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By A. E. Raddatz

In an attempt to develop technology to use domestic resources in place of imported bauxita, the Bureau of Mines investigated sulfurous acid leaching to extract alumina from kaolin. The process consists of leaching the calcined kaolin with a 30 wt-pct S02 solution at 60° C and 160 psig for 17 hours, fil¬tering the leach slurry, precipitating monobasic aluminum sulfite from the filtrate at 110° C and 60 psig, a& decomposing the sulfite in the spent liq¬uor at 150° C and 55 psig to produce crude alumina. Purification of the crude alumina was accomplished using a modified Bayer process. Results from closed-circuit tests employing the sulfurous acid process showed that overall extraction of alumina from kaolin was 67 pct. Production of 1 ton of alumina would require 3.6 tons of calcined kaolin, 0.7 ton of sul¬fur dioxide, and 8.4 tons of water. After purification by a modified Bayer process, the alumina product contained the following; impurities, expressed in weight-percent: Fa203, 0.009; S, 3.6; Si02, 0.07; Ti02, 0.002; K20, 0.017; and P205, 0.03.

Jan 1, 1981

By J. K. Lemley

The human element in large measure dictates success in contracting relationships. Because of our professional backgrounds, we view contracts primarily as either engineers, contractors or owners. A beneficial contractual environment--one in which decisions, risks and benefits are shared--demands equal consideration of all three points of view. Most of the older cities in the United States, for example, suffer from bad contracts--generalized, patched-together documents that represent an accumulation of modifications originally written to compensate for specific situations that have occurred over the years. Because such documents lack coherence, they often present conflicting instructions which lead to defensive, ultimately destructive attitudes among the parties involved in the day-to-day administration of the project. Good contract development begins with a strong central philosophy to which the details of the contract can be related. First, the owner should establish a comprehensive philosophy in which risks between the parties are identified. Following this, a specific contract document can be written to satisfy this established philosophy. The contrast between two opposed contractual situations, NYC Water Tunnel Number Three and the Seabrook Nuclear Power Plant Cooling Water Tunnels, illustrates how comprehensive, well-written contracts--contracts which share both risks and benefits--provide the basis for achieving quality construction that will reward engineer, contractor and owner.

Jan 1, 1983

In this paper, the authors attempt to apply a simplified non-homogeneous void diffusion model (NHVDM) to predict surface subsidence for longwall mining in Illinois. A generalized error function subsidence profile is derived from this model. The model validation indicates that the NHVDM approach appears to fit the observed subsidence data as well or better than the error and the trigonometric functions, particularly around the trough edge areas.

Jan 1, 1990

By E. D. Fox

Introduction The financial statement of the hypothetical Gold Mining Company, which forms the background of this survey, was designed for the Institute with the express abject of having it assessed in respect to Profits by the several taxing bodies representing the Federal and Provincial Governments, which comprise the Dominion of Canada. On the completion of the figures, copies were sent to the several Ministers of Mines, accompanied by a request that they be submitted to their taxing authorities and assessed accordingly. The response, while it was not general, was very favourable, and at all times we were treated with the utmost courtesy and patience, and what has been set forth in the compilation bears the authentication of the various government officials who are immediately concerned with taxation. The data itself constitutes a fairly comprehensive digest of taxation as it directly applies to gold mining profits in Canada. The Hypothetical Balance-Sheet (See Exhibit A) In the balance-sheet schedules 1 and 2 (Exhibit A), income is divided between taxable and non-taxable classifications, and here it should be noted that the division contemplates only the assessment for Dominion income tax. The same applies to the factors of exchange and depletion. Therefore, in making comparisons, it is to be borne in mind that the set-up for assessment to the Provinces, that is, Manitoba and Alberta, will stand as if the gross non-operating income is taxable, with the reservations as shown in the notes below the schedules.

