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By P. I. Page

In mineral exploration the place that yields the first significant result is marked and two questions are posed immediately. Where should the next sample be drawn and how big should it be? At present the answers are arbitrary and ad hoc. They depend on personal experience and sentiment?that is hunch. The thought processes involved in reaching the decisions are unsatisfactory and unsatisfying for professionals. This paper proposes guidance on choosing sample spacing and sample size. The guidance is obtained from the grades of the samples. The grades also imply the extent of influence of each sample assay. Thus sampling and assay are integrated. The integration is achieved by changing the unit of value in which assays and grades are expressed and by exposing meanings and functions of grade beyond that of measuring rock value. The proposals are extended to guide comminution of particle size in sample size reduction and to deal with the problem of erratic high assays. Also, elucidation becomes possible of the computation of a reliable figure for average grade as a statistical weighted mean.

Jan 1, 2005

By L. Mabiza

Keywords: Pyrometallurgy, furnace, sulphur, SO2, off-gas, Zimplats Zimplats embarked on an off-gas sampling campaign in December 2009 to characterise the concentration of SO2 in the off-gas from their 13 MW furnace. In excess of forty isokinetic samples (US EPA Method 8) were taken over seven days. The aim of the sampling campaign was to increase the understanding of factors that influence sulphur release from sulphide concentrates in an electric furnace. Specifically, detailed monitoring was conducted over various operating conditions to evaluate: ? The relationship between SO2 and feed rate (i.e. furnace power) ? The relationship between SO2 and ingress (i.e. furnace freeboard pressure) ? The impact of concentrate bed thickness on SO2 (i.e. blacktop) ? The effect of events such as tapping and converter slag return on SO2 ? The desulphurization reactions that take place in the blacktop A model was developed to predict the SO2 content in furnace off-gas for a particular set of operating conditions. In order to evaluate the impact of random, uncorrelated changes in concentrate composition, ingress and power (feed rate) on the SO2 content of the off-gas, a Monte Carlo approach was adopted whereby concentrate composition, power, and ingress were allowed to vary randomly around selected set-points. The model is primarily based on the release of ?labile? sulphur from the partial thermal dissociation of sulphide minerals with an over-stoichiometric sulphur content (e.g., Fe7S8 decomposition to FeS and S). The main findings of this work suggest that labile sulphur does not fully account for the measured SO2 content of the off-gas, and that limited oxidation of sulphides during melting also contributes to the SO2 content. Details of sulphide oxidation reactions in the furnace remain unclear, and it is currently not possible to provide a theoretical framework for the relationship between the extent of oxidation and variables such as temperature, gas composition, particle size, and residence time in the furnace black top. Through the use of the Monte Carlo model it was, however, possible to constrain the extent of sulphide oxidation to about 1%. This work has shown in practice what was expected in concept, that SO2 in off-gas is proportional to furnace power and ingress rate. The model that was developed consistently slightly under-predicts the quantity of SO2 generated. It also highlights that more work is required to better understand the analytical methods used to analyse for SO2 in off-gas.

