Search Documents

By D. Z. Mraz, R. S. Jones

Unlike in coal mines where caving methods are used, the subsidence over potash mines in Saskatchewan, Canada, is a function of gradual mining convergence. Because of the presence of high pressure water aquifers over the evaporite salt formations, the mines have to be designed as regionally stable and no caving is allowed. The extracted area converges gradually and the convergence is mainly a function of the extraction and the mining method employed. Consequently, the subsidence rate is very slow and the bridging of the over-lying strata is a considerably more important phenomenon than elsewhere. The paper evaluates a case history of convergence and subsidence in a deep potash mine in Saskatchewan.

Jan 1, 1986

By Carl Erickson

The term shortwall mining is somewhat of a mis¬nomer. It may infer a longwall mining system, but of much shorter face length. Actually, continuous pillar mining is a more descriptive term. Coal is mined using a continuous miner as would be done in pillar extrac¬tion, but with the addition of roof supports to control the caving. Face length on such a system typically is 46 to 61 m (150 to 200 ft). The coal is cut in front of the roof supports in the same direction as with a long¬wall shearing machine or plow, but it is mined with a continuous miner and shuttle cars of the same type as used in continuous mining. ROOF SUPPORTS Roof supports for shortwall mining must be con¬siderably larger than those used for longwall mining because of the additional roof to be supported by the wider 2.6- to 3.4-m (81/2- to 11-ft) cut of the continuous miner. Capacities of shortwall chocks in current use vary from about 454 to 726 t (500 to 800 st). The higher capacity as compared to longwall roof supports is needed primarily because of (1) the greater support length, hence more roof weight, and (2) the presence of draw slate in the eastern coal seams, where shortwall is being used. The most popular shortwall support currently used is the four-leg 590 t (650 st) model. This support is shown in Fig. 1. The price of this support is approxi¬mately $25,000 each. As shown in Fig. 1, the shortwall chock incorporates an unusually long forward bar that has an additional hydraulically operated extension bar to provide face support for the wide miner cut. METHOD OF OPERATION Mining Sequence In shortwall mining, two or three (depending upon the chock design) move up cycles of the chock are needed because of the miner cut width. Fig. 2 depicts the five steps required to complete the move of chock and spill plate using a miner that takes a 3.3-m (10-ft,

Jan 1, 1982

By C. Tsamantaki

Water-bentonite suspensions exhibit a yield stress which is defined as the minimum applied stress for flow. Considerable debate exists about the yield stress being a material property, hence different measuring methods should give similar answers, but several investigators have demonstrated that it is an engineering reality. Yield stress is normally estimated indirectly from the rheogram obtained with a viscometer following an extrapolation to zero shear rate (the dynamic yield stress), but the technique may be prone to errors because of slip flow. Direct measurements, not prone to such errors, rely on an independent assessment of the yield stress, normally carried out with the vane method (the static yield stress). In this paper results are presented and compared regarding the yield stress of 14 different water-bentonite suspensions measured using both the direct and the indirect methods. In order to obtain a wide range of yield stress values, two different types and two concentrations of bentonite at various pH were tested. Rheological data were obtained using a rotational speed viscometer and a yield stress vane measuring device. Measured vane yield stress values ranged from 5 Pa to 83 Pa. Rheological data collected with the rotating viscometer were fitted using various conventional techniques (interpolation, linear and non-linear regression analysis) as well as using a golden section yield stress search methodology based on Herschel-Bulkley model, developed in house. The vane instrument measures directly the yield stress of the suspensions and requires no further data handling. A comparison of the measured values of the yield stress with the direct and the indirect method is then made for the water-bentonite samples. Not very large differences are observed among different techniques and the variations are discussed. Similar data from literature are also analyzed and the comparison shows that differences on the various estimation methods are much larger than the differences observed in this study.

