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By Zeng Zheng, Liu Chen, Yu Xing-Fu, Tian Su-Gui, Zhang Chao

"Single crystal nickel-base superalloy is prepared by using the various withdrawing rates. By measuring creep properties and microstructure observation, the influence of the element segregation on creep properties of the superalloys is investigated. Results show that the dendrite spacing and the segregation extent of the elements decrease with the enhancing withdrawing rate. The superalloy with smaller dendrite spacing has lower segregation of the elements and better creep resistance. The dislocations climbing over the rafted y’ phase is thought to be the deformation mechanism of the alloy during steady state creep. In the later stage of creep, the fact that some dislocations shear into the rafted y’ phase may twist the rafted y’ phase. As the creep goes on, the initiation and propagation of the cracks occur up to occurring creep fracture, which is thought to be the fracture mechanism of the superalloy during creep.1. IntroductionSingle crystal nickel-based superalloys consist of high volume fraction of ?? strengthening phase and ? matrix, and possess the excellent high-temperature mechanical and creep properties, therefore, they have become the main material to make the blades of the advanced aeroengines[1-3]. Some literatures report that the temperature-bearing and creep-resistance properties of the single crystal nickel-based superalloys can be remarkably improved as the increases content of the refractory elements, such as W and Re[4-6]."

Jan 1, 2012

By I. Zh. Bunin, G. K. Khachatryan, N. E. Anashkina

For optimization of diamond processing technology the influence of nanosecond high voltage pulses on mechanical and technological properties of diamond crystals and kimberlite rock-forming minerals (calcite, olivine, serpentine) was investigated. Using methods of Fourier Transform Infrared Spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), microscopy and mikrohardness measurement the changes of structural, physic-chemical surface properties, and microhardness of minerals as the result of impacts, was studied. Non-thermal impacts caused a decrease of kimberlite rock-forming minerals microhardness in general to 40-66% as the result of surface microstructure destruction which is caused by formation of micro cracks, traces of surface breakdown and other defects. At the same time, the pulse energy impact on natural diamonds led to formation of B2 type crystal lattice microsift defects, elevated concentration of which increases the hardness properties of crystals. The obtained result indicates possibility of applying pulsed energy effects to improve the softening efficiency of diamond-bearing kimberlites rock-forming minerals without damaging the diamond crystals and ensuring their preservation by the subsequent grinding of ores. By IR and X-ray photoelectron spectroscopy revealed that processing by hight voltage pulses causes a change of natural and synthetic diamonds surface functional cover composition. Short-term exposure (~ 10 - 30) leads to detachment and partial destruction of secondary phases mineral films on the surface of natural technical diamonds, increasing floatability and hydrophobicity of crystals. However, with increasing duration of treatment (~ 30 - 150) occurs surface hydroxylation (found by XPS for synthetic diamonds), as a result of diamond surface layer oxidation. The effect of increasing the natural diamonds flotation activity by 14% (from 47% to 61%) was experimentally established as a result of processing diamond crystals with nanosecond pulses (~ 10-50 sec), which indicates the principal possibility of using pulsed energy impacts to intensify the diamond flotation during processing diamond-bearing kimberlites.

Jan 1, 2018

By Joshua Hoffman, William Chad Wedding, Braden Lusk

The University of Kentucky employs an explosively driven shock tube in the course of experimentation. A good deal of the work completed relates to the verification of blast mitigation products and strategies. The work is dependent upon reliably reproducing specific pressure time histories called out by the test in question. The facilities are located in the workings of an underground limestone quarry in Georgetown Kentucky. As such, the temperature maintains fairly consistent 60°F (15.6°C), making it a comfortable work environment year round. Unfortunately, the relative humidity follows the prevailing weather conditions allowing a wide variation, especially between the winter and summer seasons. A study was undertaken to gauge the influence of relative humidity on shock wave generation, including the positive and negative phases of the wave.

