Search Documents

By Keith A. Heasley

In the past, numerous displacement-discontinuity (DD) models of stratified rock masses have been proposed using a homogeneous isotropic elastic overburden. In this paper, it is postulated that a laminated overburden model might be more accurate for describing the displacements and stress in these stratified deposits. In order to investigate the utility of using a laminated overburden in a DD model, the fundamental mathematical basis of the laminated model is presented and graphically compared with the fundamental behavior of homogeneous isotropic elastic overburden and with field data. Specifically, the stresses and displacements surrounding an idealized longwall panel as determined from the laminated overburden model are presented and compared with results from the homogeneous isotropic overburden and with measured abutment stress data. Also, the remote displacements and surface subsidence as calculated by the laminated overburden model are compared with homogeneous isotropic calculations and with measured subsidence data. The results of this investigation show that the laminated overburden is more supple, apt to propagate displacements and stress further, and better able to fit observed data than the classic homogeneous isotropic overburden. Ultimately, it is suggested that the laminated model has the potential to increase the accuracy of displacement and stress calculations for a variety of mining situations.

Jan 1, 1996

By Rudolf Hubmer

In October 2013 JSW Steel decided to place an order to Primetals Technologies Austria (former Siemens VAI Metals Technologies) for the installation of a comprehensive Level 2 process optimization system for more than 20 existing production facilities of various suppliers. For SMS-I new L2 systems are provided for two hot metal pretreatment stations, three hot metal desulphurization stations, three ladle furnaces, two 1-strand slab casters, a ladle tracking system as well as a shop supervisory system. Additionally the existing L2 system for one 1-strand slab caster is being upgraded in the course of the project. In SMS-II new L2 systems for the 7 hot metal desulphurization stations, 4 ladle furnaces, 1 new RH vacuum degasser, ladle tracking system and a shop supervisory system are supplied. Despite of the challenging time schedule the commissioning of the single facilities started within less than 12 month after contract effectiveness. The installed Level 2 process optimization systems together with the achieved results are described in this paper.

Aug 16, 2017

By Rowan A' Murry Karstel

One way to ensure dragline productivity is by Increasing the size of the dragline bucket. In August 1994, Optimum Colliery in conjunction with Van Reenen Steel, Northwest Applied Technology, SSAB of Sweden and Barlows Equipment launched the new lightweight dragline buckets. Optimum built the first prototype bucket that was used for the deslgn for future buckets. After knowledge had been gained from measuring the input force of the bucket Northwest Technologies designed the new bucket with finite element analysis. Together with the knowledge of quenched and tempered steel from SSAB of Sweden and Barlow Equipment, the new Wrightech bucket was born.

Jan 1, 1998

By H. R. Coles

Test work conducted in the 6.4 and 10.52 m Aerofall Mills at the Iron Ore Company of Canada Carol Project showed that the conventionally used ?deflector?-type liners which form the basic principle of Aerofall Mill grinding did not necessarily provide the best grinding performance. A new design, using low profile liners incorporating radial ribs of a proper height, actually improved the mill throughput in the order of 9 to 20% without sacrificing grinding efficiency. In addition, the new design reduced liner weight and scrap losses, which resulted in a reduction of liner consumption by 25%. It provided better protection to the mill shell and reduced the overall maintenance cost for the mill

Jan 1, 1980

By R. W. Culbertson, S. Kasper

During the 1920's, approximately 11,000 small gasifiers were in operation in the United States. They converted about 15 million tons (13.6 Mt) of coal per year into low Btu gas. In some cases, hot raw gas was used for applications such as firing open hearth furnaces or brick kilns. In other cases the gases produced in the gasifiers were cooled, cleaned and desulfurized for various utility and industrial purposes. The steel industry was by far the largest user. The most important fact was that the conversion of coal to a usable fuel gas was demonstrated to be commercial. During the late 1940's and early 1950's, this form of energy was largely replaced by natural gas as the pipeline net work was expanded. Producer gas was no longer economically competitive. Over the past 25 years, government controls on the interstate price of natural gas have maintained this situation. At present only three commercial small coal gasifier plants are still in operation in the United States. These facilities are operated

Jan 1, 1980

By E. M. Spokes

Starting in 1980, a committee of the National Research Council studied the question of why some underground coal mines are safer than others and what could be done to improve the ones with poorer performance. The results indicated that safety is improved by management commitment to safety, by cooperation between labor and management on safety matters, and by quality training of employees and managers. Younger miners have higher accident frequencies, but are less likely to be killed or permanently disabled by a lost-time accident. Methods for improving safety performance are proposed.

