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By Wen Tao Liu, Tong Tian, Fu Sheng Niu, Xiu Man Liang

The level of automation employed in flotation production is relatively low. In an actual concentrator, operators use their judgment to adjust the production state based on the visual characteristics of the flotation froth surface. There are shortcomings, such as strong subjectivity and lagging process operation, that easily cause the waste of manpower and material resources. Machine vision technology is introduced to replace human visualization, achieving a quantitative description of the visual characteristics of the froth surface. The state variable parameters are provided for the identification of the flotation conditions.

By M. Howe

This is a study of the impact of cyanide from mining waste on riparian communities, primarily vegetation, near Whitewood Creek, down-stream from Homestake Gold Mine in Lead, South Dakota. Cyanide is used in gold processing and the effluent, until fairly recently, was discharged directly into Gold Run Creek which empties into Whitewood Creek. Vegetation, soil, and water were collected from four different sites over a six month period, and samples tested for cyanide concentration. Data indicate a relationship between cyanide in soil and its uptake by certain plants, also, that the Homestake cleanup effort has made the stream viable again.

Jan 1, 1983

By Arthur J. Borst, Joseph P. Gildner

In a recent National survey, Seattle topped the list for having the worst daily traffic congestion. To address this problem, Sound Transit is planning to build 40km (24 miles) of light rail, including ten kilometers (six miles) of twin tunnels with four subway stations 40 m (130 ft.) to 65 m (210 ft.) deep. The overall schedule is very aggressive and Sound Transit is preparing four separate heavy civil construction contracts for simultaneous underground construction. Three of these contracts are being considered for design-build. Final design will start in March2000 and all underground construction must be completed by the end of 2005.

Jan 1, 1999

By J. P. Baur

The sensitivity of radiochemical techniques makes possible the study of the initial stage sulfuric acid leaching kinetics of chalcopyrite and other copper sulfide minerals. High-grade Transvaal chalcopyrite was neutron irradiated in a TRIGA reactor to produce radioisotopes copper-64, iron-59, and sulfur-35. Dissolution rates were measured in the time interval zero to 60 minutes during which time significant anomalies were observed. First, an initial period of rapid dissolution lasting a few minutes; second, an arrest or "plateau" region usually lasting from 6 to 10 minutes; third, a second period of dissolution of lesser rate than the first. The effect of solution variables such as pH, oxygen partial pressure, and ferric ion concentration at different temperatures were measured. The initial rate data were correlated by considering the rapid reaction to be due to the dissolution of surface oxidation products or the formation of an iron depleted surface layer. The data for the second slower reaction have been explained to be due

Jan 1, 1972

By Ulrich Maidl, Gustavo Aguiar, Argemiro Ferreira, Marco A. Peixoto Silva, Marc Comulada

"Metro Line 5 in Sao Paulo is being constructed. This lot extends for 4,940 m with twin EPB shield tunnels under a dense and busy urban area, with an excavation diameter of 6.9 m. The tunnels run predominantly in the tertiary soils of Sao Paulo where extensive experience exists from previous EPB shield tunnel projects. However, new experience is being gained in Sao Paulo in shield tunnelling through Saprolite, the weathered product of the underlying Gneiss crystalline basement, through the resulting residual soils and in rock-soil mixed face conditions. Furthermore, experiences in difficult mixed face soil conditions with overconsolidated clay at the face in combination with loose sands at the crown under the groundwater table will be presented. Additionally, the design, operational and controlling approach followed for the shield drive at particular critical cross-sections where the shields were driven close or under buildings. INTRODUCTION Within the framework of Sao Paulo´s metro network expansion, the excavation of the shield tunnels for Metro Sao Paulo Line 5 is currently taking place. The present paper deals with the description of the most relevant features from the construction of the Line 5 – Lot 3 tunnels. The paper presents how particular challenges were dealt maximising potential of EPB shield tunnelling technology. Challenges were posed not only by the difficult boundary conditions of urban shield tunnelling, such as shield drive under buildings, but also by complex geotechnical situations. PROJECT DESCRIPTION The great urban area of São Paulo is one of the biggest cities in the world, with around 20 Million people living in the city and in the suburb area. The city faces great mobility problems and in the last years the government has been investing great amounts on the megacity´s metro expansion. The Line 5 Extension plays an important role to connect the south area to the central area of the city, with a whole extension of 11 kilometres, including 11 new stations. It is estimated that this line will transport almost 900.000 passengers/day. The first stretch of the expansion, Lot 3, consists of two single tunnels, almost 5 kilometres long each, crossing 4 stations. Figure 1 shows details of the Line 5 Expansion."

