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By Thomas M. Barczak

Advancements in support technology have occurred to a large extent because of the demands of the mine operators. Shield supports are no exception. The most notable changes in shield technology in the past decade have been increases in shield capacity and life expectancy, which have increased by a factor of 4 and 7 respectively since the inception of the shield support 25 years ago. The purpose of this paper is to set goals for the future generations of longwall shields. These goals include: (1) 100,000 cycle life expectancy, (2) improved hydraulic diagnostic capability, (3) smart load control with adjustable setting pressure algorithms, (4) composite material design to reduce weight and increase shield width, (5) constant set leg cylinder design, (6) improved joint design to reduce wear and stress, (7) advancements in leg cylinder socket design, and (8) an instrumented shield to measure in-service structural component loading. These design issues will continue to push the envelope in longwall shield technology that has provided the safest and most productive mining system employed in the history of mining. In preparation for this, a historical examination of shield failures is made and recent trends in shield design are evaluated. Design practices to improve structural margins of current designs are also addressed.

By Wilton Johnson

Native asphalt was produced by three companies in two States, Texas and Utah. Bituminous limestone, used primarily as a paving material for street and road repair, was produced by one firm, R. L. White Co., Uvalde County, TX. Gilsonite, a solidified hydrocarbon found only in Colorado and Utah, was mined by two firms, American Gilsonite Co., a division of Chevron Resources Co. (a subsidiary of Standard Oil Co. of California), and Ziegler Chemical and Mineral Corp. Hydrocarbon Mining Co. (a subsidiary of Oberon Oil Inc., a Utah corporation) closed its mining operation during the year.

Jan 1, 1988

By N. Sahay

Open fire in coal mines is one of the most serious threats to miners, as well as to the mine. Open fire can often be effectively dealt with by prompt local action, otherwise it very quickly becomes uncontrollable. In one incident, none of the available open fire control technologies, viz., water deluge and sprinkler systems, high-expansion foam, high-pressure high-stability nitrogen foam, water misting, and ventilation and pressure control techniques, were effective for saving the mine without sealing from surface, since the fuel-rich environment prohibited underground access due to the methane explosion hazard. The authors have developed a methodology for dealing with advancedstage open fires underground by the application of a modified ventilation control technique. It is based primarily on a better understanding of the behaviour of open fires, proper diagnosis of the problem, application of judicious ventilation control techniques, and selection of suitable fire indices for assessing the status of an open fire. This methodology was used to successfully control an open fire in Surakachhar 3 and 4 incline mine Surakachhar, central India. The fire area was sealed underground and production subsequently resumed in record time. The paper discusses the behaviour of open fires, particulars of the mine, diagnosis of the problem, experimentation methods, and the results obtained.

Jan 1, 2014

By Robert L. Virta

This U.S. Bureau of Mines paper discusses the structure of the talc industry, talc production, processing of talc ore, applications and demand for talc, and the outlook for the talc industry.

Jan 1, 1989

By A J. Falconer

Two magnetic parameters are proposed as a basis for the assessment of ironsands beneficiation. The parameters are determined for raw sand prior to dredging and for magnetic separator head feed over a production period of five months. The relationships between these parameters and the performance of the magnetic separators are examined to establish the value of magnetic assessment compared with the traditional soluble iron assay method. The results illustrate that the first parameter, true magnetic fraction (TMF). Has a value superior to that of soluble iron when relating raw sand grade calculated by triangulation to magnet performance. In terms of the relationship between magnet head feed grade and magnet performance, TMF and soluble iron perform equally as assessment parameters. For the ironsands mined during the five month period, the second magnetic assessment parameter, composite fraction (CF), is shown to merely reflect TMF and offers no additional information for assessment. Conclusions are that true magnetic fraction has many advantages over soluble iron in terms of time and cost of determination and that it is a meaningful and reliable parameter upon which to base all calculations relating to the mining and beneficiation of ironsands.

