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By T. Imgrund, A. Bischoff, S. Spürk

"Specific conditions of underground coal mines at great depth, such as high temperatures, high rates of methane inflow and natural ventilation pressure provide considerable challenges for the reliable design of appropriate mine ventilation systems. For decades coal mining in Germany has coped with these extreme circumstances. Based on these experiences appropriate software tools for simulating mine ventilation networks have been developed and continuously enhanced. This paper examines differences in the simulation results and underlying calculation methods of two software solutions. The analysis is based on the comparison of FlowNetTM and VentSim DesignTM (Version 5.1) regarding the accurate prediction of fluid mechanical quantities and their validation with real measurements. A special focus lies on exceptional ventilation scenarios typical for deep coal mines, like gas inflows, fire events and buoyancy effects. The purpose of the comparison is the future utilization of the experiences gained during mining at up to 1,500 m depth for state of the art ventilation design. INTRODUCTION Ventilation is an essential component of mine operations—as providing fresh air to workplaces, diluting and removing explosive, toxic or asphyxiating pollutants and assuring sufficient climate conditions. On the other hand, the costs of ventilation contribute to a large extend to the overall operating costs of a mine, as the share in the energy consumption of a mine may be in the range of 25–50% (Belle, 2008). Accordingly, proper design of ventilation systems has been a task since early times. Consequently software for modelling of ventilation networks has been developed in order to improve efficiency and accuracy of calculations (Maleki, 2018). Compressible flow has not been considered by initial ventilation modelling software tools. In Germany, the consideration of changes in airflow density—depending on pressure and temperature—in the algorithms of ventilation simulation software has been started in 1974 by Duepre & Hofbauer. This development had been continued by the Pruefstelle fuer Grubenbewetterung (Test Centre for Mine Ventilation) and resulted in the release of a computer ventilation software named “Wetter”. The mine inspectorate of the German state of North Rhine-Westphalia, which supervises the major coal mining district in Germany, declared ventilation simulation based on compressible flow being “state of the art” in 1985 (Pollak, 1985). This pronouncement made allowance for assessing the consequences of underground fires and downtimes of main fans based on advanced software solutions."

Jan 1, 2019

By R. Castro, R. Gómez, F. Betancourt, M. Moncada

In block cave mining, rock fragmentation is a key parameter that influences the production level design and mine planning. Fragmentation occurs mainly by natural breakage during the caving process and in the draw column. The breakage that occurs within the column is known as secondary fragmentation. Secondary fragmentation has been successfully described using the block caving comminution model, which replicates the fragmentation mechanics between particles under drawn and vertical loads in a draw column. This model is based on a kinetic and population balance approach, in which non-normalized and normalized assumptions can be used depending on material and comminution system behaviour. In this paper, the non-normalized and normalized approaches are applied and compared to laboratory data to determine which assumption should be used for secondary breakage in block caving. Approaches are compared graphically, with the mean square error and the Fisher test with a false-rejection probability of 0.05. Based on a statistical analysis, the results show that the normalized model can be applied to all the rock types tested.

Nov 1, 2021

By R. Codell, D. L. Hughson

While benchmarking the integrated finite-volume code MULTIFLO against the analytical solution of Philip et al. (1989) for cylindrical underground openings, we found numerical simulation of dripping threshold flux consistently higher than the analytical solution for both rectangular and unstructured grids. The magnitude of error is proportional to the alpha parameter characterizing capillarity. This may bias estimates of repository performance towards non-conservatism.

Jan 1, 2000

By Saravarim A.