Jan 1, 1987

Capture airborne coal dust generated by a continuous mining machine to reduce workers? dust exposure and to improve face visibility. Approach Develop a low-profile dust collector system which can be mounted on the boom of a continuous miner. How It Works When coal is mined with a milling head continuous miner, a substantial amount of coal dust (respirable and non-respirable) escapes the dust suppression sprays at the cutter head. This can cause poor visibility around the cutting head and can expose the workers to high levels of respirable dust. A practical means of removing this dust is with a scrubber mounted directly on the mining machine. Under a Bureau of Mines contract, a low-profile, machine-mounted dust collector (MMDC) was developed to avoid adding extra height to the continuous

Jan 1, 1983

Coal slurry pumping was introduced into the U.K. in 1973. Gateside packs were prepared in areas of containment using R.O.M. coal and a special fast setting cement. The packs restricted roadway convergence and moderated spontaneous combustion risks, but costs were high and alternptives were sought. A similar system using OPC and an accelerator had limited success. Much more successful was the Aquapack process which used dilute slurries of a special OPC based cement and an accelerator based on sodium carbonate and bentonite pumped simultaneously into la fabric packbag. The Tekpak system using HAC and a much modified calcium sulphate mixture superceded Aquapack on the grounds of improved cement pumping life lower alkalinity and lower costs. A further modification of this system gave a cement with a 24 hour pumping life thus obviating flushing out pipe ranges except at the week-ends, improved packbags also increased the efficiency of the process. The hazard of spontaneous combustion can be inhibited if air supply channels across the waste can be located and plugged. Using gas samples from pack pipes to locate the heating and injecting a special grout, formulated from bentonite, sodium silicate and thixotroping agents. into the waste on the intake road has proved a successful method of controlling heatings. Mine' roadway and face cavities are being safely and successfully filled with cementitious foams produced in a novel placer machine. The foams are based on fast setting cements with specialised foaming agents. Up to 13 cu. metres per hour of fast setting thixotropic foams can be produced and their use is now widespread throughout U.K. coal mines.

Jan 1, 1986

By Gene Mattila, Ron Boyd

Introduction Rock bolting is a general term that encompasses pinning, roof bolting, rib bolting, and cable bolting. Rock bolting contributes the highest nonproductive cost and is the most significant safety risk in mining today. Total installed bolt costs are now more than $20 per bolt. Rebolting or repair work doubles this. And bolting accidents account for about 30% of all fatal and nonfatal lost time accidents. It is only logical, then, for the mine operator to install the highest quality anchors possible. Every bolt on the market - tensioned, untensioned, full contact, or point anchor - has designed capabilities in axial, shear, and fluctuating ground conditions. Bolts will provide a designed support if material specifications and installation procedures fall within the manufacturer's recommendations. This also assumes that there are no unexpected geological or operational changes. Proper material specifications and installation procedures should guarantee the mine operator a quality anchor. To help assure this, the Mine Safety and Health Administration (MSHA), the US Bureau of Mines (USBM), and the AMC Manufacturers group developed stringent ASTM materials standards. These govern mechanical point anchor bolts and bolts using threaded and nonthreaded rebar. There are also minimum standards that suppliers must comply with in the manufacture of frictional bolts. However, most frictional bolt standards are based on the manufacturer's own specifications. It would be impossible to set uniform regulations on frictional bolts. Each bolt provides support in a slightly different manner and thereby requires different material needs. Quality Control In any case, material quality can generally be assured through tight order specifications and periodic quality control checks. The problem with installing quality anchors does not solely lie with the material. It includes all the events that occur from the time a bolt leaves a manufacturer to the time it is installed. The anchoring ability of any major type bolt can be affected by transportation, storage, mechanical performance of installation equipment, installation demands of the operator, proper drilling accessories, and local geology. Table 1 and Fig. 1 document the negative events that can affect each bolt and the degree to which it can be affected. Drilling a hole of oversized diameter, for example, is an operator controlled factor. It will adversely affect most bolts. An over-sized diameter reduces, or even eliminates, the anchorage capability of a mechanical shell. It will reduce the support capacity of a split set to nearly nothing. And it will cause a partial or incomplete grouting around the resin bolt. Frequently, due to bit wear, holes are drilled undersized in diameter and may not be properly cleaned out. In this case, it will be difficult for the operator to push the mechanical shell into the hole, thereby causing him to drill another hole. In cases where the bolt is obviously not providing anchorage, operators will probably drill another hole and place another bolt. Rock Bolt Regulations It is the situations where a bolt is improperly installed in the hole, but gives the appearance of a good bolt, that are frightening. In fact, some safety officials and engineers believe that only 50% to 60% of installed bolts are working. These bolts cause irregular ground load transfers in other bolts and overload them. This causes hazardous situations and overstressing. It is these bolts that fail prematurely 200 to 255 mm (8 to 10 in.) behind the face and possibly contribute to the high accident rate. The government and several manufacturers recognized the need to check the integrity of rock bolts. These programs are in different stages today. Tight torque regulations have been established for mechanical