Jan 1, 1980

By Zia Zafir

Design of the deep foundations for the loads imposed by lateral spread include the estimate of the pressure applied by the liquefied material as well as amount of anticipated displacement. In the absence of a non-liquefiable cover over a liquefiable layer, it is possible to design the foundation system just for the additional pressure applied by the flow slides. On the other hand, if a non-liquefiable layer exists above the liquefied zone, the foundation should be designed for anticipated movements. To completely account for liquefaction and/or lateral spread and their interaction with the deep foundation system, a coupled soil-structure interaction (SSI) analysis should be performed. However, a complete SSI analysis may not be feasible for most of the projects. This paper will present recent advances in analysis techniques and simplified methods to design deep foundations for liquefaction and lateral spreading. In addition, a case history of the Rancho California Bridge in southern California located within 1 km of the active Elsinore fault will be presented. One of the bridge abutments is underlain by potentially liquefiable layers. The pressure applied by the liquefiable layer was estimated to be greater than the shear capacity of the 36-inch CIDH piles designed for the abutment. However, with limited ground improvement and more careful analyses incorporating structural effects of CIDH piles, resulting design and construction resulted in a factor of safety greater than 1 against slope failure. The recommended approach was generally consistent with the recently published, and AASHTO sponsored, NCHRP 12-49 project regarding seismic design guidelines for new bridges and the effects of seismic displacements against bridge foundations.

Jan 1, 2006

By J. A. Finch

"A method of sampling and presenting bubbles for imaging for use in full-size flotation cells is described. The device (bubble viewer) comprises a tube attached to a sealed glass viewing chamber. The assembly is first filled with frother-containing water (to prevent coalescence) and the tube immersed at the desired location below the froth. For a few minutes bubbles are collected in the viewer free from slurry and are readily imaged. To reduce bubble overlap and the problem of defining the plane of view, the viewing chamber has a sloped side. Bubbles rise, encounter this slope, spread into a single plane and slide up. This simple expedient virtually eliminates overlap and provides an unambiguous focus plane - the underside of the sloped glass. The bubble image is captured and processed to give size data. The bubble viewer has been employed at several concentrators on different types of flotation cells. Examples of the images are given. The impact of position in the cell and the effect of changing gas rate on bubble size are illustrated. This technique provides a sensitive measure of the effects of process variables on bubble size.INTRODUCTIONDespite the extensive use of flotation in the mineral processing industry, the methodology employed for cell design is largely based on empirical rules rather than on first principles. One of the main reasons for this state of affairs is that the local flow structures encountered in industrial-scale machines are very complex. These flow structures are difficult to simulate under the controlled conditions of the laboratory and the difficulty to solve the mathematical models that treat the randomness of such flows also mean theoretical treatment is limited. Understanding flotation cell hydrodynamics requires reliable data, which involves the implementation of measurement techniques capable of performing both at the laboratory- and the industrial-scale, In addition, it is desirable that such techniques are amenable to automation to reduce extensive manual intervention in the data collection process."

Jan 1, 2002

By Gunhild Hennum, Tewodros Tefera, Gisle Håland, Annette Jahr

"Abstract The Gudrun field is located west of Stavanger in the North Sea at water depth of 109 m. A jacket substructure was selected to support the topside and was installed in 2011. The jacket shall be able to support 16 of 0.762 m (30 in) diameter conductors and is equipped with a drilling deck to allow for pre-drilling by a jack-up rig through the jacket. In general the soil conditions below mudline comprise of a thin top layer of very loose to dense sand overlaying several layers of sandy clay, ranging in stiffness from firm to hard. Below some 30 m depth the soil consists of layers of medium dense to dense silty sand overlaying very hard sandy clay containing thick beds of sand to 100 m depth or more below mudline. The jacket is secured to the seabed by twelve 2.438 m (96 in) diameter steel pipe piles, three at each pile cluster located at the four legs of the jacket at sea floor. Different design methods were used to determine the pile penetration depth. Pile drivability was evaluated using best estimate and upper bound soil parameters. The pile driving and blow count record show that the target penetration was reached as predicted. This paper discusses the different methods used to determine the pile capacity, target penetration depth and the drivability analyses made for the Gudrun jacket piles. The soil resistance during pile driving is back-calculated from the pile installation data and compared with the prediction made.IntroductionThe Gudrun platform is located west of Stavanger in the North Sea at water depth of 109 m. A jacket substructure was selected for the Gudrun platform. The general Gudrun platform jacket configuration is to a large extent dictated by the topside layout, the requirements for support points enclosing the well slots and access for the jack-up rig. The Gudrun platform jacket is a traditional 4 legged structure with a vertical side towards the jack-up rig. At the seabed the jacket is quadratic with a base dimension of 40 by 40 metres. Figure 1 shows the Gudrun jacket during load-out from the fabrication yard to the transport barge. At the site the jacket was lifted off the barge, upended and placed on the seabed by the installation vessel. The jacket is secured to the seabed by twelve 96"" (2.438 m) diameter steel pipe piles, three at each pile cluster located at the four legs of the jacket at sea floor. The target penetration of the piles is 47 m."