"The aim in flotation systems is to control the grade and recovery of the product., numerical method or sampling and analysis is used to achieve this goal. Weakness of measuring instruments, lack of process knowledge, deficiencies in management and data processing in the control of flotation cells, has led the academic and industrial units to use numerical models. In this regard, using the results obtained from the experimental design carried out in the DTP line of Gol Gohar industrial and mining complex, a regression model was developed based on the analysis of variance. To present this model, after variance analysis of factors and interactions, all models were investigated and the final model was created based on 75% of the data. The model was tested with the remaining 25% of the data to confirm the goodness of the fit. The coefficient of determination for training and testing resulted 71% and 74%. Moreover, a feed forward back propagation neural network with different layers and neuron was used to model the results. The best network structure was 6-27-1 and the coefficient of determination for this network was 99% and 98% for training and test respectively. Given the complexity of neural network models and the relatively low accuracy of the regression model, neural network has a priority assuming we have access to a specialist. In addition, the results obtained from neural network can be used as expert systems to control and optimize the flotation cells.INTRODUCTIONThe primary objective of the flotation cell control is to maintain the product's (in this case tailing) recovery and grade, which represents the index for process efficiency and product quality. Continuous estimation of these indexes requires a significant amount of maintenance, and calibration of the continuous analyzers, in order to maintain an acceptable level of accuracy. Weakness of measurement equipment, lack of process knowledge and the general deficiency in management and processing of data in the flotation cell control, will lead industrial units to use smart methods such as mathematical models, regression and neural networks in near future (Panahi, Abdollahzadeh, & Sam, 2010). Artificial neural networks are inspired by the very complex structure of human brain in which millions of nerve cells solve problems or store information by communicating with each other. The duty of neural networks learning. It should be noted that learning in artificial neural networks is limited, and what is practically considered is the computing power of the network. A neural network consists of units called neurons, and has the capacity to handle a set of input data to produce a desired output data set. Each of these input and output data sets can be assumed as a vector (Soltanmohammadi & Noparast, 2006)."

Jan 1, 2016

By Matthew John M. Krane, Christopher J. Vreeman, J. David Schloz

"A continuum mixture model of the direct chill casting process is used to model the transport phenomena and solidification behavior in the Direct Chill casting of an Al - 6 wt% Cu billet using Wagstaffs AirslipTM process. The model, which includes the transport of free-floating solid particles, can simulate the effect of a grain refiner on macrosegregation and fluid flow. Numerical predictions of sump profiles and composition and temperature fields are presented. Two 45 cm diameter billets were cast under production conditions with and without grain refiner. Temperature and composition measurements and sump profiles are compared to the numerical results. The comparison shows excellent agreement for the grain refined case. It is believed that an incorrect model assumption prevents good agreement in the non-grain refined billet. IntroductionDirect chill casting is a semi-continuous process in which molten aluminum enters the top of a water-cooled mold, is cooled, and forms a solid ingot drawn out below (Figure l(b)). The molten aluminum begins to solidify due to the cooling effect of the mold wall. As the ingot is withdrawn from the bottom of the mold, water jets impinge on the surface, directly cooling the billet and forming a solid layer around a liquid melt, commonly referred to as the sump.A particular defect that occurs in a wide range of casting processes, including the direct chill (DC) casting of aluminum alloys, is macrosegregation, the uncontrolled redistribution of alloying elements on the scale of the ingot during solidification. Macrosegregation in DC cast ingots can produce non-uniform mechanical properties [l], which affects the behavior of the metal during downstream forming and heat treat operations."

Jan 1, 2001

By M N. Mian

The Cayeli volcanogenic massive sulphide deposit is located in Black Sea region of Turkey. Cayeli Bakir Isletmeleri (CBI) was formed as a joint venture between Inmet (Canada) and Eti Holding (Turkey). CBI is processing complex copper/zinc sulphide ores. The Cayeli concentrator was commissioned in 1994, with a design capacity of 600 000 tonnes/year. The grinding circuit was a classical rod mill/ball mill combination. The rod mill was converted to a primary ball mill in May 1997. The reasons for conversion were to use mill power more efficiently and eliminate feed interruptions during rod charging. The grinding circuit now has a primary ball mill in open circuit, and a secondary ball mill in closed circuit with hydrocyclones. Classification was originally done in two stages with hydrocyclones. Both mill discharges were combined and pumped to a primary cyclopack having two, 500 mm diameter cyclones. Primary cyclone overflow was pumped to a secondary cyclopack for further classification. The secondary cyclopack had ten, 200 mm cyclones. Both unit underflows were fed to a secondary ball mill by gravity. The secondary cyclone overflow, typically 62-64 per cent passing 36 ¦m, at around 42 per cent solids (w/w) was fed to flotation circuit. In order to increase circuit capacity to 1 000 000 tonnes/year and to improve control over the grinding circuit, it was decided to convert the classification circuit from two stage to one stage. For this purpose, six Warman Cavex cyclones having 400 mm diameter were installed. Now, the combined primary and secondary ball mill discharge was classified in single stage with the Warman cyclones in closed circuit with the secondary ball mill. The cyclone overflow goes directly to the copper rougher circuit as flotation feed. The grinding circuit is producing a flotation feed of 70 per cent passing 36 ¦m. The change over to single stage classification at Cayeli was successful. A mill throughput of 1 000 000 tonne/year is being achieved with better control over classification, and improved grind size. Results and comparison between the two classification circuits are presented in the paper.