Jan 1, 2016

By Frederick J. Hoppe

The productivity or usefulness of a Front End Loader rises rapidly with its size. Loading is more aggressive. Mother Nature is defeated more easily. Larger tires get a better grip on the ground. Hauling equipment can be loaded more quickly. The productivity or usefulness of a Front End Loader is proportional to its working speed, both automotive and hydraulic. The price of speed is horsepower, which rises rapidly with speed. Horsepower saved shows up as increased productivity. This paper covers the development of the D600, KW-Dart's articulated loader, which combines massive size with new concepts to increase its working speed. Featured is a discussion of the horsepower saving, "Balanced Boom."

Jan 1, 1969

By J. S. Hu

FTIR spectroscopy has been used for the characterization of adsorbed oleate at the fluorite surface. It has been found that modest changes in the adsorption density at high temperature and high oxygen potential do not provide a satisfactory explanation for the significant increase in the hydrophobic character of the system under similar conditions. Rather, FTIR spectroscopic measurements suggest that chemical interaction between adsorbed oleyl groups occurs at high temperature and/or oxygen potential and accounts for the increased hydrophobicity. Specifically, the intensity of the =CH bond of the adsorbed oleate diminishes at high temperature and/or high oxygen potential. Such a phenomenon was not observed in control tests with the calcium oleate soap. For extensive reaction at the fluorite surface, the presence of a new surface species has been identified. These results indicate that the fluorite surface catalyzes an oxidation and/or polymerization reaction between adsorbed oleyl groups which results in a more hydrophobic structure at the fluorite surface.

Jan 1, 1986

By E. B. Kroeger

Spoil instability has been a problem at a coal mine in interior Alaska. Parameters such as original site topography, groundwater conditions, material properties, spoil-pile geometry, geology, permafrost, natural slope instability, changing weather conditions, and dense, near-surface vegetation have interacted to produce unstable slopes. Several failure modes have been identified including deep seated earth block slides, bimodal earth flows, and solifluction. Thawing of permafrost also created conditions where sliding of spoil along the interface separating the spoil and the natural ground surface occurred when the cohesion and the friction angle of that zone was reduced to zero and below 15?respectively.

Jan 1, 1992

By Dermot M. Ross-Brown

The more important factors controlling the design of pit slopes are related to the local geology over which the designer has little or no control. Nevertheless, there are some factors over which the designer does exert some control and these concern the say in which the rock is excavated and supported. They include blasting, face cleaning, water control, and the use of rock improvement techniques. The paper discusses these factors and relates the extra costs incurred to the steeper slope angles that can usually be obtained. It is demonstrated that even a modest increase in bench angle of 5° through improved excavation techniques can pay off in a single push-back.

Jan 1, 1975

By Alvin Kaufman

Malthus, an eighteenth century economist, predicted a rather dismal future for the world. It was his contention food supplies would not be sufficient for the population of the world because the economy of a nation grew arithmetically while population increased geometrically. As a consequence, within a relatively few years mass famine would spread throughout the world. This prophecy, based on an agrarian economic situation, did not come true at least insofar as the Western World was concerned. In largo measure, the salvation of our part of the earth resulted from the growth engendered by the Industrial Revolution. Throughout much of today's world, however, the Malthusian theory seems to be coming true. The advantages and benefits of the Industrial Revolution have net reached all nations. Further, the situation has been compounded by the benefits of modern medicine. This has reduced child mortality and extended life expectancy, but placed no limitations on births in the developed countries, child mortality has declined to 2 percent and adult life expectancy has doubled, but education and general prosperity have resulted in voluntary limitations on pregnancies thus partly offsetting the increased chance of survivals Even so, the present rate of population increase in Europe is approximately 6 percent per decade, and somewhat higher in the U.S., Japan, and other developed countries. The world as a whole, however, is expected to double its population by the year 2000, This would imply a rate of increase in the less developed countries approximately four times that in Europe.