Jan 1, 2014

By G. S. Rice, H. O. Howarth, Greenwald. H. P.

"Electricity as a means of transmitting power was introduced in coal mines of the United States about 1891 for both haulage and coal cutting, only a few years after electrical haulage was first installed on street cars. At first, the hazards of electrical ignition ere not appreciated and the general use of open lights and black blasting powder made the possibility of electrical ignition of fire damp seem small by comparison.5 The possibility of igniting coal dust directly by electric sparks or arcs had not been considered.In the nine years prior to 1900, the progress of introducing electricity underground was slow, except that it was used for lighting shaft bottoms. Electricity had to contend with the more general use of compressed air for coal-cutting machines and, in mainline haulage, with the use of mule-teams and endless and tail-rope systems. During this period, great improvements were made in electrical apparatus, in surface installations as well as in mines. By 1900, therefore, the technique of applying electricity in mines had so far developed that it rapidly drove out the use of compressed air in coal mines because of the comparative ease of its installation and the marked economic advantages of its use over that of compressed air in practically all kinds of mining machines except percussion. rock drills.At this time, however, little thought was given to the hazard of indiscriminate use of electricity causing explosions and fires, and the possibility of electricity causing direct ignition of coal dust had not been considered. On December6, 1907, however, the Monongah, West Va. mine explosion occurred. This was the greatest mine disaster this country has over had, 361 men being killed. Although: there was much diversity of opinion, as to the origin of the explosion, many well-informed engineers concluded that the cause was ignition of coal dust do to wreckage of a runaway trip in a rope haulage entrance slope. This slope also served as a ventilating and it extended from the level of the coal bed to the surface. The runaway trip tore down electric cables and stirred up a cloud of dust when it was wrecked at the bottom of the slope. The dust was probably ignited by the electric arcing that occurred when the wires were knocked down. (Another but less probable source of ignition was the open flames of miners lamps.) From the foot of the slops the explosion appeared to have travelled into the mine, spreading as it went. If this ignition of coal dust was the origin of the explosion, it occurred on pure intake air entering directly from the surface."

Oct 1, 1930

By Lawrence P. Goldfarb

The City of Alexandria, Virginia, Public Safety Center (PSC) is a 64,000 square foot facility that houses the Police Department, Office of Sheriff and the Office of Magistrate. In addition, the center includes a detention facility for local and federal inmates, operated by the Sheriff. The PSC is composed of a 3-story building to the west and a 6-story building to the east constructed on a landfill in a wetland area in the flood plains of hunting Creek. The existing ground floor of the 3-story building is a floating slab-on-grade, with the interior and exterior columns, exterior walls and upper floors all supported on belled, drilled shafts. Portions of the floating first floor slab have undergone excessive settlement due to the apparent consolidation of the underlying organic soils. The magnitude of the settlements of the floating first floor slab is sufficient to require replacement of the slab and relocation of a portion of the facility. The rehabilitation was complex and required staged construction, consisting of constructing Auger Pressure Grouted (APG) Piles in low overhead conditions. This paper summarizes the geotechnical conditions that lead to the excessive settlement of the floor slab, the construction of the (APG) Pile foundations in low overhead conditions and the evaluation of potential future settlements.

Jan 1, 2009

By M. van Schoor

Coal remains South Africa?s most abundant and cheapest source of energy, and there is an ever-increasing necessity for optimal and safe extraction of the remaining reserves. Increasing focus on cost-effective mining and zero harm to the environment and miners has resulted in a shift in attitude towards the application of geophysics in local coal mining and exploration. Furthermore, technological advances have contributed to geophysics being embraced more readily by the coal mining industry, compared to a decade or two ago. Predictably, the growing interest in geophysical technologies has also created a need for education and training in the basic principles and application of geophysical methods, as local coal mining companies generally do not have in-house geophysicists. Consequently, the Coaltech Research Organisation?s Geology and Geophysics working group forum compiled a textbook aimed at addressing this need: to produce a guide for applying geophysics to coal mining problems in South Africa. The target audience for such a book would be coal geologists, mine surveyors, mine planners, and other mining staff with limited or no geophysics background. This paper provides a very brief overview of the book by summarizing key sections and selected examples. In doing so, the value of geophysics to solving a range of coal mining and exploration problems is highlighted.