Jan 1, 2003

By J. West

For many years line-of-sight (LOS) issues for underground mobile equipment is a growing focus of research. This research is a result of the numerous fatalities and injuries which occur in the mining industry and which are related to poor operator LOS. Three assessment methods are currently used to assess operator LOS of underground mobile equipment. The light filament (LF) method is a hands-on assessment method that is performed in the field. This method is not evaluated in this paper. The laser scan (LS) method of assessing equipment is a quick and reliable method that comes from the need to evaluate vehicles already located in the field. The computer simulation (CS) method can assess LOS issues using a computer aided drawing (CAD) model, which is useful for assessing current or prototype models. The purpose of the current research is to compare and validate different operator LOS assessment methods. Comparison of the results of the LS and CS visibility plots yielded similar quantifiable results. A visual comparison of the results further illustrate that the LS and CS methods are acceptable assessment tools for mobile equipment operator LOS evaluation. The visibility assessment methods are now being prepared as guidelines for the mining industry to assess current and potential designs.

Jan 1, 2007

By J. West

For many years line-of-sight (LOS) issues for underground mobile equipment is a growing focus of research. This research is a result of the numerous fatalities and injuries which occur in the mining industry and which are related to poor operator LOS. Three assessment methods are currently used to assess operator LOS of underground mobile equipment. The light filament (LF) method is a hands-on assessment method that is performed in the field. This method is not evaluated in this paper. The laser scan (LS) method of assessing equipment is a quick and reliable method that comes from the need to evaluate vehicles already located in the field. The computer simulation (CS) method can assess LOS issues using a computer aided drawing (CAD) model, which is useful for assessing current or prototype models. The purpose of the current research is to compare and validate different operator LOS assessment methods. Comparison of the results of the LS and CS visibility plots yielded similar quantifiable results. A visual comparison of the results further illustrate that the LS and CS methods are acceptable assessment tools for mobile equipment operator LOS evaluation. The visibility assessment methods are now being prepared as guidelines for the mining industry to assess current and potential designs.

Jan 1, 2007

Ilmenite production in Western Australia commenced in 1956. There are now five producers, all in the Bunbury-Capel district, and current total production capacity is about 450,000 t.p.a.The deposits occur near the surface and average between 10 and 50 per cent heavy mineral. About 70-85 per cent of the heavy mineral is ilmenite. Other heavy minerals present include leucoxene, zircon, rutile, monazite, and garnet. The ilmenite contains 52-60 per cent Ti02. and is very low in chromium (0·03-0·04 per cent CrS03)Mining is done by sluicing, drag line excavation, or dredging. Primary concentration of the heavy minerals is achieved by spirals, revolving cones, or Reichert cones. After drying and screening, ilmenite is separated from the heavy mineral concentrate by various types of magnetic separator.Separate leucoxene, zircon, rutile, and monazite concentrates are also produced. Each plant uses a different technique and the processes used include chemical attritioning, screen plate electrostatic separation, high tension rolls, air tables, and dry launders.INTRODUCTIONThe treatment of beach sands in the Bunbury/Capel area for the extraction of ilmenite is a very recent development in the mining industry in Western Australia. Nevertheless, since the commencement of production in 1956, ilmenite has become the sixth most important mineral produced (Table 1).The increasing world recognition of Western Australia as a major producer of ilmenite (Table 2) is due primarily to the low chromic bxide content of the mineral (0' 03-0' 04 per cent Cr203), combined with a medium to high titanium dioxide content (54-60 per cent Ti02), supported by large reserves, a stable government, and close access to good shipping facilities. Ilmenite is. produced from these deposits at low cost which enables the industry to compete on world markets despite high rates for sea freights because of the distance from major markets.

