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By Jan M. Mutmansky

"When, in 1973, a limit was placed on the amount of dust in the coal mine atmosphere, restricting the average exposure of a coal miner to 2 milligrams of dust per cubic meter of air (mg/m'), skeptics in the United States and abroad Said the standard could never be achieved. They cited much more lenient standards already established in other countries and refused to believe that the United States could meet the world's most stringent requirements in mines where dust had never before been regulated. Yet 10 years later the goal had largely been achieved and miners were working underground in a cleaner atmosphere than ever before. It was a major achievement and a big stride in what had become a war on coal workers' pneumoconiosis (CWP), the black lung disease prevalent among miners in underground coal mines.Although the health hazards caused by working in a dust-filled mine atmosphere have long been recognized, the problem became particularly acute in this century with the mechanization and increased productivity of underground coal mining. The United States was much slower than some other countries to address the problem of respirable diseases among miners. While dust levels in South African gold mines were first regulated in 1912, in the United States it was only when 476 workers died of silicosis while blasting a tunnel through a mountain near Gauley Bridge, West Virginia in the 1930s that widespread public attention became focused on the plight of workers in dust-filled environments. Another 30 years passed before regulation of dust finally became law in the Coal Mine Health and Safety Act of 1969.With a stringent new standard imposed in all underground coal mines, the industry was faced With the daunting problem of reducing levels of airborne dust from perhaps 6.5 mg/m' to 2 mg/m', in an inherently dusty operation carried out in the close confines of underground passageways. Most of the coal dust is made by the cutting operation in which the continuous miner or longwall machine can produce several thousand milligrams of respirable dust for each ton of coal mined. Other dusty operations such as drilling holes for roofbolts, loading and unloading coal on shuttle cars, and the operation of conveyor belts contribute to the overall problem.Since the institution of the new dust control standards, a number of strategies have been adopted for reducing the coal dust in the mine atmosphere. These strategies involve engineering and design improvements that help lo prevent the generation of particles, keep particles of dust from becoming airborne, carry dust away from the working area, and isolate the dust from the workers in the mining operation. These procedures have been pursued vigorously by the Bureau of Mines, and many successful methods have been developed to reduce the mass concentration to which the workers are subjected. The mining companies were reluctant at first to confront the problems but after a period of trials and gradual improvement, they joined with others in the fight to reduce the dust concentrations in the working place."

Jan 1, 1990

By S Hanke, J Burden, P Spies

The Waterview Connection will complete Auckland’s long-planned Western Ring Route, a 48 km north-south motorway alternative to State Highway 1 that bypasses the central city to the west. The project involves construction of 5 km of new motorway – half of it underground in tunnels – to connect the Southwestern (State Highway 20) and Northwestern (State Highway 16) motorways.The Western Ring Route will link the major population and industrial centres of Manukau, Auckland and North Shore to give the region the connected and resilient strategic road transport system it needs to underpin economic growth and sustainable development. It will also provide a direct motorway link between Auckland’s central business district (CBD) and international airport.The project involves construction of twin 2.4 km driven tunnels with an outside diameter of 14.41 m beneath residential suburbs, a major arterial road and a rail corridor. Enabling works began in January 2012 while tunnel construction using an earth pressure balance (EPB) tunnel boring machine (TBM) began in November 2013.This presentation introduces the Waterview Connection project, its role in the development of the Auckland motorway network, its procurement process, the alliance delivery model and an overview of the project’s design features and construction progress to date.Design and construction highlights of the presentation include the TBM start-up, turnaround and breakthrough arrangements as well as the experience gained during the first tunnelling drive. The presentation also covers an innovative process developed for invert construction behind the TBM that is independent of tunnel excavation.CITATION:Spies, P, Burden, J and Hanke, S, 2014. The Waterview Connection Project – progress to date, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 519–540 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Michael B. Cortie