Jan 1, 1966

By P. Asadollahi, M. Invernizzi

"This paper describes the innovative full-face conventional tunnel excavation technology, with its advantages in terms of savings and safety. The full-face approach has been developed throughout the experiences gained in tunnel construction. The innovative design approach is focused primarily on the deformation response of the ground acting first and foremost ahead of the face, which is analyzed, predicted and controlled by pre-confinement of the core. The advantage of this method is particularly evident in difficult grounds. This paper will present the outstanding benefits given by the adoption of the full-face approach in two projects, the “Sochi” and the “Visnove” tunnels. THEORY AND DESIGN ASPECTS OF THE FULL-FACE EXCAVATION The main challenges in tunnel and underground construction industry are gathering the design data from the ground that is being excavated and foreseeing the critical stage during construction, where the materials are in its most critical configuration. These challenges shall be addressed during excavation when the lining and the excavation disturbance have not yet reach the equilibrium. The in situ stresses in the ground are redistributed (forming an “arch-effect”) around the opening, with zones of increased stresses around the walls of the excavation (Figure 1). The distribution of the stresses can be close or far from the excavation profile, depending upon having a ground capable of withstanding the deviated stresses well or unable to withstand them, respectively. In the latter case, the ground will plasticize and deform in proportion to the volume of ground involved in the plasticization phenomenon. When the ground completely cannot withstand the stresses redistribution, it will cause the collapse of the excavation. While in the first case, the arch effect occurs naturally, in the second case, it does occur naturally only when the ground is stabilized properly. In the case of collapse, the arch-effect must be produced artificially operating on the ground prior excavation. The design should be based on the understanding of if and how the arch-effect can be mobilized during tunnel excavation and ensure that is formed by calibrating excavation and stabilization operations appropriately. The arch-effect is function of the medium that is being excavated, the action taken to excavate and the reaction expected following the excavation."

Jan 1, 2018

By W. Todd

The Robbins Company has developed a boring machine, with a rubber packer serving as the gripper system, for blind boring of raises without using drill pipe. This machine is the BorPak and has many applications for use in the mining industry which will improve productivity. In addition to the cost savings, the boring method will lead to increased safety in constructing blind raises. The advantages of using the BorPak in a mining environment will be discussed together with possible applications.

Jan 1, 1994

By J. Edberg

"This article details the use of an alternative testing method to the 2004 "Post-Tensioning Institute (PTI) Recommendations for Prestressed Rock and Soil Anchors" manual’s recommendations for temporary and permanent rock anchors for applications in shafts and tunnels. This method was developed and used for the Black River Tunnel (BRT) project in Lorain, OH as a means to reduce testing time of rock bolts during shaft construction while maintaining a similar level of quality control and assurance. The following sections will detail the project background, subsurface characteristics, shaft construction, the 2004 PTI testing method and associated difficulties, the alternative testing method and conclusions reached.Project backgroundThe city of Lorain is located in north central Ohio on the south shore of Lake Erie, approximately 40 km (25 miles) west of Cleveland and 119 km (74 miles) east of Toledo. The city chose to build a large-diameter storage tunnel and pump station to meet its requirements to reduce sanitary sewer overflows to the nearby Black River. NTH Consultants Ltd. (NTH) was retained by the city’s prime consultant, Malcolm Pirnie Inc. (now the water division of Arcadis), to perform a geotechnical investigation, develop design and construction bid documents for the tunnel and shaft liner systems and ultimately provide oversight assistance during the construction phase of the project.The BRT is an approximately 1,700-m (5,560-ft) long, 7-m (23-ft) diameter rock tunnel to be lined with a 5.8-m (19-ft) inside diameter secondary concrete lining (Fig. 1). The tunnel is designed to accept flow at a new drop shaft (Shaft 3) located on the west side of the Black River, across from the city of Lorain Black River waste water treatment plant (BRWWTP). The tunnel will be dewatered at the south end by a large diameter pump station (Shaft 1) located in the existing Lorain Port Authority Public Boat Launch. Flow from the new pump station will be discharged into an existing shallow interceptor sewer and directed back to the BRWWTP."

