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By Z-P. Song, Z-B. Jiang, A-N. Jiang

"In deep excavations under conditions of high ground stress, even hard rock undergoes creep and other time-dependent effects that may result in instability. This study involves an analysis of the typical damage to the surrounding rock in the deep tunnels of the Jinchuan nickel mine in China. In order to understand the creep mechanism, triaxial creep laboratory tests were conducted under high stress. The creep characteristic curves and the Nishihara model parameters of typical rock were obtained from these tests. The numerical simulations, with which the creep model is developed, were performed using Flac3D. The creep model parameters were back-analysed on the basis of field monitoring data. Finally, appropriate support schemes for deep tunnels are suggested. The creep deformation of rock increases with time and axial load. At the same load level, the creep deformation of unloading is greater than that of loading. The simulated deformations of the surrounding rock are coincident with those from in situ monitoring, indicating the applicability of the presented rock creep model in situations of high ground stress. The results constitute a reference for support design in deep mining tunnels.IntroductionThe excavation of underground caverns can alter the natural stress field of the surrounding rock. In deep engineering projects under conditions of high ground stress, even hard rock shows obvious creep properties and time effects (Yao, 2005; Liu, 1994). The time effect of excavation not only causes decompression of the floor and increases sidewall stress, but also leads to stress concentration at the corners of the excavation, which influences the stability of the surrounding rock in a very complex manner.Many researchers have studied the creep properties of rock. ‘Griggs (1939) showed that creep occurs in sandstone, shale, and silty sandstone rock under the load of 12.5%–80% of the failure load.’ Subsequently, much research has been published on rock creep tests, including the uniaxial compressive creep test, the triaxial compressive creep test, the discontinuity rock shearing test, and field tests (Wawersik, 1974; Amadei et al., 1980; Okubo et al., 1991; Jin et al.,1995). A rheological model is used to describe the complex rheological deformation of material. This model is based on various fundamental parameters including rock elasticity, plasticity, and viscous properties, which can be combined into a constitutive model to reflect the rheological properties of various types of rocks. Wang et al. (2014) studied the creep– damage–rupture characteristics of rock salt by applying a creep-damage model. Munson (1997) developed a multi-mechanism constitutive model of creep of polycrystalline rock salt based on steady-state creep and modified it to incorporate transient creep through work hardening and recovery. An elasto-viscoplastic approach was developed to simulate the timedependent nature of the fracture zone (Malan, 1999). Rheological models were proposed to understand the collapse of iron ore mines in Lorraine by Dragan et al. (2003)."

Jan 1, 2016

By C. Kirmanli

The purpose of this paper is to develop an expert system for hydraulic excavator and truck selection in surface mining. Hydraulic excavators and trucks are finding increasing applications in mining operations. Hydraulic excavators are extensively used especially when bringing electricity to rural areas is difficult and for small-scale mining. This paper describes an expert system, which selects the optimum hydraulic excavator truck configuration such that unit production cost is minimized and technical constraints such as geological, geotechnical and mining constraints are satisfied. The system has four modules: user interface, rules and an methods, databases and output module. The expert system in this study is developed within KappaPC shell. It supports object-orientated technology for the MS Windows environment. The software provides a very useful tool to practitioners, saving time and cost. Equipment selection is a recurring and expensive problem of mine planning and often involves interdisciplinary experts from different fields. It is very difficult and expensive to bring together all these experts. The capabilities of the expert system developed are illustrated in the paper. The software overcomes the difficulties of selecting the proper equipment for surface mining operations, which is very important, and results in substantial savings. Equipment databases for hydraulic excavators with 15-59 yd3 capacities and trucks with 35-360 tons are constructed and these databases are used to select the proper configuration. A case study is carried out for Soma Surface Coal mines in Turkey. Keywords: surface mining, expert systems, equipment selection, hydraulic excavators, diggability

Jan 1, 2009

By El-Sayed M. Sherif, J. D. Comins, Erasmus R. M.

