Search Documents

By MARK J. VANARELLI

Estimating groundwater inflows in rock deep tunnels is critical to the safety of personnel constructing the tunnel and the cost of construction. This paper presents two case studies for estimating steady-state groundwater inflows into deep rock tunnels. The case studies included the Chattahoochee and Nancy Creek tunnels. In this paper, statistical methods were applied to packer test data obtained from exploratory borings during geotechnical site investigations. A semi-empirical procedure was utilized for estimating groundwater inflows into these deep rock tunnels. It is the most widely used method/procedure in the tunnel industry. The Chattahoochee and Nancy Creek tunnels are deep rock tunnels which exhibit radial flow conditions. For the radial flow condition, a statistical analysis presented in this paper indicates that the semi-empirical procedure works well; however, variations in the procedure and/or an insufficient amount of testing could lead to underestimations of the inflow quantities. Packer test data plotted in histograms were observed in all cases to be log-normally distributed for the radial flow condition. Modeling using Monte Carlo simulations was observed to be an effective tool for removing irregularities in the distribution of the data and incorporating high-end permeability data to derive reasonable groundwater inflow estimates. This paper is based on the PhD thesis entitled “Improvements to the Current State of the Practice in Steady-State, Groundwater Inflow Estimates into Rock Tunnels based on the Application of Statistical Analysis Methods of Packer Test Data obtained from Exploratory Borings During Geotechnical Site Investigations.”

Oct 9, 2020

By P. K. Kaiser, M. Cai

When designing an efficient and effective support system for burst-prone ground, it necessary to select the most appropriate, i.e., the ‘right’ support components, including areal and reinforcement components. For this paper, it is assumed that the areal support is not the weakest link and the support performance is controlled by the rock reinforcement and holding components (bolts). We discuss the loading modes of rockbolts under static and dynamic loadings and analyze published data from laboratory and field tests. The mechanisms of energy absorption of dynamic rockbolts are presented and rockbolts are categorized based on factors such as energy absorption capacity, energy absorption rate, direct and indirect energy absorption capacities, rock mass bulking or displacement control, and shearing resistance capacity. Guidelines for selecting the ‘right’ rockbolts to build an effective rock support system for burst-prone ground are provided.

Apr 26, 2022

By M I. Pownceby, S Bhargava, F Charalambous, S McMaster, R Ram, J Tardio

"A key component of any geometallurgical investigation involves being able to predict element or mineral recoveries from simplified input data such as bulk chemistry and/or mineralogy. This relies on the metallurgist having access to accurate information regarding the chemistry of the ore and gangue minerals as well as the likely impact on processing/extraction caused by the impurities (present either as gangue or as substitutional impurities). In this study the chemical properties of two commercially important uranium minerals, brannerite (U4+Ti2O6), and uraninite (U4+O2), were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Significant levels of impurities were present in both samples with the uranium minerals deviating significantly from their ideal chemical formulae. Differences in chemistry were due to: cationic substitution decay of the uranium isotopes into radiogenic lead and other daughter products mixed uranium oxidation states post-depositional alteration.As well, the brannerite sample showed evidence of significant radiation-induced metamictisation. Leach tests to measure the ease of extraction of uranium from both samples were conducted over a wide range of conditions (temperature, acid concentration and oxidant concentration). For uraninite, the lower U dissolution rates observed in the natural sample compared to a synthetic UO2 sample were directly attributed to the presence of impurities. For brannerite, significant metamictisation of the natural sample led to enhanced U extraction rates compared to a heat treated fully crystalline sample. This study highlights the importance of detailed mineralogical characterisation studies in any uranium process mineralogy investigation as the compositional, textural and microstructural aspects of the main uranium phases present will likely play an important role in any process to extract uranium.CITATION:Ram, R, Charalambous, F, McMaster, S, Pownceby, M I, Tardio, J and Bhargava, S, 2013. Chemical and microstructural characterisation studies on naturally occurring uranium minerals - implications for processing, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013, pp 325-334 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 29, 2013

By D. Mireku-Gyimah, R. S. Suglo

Ghana contains auriferous belts which cover 51 800 km2 of its small area of 239 400 km2. From 1493 to 1600 35.5% of the world gold production was from the Gold Coast (renamed Ghana in 1957). This dropped to 8.9% from 1701-1800. For the past fifteen years annual production has averaged less than 2% of the world total. By 1985 only four gold mines were operating, compared with 45 in 1934 and 11 in 1945. Since 1987 Ghana has experienced a boom in gold mining activities. By 1991, 83 new companies had acquired prospecting licences. At least five new companies have started large-scale production. About 650 licensed small-scale mining groups are in operation. The economic and technological factors that have contributed to the decline of gold production in Ghana are discussed. A summary is given of the methods used to mine and recover gold. These cover small-scale workings, dredging, open cast operations and underground mining. The advantages and disadvantages of these technologies and the future of gold mining in Ghana are considered.