Jan 1, 2011

By M. A. Llavona

The study of the formation and components of copper patina and its conservation has assumed great importance. The changing environment has accelerated the processes of patinas degradation; thus, the exhaustive study of factors capable of affecting the patina formation, growth and durability has assumed great importance for the industrial activity of copper. The main components of the patina, oxides, chlorides, nitrates and sulfates, have been determined; the effect of physical, chemical and microbiological factors on patina formation, particularly the influence of acid rain, natural organic matter, particles and microorganisms have been defined. The effect of different electrolytic solutions that accelerate the formation of copper patinas has been determined, and a review of the state of knowledge of the formation and evolution of metal patinas has been made.

Jan 1, 1999

By Andy Cole

Barrick Gold recently implemented an oxygen roasting process to treat carbonaceous ore from its Goldstrike property in Nevada. One of the key project challenges was the design of the roaster gas cleaning system, which was driven by the requirements of a strict air permit and the need to achieve very high reliability. The roaster gas systems include multiple stages of wet particulate collection, a dual-alkali SO2 scrubber, mercury scrubbing, CO oxidation and NOx reduction. This paper describes the gas system, the influence of regulations on project implementation, and performance of the system.

May 1, 2002

By A. Cole, F. Porretta

Barrick Gold recently implemented an oxygen roasting process to treat carbonaceous ore from its Goldstrike property in Nevada. One of the key project challenges was the design of the roaster gas cleaning system, which was driven by the requirements of a strict air permit and the need to achieve very high reliability. The roaster gas systems include multiple stages of wet particulate collection, a dual alkali SO2 scrubber, mercury scrubbing, CO oxidation and NOx reduction. This paper describes the gas system, the influence of regulations on project implementation, and performance of the system.

Jan 1, 2002

By Hervé Le Bissonnais, Jean-Pierre Janin, Anne Bergère, Pierre Renier

"The most important impact on the environment of a tunnel excavation is the creation of surface settlements. Nowadays, the mechanized tunneling allows minimizing the settlements, applying a confinement pressure which counterbalances the ground de-confinement. It is thus essential to determine the correct amount of confinement pressure. In this paper, the authors present a 3D numerical study simulating the EPB-TBM excavation of a water tunnel, in the Flanders clays (north of France). Firstly, a simplified 3D simulation, based on the concept of instantaneous longitudinal settlement curve, was performed to predict the surface settlements for different values of heading confinement pressures. Secondly, the same pressures were tested by the EPB-TBM in a monitoring zone. The comparison between the prediction settlements and the measurements was very satisfactory and allowed validation of the numerical approach and the choice of the optimal confinement pressure value for a sensitive area of the project. INTRODUCTION The excavation of a tunnel can create displacements of the surrounding soil which may affect existing structures and generate unacceptable dysfunction. The development of the closed shield tunneling has permitted to reduce the volume loss generated around the excavation and consequently the surface settlements. In this case, as explained by different authors (Clough et al., 1985; Kastner et al., 1996; Mair and Taylor, 1997), the ground movements are influenced by the TBM works: the heading confinement pressure, the shield overcutting and conicity, the annular void grout injection parameters, the segment concrete lining rigidity, the consolidation of the grout. Hence, in the tunnel design, it is important to take into consideration these different processes of the excavation works to simulate correctly the tunneling process."