Jan 1, 1934

By Neil Westoll

But First, An Overview of the Selwyn Basin and Its Resources ?World-renowned sedimentary-exhalative (SEDEX) deposits of zinc, lead, silver +/-barite ?Significant reserves/resources remain and vast tracts of prospective stratigraphyremain under-explored and untested. ?More details are at the Yukon Geological Survey?s Selwyn Basin Metallogenysite:http://www.geology.gov.yk.ca/metallogeny/selwyn/ Overview of Metal Price and Demand Trends ?The pace of economic change in China has been extremely rapid since the start of economic reforms just over 25 years ago. According to official statistics, economic growth has averaged 9.5% over the past two decades and seems likely to continue at that pace for some time. National income has been doubling every eight years. Such an increase in output represents one of the most sustained and rapid economic transformations seen in the world economy in the past 50 years.? Organization for Economic Co-operation and Development 16-Dec-2005

May 1, 2006

By E. D. Palmes

A new type of personal sampler for quantitative estimation of atmospheric concentrations of contaminant gases was first reported from this laboratory in 1972. The sampler requires no pumps or flow regulators and employs instead the motion of the gas molecules them-selves to furnish the power for sampling. Under this grant, work was completed on development of a kit for the field determination of both NO2 and NO. Detailed instructions for the preparation of the samplers and the use of the kit was supplied to the Technical Project Officer. Attempts were made to adapt the same type of sampler to the measurement of SO2 and CO. Both gas chromatographic and turbidimetric procedures for the final estimation of the S02 proved to be unsatisfactory. For CO no reagent was found which would react sufficiently rapidly with this gas to utilize the essential feature of the diffusion sampler, the maintenance of a diffusion gradient which is at least approximately numerically equal to the ambient concentration. A number of publications on use of the NO2 sampler, both at occupational and community air pollution levels, have resulted from this work.

Jan 1, 1979

By William Brundan

INTRODUCTION The Srisailam Left Bank Canal (SLBC) Tunnel Scheme is part of the Alimineti Madhava Reddy Project in Andhra Pradesh, South India. This scheme has been planned since 1983 and will provide irrigation facilities to drought-ridden areas in Andhra Pradesh. Water will be transferred from the Srisailam Reservoir during the monsoon months to 0.3 million acres of farmland and will also provide drinking water to villages en-route. The paper will address the design and onsite assembly of the Robbins Double Shield TBMs for Tunnel-1 of the SLBC tunnel scheme from planning to start-up of the machines. Also, it will provide a current status of the project and describe the advantages of a site assembly. Problems encountered to date and the solutions adopted will also be described. The project comprises over 50 km of tunnels and involves construction of the world?s longest tunnel without intermediate access. The TBM tunnels at 43.9 km in length and 10.0 m diameter will cross the Amrabad plateau, containing a wild life sanctuary and India?s largest tiger reserve, the Rajiv Gandhi. Jaiprakash elected to excavate the tunnel using two tunnel boring machines, rather than by drill and blast, in order to alleviate surface disturbances to environment and the tiger reserve, wild life sanctuary, and protected forestry areas. The Project was awarded to the Main Contractor Jaiprakash Associates Ltd with The Robbins Company as the Tunnel Boring Machine (TBM) supplier in August 2005. The Robbins Company supplied the TBMs along with two continuous conveyor systems and all spares and consumables to complete the tunnel excavation.

By X. Louw

"This paper examines the change in surface properties of the Polyurea used on spirals at different operational times: unused spiral, 28 months in operation and 58 months in operation. This is being done to investigate the alleged statement that spirals have a decrease in spiral separation efficiency after a certain period of operational time. Observing the surface characteristics under 1.5x and 36x magnification it can be concluded that the surface roughness decreases with increased operational time. This may be explained by a decrease in air inclusions and streak lines as the spiral surface wears. Decreased surface roughness should in theory have a beneficial effect on spiral separation performance. This leads to the conclusion that if a decrease in spiral separation performance is observed after a certain period of operation, it can’t be attributed to the change in surface properties. Uneven wear of the spiral surface, material creep or application of force to the spiral will change the profile of the spiral and could cause an adverse effect on spiral separation performance. The metallurgical test work showed that the best results are obtained at 30 - 35% solids by mass in the spiral feed. The iron recovery was significantly higher in the new spiral in comparison to the 2012 and 2010 spirals. The mass yield to concentrate in the new spiral was approximately three times more than for the older spirals. In conclusion, the yield combined with the grade, which equals the recovery was the best for the new spiral.IntroductionAn investigation was launched to research the common belief that spirals experience a decrease in efficiency, and therefore recovery, after a certain period of operation (a period of seven years has been used in the industry). The properties of the spiral that may have an effect on the efficiency are:"