Jan 1, 2014

By M. S. Safarzadeh, V. Agarwal

"The solvent extraction of cerium(III) and samarium(III) from mixed solutions of all rare earth elements (REEs) except promethium using PC88A (2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester), an acidic extractant, was investigated. The effects of aqueous equilibrium pH, various acids (sulfuric acid (H2 SO4 ), hydrochloric acid (HCl) and nitric acid (HNO3 )), initial metal ion concentration and extractant concentration on the solvent extraction of Ce(III) and Sm(III) were systematically studied. From the experimental results, HNO3 and HCl were found to be the preferred aqueous media for the solvent extraction of both Sm(III) and Ce(III). The most promising experimental conditions of pH, PC88A concentration and metal ion concentration were identified for the extraction of Ce(III) and Sm(III). Separation results showed that H2 SO4 at pH 2 provided the best separation between Sm(III) and Ce(III). IntroductionIn recent years, demand for rare earth elements (REEs) has increased significantly because of their many commercial applications. REEs have especially important high-tech applications owing to their unique physical and chemical properties, and they are used in a wide range of areas such as catalysts, ceramics, magnets, lasers, glass, neutron absorption and alloys. As REEs have very similar physicochemical properties, their separation and purification from each other is challenging and gaining significant interest. Samarium (Sm) and cerium (Ce) are found in different REE minerals, including bastnäsite ((Ce,La,Nd(CO3)F), xenotime (YPO4) and monazite ((Ce,La,Nd,Th)PO4) at major production sites in the United States and China, as listed in Table 1 (Bleiwas and Gambogi, 2013). The most common acidic organophosphorous extractants used for REEs extraction and separation are DEHPA (di-(2-ethylhexyl)phosphoric acid), PC88A (2-ethyl hexyl phosphonic acid mono-2-ethyl hexyl ester), Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) and Cyanex 301 (bis(2,4,4-trimethylpentyl)dithiophosphinic acid) (Sarangi, Reddy and Das, 1999; Surampally et al., 2012; Tian, Jia and Liao, 2013). Out of these extractants, PC88A is known for providing higher separation factors (Acharya, Mishra and Misra, 2015). El-Hefny et al. (2010) investigated the kinetics of the solvent extraction of Sm from chloride media using sodium salt of Cyanex 272 and reported the extracted species to be Sm(OH)A2•2HA. Lee et al. (2005) investigated the solvent extraction of Sm(III) with PC88A and saponified PC88A from chloride solutions and found the stoichiometry of the extraction reactions to be 1.5 with PC88A and 3 with saponified PC88A."

Jan 1, 2017

By D. G. Chedgy

Careful consideration is given to the type of cleaning equipment and control sys- teas to be used when selecting circuits for wash-ing fine coal (28M x 0 size fraction). However, the desliming, declaying and sizing procedures required to ensure efficient operation normally are not evaluated in sufficient detail resulting in disappointing system performance. This paper details desliming and dewatering circuit design which is extremely effective based on recent test data. The circuit maintains control of the 28M x 0 (declayed) size fraction with minimal misplaced material and maximized circuit efficiency. A discussion of circuit design parameters and control systems, as well as results from the testing program, are included in this text.

Jan 1, 1986

By Ashis Bhattacherjee, Rahul Upadhyay, Nearkasen Chau, Aditya Kumar Patra, Dhanjee Kumar Chaudhary

Heavy earth-moving machineries used in openpit mines intensively expose drill operators to whole-body vibration and shocks, and thus to musculoskeletal disorders. The roles of individual, machine and rock-related factors in their exposure remain poorly understood. This cross-sectional study investigated their roles in 39 drill operators from Indian iron ore mines. It shows that 70 percent of the operators were exposed to high levels of vibration, above the limit values recommended by ISO 2631-1 (1997). Multiple linear regression models showed that the whole-body vibration and shock exposures were strongly associated with operator’s age, drill-machine model and rock hardness, uniaxial compressive strength and density. The role of body mass index was close to significance (p = 0.08). Univariate analyses found the drill’s age, seat-pad thickness and seat backrest height were also strong predictors. These results help in identifying risky operators, materials and occupational situations, and in implementing appropriate prevention and intervention strategies to reduce and monitor the exposures and health risk. In addition, during the planning stage of acquisition of new equipment, anthropometric data of the operators should be considered for the ergonomic design of the seat.

