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By F. Peer

This Technical Note was presented as a poster at the Western Cape Mineral Processing Symposium held in August 2001 The cleaning of fine coal (-1000 µm) in today?s coal preparation plants is an economically important factor. Coals with high ash contents are, in general, commercially undesirable. Current well-known techniques for treating fine coal include froth flotation and spirals. The primary critical factor with regards to spirals is the efficiency of the process whereas that of flotation, is the cost of there agents used. Research into enhanced gravity separation techniques has resulted in several commercially available enhanced gravity separators. This project was based on a preliminary investigation into the feasibility of one such separator, to effectively treat fine (-500 µm) coal. Experimental variables included particle size and speed of rotation of the said instrument. The performance of the separator was compared to the results obtained from liquid density separations done for the two coal fractions evaluated. From the results obtained in this preliminary study it appears that the piece of equipment investigated does not measure up to expectations. Recommendations for further investigation include the evaluation of the instrument on other South African coals to obtain conclusive results.

Jan 1, 2002

By P Knight, P A. Walker, H E. Speight

Pushback 8 South is the final cut back on the south wall of the East Pit at BHPBilliton?s Mt Whaleback iron ore mine in the Pilbara region of Western Australia. Development of the cutback commenced in 1999 and is now nearing completion with ultimate pit walls up to 300m high. This paper describes the geotechnical, structural and hydrogeological setting of PB8S, reconciliation between design and slope performance and the slope engineering techniques used to effectively manage the risks associated with the slope. These techniques include slope buttressing and sequential mining with waste backfilling, as well as a detailed program of displacement and hydrogeological monitoring, structural mapping and slope stability assessment. During the course of slope formation recent developments in remote slope displacement monitoring using radar and remote structural mapping using terrestrial photogrammetry have also been applied. Aspects of the PB8S slope management plan are relevant to many large scale open pit slopes. This paper provides geotechnical practitioners with information which may be helpful in managing geotechnical risk in similar environments.

Jan 1, 2006

By Y. Guglielmi, V. Merrien-Soukatchoff, I. Kadiri

ABSTRACT: Hydraulic experiments have been conducted since 1997 within a small fractured calcareous rock mass in southeastern France, at a site called Coaraze. On this reduced-scale site closing a floodgate located on a downstream spring produces repeated hydraulic loadings. Simultaneous measurements of normal deformations and pressure in several joints have provided a better understanding of the hydromechanical behaviour of such a fractured rock mass. The present paper first describes both the site and conceptual interpretation of the measurements performed. We showed that accurate measurement reproduction requires incorporating certain features: a variable normal joint stiffness, the joint vicinity (through introducing a Z coefficient), and the initial stress state. The paper then develops an original analytical interpretation of the coupled pressure-displacement measurements carried out, which reveal the high level of measurement suitability to the non-linear behaviours examined. 2D modelling, using the discontinuous code (UDEC) was used to proceed with the calibration step. KEY WORDS: In situ test, methodology, hydromechanics, modelling, non linear behaviour ZUSAMMENFASSUNG : Hydromechanische Experimente werden seit 1997 in einer kleinen Kalksteinmasse, das sich im Südosten von Frankreich befindet durchgeführt. In diesem kleinen Standort, werden wiederholte Wasserdruck Erhöhungen durch das Schliessen eines Hahnes produziert. Gleichzeitiger Druck und normale Verformung Meßungen in mehreren Fugen haben erlaubt, das hydromechanische Verhalten einer solche gebrochene Felsenmasse besser zu verstehen. Der Artikel beschreibt zuerst den Standort und stellt die begrifflichen Interpretationen der Meßungen vor. Um die Meßungen gut zu reproduzieren ist es wesentlich, bestimmte Faktoren wie die veränderliche normale Steifheit der Fugen, die Nachbarschaft der Fugen (über einen Z-Koeffizient) und der Spannungstand zu berücksichtigen. Der Artikel erklärt die originale Methode für die Druck- und Verformungs-Meßungen Interpretation und zeigt die gute Korrelation der Meßungen mit dem nicht-linearen angenommen Verhaltens der Fugen. Die numerische 2D-Modellierung mit dem UDEC Software ist für die Verkeilung der Faktoren gebraucht worden. SCHLÜSSELWÖRTER: In-situ-test, Methodologie, Hydromechanik, Numerische Modellierung, nicht-lineares Verhalten RESUME : Des expérimentations hydromécaniques sont conduites depuis 1997 dans un petit massif calcaire fracturé situé dans le sud de la France. Dans ce site de taille réduite des mises en charge répétées sont produites par la fermeture d'une vanne située à l'aval du site. Des mesures simultanées de déformation normale et de pression dans plusieurs joints ont permis de mieux appréhender le comportement d'un tel massif fracturé. L'article décrit dans un premier temps le site et présente les interprétations conceptuelles des mesures. Pour bien reproduire les mesures, Il est essentiel de prendre en compte certains facteurs tels que la raideur normale variable du joint, le voisinage du joint (par l'intermédiaire d'un coefficient Z), l'état de contrainte initial. L'article précise la méthode originale d'interprétation des mesures pression-déplacements qui montre la bonne adéquation aux lois de comportement non linéaire proposées. La modélisation 2D, à l'aide d'un code discontinu (UDEC) a été employée pour le calage des facteurs. MOTS-CLEFS : In-situ, méthodologie, hydromécanique, modélisation, comportement non linéaire