Jan 1, 2011

By M. F. van der Merwe

Anglogold Ashanti?s Kopanang Gold Plant (previously No. 9 Gold Plant) treats ore from Kopanang and Tau Lekoa shafts. The plant is twin streamed and has dedicated treatment circuits, from milling to final product, for each shaft. Waste rock material is used to compensate for the mill gap on both streams. Each stream consists of three 4.85 m x9.15 m ROM mills in closed circuit with a single stage hydrocyclone, milling an average of 7 000 t per day. The liner configuration in each mill consists of six rows of 30 grid liners along with rectangular lifter bars. The topic of gold lock-up is not new and has been investigated and reported on many times, both within Anglogold Ashanti and the broader mining industry. Although the lock-up mechanism is understood, its measurement is neither practical nor precise. The initial lock-up in a new liner and the release as the liner wears down cannot be accurately quantified. Previous test work carried out on Kopanang Gold Plant (with a ?gold scanner?) measured the natural gamma radiation emitted by uranium. This radiation is in proportion to the mass of concentrate locked up in the grid liner pockets, as well as between the cast-on backing plate and the shell. The ratio of concentrate lock-up was estimated as 35% behind the liners and65% in the pockets. Mill gravity concentrates are recovered during routine relining operations from behind the grid liners at Kopanang Gold Plant. Prior to relining, the liners tend to release the concentrate from the pockets as the liners wear. Historical Kopanang data from actual ?mill gold? smelted indicates that an average of 29 kg gold is recovered from behind each row. This indicates a total lock-up of 250kg gold per mill. This locked-up gold should preferably be minimizedor eliminated for the following reasons: ?The cyclic build-up and release of gold in mills complicates accounting ?Gold concentrate arising from liners is a security risk and creates a major mechanism for gold theft ?Loss of interest on the value of 250 kg fine gold is significant and was a major driver for the project. These factors led to the need to develop techniques to eliminate or at least minimize the gold lock-up in the mills. Wave liners, with rubber inserts, have been successful in eliminating lock-up, and were tested at Kopanang Gold Plant in November 2000. However, due to increased load-slip and high wear rates associated with these liners, this option proved less economical in terms of liner wear. Grid liners, with rubber-filled pockets, demonstrated a very high wear life and eliminated pocket lock-up. This system was successfully trialed in January 2003, but unfortunately did not prevent lock-up behind the liners. Current developments have resulted in a system that eliminates both pocket and backing plate lock-up. The conventional grid liner design has been modified to remove its steel backing plate. Rubber inserts that are integrated onto a rubber backing plate, have been designed to be used with the newly modified grid. The backing plate and grid pockets are now completely occupied by rubber, thus completely eliminating concentrate build-up around the new grid liner system installed in November 2003. Results to date are promising and liner life is expected to exceed conventional performance.

Jan 1, 2005

The following notes have been compiled to assist authors in the preparation of papers for presentation to the Institute and for publication in the Journal. All papers must meet the standards set by the Council of the Institute, and for this purpose all papers are referred to at least two referees appointed by Council. STANDARDS FOR ACCEPTANCE To merit consideration papers should conform to the high standards which have been established for publication over many years. Papers on research should contain matter that is new, interpretations that are novel or of new significance and conclusions that cast a fresh light on old ideas. Descriptive papers should not be a repetition of well-known practices or ideas but should incorporate developments which would be of real interest to technical men and of benefit to the mining and metallurgical Industry. In some cases a well prepared review paper can be of value, and will be considered for publication. 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The Institute as a body is, however, not responsible for the statements made or opinions expressed in any of its publications. Reproduction from the Journal is permitted provided there is full acknowledgement of the source. These points should be borne in mind by authors who may submit their work to other organisations as well as to the Institute.

By P. L. Duncanson, J. D. Toth

Since 1995, when "freeze lining" refractory systems were introduced to the ferroalloy industry, they have gained in popularity, due to the freeze lining?s reputation for reliability, safety, and the contribution it makes to profitability. As with many popular and effective technologies, however, the freeze lining has spawned low-cost pretenders that claim the "freeze lining" name. On the surface they appear to contain some of the components of the technology, such as thermally conductive materials, but they fail to incorporate all of the principles that define a true Freeze Lining. The term "freeze lining" refers to the refractory system?s ability to maintain a temperature profile that is low enough to freeze a layer of process material on its hot face, which insulates the refractory and prevents direct contact with molten metal and slag. In doing so, the common wear mechanisms found in the submerged arc furnace - chemical attack, erosion, and thermal stress - can be prevented. These wear mechanisms are all related to high temperature; thus, they are prevented by maintaining low temperatures. Certain refractory properties and design concepts are absolutely necessary for the lining system to function as a true Freeze Lining. The paper explains these requirements and why they are important - the Truth of freeze linings - and further explains why systems that ignore one or more of these requirements cannot claim to be freeze linings, thereby exposing the Myths.