Jan 1, 2006

By Anthony Edey, Leigh A. Readdy, Bruce A. Kennedy

Introduction Very little attention normally is given by the experts, or the public at large, to the fact that the majority of the oil that has been or will be discovered within the U.S. remains in the ground. The inherent limitations of oil production through surface wells, either by primary or secondary techniques, will result in a total of over 300 billion bbl of oil left in the ground after completing production by standard petroleum techniques in currently producing or producible fields. This reserve represents some two-thirds of the original quantity of oil discovered in place. Recent work by a number of groups has shown that there is strong economic justification for extracting this remaining oil by mining and processing techniques. Table 1, taken from 1977 API reports, demonstrates the oil left in place at the end of the conventional petroleum production cycle in then-known fields within th’e U.S. Possible targets for oil mining operations include (1) oil remaining in place in fields and pools that have reached economic depletion by current petroleum production methods and that are not amenable to economic recovery by conventional petroleum industry techniques; (2) oilor bitumen-saturated rocks not normally considered by the industry to constitute producible reservoirs, such as shales and diatomites; and (3) asphalt- and bitumen-impregnated rocks. Economically Depleted Fields A more detailed examination of the depleted fields shows that estimates of oil remaining in place after primary, secondary, and nondestructive tertiary recovery can vary widely. There is significant evidence, however, that more than half the estimated original oil in place (OOIP) remains in the reservoir after all petroleum extraction techniques have been applied. If one compares the sum of past oil production and estimated remaining producible reserves with the API estimate of total discovered OOIP as of 1975, it becomes apparent that for the U.S. as a whole, 67070of the 00IP will remain in place at the end of the

Jan 1, 1980

By Anthony Edey, Leigh A. Readdy, Bruce A. Kennedy

Introduction Very little attention normally is given by the experts, or the public at large, to the fact that the majority of the oil that has been or will be discovered within the U.S. remains in the ground. The inherent limitations of oil production through surface wells, either by primary or secondary techniques, will result in a total of over 300 billion bbl of oil left in the ground after completing production by standard petroleum techniques in currently producing or producible fields. This reserve represents some two-thirds of the original quantity of oil discovered in place. Recent work by a number of groups has shown that there is strong economic justification for extracting this remaining oil by mining and processing techniques. Table 1, taken from 1977 API reports, demonstrates the oil left in place at the end of the con¬ventional petroleum production cycle in then-known fields within the U.S. Possible targets for oil mining operations include (1) oil remaining in place in fields and pools that have reached economic depletion by current petroleum production methods and that are not amenable to economic recovery by conventional petroleum industry techniques; (2) oil-or bitumen-saturated rocks not normally considered by the industry to constitute producible reservoirs, such as shales and diatomites; and (3) asphalt- and bitumen-impregnated rocks. Economically Depleted Fields A more detailed examination of the depleted fields shows that estimates of oil remaining in place after primary, secondary, and nondestructive tertiary recovery can vary widely. There is significant evidence, however, that more than half the estimated original oil in place (OOIP) remains in the reservoir after all petroleum extraction techniques have been applied. If one compares the sum of past oil production and estimated remaining producible reserves with the API estimate of total discovered OOIP as of 1975, it becomes apparent that for the U.S. as a whole, 67% of the OOIP will remain in place at the end of the

Jan 9, 1980

By William J. Maloney

OVERVIEW Blind drilled shafts are becoming increasingly popular, particularly in the Appalachian coalfields, as a secondary and sometimes primary means of ventilation. The reasons for the rebirth of the blind shaft are mainly due to it's economics, timeliness, safety characteristics and inherent independence from underground operations. Historically blind drilling has been used to a limited degree in hard rock and tunneling ventilation. With the recent advances in cutters, bit design, equipment and lining systems, particularly in the Appalachian coalfields, blind drilled shafts are once again the shaft construction technique of choice to the educated ventilation specialist. [ ] HISTORY OF BLIND DRILLING Blind drilling has it's roots in numerous places, including the Nevada Test site, the coalfields of Appalachia and Germany along with the uranium mines of Arizona. Early technology was developed using a variety of equipment mainly of oilfield origin with oilfield drillers entering the industry on a project basis only to "pull in their horns" and return to the oil patch. Shafts completed by oilfield equipment range from the shallow 5' and 6' lined shafts on the Nevada test site to two (2) 10' lined, 730' deep shafts in Alberta for heavy oil development. Several of these shafts were completed to extraordinary depths with the record being a 90" diameter, 6,150' deep shaft being completed in the Aleutian Islands of Alaska in 1969. EQUIPMENT Oilfield equipment is still being used on the Nevada test site but elsewhere specialized blind hole equipment has been developed to enhance the efficiency of particular applications. Where steel liners are required the A-leg derrick with a simple hoist and rotary system is used. The largest user of this type equipment in the world is the former USSR where blind drilling for mine ventilation is the norm. On applications where trip time and cutter changeout are a priority, top drive hydraulic rigs have been developed which are highly automated, efficient and mobile. These rigs are particularly well suited for tunneling applications where shafts are shallow and sites are usually tight.

