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By D J. Bradshaw, E M. Wightman, C L. Evans, B Triffett

During the commissioning phase of Prominent Hill, periods of reduced recovery were experienced with higher-grade ore blends. This was unexpected and as part of the process to identify the cause, surveys were conducted in May 2009, with two different ore blends (copper grades: 1.94 per cent Cu (blend 1) and 2.49 per cent Cu (blend 2)). Metallurgical performance was assessed in terms of rougher recovery and grade with consideration of both pulp and froth effects. In addition, hydrodynamic measurements (gas hold up, bubble size, superficial gas velocity) as well as measurements of bubble load and top-of-froth grade were taken during the surveys and full mineralogical assessment of selected streams completed to characterise the nature of the differences. The metallurgical results showed that the lower performance was obtained with blend 2 which contained the higher amount of chalcocite and was higher-grade. Analysis of the survey data showed that for both ore blends more than half of the copper loss occurred in the +38 ¦m size fractions. Almost 30 per cent of the copper in the +38 ¦m fractions that reported to the rougher tails during processing of blend 2 was liberated compared to less than five per cent for blend 1. Additionally almost 60 per cent of the copper in the +38 ¦m fraction of blend 2 was chalcocite compared with approximately 20 per cent in blend 1. This paper discusses the sensitivity of the chalcocite-to-surface chemistry effects causing marked reductions in recovery either through reduced pulp recovery or froth phase (detachment) effects. The reagent suite and operating conditions were subsequently changed and the recoveries increased substantially and the sensitivity to ore changes eliminated. It should be noted that subsequent optimisation work, which focused on recovery improvement, has led to copper recoveries of over 90 per cent being achieved.CITATION:Bradshaw, D J, Wightman, E M, Evans, C L and Triffett, B, 2012. Characterising the reasons for the difference in performance of two ore blends in early processing at OZ Minerals Prominent Hill Operation, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 273-278 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

A nine-month investigation was conducted into the effect on coke quality and blast furnace operation of the addition of bentonite and southern coal to the northern coal fed to the coke ovens at the Newcastle steelworks.Additions of 0·3 per cent bentonite or 25 per cent southern coal to the northern coal increased the coke strength from 15-20 A.S.T.M. stability to 25-30 A.S.T.M. stability. It is likely that improved mixing and blending facilities would, in both cases, give a coke of over 30 A.S.T.M. stability.For the same coke strength, the use of 0 3 per cent imported Wyoming bentonite was considerably cheaper than the use of 25 per cent southern coal, but the use of Australian bentonite promises the same coke strength for still lower costs. Other additives such as coke breeze, charcoal, iron ore fines, and certain other finely divided materials, gave relatively minor improvements in coke quality.There appeared to be sufficient improvement in blast furnace operation and production to justify full scale addition of bentonite to improve coke quality, although other variables, particularly iron ore physical quality, overshadowed on many occasions the effect of coke quality. Further coke trials with southern or bentonite will be carried out when ore quality has been improved by the introduction of ore sintering at Newcastle.INTRODUCTIONDuring the period of operation of the Newcastle coke ovens and blast furnaces from April 1960 (when No. 3 blast furnace was blown in after rebuilding) to December 1960, a bentonite coke trial was carried out based on earlier research findings (Gregory, 1959a, 1959b; Felton and Gregory, 1960; Gregory, 1960) that as little as 0 3 per cent to 05 per cent bentonite clay added to northern N.S.W. high volatile coking coals gave a significant increase in coke strength. The bentonite coke trial was followed by trials...

