Search Documents

By C. C. Pretorius

3D seismic surveys have become a well-accepted method of imaging sub-surface geology in the Bushveld Basin. Because both the seismic sources and receivers are placed at surface, most surveys are limited to imaging faults with >=7 m throw. However, some areas such as shaft infrastructure can benefit from the ability to detect smaller structures prior to shaft sinking. Borehole radar and logs such as the acoustic televiewer can identify these structures in the shaft barrel, but not within -200 m from the shaft. Therefore, Anglo Platinum has developed the method of high-resolution 3D vertical seismic profiles (VSPs) for structural sterilization of shaft sites prior to shaft sinking. VSPs utilize a surface source and sub-surface receivers deployed down a borehole. This means that seismic energy goes through the near surface only once, and therefore suffers less frequency loss than when both source and receivers are on surface. Furthermore, VSPs can record 3 component (3C) data which comprises P wave, Sh (horizontal) and Sv (vertical) wavemodes. Because S waves travel at about 0.6 of the velocity of a P wave, shorter wavelengths and therefore higher resolutions are possible using S wave data. VSPs were first used in their one dimensional, zero offset, mode to correlate borehole geology with seismic stratigraphy within seismic surveys. This showed that VSPs record -30% higher frequencies than surface seismic surveys. The program then applied two dimensional VSPs to the problem of imaging geological structure close to a borehole. 2D VSPs confirmed that high frequency results could be achieved, and that this enabled a more accurate image of the Merensky Reef than could be achieved by surface seismic data. Finally, the program has achieved the successful recording and processing of 3D VSP data, with both compressional and shear wavemodes giving a high resolution structural result. Although P wave data gives -30% frequency improvement over surface seismic surveys, S wave data can give as much as 80% improvement, further improving the structural image achieved. The high fixed costs of VSP surveys mean that they should ideally be run in multi-client batches, which can reduce the per borehole cost by up to 50%. Their application is anticipated to be on high value capital infrastructure with a geological risk from faults which are not imaged by surface seismics-generally in the sub-7 m range. Keywords VSP, 3D seismic, bushveld, platinum, resolution, imaging, shear waves, shaft sinking.

Jan 1, 2011

By S. Vézina

"Environmental issues have evolved considerably over the last two decades. The main contributing factors, to name a few, have been the changing values of modern societies, the globalization of trade and its linkage to environment, evolution and accessibility of information/ communication technologies, better educated populations, climate change, longrange transport of toxics, and the increasing influence of non-governmental organizations (NGOs) and multistakeholders.As well, environmental management of mining operations had to be realigned in order to meet these new realities and to respond to more elaborated regulations oriented towards sustainability. Environmental management systems (EMS) have been introduced not only to meet the assurance of conformance to regulations but also to prevent pollution and to apply the continuous improvement of mining processes. EMS models have been developed and certification to international standards (e.g. ISO 14 001) is a common practice.Globalization has imposed challenges and additional requirements to environmental management. Developing a mine in emerging countries implies dealing with international agencies, local communities, and a variety of government infrastructures to obtain a “license to operate.” This paper presents the structure of Cambior’s EMS and how it was adapted and implemented in the company’s operations in South America."

Jan 1, 2006

The Golden Cross Mine will be the first underground gold mine in New Zealand to operate since 1952. The development plans, along with the conditions and circumstances presently found in the now ongoing mine development, will be discussed as well as a brief review of planned stoping activity and stoping results to date.