Jan 1, 1993

My first regular job nearly fell through. My parents were spending the summer in California and I joined them at Lake Tahoe where we were guests at the lovely summer home of the Reids of Belmont. The time went quickly but I was eager to start work so I left for Bisbee a few days earlier than I had arranged. This was lucky, as just after I left a letter came from Gene Whitely, chief engineer of Calumet and Arizona, saying that because of the depressed copper industry there would be no job. I reached Bisbee on a Saturday morning, a day or two before my 23rd birthday, July 27, 1907. The brown plastei four-story Copper Queen Hotel was only a few steps from the station where the branch railway ended. I rented the cheapest room on the top floor and, of course, there was no elevator. I soon learned how to walk up the mile of switching tracks to the Calumet and Arizona office at the Irish Mag mine. I was horrified when Whitely told me about his letter telling me not to come, but since I had not received it he relented and said I could work for a short time anyhow. I was to start at 7:30 the next Monday morning, "holding the ignorant end of the tape”-in other words being surveyor's assistant, at $100 a month. Hours were from 7:30 to 5: 00, seven days a week. I spent Sunday walking around the town. I rented a room at the Royal Lodging House, which was cheaper than the hotel. It smelled strongly of carbolic acid but that meant no bugs. Compared with Cobalt or Cripple Creek, Bisbee didn't seem unattractive. The main street, with one or two-storied stores and saloons, followed the bottom of the canyon with high steep hills on both sides. My lodging house was on a rock in a narrow spot in the canyon, discouragingly called Tombstone Canyon. Chihuahua Hill, opposite the

Jan 1, 1976

By Daniel Su

This paper describes recent ground control challenges encountered at the longwall recovery areas of one of Bailey Mine?s two longwall faces and the proactive measures taken by CONSOL management and engineering to mitigate them. The challenges derived primarily from the following causes: (1) irregular roof coal and draw slate thickness, (2) presence of thick sandstone at the recovery area and extremely weak rocks below the sandstone, (3) close proximity to a regional anticline, (4) low shield set pressure and tip load, and (5) ineffective primary roof support that led to progressive failure of the headgate roof. The presence of the anticline contributed to extensive fracturing of the sandstone. Excessive pot-out in advance of the shields frequently occurred near mid-face due to the presence of thick draw slate and irregular roof coal near the recovery area. This, in turn, resulted in face heights that exceeded the maximum reach of the shields. Subsequently, during longwall meshing, when the advance rate slowed considerably, fractured sandstone would often break loose, causing the shields to yield, thereby reducing the height and inhibiting shearer movement. To improve the headgate and face conditions within the longwall recovery area, several actions were taken, including: (1) assessing site-specific roof geology by conducting in-mine roof coring around the recovery areas and by mapping immediate draw slate and roof coal thicknesses within surrounding entries, (2) increasing pump pressure and thus shield set pressures (3) diligently monitoring shield set pressures and longwall extraction horizon, (4) installing additional cable bolts and roof screening to prevent progressive failure of the immediate headgate roof, (5) fully-grouting supplemental cable bolts to improve headgate support stiffness, and (6) gluing the headgate roof within the recovery areas with polyurethane. As a result of these collective efforts, longwall recovery delays at Bailey Mine were reduced from 21 days in 2006 to nearly zero in 2009.

Jan 1, 2009

Terminology. The term potash originated in "pot ashes" produced by burning wood to ashes in iron pots and then leaching out the soluble salts, chiefly potassium carbonate, from the residue. In modern usage potash is a generic term for various potassium salts used in agriculture and industry. More specifically, it denotes the oxide of potassium, K2O, and the content of potassium in ores and products is stated as weight percent of K2O present. Its salts are commonly referred to as muriate of potash, sulfate of potash, etc. The presence of an adequate supply of available potassium in the soil promotes the health and improves the quality of the plant. insures greater efficiency in photosynthesis, increases resistance to certain diseases, offsets the effect of an oversupply of nitrogen, and helps the plant to utilize soil moisture more advantageously. ("Soils and Men," U.S. Dept. of Agriculture Yearbook 1938.) Occurrence. Potassium ranks seventh among the elements in abundance. It is estimated to constitute some 2.6% of the lithosphere and is found in soluble forms in the oceans, lakes, rivers, and subsurface waters. It is also an important constituent of plant and animal life. Commercially significant accumulations of potassium salts occur in underground deposits formed in past geologic times by evaporation of ancient bodies of saltwater, inland drainage basins, and shallow sea lagoons. The potash content of such waters was the end result of weathering and leaching of insoluble potash-bearing aluminosilicates, such as feldspars, micas, leucitcs, and others. The concentrations of potassium salts in the natural brines of some lakes in the arid and semiarid regions of the continents are also important as sources of potash; the brines of the Dead Sea in Asia Minor, the Great Salt Lake in Utah, and Searles Lake in California typify such concentrations. Every continent has major potash deposits as listed in Table 1 adopted from Cawley.1