Jan 1, 1962

It has been clearly demonstrated in both the first, as well as in the last world conflict, that a nation's ability to wage as well as win a war is primarily a function of its industrial, and particularly its steel making capacity, provided both are directed to munition production.The Axis gambled on their pre-war policy of bullets before butter giving them sufficient initial advantage to decide the issue before the Allies had time to gear their industries to war production.Fortunately for us, Hitler and his advisers apparently underestimated Russia's war potential, although they must have known that Russia was, in 1939, the third largest steel making country in the world, as shown by the following figures:

Jan 1, 1947

By R Cannings, J Wallace, M McCamley

The mining industry continues to have major disasters (Bingham Canyon, Pike River, Upper Big Branch, Mount Polley and Samarco), which often have a devastating effect on the enterprise, in terms of personnel deaths and injuries, environmental destruction, and financial and reputational loss. These disasters are not imposed from outside the business or organisation, they are almost always a function of loss of control of the management of the organisation’s critical assets and processes that they contain or to which they are exposed.Asset integrity is discussed as an effective response to business risks in order to mitigate, control and recover from loss scenarios that could expose a mining operation to significant property damage and business interruption, or even total loss. Vital to this process is the identification and control of risks to critical assets. Components of a critical asset assurance program are presented for discussion.Formal risk assessment has a longer history in industries other than mining, eg petrochemical, nuclear, military, aviation and space industries. Risk assessment is a structured, proactive approach to understanding and improving risks, as opposed to a reactive ‘fix-it-when-it-breaks’ mentality. Risk assessment techniques were triggered by major public disasters, such as the Flixborough chemical plant disaster (1973), Three Mile Island nuclear plant event (1979) and others.Today, most industries see risk assessment as an inherent part of their business, but do mining sites capture business risks that are related to major loss scenarios, which could have a significant impact on the operation?Does your risk assessment process:- involve a team having the right skill set so that the discussion is both stimulated and technically sound?- use generic assessment when a site-specific assessment is needed?- fail to consider all possible outcomes, including maximum foreseeable loss (MFL)?- fail to identify all hazards and controls associated with a particular activity?- fail to monitor controls effectively?This paper addresses the issues identified by these questions and provides some direction for developing a risk management process where business risk associated with critical asset integrity is integrated with other business and safety and health risk processes to provide a robust method for managing your business. Case studies and common findings from critical asset failures are used to support the need to include critical asset assessments as part of business risk management processes.CITATION:Wallace, J, McCamley, M and Cannings, R, 2016. How robust are your asset integrity management processes? In Proceedings International Mine Management Conference, pp 53-64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By E de Necker, F D. I Hodg, L-M Cruywagen

The acid mine drainage (AMD) situation at three opencast collieries in the Witbank Coalfield, South Africa, was evaluated from different perspectives. Twenty-seven test pits were dug into the spoils of these collieries to characterise the in situ conditions of spoils of varying age. Detailed static testing was done on surrounding drill holes and additional samples were taken from the test pits. Selected samples were tested using different techniques, namely ABA, mineralogy and kinetic tests. Groundwater monitoring boreholes from the areas surrounding these spoils were also used for characterisation. The ABA results compared favourably with the in situ determinations; acidic test pits proved to be potentially acid-generating from ABA, even when the samples had neutral paste pH. Kinetic test results showed these samples to yield low pH leachate over the test period. In several of these results, the theoretical depletion of neutralising potential and the onset of acidity were well matched. NAG pH-values and final observed water chemistry corresponded for the cells predicted by ABA to acidify, but compared poorly in cells that did not acidify. Results from the non-acidic spoils were consistent with the in situ observations. Alternative kinetic test methodologies were also employed. Duplicate samples were tested in humidity cells and in aerated trays that were manually wetted on a regular basis. Results from these tests showed an excellent correlation. Detailed mineralogical determinations using XRD and XRF were used for comparison to the ABA and, in some cases, humidity cell results. These comparisons show that the ABA results are consistent with the results expected from the mineralogy. The conclusion from these assessments is that ABA, in most cases, provides information that can be correlated to the field, mineralogy and to humidity cells. The use of multiple techniques leads to a higher degree of confidence in the use of the data.