Jan 1, 2017

By Rob D. Morrision, Paul W. Cleary

"The best accepted method for design of autogenous and semi-autogenous mills is to carry out pilot scale test work using a 1.8 m diameter by 0.6 m long pilot scale test mill. The load in such a mill typically contains 250,000-450,000 particles larger than 6 mm, allowing correct representation of more than 90% of the charge. This scale of DEM model is now within the practical range of standard workstations running an efficient DEM code.This paper describes various ways of extracting collision data from the DEM model and translating it into breakage and wear estimates. Account is taken of the different breakage mechanisms (impact and abrasion) and of the specific impact histories of the particles in order to assess the breakage rates for various size fractions in the mills. These impact histories have the potential to be directly related to breakage as they most resemble the single particle breakage tests which are used by the JKMRC to calibrate more traditional population balance models for variations in ore behaviour. However, the specific impact histories also show a background of many low energy collision events within the mill. This Background may constitute what is usually regarded as “abrasion” breakage. As might be expected, high impact events are concentrated in the toe of the charge and near to the mill shell where the forces associated with the load bearing on each particle is more concentrated."

Jan 1, 2003

The Stawell Goldfield, the westernmost of the main Victorian fields, has produced over a million and a quarter ounces of gold from one and three-quarter million tons of ore. The lodes are quartz reefs and sulphide bodies occurring in sediments of lower Ordovician or upper Cambrian age. The lodes are confined to a relatively narrow suite of weak rocks lying between stronger ones above and below and there is a definite relationship between fold structure, pitch and strength of folding and ore.LOCATION HISTORY AND PAST PRODUCTIONThe town of Stawell, situated 150 miles north-westerly from Melbourne on the main railway and road to Adelaide, is the most westerly of the main gold areas of Victoria. Alluvial gold was found at Pleasant Creek (now Stawell West) in 1853 and the usual "rush" followed. Numerous alluvial leads, some surface, others buried under up to 100 ft. of Tertiary sediments were worked. The alluvial gold was soon exhausted, but in 1857 gold-bearing reefs were found on the slopes of a prominent ridge on the northern edgeof the present town. Early reef mining was by small working parties mining to shallow depths only and treating their ore at public crushing plants. Some of the early returns were very high grade. The next stage was the amalgamation of claims and the formation of companies, with their own treatment plants. This stage continued till the last mine closed in 1921. These companies had, by present standards, small holdings and far too many shafts were sunk, resulting in less efficient prospecting and operation.Since 1921 there have been one or two small scale attempts to revive mining but without success. Of recent years Gold...

Jan 1, 1960

By G. H. Lind

New South Wales has a successful history of pillar extraction stretching back more than 60 years. Various methods of pillar extraction ranging from the rib pillar methods (such as the Wongawilli system) to the more recent pillar stripping techniques (similar to those used in the USA) are discussed in this paper. These discussions are based on the experiences of the author stemming from a recent research tour of seven underground pillar extraction operations in New South Wales as part of the Coaltech 2020 collaborative research initiative. Some operational issues of each site visited are presented before some general comments pertaining to the overall success of pillar extraction in New South Wales are discussed. Generally pillar extraction in New South Wales is on the decline in favour of longwalling. However, the pillar extraction that is conducted is done so along specific guidelines to ensure their success, and these are also discussed.

Jan 1, 2002

By H. C. Fowler, G. B. Shea

MODERN industry's incessant demands for increased operating efficiency and lower costs require that hazards attending all occupations be reduced to a minimum. Reduction of the inevitable losses that result from accidents and injury to the worker is one of the important economic problems confronting industry today and is the basis for the widespread safety movement. Dr. Charles E. Munroe, chief explosive chemist of the U. S. Bureau of Mines, is father of the statement, "The existence of a nuisance is evidence of an economic waste." This pointed expression of the internationally recognized scholar and explosives engineer has a direct relation to the prevention of accidents. Every injury and death in industry is a waste in human endeavor and a lessening of productive gain. Dr. Munroe has aptly paraphrased his previous summation with reference to wastes as follows: "A lost-time accident is evidence of an economic waste." That the economic waste entailed by occupational accidents is chargeable to industry is well substantiated by the fact that all but four states (Mississippi, South Carolina, Florida and Arkansas) now have workingmen's liability and compensation laws.