Jan 1, 1991

Background geochemistry of streams in mineralised terranes is affected by (a) natural sulphide oxidation and associated metallic discharges; and (b) previous mining history and associated discharges. Both of these processes elevate background metal concentrations by (i) directly adding dissolved metals to stream water; and (ii) adding sulphide-bearing sediments' to the stream system, to be trapped in old channels and bars for later chemical decomposition in situ or after flood reworking. Definition of downstream geochemical background, involving sediments and low-flow dissolved chemistry prior to mining is prudent, as this will provide a benchmark for any required estimation of new inputs from, for example, accidental tailings discharges. Two high-profile examples from western USA illustrate these points. Summitville mine in southern Colorado is an environmental disaster left when the operating company went bankrupt in 1991. Acid metal-rich discharges are leaving the site into a river system used for agricultural irrigation. However, nearby sub-catchments have substantial naturally occurring acid metal-rich discharges and locally discharge natural sulphide-rich debris flows into the same river. Distinction between natural and anthropogenic pollution in the downstream reaches is difficult. Early mining at Cooke City, Montana (New World District) released large volumes of sulphide-bearing tailings into the river system when a tailings impoundment dam failed. The event was equivalent to a 100-year flood, and tailings were deposited for 30 km downstream. These tailings are currently oxidising, and are being reworked into the modem stream during high flow events, thus perturbing background geochemistry.

Jan 1, 1999

By James J. Meadows, Jason D. Pampena, Emanuele G. Cauda, Lauren G. Chubb

Exposure to respirable crystalline silica (RCS) can cause serious and irreparable negative health effects, including silicosis and lung cancer. Workers in coal mines have the potential of being exposed to RCS found in dust generated by various mining processes. The silica content of respirable dust in one single mine can vary substantially over both time and location. The current monitoring approach for RCS relies on the use of traditional air sampling followed by laboratory analysis. Results generated using this approach are generally not available for several days to several weeks after sampling, and this delay prevents timely and effective intervention if needed. An alternate analytical method is needed to reduce the time required to quantify the RCS exposure of mine workers. The National Institute for Occupational Safety and Health (NIOSH) has developed a new method using commercially available portable infrared spectrometers for measuring RCS at the end of the sampling shift. This paper will describe the application of the new field-based RCS analytical process for coal mines, including the use of the new method with the existing Coal Mine Dust Personal Sampler Unit. In a case study conducted by NIOSH with a coal mine operator in West Virginia, field-based RCS analysis was completed at a mine site to evaluate the new technique. The RCS analysis results obtained by the field-based method in this case study showed sufficiently strong correlation with results obtained by the MSHA standard laboratory analysis method to allow the mine operator to use the field-based method for evaluating process improvements.

By John Yenter

"Unique blasting problems during reconstruction and expansion of 100 year old buildings toaccommodate gambling. Located on steep mountainous terrain and linked by narrowroadways, the towns of Central City and Black Hawk challenged blasters to exceptionalmeasures in order to control over_break, vibration, public exposure and damage to thecharacter of these historic mining towns. Utilities were also upgraded to fit demands of asmuch as 800% volume change in one year."

Jan 1, 1993

By Charles D. Litton

This U.S. Bureau of Mines report describes the results of two large-scale tests conducted to evaluate a prototype nitric oxide (NO)-compensated carbon monoxide (CO) fire sensor, developed by Carnegie Mellon Research Institute (CMRI). In the tests, small coal fires were allowed to develop in the presence of diesel exhaust at relatively low ventilation airflows. These tests compared the response of the CMRI fire sensor with that of other fire sensors, including the Bureau's diesel-discriminating smoke detector. During the tests, CO, NO, and smoke levels were continuously monitored in order to determine the sensor alarm times and gas levels as the fire developed. The data indicated that the NO-compensated CO fire sensor was capable of suppressing the CO produced by a diesel engine and that the sensor responded reliably to the CO produced from the test fires. The tests also showed that the Bureau's diesel-discriminating smoke detector alarmed earlier than the prototype NO-compensated CO fire sensor.