Jan 1, 2016

By Walid El Kamash, Sadik Oztoprak

"Soft soil presents a challenge against multistory buildings in some cities of Egypt such as Port Said due to the consolidation settlement. Deep mixed (DM) columns are used to improve the soft foundation soil in order to reduce the total and differential settlements. Latest research revealed that this improvement technique also increases the rate of mechanical consolidation due to column yielding caused by stress concentration from the soft soil. In this study, extended poly-styrene (EPS) Geofoam is used to replace the soft soil over DM columns in order to control the stress concentration and settlement. To understand the effect of EPS geofoam on the degree of consolidation, stress concentration and settlement, a parametric study was carried out through a mechanically and hydraulically-coupled numerical method. A unit cell model is used, in which the soil was considered linear elastic; DM column and EPS Geofoam are elasticplastic materials. Results reveal that EPS geofoam is helpful for reducing the settlements and accelerating the consolidation. Increasing the length of the column of the deep mixed foundation with EPS geofoam has a significant effect on accelerating the consolidation.INTRODUCTIONExpanded polystyrene (EPS) geofoam is a lightweight polymeric material which is made by expansion of raw plastic beads. The expansion of the EPS beads are spherical-shaped particles containing closed hollow cells. EPS which plays an important role as an innovative lightweight construction material is now well recognized due to its low density in addition to high compressive and rupture strength. Inglis (1996) reported the first use of EPS geofoam as a seismic buffer to reduce potential seismic loads against a nonyielding basement wall. Gaskin (2000) and Bathurst et al. (2007) carried out reduced-scale shaking table test on a rigid retaining wall protected by EPS geofoam. The test data showed that the peak lateral loads acting on compressible model walls were reduced below values measured for nominally identical structure but with no compressible inclusion. Abdelrahman and El Kamash (2014) investigated the behavior of EPS Geofoam beneath raft foundation on soft soil of Port Said. They showed the ability of EPS to control vertical displacements. The investigation of the behavior of EPS geofoam with DM column has not attracted more attention of previous researchers. In this paper, the behavior of replacing the soft soil by EPS geofoam was examined in the presence of DM column."

Jan 1, 2015

By W. G. Miller, J. D. Scott, D. C. Sego

ABSTRACT The influence of using different extraction processes (caustic versus non-caustic) on thethixotropic strength of oil sands fine tailings is examined, as is the influence of adding a coagulant tocaustic fine tailings. The thixotropic strength of fine tailings at large void ratios manifests itself as a bonding or gel strength that has been widely noted both in the laboratory and in the field. This gel strength has a significant influence on preventing the initial consolidation or settlement of fine tailings. Differences between the fine tailings’ thixotropic strength development are explained based on their physical and chemical characteristics.

Jan 1, 2010

By J. J. K. Daemen, C. Fairhurst

Introduction The stress field around a supported tunnel can be considered as being composed of: i) the virgin (pre-mining) stress in the rock ii) the (elastic) change in this stress field caused by creating the opening iii) the (time-dependent ) change in the stress field produced by (i) and (ii) as a section of the rock breaks up iv) the (time-dependent) influence of the stress build-up in the support. Several authors have examined the conditions necessary to produce static equilibrium between the support, the rock, and the regional (in-situ) stress field. The analysis used by Labasse (1) is typical. Consider a circular tunnel radius R in a hydrostatic stress field (P), and a radial pressure pi exerted by the support. According to Labasse, the radius ‘b’ to which the rock will break* for a given support pressure, pi, can be calculated from: - the equilibrium equation: [ ] As a zone of broken rock develops around the opening, the stress circle for a point on the elastic-broken rock boundary moves to the right in the Mohr diagram until the radial stress in the broken zone s equal to the radial stress in the elastic zone.

Jan 1, 1971

By Edward J. Bagnall

The major raw material feed properties of size distribution and chemistry are examined in relation to their effect on sinter operating conditions, plant productivity, sinter physical quality, reduction- degradation characteristics and sinter texture and mineralogy. The resultant physiochemical properties of these sinters are related to their behaviour in subsequent ironmaking operations.