Corrosion of copper in aerated acidic chloride pickling (0.5 M HCl) solutions and its inhibition by 3-amino-1,2,4-triazole-5-thiol (ATT) have been investigated using electrochemical techniques and weight-loss measurements, along with Raman spectroscopy. Electrochemical measurements for copper after varied immersion periods of 0, 24 and 48h showed that the presence of ATT and the increase of its concentration significantly decrease cathodic, anodic, corrosion (jCorr) currents and corrosion rates (KCorr), as well as the dissolution currents at 300 mV vs. Ag/AgCl, while increase polarization resistance (Rp), degree of surface coverage (?) and inhibition efficiency (IE%) to a great extent. Weight-loss measurements after different immersion periods of 6 ~ 48h revealed that the dissolution of copper decreased to a minimum and the corresponding IE% increased with ATT concentration increases. The detection of ATT molecules on the copper surface by Raman spectroscopy indicated that inhibition of copper corrosion is achieved by strong adsorption of ATT molecules onto the copper surface. Aerated acidic pickling solutions; 3-Amino-1,2,4-triazole-5-thiol; Copper corrosion; Corrosion inhibition; Raman spectroscopy

Jan 1, 2006

By B. Z. Weiss, N. R. Comins, F. Blum

The effect of microstructure on the deformation and fracture properties of 3CR12 steel was investigated at different strain rates in the temperature range -196 to 200°C. The yield stress of the as-received steel, showing a banded dual-phase microstructure, was much lower than that of the flake-like dual-phase microstructure produced by heat treatment. The heat treatment also resulted in an increase in the volume fraction of martensite. The fracture toughness of the as-received 3CR12, on the other hand, was significantly higher than that of the heat-treated material. These changes in both yield stress and fracture toughness were attributed to the effect of microstructural parameters on the constraints imposed on the deformation and subsequent failure of the ferritic phase in the as received and heat-treated steels. The exceptionally low resistance to crack extension in a plane parallel to the roiling plane of the as-received material was ascribed to the delamination process, which is typical for controlled-rolled steels. The yield stress and fracture toughness were found to depend on temperature and strain rate. The appearances of the fracture surfaces were found to be consistent with the mechanical properties.

Jan 1, 1992

By T.R. Stacey

Physical testing of rock support for rockbursting conditions has been carried out for over 40 years. A review of this testing shows that it has been mostly component based, rather than actually testing support systems. Further, it is concluded that none of the testing is truly representative of rockburst loading in a similitude sense. Similitude conditions are not achievable, mainly because the real conditions in a rockburst event, such as seismic source location and magnitude, wave frequencies, amplitudes, and interactions, are not all known. Because such information is not available, and because the results of all testing carried out to date have not been able to define, for support design purposes, the capacity of support systems, ongoing physical testing of rockburst support systems is essential. It is essential that the test should simulate, or actually take place in, a supported rock excavation. A rock support system is a combination of individual support components that work together to retain and contain the rock. In doing this, the components are subjected to loading by the rock and to interactive loading between one component and another. It is necessary to prove the capacity of such rockburst support systems by subjecting them to severe loading, as in direct blasting. The direct blasting approach, pioneered more than 40 years ago, probably still provides the greatest validity as a significant test of rockburst support capabilities, even though it does not simulate a rockburst. Direct blast testing of rockburst support systems in a surface environment, such as in a quarry or on exposed rock cutting surfaces, could represent a practical development of the approach, facilitating the execution and monitoring of tests.

Jan 1, 2012

By D. Burrows

Traditionally, characterisation of the mineralogy and textures of ore and rock samples were based on observations of hand specimens and thin sections using an optical microscope. The extent of the data collection was limited by the available tools and thus variations in mineralogy and texture were generally not described by quantitative data. These qualitative to semi-quantitative approaches, even though well established over the years, resulted in variable observations and data sets. The data were unlikely to be representative of a sample and limited statistical validity meant the results could not be reliably used in modern digital mining design and planning. With recently developed SEM based quantitative mineralogy tools and the corresponding methodologies, ore textures can be quantified and compared numerically. The numerical data can not only enhance the understanding of an orebody in geological terms, but can also be used in the creation of metallurgical models for mine and mineral processing design and simulation. These capabilities provide valuable inputs to risk assessment studies and the evaluation of mineral projects.