Jan 1, 1965

By David Meadows, John Starkey

"As part of the ongoing project development for the Tenke Fungurume Copper-Cobalt Project in the Democratic Republic of Congo, Phelps Dodge Corporation has examined methodologies for determining the size of grinding mills to support a 7000 mtpd operation. Six samples were tested by Hazen Research, Inc. (HRI) to obtain the JK parameters using the JK Drop Weight Test, standard Bond crushing, and rod mill work indices, abrasion indices and by Dawson for Bond Ball Mill Work Index tests using crushed feed, and Standard Autogenous Grinding Design (SAGDesign) Tests, patented by Outokumpu. (See reference 8 below).The comparison of these results gives context to how the various measurements relate to each other and how they can be used to obtain an accurate design for the grinding mills required for the Tenke Project. This is the first published direct comparison between JK Drop Weight, standard bond work indices, and SAGDesign test results. The SAGDesign test includes a SAG test followed by a Bond BM Wi test done on SAG ground material.INTRODUCTIONAfter the presentation of the paper “SAGDesign Testing – What It Is and Why It Works” at the recently concluded SAG 2006 Conference in Vancouver, a question was asked about how SAGDesign ore hardness measurements compared with other comminution tests, specifically the JK Drop Weight Test and the parameters that are derived from such testing. At that time it was noted that a paper was being prepared for the CMP Conference in January to show how various ore hardness measurements compare with each other when done on the same samples.This paper will therefore present the first such comparison using test results from the Phelps Dodge Tenke Fungurume Project where six composite samples were examined by the tests noted below. A seventh sample was tested at Dawson but not at other labs. The tests were done at four different laboratories listed below and included the tests shown."

Jan 1, 2007

By K. Biswas, S. Iverson, S. J. Jung

Computer modeling of rock flow in ore passes is being investigated and compared using MSC Soft-ware’s Working Model 2D1 (WM2D) and Itasca Corp.’s Particle Flow Code in Two Dimensions (PFC2D). This work is being carried out by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health to determine the usefulness of computer modeling to improve ore pass design. The types of tests included pendulum tests to validate WM2D simulations and simulated single-rock drop tests in both WM2D and PFC2D to understand their contact models. Simulated rock impacts at the ore pass chute and the use of inclined ore passes and doglegs were investigated in both programs. A PFC2D simulation showed that dynamic loads at the chute gate were reduced significantly when a dogleg transition was used, and simulations in which the ore pass was inclined showed significant reductions in chute impact loads compared to simulations of a vertical ore pass. A released hang-up was simulated using PFC2D.

By Elaine Ellingham, Francis T. Manns

"The Orostar and Scadding were two small gold mines owned and operated by Orofino Resources Limited. Conventional statistical treatment indicates an identical arithmetic mean grade of 0.22 oz/T Au for both mineable reserves. Further, the deposits are both shown to have cut weighted average reserve grade of 0.21 oz/T. Orostar mined out at 0.206 oz/T and Scadding at 0.156 oz/T Au. The combined exploration and development database contained 1394 fire assays, more than enough for statistical confidence in a normal distribution. Therefore this study was initiated to determine, if possible, why the mill head grades were lower than the averages and to experiment with several methods to determine whether a reliable statistical mill head grade estimation method would emerge. Despite the identical reserve grades, distinct differences in the grade distribution histograms are present. By studying the arithmetic and log-normal grade distributions, with some attention to South African practices, this paper reports on those differences which may account for the considerable divergence in the mill head grades. Furthermore, this study casts considerable doubt on the industry standard method of cut weighted averages.The global mill head grades of the two deposits have been derived from the arithmetic average grades by graphic means. This precise method of mill head grade prediction, if applied to complex orebodies, could permit selective grade control and result in direct cost savings by allowing the operator to detect false value stopes, benches or levels and emphasize reliable regions of not only gold mines, but also uranium or base metal deposits."

