Search Documents

By J Kleynhans, D Vermeulen, V Cogho

A number of rehabilitated open cast coalmines in SA are already decanting. The paper focuses on the situation at one of these mines where the following information exist: monthly decant rates and rainfall; sulfate concentrations of the decanting water; water level measurements inside the mine prior to decanting; ABA analyses; information about the rehabilitation (drainage slope, vegetation, soil used). A 2D-model was constructed for the mine and calibrated against six years of flow data. About 85 per cent of the decant outflow rate comes from direct recharge on top of the rehabilitated mine while the other 15 per cent is derived from lateral groundwater inflows. The estimated recharge value was 17 per cent of the rainfall. Measured sulfate values showed that the sulfate generation rate for the mine was in the order of 7 kg/ha/d. Conclusions from the study are:most of the water decanting from rehabilitated open cast coal mines is derived from recharge via rainfall; given a specific sulfate generation rate, then: the lower the recharge the less the decant rate but the higher the sulfate concentration of the decanting water and vice versa; future prediction of the decant rate must be stochastic according to expected percentile monthly rainfall values; and as a first assessment of the predicted sulfate concentration of decant water from rehabilitated open case mines, the 7 kg/ha/d sulfate generation rate can be used.

Jan 1, 2003

By T. M. Kohler, G. L. Finfinger, D. M. Hyman, A. T. Iannacchione

The Bureau of Mines measured methane emission rates from an advancing salt face ranging from 15 to 56 ft3/ton (0.5 to 1.8 m3/t). Small room size, use of a continuous miner, and a well-defined ventilation system made possible air velocity and methane concentration measurements, These measurements, representing data from 18 production days, were con- ducted in an area of abnormally low grade salt, Methane emissions occurred primarily during the advance of the salt face by continuous miner.

Jan 1, 1982

By J. A. Organiscak

The U.S. Bureau of Mines recently conducted an investigation into the amount of respirable and quartz dust generated while mining rock in coal mines by continuous and conventional methods. The study was made at two mines that use both continuous and conventional mining. Results show that continuous mining produces 1.2 to 3 times more respirable dust, and 6.7 to nearly 15 times more quartz dust than conventional mining.

Jan 1, 1989

By A. S. Malicsi, I. Iwasaki

Differential flotation of bulk sulfide concentrates from Duluth gabbro into copper and nickel concentrates could be implemented by first destroying the hydrophobic coating with ozone and then by recovering the copper concentrate with a copper-selective collector. A number of parameters involved in the use of ozone, such as the sequence and the conditioning time of ozone treatment, the pulp pH, and the level of xanthate addition, were investigated.

Jan 1, 1986

By T. Smales, P. L. Wright, K. Barron

The results of field measurements using an air injection technique to investigate the integrity of three pillars in the Mclntyre Mines Ltd. 114 seam at Crande Cache, Alberta, are reported. These pillars are shown to be stable and an estimate is made of the strength of these pillars. Using these results, together with Hustrulid's pillar strength formulae, a general pillar strength equation for the 114 seam is developed. This equation takes into account the probability of failure that may be deemed tolerable within the design requirements. The variation of the minimum pillar dimensions with depth below surface for uniform pillar layouts is then examined for a range of tolerable failure probabilities. A general equation of the form B = 2.60 +B Z relates the minimum pillar design width, B metres, with the overburden depth, Z metres, where B is a parameter related to the tolerable failure probability. This equation only applies for 3.05m high pillars with 6.lm wide entries. Finally, the question of what failure probability is tolerable within the design of mine pillars is discussed. This will depend on the support role required of that pillar and the anticipated period over which the pillar must perform that role. Five categories of coal mine pillars are defined, each with a somewhat different role to perform. Tentative design criteria in the form of "tolerable probabilities of failure" are suggested for four of these five categories of pillar. The fifth category of pillar has no reliable support function to perform and support must be obtained by other means.

Jan 1, 1983

By Brett Campbell

The San Vicente to 2nd Aqueduct Pipeline?Tunnel project is a raw water conveyance tunnel linking the San Vicente Reservoir (SVR) to the 2nd Aqueduct Pipeline via Rancho Penasquitos Pressure Control Facility (RPPCF). This 58,230 lf long tunnel will be 8.5? final ID, and has four points of construction access. The job is classified into 6 Reaches of tunnel, identified by the dominant geology within the reach. This paper will focus on Reach 3, specifically the measures necessary to drill and blast a 550 lineal foot section of granitic rock tunnel immediately in front of an open face digger shield.

