Search Documents

By D. S. Choi, H. von Schonfeldt, H. D. Dahl

The design of pillars around a longwall panel in which the effect of the adjacent and worked-out panel is taken into consideration is discussed. A mathematical model is used to duplicate field observations such as opening closure and pillar rib movement. The model is then used to predict the effect of changes in mining geometry on the opening stability.

Jan 1, 1976

By D. S. Choi

Underground production of coal by longwall methods has increased significantly in the last few years and will very likely continue to: increase. There are several reasons for this. First, as mining moves into seams having greater overburden, roof exposure must be reduced since support will become' increasingly expensive. Secondly, the growing demand for coal has forced the coal industry to seek alternative, more productive, coal mining methods. In addition, the longwall method greatly simplifies the underground ventilation network. This paper addresses itself to the design of longwall development headings, particularly to those of the United States where multiple development headings are required by law. The most burdensome problem encountered in many longwall mining installations is deterioration of the tailgate due to the combined effect from, the active longwall gob and the old gob made by mining the previous panel.1 Portions of the tailgate entry are sometimes closed to such a degree that extensive repair work is necessary to keep the entry in usable condition. The purpose of this paper is to present the result of a study in progress which combines field measurements with numerical model analysis to reduce the cost of maintaining tailgate entries in longwall mining systems.

Jan 1, 1975

By Peter Cain

Longwall extraction in the Phalen Scam in the Sydney Coalfield of Nova Scotia is carried out under flooded abandoned workings in the Harbour Seam 140 m above, and at depth of up to 700 m beneath the Atlantic Ocean. Careful planning of panel and pillar dimensions is necessary to prevent inflows from the overlying workings and to prevent the development of excessive subsidence strains at the seabed. This paper briefly summarises the research undertaken over the past five years by CBDC and CBCRL into the problems associated with mining under water, and then describes the development and application of a design/planning code of practice developed jointly by CBDC, CBCRL and mine regulatory agencies. The design method employed in the Code of Practise is based on empirical data from the coalfield and parameters developed from subsidence modelling and previous water inflow experience. It includes precautionary measures to be adopted during development and mining, and monitoring procedures to be followed. It is flexible enough to allow future developments in the understanding of inflow mechanisms to be incoporated without major modifications, and represents a major step forward in reducing the potential hazards associated with coal extraction in the coalfield.

Jan 1, 1996

By Jinsheng Chen, S. S. Peng

The relationship between support performance parameters and parameters representative of mining and roof conditions is characterised by uncertainty, non-linearity and dependence, so the theory of artificial neural networks was selected as a basis for shield design. A computer program based on a back-propagation training algorithm was written to derive the weighting factors between inputs and outputs from field data; once these had been established two mathematical models were developed to describe the relationship. Back-calculation of field data indicates that the results generated from the neural network models are much more accurate than those derived by traditional methods and can be used with a higher level of confidence. The support density, possible yield frequency of face supports and interval of periodic roof weighting under specific mining and roof conditions can be determined by application of the models

Jun 21, 1905

By D. S. Choi, D. L. McCain

A method of estimating the chain pillar size required to support the wide working faces of longwall or shortwall coal mining is presented. The pillar size is determined through the use of coal strength, entry geometry, panel width, and overburden pressure. Design analysis is focused on a three-entry development system in the Pittsburgh Seam but can be used for other development plans and other seams by substitution of the proper geometric and strength data.

Jan 1, 1981

By Joel Nonnweiler, David Young, John Hawley

The Sacramento Regional County Sanitation District has implemented a billion-dollar interceptor system master plan, including the 31 km (19 mile) long Lower Northwest Interceptor (LNWI). For the two LNWI Sacramento River crossings, pipe-jack/micro tunnel drives in excess of 300 meters (1,000 ft) from 30 meter (100 ft) deep shafts in mixed soil conditions below the water table were considered, as were600 meter (2,000 ft) tunnel drives utilizing pressurized-face tunnel boring machines. Operation and maintenance concerns, predicted flood scour, and levee concerns are discussed. A risk assessment process was used to select both profile and construction method. Construction will begin in mid 2004.