Jan 4, 1985

By J. Miettunen

"The lining of a grinding mill has an important role in creating the conditions for the grinding process. The main purpose of the lining is to transfer the energy taken by the mill motor to the contents of a mill. The power draw curve of the mill, if measured with sufficiently short intervals, describes how well the lining works in lifting and mixing the material to be ground.The power draw curve can also be used for determining the volumetric filling of a mill. This new measuring technique was developed at the Pyhasalmi concentrator in 1989-90. The measuring device with its PC-connections offers an excellent tool for controlling volumetric mill filling, for maximizing throughput and for research purpose (e.g. process studies, mill linings design).The paper describes the new method and the results achieved at Outokumpu's concentrators.INTRODUCTIONVarious methods have been developed for measuring mill load; weighing, noise, etc. Weighing is one of the most reliable methods but installing the sensor to existing mills is often difficult. Besides the load measurement does not indicate the volumetric filling if the specific gravity of the mill feed fluctuates. Noise measurement has often failed with its sensitivity to various disturbance sources.As known, the power draw measurement is one of the most accurate measurements in grinding circuits and therefore it has been utilized in sophisticated control, e.g. in power peak seeking algorithms for maintaining maximum grinding efficiency.About 10 years ago power oscillation measurement was developed at Pyhasalmi concentrator. In this method the amplitude of the oscillation caused by the lifters was measured. The oscillation amplitude and the mill filling has quite a good correlation and together with the power draw measurement it could be used for maximizing mill throughput (Koivistoinen and Miettunen, 1989). The main difficulties in this method were that the dependence between mill filling and the amplitude is unlinear and that the dependence also is individual for each mill.The method developed during 1989-90 is also based on the power oscillation but on its phase shift. In principle level of the material in a mill is measured. The method has been successfully used for maximizing throughput at Pyhasalmi and Enonkoski concentrators and at Harjavalta slag concentrator."

Jan 1, 1991

By G. J. Borbely, E. A. Devuyst, V. A. Ettel

"A new method for oxidative destruction of cyanide in industrial waste waters and slurries, such as gold mill barren liquors, tailing slurries and flotation tailings has been developed at the Inca research laboratories. Rapid decomposition of cyanide and related species is attained by treating the waste waters with a mixture of S02 and air at controlled pH and in the presence of a small amount of copper which acts as a catalyst. The approach selectively oxidizes cyanide and metal cyanide complexes, and also removes iron cyano complexes which are not removed by alkaline chlorination.The new method is shown to be less reagent intensive and therefore more economical than alkaline chlorination for treating gold mill and flotation waste waters. INTRODUCTIONOver 90% of the gold mined in Canada is extracted from the ore by ""cyanidation"". Wastes from the process consist of tailings which contain free cyanide, cyanide combined with heavy metals, thiosalts and thiocyanates. Because of the concern over the effect of toxic cyanides on the environment, all cyanide containing effluents will have to be treated in the future to meet certain government set concentration limits."