Jan 1, 1985

By Sotiris Psomas, Colin M. Eddie

"Steel Fibre Reinforced Concrete (SFRC) Segmental Tunnel Linings have successfully been used for over 20 years in the UK and have been adopted in a number of high profile projects such as High Speed 1, Crossrail, Thames Tideway, as well as High Speed 2. Tunnel linings and especially SFRC design are not covered in the Eurocodes. This shortage of SFRC tunnel design rules seems to be partially addressed by several international publications. However, in the UK, the ‘design-assisted by testing’ (DAT) approach has also been adopted. The Paper discusses the UK’s best design practice and focuses on the DAT methodology as applied in the case of the 6.9km (4.3miles), 7.8m (25.6 feet) ID Lining for the £635million Lee Tunnel Project. The design approach, the full scale testing at the Building Research Establishment (BRE), and the construction innovations are presented. This experience will be transferred to the £4billion Thames Tideway Tunnel.INTRODUCTIONSteel Fibre Reinforced Concrete (SFRC) has been used for Tunnel segments for more than 20 years. The first application of SFRC in the UK was for the Heathrow Baggage tunnel (1994). Since then significant size tunnels have been designed and constructed, such as the Jubilee Line (1999) High Speed 1 (CTRL, 2006), Crossrail (2014), Lee Tunnel (2014) and the scheduled 25km Thames Tideway (‘Super Sewer’) and High Speed 2 rail tunnels. However one the main obstacles in achieving streamlined design and improving efficiency are the lack of appropriate design guidelines for SFRC tunnel segments. This issue will – to some extent – be addressed by a number of current documents on tunnel FRC design either being produced by BSi (PAS8810, expected 2016), ACI (544.R) and ITAtech (Design Guideline PCFRC, 2015) in an effort to advance the design of SFRC and take into consideration the recent developments in Steel and Macro-Synthetic FRC technology."

Jan 1, 2016

By R. Yang

This paper presents a kinematic approach for blast modeling with examples of blast models that were developed previously. A kinematic approach was applied successfully in developing blasting models that can simulate all blast design parameters for field applications. Several applied blasting models have been developed and applied widely in the world. A kinematic approach to blast modeling refers to using measurements of kinematic quantities such as the velocity, strain, or displacement and well-established assumptions to model blasting phenomena, rather than being restricted to use first principal of physics, such as, the stress- and material-constitutive relations. The kinematic quantities are easy to measure in the field. Due to the complexity and inhomogeneity of rock mass properties, using first principles of physics, many parameters of rock and explosive properties must be involved, which are hard or impossible to quantify. This creates a major impediment when trying to simulate the total process of blasting based upon first principles of physics. The 3D kinematic model for muckpile formation was developed and applied to open pit blasts. The multiple blasthole fragmentation model developed during recent years has been applied successfully to many mine sites around the globe. These models are typical examples of blast modeling using the kinematic approach, which enables the models to catch major trends of the blasting process and explicitly simulate full blast design parameters and complex geometries. Blast modeling using the kinematic approach results in easy model calibration and validation against field measurements and effective applications to practical problems. Using kinematic models of the muckpile formation and the multiple blasthole fragmentation model, this paper demonstrates the merits of the kinematic approach for blast modeling. New developments of the models were also presented in the paper, which illustrate the potential of the kinematic modelling approach.