Jan 1, 2003

By Y. Shiraishi, Y. Sakurai

A new method, the gliding cylinder method, was proposed as a wide range viscometer for the measurements of molten salts, slags, and glasses. The method consists of two coaxial cylinders, cylindrical bob and a vessel containing a liquid sample. There is a narrow gap between bob and vessel. When the vessel moves against the bob, the generated force on the bob consists of three types of resistance: (1) Stokes’s resistance on the bob, (2) a capillary flow resistance though an annular gap between vessel and bob, and (3) lubricating resistance in a gap. The last two can be calculated on a theoretical basis but the first cannot be estimated by a simple calculation since a wall effect did not calculate easily. However, it can be assumed that the generated force depends on both the viscosity of a liquid and velocity of the vessel. Thus, the relation between viscosity and a force at desired velocity of the vessel was measured using several standard reference materials including glycerol aqueous solutions and standard reference oils. The results depended on the magnitude of the gap between the bob and the vessel. For the wider gap, it was shown that the viscosity is a linear function of a gradient of force with respect to a vessel velocity. In contrast, if the gap is small, the viscosity depends on the gradient (of force with respect to velocity). This implies that the non-linear phenomena would occur in Stokes resistance. Though detailed analysis is in a further investigation, a calibration method can be applied to determine the viscosity by this method, because good correlation was obtained among these quantities. Viscosity of molten salts, such as NaNO3and ZnCl2was measured by this method as high temperature demonstration. Keywords: viscometer, viscosity, sphere pull-up method, fused salts, molten slags, glass melts

Jan 1, 2004

Due to the reduction in frictional resistance, the characteristics of joint infill have a major role to play on rock mass instability. This paper elucidates the laboratory behaviour of graphite infilled joints based on a large-scale shear apparatus under constant normal stiffness (CNS). Discontinuities in a graphite mine have been simulated using high strength gypsum plaster, with the joints infilled with compressed graphite layers. The Fourier series was employed to characterize the joint surface, and the method of using the Fourier coefficients for the prediction of dilation and normal stress with displacement is explained. Die Charateristik von Verbindungsfüllungen hat einen wichtigen Einfluss auf Felsmassenstabilität aufgrund der Verringerung des Reibwiderstandes. Diese Veröffentlichung untersucht das Verhalten von Graphit gefüllten Verbindungen im Labormaßstab mit einer Methode die auf einem gross-umfang Apparateprinzip unter konstanter Normal-Steifheit beruht. Unregelmässigkeiten in einer Graphit Mine wurden mit Gypsum Gips von hoher Festigkeit simuliert, die Verbindungen wurden mit kompressierten Graphitschichten gefüllt. Fourier Reihen wurden angewandt um die Verbindungs Fläche zu Characterisieren. Die Methode die verwendet wurde um die Ausdehnung und Normalkraft mit der Verschiebung mit Hilfe von Fourierkoeffizienten zu bestimmen wird beschrieben. Due à diminution des résistances par frottements, les caractéristiques des joints de remplissage joue un rôle majeur sur les instabilités de la roche. Cet article étudie le comportement en laboratoire des joints de remplissage en graphite à partir d’un dispositif de friction à grande échelle sous rigidité normale constante. Les discontinuités dans une mine de graphite ont été simulées grâce à un plâtre à haute teneur en gypse, dont les joints ont été remplis de couches de graphite compressées. La caractérisation de la surface des joints a été réalisée avec les séries de Fourier. La méthode utilisant le coefficient de Fourrier pour la prédiction de la dilatation et de la compression en fonction du déplacement est également expliquée.