Jan 1, 2003

By P. Forrest

Based on the results of mathematical analysis, photoelastic modelling, and case studies, the mechanisms of longwall under- mining interaction has been thoroughly investigated. The effects of using yield pillars in combination with rigid pillars in lower seam mine design have been found to provide significant improvement in ground conditions during undermining. Off- setting of solemnized longwall panel entries relative to upper-seam remnant structures has proven to be effective in alleviating adverse stress conditions.

Jan 1, 1988

By Rollin A. Slater

The bulk materials handling industry has served silently for years as the skeleton structure and often the central system of nerves and nourishment for the body of basic production industries. During the past two decades, this body has undergone substantial growth and mutation to meet the surging demands of our national economy for more and better products. The steel industry has been prominent in this phenomena and plants of the sixties are as unlike the second war vintage as our current crop of basketball players differ from their fathers. Steel has kept pace with spiralling demand by innovation which has resulted in new processes and improved designs which generally yield greater production from fewer units. The supporting industry of materials handling has likewise improved its techniques and currently has a new stronger generation of equipment to perform its necessary supporting function. It has been my fortunate experience to have been instrumental in the creative stages of several new steel mills which are currently in conceptual design or actual construction. Drawing upon exerpts from this experience, this paper will describe a basic approach to the selection and application of modern bulk materials handling systems to an entirely new steel plant. Specific details of past work are not available for publication, therefore, the plant described herein is a composite of ideas and will be the new plant of the Hypothetical Steel Corporation which will be located on the lower shores of the Great Lakes.

Jan 1, 1967

The paper describes the design of the dilute medium and medium recovery circuits installed at the coal preparation plants at the Cornwall Coal Company's Fingal Mine, and the BP Coal Australia's Howick Mine. These circuits maximize the use of clarified water for rinsing to improve the mass transfer of adhering medium from the coal surface into the carrying liquid, and have been combined with the use of a two stage magnetic separator. The separator utilizes a conventional concurrent first stage and a counter-rotation second stage. This combination results in high medium recoveries during both normal operation, and start up and shut down phases when large quantities of medium can be lost from a conventional circuit. Overall losses using this circuit have been estimated to be, 200g/t, over a twelve month period. Further advantages in plant operation are also obtained, especially steady operating conditions in the centre-tube pump tank, lower slimes contamination of the product, and lower quantities of non magnetics trapped in the separator concentrates. The techniques are particularly suited to incorporation in circuits treating coals containing high percentages of sticky and difficult clays, as are found in the Walloon coal measures.

Jan 1, 1987

By B. P. Watson

The Bushveld platinum group metal deposits are two distinct, shallow-dipping stratiform tabular orebodies which strike for many hundreds of kilometres. Mining is extensive, with depths ranging from close-to-surface to 2 300 m. The mining method is a variation of planar open stoping. Pillars are widely employed to support the open stopes. In the deeper levels, in-stope pillars are required to fail in a stable manner soon after being cut, and the residual pillar strength is used to stabilize the hanging wall. These pillars are commonly known as crush pillars. Little work has been done in the past to determine pillar peak and residual strengths, and pillars have been designed using experience and formulae developed for other hard-rock mines. This has led to over and undersize pillars with consequential loss of ore, pillar bursts and potential collapses. This paper describes a crush pillar design methodology, and provides design charts. Three mining environments were incorporated in the investigations, which included underground and laboratory measurements, analytical solutions, numerical model sand back analyses. The results of the study are suitable for the areas where the research was carried out, and may also be applied with caution in other similar environments.