Jan 1, 2004

By M. Bryson, V. Deeplaul

As a national facility, Mintek?s brief is to conduct high calibre research that allows the most effective utilization of South African resources. The research takes two different forms, with the efforts being directed at both high-risk endeavours that may lead to the development or adoption of new technologies or the reapplication of technologies to potential new operations. Starting in the 80s Mintek began developing a process to upgrade the UG2 ore and invested heavily in projects, equipment and people to service the industry. Some of the highlights of that work that has been conducted here include: ?Development of a milling and flotation process for UG2 ores ?Development of the ?Mintek Process? for maximizing PGM recovery for UG2 ores ?Conversion of the UG2 milling circuits to open circuit ?Development of a robust pilot plant facility for use in plant design studies ?Use of dense media as a waste rejection option ?Use of attritioners in flotation circuits. More recently, and with the future in mind, the following processes are being researched, some of which have already been commercially applied: ?Development of a flowsheet for Platreef ores ?Use of optical sorting technology for upgrading platinum ores ?Use of a mini-plant for reagent optimization studies. Each of the highlights listed above will be discussed in the paper.

Jan 1, 2004

By J J. Pretorius, G M. Hoffmann

Utilisation of lower-grade (<60 per cent Fe) resources, not utilised in the current products, is crucial to ensure optimal resource utilisation and maintaining/improving future profit margins by reclassifying low-grade material to ore. The purpose of the Sishen Expansion Project (?SEP?) is therefore to investigate the technical and financial viability of producing up to an additional 10 Mtpa of new products at Sishen from material currently classified as low-grade materials. Jigging technology has progressed to a point where Sishen?s 50 to 60 per cent Fe run of mine (?ROM?) material, once considered as waste, can be beneficiated to produce a saleable 64 per cent Fe product. This has been confirmed through appropriate beneficiation testwork. Consequently, Sishen can now produce saleable product from material not currently included in the resource definition, increasing the resource base of the mine significantly and ensuring higher resource utilisation. Mine Planning utilised the geological models to produce detail planning schedules, reflecting the current and SEP plants separately, optimised to comply with product specifications of both the current and SEP plants and to confirm the viability of the low-grade resources identified as SEP feed material. The SEP products specifications have been derived by optimally matching iron ore market requirements with the revised resource base. A 64.0 per cent Fe lump product and a 63.5 per cent Fe fine product are the optimal SEP products. The SEP plant will be able to produce 10Mtpa at an average yield of 60 per cent and a lump to fine ratio of 62 to 38. The plant consists of five major sections namely crushing, material preparation, beneficiation, final product handling and quality control services. Maximum integration with the current Sishen plant was considered. Kumba currently has an agreement with Transnet to rail up to 23.5 Mtpa through the Sishen Saldanha Iron Ore Export Channel (?IOEC?). Transnet and Sishen Iron Ore Company have signed a Definitive Agreement that deals with the expansion of IOEC?s capacity, which increases Kumba?s entitlement from 23.5Mtpa to 35.0Mtpa. The detailed enviro-legal impact assessments for the SEP indicated that the project has low enviro-legal risk as a result of it being a brownfields project incorporated into the current Sishen operations.