Jan 1, 2003

By Hochwimmer B, Baxter JL

Heavy minerals are mined from two fossil strandlines on the southern Swan Coastal Plain. The Capel shoreline, 7 km inland, and the Yoganup shoreline, 15 km inland are arcuate, northwest-facing, and remote from the modern coast. Based on foraminiferal and molluscan assemblages, the shorelines are probably of Pliocene age. The Yoganup shoreline is adjacent to the Whicher Scarp, which is cut into the Leederville Formation (Lower Cretaceous) at the southern boundary of the Swan Coastal Plain. Stratigraphic relations and detailed sedimentology have been studied from temporary exposures in the Yoganup Extended and Yoganup North mines, within a strandline complex at 27 m and 18-33 m above sea level respectively. Heavy minerals were deposited in thin, shallowing-upward sequences along a wave-dominated clastic shoreline cut into pre-Cainozoic sediments. Lithofacies units deposited in eolian, foreshore, shoreface and lagoonal environments are the most significant sites of heavy mineral accumulation. The data collected provide a basis for further exploration.

Jan 1, 1986

By King RP, Kientzler P

In recent years, ultrasonic comminution technology has been developed at the Utah Comminution Center. An ultrasonic grinding device was assembled and investigated. An ultrasonic transducer system has been significantly improved by using a special type of piezoelectric ceramic and preloading to 4.1 x le kPa to obtain maximum strength. The improved system provides constant and rapid vibratory promotion of fatigue fracture resulting in more effective breakage. The design principles for an ultrasonic mill are developed in this paper. Size reduction was successfully achieved in the ultrasonic nip-roll device for a variety of materials. Ultrasonic comminution has repeatedly demonstrated the capability of producing fine particles from a variety of materials. A comparison between ultrasonic grinding and dry ball milling of limestone showed that the ultrasonic device produced much narrower size distributions than the ball mill. This trend is especially obvious in the coarse size range where few particles remain, and in the fine size range where overgrinding is prevented. This behavior might have some interesting applications in areas other than mineral processing like powder metallurgy or material science where narrow and controlled product sizes are required for the successful elaboration of high-technology ceramics and glasses. Ultrasonic comminution has a significant advantage in the accurate control of the product size.

Jan 1, 1993

The BHP Billiton Cannington Mine uses paste as the principal method of backfill. The paste consists of mine tailings and cement. The pastefill process at Cannington includes a surface plant where the thickened total tailings stream is filtered using two vacuum disc filters operating in parallel. The filter cake is mixed with Portland cement in a spiral mixer to produce a paste at a specified yield stress and cement content. The initial system design only required paste to be delivered under gravity. In July 2001, Cannington Mine expanded to 1.8 million tonnes per annum. In order to achieve this, production commenced on five new levels underground, 350 metres horizontally from the paste plant. Due to the high viscosity of paste, this distance was too far to transport by gravity. Traditionally, paste has been transported only short distances (50 m) using positive displacement pumps, with very limited success. At Cannington, a conveyor was installed which was designed to achieve zero spillage into the environment. This paper discusses the innovative design strategies used to attain zero harm on the environment whilst conveying a material, which is difficult to transport.

Jan 1, 2002

By Hermann J. A

Over the last few years enormous dapooits of high-grade bauxite have been discovered in Australia, ;_ d an alum .nium smelting industry based on them is rapidly being developed,, This industry requires large amounts of carbon, as about 60 pounds of carbon anodes are consumed for every 100 pounds of aiumin.'.'-n produced. Tie anodes are usually made by mixing finely ground petroleum coke with coal tar or petroleum pitch, forming the mix into shapes under pressure, and baking them at around ?.200¦C0 Petroleum coke is ussd uecause its high density gives good strength and conductav_ty to the finished electrode, and its purity ensures that contamination. of the alumin- ium by extraneous i,iorganic material from tho carbon is low,

Jan 1, 1969

This paper outlines the manner in which legislative control for tunnelling and allied operations has evolved, detailing Victorian experience. It examines the concept of mine managers as it relates to the industry and attemps to illustrate its benefits. The Victorian experience in relation to fatal and serious accidents is examined in detail, particularly in the allied art of trenching and examines the Krings system of trench lining support which is hoped will catalyse an increase of engineering expertise in this area. The paper concludes by demonstrating that safety awareness is not incompatible with production efficiency or economic viability.