Jan 1, 2014

By K Ehrig, J Griffith

An extensive suite of elements are routinely assayed on all resource drill core samples to assist in deposit scale resource definition, local mine scale delineation of ore zones, and ore characterisation for the planning and scheduling of mining and processing of ores at Olympic Dam. This paper discusses a deposit scale geochemical relation that can be used by mine geologists to find more high-grade ore at the local mine area scale at Olympic Dam.A 3D grade shell representing 0.8 per cent Cu was created for a mine area using drill hole assay data. This defined the geometry of the ore zone. The Cu-grade shell was then overlain onto the existing resource block model to evaluate the relationships between the Cu-grade shell, copper and other elements. The strongest correlation was between copper and manganese. The block model showed a dramatic decrease in the concentration of manganese just below the below the Cu-grade shell.Several drill holes that intersected the Cu-grade shell were selected to evaluate the copper manganese relation at the drill hole scale. As expected, the individual drill holes displayed a strong inverse relation between copper and manganese. A geochemical footwall was then modelled representing 0.1 wt per cent Mn. Using both the Cu– and Mn-grade shells, several drill holes were designed/drilled and all hit high-grade copper.For the vast majority of the deposit the inverse relation between copper and manganese is valid; however, in areas with intense chlorite alteration (related to amounts of mafic to ultramafic rocks) this relation is not as strong, due to increased manganese in the rock mass. Even though using the copper manganese relation as a drill targeting method was not always as reliable in a few small areas of the deposit, it demonstrates the value of using existing assay data integrated with the resource block model to discover local mine scale geochemical relationships which can be used to more effectively design drill holes to discover high-grade ore at Olympic Dam.CITATION:Griffith, J and Ehrig, K, 2017. Using existing data to improve the delineation of ore at the Olympic Dam Fe-oxide Cu-U-Au-Ag deposit, in Proceedings Tenth International Mining Geology Conference 2017, pp 321–326 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By Richard Short

Shallow rainfall-induced landslides in residual and colluvial hillslopes and steep embankments are a common occurrence in many settings [1, 2, 3]. While occasionally posing a threat to property and life-safety, they more often present an ongoing maintenance problem and can lead to the initiation of larger failures. Typically, these slides consist of 2 to 4-foot thick translational movements of silty and clayey soils down slope through the reduction of strength from increases in pore water pressures. Direct surficial infiltration and indirect groundwater seepage are the normative triggers for failure. In the residential community of Blackhawk, California, located east of the San Francisco Bay, these types of landslides are a common occurrence (Figure 1). However, shallow landslides have also been a repetitive and constant problem along many state highways where steep embankments have been constructed in close proximity to busy thoroughfares. Given the real threat to property values in residential and commercial settings and the constant maintenance problem posed to lifeline structures such as utilities, roadways, and pipelines, new methods to deal with these landslides are needed.

Jan 1, 2007

By D. Imeson, T. Grammatikopoulos, M. Aghamirian, M. Oliazadeh

"More than 70% of potash is produced worldwide by froth flotation. Flotation of potash was developed in the early 1930s. Amines are widely used for flotation of sylvite (KCl) from halite (NaCl) and insoluble materials such as clays. Amine collector is also absorbed by clays. Therefore, clays are usually separated by scrubbing and de-sliming prior to flotation. Alternatively, slimes can be floated ahead of potash flotation. Flotation recoveries of sylvite are commonly in the range of 85%, while losses can occur in slimes, flotation tailings and make-up of process brine. Ores containing free coarse-grained sylvite are generally screened, whereas both fine and coarse fractions are conditioned and floated separately. The unique features of potash flotation include solubility of sylvite in water, the size of particles floated and fast kinetics. Particles up to 2.3 mm can be floated and about 50% of flotation feed can be removed in the rougher stage in few minutes. The main challenges in potash flotation are the recovery of potash from slimes, flotation efficiency in the presence of carnallite and recovery of coarse potash grains. A review of potash flotation shows that there is still room for improvement in both coarse and fine potash flotation. The present paper reviews the most significant flotation parameters including reagent type and dosage, flotation circuits, flotation equipment size and new developments in potash flotation. The latter include new reagents, flotation technologies (Hydrofloat, Jameson and column cells) larger flotation cells and slimes flotation.INTRODUCTION Potash is the common industrial term for potassium in various chemical combinations and minerals soluble in water. About 90% of potash produced worldwide is used as agricultural fertilizers. Flotation is the main treatment process of sylvinite (KCl-NaCl) ores for recovery of sylvite (KCl). Potash concentrate should contain a minimum of 95% KCl and be relatively free from 0.2 mm KCl fines. The flotation process for beneficiation of potash ores was developed in United States and Russia concurrently in the early 1930s. In 1934, Potash Corporation of America applied flotation process in a commercial scale (Tippin R.B. and Huiatt J.L). In the initial application, halite (NaCl) was selectively floated by employing lead chloride as an activator and soap as collector. The sylvite concentrate was reported in the cell underflow."

