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By Meili Zhu, Qingpu Shi

High temperature, methane, dust and other disasters are getting more serious with mining depth getting deeper and the development of mechanization in underground mines. An application of a descensional ventilation to a coalface is one of the effective measures to solve the above problemes. The descensional ventilation is an venttilation that an airflow in a coalface wouuld downflow along an inclination of a coalface and the direction of the airflow is the same as coalflow. Since 1960's, the descensional ventilation has been applied to 171 coalfaces in 46 coal mines of 23 coal mine administrations in China, such as Pingdingshan , Zhongliangshan, Pubai, Huangshi coal mine administrations. Among the 171 coalfaces, there were 104 coalfaces taking 60.8% in gently inclined seam. The coalfaces in inclined seam and steep seam were individually taking 18.7 % and 20.5 %. There were 77 coalfaces taking 45 % of the total in low gassy coal mines and coal and methane outburst mine were individually taking 17% and 38%. There were 141 coalfaces taking 82.5% of the total in potential danger of dust explosion. There were 125 coalfaces taking 73.1% of the total in potential danger of spontaneous combustion. Therefore, the descensional ventilation can be used in coalfaces under different conditions in China. The practice at home and abroad shown that the application of the descensional ventilation to coalfaces has obvious results in dust control, temperature control, preventing methane accumulation at top corner angle and control of spontaneous combustion in goaf. To more safely and reliably apply the descensional ventilation to coalface and to provide a way for the development of mine ventilation technology in China, the paper will have discussions on the following problems: METHANE EMISSION AND DISTRIBUTION AT COALFACE WITH DESCENSIONAL VENTILATION Methane emission in a coalface with a descensional ventilation is an argued issue for many years. Base on the coal practice, special similar model tests and researches in China, the followings are our main comments. The Descensional Ventilation can Reduce the Methane, Accumulation at the Top Corner Angle. The measurements in six coalfaces with the downward airflow in Qinhemen Mine, Fuxin Coal Mine Administrations shown that the methane concentration at the top corner angle is often up to l% when the coalface has the upward, airflow. The max. methane concentration at the top corner angle is about 0.49 to 0.7% when the coalface has the descensional ventilation. Therefore, with the descensional ventilation, it basically solved the overlimited gas concentration at the top corner angle which is a potential danger to coal production. Because the direction of upfloating gas is opposite to the direction, of the descensional airflow, the descensional ventilation; could increase a turbulent flow mixing capacity of the methan gas and air, and reduce a possibility of methane; accumulation. Due to an air leakage in goat when the coalface with the descensional ventilation lower than an air leakage in goat when the coalface with the, ascensional ventilation, a less methane quantity will release from goat at the descensional ventialtion. It should be pointed out that due to a higher air leakage at ascensional ventilation and the direction of the air; leakage same to the direction of the natural upfloating methane in goaf, those will cause a large methane; accumulation at the top of the goaf and easy bring about, methane accumulation and overlimited methane concentration at the top corner angle with an ventilation vortexflow at the top corner angle. On the other hand, because the direction of the upfloation force function is upward, the descentional ventilation could minimize as possibility of methane accumulation at top corner angle in coal with the descensional ventiltion.

Jan 1, 1991

By Andy Ingriselli, Andrew Famiglietti, John Westland, Greg Landry

Atlas Dewatering was contracted to install and maintain a groundwater control system for the new Bessarion Subway Station and the Tail Track Structure on the Toronto Transit Commission’s new Sheppard Subway Line. Atlas met the challenges presented by the project by closely reviewing the contract documentation provided by the Program Geotechnical Consultant, Golder Associates and by working with the general contractors, Bondfield Construction Company and PCL Constructors Eastern, inc., throughout the duration of both projects. In addition to concerns about soil loss, excessive settlement and seepage, the consultant was concerned about spreading hydrocarbon-contaminated groundwater between the two aquifers present at the Bessarion Station site. By installing a system of multi-level vacuum eductor wells around the perimeter of the excavation, Atlas was not only able to provide a dry excavation for construction, but, due to a unique well design was also able to prevent cross-contamination of the aquifers.