Jan 1, 2007

By J. Manchisi

Laboratory investigations were conducted to establish the feasibility of bioleaching a mixed copper oxide/sulphide rougher concentrate from Nchanga Mine on the Zambian Copperbelt. The objective was to determine the kinetics and extent of copper extraction for this material. Batch experiments were conducted under different solution conditions in stirred tank bioreactors. The progress of (bio)leaching was monitored through measurements of soluble ferrous and ferric iron, copper, pH, and redox potentials, while bacterial activity was monitored online through 02 and C02 gas utilization rates. About 20 per cent copper was solubilized within 2 hours in all cases of non-oxidative (abiotic), oxidative (abiotic), and bioleaching experiments. This was attributed to the dissolution of mainly copper oxides. Subsequently, bioleaching experiments resulted in an overall copper extraction of 93 per cent, with up to 8 g.L-1 copper after six leaching days, compared to 58 per cent copper extraction in the abiotic oxidative acid leaching experiments. However, there was little effect of time (i.e. poor dissolution kinetics) on copper recovery for abiotic non-oxidative acid leaching of the material. Hence, the rate of sulphide leaching increased due to the activity of bacteria. Thus, the material is potentially bioleachable under mesophilic conditions. However, more exhaustive test work needs to be conducted to establish the effect of bioleaching variables and heat requirement.

Jan 1, 2012

By I. Beukes, H. Kotze, B. Krause, R. P. Hattingh

Hillendale Mine is operated by Exxaro KZN Sands, and is situated on the north coast of KwaZulu-Natal in South Africa near the towns of Empangeni and Richards Bay, some 200 km north of Durban. During the mining operation the heavy minerals rutile, ilmenite, zircon and leucoxene are extracted for further beneficiation at a processing complex near the town of Empangeni. The deposit contains approximately 25% slimes (defined as the sub-45 micron fraction), and is mined using hydraulic monitoring. Run of mine is gravity fed down launders to pump stations, which deliver the material to a primary wet plant. Slimes is separated from the run of mine prior to the heavy minerals being separated from the sand. Sand tails containing approximately 2-5% slimes is pumped to the mining void. The slimes is thickened to a density of approximately 1.2, and most of the resultant material is pumped to a sub-aerial deposition site (residue dam). The area is characterized by an annual rainfall of approximately 1300 mm, which is relatively high by South African standards. From an agricultural perspective the soils are deep and well weathered. Dryland agriculture has been practised on an extensive scale in the area for the past 70 years. Sugar cane in particular is cultivated on and around the mine area. In terms of environmental approvals, the post-mining land use and objectives are defined as economically viable and sustainable sugar cane cultivation in the mined areas. During mining the soil profile is destroyed. In this paper the establishment of a reconstituted soil profile is discussed, with specific reference to the methodology that is being followed to achieve the homogeneous blending of sand and slimes. Defining the rehabilitation strategy and soil specification Strategically Exxaro KZN Sands divided rehabilitation into four aspects, comprising physical rehabilitation (restoration of soil structure), vegetative rehabilitation (restoration of vegetative cover), ecological rehabilitation (restoration of sustainable ecological communities), and sustainability (sustainable man/environment interface) (Hattingh and Viljoen, 2006). It is believed that the key to successful rehabilitation lies in achieving a substrate (soil) suitable for the establishment of the target vegetation. During the development of the rehabilitation strategy the key factor in the establishment of a suitable soil profile was shown to be the soil water retention of this material. Since dryland agriculture is practised, this aspect becomes critically important in ensuring that the post-mining land use is sustainable (Hattingh et al., in prep.). From a financial perspective, a closure certificate being issued implies that the state takes over financial liability for the rehabilitated land. This has significant implications for the state-the default position will be that all possible latent and residual impacts must be identified and known prior to a closure certificate being issued. From the mine's perspective this precautionary approach by the state implies that post-operational costs cannot be quantified exactly, and our approach is therefore to mitigate the risk of a long post-closure care and maintenance phase by means of addressing all potential latent defects during the operational rehabilitation phase. The financial viability of the soil reconstitution process itself is therefore not measured against other rehabilitation methods, but against the risk of not achieving closure. During a series of technical workshops comprising experts in the various disciplines in the rehabilitation of the soil profile were identified. These aspects include the re-establishment of a functional soil profile, soil physical characteristics, soil chemistry, soil biota, salinization potential, erodibility and soil weathering. The natural soils in the Hillendale area have been classified in terms of the South African soil classification system (MacVicar and co-workers, 1991) and consist of Hutton (orthic topsoils on red apedal subsoils) and Clovelly (orthic top soils on yellow apedal subsoils) soil forms. The topsoils consistently comprise medium to fine grained sand overlying heavier textured sandy clay loam to clayey subsoils. The topsoil structure consists of a single grain structure, whereas subsoils are apedal. These soils are typically deeply weathered and do not show secondary structures. During the mining process a layer of topsoil (300 mm) is stripped off, and the balance of the material down to the footwall is processed. Sand with 2-5% slimes (defined as the sub-45 micron fraction) is returned as backfill in order to re-establish the dune to approximate the previous landform. From an agricultural perspective this material is not suitable for the dryland cultivation of sugar cane. A capping of more suitable material therefore has to be provided. The most significant difference between the premining soil form and the backfill material is the percentage slimes, consequently a mixture of the sand and slimes is required as a capping over the backfilled sand. The required thickness of the cap is a function of specifically plant growth requirements, erodibility, weathering and runoff (Hattingh, et al.; in prep.). The percentage slimes required in the cap is a function of mainly soil water requirements (Hattingh and Viljoen, 2006). The conservative indications to date show that the reconstituted soil profile should consist of a homogeneously blended mixture of 70%-80% sand and 30%-20% slimes up to a maximum of 2 metres thick. This will be sufficient to ensure growth during dry periods.