By Ch. R. V. S. Nagesh, Ramesh Naidu Mandapati, Venkata Swamy Nalajala, Tondepu Subbaiah, Naga Jyothi Kothamasu

Leaching studies of magnesite obtained from Tamilnadu Magnesite Limited, Salem, have been carried out using hydrochloric acid leaching and percentage of magnesium chloride recovered was estimated. The variables considered in this study were the following: duration of leaching, volume percentage of hydrochloric acid, temperature, and pulp density. Percentage recovery of magnesium chloride increased with duration of the leaching, volume % of concentrated hydrochloric acid, and temperature. Percentage recovery of magnesium chloride decreased with increase of pulp density. The optimum conditions found to be pulp density (10%), hydrochloric acid concentration (30%), duration of leaching (2 h), and temperature (348.15 K). Iron was removed by treating the leach liquor with hydrogen peroxide and by raising the pH to 3.5–4. The purified leach liquor was subjected to spray drying for producing high pure magnesium chloride.

Jun 7, 2022

By Yi Yang, CHENGLONG XU, HAORAN LI, YALI FENG, JINRONG JU

This study presents a method for recovering valuable metals and synthesizing anhydrite from steel slag using sulfuric acid leaching and solvent extraction. The process achieved high leaching efficiencies for V, Ti, Fe, and Mg, and produced anhydrite with 93.09% purity. The leachate was further processed to separate and recover V, Ti, Fe, and Mg using selective stripping and precipitation methods, offering a sustainable approach to steel slag utilization.

Jan 22, 2022

By Eugie Kabwe

The effective employment of a pretensioned bolt within support structures requires an appropriate installation tension as a result of sufficient bolt head/nut preload. In this paper, a load indicator washer (LIW) able to withstand an assigned static loading as well as provide an appropriate pretension is presented. The different LIW breadths are numerically analyzed with ABAQUS finite-element code to estimate deformation when a designated 60 kN preload is applied. The numerical simulation employs the bilinear isotropic hardening constitutive law governed by the von Mises yield criterion. The simulation also considers the nominal temperature of the nut-LIW-rock bolt connection. Therefore, long-term relaxation effect on bolt pretension as a result of stress relaxation is neglected. The compressive force required to achieve the LIW predetermined deformation is the bolt pretension. It is drawn from the simulation results that LIWs with thicknesses of 1.5, 2.0, 3.0, 3.5 and 4.0 mm are completely flattened when subjected to 28, 42.5, 65, 76 and 88 kN preloads, respectively.

By G. J. Joy, J. P. Rider

Technical advances in longwall mining over the last several years have resulted in much larger and faster shearers that have the capability of mining at speeds over 30 m/min (100 fpm). This has resulted in a substantial increase in the amount of dust that is generated at the shearer and during shield advances. Meanwhile, increased underground coal production has put a greater demand on longwall dust control systems as some operators have had difficulty maintaining consistent compliance with federal dust standards. To address this need, the U.S. National Institute for Occupational Safety and Health (NIOSH) is investigating the effectiveness of a water spray manifold mounted on the tailgate end of the shearer body. The sprays are oriented parallel to the tailgate ranging arm, and these sprays create a water curtain confining the dust plume near the face, preventing the dust from drifting into the walkway. This redirection of dust provides a clean air envelope for the tailgate shearer operator and jacksetters working near the tailgate drum. Three different tailgate spray manifold designs were tested and evaluated at the Office of Mine Safety and Health Research (OMSHR) Pittsburgh Longwall Test Facility. Manifolds were equipped with hollow cone or flat fan water spray nozzles and evaluated at three face air velocities — 152, 213 and 274 m/min (500, 700 and 900 fpm)— and at water pressures of 689, 1,034 and 1,379 kPa (100, 150 and 200 psi). Reductions in dust concentrations were observed at six face sampling locations for all the tailgate manifold systems at each of the tested spray pressures and face velocities. Average reduction efficiencies of at least 90 percent were seen at the three sampling locations closest to the shearer for all three manifold systems at nozzle spray pressures greater than 689 kPa (100 psi). Based on results from the laboratory tests showing reductions in dust concentrations at sampling locations downwind of the shearer, a spray manifold was fabricated and evaluated at an underground operation.

Jan 1, 2016