Jan 1, 2001

By Paul C. Schmall, John F. Donohoe, Arthur B. Corwin

In the aftermath of the September 11th attack on the World Trade Center, groundwater control was of immediate concern. Water in?ow from the adjacent Hudson River through the compromised slurry wall ‘bathtub’ surrounding the site, ruptured water and sewer mains, and saturation from fire hoses all contributed to an already critical situation, further hampering the recovery and rehabilitation effort. An extensive pumping and deep well installation program was initiated, focused on reducing the hydrostatic loading to the severely damaged perimeter slurry wall.

Jan 1, 2003

By John A. Cordes, John J. Schanz

INTRODUCTION The economic structures of industrialized countries require a continuous supply of reasonably priced and appropriately processed nonfuel minerals. As a result, national policy makers are sensitive to real or perceived threats to the effective operation of these commodity markets. Their most persistent concerns can be subsumed into the related political economy issues of supply availability and marketplace stability. These concerns are not new. For over a century the "global struggle" for mineral resources has influenced national policies and international relations (Eckes, 1979). During the past two decades the complexity of these issues, if not their place on national political agendas, has increased. Dramatic changes in the structure of mineral industries and in the nature of international economic relations have redefined policy needs and response options. This paper focuses on how selected OECD countries have responded to nonfuel mineral industry issues over the past twenty-five years. Particular emphasis is placed on the impact these policy decisions have had on the size and location of productive capacity and its utilization rates. The results, perhaps, are not surprising for this group of market- oriented economics. While individual cases of significant impact are easy to identify at various times in most countries, the overall importance of policy decisions has not been great. This is especially true for the past decade when excess capacity reached unusual highs of magnitude and duration. Macroeconomic forces and market structure changes played much more important roles. PERSPECTIVES ON THE ISSUES OECD nations dominate the international nonfuel minerals marketplace as producers, consumers and traders. In 1986, these twenty-four countries accounted for 75 percent of the Western world's export trade value in minerals, ores and metals. They imported 88 percent of the total value. During 1966, the respective percentages were 70 and 94. Japan was the world's largest importer in 1986 followed by the US, FRG, UK and France. The same five countries led the 1966 list except that, then, Japan was ranked fourth. Table 1 ranks the fifteen largest Western exporting nations in the two specified years. It also indicates the growth in current export dollars earned in 1986 compared to 1966.

Jan 1, 1989

By Janet Briggs, Michael Vertes, J. F. Shirley, R. E. Cutherbertson, Alexander Sutulov, J. D. Vincent