Mar 2, 2022

By R. Rodgers

The Pinto Valley concentrator of BHP Copper Inc. restarted its sulfide mining operations in September 2007 to produce copper and molybdenum concentrates. During the plant production ramp up, the copper/molybdenum circuit quickly reached the copper grade and recovery targets, but the production and quality of the molybdenum concentrate continued to be a challenge. Even though several improvements in the molybdenum circuit were completed, the final molybdenum concentrate did not meet contractual specifications. After reviewing several options to improve grade and reduce contaminants, the installation of three flotation columns were chosen. The column design and construction were done using in-house craftsmen and engineers. Ten days after commissioning, the columns successfully reached a steady operation and began producing molybdenum concentrate to the required specifications, that is, high molybdenum tenors and low copper and iron content. The Pinto Valley operations, are comprised of the Pinto Valley concentrator, the Pinto Valley dump leaching and a solvent extraction/electrowinning (SX/EW) plant. The concentrator operated from 1972 to 1998 when mining and milling operations were curtailed for economic reasons. The SX/EW plant continued operations for copper cathode production. After a cessation of mining operations of almost 10 years, Pinto Valley operations began a restart project in January 2007, to bring the mine and the concentrator back into production. Copper concentrate production started in October 2007 after refurbishing and upgrading the facilities with a new DCS system and filter plant. The daily targets of the concentrator were to treat 56.7 kt (62,500 st) of ore, produce 762 t (840 st) of copper concentrate containing 27.5 percent copper at recoveries of 86 percent and produce 2.2 t (2.5 st) of molybdenum concentrate containing more than 80 percent MoS2.

Jan 1, 2010

By Godfred Amponsah, Mehrdad Razavi

Slope failures very commonly occur during a long period of heavy rainfall and groundwater rise. The failures pose a substantial risk to people, infrastructure, and equipment downslope. In the recent past, the mining industry has faced an increase in tailings dam failure due to several reasons including pore pressure increases in the dams. Many failures have been observed to occur during times of water level fluctuations but the critical factors that influence the initiation of slope failures still need to be adequately clarified. To investigate these factors, laboratory experiments were conducted on model sandy slopes to determine pore pressure-induced slope failure initiation. This study also presents a method to examine water seepage through soil slopes using an ultraviolet (UV) dye and a UV flashlight. The small-scale model test simulation demonstrated failures induced by either water percolation from the upslope tank at a constant level or by raising the water level at intervals. A bottom chamber fully filled with water to replicate groundwater rise was also simulated. The soil slope was monitored at every stage to study the deformations and behavior until failure occurred. Results gathered from the controlled laboratory conditions were useful for the verification of the numerical modeling method created in the computer program Slide. The analysis showed that slope failure always occurred when the toe was fully saturated. High pore pressures and seepage forces reduce the shear force at the toe to almost zero causing it to slide. A comparison of slope height to water level also indicated an average of 96% water level to cause a failure. At this point, the soil slope is fully saturated and has no matric suction. The findings in this study show that, by monitoring the moisture content of slopes, failures can be predicted.

Feb 1, 2024

By Hakan Uyguçgil, Beril Bayraktar, Adnan Konuk

Mining is one of the industries with the highest risk of occupational accidents in Turkey and globally. The most important feature that distinguishes the mining industry from other sectors is the constantly changing working conditions. The risk of accidents is very high, especially in underground mining, and can happen for several reasons. Therefore, it is essential to carry out all necessary measures in coordination with other disciplines to adapt to changing workplace conditions. The dangers that might occur underground must be determined in advance, controlled at their source, or eliminated since it is critical to take the necessary precautions before the accident. Accident prevention will protect miners’ living conditions by contributing to the country’s economy through reduced labour and production losses. In this research, the data from 13,653 accidents reported in the Karadon Hard Coal Enterprise between 2000 and 2011 were analysed and compared using the Life Table and the Kaplan-Meier methods. Accident records were classified and analysed into four categories: environmentalrelated accidents, equipment-related accidents, person-related accidents, and other accidents. Findings in terms of survival time indicate that environment-related and person-related accidents had the highest risk in Karadon, with equipment-related accidents having the lowest. This study established the reliability of using survival analysis methods to investigate occupational accidents in the mining sector. Given that environment-related and person-related accidents occur in a relatively short period, such as 1 year after starting work, it has been recommended that research be done to improve workplace and occupational safety measures and broaden the training given to miners. Additionally, it has been determined that increasing the use of automation and mechanisation in underground coal mines, combined with developing a thorough equipment safety training programme to raise awareness of the danger, can help prevent person-related occupational accidents caused by the interaction between equipment.