Jan 1, 2003

By J. Rivoirard

Historically, linear and lognormal krigings were first created to estimate the in situ mineral resources of blocks. Nonlinear geostatistics and indicator kriging were subsequently developed to evaluate also the portion recovered when applying a cut-off on selective mining units (SMUs) within blocks. In practice these methods are generally based either on the Gaussian model with a transformation generalizing the lognormal case or on the indicators above cut-offs. Very often the indicator approach is simplified by kriging separately each indicator, and when starting from a continuous variable, a practical advantage of the discretization into classes lies in the easy treatment of a zero effect and of the high values. However, a number of so-called isofactorial models have also been developed for a discrete or continuous variable, where the full cokriging of indicators (i.e. disjunctive kriging) simplifies to the separate kriging of factors. Moreover, these models are equipped with a change of support, allowing a consistent estimation of recoverable resources on SMUs. Min-Max Autocorrelation Factors (MAF) analysis of the indicators offers a new approach for indicator modelling. In particular the first factor, the one with the highest spatial continuity, can help in choosing the type of model. For example a monotonic experimental first factor can be used directly as the basis of a discrete diffusion model, unless a continuous diffusion model such as the Gaussian model can be used on the original variable. This approach is illustrated on a uranium deposit mined selectively: estimates of recoverable resources by discrete disjunctive kriging and uniform conditioning in a Gaussian model are compared locally to short-term estimates based on two areas densely drilled.

Jan 1, 2014

By A. M. Bryukhanov, A. G. Mnukhin

The report states accident rates for gassy/dusty coal mines represented as an ergatic system "man – machine - environment" with further analysis by the method of conditional probabilities. A coal mine has been analyzed with allowance for the attending personnel, equipment and environment as a sequence of events and states. Probabilities of operational states have been determined and prediction of mine behavior has been made on the basis of investigation findings for equipment and the personnel states, and analysis of the environment (i.e. mine and mining conditions). Utilization of expert estimation methods has been considered for determining major operational parameters of gassy/dusty mines. The importance of standardized values of permissible occupational risks (permissible probability of accident, PA) is demonstrated. It is also stated that a procedure is essential to determine these values, involving regular check-ups of the integral safety criterion at all mines and further development of customized recommendations for individual mines on efficient improvement of accident situations. Methodology to determine the assessment criteria has been developed and scientifically substantiated for permissible accident rates in hazardous industries.

Jan 1, 2003

By Van Sint JanM., M. Prudencio

ABSTRACT We report the results of a model-testing program to evaluate the strength characteristics of non-persistent joints. We describe the conditions under which new tensile cracks generate and propagate to connect existing joints so that the rock mass becomes fractured into several blocks, leading to a low strength. The strength of some models was equal to that along a single joint through the full sample length. In models with two joint sets, failure took place along a composite plane, partly sliding along a discontinuous joint and shearing through the intervening intact block of rock, or else by rotation and sliding of the blocks. This last failure mode could also lead to very low model strength. ZUSAMMENFASSUNG Dieser Bericht beschreibt die Ergebnisse von Versuchen mit Modellfelsmassen um den Einfluâ von unterbrochenen Rissen in ihrer Widerstandsfähigkeit zu untersuchen. Es werden die Umstände beschrieben unter denen neue Zugrisse entstehen, sich verbreiten, sich mit bestehenden Rissen verbinden und die Felsmasse in mehrere Felsblöcke zerlegen und zu einer kleinen Widerstandsfestigkeit führen. Der Widerstand einiger Versuchskörper entsprach der Festigkeit eines Risses der die ganze Länge des Versuchskörpers überquert.Versuchkörper mit zwei Rißfamilien versagten unter einer zusammegesetzten Ebene, zum Teil mit Verschiebungen nach unterbrochenen Rißebenen die sich durch Schnittversagen intakter Felsblöcke verbinden, und zum Teil durch Drehungen und Verschiebungen einzelner Felsblöcke. Die letzte Versagunsart kann zu einer stark verminderten Widerstansfähigkeit führen. RÉSUMÉ Nous présentons les résultats de quelques essais fait sur des modèles évaluant les caractéristiques de résistance des fractures discontinues. Nous décrivons les conditions sous lesquelles des nouvelles fissures de traction peuvent s’engendrer et se propager pour faire la connection avec des fractures existantes, de façon que le rocher se fracture en plusieurs blocs, menant à une résistance réduite. La résistance de quelques modèles fut égale a celle d’une fracture traversant toute la longueur du modèle. Pour les modèles ayant deux ensembles de fractures, la rupture a eu lieu sur une surface mixte, causée d’une part, par le glissement sur une fracture discontinue et d’autre part, par la rupture à travers le pont de matériel intact; ou bien par rotation et glissement des blocs. Cette dernière façon de rupture peut aussi aboutir à une très faible résistance des modèles.