Molybdenum, the 42nd element in the periodic table, is now a very important metal in industry of the United States and the world. Chemically, it is a very complex element having valences of 0, +2, +3, +4, +5, and +6, and can exist as a mixture of these valences in many compounds. It was discovered and separated by Scheele in 1778. At the present time, molybdenite is the only important commercial source of molybdenum. Molybdenum occurs in some 12-14 different recognized minerals, but practically all of the production is molybde¬nite. As late as 1915, it was considered a rare metal. Germany made extensive use of it during the first world war, which resulted in the establishment of a molybdenum industry in the United States at Cli¬max, Colo., in 1917. It was not until the mid-1920s when its introduc¬tion to steelmaking developed for the US automobile industry that the metal gained important acceptance. The first notable example was the Willis-Saint Claire automobile introduced in 1921 by C. Harold Willis, formerly chief metallurgist for Ford Motor Co. Molybdenum has also been produced in the US from wulfenite (PbMoO4) from Arizona and Nevada, and a small amount of molyb¬denite was produced up to the early 1970s as a coproduct from two molybdenum-bismuth mines in Quebec, Canada. The first byproduct production of molybdenite from a copper con¬centrating operation was achieved at Cananea, Sonora, Mexico, and was followed shortly by the Utah division of Kennecott Copper Co. in the mid-1930s. This section of the Handbook is divided into four main subdivi¬sions: Chapter 2, which deals with the concentration and recovery of molybdenite from primary molybdenum ores; Chapter 3, which deals with the recovery and separation of molybdenite as a byproduct from copper production; Chapter 4, which deals with the conversion practices employed for converting molybdenite to the oxide or metal form; and Chapter 5, which covers the uses of molybdenum in steel¬making, chemicals, pigments, lubrication, catalysts, etc. The Free World molybdenum production, for the past eight years from all sources, is shown in Table 1. 2. Primary Molybdenite Ores General In 1978 there were four primary molybdenite recovery plants in operation: Climax, Endako, Quests, and Henderson. For over half a century the Climax mine has been by far the largest and most important source of molybdenum in the world. During the early 1970s a few primary molybdenite mines in British Columbia were shut down due to adverse economical conditions. The largest of these was British Columbia Molybdenum, formerly owned by Kennecott Copper Corp. The Climax plant and operations are described in detail and the opera¬tions of the other plants are summarized following a general discussion of recovering molybdenite from primarily molybdenite ores. Recovery of molybdenite as a byproduct will be taken up in Chapter 3. Geology Molybdenite production from mines in which it is the sole or preponderantly important mineral is confined to ore bodies in granites or igneous-type rocks or pegmatite dikes. More than one state of mineralization is sometimes present as at Climax, York, Hardy, and Questa. In the case of Climax, important byproduct recovery of tung¬sten, tin, pyrite, and monazite is also attained. The molybdenite is commonly disseminated very finely in the siliceous granitic gangue but does occur in stringers and blebs in silicified mineral solution channels. Treatment of Primary Molybdenum Ores All primary molybdenum ores are low in molybdenite, the content ranging from less than 0.20% MoS2 to a high of about 0.40% MoS2. A high resistance to grinding is a common ore characteristic combined with a habit of very fine dissemination of molybdenite in the siliceous portion of the ore. Because of low MoS2 content, high hardness, and fine dissemination of molybdenite in primary ores, it has been necessary to develop a special mill treatment which yields an accepta¬ble recovery at a reasonably low milling cost. Essentially, the treatment consists of intensive rougher flotation at a relatively coarse grind with production of a low grade rougher froth containing a substantial percentage of the molybdenite in the form of low grade middling particles, followed with multistage regrinding to liberate the locked molybdenite and several stages of flotation cleaning to produce a finished grade concentrate. Rougher flotation on pulp ground to ap¬proximately 35 mesh is common practice, even if complete liberation of molybdenite from siliceous gangue may require regrinding to 200 mesh. The flotation of middling particles with a very low content of molybdenite in the rougher flotation step has been made possible by the application of a combination of reagents first developed at the Climax mill and used with some modification in the treatment of all primary molybdenum ores. The reagents commonly employed and their functions in flotation are:

Jan 1, 1985

By G. Troly, M. Esterle, B. Pelletier, W. Reibell

In New Caledonia, ultramafic formations occur on 7,000 square kilometers. Weathering of peridotites leads to profiles of alteration and nickel concentrations. Complete profiles are composed of two main groups of horizons: 1. Limonitic, mainly composed of iron hydroxides 2. Saprolitic, partly composed of magnesium and iron silicates Shape and mineralogical composition of saprolitic horizons are chiefly affected by the nature of the bedrock: types of peridotite and their degrees of serpentinization. On the other hand, morphology (plateau, terraces, slopes, piedmont) is an important factor. Ore-bodies are inside saprolites; their outlines are determined by the grade of nickel and tonnage economically mineable. Information about geology, morphology, geochemistry, and mineralogy are given in this paper.

Jan 1, 1979

By S. S. Peng

This paper presents a computer program package for predicting surface movement and deformation caused by under-ground coal extractions. It is capable of: predicting final surface movement and deformation over underground openings; predicting dynamic surface movement and deformation process associated with underground lingual mining operations; processing and bookkeeping subsidence survey data; recommending subsidence parameters for those new coal mines where no subsidence data are available; and deducting subsidence parameters from collected subsidence data.

Jan 1, 1986

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

The paper examines current room and pillar mining practice in the U.S.A. from the standpoint of rock mechanics. Consideration is given to the deformation characteristics of the roof formation and the coal seam as determined in the laboratory as well as in the field. The results can be utilized by the practicing mining engineer to improve current mine design practice.

Jan 1, 1982

By S. K. Kawatra, Harrison R. Cooper

In the last 30 years, on-¬stream slurry analyzers have proven to be of great use in the control of mineral processing circuits. This review discusses the two most popular methods, x-ray fluorescence and neutron activation analysis, and also considers techniques which are still under development.