Jan 1, 1982

By David A. Lee

It was estimated in Chemical Week1 that the uranium fuel requirements for the U.S. Electric Utility Industry by the mid 1980's would be about four times that-of what it is today. This corresponds to approximately 45,000 tons per year of 'yellow cake' - of which a good portion is represented by ammonium diuranate - vs. the 11,700 ton total estimated for 1975. Perhaps just as significant is the 40-fold increase in thirty years projected for the entire world since 1970. Thus by the year 2000. 'yellow cake' production could be in the order of [3]50.000 short tons annually.2 'Yellow cake', so named because of its inherently bright yellow color, is a finely divided precipitate that can be formed after the leaching step when refining uranium ores. Feed solids enhancement then occurs to at least 50% by weight using filters or centrifuges This is followed normally by drying and then calcining with the conversion of ammonium diuranate to triuranium octoxide represented by the following equation: [9 (NH4)2 U2 07 heat 14 NH3 7 + 15 H2O7 + 2N2/ + 6 U308 4] Theoretically, assuming 100% conversion every 100 kgs. or 100 lbs. of ammonium diuranate will result in 90 kgs. or 90 lbs. of triuranium octoxide.

Jan 1, 1976

By Larsson Lars-Erik, Rani Isa, Martin Jönsson, Håkan Bredenberg, Mats Larsson

"IntroductionSteel Core Piles are used extensively in Scandinavian countries, where hard rock is found within reasonable depths. A steel core is cast into a drilled steel tube casing and a rock hole is extended below the casing. This pile type is considered a very reliable type of pile, and for urban environment it has several advantages compared to other types of piles. One critical phase of the installation is the drilling of the casing. Usually a DTH (Down The Hole) hammer is used. Drilling in fine grained soils, e g silt, below the ground water level, may give rise to an excessive volume of soil material flushed up from the point of the casing, resulting in unacceptable settlements around the pile installation area.Using a new method for drilling of the casings, the ELEMEX-method has proven to significantly reduce the risk for such problems. In the paper a case record from a ground improvement project in central Stockholm is described. Ground settlements around the drilling area were carefully monitored over a longer period. Both the new drilling method and the conventional DTH casing drilling method where used, so that the corresponding ground settlements could be compared. Settlement records and comments are included in the paper.The paper also gives a description of the project. The installation of new piles and foundation constructions cover a whole city block in Stockholm downtown. The reason for the replacement of the old, damaged wooden piles were due to their destruction caused by a long time lowering of the ground water table. The paper gives a description of the new drilling method as well as an overview of usual urban foundation issues and their solution in Sweden, Finland and Norway.Drilled Foundation MethodDrilled Foundation, using drilling methods originally developed for drilling of large diameter rock holes, is today a standard method for the installation of piles, tiebacks, drilled pile walls and other foundation components, especially in urban built up areas where other techniques as drop hammers, augers, vibratory hammers and other equipment fail to meet the requirement, se ref(1). Drilled foundation is for example used for"

Jan 1, 2014

By Catalin Florin Petre, Elahe Ghasemian Langeroudi, Abdelaaziz Azizi, Éric Proulx, Caroline Olsen, Paul Blatter, Faïçal Larachi, Claude Gagnon

"The recovery of gold from ores is often accompanied by the release of other species in the leach solution. This state of affairs leads to depleted free cyanide levels in the slurry. Therefore, separation and quantification of these cyanicides and free cyanide at different stages of the cyanidation process as well as in waste solutions is crucial to provide mitigation tools by preventing leaching of deleterious metals for environmental considerations.COREM and the research group of Prof. Larachi have been working together on the control of gold passivation and cyanicides during cyanidation for several years. Previously, a first capillary electrophoresis (CE) protocol for the speciation of sulfur and cyanicides (SCN-, Cu, Fe) during cyanidation of gold complex sulfide ores was developed and validated for assessing industrial process water.The separation of zinc cyanide complexes used to be confronted with a number of difficulties due to the weak and/or undetectable cyanocomplexes in formally available CE protocols. Moreover, according to our knowledge, no direct CE protocol exists to separate free cyanide. Therefore, a new study aimed at developing a second CE protocol for the detection and quantification of cyanide complexes of zinc and nickel as well as of free cyanide in the cyanidation process water.To achieve this goal, six common carrier electrolytes such as pyridine, trimellitic acid, 4-methylbenzylamine, sodium chromate, phthalic acid and tris base were studied, using an indirect UV detection method. The best results were obtained using sodium chromate for which all ions were successfully separated and quantified. In addition, the effect of electric field strength, injection volume, electro-osmotic flow (EOF) modifier and background electrolyte (BGE) concentration were examined, while peak height, peak area and noise were considered for optimization.As a result, the new protocol is expected to complete the initial CE protocol by detecting cyanide complexes of zinc and nickel as well as free cyanide. Moreover, analytical determination of free cyanide in the presence of weak cyanide complexes achieved by the new protocol was also compared to conventional titration using silver nitrate solution. This new CE protocol will contribute to applied research and help plants to better understand and eventually control the behaviour of cyanidation circuits."