Jan 1, 2003

Publications on hard rock tunnel support design in the South African mining industry have originated primarily from the goldmines during the past 50 years. Little has been published to date on the platinum and chrome mines of the Bushveld Complex. This paper covers the search for a suitable design methodology for off-reef tunnels at Impala Platinum Mine, situated on the Western Lobe of the Bushveld Complex. The fall of ground accident statistics for off-reef excavations of the mine are presented and the available rock mass quality evaluation systems are reviewed. The Q-Tunnelling Quality Index (or Q-Index) is selected because it assesses the important driving factors behind falls of ground at Impala. Two off-reef excavations are evaluated using the Q-Index, and it is shown that minor modifications are required for implementation at Impala. It will take some time before support design throughout the mine is based on the outcome of proper geotechnical investigations based on the Q-Index. Widespread implementation of such support designs should help to solve the fall of ground problem in off-reef excavations while at the same time reducing support costs.

Jan 1, 2002

The EMEM Awards of the Department of Minerals and Energy (DME) were formally launched on 3 March 2000 by Ms Susan Shabangu, Deputy Minister at the Department?s Mineralia Centre in Pretoria. The launch was attended by invited guests from the mining and aggregate industries ,representatives of the Patron Organisations (see below),non- government and scientific organizations, the media, other government departments involved with mining environmental management and members of staff of the DME both nationally and regionally.

Jan 1, 2000

By B. McCosker

The choice of the appropriate delivery process for a project is often not adequately thought about. The industry needs to be prepared to break its preconceived mind-sets on delivery procedures. Industry should also be prepared, on a project by project basis, to commit to a critical review as to how the assessment and then selection of the best procurement method can best optimize the project outcome for both client and contractor. Conventional standards and biased reliances and experienced based preferences should be challenged. To achieve this requires a paradigm shift in attitude to both the process of tendering and the evaluation of tenders. Tender and contracting practices are dynamic and have moved away from solely cost based assessments. Tendering contracts arise imposing changed duties upon owners. Traditional contract delivery models have shifted, reflected in part by the trend towards relationship contracting. The categories of contract options are not closed. Many are but hybrids of other time-tested models. This paper considers options available for any brownfield or greenfield project. The principles outlined are translatable to supply, upgrade, operation and maintenance arrangements.

Jan 1, 2002

By M. H. Rogers

Coal has been at the forefront of mankind?s drive to improve his quality of life and also for sustainable development, from the Industrial Revolution onwards. The international coal industry today is large, with some 3,7 billion tons being produced and consumed in 1997. South Africa is an important participant in the coal industry, selling some 220 million tons in 1997 of which 64 million tons were exported. It is the second-largest thermal coal exporting country in the world. Despite the size of the world coal industry, it is not immune to change. The address examines growth projections for the industry and the change drivers that will impact on it in the future. Environmental pressures, the most important of which being the climate change debate, the Kyoto Protocol arising from this debate and the development of clean coal technologies, to reduce the impact of coal production and usage on the environment are considered. Other major change drivers considered are competition from other sources of energy and that between coal producers, the deregulation of the electric power industry, corporate restructuring and for the South African producer, legislative reform. The declining (real term) coal price, the consequent squeeze on margins and the need for producers to actively contain costs is covered. Technology has, in the past, been the driver behind the growth and change of the South African coal industry and its future role in ensuring that coal is the fuel of choice for continued improvement in standards of living and economic development is addressed.

