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By Verya Nasri, Mehdi Bakhshi

"Fiber reinforcement has emerged as an alternative to steel bars in precast concrete segments due to advantages such as saving cost and reducing production time while developing a more robust product with improved handling and long-term durability. ACI recently drafted a new report as the first design guideline on FRC tunnel segments to provide specific guidance for this emerging technology. ACI document offers general information on the history of FRC precast segments from tunneling projects throughout the world; a procedure for structural analysis and design based on governing load cases, and a description of the material parameters, tests and analyses required to complete the design. This paper summarizes the design considerations in this ACI guideline prepared by the authors of this paper as the main contributors. Application of this guideline to design of a tunnel with an internal diameter of 5.5 m (18 ft) results in elimination of steel bars.INTRODUCTIONPrecast concrete segments are installed to support the tunnel excavation behind the Tunnel Boring Machine (TBM) in soft ground and weak rock applications. The TBM advances by thrusting off the completed rings of precast concrete segments that provide both the initial and final ground support as part of a one-pass lining system. These segments are typically designed to resist the permanent loads from the ground and groundwater as well as the temporary loads from production, transportation and construction. Tunnel segments are generally reinforced to resist the tensile stresses at both the Serviceability (SLS) and the Ultimate Limit States (ULS). With traditional rebar, a significant amount of labor is needed to assemble the cages and place the rebar, which results in higher production costs.Fiber Reinforced Concrete (FRC) can be used to enhance the production, handling, and placement of precast concrete segments. This is because of the uniform dispersion of fibers throughout the segment to include the concrete cover, which is very advantageous for resisting the bursting and spalling stresses. These stresses develop as a result of the high loads induced on the segments during the TBM jacking process. The presence of fiber in the concrete matrix helps mitigate against unintentional impact loads during segment handling and tunnel construction operations."

Jan 1, 2016

By L. Figueroa

Electrochemical methods have potential to treat waters impacted by mining, while simultaneously producing a recoverable metal product to off-set treatment costs. Mining-impacted waters may present challenges with electrochemical treatment due to low concentrations and complex solutions of numerous dissolved metals. This paper presents an evaluation of the potential strengths and limitations of abiotic electrowinning of mining-impacted waters. In particular the impacts of chemical composition on metals removal are evaluated. Results of bench-scale experiments demonstrate the potential to remove metals on the cathode (copper, cadmium, lead), as well as the anode (manganese). Pre-treatment for iron and aluminum may be needed and post-treatment pH adjustment would be necessary. INTRODUCTION Due to continually increasing demand for metals, new technologies and innovative applications of existing technologies are needed to recover metals from mining-impacted waters. Electrochemical methods have long been used for metallurgical processes with solutions containing high concentrations of the target metal. However, electrochemistry also has potential to treat waters with lower metal concentrations, while simultaneously producing a recoverable metal product to offset treatment costs. Electrochemical water treatment may have several benefits over traditional alkaline treatment for acid rock drainage (ARD). Sludge produced from alkaline treatment has high water content that is difficult to dewater, even for treatment plants producing a relatively high-density sludge. For example, the Argo Tunnel Water Treatment Facility (Argo Facility) in Idaho Springs, Colorado uses hydrated lime to produce a high-density sludge with a solids content of 20 to 25 percent and filter cake with solids content from 30 to 35 percent [1]. Furthermore, costs for managing the sludge are significant, approximately $90,000 per year for treating approximately 150 million gallons of water [1]. Although not the case for the Argo Facility, sludge produced from alkaline treatment of ARD has potential to be classified as hazardous. Disposal of sludge also opens up the potential for future liability depending on the sludge’s chemical stability and methods of disposal. In contrast to alkaline treatment, electrochemical treatment produces metals in elemental and other highly-dense forms on the cathode. If metals concentrations and flow rates are sufficiently high, the metals recovered may help offset overall treatment costs. In addition, sludge production would be reduced, if not eliminated altogether, thereby reducing both disposal costs and potential future liabilities as well.

Jan 1, 2019

By J. van der Walt

The Meikle Mine is located in the northeastern part of Nevada in the gold-rich Carlin Trend. First discovered in 1989, Meikle is being developed into a 2.2-kt/d (2,500-stpd) underground mine that will open during the second half of 1996. Work has already been completed on the mine’s cooling plant, a necessary item due to the high rock temperature and the hot ground water. In North American mines, there has been little need for refrigerated cooling. Therefore, Barrick needed to draw on experience from elsewhere in the world — particularly South Africa — to meet these requirements. The history of cooling mines using mechanical refrigeration dates back to the 1920s at Morro Velho in Brazil and 1936 at Ooregum in India (Dobson,1940 and Biccard, 1946). From 1940 to 1960, several cooling plants were installed on the deep level gold mines on the Witwatersrand in South Africa. These were followed by similar installations on the mines in the Klerksdorp, Welkom, Evander, Rustenburg and Thabazimbi areas. The first mine cooling plant in Germany was built during 1976.