Jan 1, 2006

By E. Y. Baafi, H. Fan, W. Zeng

We present a discrete event simulator, TSJSim (Truck-Shovel JaamSim Simulator), for evaluating the stochastic and dynamic operational variables in a truck-shovel system. TSJSim offers four truck allocation strategies: Fixed truck assignment (FTA), Minimizing shovel production requirement (MSPR), Minimizing truck waiting time (MTWT), and Minimizing truck semi-cycle time (MTSCT) including the genetic algorithm (GA) optimization and the frozen dispatching algorithm (FDA) optimization rules. Multiple decision points along the haul routes for all the trucks close to the decision points were included in the model. The simulation results indicate that the trends associated with production tons and queuing time utilizing the four truck allocation strategies (MSPR, MTWT, FDA, and GA) all demonstrated similar patterns as the fleet size varied. As the system fleet size increased, the system production tons under these strategies at first increased significantly and then remained relatively constant; the queuing time relating to these strategies showed a positive relationship with the system fleet size. The bunching time decreased when the truck allocation strategies were applied in the model. In the simulated truck-shovel network system with multiple traffic intersections, by assigning the trucks at the intersections, both productivity and fleet utilization increased.

Dec 13, 2022

The heap leaching of base metal ores can be applied within a number of different scenarios, each requiring its own set of parameters to be determined during the metallurgical testwork programme. The occurrence of acid-gangue reactions and its concomitant precipitation reactions is a factor common to all cases, and requires that the optimal irrigation acid strength be found that optimises the combination of extraction kinetics, acid consumption and possible premature blinding of the heap due to precipitation reactions. For the heap bioleaching of base metal sulphide ores the oxygen requirement needs to be determined for the design of the aeration system, and the operating conditions employed need to also facilitate bacterial growth over and above the acid strength optimisation mentioned above. For the heap bioleaching of chalcopyrite, the need to preserve heat in the heap becomes yet a further parameter of critical importance. For the heap leaching of uranium ore a choice is required between either chemical or bacterial oxidation, based on economic and processing factors. Frequently the operating parameters need to be determined for a circuit in which heap leaching is combined with tank leaching and/or pressure leaching. The processing implications and metallurgical testwork approach for each case is discussed.

Jan 1, 2007

By N. J. Alderman, D. J. Clowes, N. I. Heywood

The effects were studied of the presence of comminuted flint on the rheological characteristics of chalk slurry pumped through a 92-km long pipeline from Kensworth Quarry to Rugby Cement Works in the UK, and their impact on the pipe flow conditions. Flow curves were measured for 63different chalk slurry samples; these were described by the Bingham plastic model. In addition to observing trends in the yield stress parameter and plastic viscosity in the model with variations in both flint concentration and dispersant additive, use was also made of slurry viscosity values at a reference shear rate of 60 s-1for the pipe flow. It was found that chalk slurry viscosity decreases with increasing flint content up to 10% by weight for a given additive concentration, and increases with increasing additive concentration from 0.7 to 1.0%, for a given flint content. The pipeline flow regimes were identified using the critical value of the Bingham Reynolds number for laminar flow breakdown. For Bench 11 (quarry bottom) chalk slurries, it was observed that all sections of the pipeline operate in the turbulent flow regime for the nine different formulations and for the three pipe diameters used along the pipeline. However, this was not always the case for Bench 1(quarry top) slurries. It was therefore recommended that chalk slurries prepared from Bench 1 should not be used because of the strong likelihood that laminar flow conditions will occur owing to the presence of higher clay concentrations within this bench. This, in turn, will lead to an unsafe operation of the pipeline because of the potential for coarse particle settling. Likewise, blending of chalk from Bench 1 with the lower benches such as Bench 11 could be problematic and this requires further experimentation.