Jan 1, 1993

In a gravity separation device, particle shape, size and density all play a role. The combination of these determines where each individual particle reports to in the viscous fluid, where particle crowding (solids to water ratio) also plays a role. To understand the performance of gravity separation devices in the heavy mineral industry, these particle characteristics need to be measured. There are various challenges in analysing particle density and particle size simultaneously for the purpose of quantifying gravity separator performance, not to mention particle shape. These analytical challenges include the high cost of high-density sink-float fractionation, toxicity of high-density sink-float media, inability of sink-float media to fractionate at densities greater than 4.0 g/cm3, and the time-intensive nature of these fractionations. The use of the detailed particle-by-particle output from Qemscan® particle mineral analyses (PMA) as a fast and cost-effective alternative is evaluated. The size and density outputs from the Qemscan® were employed to characterize the performance of a heavy mineral spiral concentrator as an example. Critical analytical requirements are to be addressed before the Qemscan® output data can be utilized. Keywords Gravity separator, performance, heavy minerals, Qemscan® particle mineral analysis

Jan 1, 2011

By Patrick J. Hannigan

A comparison of 40 statically and dynamically load tested piles was performed to evaluate the variation between testing methods. This evaluation indicated an agreement of 10% to 15% could be obtained when the available static resistance is fully mobilized by both methods and when time dependent capacity changes are minimized. Dynamic pile testing recommendations for minimum induced impact force, ram weight to pile weight ratio, and considerations for time dependent capacity changes are presented.

Jan 1, 1987

By Sabry A. Sabour

Metal price is among the key variables in the open pit optimization and the economic evaluation process. The common approach to handle metal prices in open pit mine planning is to optimize the ultimate pit and the mining schedules using a fixed, flat metal price. In this respect, metal price is assumed to be known with certainty throughout the entire mine life, which in some cases can reach 80 years. Given the volatile nature of metal markets and the metal price cycles, the conventional pit optimization approach may generate sub-optimized mining plans, which results in either extra costs to mining projects or lost revenues, or both. Long-term operational decisions such as future pit expansions, beyond the currently optimized limits, cannot be handled using the pit optimization approach based on flat metal prices. There is a growing interest in the mining industry to model and manage such market uncertainty in the pit optimization as well as the project evaluations in order to maximize the value of mining operations. In this paper, the author will outline a practical approach to optimize the ultimate pit taking into account the volatility and variability of metal markets. The proposed approach uses a combination of the pit optimizer of the commercial MineSight package and a simulation-based economic modeling real options valuation approach employing the least-squares Monte Carlo algorithm. MineSight pit optimizer employs both the floating cone for initial optimization exercise and the standard Lerchs-Grossmann algorithm. In this paper, Lerchs-Grossmann option will be used to generate the pit shells. Real options valuation approach used in this study is based on generating multiple metal price scenarios. Metal price uncertainty is modeled using stochastic metal price models such as the geometric Brownian motion and the mean-reverting process. The mining operational scenarios corresponding to the simulated metal prices are then optimized using the least-square Monte Carlo approach. The objective is to maximize the discounted cash flow value of the project while incorporating the operating flexibility to revise the operating status of the open pit with time as new information becomes available. The focus of this work is on the practicality of the proposed uncertainty-based pit optimization approach and the difference it can make to the technical operational mining decisions. A case study of a hypothetical open pit poly-metallic mine is provided. The deposit contains copper, gold and silver grades. The run of mine ore is sent to the process plant that produces copper concentrate with copper as the main metal and gold and silver as the by-products. Four uncertain variables are considered here include copper, gold, silver prices and foreign exchange rate. Both copper price and exchange rate are modeled using the mean-reverting process while gold and silver prices are modeled using the geometric Brownian motion. The case study is performed using both the conventional flat price pit optimization approach and the proposed uncertainty-based one to compare results.