Jan 1, 2007

By E. -U. Reuther

To improve the climatic environment underground the German coal mining industry has installed refrigerators with a capacity of 300 MW cooling power. One third of this total is accounted for by central refrigeration plants with more than 5 MW capacity. The central refrigeration comprises three stages: mechanical cooling, transport and distribution of chilled water via pipelines and exchange of heat in the air coolers. Of these three stages only the mechanical generation of chilled water has been resolved satisfactorily. Transport (including distribution) and exchange require further technical research. The Mining Institute of the Aachen University of Technology has done extensive studies on this subject, concentrating on controlling the flow of chilled water according to demand in the mine. Additionally, the favourable exchange in the air coolers is taken into account. The studies are based on a model mine which simulates the conditions in deep coal mines in Germany. The simulation program represents firstly the condition of the mine air at the location of the air being cooled, then the heat exchange in the air cooler itself, and finally the transport of the chilled water from the central refrigerator to the consumer. The program also reproduces the seasonal and operational changes in conditions of mine air as well as different air cooler designs. A regulated distribution of chilled water is also suggested. Finally, estimations of costs can be made as an aid for further planning.

Jan 1, 1987

By C. Musingwini, T. C. Sebutsoe

"The primary objective of any mining business unit is to make profit by extracting, processing, and selling minerals from a particular mineral deposit. It is important to optimize extraction of the mineral resource given time, capital, and space constraints. Mineral extraction is often associated with uncertainty due to variable technical and human factors. Technical factors such as grade distribution, ground conditions, and equipment reliability influence the performance of a mining production system (MPS). The performance of the MPS is also impacted by human factors such as employee skills, health, and attendance. Uncertainty associated with technical and human factors often leads to actual output differing from what was planned. Therefore an in-depth analysis of the significant causes of deviations from the planned outcomes is relevant.In this paper we investigate the empirical relationships between inputs and outputs in a MPS in order to assist management in directing efforts at key production drivers. Once a MPS has been empirically characterized, more effort and resources can be focused on the key decision-making variables (DMVs) in order to meet the planned outcomes.For a typical underground, tabular, narrow-reef conventional drill-andblast platinum mine the face advance, face length mined, number of teams, team efficiencies, and team size have a statistically significant relationship with the centares (m²) produced, which is a key performance indicator (KPI). The production function derived in this study can be used to align the physical, technical, and human factors together to predict the optimal output level. The most significant production lever of the MPS is the face advance. IntroductionA mining production system (MPS) is a result of an iterative process of design, planning, and optimization of mining input variables and decision-making variables (DMVs). The MPS exists within the mineral extraction link of the complete mining value chain. It represents the stage where mining companies have the opportunity, through production, to start generating returns on the investments undertaken. Returns on shareholders’ investments can be realized at this stage."

Jan 1, 2017

By S. J. Bluhm

Recommendations are given for the design of multi-stage spray chambers in which air flows horizontally through water sprays. A detailed description is given of one such spray chamber at Hartebeestfontein gold mine that is used for bulk cooling of the incoming ventilation air, and that has been constructed according to these recommendations. A method for predicting the performance parameters of horizontal multi-stage spray chambers is given, and the method is illustrated with some examples. The method is equally applicable to spray chambers in which the water, rather than the air, is cooled.