Jan 1, 2007

By Xiaoxu Sun, Jianchao Yao, Qiheng Zhu, Dubo Wang, Jiancheng He, Shijie Lu

Tower mill is considered to have a better regrinding and fine grinding effect compared with ball mill, and its application is much broader. The spiral agitator of the tower mill is driven by the motor. Media inside the mill is under the combined actions of the spiral mechanism, the cylinder, and media nearby, and these parameters are key factors affecting the grinding effect. However, it is not possible to obtain detailed information of kinematic law of media based only on traditional laboratory experiments, let alone the relationship between parameters of kinematic law of media and grinding effect. Experimentation is the only way to develop industrial equipment. However, this is time-consuming and costly, which hampers the further research of the tower mill’s grinding mechanism. The paper selects two structural parameters (gap between the edge of the spiral agitator and the cylinder wall, ratio between the diameter of cylinder and that of the spiral shaft.) and three operating parameters (diameter of media, filling ratio, the speed at the edge of the spiral agitator) as variables to do an orthogonal designed experiment of five factors, four levels, and thereby obtaining change law of grinding indicators of different parameters. Experimental equipment may be simplified to enable an applicable simulation strategy. Simulation based on a discrete element method is conducted to obtain the change law of the speed of media, collision frequency, normal force, and radial force. The relational curve between parameters of kinematic law of media and energy consumption of grinding is clarified, and key factors affecting grinding efficiency are determined. Those factors will be used for optimising the design and operating process. The research result of this paper obtained from laboratory experiments and computer simulation provides data support and theoretical bases, and has directive meaning and applicable value for tower mill’s optimisation and large-sized design. Keywords: Tower mill, discrete element method, kinematic law of media, energy consumption of grinding

Jan 1, 2020

By D. P. Roberts

This investigation aimed to simulate the experiments performed by Nic Gay (Gay, N.C.1976. Fracture growth around openings in large blocks of rock subjected to uniaxial and biaxial compression. International journal of Rock Mechanics and Minining Sciences and Geomechical Abstracts, vol. 13. pp. 231-243) on fracture growth around openings in blocks of rock subjected to uniaxial and biaxial compression, using the Elfen discrete element code. The results of the physical experiments indicated a number of trends that were successfully replicated in the numerical simulations, including crushing ahead of the face, the formation of a sub-vertical tensile fracture at centre-span, the formation of groups of fractures originating from the crushed face zone, the formation of large corner-to-corner fractures which precede sample failure, and linking of slot corner and sample corner fractures leading to sample failure. In addition, other features were apparent that were not reported by Gay. It is believed that these took the form of conjugate shear fractures (as reported by Gay in a previous paper) and other features that may have been altered or inhibited by the presence of pre-existing structure in the physical samples. It was found that the samples, though nominally made up of the same rock type, must have had significantly differing properties. The presence of pre-existing structures may have contributed to this discrepancy. Strain measurements from the physical experiments were reasonably well matched, except where the gauge lay directly in the path of advancing fractures.

Jan 1, 2012

By H. Dong

This paper presents a heat conduction model to determine the erosion profile of freeze linings in a ferronickel submerged arc furnace. Kirchhoff transformation was adopted to simplify the nonlinear equation governing heat conduction. The boundary element method (BEM) and Nelder-Mead simplex optimization method were employed to solve an inverse heat conduction problem. Erosion profiles could be obtained when calculated temperatures at sensor locations agreed well with measured temperatures. The model was validated by comparing the heat loss through the linings, which was calculated by BEM and integral operation after erosion profiles were obtained, with the value calculated from industrial data such as actual power consumption, tap-to-tap time, and ferronickel output. The optimal solution for the erosion profile could be acquired when the difference in heat losses calculated by these two methods is at a minimum.

Jan 1, 2014

By L. Ziyuan, S. Chunbao, K. Jue, H. Yang, S. Tichang

In this study, potassium ferrocyanide, a non-toxic cyanide precursor in dark and diffuse reflection environments, was applied as a reagent for the leaching of gold. The free cyanide ions were gradually released from the potassium ferrocyanide solution under the ultraviolet light. Orthogonal leaching experiments were performed in gold ore to analyse the effect of solution pH, potassium ferrocyanide dosage, and temperature in potassium ferrocyanide solution system under UV light. Response surface methodology (RSM) was applied to explore the role of potassium ferrocyanide in gold leaching, Optimised results showed that the gold recovery reached 67.74% in a high-alkaline environment at a 12.6 pH, 3.8 kg/t potassium ferrocyanide dosage, 62°C, and irradiance of 10mW/cm-2. The gold leaching kinetics was monitored by quartz crystal microbalance with dissipation (QCM-D) of potassium ferrocyanide solution. The results indicate that the gold extraction process consists of two processes: adsorption and leaching, and a rigid adsorption layer formed on the reaction surface. Furthermore, Xray photoelectron spectroscopy (XPS) analysis of the gold sensor surface after leaching reaction showed that -C≡N appears on the gold sensor surface, and the gold is oxidised to form AuCN complexes. Keywords: Gold leaching, potassium ferrocyanide, UV light, QCM-D, AuCN complexes