Jan 1, 1996

By W. Z. Rogers

U.S. feldspar output sold or used in 2004 was estimated to be 790 kt (871,000 st), valued at $43 million free-on-board plant. This was below 2003 and about the same volume as 2002. The strong housing market in the United States maintained demand for ceramic tiles, plumbing fixtures, and fiberglass insulation requiring feldspar and shipments of glass containers increased by about 4 percent. Imports of ceramic tiles and plumbing fixtures continue to increase, taking the place of U.S. produced goods, and the feldspar required to make them. Output included flotation concentrates, feldspar content in feldspar-silica mixtures, potash feldspar and aplite.

Jan 1, 2005

By T. J. Lien

AMAX Coal Company's Belle Ayr coal dryer is the first industry attempt to commercialize sub-bituminous coal drying which has been the subject of laboratory and pilot plant tests for almost two decades. This paper presents the historical background, construction, start-up and operation of this adaption of fluidized bed coal drying technology to Powder River Basin coal. The flowsheet and operational problems encountered during plant start-up are discussed together with general material balance and product quality.

Jan 1, 1990

By Jack E. Bailey

From a start in 1957, milling 3,000 TPD of copper ore, the Cyprus Pima Mining Company, which is located 20 miles south of Tucson, has expanded its operations four times, and is currently treating over 55,000 TPD of ore.1 The most recent expansion added a 14,000 TPD semi-autogenous concentrator to the operation. Shortly after startup in January, 1972, the semi -autogenous plant exceeded the designed tonnage rate.2 Ore from the mine is delivered to a 54 inch gyratory crusher and is reduced to a minus 8 inch product. From the crusher the ore is stacked on a surge pile and then reclaimed and fed to the two parallel grinding circuits. A 28 ft. diameter by 12 ft. long semi-autogenous mill and a 16.5 ft. diameter by 19 ft. long ball mill make up each grinding circuit. The semi-autogenous mills are in closed circuit with screens and the ball mill circuits are closed with hydro- cyclones. Rougher flotation follows the grinding operation. Concentrate regrinding and cleaner flotation is performed in Mill I, the older mill. The generalized flowsheet is shown in Figure 1.

Jan 1, 1975

By Y. Okahara

The chlorination behaviors of pure iron and manganese oxides were investigated by combining a thermogravimetric analysis (TGA) technique with batch-boat roasting followed by leaching. Ferrous and manganeus oxides could be chlorinated readily, but, in the absence of a reductant, the higher oxides of both iron and manganese were difficult to chlorinate. Thermogravimetric analysis curves were drawn to illustrate the complexitites of the reactions, and the possible mechanisms were discussed. Then three manganiferous materials from the Cuyuna Range of Minnesota were treated by a process involving the selective chlorination of manganese followed by leaching. The results were interpreted in the light of the chlorination mechanisms observed on the pure iron and manganese oxides.

Jan 1, 1969

By R. Merkl

Since the 1940s, decanter centrifuges have become more important for increasingly complex solid-liquid or solid-liquid-liquid separation processes. Sometimes processed industrial or metalliferous minerals are abrasive or are treated with corrosive chemical agents. Traditional mining applications include the processing of coal, gravel and other products, where low-speed decanters, as well as screen bowl decanters and filters, dominate. These have been increasingly replaced by high-speed decanters during the last decade. Decanter centrifuges also started to play a key role in applications such as drilling muds, processing carbonates and separating SX crud in copper platinum ore concentrations of nickel and gold. Communication between machine producers and mineral processing engineers is vital for the right choice of materials and the design of the right decanter centrifuge for the individual process.

Feb 1, 2012

By M. A. Stoakes, H. D. S. Miller

Surface subsidence is becoming an increasingly important factor in the economics of mining Louisiana salt domes due to, amongst others, excessive shaft deformations and land loss to encroaching sea water. The vast majority of subsidence studies have been undertaken on bedded, tabular deposits. It is important to understand the causes of subsidence due to mining domal salt and how it can be minimized. The paper will review the major differences between subsidence caused by domal and tabular evaporite mines, the problems encountered in predicting subsidence, the factors that influence subsidence and, finally, possible alternative mining methods.