Jan 1, 1979

The exciting history of gold mining in South Africa haR been told in many different ways - in books, plays, and films, and on radio. But now, there's a new and far more lively way to find out about it and that is by actually participating in living history. Your invitation to go back in time will not take you much further from the centre of Johannesburg than the late-afternoon stretch of the shadows of the skyscrapers. The Gold Mine Museum - a new venture by the Chamber of Mines - brings back all the colour and romance of mining a century ago, and reminders of some of the hardships too. This is not an ordinary museum, but one of the most modem attempts in the world to make the past come to life.

Jan 1, 1980

By R. D. Lama

This paper presents the results of a study of the mechanics of methane gas flow in coal. Desorption tests carried out on cylindrical coal specimens showed that an analytical formulation can be made to model the process of gas flow in coal based on an integration of Darcy's law, Fick's law and Langmuir's relation. The diffusivity term in the flow equation varies directly with local gas content. Permeability tests carried out on the same coal result in permeability constants with values higher than equivalent permeabilities obtained from desorption tests by many orders of magnitude. The study also revealed that permeability is highly dependent on the applied gas pressure and the rock stress.

Jan 1, 1987

By C. L. de Jongh

The number and scale of backfilling operations in the South African gold mining industry have grown rapidly in recent years. The application of backfilling as a means of stope support in a wide range of geological conditions and mining systems has resulted in the development of a variety of alternative fill systems. Experience gained in the evaluation of operating fill systems has contributed to a knowledge of the essential concepts to be considered in their design. This knowledge can also influence management's perception of what is expected of a backfilling system. The factors to be assessed in stating and satisfying these objectives are examined. The areas of investigation cover the selection of a suitable material, its preparation, distribution and placement, and the engineering logistics involved in the management of such a system. Finally, the integration of a filling system with an existing mining operation is examined.

Jan 1, 1988

The kinetics of adsorption of gold di-cyanide onto activated carbon has been investigated extensively over the past two decades. These studies have demonstrated that both film and intra-particle mass transfer affect the kinetics. The dominant mechanism of intra-particle mass transfer has not yet been identified. In the work described, surface diffusion and pore diffusion are considered as possible rate-determining mechanisms of intra-particle mass transfer. Mathematical models are described that incorporate film mass transfer and the respective intra-particle mass transfer mechanism with equilibrium described by a Freundlich isotherm. Rate constants of film mass transfer and pore or surface diffusivities were estimated by the fitting of the respective models to experimental carbon adsorption data. The estimated pore diffusivities, after they had been corrected for the porosity and tortuosity of the carbon, were found in most instances to be higher than the molecular diffusivity of dilute gold di-cyanide in aqueous solution. This situation is not physically viable. The surface diffusion mechanism acting in parallel with the pore-diffusion mechanism is thus responsible for the intra-particle transportation of most of the gold.

Jan 1, 1996

The mining rock-mass rating (MAMA) classification system was introduced in 1974 as a development of the CSIA geomechanics classification system to cater for diverse mining situations. The fundamental difference was the recognition that in situ rock-mass ratings (AMA) had to be adjusted according to the mining environment so that the final ratings (MAMA) could be used for mine design. The adjustment parameters are weathering, mining-induced stresses, joint orientation, and blasting effects. It is also possible to use the ratings (AMA) in the determination of empirical rock-mass strength (AMS) and then in the application of the adjustments to arrive at a design rock-mass strength (DAMS). This classification system is versatile, and the rock-mass rating (AMA), the mining rock-mass rating (MAMA), and the design rock-mass strength (DAMS) provide good guidelines for the purposes of mine design. However, in some cases a more detailed investigation may be required, in which case greater attention is paid to specific parameters of the system. Narrow and weak geological features that are continuous within and beyond the stope or pillar must be identified and rated separately. The paper describes the procedure required to arrive at the ratings, and presents practical examples of the application of the system to mine design.