Jan 1, 2020

By D. F. Malan, L. Scheepers

Seismic risk in the deep gold mines of South Africa has been studied for many decades. A clear understanding of the effect of geotechnical conditions on the seismic hazard nevertheless remains elusive. Certain reef types seem to be associated with a higher risk of rockbursts. The stability and deformation behaviour of excavations on the different reef horizons are affected by the rock types and the varying strength properties. The seismic response to mining is therefore also expected to differ according to the geotechnical conditions. As a case study of this behaviour, the seismicity at Mponeng mine was investigated. On the VCR (Ventersdorp Contact Reef) horizon, two areas can be delineated. On the eastern side of the mine, the footwall is shale, and on the western side it is a strong brittle quartzite. More large-magnitude events occur in the area with the shale footwall than the area with the quartzite footwall. Moment tensor analyses indicated that the majority of the large-magnitude events are not related to geological structures, but are face-related, implying that shear failure of intact rock is occurring ahead of the mining front. Preliminary modelling indicated that the closure volume for the shale footwall may be higher than that for the quartzite footwall, providing a possible explanation for the observed difference in seismic response.

Mar 2, 2022

By P. Sharma

Longwall panels facing wind blasts have been investigated at both Newstan and Moonee Collieries in the Newcastle Coalfield under the Wind Blast Project of the School of Mining Engineering, The University of New South Wales. The fluid mechanics involved in the compression and expulsion of air during wind blasts have been defined and the overpressure and air velocity time histories utilized to determine the wind blast parameters and define the relationship between them. The characteristics of wind blasts pressure pulses in mine roadways show some similarity with transient phenomenon like air blasts from explosives and shock waves from the failure of pressurized vessels. The peak wind velocities in roadways, however, exhibit marked deviations from theoretical predictions based on compressible fluid flow and Rankine-Hugoniot relationships applied to goaf air displacement and panel geometry. Peak overpressures and wind velocities have shown a positive correlation with the areas of goaf falls, with the values peaking off for larger areas. The field investigations have helped the mine management in risk assessment and in evaluating the success of induced caving by hydrofracturing to mitigate the hazard.

Jan 1, 2004

By R. G. Votteler, A. C. Brent

"The business performance of mining corporations in South Africa is adversely affected by the constantly increasing electricity costs. The most commonly used power sources are the national utility supplier via a grid connection, and on-site diesel generators. Previous research has identified the renewable sources of solar photovoltaic (PV), onshore wind, and geothermal energy in hybrid versions with current sources as possible opportunities to counteract rising electricity costs. To provide a clear understanding of the new, developing market of renewable energy sources, this research is divided into two papers. This first paper investigates the internal business structure of mining corporations in order to evaluate electricity generating sources. The multi-criteria decision analysis (MCDA) method is selected as the most suitable approach for this. The paper identifies the criteria used by mining corporations to evaluate possible electricity generation sources for self-generation by means of the corporations’ own investment. Four mining corporations with several mining locations were interviewed. The interviews revealed both new and identical evaluation criteria when the findings were compared to earlier MCDA adaptations analysed in the literature review. The second paper (Part 2) combines current knowledge about the external macroeconomic environment with the findings about the internal environment described here. MCDA is adapted in Part 2 and implemented to analyse and compare current to hybrid renewable sources from the perspective of mines. IntroductionMining corporations in South Africa are currently adversely affected by increasing electricity prices. Electricity is supplied mainly by Eskom1 and, especially in remote locations, by on-site diesel generators (Boyse et al., 2014). Electricity price increases, emanating from diesel price hikes and Eskom, have escalated the total operational expenditure on electricity by the largest mining corporations from 8% to 20% of total operating costs in the past seven years (EIUG, 2015). The reliability of electricity supplied by Eskom has decreased drastically (Govender, 2008), and the prices will increase annually by at least 13% until 2018 (Numbi et al., 2014; Eskom, 2015b). In addition, the South African government plans to introduce a carbon tax on greenhouse gas emissions (Alton et al., 2014)."