The young field of nanotechnology has as its objective the design and construction of useful devices made of nanoscale materials. Objects or structures which have at least one important dimension in the range 0.5 to perhaps 50 nm may be considered to be in the nanoscale domain. These sizes lie far below the 200 nm or so that can be resolved with an optical microscope, and are closer in size to the 0.3 nm diameter of individual atoms. Nanotechnology, which is the study and exploitation of these tiny structures, is attracting keen interest at present. The excitement is motivated by the observation that control of matter at the nanoscale holds the promise of faster computing, better medicines, and smarter materials. In this paper, the physical phenomena on which this optimism is based are broadly discussed and explained. Where appropriate, examples of the rather different and curious properties of gold at the nanoscale are used to illustrate the points covered.

Oct 1, 2003

By E. M. Stiles

THE Wellington Lake power plant of the Consolidated Mining and Smelting Company of Canada, Limited, about 25 miles from Goldfields, Saskatchewan, is the second hydro-electric project operating in that Province, the first being the Island Falls plant of the Churchill River Power Company which serves the operations of the Hudson Bay Mining and Smelting Company at Flin Flon, Manitoba. The Churchill River project develops 90,000 h.p. at 56-ft. head; the Wellington Lake plant 3,300 h.p. at 75-ft. with pro-vision for an additional 3,300 h.p. unit. Churchill River power is trans-mitted at 110,000 volts over a 58-mile line of steel towers to Flin Flon and an additional 45 miles over a wooden pole-line to Sherritt-Gordon. Our steel tower-line is 22 miles long, and the voltage is 60,000; this choice be-cause certain such equipment was available from Trail. The diversion of 15,000? second-feet at 56-ft. head for 90,000 h. p. at Churchill river dwarfs our 500 second-feet flow at 75-ft. head for 3,300 h.p. In both cases, the main obstacles to be overcome during plant construction were the lack of transport facilities and the short open season. Let it be noted here that this paper deals mainly with those phases of plant construction which were particularly interesting to the writer. With-out these variations from the ordinary routine, this is just another power project whose story is better told by the accompanying charts and pictures. To many members of the Institute it is still just that; but I am writing for those who, like myself, have been too seldom responsible for major under-rakings at an appreciable distance from a railway siding. When it was planned in early 1937 to erect a 1,000-ton mill at our Box mine, both hydro and Diesel power were discussed. With ten years' ore in sight, even an expensive hydro project, such as ours turned out to be, produces kilowatts materially below the 2-cent operating cost of a Diesel plant using fuel-oil at 14 cents a gallon.

Jan 1, 1940

By Richard Switalski, Thomas Scotese, James Morrison, Randall Essex

OVERVIEW Like many older metropolitan areas across the U.S., the Greater Cleveland area is served by a combination of separate sanitary sewers and combined sanitary-stormwater sewers. In 1966, a Master Plan was implemented by the Northeast Ohio Regional Sewer District (District) to minimize pollutant overflows into adjoining Lake Erie and its tributary rivers and streams, that would occur during wet weather events. One component of the Master Plan was to reduce the load on combined sewers by constructing new conveyances to intercept separate sanitary flows and convey them to upgraded regional waste water treatment plants for priority treatment. As part of a 15-year program to construct 74 km (46 miles) of new interceptors, the West Leg Interceptor (WLI) Project intercepts flows from four decommissioned waste water treatment plants (WWTPs), and conveys those flows to the new Southwest Interceptor (SWI), which conveys the flows to the Southerly Treatment Plant, a tertiary level treatment facility. The WLI Project was built in sections to permit decommissioning of the WWTPs as each segment of the interceptor system was completed and put into service. Flows from the first of the four WWTPs was converted to the WLI in November, 1992; the final connection was achieved in July 1994. The WLI comprises 9.1 km (5.7 miles) of 21 to 29 m (70 to 95 ft) deep mainline interceptor tunnel, four vortex drop structures, approximately 2 km (1.3 miles) of shallow tunneled connector sewer to the mainline, approximately 2.9 km (1.8 miles) of open cut connector sewers, five construction work shafts (not including one work shaft constructed under SWI Contract 6 at the north end of the WLI), and 15 access shafts.