Jan 1, 2008

By Nicola Beltrandi, Andrea Pigorini, Holad Mohamed Dahir, Ezio Pedone

"Genoa is a very distinctive city located between mountains and the sea and infrastructural upgrading works often have to deal with the intersection of existing infrastructures. This is the case for the new railway tunnel construction between the stations of Brignole and Principe which under-cross two existing double-track tunnels in operation. The latter have been constructed with masonry bricks and the vertical distance between old and new tunnels is approximately 1m. Due to rock characteristics and the urban environment, stability and vibrations control are the main issues. Consolidation work with the fore-poling method and a specific sequence of excavation, primary lining and final lining support have been designed to assure stability and settlement control. A hard rock road-header has been used to assure vibration control. Finally, a real time monitoring has been implemented. The article presents monitoring and back-analysis results of the under-crossing of the existing tunnels. GENERAL LAYOUT OF WORKS The Genoa railway junction constitutes an integral part of the Ventimiglia-Genoa-Novara-Milan railway line route and it is included amongst the railway systems of the Tyrrhenian-Northern European multi-modal corridor (corridor of the two seas or corridor VII Genoa-Rotterdam). The main aims of the project concern the upgrading of the existing lines and the separation of the long-distance passenger and freight traffic flows from those of a regional and metropolitan type. The project includes: •,Completion of the connection with the port of Genoa Voltri and the Italy-France coastal route. •,Interconnection with the future Terzo Valico dei Giovi mountain pass route towards Milan. •,Upgrading of the Genoa Voltri – Genoa Brignole main line to four/six tracks. Rearrangement of the systems at the Genoa Voltri, Genoa Sampierdarena and Genoa Brignole Stations, reorganisation of the services in the Genoa Terralba area and interchangeability with the metropolitan system complete the design activities. The contract which includes civil and technology works is divided into four construction lots (ref. Figure 1):"

Jan 1, 2016

By R. L. Eadie, J. L. Luo

The effect of plastic deformation on near-neutral pH stress corrosion cracking (SCC) also known as environmentally assisted cracking was studied by cracking rate measurements. All the tests were conducted in a synthetic near-neutral pH solution. The traditional potential drop tests using compact toughness (C-T) specimens with 2-3 mm long pre-cracks showed varying plastic deformation by rolling would increase the material's susceptibility to SCC. This was confirmed by cyclic loading tests using double notched flat tensile specimens with 200-300 µm long pre-cracks which gave the same results that the specimen with large scale plastic deformation by tensile loading had a relatively faster crack growth rate than that with only small scale plastic deformation.

Jan 1, 2005

Same-batch and non-blind as well as blind pulp duplicates are often submitted as quality assurance/quality control (QA/QC) control samples to a routine laboratory along with routine assays (and other control samples such as reference material samples). The current ways of interpreting the results of duplicate assays to derive QA/QC conclusions and decisions, however, has not yet been formalised in a scientific manner. The current, prevailing approach and its limitations are reviewed and a new method is proposed as a substitute tool. This new tool should allow for operational error detection on a batch per batch basis (ie batch rejection) as well as laboratory performance assessment with time on reproducibility.

Jan 1, 2008

By Stephen Pogorski, Colin R. Phillips, Atika Khan

An optimized counting scheme for a mixture of radon daughters and thoron daughters typical of Ontario mines, developed in a previous study, was experimentally examined under mine conditions. The counting scheme requires a 10 minute sample and 5 1/2 hours counting instead of a 60 minute sample and more than 40 hours counting as required by a previous method. Taking into account the uncertainties associated with concentrations, flowrate and radioactive decay, the precision of the counting scheme was analyzed and found to be on average better than the 40 hour method.

Jan 1, 1981

By Roger B. Alke

INTRODUCTION Request to Mine Beneath Bridge The Jakes Run Bridge is a reinforced Portland concrete arch filled bridge located on WV Route 7 near Pentress, WV. The bridge has a span of 22.9 m (meters) and a height of 4 m above normal pool elevation to the underside of the center of the arch (See Fig 1). The bridge is a two lane structure with a width of 6.86 m. The structure is over 50 years old having been built in 1929 and is owned by the Department (WV Department of Highways). [ ]

Jan 1, 1984

By Anderson JDC

Opencast Lignite Mining requires topwall strata of seams to be fully depleted and footwall aquifers sufficiently depressurized. To prevent a spread of the cone of depression into protected wetlands some distance away, alternatives had been investigated such as closing water works, underground slurry wall barriers and recharge by infiltration. As a result of these investigations, the infiltration method has been chosen and in a first phase during the next decade it will utilize as much as 55 x 106 m3/year. Using this approach, the survival of the wet lands is assured.

Jan 1, 1988

IT is necessary that all men who wish to bring things to a certain end should think of the agents needed to attain this. Now whichever one of the above processes you wish to use you must consider the nature of the material and see whether it is disposed to render what you wish to extract. Then you must see whether you have the other agents sufficiently powerful and proportioned to attain this result, for if the things were not in harmony your work would be vain and very laborious. Therefore, if you should wish to make waters or oils by way of distilla-

Jan 1, 1942

By J. A. Wates

Stope backfilling in South African gold mines uses the coarser cyclone fraction of the gold tailings. The disposal of the overflow from the cyclones, which is finer and of higher moisture content than normal gold tailings, presents some problems. This paper describes an investigation undertaken to define the parameters that are required for a quantitative and qualitative assessment of the operation and stability of slimes dams built of such material. However, seeing the investigation was conducted on the slimes from only one mine, it is recommended that, until a wider range of data becomes available, tests should be conducted for each individual mine.