Jan 1, 1981

The Tom, East and West zone, stratiform Zn-Pb-Ag deposits at Macmillan Pass, Yukon, Canada were discovered by Hudson Bay Mining and Smelting Co Ltd prospectors in 1951. Further exploration, including two phases of underground exploration produced an HBM&S calculated reserve of 9.28 Mt of 7.5 per cent Pb, 6.2 per cent Zn and 69.4 g/T Ag for these zones. Cominco Ltd optioned the property in 1988. Deep, surface drilling extended the West and Southeast zones downward 200 - 300 m, indicating an additional potential resource of several million tonnes of good grade. The magnitude of the controlling syndepositional setting suggests that mineralisation continues to greater depth but with increased drilling and possibly mining costs. The 30 x 60 km Macmillan Fold belt trends WNW across the NW Selwyn Basin and Cordilleran trend. Within the fold belt, the Central Block - a complex, rift controlled basin of Devonian siliciclastics, hosts seven zones of Pb-Zn-Ag mineralisation clustered about four hydrothermal centres. The centres, distributed over 24 km, are coincident with small syndepositionally active structural sub-basins. The Tom deposits, in one such sub-basin, are localised by a third order structure consisting of two palaeobathymetric troughs flanking a syndepositional horst. This structure caused drastic facies and thickness changes over 600 metres of strata and focussed the venting of hydrothermal fluids through permeable conglomerates in the horst and its flanking growth faults. Mineral facies are zoned, with Pb-Ag contents rapidly diminishing outward from the vent resulting in restricted areas of high grade Pb-Zn-Ag-Ba ore within more extensive, sub-economic, Ba-Zn mineralisation. Widespread iron carbonate alteration of the footwall and high Si, B and Zn values in the hangingwall 'fingerprint' the deposit and along with the distinct facies variations provide aids to exploring the Tom and like deposits.

Jan 1, 1993

By H W. Wu

Occupational exposure limits for diesel particular matter (DPM) are progressively being adopted in a number of countries. Many of these follow the lead of the US Mine Safety and Health Administration initiated in 2008. In line with adoption of best practice it is accepted that all exposures should be reduced to as low as reasonably achievable. The management of diesel emissions and occupational exposures to those emissions requires an integrated strategy incorporating efforts from all key departments on a mine, including management, production, maintenance, supply and occupational health and safety.Australian coalmine longwall moves rely on the use of high-powered diesel equipment such as chariots and other machines that produce exhaust pollutants of gases and DPM. To reduce mine personnel’s exposure levels to DPM a hierarchy of controls can be followed. Minimising the use of diesel equipment, better operator positioning in relation to exposure source, using efficient engineering methods and adopting better ventilation to reduce concentrations through dilution are some of the controls that can eliminate exposures. Approaches generally adopted in Australian longwall mines currently rely on a combination of strategies such as optimisation of ventilation, use of diesel particulate filters and use of diesel tag boards that minimise the number of vehicles through recording entry and exit into working panels.A study has been undertaken into the mine ventilation systems currently in use during longwall moves within Australian modern longwall extraction mines. This paper reviews current longwall section ventilation systems and discusses evolving changes being adopted to address the more complex problems in dealing with section DPM during phases of the operational moves. The effects of DPM on crew members as well as the diesel equipment operators within a longwall section are examined. Issues that should be considered in designing the longwall section ventilation during the moves are discussed.CITATION:Wu, H W and Gillies, A D S, 2015. Review of ventilation optimisation strategies during longwall moves, in Proceedings The Australian Mine Ventilation Conference, pp 133–140 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By M Wortley, J McKay, D La Rosa, O Guyo

