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By F. N. Kissell, H. K. Sacks

This study examines the accuracy of area sampling for measuring the dust exposure of mining machine operators in coal mines. The specific objective of this research was to find locations where an area sampler might work better than earlier studies have indicated. The results show that fixed-location area sampling cannot accurately predict the dust exposure of a machine operator, even when the best fixed location is sought, the fixed location is quite close to the operator and the bias due to the dust concentration gradient is corrected. Industrial hygienists have known for many years that area sampling is unsuitable for measuring air contaminant exposures in the workplace. Near contaminant sources, the dilution air and the contaminants are not evenly mixed. Therefore, when workers are near contaminant sources, exposure measurements must be taken from the worker's breathing zone to be accurate.

Jan 1, 2003

By John V. Beall

THIS is not simply the story of how a water filled shaft was developed into a million-ton- a-year producing mine in the space of four critical years, although it is reason enough for telling it, but it is also the saga of an engineering achievement in which knowledge nurtured by years of experience in coal and ore mines was blended together and the best from each type of mining selected. The entire system of mining was detailed on maps by the mining engineering department before the shaft was unwatered, and subsequent development followed these plans nearly to perfection. The selection of machinery was particularly critical as it was necessary to push production from only a few headings in the early stages of development and metal mine machinery was being used in a coal panel-system of mining.

Jan 12, 1950

It is a well known fact that the best method of rock reinforcement is to avoid physical ground support. This goal can be achieved by means of: - Increasing the rock structural strength - Geological definition and forecasting. - Sequencing the excavation - Smooth blasting In many cases however, extra ground support is needed in order to maintain safe working conditions. In an open pit, the structural strength of rock cannot be increased by lowering the pit walls due to economical reasons. Economy demands steeper walls and less waste to be hauled to the dump. The geological conditions can also often be extremely poor and unpredictable. For excavation sequencing and smooth blasting there are good possi- bilities, such as cleaning of the pit walls after the main excavation, arul- ing of long small diameter straight inclined holes, use of smooth blasting techniques and lightened explosives.

Jan 1, 1989

In the future to excavate sufficient coal for power generation, two dredgers would be required to dig overburden or interseam 70010 of the time and three dredgers 40010 of the time. One overburden system was not adequate for this requirement, making coal production reliability vulnerable. TS5 spreader is the new machine element of this system. The selection of the best type of machine configuration to suit the application was then subject to an internal SECV VE Study, a registration of interest and a tender for two machine alternatives. This paper outlines the reasons why SECV planned the Secondary Overburden System and how the Krupp machine met these requirements. It also identifies the main design features of the machine and its constructability which will allow the machine to be operational by the end of May, 1990.

Jan 1, 1989

By Larry DeGraff

With the increase of new mine development in the past several years, many coal mines have decided to self- perform the design and construction for their slope development projects. The development process of determining the proper configuration is challenging, and a major economical consideration. Greenbrier Smokeless Minerals engineering staff and consultants, along with DSI/American Commercial, developed a support configuration that was best suited for their slope. The developmental process took into consideration the length of slope, depth of slope at the high-wall transition, economics of a single or multiple entries, waterproofing, stresses on the steel supports and lagging during the backfilling operation. This paper describes the developmental concept of using a single entry, side by side configuration, using steel ?Banjo String? supports with steel plank lagging, to develop a long term permanent installation in a cut and cover application.

Jan 1, 2009

By Holger Witthaus

The conditions of great mining depth and multi-seam¬longwalling require a special method of rockbolting, It can be described as a control loop which is based on the elements of planning, drivage and measurement. Different planning elements such as the results of the observation of physical models, numerical programmes for calculation of stress-distribution and support success, lab and underground support testing and the knowledge of strata behaviour underground including geotechnical classification are used to get best results. The increasing geotechnical information collected during drivage of roadways are used to estimate and minimise the risks of support-overload. The repeated plan/acutal comparison during the use of roadway and continuously monitoring of support and roadways provided the opportunity of optimising support design during the process of drivage and if necessary in front and after of the longwall face.