Jan 1, 1986

This chapter contains the edited transcript of the "Gold Heap Leach Information Exchange" session that was held at the 1990 SME/AIME Annual Meeting in Salt Lake City, Utah. The exchange occurred on the afternoon of February 27, 1990. The session was intended to act as a forum for discussing some of the more prominent operating problems associated with heap leaching precious metals. The information exchange was very successful. The exchange consisted of several panelists introducing and discussing different topics, follow by a comment and question period. This transcript contains the panelists' presentations as well as comments and questions from the floor and the panel. Extraneous comments and remarks have been edited out. Some wording has been changed for clarity, but the transcript is basically an accurate account of what was said. At the end of the transcript are two papers submitted as part of the panel discussion

Jan 1, 1990

By Georgios Kafantaris, Carsten Bonde, Nataša Katic

Within the investigation works for the Copenhagen Cityring metro, Geo/CMT have carried out 90 geotechnical boreholes. Together with the previously available investigation, this resulted in more than 15 km of vertical drillings and several thousands of laboratory tests. The design is made for 17 stations, four shafts and two parallel 16 km long tunnels. The geotechnical investigation and design have been carried out in several stages comprising appropriate refinement of structural design and design of excavation operations, including TBM break-in and launching operations at each station shaft. Acceptance of the solution and / or refinement of the investigation and design schedule in the next stage were based on the geological conditions, area availability at surface level, planning and cost-control criteria. The applied recursive design refinement is presented herein with an example of the Østersøgade shaft location.

Jan 1, 2016

By S. Dubnewych, S. Kieffer, M. T. McRae, R. R. Redd

The seismic vulnerability of the existing outlet tower at Lake Mathews reservoir, located in Riverside County, California, necessitated the design of a new outlet facility to assure serviceability of the facility following a major earthquake. The components of the proposed facility include: a new outlet tower; a shaft; a new outlet tunnel; an approach channel that will be excavated underwater; and two short tunnels that will connect the new outlet tunnel to the existing outlet tunnel via the shaft. As the new facilities will be constructed while the reservoir is in operation, a cofferdam will be constructed around the site of the new outlet tower. The design for the underground facilities used a combination of empirical methods; limit equilibrium analyses, including displacement-based pseudo-static analyses for dynamic loading conditions; and numerical analyses. This paper outlines the design methodology used to develop an innovative design for the facilities which can be constructed within the time frame required by the operational schedule of the reservoir and existing outlet facility.

Jan 1, 1999

By J. Herbst, C. C. Harris, G. Poling

The modern flotation machine is the result of decades of adaptation to a changing environment. In response to falling ore grades, and rising demands, tonnages, and costs, attempts are now underway to expand machine capacity by about an order of magnitude, while at the same time maintaining metallurgical performance and if possible reducing power requirements per unit throughput. Empiricism and rule-of-thumb have guided flotation machine design and scale-up, and a current need is for the development of a fundamental understanding of the subject. Design features of current and some obsolete machines are discussed in an attempt to outline those principles of flotation machine design which are known, and to delineate topics needing investigation. Attempts are made to distinguish between essential machine features required by the physics of the process, those features resulting from speculative theories on the flotation mechanisms, and features which are essentially styling variations. Topics discussed include: flotation mechanisms; tank and impeller/ stator design and dimensions; impeller speed; aeration; power consumption; particle suspension and dispersion; capacity; correlation of design parameters and operating variables; scale-up and scale- down; materials flow; problems in machine design. Design details and operating data for several current machine families are provided in Appendices.

Jan 1, 1976

By K. Rajamani, I. Shah

The development of liquid-level control algorithms, based on sets of linguistic rules expressing human operator's "intuitive" control strategies, have been reported. The main objective of the present paper is to illustrate the implementation methodology. The experimental work was done with a 28.3Lflotation cell. The control variable (height of pulp in the cell) was controlled by manipulating the outflow rate. The controller algorithms were programmed and implemented using an Applelle computer and a Keithley das Series 500 measurement and control interface. It is pointed out that the scheme of fuzzy controllers is simple to use and powerful enough to handle complex and nonlinear systems.