It has been a generally held concept that crushing operations were, by their nature, too simple to benefit from the implementation of advanced process control. The commissioning of an OCS¬ expert control system and image-based oversize detection system, VisioRock, at the Pilbara Iron Tom Price facility are dispelling these notions. A constraint-based OCS¬ expert control system has been designed and commissioned on the high-grade crushing and screening plant along with a vision-based oversize detection system functioning on six product conveyor belts. To date, the expert control has demonstrated the ability to increase production by maximising dynamic constraint utilisation. Dynamic constraint utilisation is a concept developed by Rio Tinto Technical Services for effectively evaluating constraint-based control logic performance. The VisioRock system has been installed and configured and has been operating for a period of several months. Currently, Tom Price and Metso personnel are working to define correct oversize detection thresholds. Details of the plant implementation are discussed.

Jan 1, 2006

By S Oliver, D Willingham

"Although a resource model is central to the mineral resource value estimation process (Glacken and Snowden, 2001), creating it is a labour intensive task and in the end it is a limited representation of the actual orebody. Creating this resource model is a labour intensive task that requires inputs from geology, mining, metallurgical and commercial disciplines. It requires thousands of samples from hundreds of drill holes to be verified, grouped in geological domain, interpolated and then valued. Even after all this effort, a model is only an estimation; therefore further significant effort has gone into quantifying uncertainty in the model and subsequently risk around any value estimates derived from the model. Further risks to model quality are introduced through poorly conditioned data or incorrect assumptions.This paper proposes the application of machine learning to automate the resource model development. Machine learning is applied to the traditionally manual tasks of geological formation, domain identification and validation of the block model mineralogy. Through automation the resource estimation process can be accelerated, allowing more drill holes or a larger resource body to be processed in a given time frame, or allowing the process to be more agile to changes in input data and assumptions. A case study based on drill hole data from a Western Australian iron ore deposit (Government of Western Australia, Department of Mines and Petroleum, 2015) is used to demonstrate the application of machine learning in this process.CITATION:Oliver, S and Willingham, D, 2016. Maximise Orebody Value through the Automation of Resource Model Development Using Machine Learning, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 295–302 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By E Widzyk-Capehart, C Hölck Teuber, S Steffen, V Rivero, O Fredes, E Sanchez, I Pedemonte, N Gonzalez

This paper summarises the research, development and initial application of a sensing platform that has the potential to monitor subsurface deformations, pore pressure and other variables simultaneously to gain a better understanding of rock mass behaviour. The platform is based on Networked Smart Markers (NSMs) devices, which, with their ability for wireless communication between individual sensors and the possibility of real-time data acquisition and processing, will assist in the development of predictive tools to better assess rock mass behaviour.A good opportunity to implement this technology is in the specific application of transitioning from an open pit mine to an underground caving operation. One of the key elements to maintaining the mining business during such a transition is having a good understanding of the unique geotechnical conditions of mutual influence created during the open pit to underground interaction. The knowledge acquisition will require the implementation of a robust platform for geotechnical monitoring, which could be enhanced by incorporating the NSMs. The integration of sensors within the NSMs would enable the collection of additional data about rock mass behaviour (ie caving propagation and crown pillar fracturing), which could be used to improve the management of mining operations and, specifically, allow the development of reliable predictive tools based on the data collected.CITATION:Widzyk-Capehart, E, Hölck Teuber, C, Fredes, O, Rivero, V, Sanchez, E, Pedemonte, I, Gonzalez, N and Steffen, S, 2016. Understanding rock mass behaviour through the development of an integrated sensing platform, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 275–284 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By J Allen, B Oats, S Palaniandy, M Lollback