Jan 1, 1992

By Alan Mayton, Bertrand Valero, Christopher Jobes, Farid Amirouche

Exposure to vibration induced in and around underground mine’s exploration is a major concern to vehicles operators. Most of these drivers over time develop serious spinal musculoskeletal and discs problems causing low back injuries. The first purpose of this paper is to analyze the performance and dynamic response of driver/operator when subjected to different levels of vibration due to rough road conditions depicted in a mine field. The second purpose of the paper is to quantify the energy transmission in the presence of seat padding with special characteristics and active suspension. Using experimental testing data collected at NIOSH/PRL (National Institute for Occupational Safety and Health/ Pittsburgh Research Laboratory) along with model simulation algorithms developed at the University of Illinois at Chicago we investigated how acceleration transfer functions as well as absorbed power affects the different parts of the body. To this end, we used a previously validated human model which includes the head, torso segments and legs. The connective forces between body segments were modeled through modal analysis techniques from previous experimental data at the UIC Vehicle Technology Laboratory. The absorbed power and energy transmitted to the body are used as an index measure to assess the viability of the different seat padding’s and active seat suspension control strategies.

By James Warner, Peggy Ganse, Glen Smoak, Raymond Henn, Sam Bandimere

Over the past several decades, cement-based grouts using ultrafine cement as are placement for portland cement have begun to gain acceptance as an alternative to chemical solution grouts, however the amount of information currently available on these grouts is limited. For this reason, the authors developed a field testing program to evaluate the penetration capabilities of various ultrafine cement grout mixes. The tests were conducted by injecting sand columns using different portland and ultrafine based grouts, the measuring penetration distances after applying equal injection pressure for the same time period. Results of tests performed in 1999 and 2000 are discussed herein.

Jan 1, 2001

By F. Hassani, R. Mikaeil, B. Ferdowsi

Two analytical solutions for estimating the ovaling deformation and forces in circular tunnels are widely used in engineering practice, due to soil-structure interaction under seismic loading. This paper discusses the discrepancy between the two analytical and finite difference methods. A comparison of the two analytical methods shows that the calculated forces and displacements are identical for the condition of full-slip between the tunnel lining and ground. However, the calculated lining thrusts differ by an order of magnitude when considering no-slip between the tunnel lining and the ground. The analytical solutions are compared to numerical analyses of the no-slip condition using the finite difference method to validate which of the two methods provide the correct method. To achieve the goal, numerical modelling, field data of the Kuhin railway tunnel and Manjil earthquake characteristics are used. Numerical analysis results agree with one of the analytical solutions that provides a higher estimate of the thrust on the tunnel lining, thus highlighting the limitation of the other analytical solution.

Jan 1, 2008

By Leonardo Gonçalves Pedroti, Fernando de Paula Cardoso, Beatryz Cardoso Mendes, Afonso Ramos Garcez de Azevedo

This work aims to produce paints using granite waste, as a pigment, and compare their performance to soil pigments based paints, in terms of hiding power and abrasion resistance. Initially, the residue and soils were physically, mineralogically and morphologically characterized. For the production of the paint samples, an experimental model was defined, based on the variation of the proportions of pigment and resin. The proportion of water varied in each sample, in order to maintain the viscosity within a range considered ideal for application. Sequentially, tests were done to determine the hiding power and abrasion resistance of inks. It was found that, in comparison to soil paints, the granite residue paints presented greater hiding power. This result can be explained by the characteristics of the granite residue, which allowed a high nonvolatile content in the mixtures. With respect to abrasion resistance, granite residue paints showed less resistance than soil paints, possibly due to the granulometry of the residue that resulted in a greater roughness of film. In addition, none ink sample satisfied the minimum specifications prescribed in the Brazilian standards for hiding power and abrasion resistance, at the same time. This means that these inks, when used, will require more repair and repainting over time than conventional paints.