Jan 1, 2017

By H. Ogasawara

Information on rock stress is important for safe mining in seismically active ground. On a major gold mine, a few tens of crews are continuously conducting geological drilling with small pneumatic machines. However, stress measurements are not often carried out in South African deep-level gold mines. One of the reasons is the drilling diameter that overcoring requires, which is much larger than the diameters used in regular geological drilling, e.g. Boart Longyear Metre Eater, which drills AQ or BQ holes. Larger diameter holes result in slower drilling advance, more load in transportation and handling at sites, and higher cost. In order to enable overcoring in BX size (60 mm diameter), we modified the compact conical-ended borehole overcoring (CCBO) technique that has been suggested by International Society for Rock Mechanics (ISRM) and was originally designed for NX drilling (76 mm diameter). With a single overcoring, the 3-D stress tensor can be determined. We tested this modified method at a depth of about 3 km at Moab Khotsong mine in South Africa. We worked with drilling crew who usually work at geological drilling with the Metre Eater. In January 2011, we tried using regular geological drilling tools (a sequence of a normal BX bit, reamer, and rod) without success. In August and September 2011, introducing stabilizers and thin BX bits, we succeeded. We could complete a cycle of procedures necessary for an overcoring, including shaping the borehole-end conically, glueing a 16-element strain cell, and overcoring, within 2.5 hours. Only 10 cm overcoring is needed, which increases the chance of successful overcoring in heavily fractured conditions. This modified method is suitable for up-dip holes to depths of 10-15 m from tunnels, and has the potential to be widely used at the initial stage of geological exploration drilling at many localities.

Jan 1, 2012

By A. Tor, M. Borowski, N. Szlazak, D. Obracaj

This article presents possibilities of reducing methane emission to the atmosphere in working mines in Jastrzebie Coal Company by means of proecological solution. They form a new approach towards the problem of rational and effective use of natural resources both in economical and environmental respect. Power and thermal energy for underground air conditioning in mining excavations are produced from the methane, which is drained out of the mine for safety reasons.

Jan 1, 2003

By R. P. Jensen

This is a sampling of the papers presented at the conference, the proceedings can be bought from the SAIMM Arbitrary Lagrangian Eulerian (ALE) computational techniques allow treatment of gases, liquids and solids in the same simulation. ALE methods include the ability to treat shock waves in gases, liquids and solids and the interaction of shock waves with each other and with media from one of the other categories. ALE codes can also treat explosive detonation and the expansion of the explosive gases and their interaction with air and solids. ALEGRA is a 3-D ALE code that has been developed at Sandia National Laboratories over the past few years. ALEGRA has been applied to a 2-D simulation of presplitting using decoupled explosives in rock blasting with very interesting results. The detonation of the explosive at the bottom of the hole sends a shock wave up the borehole driven by the explosive gas expanding into air. The explosive gas compresses the air against the stemming column where it rebounds and recompresses at the bottom of the borehole. This type of ringing takes several cycles to damp out. The explosively induced expansion of the borehole is also treated by ALEGRA as well as the shock wave imparted to the rock. The presentation of this paper will include several computer animations to aid in understanding this complex phenomenon.

Jan 1, 2000