Jan 1, 2010

By J. C. Loretto

The philosophy and detail of mill design in developing countries, where it is frequently difficult to obtain experienced, qualified supervision to operate the plant, are discussed. The resulting design suggests the desirability of simple units, with maximum visibility of equipment operation and material movement, which allow the minimal technical supervision to see the plant conditions prevailing. Information on plant conditions during periods of lesser supervision can be provided by the use of simple, low-maintenance recorders. Where the mill is intended for operation in a developing country, it is insufficient for the flowsheets and plant layouts merely to be drawn: the process metallurgist must pay meticulous attention to details that could ordinarily be left to the design detailing group. The design of this type of mill requires a knowledge of human engineering—of the type of individual who will operate and supervise the plant; probable changes in personnel should be taken into account. Details are suggested for coarse-ore handling, screens, feeders, secondary and tertiary crushers, conveyors, dust collecting, fine-ore feeding, grinding mills, conditioners, flotation, thickeners, filters, reagent systems, sand pumping, sampling, instrumentation, safety and construction

Dec 1, 1971

By J. C. Bowling

Factors governing the choice of building types, materials, and the details of construction for mineral processing plants in remote locations with cold climates are discussed. Alternative types of building insulation in common use are described and a comparison is made of their suitability under various conditions.

Jan 1, 1973

By Deutsch G. P

The output of an underground mine often depends entirely on the mine winding system. -Decisions made--at the design stage affect the economy and operation'of the mine'.througb -its entire life. A modern mine winding installation is an integrated system and its design requires a multidisciplinary approach including expertise in the-materials handling, mining, mechanical, civil, structural, electrical and control engineering fields. The paper-sets out the elements of typical mine wind- ing systems-and describes some of the more important decisions which must be made during the planning and design process, It is no longer.adequate to. base the choice of a system on the pre- ferences and experiences of individuals. Major Australian winding install- ations are usually designed on the basis of overseas experience and some of the detail design is often carried, out overseas. Differences in basic design criteria occur from country to

Jan 1, 1973

By Laxaminarayan Holla

Significant coal reserves in New South Wales lie underneath major bodies of natural and stored surface waters. In order that mining can occur safely and without any adverse effect on the surface, various statutory provisions and administrative guidelines have been framed for regulating the surface and sub-surface strata disturbance. There are particular bases for the existing guidelines and the assumptions which were made in their choice. Evaluation of the guidelines in the light of the knowledge gained during the last ten years indicates that they are conservative in some cases and can be made less restrictive without lowering the safety standards. The suggested changes include reduced width for pillars in both bord and pillar first workings and panel and pillar workings, and increased level of extraction for a given degree of subsidence. Changes, if implemented, would lead to increased coal recovery.

Jan 1, 1987

By Gary E. Butts, Paul R. Smith

Introduction The design of a mineral processing flowsheet involves many factors. The importance of the sample can not be overemphasized. Competent and thorough mineralogical examinations are important as an aid in designing the test program. Designing and conducting the laboratory test program is basic to the design of the flowsheets. In the project under consideration a flotation pilot plant was conducted to prove the process and to provide a realistic prediction of metallurgical results. Moreover, the pilot plant operation provides important pilot plant design data. Finally, accurate and clear reporting is essential so that the information developed can be utilized advantageously by the client and the engineering firm. The design of a minerals processing flowsheet is a team effort. Engineers from the mining company, the research organization, and the engineering firm all contribute to the effort.

Jan 1, 1978

By Verya Nasri, Mehdi Bakhshi

The development of the Montreal metro extension Line 5 -Blue Line- toward the northeast are located between the existing Saint-Michel station and Anjou. It consists of 6-km long two-track tunnel, five new stations and six auxiliary structures. Most of the tunnel (5.5 km) will be excavated by a 9.6 m diameter shielded rock TBM and supported by a precast segmental lining system. TBM will be fitted for probing and preexcavation grouting to control water inflow into the tunnel during the excavation. This paper presents major design aspects of the TBM tunnel including alignment, geological condition, spaceproofing, precast segmental lining, and geotechnical instrumentation and monitoring.

Dec 1, 2022

By E. B. Johnson, G. Kjerbol, L. J. Holloway

The Mount Baker Ridge Tunnel is a major improvement of Interstate Route 90 in the State of Washington. The total length of planned underground construction is about 3,400 feet (1,040 m) of which 1,332 feet (406 m) will be constructed by a stacked-drift tunneling method. Sized for vehicular traffic on two levels, the net interior diameter will be 63 feet (19.2 m) requiring an exterior diameter of about 80 feet (24.4 m). The material to be excavated is predominantly stiff clay, and this will be the largest-diameter tunnel ever attempted in soft ground. A construction contract for the stacked-drift tunnel was awarded in late 1982.