Jan 1, 2000

By Hoppe AJ

Drilling and shooting techniques at Moura open-cut have evolved over a period of 16 years and are the result of hard earned experience combined with established practices and consul- tation with professional services. The wide range of overburden types encoun- ted in the field requires varying methods to achieve the best results at all times. Safe working conditions for the employees and protection of mining equipment is of para- mount importance and close liaison is maintain- ed with the Department of Mines Queensland to keep abreast with changing legislation. Drill patterns, charging profiles, types of explosives and ultimate results are des- cribed in detail along with a resume of equip- ment. Costs of drilling, labour and explosives are also analysed with a total of approximately 20c per cubic metre of shot ground. Future developments and improvements to facilities are also outlined.

Jan 1, 1978

By Chai Li-yuan

The anodic behavior of AZ31 magnesium alloy in NaOH alkaline solution was investigated in this paper. The effects of anodizing parameters, such as applied current density, concentration of NaOH and temperature of the solution on the formation, structure and surface morphology of the anodic films were also studied. The formation of the anodic film was analyzed by analyzing the anodic polarization curves, the potential-time curves and XRD, SEM graphs of samples obtained at different anodizing time. The results of corrosion resistance tests, XRD and SEM observation showed that the temperature greatly affected the formation and anti-corrosion property of the anodic film, but the concentration of NaOH not. The film with best anti-corrosion resistance was obtained at applied current density of 10mA/cm2, 353k in 1mol/l NaOH solution.

Jan 1, 2006

By Peter Griesenbrock

In German underground coal mining mostly arch and some rectangular roadways are used in the development work. Due to its positive results from numerical and physical modeling techniques as well as good underground experiences, the numbers of rectangular roadways has increased significantly. Today the bolt support - independent of its cross-sectional shape - represents an undeniable support element. During the introduction of new bolt techniques a detailed investigation of the rock and support mechanical effectiveness of bolt support in roadways at all operation stages is of basic importance. This effectiveness can be predicted and verified using different simulation techniques. For the planning of rockbolted roadways two supplementary simulation techniques are presented in this paper. By combination of all available planning tools the best result for planning assurance can be achieved. Keywords: numerical modeling, physical modeling, arched roadway, rectangular roadway, roofbolting, advancing longwall.

Jan 1, 2002

Grade control aims to deliver quality tonnes to the mill via accurate definition of ore and waste. It comprises data collection and interpretation; local reserve estimation; supervision of development and mining; and stockpile management. The foundation of all grade control programs should be that of high quality sampling supported by geology. The requirement for quality grade control samples has long been recognised, where they should be representative, unbiased, safe and operationally timely. Underground sampling methods include chip and channel samples; grab samples; and drill-based samples. To achieve quality samples, collection techniques employed should minimise delimitation, extraction and preparation errors. Grade control staff should be well-trained and motivated, and mining staff should understand the need for grade control. This paper reviews grade control sampling methods and presents recommendations for best practice and minimisation of sampling errors.

Mar 1, 2010

By P. Gonzalez

Minera La Parreña, S.A. de C.V., Milpillas operation is an underground mine designed to process 8 352 tons of ore per day for the recovery of copper through crushing, heap leaching, solvent extraction and electrowinning facilities. In order to optimize copper recovery during leaching, the ore is crushed to 13 mm and subjected to primary sampling every 15 minutes for metallurgical accounting. At the same particle size, primary sample goes to secondary sampling and then, the secondary sample is crushed to 2 mm before tertiary sampling. The tertiary sample is sent to laboratory where a final sample is obtained and pulverized to 106 microns for copper assay. This paper shows a review of sampling strategy focused on minimizing or eliminating sampling errors and an experiment designed to determine copper head grade profile as well as the best sampling frequency.