Jan 1, 2011

By P. James

"INTRODUCTION High sulfate (SO4-2) levels often occur in MIW (mining influenced water) either as the result of oxidation of sulfide minerals exposed by mining activity or by deliberate addition – commonly by sulfuric acid (H2SO4) use in hydrometallurgical leaching activities. Increasing regulation of sulfate discharge is creating new pressure to treat or mitigate sulfate release to prevent its entry into the environment. Current treatments include precipitating as gypsum during lime treatment, filtration separation using membranes such as reverse osmosis and nanofiltration technology, and biological elimination via methods like constructed bioreactors. Blue Planet Strategies (BPS) focuses on improved resource utilization targeting electrolytic treatment and waste conversion into resources and has now demonstrated that its proprietary DEMET™ (Dynamic Electrolytic Metal Effluent Treatment) platform can also remove sulfate from target streams as a byproduct of its usual primary treatment focus points of metal species elimination and/or pH adjustment.[1-6] This powerful new capability can mitigate sulfate contamination and recover the sulfate in a useful and potentially saleable form as a byproduct of improved primary treatments focused on enhancing production or treating waste. This provides a new treatment opportunity and value proposition for lowering overall sulfate consumption/addition or creating new revenue to defray conventional treatment costs. The DEMET Alternative DEMET utilizes a patented electrolytic technology platform employing proprietary dynamic high surface area electrodes in innovative configurations to achieve a variety of novel selective chemistries. DEMET‘s unique elements can yield higher processing rates at practical efficiencies, lower energy consumption, plus improved processing stability and lower maintenance requirements due to enhanced resistance to cell fouling and shorting; while also thwarting cross stream (catholyte vs. anolyte) contamination. Consequently, DEMET can provide a superior, extremely versatile, and cost-effective electrolytic treatment option where a multitude of FEED and PRODUCT stream combinations might be employed in comparison to traditional tankhouse electrolytic cells. Secondary reactions (Figure 1A) which could also occur at the cathode (plating/electrowinning, precipitation/scale formation, etc.) are controlled through process tailoring and operation parameter selection. Additionally, DEMET‘s innovative dynamic system mitigates potential fouling and electrode occlusion or shorting challenges which could occur when process particulars demand some of these secondary side reactions occur."

Jan 1, 2015

By Thomas F. McLoughlin, David K. Hylbert

A new method of satellite imagery analysis has been developed during underground mine roof research. Landsat positive film transparencies were projected onto topographic base maps to scale and lineaments enhanced with a Ronchi grating (method A). Thirty-five millimeter slides of video-enhanced scenes were also projected onto base maps (method B). Both methods permit direct plotting of lineaments to scale and direct correlation with surface and subsurface data wing transparent overlays.

Jan 1, 1981

By B. Cousins

Flotation reagents are critical to the optimum performance of flotation circuits. How a flotation reagent performs within the first few cells of a flotation train is a key indicator of how well it will perform throughout the entire circuit. A method to compare reagent performance was recently developed by Ashland Water Technologies. The procedure involves collecting a timed sample of concentrate from each cell and then measuring the volume of the settled solids. An estimate of the percentage of concentrate collected from each cell can then be mathematically determined, providing an understanding of the recovery changes in each cell. Data from trials at a coal flotation circuit are used to demonstrate the method's validity.

