction plan and results of new road tunnel construction in the proximity of the piers of elevated tracks on the Tokaido Shinkansen railway.2. SUMMARY OF CONSTRUCTION AND ISSUES Auxiliary Route No. 26 as specified in the Tokyo urban plan is a project by the Tokyo Metropolitan Government, covering the construction of a new road with a total length of 22.3 km currently on the way to completion. In Shinagawa Ward, Tokyo, Auxiliary Route No. 26 is designed to cross the railway tracks of the Yokosuka Line and the Tokaido Shinkansen Line, so for this project, the East Japan Railway Company (JR East) was commissioned to design and build a road crossing under the railway tracks (Sumiyoshi Underpass). Figures 1 through 3 show a sketch of the Sumiyoshi Underpass. The Sumiyoshi Underpass was planned as a two-lane tunnel for vehicles, which was to cross under the railway tracks of the Yokosuka Line and the Tokaido Shinkansen Line at an angle of 70 degrees. The structure concerned is a single-story single-span box culvert structure with the following dimensions: 11.5 m wide, 7.7 m high and 31.6 m long. The Tokaido Shinkansen Line tracks were constructed on a girder-type elevated bridge built in the 1960s, and the foundation piles of the piers (P7 and P8) in the proximity of this crossing box culvert of RC structure were constructed using an earth drill method. The crossing structure for this project is located extremely close to the piers of the Tokaido Shinkansen railway tracks, with a minimal separation of 0.4 m, and the most significant issue of this project was construction in a manner that would not obstruct the normal operations of the Tokaido Shinkansen (Figure 4). Initially, we considered installing a temporary earth retaining structure in the proximity of the piers, cutting the ground and building an RC box, but concluded that it would be very difficult to apply this method because of probable excessive displacements in the Shinkansen railway piers. That is why we decided on the use of a non-open cut method in order to minimize the impact on the piers."

Jan 1, 2016

By A. M. Anthony, A. Y. Atta, S. S. Magaji, U. Abubakar-Zaria

There are two major gold recovery methods: the hydrometallurgical technique, which employs cyanide solutions, and amalgamation method, which involves mercury (Hg). These methods present considerable health, safety, and environmental concerns. Past applications of alpha-cyclodextrin (α-CD) on gold scraps show that α-CD is not only inexpensive, but is also environmentally friendly. This research work used α-CD to recover gold from gold ores instead of gold scraps. The gold ore was sourced from Shanono gold deposit site Kano State,Nigeria. The gold ore was characterized by fire assay (FA) for the precious metal. The concentrate was digested with aqua regia (AR) for 24 h. Modified AR, where hydrochloric acid was replaced with hydrobromic acid, was used for the gold digestion due to the good match in molecular recognition between gold bromide ion (AuBr)− and α- CD in a second sphere coordination complex. The digestate was characterized using atomic absorption spectroscopy (AAS). Gold recovery using this technique is pH sensitive, and five pH values (2.0, 3.6, 4.0, 5.4, and 6.0) were investigated. FA analysis showed the Shanono gold ore deposit contains an average of 4.71 ppm of gold, AAS analysis showed highest gold recovery of 69% at pH 4.0, which is lower than recoveries from the metal scraps. This could be due to the presence of other gangue minerals closely associated with the ore. However, gold recovery using α-CD on Shanono gold ore has shown to have a higher yield of 69% compared to 35.5% yield obtainable by Artisan Small Scale Miners using mercury.

May 5, 2020