The Julius Kruttschnitt Mineral Research Centre has conducted an intensive VertiMill® (VTM) survey program at the Cannington mine concentrator as part of the ‘collaborative research in stirred milling technology’ program funded by Metso Minerals. Since 2003, Cannington has progressively added grinding capacity into the circuit through VTMs operating in secondary and regrinding duties. Cannington was one of the first mines to adopt this technology in secondary duty by installing two VTM-1500-WBs as part of a capacity expansion to produce sub-100 µm rougher feed. Subsequently, an additional VTM-800-WB was installed in the lead regrind circuit to prepare sub-20 µm cleaner stage feed.Several surveys were carried out to evaluate the VTM performance over a range of changed conditions. Among the key changes in operating variables were circuit power draw, feed rate and water addition to the bottom of the mill. The average specific energy for secondary duty was 3.7?kWh/t. The lead and zinc regrind mills consume 8.1 and 15.3 kWh/t respectively. Generally, the VTM installations have successfully prepared feed for rougher and cleaner circuits by reducing the top size into the floatable regime with steeper particle size distribution, which has led to enhanced recovery. The survey results show the success of VTM installations in secondary (receiving feed from autogenous circuit) and regrind duties.CITATION:Palaniandy, S, Powell, M S, Hilden, M, Allen, J, Kermanshahi, K, Oats, B and Lollback, M, 2014. VertiMill® performance updates in secondary and regrind duties at Cannington mine, BHP Billiton, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 263–272 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By K Faure

At Sams Creek a peralkaline granite porphyry dyke hosts gold-bearing sulfide-quartz-siderite veins. The granite dyke intrudes Ordovician-Silurian metapelite and quartzite, and has thin lamprophyre dykes along its contacts. The mineralised veins and the granite and lamprophyre dykes have been deformed during several phases of folding, the youngest of which is Early Cretaceous. The granite has been hydrothermally altered, with early magnetite-siderite¦biotite alteration overprinted by sulfide and quartz-siderite veins and quartz-perthite-albitesiderite-pyrite-rutile¦sericite alteration assemblages. The sulfide veins are composed of arsenopyrite + pyrite ¦ gold ¦ galena ¦ sphalerite ¦ chalcopyrite ¦ pyrrhotite ¦ graphite, with minor quartz and siderite. The gold contains significant silver (up to 30.8 wt per cent) and ranges in fineness from 692 to 844. Immiscible liquid-rich fluid inclusions, in quartz protected from recrystallisation by enclosing arsenopyrite, contain carbonic liquid that homogenised at temperatures of 320 - 355¦C. The Sams Creek gold deposit is distinguished from the orogenic gold deposit type by its stockwork veining, magnetite-siderite¦biotite alteration, high sulfide content, ore mineralogy and the absence of mineralisation in the metapelite country rocks. Features of the Sams Creek gold deposit do not fit neatly into existing classifications of granite-related gold-bearing deposits. The peralkaline composition of the Sams Creek granite and the absence of molybdenite and paucity of chalcopyrite, are major points of difference with gold-rich porphyry copper deposits. The presence of a lowsulf idation-state ore mineral assemblage, carbonate alteration and carbonic fluid inclusions at Sams Creek are typical of many of the reduced granitic intrusion-related type of gold deposit. However, notable differences are: the reduced type granites are metaluminous and calc-alkaline; and Sams Creek only has high As in contrast to elevated Bi, W, As, Mo, Te, and Sb in the reduced type. The Sams Creek deposit also shows affinities with gold deposits associated with alkaline magmatism, and it appears to be a new variant of this type as an As-Au deposit associated with a peralkaline granite and lamprophyre.