Aug 5, 2023

By H. R. Bullis

Lupin is located on the shores of Contwoyto Lake at lat. 65° 48'N, Long. 111° 15'W and lies about 80 kilometers south of the Arctic Circle. Since start up in 1982 the mine has produced over 2.15 million ounces of gold from 6.66 million tonnes of ore grading 10.63 gm/tonne. Total remaining reserves at 1993 year end were 5.1 million tonnes at a grade of 9.11 gm/tonne (1.65 million ounces). This is sufficient for 7 -8 years at the present annual production rate of about 200,000 ounces. The Centre and West Zones of the deposit are open to depth. The deposit is in an Archean metaturbidite sequence of the Contwoyto Formation, which has been mapped as part of the Yellowknife Supergroup of supracrustal metasedimentary and metavolcanic rocks making up part of the Slave Geologic Province. These rocks have been subjected to regionar and contact metamorphism and to several phases of deformation. Six stages of Archean plutonism have been identified and all Archean rocks have been cut by Proterozoic diabase dyke swarms. Gold mineralization in the Lupin deposit is commonly fine grained and associated with pyrrhotite and arsenopyrite in amphibolitic banded iron formation. The gold-bearing portions of the host iron formations are characterized by the presence of multiple quartz veins and the pervasive replacement of grunerite by hornblende. In sparsely mineralized portions of the host iron formation, zoning of sulfides about quartz veins is clearly seen with the arsenopyrite halo being more restricted around the veins than the pyrrhotite halo. In well mineralized portions, quartz vein densities approach one vein per metre along strike. In these areas pyrrhotite distribution in the iron formation is more pervasive and the rock takes on the appearance of a banded sulphide rock.

Jan 1, 1995

By Hemendra N. Kalia

Several attempts have been made in the past sixty or so years to commerciliaze the vast oil shale deposits of the United States of America. However, the industry has yet to become viable and economic. To date, it has not been possible to produce oil from the oil shales at a competitive price when compared to the oil produced from oilfields by conventional methods. However, the development work has been quite fruitful in furthering the art of thick bed mining and technology of in situ retorting. The in situ method has the potential of recovering oil from thick beds and the resource recovery potential is much greater than that from underground mining and surface retorting. In situ methods require that the shales/ marlstones be fragmented ' in place to induce adequate porosity and permeability to allow in situ' heating of the fragmented shales. This can be accomplished by using explosives. However, it has been found that the existing blasting systems, though very efficient, are somewhat lacking. The explosive become insensitive when shot in multiple vertical decks. They can also become insensitive when spaced horizontally at close proximity to other charges. Also, since the blasting is done in a very limited free face, this limits the delay time that can be allowed between charges. Consequently it is not always possible to predict the performance of the blasting system on a routine basis. Furthermore, since it is not possible to undertake secodary blasting, it is imperative that the blast design function properly. Recent, successful retorting by Occidental Petroleum Company of retorts seven and eight suggests that some of these problems may have been overcome. This paper addresses some aspects of in situ retorting and problems those have impeded the development of a viable oil shale industry in the U.S.A.

Jan 1, 1983

By Ulrich Maidl, Marc Comulada, Janosch Stascheit

"INTRODUCTION Cohesive soils are notorious for causing clogging of the cutter head and the excavation chamber of tunnel boring machines (TBMs). While clogging leads to a drastic reduction in excavation performance, it further induces higher wear of tools and other parts of the cutter head and may even prevent a controlled support of the tunnel face and, thus, lead to face collapse and excess settlements or sinkholes. Employing well-balanced soil conditioning techniques, the clogging tendency can be significantly reduced. The monitoring and control of soil conditioning as well as the timely detection of potential clogging tendencies require a close monitoring of all relevant machine parameters and measurements. To this end, a reliable and powerful Process Controlling software that gathers all machine and process-related information is a prerequisite for successful mitigation of clogging-induced problems. The remainder of this contribution is organized as follows: First, a brief introduction to the Process Controlling system PROCON is given. Afterwards, the mechanisms and mitigation techniques of clogging are discussed. Finally, an example is given how Process Controlling has been employed to soil conditioning in a tunneling project with highly clogging soils.PROCESS CONTROLLING Being both the active part and a huge measuring device, the shield machine represents the core component in mechanized tunneling. This machine comprises a manifold of complex components and devices that require constant supervision and control and, thus, is equipped with a manifold of different sensors that provide a continuous monitoring of the state and condition of the machine (Maidl & Stascheit, 2014). If these data are put into the whole context of the tunneling process, they can provide insight to the assessment and optimization of the performance and to the prediction of potential risks and hazards such as, for example, the tendency of clogging of the cutter head."