Jan 1, 1933

By F. J. Tavera, J. A. Finch

A probe suitable for on-line measurements of gas hold-up in industrial flotation systems has been developed. It is based on an open cell for measurement of slurry-gas conductivity and a novel syphon cell for measurement of slurry-only conductivity. The desired behaviour of the two cells was demonstrated and estimates of gas hold-up were shown to be in good agreement with independent measurements. The gas hold-up probe was used as a diagnostic tool to assess the operation of flotation columns. Differences in gas hold-up between baffled sections in two industrial columns were detected

Jun 18, 1905

By B Moynihan

The Roa Opencast Coal Mine is situated at the north-eastern end of the Greymouth Coalfield. It lies on an eastern flank of the Paparoa Range, 16 km north-east of the town of Greymouth on the West Coast of the South Island. Road access is via a sealed road from Blackball to Roa, then by a 5.3 km all weather, gravel road, which gains 340 m in elevation from 190 m RL at Roa to a maximum height of 530 m near the opencast.

Jan 1, 1993

By B. Samoski

In late 1994, EPA and OSM acknowledged that efforts by any one agency or by the many different agencies to remedy the water quality impacts of decades of contamination from abandoned coal mine lands in Appalachia would not be successful if their disjointed efforts were not unified and if the local watershed organizations were not included. The result of the collaboration between EPA and OSM was the creation of a statement of mutual intent which was a pledge by government agencies, watershed organizations, and the industry to restore watersheds degraded by acid mine drainage from abandoned coal. The presenter will describe the evolution of this pledge from a paper promise to on-the-ground remediation projects.

Jan 1, 2002

By W. H. Young

The thickness of the coal seam is one of the more important items influencing the productivity and general overall efficiency of operation of a coal mine. The average thickness of coal seams mined in the United States has changed very little in the past 40 years. The first measurement of thickness of bituminous coal and lignite seams was made for 1920, when the average thickness was 5.3 feet.4/ The average thickness for later years was as follows: 1945, 5.4 feet; 1950, 5.3 feet; 1955, 5.2 feet; and 1960, 5.5 feet.5/ Table 1 includes data on number and production of bituminous coal and lignite mines classified by I-foot intervals of seam thickness mined in 1920, 1945, 1950, 1955, and 1960. Though bituminous coal and lignite are mined today from seams of exceedingly variable thickness -less than 2 feet to more than 50 feet - a large majority of the production, 62 percent in 1960, came from seams 3 to 6 feet thick. This is not surprising since the coal seam of moderate thickness presents the least mining difficulties.

Jan 1, 1962

By Reeves M

A review of the literature available in English on kriging and geostatistics is given with the references cross-classified by their subject matter for convenience and ease of use.

Jan 1, 1979

By Normal Seidle

This report (rind related Appendices) provides a description of the functional design specifications and related rationale for development of a training system for dragline equipment operators. Phase I activities involved a delineation and detailed analysis of specific behavioral requirements for successful dragline operation. Following the field data collection effort, job/activity/task descriptions were formulated into training requirements which can be achieved by a trainee with training hardware having specific functional capabilities. The training system analysis integrated the training requirements and the trainer functional capabilities into recommendations which configure a total training system. The objective of the training system described in this report is to provide new operators of dragline equipment with the requisite skills and knowledge to assure cost-effective development and an adequate supply of our human resources.

Jan 1, 1975

By Irwan S. Halim

For tunnels in horizontally bedded rock, geologic factors affect the selection and design of the initial supports, including the rock propensity toward parting along bedding and the resulting high potential for rock slabbing during excavation. To evaluate this ground behavior, numerical analyses and results with Mohr-Coulomb, Hoek-Brown, and Ubiquitous Joint constitutive models were used, using the Upper Rouge CSO tunnel in Detroit, Michigan as an example. The different rock models and other geologic considerations are shown to impact the selection of the tunnel initial support and design. This paper emphasizes the appropriate selection of an analytical model based on the site specific geology to achieve an optimum initial support design.

Jan 1, 2008

By Sanna Mustonen, Seppo Mellanen, Mellanen, Pekka Kantia

In Finland Posiva Oy (Company) is responsible for implementing the final disposal programme for spent nuclear fuel of its owners. Company is preparing for the geological disposal in Olkiluoto crystalline bedrock. Excavation will be executed using drill and blast method. Method unavoidably causes variable excavation damaged zone (EDZ) on tunnel surfaces. The EDZ constitutes a risk for long term safety and therefore good control methodology of the blasting technique is required. The thicker the EDZ, the greater is the likelihood for detrimental transport pathways for ground water to transport radio nuclides, should those be present.

Jan 1, 2016