Jan 1, 1977

By P Hunger, H Günter, F Heinicke

High pressure grinding rolls (HPGR) have been used for more than 20 years to grind iron ore pellet feed. Besides coarse comminution (crushing), where HPGR are installed upstream of the ball mill, there are numerous flow sheets where HPGR are used after ball milling and dewatering for re- or finish grinding.There is a clear growing interest in grinding of pellet feed with HPGR during the last few years. In addition to their known advantages of low specific energy consumption, high availability, low steel consumption and improved pelletising processes the lower environmental load (reduced or no water consumption) became a strong driving factor for the application of HPGR in pellet feed grinding.This growing demand increases the interest in better understanding of the HPGR grinding process with fine iron ore concentrates. One of the most important process parameters is the moisture content of the feed material which influences the performance of the HPGR enormously. The HPGR can react to fluctuations of the fresh feed properties to a certain degree by adjusting grinding force and roller speed. Nevertheless, there are limitations by the physics of the compression process and the capability of water absorption by the concentrate. The capability varies for different concentrates and different specific surface areas. This fact has to be considered during engineering of the beneficiation plant.The paper focuses on the influence of feed moisture content on the HPGR performance in view of throughput, increase of Blaine number and process stability on the basis of numerous pilot plant tests, modelling results and industrial experiences.CITATION:Heinicke, F, Günter, H and Hunger, P, 2017. Influence of feed moisture on high pressure grinding roll pellet feed grinding, in Proceedings Iron Ore 2017, pp 187–194 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Thomas Mütze, Frank van der Meer, Gunnar Kretschmar

"The air classification of moist bulk materials is addressed in the literature insufficiently. Therefore a feasibility study investigated the influence of feed moisture on the separation efficiency expecting a reduction with higher moisture content in the feed. Two iron ore samples were characterized in terms of the nature of bonding of moisture as well as its effect on the agglomerate strength. The classification tests themselves were conducted with two dynamic laboratory air classifiers at cut sizes from 45 to 110 µm and a moisture of the feed material between 0 to 10 wt.-%. The quality of classification was assessed by split factor, cut size, separation efficiency, moisture of both products, as well as the yield of the fines as product fraction in a corresponding processing plant. An initial approach was found for a technological implementation: A sufficient drying of a moist feed can be realized simultaneously to the pneumatic transport inside the classifiers. In the present case the drying effect and dispersion intensity was sufficient to provide good separation results up to 3 wt.-% feed moisture. An additional drying step was necessary beyond 3 wt.-%.INTRODUCTIONSpecific information about the influence of moisture in air classifiers is very rare. Mostly only dry products are processed and/or drying prior to classification is recommended. Apart from the specific influence of the feed moisture a lot of literature can be found regarding air classification itself. Altogether air classification can be divided into several sub-process (Leschonski, 1977):- dosage of the feed material,- dispersing the solid feed material into a gas stream,- feeding the dispersed material into the classification zone by pneumatic conveying,- separation of coarse and fine particles, and- separation of fine particles from gas.For wet feed particles also drying plays an important role. Interesting for the present investigation are the humidity of the feed and its influence on the single sub-processes."