Jan 1, 2004

By J Westh, S Rashleigh, L Gallagher

Mining companies are moving towards automated haul trucks and other equipment. One reason for this is that if automated trucks can operate in a standard pattern over and over again without variation, then human error is reduced, if not eliminated.The challenge for mining production leaders/managers is to ensure operators follow standard operating procedures for load and dump operations, with each operator doing the same thing, every time. However, operators are only human and inconsistent performance is rife at every mine site. The finger may be pointed at the operators for not doing as instructed. The clarity and variability of trainer instructions may be considered causal to the problem. Herein lies the problem. Almost all operators believe they are following the procedure very closely; moreover, they all demonstrate a strong desire to conform to instruction.Using video analysis and feedback, each operator can be shown where and by how much they differ from the benchmark set by their company. Operators, often for the first time, can see definitively what they are doing, compared to industry best practice.The technology utilised by real-time video (RTV) crews measures time, distance and angles. It can overlay the video of the operator at the load site, with video of the perfect pass. Operators are amazed when they see how near to, or how far they are from best practice.The footage and data gathered by RTV assists operators in understanding exactly what adjustments are required to increase proficiency. It also assists load and dump superintendents to identify where in the process they are losing time. When translated to overburden removal or mineral/resource extraction, the result is large production economies without the need for large capital investment in new automated technology.CITATION:Westh, J, Gallagher, L and Rashleigh, S, 2012. Improving safety and mine productivity using real-time video technology, in Proceedings International Mine Management 2012, pp 173-188 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

By A Sainoki, D Fukuda, K Shioya, C Zhang, M Sharifzadeh, T Yamaguchi, S Saydam, J Kodama, C A. Amagu, Y Fuji

In an open pit mining, ensuring stability of rock slope has been one of the major challenges. As the instability of rock slopes can results in slope failures; consequently, endanger the lives of workers, affect mining operations, and often lead to economic losses. Therefore, it is practical important to study the stability of rock slopes to ensure safe, smooth, and effective mining. The stability of rock slope of about 130 m height at Higashi-shikagoe limestone quarry, which has experienced slope failures four times since 1996, was assessed. The rock mass at the quarry is consists of mainly limestone, schalstein and slate rocks intersected by clay seams of about 70 m thick at footwall of the rock slope. Previously, the effects of limestone excavation at the foot of the rock slope and shear failure due to rainfall infiltration have been investigated. Although clay is widely known to plays a vital role in the stability of slopes in engineering projects including mines, but its impacts on slope deformation at the study quarry are not adequately examined. Therefore, the present study addressed the impact of presence of clay on slope deformation at Higashi-shikagoe limestone quarry by employing both field displacement measurements and numerical simulation. Firstly, surface displacements measured by automated polar system (APS) for over eight years were analysed to understand the overall characteristics of the slope deformation. The measured results show that the displacement gradually decreases with time. The maximum displacement of about 100 mm was observed at middle of the rock slope. Secondly, the effect of deterioration and plastic behaviour of the thick clay layer were simulated using two-dimensional finite element method (2D FEM). The simulated results reveal that the clay exhibited deterioration by water contact and plastic behaviour arising from mining activities at the footwall of the clay zone. Based on the characteristics of the measured and simulated results, it was found that the displacement induced by the effect of deterioration of clay is more noticeable at the north side of the quarry whereas displacement induced by excavation is quite significant at the south side of the quarry if clay behaves as an elasto-plastic material.

Nov 29, 2022

By Isobe K, Muchi I, Hsieh YS

Theoretical and experimental studies have been made-to clarify the physical and chemical behavior of the tuyere combustion zone of blast furnace. Gas streamlines around this zone were visualized by the use of the two-dimensional equip- ment. Close agreement between the observed stream- lines and the calculated ones is found. The three- dimensional experimental studies have revealed that there exists a so-called dry zone in the neighbor- hood of the raceway and the trickling liquid be- haves approximately like a continuum. A kinetic model is develdped to describe the behavior of coke combustion in the tuyere zone. The model is based on the reaction kinetics, the differential balances of heat and mass, and the mechanics of gas flows. Regarding-the-axial distribution of gas composition in the tuyere zone, good agreement is obtained be- tween the model prediction and the data observed in a working furnace by the other investigators. Cal- culated results-show that the maximum consumption of coke occurs at the intermediate region of the raceway. For the blowing of oxygen-enriched or high -humidity blast, the position at which the maximum consumption of coke occurs is shifted toward the tuyere nose. Similar effect is found when the par- ticle diameter of coke in the tuyere zone is de- creased. The solid flow pattern around the tuyere combustion zone was visualized by the use of the two-dimensional equipment in which the sublimation of dry ice particles in front of the tuyere was

Jan 1, 1981