Jan 1, 1999

By M. Berger

The ‘Metallurgical Operations’ Department of Grinaker-LTA Process Engineering (GLTA) currently undertakes then primary mining as well as the re-deposition of tailings forTicor South Africa (Ticor) at their Hillendale mine near Empangeni, KwaZulu-Natal, South Africa. The mining plant, which was designed by GLTA on a Build, Own, Operate and Transfer (BOOT) basis, is capable of mining 780 000 tons per month of ROM material which is then pumped to the Primary Wet Plant for treatment by Ticor. Hydraulic mining via high pressure water cannons and subsequent transfer of the heavy mineral slurry at an RD of between 1.35 and 1.48, has never before been undertaken successfully at this level of production on an in situ reserve. The presentation will take the form of a case study in which the unique site operating conditions will be detailed and discussed, as will the innovative process and engineering solutions employed by GLTA to overcome the engineering and production challenges encountered. In order to protect the intellectual property involved in this operation, this paper is fairly general in nature, and attempts merely to provide the reader with a broad perspective understanding of the operation, and some of the difficulties encountered during the early stages of production.

Jan 1, 2003

By J. Martinovic

The large proportion of gangue minerals present in platinum bearing ores in South Africa provides challenges to the flotation and downstream processes. In order to take effective measures to reduce their recovery in flotation, an understanding of the mechanisms and factors influencing their behaviour is needed. Typical gangue minerals are pyroxene, feldspar, quartz, chromite and talc. Of these, talc is a naturally hydrophobic mineral and although it is present in relatively small quantities, it has a disproportionate effect as it has a strong froth stabilizing effect, increasing the recovery of other gangue minerals by entrainment. Talc recovery is effectively reduced with the addition of polymeric depressants. Although the other gangue minerals are assumed to be hydrophilic and their recovery by entrainment is expected to follow the water recovery, there is some evidence that they may be activated by the typical reagent suites used. Reagents such as copper sulphate, added as an activator, and collectors are used to selectively induce hydrophobicity on the sulphides. It has been shown that some of these gangue minerals can be activated. This research work investigates whether inadvertent copper activation is mineral specific and evaluates the mechanisms and factors affecting the reversal of activation with the addition of the depressants using electrokinetic measurements, adsorption and microflotation tests. Results are presented that show that the selected minerals do respond differently and that the reversal of activation is dependent on mineral type, depressant type, dosage and ionic strength of the electrolyte.

Jan 1, 2005

By J. du Plooy

Mintek has implemented a training scheme that provides students with the experiential training requirement for the National Diplomas in Chemical Engineering and Extraction Metallurgy. This note describes the main features of the scheme and the course content, and our view of future developments in this area.

Jan 1, 1998

By J. R. G. Williamson

The Mining Division of Iscor, an integrated minerals and metals company, has recently completed a feasibility study for the establishment of a new heavy minerals mine and smelter in the Richards Bay area of KwaZulu-Natal, South Africa. The mine will produce a heavy mineral concentrate containing ilmenite, zircon, rutile and leucoxene which will be beneficiated at a central processing complex close to Empangeni. The ilmenite will be smelted to produce high-grade titania slag and pig iron for export. The ancient dune containing the mineral deposit is located some distance inland of the coastal dunes, and the sands contain a high proportion of extremely fine material which must be extracted ahead of the gravity separation process. Of the 56 million tonnes to be mined annually over the ten-year life of the mine approximately 23,4%?a total of 13,1 million tonnes of minus 45 micron residue fines?will have to be disposed of in a containment facility. The origin of the fine material is from the weathering of amphibole minerals. The remaining coarse sands will be returned to the mined area to re-create the original dune configuration. A number of options for the disposal of the residue fines have been examined and specialised laboratory tests undertaken to determine the deposition behaviour of the fines. The final solution involved the use of a ?sub-aerial? technique for deposition of fine material in a disposal facility. The resulting arrangement will adequately meet technical and environmental criteria. Upon closure after 10 years of operation, the surface of the disposal facility will be returned to sugar cane cultivation The paper refers to the various options considered and describes the problems associated with competent disposal of the residue fines and the development details of the final disposal facility.