Jan 1, 1990

By R. S. Sarracino, M. J. Louw, S. M. Vather

Two detonation models, IDeX for ideal VOD and CPeX for non-ideal VOD, were used to predict the velocities of detonation (VOD) of five explosives: ANFO, a bulk emulsion, and three repumpable emulsions (R100 Gold, R100 Diamond, and R105). The theoretical VODs were compared with the in-hole VODs of the explosives, and the predicted and actual values were found to be within experimental error for ANFO and the bulk emulsion. The results were not consistent for the repumpable emulsions. The discrepancies can be explained as being due to variations in mining and loading practices. The results show that the detonation models can be effective tools in predicting the behaviour of explosives in different diameters and rock confinements, provided that the user is aware of the factors that can affect the optimal usage of explosives and equipment.

Jan 1, 1993

By R. G. B. Pickering, H. H. Haase

Few innovations in the South African gold mining industry could have a more significant impact on improving profitability than non-explosive methods of mining. The far-reaching benefits of this approach are explained and the progress made through development work funded by the industry is described. Three methods are considered: impact ripping, sloting with abrasive waterjets and diamond saws, and breaking from drilled holes with waterguns and electric pulses. Of these methods, impact ripping is the most advanced and requires only minor refinements before production applications can be initiated. Although this method, based on current performance, is expected to yield considerably increased profits, it is predicted that it could perform several times better than at present with further development. The other methods of rockbreaking also show potential. Waterguns and electric rockbreaking would be attractive in unfractured rock for difficult geological conditions, and for confined areas such as gullies and development ends. Methods based on sloting could be combined with any of the other methods to enhance their effectiveness and thus yield further improvements in profitability; also, they could be used to advantage in specific applications. Al the discussed methods, therefore, deserve to be developed further.

Jan 1, 1991

By F. H. Deist, J. P. E. Morris, E. Georgiadis

For some years the Collieries Research Laboratory of the Chamber of Mines of South Africa has been engaged in the development and application of computer programmes to aid in the solution of rock mechanics problems. It is the purpose of this paper to introduce some of the programmes having general applicability. A system capable of predicting stresses and displacements induced by large-scale tabular excavations is discussed. A finite element programme especially designed for handling layered continuum problems, and which is being used extensively has been supplemented by an automatic mesh generation facility that reduces problem preparation times considerably. Some typical applications of these programmes are described. An entirely new approach, potentially capable of performing linear three-dimensional continuum analysis at practical cost is introduced.

By B. Mienie, J. F. Morrison, C. H. Wyndham, M. J. Martinson, N. B. Strydom

Contribution to discussion M. J. Martinson (Associate Member)*: Application of the simple selection test mentioned in the penultimate paragraph of the paper (reference to a more detailed description of the test would not have been inappropriate) should assist South African mining engineers to make more efficient and possibly more humane use of available labour. The authors mention that the test 'is in use in the gold mining industry', and it would be interesting to know the extent of this usage in terms either of number of mines or as a percentage of the total number of labourers employed on 'heavy' tasks. The paper would have been of greater interest had the authors attempted to relate their findings to the statistics of labour usage in gold mines, members of the Chamber, and to the 'heavy' tasks in particular. On this the authors confine themselves in their Introduction to the somewhat ambiguous statement that 'A relatively high proportion of the 360,000 Bantu mine labourers are employed underground on manual tasks'. To appreciate the practical significance of the authors' work one needs a detailed breakdown of the underground labour force by occupations, together with estimates of quantities such as: (a) total stope and development tonnages moved manually per shift: by shovelling by shovel/tram by tramming together with distances and any other relevant data; (b) theoretical energy expenditures required to accomplish (a); (c) actual energy expenditures required to a accomplish (a); (d) energy theoretically available to accomplish (a) based on 50 per cent of the total maximum oxygen intakes of the labour force allocated to these tasks. Analyses of this sort on an industry basis might demarcate the more promising areas for detailed investigation. Stress is often laid on the need for increased mechanisation to increase stope productivity, but it may be questioned if enough is known about the characteristics, performance and potential of our underground labour force to warrant blind acceptance of stope mechanization as the industry's panacea. Provided that health and safety are not compromised, the ultimate yardstick for assessing any form of stoping is profitability; obviously the industry must investigate very thoroughly any form of mechanization which might reasonably be expected to increase profitability, but it should also be remembered that a radical overhaul of existing systems-which have after all evolved by trial and error over the past 75

Jan 11, 1968