Jan 1, 2016

By A. Bakalarz, M. Duchnowska

"The copper sulfide ore from the Legnica-Glogow Copper Basin in Poland, which is processed by KGHM Polska Miedz S.A., consists of three lithological fractions: dolomitic, sandstone and shale. The copper ore, depending on the mining area, contains all fractions in different ratios. The lithological fractions differ in the particle-size distributions of their useful minerals. In the dolomitic part of the ore, most of the metal sulfide particles are 50-200 microns in size, while those in the sandstone and carbonaceous shale are 30-200 and 5-40 microns in size, respectively. This complex composition results in different mineralization, physicochemical properties and, in particular, upgrading selectivity. Due to the specific nature of the examined copper ore, two of the crucial parameters determining the beneficiation efficiency are size and liberation of sulfide particles. We analyzed the influence of grain size of feed on scavenging selectivity in one of the KGHM flotation plants and performed evaluation and analysis of the upgrading results of industrial beneficiation of the ore, containing mostly dolomite and shale. The upgrading efficiency was estimated using a selectivity indicator obtained by means of the Fuerstenau upgrading curve, which was then correlated with the particle-size distribution of the flotation feed.IntroductionFroth flotation is used extensively in commercial ore treatment flotation plants to separate minerals from gangue and to separate minerals from each other. The floatability of ores and their benefication selectivity are determined by many factors. One of them is particle size. The effect of particle size on flotation performance has been widely studied by many authors (Gaudin et al., 1931; Trahar, 1976; Trahar and Warren, 1976; Lynch et al., 1981; Pease et al., 2004). Particle size also plays a critical role in the probability of particle collision and attachment to bubbles (Solari and Gochin, 1992; Schulze, 1993), kinetic flotation (Taggart, 1956; Ahmed and Jameson, 1985; Debacher, 2002; Brozek and Mlynarczykowska, 2007; Potulska 2008), collector consumption (Sutherland and Wark, 1955; Vianna et al., 2003) and mechanical entrainment (Lynch et al., 1981; George et al., 2004; Konopacka, 2005). Most of the results have shown that there is an optimum particle size range for a given flotation system and that the simultaneous optimization of the recovery and concentrate grade of these particles in conventional flotation equipment is extremely difficult."

Jan 1, 2015

By Thibaut Pannetier, Damien Rogat, Catherine Larive, André Regnard, David Chamoley

"INTRODUCTION For several decades, the use of fibre-reinforced sprayed concrete (FRSC) has been becoming increasingly widespread, either as a replacement for or in addition to traditional reinforcements. Macro-synthetic fibres appeared on the market at the same time as metal fibres (in the 1980s), but their use has developed more recently in France, starting in the early 2000s. While their properties are attractive for underground operations, their long-term performance remains the subject of some controversy, particularly with regard to the phenomenon of creep [1-5]. Unfortunately, the many differences of protocol among the studies carried out (materials, metering, spraying equipment and test methods, etc.) mean that, in general, the results cannot be compared. Although several methods have been developed to assess the bending creep behaviour of fibre-reinforced concrete, the majority of them test notched beams resting on isostatic supports. There are currently no standardised test methods adapted to FRSC on hyperstatic supports (as is the case for FRSC used for underground support). The Asquapro association has thus developed a new test specially designed for this type of concrete. Slabs of thickness 10cm, measuring 60 x 60 cm in plan have been sprayed and tested under bending stress according to a test procedure inspired by the standardised test of energy absorption capacity (NF EN 14488-5). An experimental campaign was launched in October 2014 to study the behaviour of seven types of sprayed concrete, manufactured using the same concrete matrix: six of them were reinforced with different metal or macrosynthetic fibres and the seventh with a welded wire mesh. Fourteen slabs were sprayed for each type of concrete and also for the non-reinforced concrete with the same matrix. The types of mechanical performances measured were the compressive strength and energy absorption capacity (at seven and twenty-eight days), in addition to the creep behaviour of these seven types of concrete, placed under stress on the seventh day. This article follows on from that published in the WTC 2015 congress proceedings [6]: the programme and the test methods are briefly described here and the results available at the time of writing are presented and discussed."

Jan 1, 2016

By W. G. Pariseau

Regression analysis of calculated on measured displacements were used to assess the influence of fill and fold plunge on shaft pillar mining at the Homestake Mine. These effects were neglected in the original three-dimensional finite element analysis undertaken in 1991. An average fold plunge of 15? and a 24K fill (Young’ modulus of 24,000 psi or 165 Mpa) were used in the reanalysis. Measured displacements were obtained from an array of 36 m (120 ft) multiple-position borehole extensometers installed in June 1994 and read to March 2003. Results indicate the effects of both on calculated displacements and thus on regression parameters are noticeable. However, these neglected effects would not have changed the original inference of Ross Shaft stability during pillar mining.