Aug 1, 2013

By G. L. Oldright

The first Report of Investigations of the present series (No. 4562) was on the fundamental properties of lead compounds, and the manner in which they set limits to the richness of lead products treated in the usual sintering-blast furnace units. These properties of the compounds were emphasized, as' it was desired, also, to learn the limitations of smelting the same compounds in present ore hearth practice; the hearth has a competitor in these "usual" units, even with the rich lead feeds best adapted for the hearths. Operating conditions that were followed in older metallurgical processes, when rich products, were treated, were outlined. The second report of the series (R. I. 4563) was on the development of the ore hearths of the types now used in the Tri-State from the viewpoint of the features, functions, and dimensions of the earlier hearths that had been most changed. Experimental data, for both well and poorly desulfurized charges being considered, were given to show the relative changes in the sizes and compositions of the charges after they were added to the ore (Scotch) hearths. A general picture was given of the charge column and of the conditions prevailing there when the operation was satisfactory. In this third paper, the composition of the gases prevailing in the charge column at various elevations will be correlated with what has been learned of the nature of the charge column in order to trace the steps of operation by which lead sulfide is converted into metallic lead. The metallurgical factors that govern operation and the lines along which improvements may be made will be noted.

Jan 1, 1949

By L. M. Lenahan, J. D. Sheets

INTRODUCTION The Raleigh-Durham International Airport (RDU) in North Carolina is the fourth largest airport in the southeast region of the United States. The Raleigh-Durham Airport Authority is currently underway with planning, designing and constructing are placement Passenger Terminal as part of the Major Capital Improvements Program at Raleigh Durham International Airport. The Terminal C Expansion and Renovation Project will replace the existing Terminal C structure with a new processor building and concourse. The project is separated into several contracts. The early stage contracts are constructing a west side storm water management facility, relocating taxiways, installing new drainage systems, installing new aircraft apron pavement, Demolition, the Central Energy Plant and Early Foundations. The later projects are the Terminal Building, Passenger Boarding Bridges, Information Technology Systems and Integration, Furniture, Furnishings & Equipment and Specialty Millwork. The Terminal Building will be constructed in two phases. Phase 1 constructs the north half of the new terminal. Airline operations will move to the new terminal at the completion of this phase. Phase 2 completes construction of the south processor building. The full build out of the project, subject to funding availability, will replace the remainder of the south concourse. The Program’s primary focus is to replace the existing passenger Terminal C with a new terminal that will provide more passenger gates and larger passenger screening, ticketing and baggage handling facilities. The planning for the New Terminal C Program began in 2002 with construction starting in March, 2003. The continuing growth of passenger airline travel in the Raleigh/Durham metropolitan area requires RDU to expand its facilities to keep up with the present and future growth within the Region. In October of 2002, the RDU Airport Authority selected Parsons Transportation Group as the Program Manager/Construction Manager to help assist in the development of the Terminal C expansion program. RDU Airport Authority selected the Seattle Washington Office of URS Corporation as the Engineer of Record for the West Side Storm Water Management Facilities. The Westside Storm Water Management Facilities Project became one of the early critical path activities of the overall RDUAA Terminal C Expansion Program. The Briar Creek Reservoir had been constructed to accommodate storm water runoff to the west of the Airport. The existing 1.5 m culvert that drained runoff from the airport terminal (area) to the reservoir was insufficient in supporting the additional flows

Jan 1, 2005

By George Koenig

I have been granted the outstanding privilege... and pleasure to introduce you this evening to the Grand-Duchy of Luxembourg and to tell you in a few words how this country came into existence, how it managed to survive and what role it nowadays plays in the International Community. Luxembourg, situated between Belgium, Germany and Prance is a small, a very small country... just a dot on a map. After all, it is only a matter of 62 miles from top to bottom and 37 miles across at it's widest... barely covering some thousand square miles... so be careful about stepping on the accelerator... you might be in and out without having realized it... which would be a real shame as the Grand-Duchy enjoys a fairly unique geographical feature in so far as it provides the visitor with an outstanding variety of scenery concentrated in a minute spot.