Jan 1, 2016

By P. J. Mackey

A whole new group of non-ferrous pyrometallurgical processes with the ability to utilize tonnage oxygen and capture sulphur dioxide were developed and commercialized over the period 1940s–1980s. Many of these earlier process developments were undertaken with limited knowledge of the process chemistry and influence of key process variables; in many cases, piloting helped provide much new physico-chemical data, but gaps remained. The second generation versions of these technologies of today provide all the primary copper, nickel and lead produced worldwide by pyro-metallurgical smelting. Further, process development has continued and a new generation of copper and lead smelting technologies have also been developed in China since the 1990s. The older reverberatory and blast furnaces have been progressively replaced by the newer technologies—a good example being the introduction in 1992 of the copper IsaSmelt technology at the Mt. Isa smelter in Australia where the former fluid bed roaster and reverberatory furnaces were replaced by a single new smelting unit, together with an acid plant for sulphur dioxide collection. The development of these new technologies was made possible by investment in fundamental and applied research. The lesson for the future is, in order to sustain these improvements, continued investment in research and development capability is required—to do otherwise is to risk obsolescence and lack of competiveness in the world market. Dr. Peter Hayes at The University of Queensland is one of the many researchers and process engineers who have contributed to the fundamental understanding of metallurgical processes over this period of rapid change in technologies. The present paper briefly outlines some of the many contributions Peter Hayes has made to the understanding of kinetics, mechanisms and phase equilibria in metallurgical systems, and metallurgical process development.

By S. Pastor, S. Hahn

"As the concept of autonomous haulage systems (AHS) moves from prototypes to production-ready applications, the operating performance of the haul road will become critical to the overall success of autonomy in mining. Deterioration in road performance will require remediation, human intervention and significant, albeit temporary, changes to operating procedures, to accommodate road maintenance. With autonomous trucks comes the opportunity to reduce road formation and operating width. This will, therefore, generate potentially significant reductions in stripping ratios and improvements to mine economics, but only if the design of the road, and its associated deterioration rate, is predictable and manageable, based on the materials used to construct the road and the maintenance interventions to be carried out on the road.This article presents the assessment of a digital photogrammetric approach to the characterization of a mine haul road surfacing, or wearing course material. Design and maintenance parameters for these roads are currently determined partly from physical particle size distribution (PSD) assessments of ‘in-road’ material. However, this approach does not accommodate the need, nor leverage the benefits from, AHS. The digital imaging approach is assessed in this article, using two standard digital analysis software tools, together with in-service mine haul road wearing course samples and images that are analyzed to determine the applicability and reliability of the approach to deliver a real-time assessment of haul road surfacing conditions and thus to identify the road maintenance interventions required to address deterioration.Enhancements in mine road design, construction and management for the past 20 or more years has largely been focused on short-term tactical needs. These improvements have not been matched by advances in the fundamental technologies that underpin mine road design and management and, although the quality of mine roads have probably"

Jan 1, 2015

By A. L. Hinde

Ideally, mill circuits should be controlled so that excessive random disturbances are reduced in frequency and amplitude. It is difficult to derive an objective measure of the effectiveness of any chosen control strategy. Often, the response of the circuit to pulse or sinusoidal disturbances is used as a measure of the effectiveness of control, but this is not adequate in many circumstances because such disturbances bear little resemblance to those that occur in practice, and such an approach cannot be easily related to the profitability of the reduction process. A superior approach appears to be the application of the theory of stochastic processes. This theory permits both real process disturbances to be modelled accurately, and useful objective functions for control to be derived. A test of the usefulness of stochastic theory in mill control was made on the gold ore milling circuit shown in Figure 1. This circuit was fed with an ore which had a liberation characteristic such as that shown in Figure 2. It is simple to show that, for such a liberation characteristic, the recovery of valuable mineral will vary as the standard deviation of the particle mass-size distribution varies even though the mean particle mass-size is kept constant. Similarly it may be shown that excessive perturbations in the circulating load in a milling circuit such as that shown in Figure 1 can affect liberation. Figure 3 shows how, as the cyclone feed density increases and the sump water addition decreases at constant sump level, the cyclone operation becomes unstable and the discharge "ropes? with a consequent catastrophic coarsening in product size. By minimising the variance of the circulating load it is possible to reduce the probability of initiating instabilities of this nature.

Jan 1, 1977