Jan 1, 1997

By E. J. M. Jahnsen, I. Jauhari, T. Badrujaman, F. A. Stober, B. O. Wasmund, L. R. Nelson, T. Miraza, J. M. A. Geldenhuis, A. Taofik Hidyat

The role of dedicated operational support in the ramp-up and stabilisation of the FeNi-II furnace for ferro-nickel production at PT Antam?s smelter located in Pomalaa, Indonesia is described. The furnace was uprated to 32MW capability in a rebuild performed in 2005. This primarily involved installing a larger transformer, coupled with adoption of HATCH water-cooled copper plate, waffle and flanker coolers with integrated metal and slag tapblocks, HATCH air-cooled copper fin lower sidewall cooling and HATCH vertical sidewall binding system ? ?holddowns?. Following a smooth commissioning period, the progress in attaining the preliminary ramp-up target load of 24MW is described. This initial target was set by Antam, subject to some prevailing smelter equipment constraints, particularly kiln capacity. Stabilisation of the furnace operation is discussed, together with some of the specific commissioning and operational challenges surmounted by the joint Antam-HATCH team. These included: ?Mastering furnace integrity monitoring and operation with copper coolers, especially metal tapblock planned maintenance and repair strategies; ?Transition from traditional ?immersed electrode? to ?brush-arc? mode of operation approaching as closely as possible to the productive ?shielded-arc? mode of operation within existing equipment constraints; ?Reductant selection and control issues; ?Utilising the sophisticated furnace monitoring to provide detailed indication and warning of potentially destructive furnace upset conditions such as Si reversion and CO boils.

Jan 1, 2007

By E. V. Lilford

The South African Minerals Development Act (?the Act?) has been promulgated and will come into full force and effect once it is gazetted. Thereafter, all Old Order mineral rights will have to be converted into New Order mineral rights within a 5-year period, probably by the end of 2008. The conversion of rights will be achieved only with the demonstrated inclusion of empowerment groups in the conversion applications. In addition to the Act, the first draft of the proposed Royalty Bill (?the Bill?) was released during the week beginning 17 March 2003. Comments on the Bill?s contents had to be submitted before 30 April 2003. The contents were to be considered in terms of applicability and acceptability to the South African minerals industry, where after proposed comments and suggested amendments were to be submitted to the relevant State Treasury office. Specifically referring to the Bill, the general response from the industry is one of concern. Since any royalty is tantamount to a tax, the general feeling is that the current mining taxation rates are already internationally competitive and to increase these effective rates, notably at differing rates depending on commodity type, will have an adverse impact on the South African mining industry. A number of these impacts can be mitigated to some degree, depending on the flexibility of the State to address the major concerns.

Jan 1, 2003

By M. Karimi

Artificial neural networks (ANNs) have found their applications in the modelling of unit operations of mineral processing plants. In this research, laboratory-scale tests were conducted, using a three-inch diameter Mozley hydrocyclone. Main parameters included pressure drop at inlet, solid per cent, vortex and apex diameter were adjusted. The corrected cut size (d50c) and the flow rates of underflow and overflow were determined. Multi layers perceptron (MLP) feed forward network architectures were designed to predict the responses. The results showed a good correlation between experimental and network output, for corrected cut size and flow rates. Keywords: hydrocyclone, artificial neural network, corrected cut size, flow rates.

Jan 1, 2010

By D. Fenn, A. du Kanda, D. Dukhan

"SynopsisGibb Consulting Services was contracted by Eskom Line Engineering Services to conduct an investigation to determine the absolute displacement to date and infer the current rate of displacement of unsurveyed colliery backfill.At the test site, where a 400 kV power line is to be constructed, neither the surface nor the backfill material had been monitored and it was not possible to state whether the surface will be subject to future settlement that may compromise surface infrastructure. Therefore indirect methods of estimating current and future displacements needed to be found to act as a proxy for a comprehensive long-term settlement monitoring exercise and provide a reasonable estimate for the settlement that has occurred in the decades of mining.The innovative solution was to recover essentially undisturbed core from backfill using a sonic drill rig and use the measured dry density values from the samples as a proxy for the rate and absolute displacement in the backfill.The success in obtaining an essentially undisturbed backfill core and the clear relationship of the backfill density with age and depth allowed the conclusion to be issued that the power line infrastructure can be constructed over the backfill; with a warning that once the water table recovers after mining ceases some collapse settlement may occur.With this method, the amount of settlement can be predicted and, if proven conclusively, provides a way to confidently release huge areas of currently waste ground for future surface infrastructural development.IntroductionIn coal mining, it is normal mining practice to backfill the newly mined-out voids with the excavated waste rock and soils. As there is no requirement for the mining companies to uniformly compact the spoil or accurately monitor surface or inter-backfill displacement, these backfilled voids are prone to differential compaction and consolidation settlement. They are therefore avoided as sites for future surface infrastructure work, especially for linear structures such as roads, railways, and power lines."

Jan 1, 2015