Jan 1, 1987

By Eleanore L. Nestlerode, James R. Guilinger

In April. 1990 Addwest Minerals acquired the Phillips Ranch sulfur property. The sulfur deposit, hosted by the Permian Castile anhydrite, occurs as two distinct elongate. parallel orebodies within a series of northeast-trending grabens. After completing a positive feasibility study, based, in part. on successful drilling programs by Addwest Minerals and previous operators, the decision was made to place the property into production. Utilizing an existing on-site kasch plant, plus significant portions of the recently purchased Texasgulf Comanche Creek Frasch plant. Addwest is currently constructing an 800 long ton per day Frasch mining facility.

Jan 1, 1992

By Miklos D. G. Salamon

The laminated model, in conjunction with the seam element method, is expected to be a powerful predictor of subsidence due to coal mining. The fundamental solutions for the model are presented. Numerical approach to determine the roof-to-floor convergence and evaluation of ground movement are discussed. Numerical results and comparisons with field observations are given to illustrate the validity and the potential of the model.

Jan 1, 1986

By Richard C. Fox

"Why geophysics? We will have to drill anyway." Reliance on geophysical methods for detailed target appraisals will increase as direct surface evidence becomes more subtle. This will create a need for more effective and efficient geo- physical programs. Numerous computer-based techniques that deal with a broad range of geophysical problems are described in the literature. The purpose of this chapter is to provide a framework for the systematic application of these techniques to effect an overall optimization of the geophysical appraisal. The concepts described are not technique specific, but should serve as a guide for increasing the effectiveness and efficiency of any geophysical program. Fig. 1 shows a generalized flow chart of the major aspects of the program described. The three main subdivisions of a 'geophysical program are discussed: (1) survey design, (2) data processing, and (3) data interpretation. Detailed flow charts, outlining the goals, the requirements for meeting the goals, and the steps followed within each subdivision are presented at the beginning of each section. The objectives and type problems of each subdivision are defined, followed by a description of applicable computer methods. . References are cited that give a general cross section of computer techniques available in the literature, and examples are given in each subdivision to demonstrate basic concepts and the use. of computers in solving the type problems.

Jan 1, 1979

By Gordon T. Clark, Stephen H. Gleaton

This paper discusses the conceptual design of cut-and-cover tunnels currently being considered as one of the replacement options for the earthquake damaged, elevated double-deck highway and seawall built in downtown Seattle 50 years ago. The 4.8 km (3 mile) long, 6-lane improvement consists of 1.6 km (1 mile) of at-grade roadway with aerial interchanges, 1.6 km (1 mile) of large two-level cut-and-cover tunnels along the Elliott Bay waterfront, and retrofit of the 50-year old, 1.6 km (1 mile)long Battery Street tunnel and north transition to grade. Construction of deep cut-and-cover tunnels, in complex glacial geology overlain by hydraulically placed fill immediately adjacent the existing sea wall, will require extensive use of concrete diaphragm walls, ground improvement and dewatering. The potential liquefaction and lateral spreading of the fill materials in this active seismic region pose significant design challenges and risk.

Jan 1, 2003

By Sanja Zlatanic, Michael P. Della Posta

New York State’s Metropolitan Transportation Authority (MTA) has undertaken the largest transportation project in New York City. The East Side Access Project (ESA) will introduce MTA’s Long Island Rail Road (LIRR) service to the East Side of Manhattan, to a new terminal located beneath the existing, landmark Grand Central Terminal(GCT). Construction of the Manhattan Segment of the project will affect overlying operating facilities of two other MTA entities, Metro-North Railroad (MNR) and New York City Transit (NYCT) and major Midtown Manhattan buildings. The paper describes the evolution of the GCT concept at Manhattan from a shallow alternative proposed by a Major Investment Study (MIS), that would require extensive underpinning of multi-story buildings and have considerable impact on MNR and NYCT operations, to a deep alternative with lesser risk and potential for disruption.

Jan 1, 2001

By Marian Radetzki

The economic developments and industrial behavior patterns that led to a lasting excess capacity in the world non-ferrous metals industries from the aid-1970s are explored. Detailed attention is devoted to analyzing and defining crucial concepts like "capacity", "excess capacity", "capacity maintenance" and "investments". Empirical evidence of capacity utilization and capacity growth in the industries under study is provided. The coincidence of excess capacity and low prices on the one hand, and investments in capacity maintenance and capacity expansion, on the other, is seen as a consequence of substantial declines in the metal industries' investment and production costs during the period studied.

Jan 1, 1989