Jan 1, 2012

According to the data provided by the most recent European Survey on Working Conditions, roughly 25 per cent of the European working population is exposed to mechanical vibrations for no less than one quarter of the work shift duration, while around ten per cent are exposed for the entire work shift. The occupational exposure to whole-body vibration (WBV), in particular, represents a major health risk in mining, quarrying and civil excavation activities. In accordance with European Directive 2002/44/EC, the latest version of the Italian law on physical risks has recently confirmed the possibility of using relevant literature data on vibration magnitude in order to evaluate personal occupational exposure (vibration database or data provided by the manufacturer). Still the alternative option, based on field measurements, represents the most appropriated method of risk assessment, as it accounts for the actual operating condition at the workplace; actual operator and vehicle under investigation and specific working cycle. The article discusses the vibration measurements taken on a number of heavy machinery (excavators, loaders, trucks, dumpers, etc) employed for talc extraction in a mine located in Sardinia and the resulting personal exposure for the drivers. The assessment was carried out in accordance with the specifications of ISO 2631-1 and EN 14253.

Dec 6, 2010

By Paul J. Axtell

The results of in-situ geophysical cross-hole tests on improved soil by soil mixing (SM) and jet grouting (JG) are described. This testing was conducted on soil improved by SM and JG columns constructed in the downstream free-field of Tuttle Creek Dam near Manhattan, Kansas as part of the seismic retrofit. Results of similar geophysical testing performed on untreated soil in the vicinity of the Downstream Test Program (DTP) area, as well as beneath the embankment at several locations, are also described and used for comparison purposes. In-situ shear moduli are also compared with those determined in laboratory resonant column tests. The increase in stress wave velocities and associated shear moduli by SM and JG treatment are presented for use in liquefaction potential and seismic deformation analyses of SM or JG treated soil. This data is required to determine the decrease in liquefaction potential and earthquake-induced permanent deformations due to SM or JG with respect to that of untreated soil.

Jan 1, 2008

By C. Musingwini

The subject of optimal planning of level and raise spacing for inclined narrow reef deposits has received intermittent attention over the years because the subject matter is inherently complex. Previous work has approached the problem as simply that of simultaneously minimizing the total excavation and haulage cost associated with the development workings. However, when level and raise spacing are altered, other factors such as productivity are negatively affected, thus requiring a delicate trade-off of contradicting planning or optimization criteria. The paper concludes that the problem is actually of the multi-criteria decision analysis (MCDA) type, contrary to traditional thinking that the planning problem is achieved solely by minimizing waste development.

Jan 1, 2010

By T. O. Hagan

A simulated rockburst experiment was conducted underground at a deep level gold mine. This was done by means of a large explosion detonated in solid rock close to a tunnel sidewall. The resultant shake-out damage is typical of that associated with a small seismic event in close proximity to a tunnel that is subjected to the estimated field stress, as in this case, of 50 MPa. The experiment involved: ?the design of a blast to mimic a seismic source ?seismic monitoring using a dense seismic array ?high speed video filming ?a study of rock mass conditions (fractures, joints, rock strength etc.) before and after the simulation using mapping and ground penetrating radar ?special investigations to evaluate the mechanism and the magnitude of the damage ?a study of support behaviour under excessive dynamic loading.

Jan 1, 2001

This paper provides an overview of possible approaches for structuring the ventilation systems for mines that will become operational within the next decade. Features addressed in the paper include: aspects of airway design and layout in the absence of centralized vertical return shafts, the impact of using diesel-powered trackless equipment in conjunction with conveyor belts in the development and production phases of the project, and the need to balance increasing electrical power costs against the requirement for reduced capital expenditure. The paper provides brief descriptions of the strategies employed in real-life situations and presents an overview of various operational parameters affecting the design of ventilation systems that will be used as ?platforms? for much deeper mines in the future.

Jan 1, 2007

By A. R. T. Denues

The Explosives Division of the Bureau of Mines, United States Department of the Interior, is investigating cushioned blasting at the Explosives Testing Station, Bruceton, Pa. The general interests of this investigation are practical and relate particularly to safety. The immediate concern is an application of cushioned blasting in coal mining In cushioned blasting, various means are employed to reduce the intensity of the application of energy in an explosive action in a borehole. The primary object is to increase the efficiency of the use of explosives.

Jan 1, 1940