Jan 4, 1993

By Seth Robertson, Daniel Belardo, Travis Coleman

Thermal Integrity Profiling (TIP) is a non-destructive method used to evaluate drilled deep foundation integrity. This integrity testing method is specified more frequently, and is becoming an industry standard in the transportation and private construction sectors. This testing method utilizes heat generated during the concrete/grout curing process to assess deep foundation integrity over the evaluated length. With compilation of the measured temperature versus time and installation records, a model of the Effective Average Radius versus measurement depth is generated. The generated effective shaft model is highly dependent on specific construction details, subjective modeling parameters, and proper interpretation of concrete/soil heat dissipation characteristics. Key components of the TIP analysis include both qualitative and quantitative assessments. Qualitatively, variations or sharp reductions in temperature profiles may indicate potential anomalous regions. Quantitatively, a correlation is established between measured temperatures and estimated Effective Radii for subsequent integrity evaluation. Best practices in processing the TIP measurements are presented, including selecting the optimal time for analysis, normalizing the thermal profile, and proper interpretation of potential anomalous regions. Recommendations for implementing mitigation efforts and interpretation of the TIP results are presented.

Sep 8, 2021

By Jürgen F. Brune, SAMUEL A. LOLON, ADITYA JUGANDA, Gregory E. Bogin Jr

Historically, there have been many occurrences ofmine fires and explosions recorded in the United States and other countries that have demonstrated the existence of explosivemethane–airmixtures, herein referred to as explosive gas zones (EGZs). The risk of mine explosions can increase if the EGZs migrate out from the gob into the surrounding mine entries. Fluctuating barometric pressure is the common cause for EGZs outflowing or outgassing from the gob. Numerical analysis using a 3D computational fluid dynamics method was developed to fully understand the outgassing phenomenon. A number of simulations using various magnitudes and periods of barometric pressure changes indicated that the EGZ outgassing potentially occurs due to lags in pressure, which are strongly influenced by mine conditions and ventilation systems. An early warning system with a real-time pressure monitoring and the application of gob ventilation boreholes are recommended to detect and mitigate explosion hazards from gob outgassing.

Aug 24, 2020

By G. M. Scamans

In the past ten years there has been considerable penetration of aluminum automotive body sheet (ABS) into automotive structures. The exponential increase in demand is resulting in major investments in heat treatment and finishing capacity across the globe. Line speed and tonnage throughput is limited by the continuous heat treatment (CHT) floater furnace rather than the cleaning and pretreatment section where electrolytic treatments that offer higher line speeds should come into favour and roll coating of pretreatment should predominate. The capacity limiting surface texturing pass will either be eliminated or moved to the finishing line or a dedicated mill. The key to making aluminum both embedded carbon and cost competitive with steel for more and more affordable classes of vehicles lies in recycling of both prompt scrap and, in the longer term, end of life vehicle scrap. For the first time scrap separation technology is available that can compete effectively with hand sorting and can sort aluminum shredded vehicle scrap into wrought and cast alloys and then into individual alloy groups. The challenge is to use more end of life scrap in alloy formulation whilst at the same time extending the property range in terms of both strength and formability.

Jan 1, 2015

By Christopher B. Kapes

To reduce concentrate dewatering and drying costs, the Concentrator Division at Phelps Dodge Morenci, Inc. investigated available filtration technologies. Numerous methods were explored, including: drum, disk, belt, pressure, hyperbaric, and ceramic media filtration. An economic evaluation of the individual filtration technologies indicated the advantages of ceramic media filtration for Morenci concentrates. This paper discusses the technological development culminating in the first full scale application of ceramic media disk filters in North America. Low moisture contents are obtained at high production rates and greatly reduced operating costs.