Jan 1, 1986

By J. Gustavson, E. Mallard, F. Pirkle

The Sales Comparison Approach to estimating the value of a mineral property must always be attempted1 . In addition to other parameters, the approach depends heavily on the availability of transaction data. The consideration for the mineral property must be in form of cash, cash equivalent or other consideration. In other words, “What dollar amount did the property sell for?” Mineral properties are generally real estate, albeit frequently buried deeply under the overlying surface real estate, unless the property may be a quarry. In some states, transactions must be recorded in county courthouses, and the sale consideration must be included. In such cases, the appraiser’s job is made easy. In other locations, the sale considerations are withheld in the courthouse data; but occasionally a local transfer tax is collected and recorded. Again, the appraiser’s job is made easy by back calculation with knowledge of the legislated transfer tax percentage. The worst problem occurs when the consideration for a mineral real estate sale is totally withheld. That may occur in so-called nondisclosure states. A recent map2 of ten non-disclosure states in red is shown below. For the full color code, please refer to the footnote

Mar 2, 2022

By Bob Rautenberg, Luminita Calin

The Tunnel and Reservoir Plan (TARP), commonly known as the Deep Tunnel Project, was developed by the Metropolitan Water Reclamation District of Greater Chicago as a two-phase solution to the problem of waterway pollution and basement flooding due to sewer system backups created by the combined sewer overflows. With only one contract left before completion of the Phase I tunnels—the 12.4 km(7.7 mi.) long Little Calumet leg—the pollution control phase of the 175.7 km(109.2 mi.) long system will be 93% complete, once the Torrence Avenue tunnel project comes to an end. This paper describes the Torrence Avenue tunnel project, currently under construction by the joint venture of Kenny (Sponsor) / Kiewit / Shea. Mining of the10.4 km (34,151 feet) long and 8.3 m (27'-4") diameter mainline tunnel was completed in a record thirty-one-weeks period and the concrete lining is nearing completion. Details on the complete muck handling system, numerous mining and concrete lining records will be given.

Jan 1, 2001

By F. Habashi

Japan was a closed society until 1853 when it was forced to open to the West. Mining, metallurgical, and geological education started there around 1861 when a graduate from Yale University in USA went to Japan to organize the first School of Mines. This was followed by other metallurgists from Great Britain, France, and Germany and thousands from other disciplines. The present report is a summary of the writer's first contact with Japanese metallurgists and his visits to a number of universities and research institutions in the past years.

Jan 1, 2012

By Kim Appleby

Epithermal gold-silver (lead-zinc-copper-manganese) mineralization on Misima Island is confined to steep and reactivated flat-lying normal faults in the upper plate of a major, shallowly dipping detachment fault. The hangingwall comprises an Eocene metavolcano-sedimentary sequence that has been extensively intruded byMiocene calc-alkaline granodiorite. It is unconformably overlain by Pliocene sedimentary and volcanic rocks. High-pressure amphibolite facies rocks dominate the footwall and have many characteristics of a metamorphic core complex. Mafic-alkalic lamprophyre dike swarms intrude the hangingwall and footwall sequences. Previous workers attributed the gold-silver mineralization on Misima to the intrusion of the porphyritic granodiorite (Williamson, 1984). This has been proposed for many tertiary gold deposits of the southwest Pacific(Sillitoe, 1989; Leach and Corbett, 1994).

Jan 1, 1996

By Paavo Eerola

In May of 1984, it was decided that Outokumpu Oy would design and build a new nickel flotation mill to process ore from the newly discovered Enonkoski mine in eastern Finland. Since there hart peen a number of successful process charges in the existing mills, the design effort included the study and incorporation of several new developments, including all-autogenous grinding, "flash flotation", lane cell roughing, large cell cleaning and a computer-based, profit optimizing, process control system. The paper discusses the background and results of those studies, and a description of the resulting mill which will begin production in 1986.

Jan 1, 1985

By Juan J. Monsalve, AMAN SONI, Nino Ripepi, Richard Bishop

The design and strength of pillars are important parameters while implementing the room-and-pillar mining method in a limestone mine. The process becomes complex with the presence of the karst voids which are frequent phenomena in a carbonate rock formation. The karst system is a network of cavities that along with an omnipresent fracture network may lead to ground control issues in a limestone mine. The objective of this study is to provide a safe and reliable alternative design for a pillar in a case study mine for safe and efficient ore recovery. This research is a continuation of a previous study aimed at studying the effect of karst void on the strength of the same limestone pillar. It was assessed from the calculated pillar strength and the estimated redistributed stresses that the pillar is capable of countering more stress than is currently imparted on it. Numerical modeling studies combining in situ stress determination and excavation sequencing were used to estimate the existing stresses on the pillar. Different possibilities of modification to existing pillar design were simulated using Distinct-Element Modeling (DEM) to determine a better design. Discrete fracture networks (DFNs) were included to imitate the effect of the presence of discontinuities. An effort is also made to understand the variation of pillar strength with height for karst-affected pillars using two different constitutive models. This study serves as a preliminary investigation in terms of improving the future design of pillars and also while recovering old pillars prone to karst formation.