Mar 1, 2018

By Morteza Gharouni Nik

Flexible Dilatometer Test (FDT) is one of the in-situ test methods for determining the deformational characteristics of rock masses. In this study, several dilatometer tests have been conducted in different geotechnical phases of site investigations by means of two types of FDTs. The purpose of this paper is comparison of the performance of these two types of dilatometers and analysis of the differences in the results of the tests.

Jan 1, 2008

By M. Kuchta, S. Iverson

INTRODUCTION Underground blasting with perimeter damage control can reduce the requirement for loose rock scaling and reduce the risk of ground-fall injury. In previous work Johnson and associates (2010) from the National Institute for Occupational Safety and Health (NIOSH) developed a rock blasting perimeter damage and control design method included in the DRIFT software tool (NIOSH, 2018). This blast design software tool utilizes current methods of perimeter blasting with the added design element of a buffer row coordinated with the perimeter row to reduce perimeter damage. The coordination is in applying one of several blast damage models to calculate the damage extent for each production, buffer, and perimeter blast hole in the design. The calculated damage is then applied to the spacing between the blast holes. The basis of the buffer row design is the practical damage limit and is supported in this paper with computer models of signature blasts and full blast rounds using PFC2D (Itasca Consulting Group, Inc., 2018). Practical damage limit The practical damage radius (Rd) is not to be confused with burden. The practical damage extends toward the burden side and inward into the rock mass. For all practical purposes, the practical damage radius equals one half the burden (Hustrulid, 1999). The maximum extent of radial crack damage around a blast hole (Rcrack) and the maximum extent of radial crushing damage (Rcrush) are illustrated in Figure 1. A “practical” radius of damage (Rd) lies between the crushing limit and the cracking limit. The “practical” damage means that if the rock mass lying outside of the practical damage circle were removed, the rock remaining within the circle would easily break apart. Blast pressure and strain Work by Johnson (2010) and associates included signature blast tests in large concrete blocks. A signature blast test in concrete as exampled by strain data in Figure 2 was designed to monitor the dynamic strain at incremental distances from a single fully coupled blast hole, measure crushing and radial cracking extent by wire-sawing to expose the damage, and relate the damage to overbreak that is common in underground blasting. The initial slope or rising strain as the stress wave passes by the strain gages shows very high strain and strain rates close to the single blast hole. Since the derivative of strain versus time is strain rate, a line tangent to each of the strain curves at the maximum strain rate is drawn and the strain rates identified. The high strain rates were then plotted on a semi-log in Figure 3 to show a linear trend. The strain rate is greater than 100 s-1 within 20 cm from the blast hole for the signature blast experiment. The strain rate at the blast hole wall is projected to be 300 s-1. Figure 4 illustrates the damage in the NIOSH block exposed by a wire saw cut.

Jan 1, 2019

By H. M. Stewart, N. F. Dawson, J. P. Beukes, P. G. van Zyl, Q. P. Campbell, A. Jordaan, R. I. Glastonbury, L. N. Sadiki