Jan 1, 1994

By Lawrence Devon Smith

"This paper examines the impact of the various assumptions that go into an economic evaluation, and shows how these can be combined to show an exciting result that may not really exist. An example of an embellished case (the kind that one frequently sees when projects are being promoted) is developed and the cumulative impact is analysed to show the actual project underneath. The paper also points out some areas to watch for overly optimistic assumptions such as prices, inflation, and debt. The concept of a ""bare bones"" base case is proposed (constant metal prices, constant dollars, no inflation, no debt, no interest, on a project basis, after tax) as a common reference point.As well, the discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.INTRODUCTIONOften, the first time that all of the technical and economic data for a mineral project comes together in one place is when the economic evaluation is developed. This typically happens when work on the project has progressed to a sufficient level of detail that the effort to produce a year-by-year cash flow is justified, usually at the pre-feasibility or feasibility study stage. The data involved will include:• production; tonnes waste and ore mined, ore grade, mining recovery, metallurgical recovery, metal sold• revenue; metal price, smelting & refining charges, marketing costs• operating Costs; mining, milling, administration, fees, royalties• capital Costs; exploration, development, construction, indirect costs (engineering, management), contingencies, start-up, inventories, working capital, replacement and sustaining capital, closure costs• taxes and royalties• exclusions; depreciation (this is not a cash item), sunk costs (only costs going forward)."

Jan 1, 2003

By Muhammad Zia-ur Rehman, Sajjad Ahmad Baig, Gao Lei Fu, Muhammad Mohsin, Sobia Naseem

The environmental sustainability is linked back to human sustainability; the sustainability development comprises the environment, society, and economics. This study mainly focused on mining sustainability and its impact on the environment of Pakistan. For measuring the level and environmental mining sustainability nature to Environmental Impact Assessment (EIA) of the world’s second largest salt mine “Khewra,” Folchi and Phillips environmental sustainability mathematics (PESM) models are applied. The results indicated that Khewra was deemed to be potentially sustainable for the environment and quality of salt. The results suggest the delicate balance of maintaining sustainability successfully, regarding the mining process in Pakistan which has been affecting the local environment and community so badly. The paper lays emphasis on the potential significance of the model’s application for the attainment of sustainable mining goal. This study is essential for researchers,

May 11, 2020

By George Saratsis, George Exadaktylos

In the marbel industry, ore reserves refer to the produced tonnage of orthogonal prismatic, defect-free blocks of commercial sizes and of marketable aesthetical quality. On the contrary, in the mining sector, ore reserves refer to the tonnage of ore with grade above some cut-off value. While in the mining sector ore reserves are reported according to existing standard guidelines, the marble industry has no standardmethod. The purpose of this paper is to present a method to estimate white marble reserves using drill coring or borehole wall logging and limited joint mapping on exposed marble surfaces. Data pertaining to fracture orientation, fracture frequency, size, and whiteness were collected. The primary phase of marble characterization is followed by the discretization of the orebody into a three-dimensional array of orthogonal prismatic blocks, where the marble whiteness and fracture intensity are attribute values. Both these variables are considered to obey continuous and not discrete probability distributions. The discretization is performed using computer aided design and the Block Kriging techniques. An outline to improve the description of a given marble ore deposit at the exploration stage is presented for the prediction of marble block size distribution from joint count measurements along diamond drill cores. An example case of a white dolomitic marble quarry is used to demonstrate these methods.

May 27, 2020

By Richard Hamburger

Calculating machines permit the use of the more rapid cotangent and semigraphic solutions of plane triangulation. The results of these methods are as accurate as those of other methods. Simple adjustment of the net, and ease of calculation encourage more complete field work. Errors in field work or in computation are easily localized.

Jan 1, 1950

By T. J. Otto, G. C. Lindeque

Productivity is improved by increasing the ratio of output to input. In an operating open-pit mine, improving the productivity of heavy mining equipment (HME) enables the unit cost of production to be reduced. To optimize HME productivity, the Kolomela open-pit iron ore mine transitioned to an enhanced short-term mine planning (STMP) process that supports the application of a manufacturing-type operating model. At the core of the enhanced STMP process is a focus on integration across the open-pit mining value chain. The interdependencies between mining activities are highlighted and emphasized, thus ensuring that mining activities are synchronized. The improvements related to HME productivity were monitored from 2019 to 2020. The utilization of mining area in the Leeuwfontein pit improved from 71% to 90%, and the blasting frequency reduced by 14% while the average blast size increased by 17%. The distance travelled during shovel relocations between mining phases reduced by 16%, and the lost time associated with drills relocating reduced by 53%. These productivity improvements resulted in an 11% increase in the loading rate of the main waste shovel at Kolomela from 0.9 Mt/month in 2019 to 1.0 Mt/month in 2020. The enhanced STMP process can be adapted to other open-pit mining operations.