Jan 1, 2009

By John W. Lund

The Geo-Heat Center has been investigating the utilization of waste silica from the Cerro Prieto geothermal field for several years. The main objectives of the research were to com-bine silica with various additives to (1) form bricks for low cost housing, and (2) to produce a suitable road surfacing material. The various additives that were tested included hydrated lime, portland cement, plastic fibers, asphalt cement and emulsified asphalt. The silica-cement combination produced the strongest bricks and had the best weather resistance, whereas, the silica-lime combination produced the bricks with the lowest thermal conductivity and specific gravity density. The addition of plastic fibers to the silica-lime mixture improved both strength and weather resistance. The combination of asphalt and silica is not suitable as a road surfacing material, however, silica-cement appears promising.

Jan 1, 2006

By John Gann

THE following investigation constitutes a brief resume of the more important binary magnesium alloys from the standpoint of metallographic technique, and the effect of heat treatment on structure and properties. The comparative newness of the subject justifies this procedure as a preface to a more detailed study of each individual series of alloys. The work was started with the idea of practical application in the industry rather than as a theoretical investigation. The alloy compositions studied were selected as those most likely to show whether heat treatment would produce beneficial results. Furthermore, it was considered satisfactory to use commercial 99.9 per cent. magnesium, the best commercial grade of alloying ingredients, and to limit the time of heat treatment at the expense of incomplete equilibrium. These facts must be kept in mind when examining the results obtained, and the conclusions drawn.

Jan 1, 1928

By B. Grosso

The National Italian Regulation concerning environment protection imposes that industrial areas are provided with systems aimed at preventing the circulation of contaminated groundwater. These systems can be static or dynamic and operate basically by intercepting the contaminated flow. Their effectiveness, realization time and costs depend on the intervention type and on the features of the specific site. The selection of the best solution is complex and the results obtained by this selection may be affected by residual risks related to the uncertainty of the hydrogeological and geotechnical characterization of the site. With regard to the industrial area of Portovesme, located in the south of Sardinia, the paper presents the analysis of alternative interventions aimed at the protection of the groundwater. The attention is focused on the evaluation of their effectiveness, impact on environment and, finally, time and costs of construction.

Jan 1, 2008

By Wm. H. Woodhead

Improved methods of mining have accompanied the introduction of mechanical loading, of which there are a great many varieties, but this multiplicity of mining brings new problems and greatly increases the importance of managing over a few years ago. Few mines operating today have been opened with the intention of mechanizing throughout. The problem of mechanization is to change over a mine heretofore operated by hand methods and to select machinery that will fit the old system with the least number of changes, the aim being not to disrupt or to completely change the original plan. The organization of mechanical and electrical forces is a problem in mechanical loading, and each individual mine presents its own problems. Plans which may succeed in one mine may fail in another and upon the management rests the responsibility of deciding the best method in each case.

Jan 1, 1930

This paper presents an overview of a program PC-BC developed for application to the design and evaluation of block cave operations. Conventional mine planning software tools are not well suited to the evaluation of this type of deposit. The paper looks at the modelling approach as applied to a block cave mining project. The following steps are described:Initial preparation of data including block models, draw point footprint geometry and draw cone geometry. Computation of individual draw point reserves. Procedure for modelling of vertical mixing of material within each draw point and subsequent determination of the best height of draw for each draw point based upon an economic cut-off value. Smoothing of draw heights amongst neighbouring draw points to produce a realistic draw envelope. Mineable reserves within the envelope are then computed. Tools for preparation and evaluation of various production schedules. This includes definition of draw rates, and rates for commissioning new draw points. In an operating mine, the capture and analysis of daily draw tonnages is important. How PC-BC accommodates this is described as well as the processes for depleting the draw column reserves. In the 12 years since the program was first developed, it has been used on a number of projects for feasibility studies and operating mines. Some practical examples of the use of the program in these projects are presented. Finally, some commentary on the sensitivity of various parameters is presented. Particular emphasis is placed on the overall footprint design.