Jan 1, 1988

By H. C. Fiedler

It was recently shown with 3.3 pct Si-Fe containing 0.026 pct S and 0.06 pct Mn that the extent of secondary recrystallization to a cube-on-edge texture is determined by the cooling rate from the solution temperature of the manganese sulfide inclusions.1 With a rapid cooling rate, many small inclusions rather than a few large ones are formed, which leads to increased restraint to normal grain growth and more complete secondary recrystalliza-tion. Strip samples 12 mils thick, rolled from 1-in.-thick slabs that were cooled at 130°C per min

Jan 1, 1964

By Robert G. Bottge, Paul C. Hyndman, Don J. Barnes, Clark A. Roberts

The effect of Federal restrictions on Federal mineral estate in Alaska and the Western States is being addressed by systematic, State-by- State studies. The Bureau of Mines has inventoried and classified 3.5 million sq km (876 million acres) of land, section-by-section, according to 1) mineral ownership, 2) availability for mineral exploration and development as affected by Federal restrictions, and 31, areas containing mines and mineral resources. The availability of Federal land for exploration and development is spatially compared to areas containing mines and mineral resources. The methodology and overall results of the studies are presented.

Jan 1, 1991

By S. Pignolet-Brandom, E. Fregeau-Wu, I. Iwasaki

To recycle steelmaking slags for their iron, manganese and lime contents, removal of the phosphorus-bearing dicalcium silicate and calcium phosphate is essential. Slow-cooling of slags was necessary to promote sufficient grain growth to achieve liberation. In situ grain size distribution determination showed that a high soaking temperature, a long soaking time, a very slow cooling rate and the addition of fluorspar promoted grain growth. High gradient magnetic separation on slow-cooled slags removed much of the dicalcium silicate. Liberation modeling was used to discuss the breakage and beneficiation characteristics of the slow-cooled slags.

Jan 1, 1993

By D. E. Ranta, Leigh A. Readdy

Defining classes of ore using geostatistical methods that match historical classifications has presented problems in the past. A simplistic and practical approach to this problem is presented. An example of the approach is presented using a porphyry-type system as a case study. The technique described uses area of drill-hole influence and known conditions from similar deposits, or the production history of the deposit being studied. It provides a practical bridging mechanism for defining the class of ore on a block-by-block basis using the error of estimation value developed during kriging. The approach provides a filtering method that refocuses attention on the adequacy of drill-hole spacing.

Jan 1, 1992

By Zhucheng Huang, Ronghai ZHONG, Liangming Wen, Tao Jiang

The reduction roasting-magnetic separation and its strengthening of high silicon coal-containing mini-pellets by sodium additives were researched. The results show that the carbon gasification reaction and reduction of fine hematite in high silicon coal-containing mini-pellets with 3% sodium additives were enhanced. Comparing with no sodium additives, the gasification rate of carbon with 3% sodium additives reacting with CO2 for 40 minutes at 950 and the metallization rate of reduced pellets with 3% sodium additives after roasting for 35 minutes at 960 increased from 35.15% and 58.72% to 86.98% and 86.15%, respectively. The analysis of SEM equipped with EDS demonstrates that the inner pore of reduced pellets with 3% sodium additives was more developed and the iron grains size significantly enlarged, meanwhile, the iron grade of concentrate increased from 60.45% to 80.23% and the iron recovery rate decreased from 84.67% to 80.78% after grinding-magnetic separation.

Jan 1, 2016

By MATTHEW HART, THOMAS BAMFORD, Kamran Esmaeili, MICHAL KOWALCZYK, FILIP MEDINAC

Improved haul-road conditions can have a positive impact on mine operations, resulting in heightened safety, productivity gains, longer tire life and lower maintenance costs. For these reasons, a monitoring program is required to ensure the operational efficiency of the haul roads. Currently, at Bald Mountain Mine, monthly site severity studies, ad hoc inspections by frontline supervisors or operator feedback reporting are used to assess road conditions. These methods are subjective and provide low temporal resolution data. This case study presents novel unmanned aerial vehicle (UAV) technologies, applied on a critical section of haul road at Bald Mountain, to showcase the potential for monitoring haul roads. The results show that orthophotos and digital elevation models can be used to assess the road smoothness condition and to check the road design compliance. Moreover, the aerial mapping allows detection of surface water, rock spillage and potholes on the road that can be quickly repaired/removed by the dedicated road maintenance team.