Nov 1, 2021

By A. F. van der Merwe, R-D. Taylor, M. Jacobs, F. H. Conradie

Total bound moisture (TBM) is a typical quality indicator of industrial-grade gypsum. This gypsum is comprised of three distinct phases, namely anhydrite, dihydrate, and hemihydrate, of which only the latter is of much industrial use. TBM analysis is a lengthy laboratory procedure, and an artificial neural network (ANN) TBM inference measurement is proposed as a fast and online alternative. An ANN inference model for gypsum TBM based on plant data was developed. The inputs to the network were primarily focused on the plant's calciner, and different network topologies, data divisions, and transfer functions were investigated. Furthermore, the applicability of the TBM value as a quality indicator was investigated based on a gypsum phase analysis. A strong correlation between TBM and the gypsum hemihydrate and anhydrite content was found, validating the plant target TBM of 5.8% as a quality indicator. A network topology consisting of one hidden layer with logarithmic-sigmoid (logsig) and pure linear (purelin) transfer functions showed the best performance (R > 90%).

Oct 3, 2023

By D K. Weatherley, G R. Ballantyne, S Ali, M Yahyaei, M S. Powell

This paper explores development of a novel ore characterisation method for the precise measurement of practical minimum comminution energy. A monolayer of particles with a narrow size distribution is broken using a precision rolls crusher (PRC); an ore characterisation device developed to overcome the shortcomings of conventional tests. For energy measurement, PRC uses two shaftmounted rotary torque transducers. These transducers acquire precise torque and angular speed data in response to the load applied to the rotating shafts during breakage events, which is converted into energy. The test progressively crushes feed particles down to final product size in many controlled breakage stages. The generation of fines in each breakage stage is then plotted as a function of input energy. The inverse of the gradient of this plot provides the size specific energy (SSE) in kWh/t of material generated below a predefined marker size; -75 μm in this case. The PRC has potential to evolve as a geometallurgical ore characterisation test—it is simple, fast, requires small sample mass (200–300 g), covers a wide feed particle size range (10 mm to 115 µm), and provides ideal SSE measurements that can be used for the calibration of on-site production equipment.

Aug 24, 2022

By I Govender, T L. Moodley

Tumbling mills are grossly inefficient, using only 5 per cent of the total energy supplied for actual breakage. A significant proportion of this inefficiency is unavoidable owing to geometric limitations; rotating drum systems are prone to exhibiting certain regions (energy barriers) that resist particle entry thereby restricting the transfer of energy. Though such systems are inherently inefficient, improved modelling schemes may lead to slightly enhanced efficiency through better microscale predictions of key breakage drivers (stress, force). Central to achieving such incremental advances is the development of a universally accepted rheology for dense granular flows. Armed with a better understanding of these macro-scale ingredients, classical process modelling offers an efficient, spreadsheet friendly framework for recovering the spatial distributions of the comminution drivers. At this real-time level of process control, it should be possible to tune comminution operations towards more energy efficient configurations – the ultimate goal of this research. The present work employs validated DEM data to recover the full continuum field which will ultimately serve as a basis for calibrating process model outputs based on different rheological hypotheses. Such a continuumbased approach captures tensor properties like the shear stress and strain rate – both of which are necessary to developing a dense granular rheology. Moreover, DEM captures this data at the momentum transfer timescale of 10-6 s – no other measurement technique is capable of this level of spatial and temporal resolution. Importantly, the confidence in this DEM data is strengthened because it has been validated at the continuum scale using Positron Emission Particle Tracking (PEPT) kinematic measurements. Validated DEM data is derived from batch experiments conducted within a 300 mm ID laboratory drum using three and five millimetre glass beads at 60 and 75 percent critical speed; such mill speeds are typically encountered in the tumbling mill industry. Dimensional analysis is conducted using critical rheological parameters (shear rate, shear stress, granular temperature etc), which are key to not only developing a granular rheology but ultimately will be used to tune our mechanistic models.