Jan 30, 2023

By R. Benemelis

The existence of resins in some coal deposits in various parts of the world has been known for many years. These resins vary considerably in chemical structure and properties. The resin that is found in Utah coal, however, is rather unique, and has properties particularly attractive for the manufacture of printing ink mastics and adhesives. This resin is a rather dark, very high melting point, low molecular weight hydrocarbon resin. Its typical properties are shown in Table I. Its largest use by far, has been in the printing ink industry. The history of Utah coal resin is interesting, but unfortunately one of disappointment and failure.

Jan 1, 1990

By Rong Lu, Hao Wu, Bing Dai, Guoyan Zhao, Li Cheng, Weizhang Liang

Affected by the disturbance of blasting activities, deformation instability and rock dynamic disasters are prone to occur in deep hard rock roadways. Thus, it is particularly necessary to understand the failure behavior of rocks and roadways under dynamic loads. In this study, a series of impact loading tests were carried out on sandstone samples with and without a circular cavity by a modified split Hopkinson pressure bar (SHPB) test system. The mechanical properties and energy evolution of the samples were systematically investigated, and the effect of cavity size was analyzed. The results showed that the presence of the cavity in the samples weakens the dynamic compressive strength by more than 10%, and the peak strain and brittleness are also reduced to varying degrees. Under dynamic loading, spalling cracks occur first on the roof and floor of the cavity, and then different numbers of shear cracks are formed on the sample diagonals. The eventual shear failure mode is the result of the connection of the shear cracks and the cavity. As the cavity radius increases, the dissipated energy density and fractal dimension both grow accordingly, leading to smaller and smaller rock fragments. The dynamic failure behavior of the circular cavity can be well explained based on the dynamic stress distribution law. Overall, this study can provide a reference for the study of the mechanism of rock burst in deep roadways.

Feb 18, 2021

By Cesar A. Busnardo

The carbonatite orebody in Jacupiranga is situated some 230km (140-mi) southwest of Sao Paulo and is mined by Serrana S/A de Mineragao, producing an apatite concentrate for fertilizer production and a calcite tailing for cement manufacture (see Figure 1). The orebody (Table 1) is mined by open pit and the total production is 4.5 million mt/year of carbonatite ore with a further 2.2 million mt/year of overburden. The carbonatite low-grade ore (Table 2) is fed to the concentration plant at 460 mt/h , comprising of four parallel lines of grinding, by rod mills 2.7m x 4.5m (9 x 15-ft), operating in closed circuit with hydrocyclones. The grinding circuit product is deslimed in four stages using hydrocyclones and the deslimed product is conditioned with corn starch and subsequently floated, using fatty acids as collector to, recover the apatite.

Jan 1, 1985

By Willard A. Murray

Investigations of underground coal gasification (UCG) have been actively pursued by the U.S. Department of Energy since the early 1970s; the Lawrence Livermore National Laboratory (LLNL) conducted its first field experiment in 1976. In conjunction with field and laboratory studies of the process of recovering energy in the form of combustible gases from the burning of coal deposits in situ, an extensive environmental program has been conducted at LLNL under the auspices of both the U.S Department of Energy and the U.S. Environmental Protection Agency. This program has focused on groundwater contamination and ground surface subsidence caused by UCG. The material presented in this paper is a summary of results from the environmental studies of UCG activities conducted by LLNL as described by Mead, et al. (1981) and supplemented by the author's experience with this program in 1980 and 1981. The following sections describe specific groundwater contamination and surf ace subsidence problems encountered during field experiments in northeastern Wyoming, and will discuss implications of preliminary findings from geohydrological investigations of a site in southwestern Washington. Finally, possible environmental control technologies that are most likely to be effective in mitigating environmental impacts are discussed.

Jan 1, 1982

By M. R. Yalamanchili

The in-situ FTIR/IRS technique has been used to spectroscopically characterize interfacial water near a hydrophilic surface. Interfacial water was examined spectroscopically over known distances from the surface of a silicon single crystal by appropriate design of the geometry and optics of the internal reflection system. The in-situ FTIR/IRS spectra of interfacial water were examined by consideration of the 0 -H stretching region (3000 -3800 cm-1) associated with the vibrational spectra of water. The broad peak: in this region which describes the interfacial water structure was deconvoluted in order to isolate the overlapping spectral features of the interfacial water. Preliminary spectral results indicate the prevalence of an ice-like water structure (-3200 cm-!) at the silicon surface. Importantly, it appears that the interfacial water structure may extend a considerable distance (several tens of molecular layers) from the surface as established from the spectroscopic depth profile measurements which show that the free OH stretch at 3600 cm-1 becomes very significant at distances from the surface exceeding 400 nm.

Jan 1, 1995