Feb 27, 2013

By Jorge Cárdenas, José Luis Hurtado

The critical distance determination test through direct recording for the mine in Phase 03 was carried out in January 2024, and in it the vibration and pressure models were obtained for the Sedimentary breccia unit. The method of obtaining the records is based on the capture of individual pressure waves generated by distant loads, sequenced in periods of 600 ms for easy identification. The test set up corresponds to a variation of that used to obtain the vibration model, and uses 08 wells for loads and 04 for instrumentation. The results apply a safety factor of 1.2 and 1.5, being 16,000 PSI and 13,250 PSI respectively. The values are valid for any distance greater than 5.5 m, this being the minimum established between wells for loads according to the configuration defined in the field, also considering that in 5.0 m of instrumentation the section of the drill hole with the sensor called S1 collapsed. The results of the analysis of the test, generated with Heavy Anfo 82 explosive, with a final density of 1.15 g/cc, are presented. The results of the modeling and generation of the graphs and tables presented show behavior in line with the concept of scaled distance. It is important to consider that in water conditions there is a high impact by the condition, which causes the records to be higher than those expected in dry conditions and present less variability. It is for the above reason that the row corresponding to distance with safety factor 1.5 is declared valid. The results are only valid for the rock analyzed, whose medium is homogeneous and constant in terms of lithological composition and that present similar resistance characteristics, fracture frequency and water table levels. As future steps, the objective is to quantify the increase in pressure generated between wells by analyzing time and sequence factors. This analysis aims to explain the occurrence of dynamic pressure events in areas where critical safety distances are observed.

Jan 21, 2025

By Guillermo Lazcano Ríos, Jorge Parvez Aguirre, Alejandro G. Díaz Berríos, Felipe Rodriguez Alveal

Codelco's Chuquicamata Underground Division (DCHS) faces issues due to collapses in its subsidence streets, which hinders the advancement of the subsidence front and leads to the loss of areas and reserves. To address these issues, DCHS and Orica have developed a new excavation methodology based on pre-loading explosives in high drawbell. This methodology involves creating a high drawbell extending from the floor of the production level to the ceiling of the subsidence level, divided into two phases: upper and lower. A resin stemming is used to separate these phases. The excavation strategy adjusts to variables such as reception volume, fluffing, and excavation geometry, involving vertical pre-loading of the explosive and the use of a separating element between the phases. The test aims to validate the new excavation methodology and the retaining element in the rock mass, evaluating aspects such as drawbell geometry, impact on the rock mass, damage to the retaining element, and fragmentation. Wireless electronic detonators are used in the upper phase to improve safety by eliminating the need for physical connections, while traditional electronic detonators are employed in the lower phase. Low-density bulk emulsion is applied to minimize the impact on the Crown pillar and extraction point, and higher-density explosives are used above the subsidence level to ensure good caving. Results showed that the blast achieved 86% conformity with the theoretical design. Resin stemming allowed for 100% effective detonation in the upper columns, and the fragmentation obtained was 5.44 inches, which was less than expected. No damage to the Crown pillar was observed, and the explosive quality met standards. This technique has proven to be effective and viable, suggesting the possibility of eliminating the subsidence level in future levels, resulting in savings, and providing greater stability to the rock mass.

Jan 21, 2025

By José Aparecido Pereira

The innovative methodology developed by the author allows the elaboration of an Angle Roll Pass Design based on the practical observations of the rolling process and applies mathematical criteria, using the Ekelund´s formula supported by Advanced Excel tools (Reach Goal, PROCV-PROCH, Macros) and AutoCad. The first step is the definition of the number of stands, roll dimensions, gear boxes reduction, initial stock, average reductions, spread factors, finishing speed and type of grooves. For each pass are calculated: bite angle, spread, section reduction, lost and gain of temperature, separating force, speed, torque and motor power. After these calculations and checking of the parameters, the program calculates the dimensions of the passes transforming the flat passes into shaped ones. With these dimensions it is possible to draw the grooves using AutoCad and check section reductions. This methodology was already used for the development of a new project and also to check the parameters of existing ones, with comparison of the results and has shown to be reliable in real and tested projects. It is an innovative process that is not available in known literature.

Oct 1, 2019