Aug 24, 2022

By Henry Kreisinger, L. P. BRECKENRIDGE, WALTER T. RAY

The investigations of fuels conducted by the technologic branch of the United States Geological Survey had their inception at the Louisiana Purchase Exposition in 1904. By an act approved Febru- ary 18, 1904, Congress authorized the work of analyzing and testing at the Louisiana Purchase Exposition the coals and lignites of the United States, under the supervision of the Director of the United States Geological Survey. An appropriation of $30,000 was made for this purpose. In the general deficiency bill dated April 27, 1904, the sum of $30,000 was added to the appropriation. To carry out these investigations the Director of the Geological Survey appointed a committee consisting of E. W. Parker, statistician of the Geological Survey; Joseph A. Holmes, State geologist of North Carolina; and Marius R. Campbell, a geologist of the Geological Survey. Under the first act authorizing this work all of the machinery and coal for the tests was to be furnished the Government free of charge. The buildings containing the testing apparatus were all paid for out of the first appropriation. After the close of the Louisiana Purchase Exposition every Congress made an appropriation for continuing these fuel tests. These subsequent appropriations permitted the purchase of appliances better adapted for the testing work.

Jan 1, 1912

By N Weerasekara, M Bird, M Yahyaei, M M. Hilden, M S. Powell, J Franke, P Toor

The combination of new tools with a more rigorous approach to understanding the interaction of mill liners with overall mill performance and economics, forms the basis of an integrated approach to liner management. Based on accurate liner wear measurements, some (limited) physical mill inspections and surveys, accurate calibration of the mill load and analysis of process data, a whole new approach to liner selection, relining intervals and mill control is proposed. Collection and analysis of this information in operating mills illustrates the mill performance improvement which can be attained through this careful measurement and modelling approach.A more holistic approach to liner management is proposed, including a broadening of the current work to cover the potential benefits of improved relining technologies and predictive liner wear modelling. CITATION:Powell, M S, Hilden, M M, Weerasekara, N, Yahyaei, M, Toor, P, Franke, J and Bird, M, 2012. A more holistic view of mill liner management, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 95-104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By J. P. Nicoud

"The Frog's Leg project is located in the Kundana mining centre 22 kms West of Kalgoorlie, in Western Australia. The Mines and Resources Australia (MRA) Dioro Exploration Joint Venture has had considerable exploration success centred on the high grade Frog's Leg discovery. A gold resource of 930,000 ounces has been defined. At Frog's Leg there have been three discrete resource domains recognised - Supergene, Contact, and Quartz Lodes. This paper describes the metallurgical test work undertaken.The selection of the drill core was a joint effort by the MRA Senior Geologist and Mineral Engineering Technical Services (METS) to ensure the samples were representative of the ore body. Optimisation of gold recovery was essential as both the Contact and Quartz Lodes have exceptionally high percentages of free gold as well as significantly higher grades than the typical open pit ores found in Western Australia. The metallurgical scope of work included documenting all of the metallurgical test results, establishing the comminution characteristics, determining the percentage of gravity recoverable gold, evaluating the cyanide leach characteristics and determining the tailings characteristics. These studies were used as the basis of flow sheet design to treat both ores and to discuss the advantages and disadvantages of alternative flowsheets. Investigations also included toll milling options at various plants as well as second hand and transportable plants. Considerable technical effort has been put into ore characterisation by way of test work aimed at managing the process risk at each stage of project development, including mitigation. MRA also carried out detailed mineralogical analysis of the ores."

Jan 1, 2005

By C. A. D' Odorico

The zinc pressure leaching (ZPL) plant at Teck Cominco's Trail Operations was started up in 1981 and represented the world's first commercialization of the technology. From the outset, the process was designed to operate using iron-rich Sullivan Mine zinc concentrate. When the Sullivan Mine reached the end of its life in 2002, the ZPL plant underwent a significant process change with the treatment of 100% Red Dog zinc concentrate. Through careful improvements to existing plant processes, controlled changes to plant operating parameters and a rapid adjustment to the modified process by operations personnel, the plant has been successfully converted to processing a feed of 100% Red Dog zinc concentrate. This paper discusses the challenges faced during the conversion and describes the modifications to plant operating procedures, as well as changes to plant processes.

Jan 1, 2004