"SynopsisThe physical properties of oxidative sintered pellets produced from typical South African UG2 ore are compared with the physical properties of pellets produced with conventional South African metallurgical-grade chromite ore (from the Lower Group 6 or the Middle Group 1 and 2 seams). A statistical evaluation of the cured (sintered) compressive strengths proved that pellets prepared from UG2 ore are likely to have the same, or better, compressive strength than pellets prepared from metallurgical-grade chromite ore. The cured abrasion strength of the UG2 pellets was also superior to that of the metallurgical-grade pellets. Scanning electron microscopy (SEM) backscatter, secondary electron, and elemental X-ray mapping were used to determine the reasons for the general superior strength of the UG2 pellets. The case study UG2 ore also required 13 kWh/t less energy for milling to attain the required particle size distribution prior to pelletization, which can lead to substantial cost savings. Results presented in this paper can be utilized by ferrochromium (FeCr) producers to better quantify the advantages and disadvantages associated with the use of UG2 ore for FeCr production.IntroductionChromite, a mineral of the spinel group, is the only commercially viable source of virgin chromium units. Geologically, commercial chromite deposits in the world are found in three forms, i.e. alluvial-, podiform-, and stratiform-type deposits (Murthy et al., 2011; Cramer et al., 2004). Alluvial deposits were formed by weathering of chromite-bearing rock with the subsequent release of chromite and gravity concentration by flowing water. However, these deposits are relatively small and of comparatively minor commercial interest. Podiform-type chromite deposits usually occur as irregularly shaped pods or lenses, and their distribution within a mineralized zone is usually relatively erratic and unpredictable, making the exploration of these deposits difficult and costly (Cramer et al., 2004). Stratiform-type chromite deposits occur as parallel seams in large, layered igneous rock complexes with more regular layering and lateral continuity (Cramer et al., 2004). The largest example of a stratiformtype chromite deposit is the Bushveld Complex (BC) in South Africa, which holds an estimated three-quarters of the world’s viable chromite ore resources (Cramer et al., 2004).Several chromite seams exist in the BC. The seams of economic interest are the Lower Group 6 (LG6), the Middle Group 1 and 2 (MG1 and 2), and the Upper Group 2 (UG2) seams (Cramer et al., 2004). The LG and MG seams are specifically exploited for their chromium content, while the UG2 seam is mined primarily as a source of platinum group minerals (PGMs) (Xiao and Laplante 2004). Extraction of the PGMs from the UG2 ore usually involves the liberation of the sulphide by milling and subsequent recovery of the PGM concentrate through flotation (Xiao and Laplante, 2004). Chromite in the PGM concentrate is undesirable; therefore, PGM recovery circuits are specifically designed to ensure maximum rejection of the chromite to the tailings stream. However, the chromite in the PGM tailings can potentially serve as feedstock for ferrochrome (FeCr) production, after beneficiation to increase the chromium content."

Jan 1, 2015

By Andrew Port, Ali Ghandeharioon

Nonlinear seismic deformation analyses using the finite difference program FLAC were performed for a wastewater treatment plant to estimate foundation displacement and performance of two proposed trickling filters during the 2475-year event design earthquake. The effective stress based constitutive model UBCSAND, which captures the cyclic behavior of both the “sand-like” and “clay-like” materials, was used to model the dynamic response of the soil strata. Dynamic analyses of the site indicated that in absence of ground improvement or deep foundations beneath the proposed trickling filters, those structures would undergo horizontal displacements in excess of 1 m and short-term differential settlement gradient of about 400 mm over 50 m as a result of seismic and post-seismic settlements. Three mitigation options were considered for limiting the seismic displacements and differential settlement gradients of the proposed trickling filters. These alternatives include vibro-replacement stone columns, vibro-replacement stone columns plus supplementary cutter soil mixing (CSM) configurations, and pile foundations. Various layouts for each mitigation option were considered including the lateral extent of the ground improvement, CSM walls and pile spacing. Seismic horizontal and vertical displacements of the proposed structures as well as post-earthquake consolidation settlements due to dissipation of excess pore water pressures in soil layers were assessed in all the analysis alternatives. The analyses indicate that all the alternatives considered have the potential to provide a comparable level of seismic and post-seismic performance. However, for similar performance levels, the ground improvement options need to extend well beyond the edges of the proposed structures, while the piles can be limited to just beneath the footprint of the structures. INTRODUCTION Annacis Island Wastewater Treatment Plant (AIWWTP) is owned and operated by Greater Vancouver Sewerage and Drainage District and services a population of approximately 1 million people in Vancouver, British Columbia. Wastewater is generated by residential, commercial, and industrial sectors and the treated effluent is discharged to Annieville Channel of Fraser River on the south side of Annacis Island. AIWWTP is located on a 51-hectare site and was commissioned in 1975 as a primary treatment plant, but has had two major expansions to meet the population growth needs, and to improve the treatment process efficiency through the provision of secondary treatment of the liquid stream. The current expansion includes construction of additional solids contact tanks and secondary clarifiers. Future expansions include the construction of proposed additional trickling filters. New expansion structures are required to be designed for post-seismic operation after the 2475-year event design earthquake.

Jan 1, 2018