Jan 1, 2004

By K. Esmaieli

This paper addresses issues associated with ore pass degradation caused by material impact. A series of numerical experiments, using the particle flow code, were undertaken to investigate the influence of various finger raise configuration. This has allowed the identification of favorable configurations. The results of this analysis, when coupled with field observations, can contribute to the design of ore pass systems that can prolong the useful operating life of ore pass systems.

May 1, 2009

By Dao-Wu Yang, Ju-Lan Zeng, Li-Xian Sun, Yan Yao

"The hydration heat of the pure cement, the fly ash single-dopped cement, as well as the fly ash and fluorgypsum co-dopped cement were investigated by means of micro-calorimety with an eight-channel micro-calorimeter (TAM Air). The results showed that the hydration heat and the hydration rate could be reduced significantly by fly ash and fluorgypsum. However, the reduction was not proportional to the loading of dopant. The exothermic peak of the fly ash and fluorgypsum co-doped cement was appeared earlier than the fly ash single-doped cement. As the temperature decreased, the hydration heat and the hydration rate of the doped cement were reduced, and the exothermic peak appeared later. The effects of fly ash and fluorgypsum on the compressive strength of cement were also investigated. The results revealed that the early compressive strength of concrete made up of the co-doped cement was largely higher than that of the fly ash single-doped cement. Based on the experiment results obtained in this paper, we could conclude that fluorgypsum is a suitable additive for fly ash-doped cement.IntroductionFly ash and fluorgypsum are industrial waste. In 2008, nearly 400 million tons of fly ash has been produced by coal-burning power plants in China. And it is estimated that this number would exceed 500 million at the year of 2015. Besides, every year the fluoride salt factories in China discharge more than 100 million tons of fluorgypsum. Tremendous of fly ash and fluorgypsum occupy considerable land and contaminate air and water sources [1]. As a result, comprehensive utilization of this two industrial waste has draw great attention from all over the world.Cement is the most-used construction material on earth. But the production of cement consumes huge energy and destroys the environment. This problem might can be partly solved by applying fly ash and fluorgypsum as additive for cement [2-4]. During the last decade, some papers that focused on applying fly ash and fluorgypsum as additive for cement have been published [5, 6]. However, to the best of our knowledge, none of these papers investigated the hydration heat of the fly ash and fluorgypsum co-doped cement.The hydration of cement is an exothermic reaction, which can result in serious problem for mass concrete: The interior of the concrete could reach very high temperature as the hydration proceeded [7-9]. As a result, the great temperature difference between the interior and the outer of the concrete would exist and cause serious thermal stresses. Thus, the concrete would be destroyed by the cracks which in tum are resulted from the thermal stresses [10, 11]. The heat released by the cement hydration and the hydration rate is commonly regulated by adding mixed materials or transferring additive such as fly ash and fluorgypsum [12-14]."

Jan 1, 2011

By T. A. Boyden

The Free World uranium market is now characterized by production nearly twice that of consumption result- ing in a rapid build-up of uranium inventories. Low- cost production from high-grade deposits in Australia and Western Canada will gradually add another 10 to 15 million pounds U308 annually into Free World production throughout the 1980's. This latter material cannot be absorbed in further inventory build-up and can only displace higher cost production. The result is a restructuring of the Free World producer industry. United States and Eastern Canadian producers have the higher cost production which gradually will be displaced from the market during this decade. As United States production declines, United States utilities must increase their reliance on foreign supplies in order to meet their needs. This paper reviews the elements that will cause the restructuring of the Free World producer industry and the expected response of the United States utility industry to that developing situation.

Jan 1, 1982

By A. M. Tunstall

Blasting is commonly viewed separately from mechanical handling and crushing. This view is misleading because the degree of fragmentation achieved by blasting can have a significant effect on the efficiency of these processes and, hence, on the overall cost of the mining operation. In this paper, aspects of blasting and crushing and their interaction are examined. A case study is also presented that dramatically illustrates the influence of blast fragmentation on subsequent processing and on the financial implications involved.

Jan 1, 1998