Jan 1, 2000

By Richard L. Wedertz

Although the physical appearance of excavating equipment doesn't seem to have radically changed over the past decade, important changes within the products and an innovative attitude on the part of the engineer in his design approach is becoming increasingly evident. The new philosophy is to go beyond simple refinements of existing designs that simply produce a machine which further reduces overall cost per ton or per cubic yard of material moved and to do it more efficiently than ever before. Standard ideas and preconceived notions have been discarded and have given way to providing a design and a machine that is best suited to get the job done. Understanding that the application will not always fit the machine, but, in most cases, the machine should fit or suit the application is a foremost consideration in the engineers' design criteria.

Jan 1, 1973

By R. C. Buehl

[Improvements in refractories for high-temperature service have made possible the use of higher temperature in many processes. Consequently, it sometimes is desirable to use gases heated above 1,600° F., and for moderate rates of gas flow, there gases can be heaters best with pebble heaters. Pebble heaters of the stationary-bed type in which the chanber was lined with mullite brick and pebbles of pure alumina served as the heat-exchange medium have been used recently to heat the air blown into an experimental blast furnace4/ These pebble heaters worked well and made it possible to use air temperature up to 2,500° F. at the tuyere of the furnace. Since little has been published on this type of gas heater, a review of the construction on employed and operating data should assist in selecting applications and designing units.]

Jan 1, 1953

By K. Zabrusky

"Wireframe construction is an integral part of resource estimation. Wireframes control domaining of samples and data for geostatistical analysis and grade estimation. They may also provide 3D representations of lithology and grade domains. Thus, the way in which a wireframe is constructed has implications throughout the resource estimation process. Proper construction technique and understanding of wireframing processes should be a high priority in a model workflow. Herein is presented an overview of two main categories of wireframes: implicit and explicit. Construction differences between these two types are highlighted. Factors affecting the choice between the two wireframe types will be discussed, including data quantity, data distribution, and sampling technique. Deposit geometry also plays an important part in wireframe construction. The role of geologic knowledge, cross section orientation, and deposit type in regards to wireframe construction will be discussed. The effect of wireframe type on resource estimation will be examined. Finally, best practices for creating meaningful solids that contribute to a reasonable grade estimation are outlined. INTRODUCTION Wireframes are essential to many types of resource estimations. They provide a way to delineate a deposit into various domains. Domaining can be done by lithologic or geologic units, structures or structural zones, or by grade. Domaining is important for geostatistical analysis and grade estimation of a deposit. The purpose of domaining is to analyze and estimate like data with like. Grade distribution patterns may vary by lithology or by proximity to or existence within structural zones. Properly constructed wireframes are therefore a fundamental necessity to a properly executed geostatistical analysis and resource estimation model. The choices made in construction of wireframes have a trickle-down effect on the entire model and should be made according to best practices for the deposit type at hand.TYPES OF WIREFRAMES Explicit The term “explicit wireframe” is used in this paper to indicate wireframes that are constructed by the modeler. This usually involves the modeler drawing the wireframes “by hand”, e.g. still utilizing some sort of computer aided drawing software, but with the modeler making all decisions about the size, shape, and positon of the wireframe. These wireframes are drawn based on some type of key variable that the modeler determines is important to their system. Often, this key variable may be a lithologic unit that controls mineralization, an observable structural zone, or a grade cutoff. Explicit wireframes are generally constructed as a series of shapes drawn on 2D planes or cross sections that are then connected into a 3D shape. Figure 1 shows an example of an explicit wireframe that was drawn based on a grade cutoff on 2D sections (Figure 1a), then joined into a 3D shape (Figure 1b)."

Jan 1, 2015

By Wayne A. McCurdy

I welcome the opportunity to meet with you and discuss the work and program of the Office of Coal Research. Our programs are oriented to serve the conservation objectives of the Johnson Administration and of the Nation by seeking out the most efficient and best uses for coal. We believe that even if only a portion of our program is successful, the coal industry and the Nation will benefit far out of proportion to our expenditures. Operating with a budget of $7,220,000 in Fiscal Year 1966, OCR sponsors contract research which offers potential for achieving benefits to the coal industry in the form of new production and new markets. This directs us into many areas of research activity: in coal combustion, in advancements in mining methods and coal preparation, in new uses for coal, and in associated economic and marketing research.

Jan 1, 1966