Jan 1, 1987

By Rick J. Chalaturnyk

In Alberta, oil sands bitumen is utilized for synthetic crude oil production by surface mining, bitumen extraction followed by primary (coking) and secondary (catalytic hydrotreating) upgrading processes, or by catalytic hydrocracking and hydrotreating replacing the primary and secondary upgrading processes. Oil sands tailings, composed of water, sands, silt, clay and residual bitumen, is produced as a byproduct of the bitumen extraction process. Several processes have been proposed for the treatment of oil sands tailings, resulting in different recovered water characteristics, consolidation rates and consolidated solid characteristics, which may have effects on the performance of the overall plant operations. A process for the same purpose has been developed by treating the oil sands tailings with CaO lime and CO2 and thickening it using a suitable thickener. In this process a release water of acceptable properties is recovered in a short retention time, which makes it possible to recycle the recovered water, probably after a reconditioning treatment, as warm as possible to improve the thermal efficiency of the extraction process. The paper presents the theory and laboratory results for the CaO and CO2 thickening of low temperature flotation tailings. The water release rates, segregation potential of the thickened underflow and chemistry of the release water are shown and discussed. It is suggested that in using the proposed process, the thickened tailings underflow can be disposed for further consolidation, or combined with the coarse tailings to produce Blended Composite Tailings, corresponding to the Composite Tailings process in the existing hot water extraction plants.

May 1, 2002

By W. L. Falke

The Bureau of Mines has developed a system that permits the "soft" soldering of aluminum and aluminum alloys with standard tin-lead solders. The method employs application of a thin nickel-copper-alloy coating to the substrate, which enables the tin-lead solders to wet readily and spread over the areas to be joined. With conventional technology, aluminum and aluminum alloys are extremely difficult to solder because tenacious surface oxide films prevent wetting. With the Bureau-developed method, the aluminum substrate is mechanically or chemically cleaned to facilitate bonding to a minute layer of zinc that is subsequently applied with an electroless zincate solution. The nickel-copper-alloy (30 to 70 pct Ni) coating is then applied electrolytically over the zinc, using immersion cell or brush-coating techniques. Development of acetate electrolytes has permitted deposition of the proper alloy coatings. The coated areas can then be readily joined with conventional tin-lead solders and fluxes. The joints so formed are ductile, strong, and relatively corrosion resistant, and exhibit strengths equivalent to those formed on copper and brass when the same solders and fluxes are used. The method has also been employed to soft-solder magnesium alloys.

Jan 1, 1983

By R. L. Caldwell, E. E. Glenn, L. J. Norton, A. J. D. Straus, S. V. Holcomb, J. Zemanek

A new and unique logging tool, called the Borehole Televiewer (BHTV), has been developed to inspect boreholes and to evaluate formations. Even though geologists and engineers have had only about 3 years' experience with the BHTV, the thinking of many of them has been radically influenced by the fascinating and revealing "log-picture" recorded with the tool. The BHTV fills a need for a logging tool that can produce a direct and descriptive record of the physical properties of the borehole environment. Although primarily developed to evaluate fractured reservoirs, the BHTV has been used successfully to solve a variety of problems related to formation evaluation and borehole inspection. Geologists and petroleum engineers have been confounded for many years by the problems of locating and evaluating fractures. Interpretation of the usual resistivity, acoustic or radioactivity logs, as well as the analysis of cores, for evaluation of fractured reservoirs is extremely difficult and often not definitive. This is understandable since analysis of cores from fractured formations has reported variously: (a) low porosity, (b) no effective permeability, (c) lack of any matrix oil saturation and (d) oil stains on fracture planes as the only indications of potential production.14 In recent years acoustic amplitude logs have been introduced and used with varying degrees of success to locate fractures.8'9'11"13 Conventional amplitude logs at best give only qualitative answers where quantitative ones are desired. The logs reveal nothing of the orientation of the fractures. In addition to these logs, various types of cameras, television, and rubber impression packers have been used for borehole inspection. (See Appendix.) The BHTV logging tool supplies both the quantitative and the orientation answers about fractures. The borehole can be filled with any homogeneous, gas-free liquid such as fresh water, saturated brine, crude oil or drilling muds. This tool takes an "acoustic picture" of the borehole wall. The resulting log is a representation of the borehole wall as if it were split vertically and laid flat. The log is oriented with respect to magnetic north. Any physical changes in the borehole wall are seen as changes in picture intensity. In this way, fractures, deformation or pits are reflected on the log. Tool Description The fundamental parts of the BHTV are shown in Fig. 1. A piezoelectric transducer probes the borehole wall with bursts of acoustic energy. A flux-gate magnetometer senses the earth's magnetic field and provides the means for determining the orientation of the log. A motor rotates the transducer and mag-