Jan 1, 1983

By D. J. Reddish

An understanding of the mechanisms that cause large seismic events in a deep mine provides a foundation for designing effective measures to reduce the incidence of these events, as well as reduce the potential for damage arising from these events. The work described in this paper focuses analytical efforts on major recognizable and controllable factors that influence mining-induced seismicity and serves to screen out many of the more random aspects of individual events. Information used in this study was developed in the course of a long-standing rock burst research program conducted by the U. S. Bureau of Mines in cooperation with mines in the Coeur d'Alene Mining District and regional universities. Information was collected on 39 seismic events having local magnitudes greater than 2.5 that occurred between 1989 and 1994. Five major types of events were developed from these data that describe all but two of the 39 large events. The characteristic mechanisms, tint-motion pattern, damage pattern, and relationships to mining and major geologic structures were defined for each type of event. This information provides a foundation for assessing whether or not changes in mining activity aimed at reducing one type of rock burst will increase the incidence of other types.

Jan 1, 1996

By T. K. Akopyan, E. A. Naumova, V. V. Doroshenko, N. A. Belov

"A qualitative and quantitative analysis of the new Al-Ca-Mn-Fe phase diagram in the region of the aluminium corner is carried out using both thermodynamic calculations and experimental methods. Using the obtained data, the principal possibility of creating both cast and wrought sparingly alloyed aluminium alloys with calcium, manganese, scandium and zirconium at allowable iron contents of up to 0.4% that do not require solution treatment and quenching is justified. At the selected concentrations, the entire amount of manganese (1%) is practically included in the aluminium matrix, while calcium (~2%) and iron are in the multiphase eutectic, which has a fine structure. The joint introduction of 0.25% Zr and 0.1% Sc into the alloy leads to precipitation hardening due to the formation of the L12-Al3(Zr,Sc) phase during annealing. Based on the experimental data for the model multicomponent Al2CaMnFeZrSc alloy, it is shown that such alloys can combine high mechanical properties and good manufacturability during both casting and metal forming. This is due to the combination of a narrow temperature range of solidification with a fine eutectic structure.INTRODUCTION Hardening in branded aluminium alloys (both cast and wrought) is generally achieved by heat treatment of the T6 type, including quenching and artificial aging (Zolotorevskiy, 2007; Kaufman, 2004; Mondolfo, 1976). Heat treatment significantly increases the cost of the final products. Therefore, industrial companies are interested in developing alloys that can be hardened to the desired level without quenching. To solve this problem, alloys with scandium are the most suitable (Toropova, 1998; RØyset, 2005). This element (usually in an amount of ~0.3%) is one of the most effective hardeners in aluminium alloys, due to the formation of Al3Sc (L12) phase secondary precipitates, the size of which is less than 10 nm (Knipling, 2010; Fuller, 2005). These nanoparticles are formed during the annealing via decomposition of the supersaturated aluminium solid solution (hereinafter referred to as (Al)). This feature allows us to significantly increase the strength of aluminium alloys by simple annealing (at ~300°C), i.e., without heat treatment, including quenching. However, scandium is a very expensive metal, so its use as an additive is severely limited. The most effective method is the introduction of scandium together with zirconium (Lefebvre, 2009; Booth-Morrison, 2012). The optimal combination is the introduction of ~0.1% Sc together with 0.20–0.25% Zr, which, according to (Belov, 2006), gives approximately the same strengthening effect as the introduction of 0.3% Sc."

Jan 1, 2018

By Verya Nasri

The Silver Line Phase III Project is the final one mile underground segment of the new Bus Rapid Transit in downtown Boston. The project is expected to significantly reduce existing and anticipated traffic congestion. The twin one-lane tunnels and two station platforms will be built by NATM in Boston saturated soft clay, sand and till layers in proximity to several historical buildings, underpinning two existing cut and cover subway stations and several major utilities in densely built urban area. This paper presents the analysis and design of the NATM tunnels and stations detailing the excavation sequence and support system and various ground improvement and pre-support techniques used in the preliminary and final design of the project