Jan 1, 1970

By Charlie Vaught, Bill Wiehagen, Lynn Rethi, Pamela Kidd, Lisa Steiner, Ted Scharf, Henry Cole, Kathleen Kowalski

The most hazardous work environments share one feature in common: constant change. Many different, but constantly changing hazards are found in agriculture, construction, mining, and transport. This dynamic feature of work-place hazards varies by: (1) degree of control, (2) predictability, (3) visibility, (4) movement, and (5) degree of speed and force. In some cases the actions of the dynamic hazards are required for production to take place, and in many cases,

By R. F. Favreau, P. Favreau

Rock excavation is the first process in the cycle of operation of a mine, and efficient blasting is paramount to the profitability of the mine. The traditional way to design blasts has been by trial and error, based on the experience of the designer. This is probably the only important engineering practice which continues to be done without a precise engineering technique. The efficiency of most other mine processes has been improved by the use of high-tech, while a majority of blast design has not yet profited from the advantages of the computer. However, with the advent of the high-tech blast simulator Blaspa, it has become possible to design the parameters of the blast according to normal engineering practices. Over the last 50 years, the chemical and physical mechanisms which occur during a blast have come to be identified; they are reviewed in section B. Although these mechanisms are complex, they have nevertheless been expressed in terms of mathematical equations which have been assembled together in the computer to create the blast model Blaspa.

Jan 1, 2002

By D. Lusinga

Hydrocyclones are a common feature in almost all mining operations in the world, serving mainly as classifiers. Some of their advantages include low capital costs, low space requirements and their ability to reduce residence time in closed circuit grinding processes. Although an extensive body of literature exists for hydrocyclones, these devices are still inherently inefficient, and more research is currently being undertaken, particularly in the field of modelling. In the vast body of hydrocyclone literature published so far, there has been little or no effort devoted to analysing the effect of the cone force ratio on the performance of hydrocyclones. The cone force ratio is defined as the ratio of the spigot to the vortex finder diameter (Shah, 2005). In this study a total of 44 tests was carried out in a custom-built rig at the University of Cape Town. These tests were aimed at evaluating the effect of the cone force ratio on the performance of as mall diameter hydrocyclone. The cut size and water split were used as the criterion for evaluating the performance of the hydrocyclone. Results from the tests showed that the cut size decreased with an increase in the cone force ratio. The cut size also appeared to decrease as the calculated locus of zero vertical velocity (LZVV) shifted inwards. The water recovery to the underflow appeared to increase with an increase in the cone force ratio. The effect on the cut size of adjusting the cone force ratio was found to be higher for a coarser feed than it was for a finer feed.

Jan 1, 2009

The importance of understanding the behaviour of cemented paste backfill (CPB) within the framework of the effective stress concept is highlighted in this paper. Only through an understanding built on this concept can problems such as barricade loads, the rate of consolidation and arching, be fully understood. The critical importance of the development of stiffness during the hydration process, and its impact on factors such as barricade loads, is used to illustrate why conventional approaches that implicitly ignore the effective stress principle are incapable of capturing the essential components of CPB behaviour.

May 1, 2007