Jan 1, 1995

By J. O. Wheeler

"DEFINITION OF THE REGION, ITS BOUNDARIES, AND PHYSICAL AND GE'OLOGICAL CHARACTERISTICSTHIS PAPER concerns the Western Cordilleran region, embracing most of British Columbia, the southern half of Yukon Territory and the southwestern most part of the District of MacKenzie. It excludes Vancouver Island and the Queen Charlotte Islands, which are discussed in a background paper on the Pacific Continental Shelf. The region is bounded on the south by the northwestern United States, on the west by the continental shelf and Alaska, on the north by the front of the Ogilvie Mountains, on the northeast by the axis of the MacKenzie Mountains and on the east by the Rocky Mountain Trench.The region is dominated by two mountain chains that con tain icefields and glaciers: the St. Elias, Coast and Cascade Mountains in the west; the Selwyn, Pelly, Cassiar, Omineca and Columbia Mountains in the east. The Intermontane region between these mountain chains consists of lower mountains and plateaus. In the mountains, the region above the timberline and many of the steep valley-walls provide good exposures of rock, but these areas are subject to rockslides and landslides and in winter to snow avalanches. Much of the Western Cordillera was covered by ice-sheets at various times during the Pleistocene epoch. Consequently, the larger valleys in the mountains and much of the Intermontane region contain much glacial drift and alluvium and only limited exposures of rock. This same terrain in the Southern Cordillera, however, is the most favourable for agriculture. Parts of the region, particularly in the two mountain chains, are heavily forested. Elsewhere, the forest cover is less, with grassland prevailing in the south and tundra in the north."

Jan 1, 1969

By J. O. Wheeler

"DEFINITION OF THE REGION, ITS BOUNDARIES, AND PHYSICAL AND GE'OLOGICAL CHARACTERISTICSTHIS PAPER concerns the Western Cordilleran region, embracing most of British Columbia, the southern half of Yukon Territory and the southwesternmost part of the District of MacKenzie. It excludes Vancouver Island and the Queen Charlotte Islands, which are discussed in a background paper on the Pacific Continental Shelf. The region is bounded on the south by the northwestern United States, on the west by the continental shelf and Alaska, on the north by the front of the Ogilvie Mountains, on the northeast by the axis of the MacKenzie Mountains and on the east by the Rocky Mountain Trench.The region is dominated by two mountain chains that con tain icefields and glaciers: the St. Elias, Coast and Cascade Mountains in the west; the Selwyn, Pelly, Cassiar, Omineca and Columbia Mountains in the east. The Intermontane region between these mountain chains consists of lower mountains and plateaus. In the mountains, the region above the timberline and many of the steep valley-walls provide good exposures of rock, but these areas are subject to rockslides and landslides and in winter to snow avalanches. Much of the Western Cordillera was covered by ice-sheets at various times during the Pleistocene epoch. Consequently, the larger valleys in the mountains and much of the Intermontane region contain much glacial drift and alluvium and only limited exposures of rock. This same terrain in the Southern Cordillera, however, is the most favourable for agriculture. Parts of the region, particularly in the two mountain chains, are heavily forested. Elsewhere, the forest cover is less, with grassland prevailing in the south and tundra in the north."

Jan 1, 1970

By J. F. KENP

THE White Knob copper-deposits are situated about three miles south of Mackay, on the Salmon River .branch of the Oregon Short Line Railroad, in Custer county, Idaho. An outline-map of this district is given in Fig. 1. The deposits have been known and spasmodically worked for many years, and a total of over 3.5 miles of tunnels, shafts and other workings has been driven with a view to their development. These extensive excavations have exposed the deposits sufficiently to permit a careful geological examination. The peculiar features which give special interest to this paper are the branching, free-like form of the ore-bodies; the absence of zones of secondary enrichment in the partly oxidized pyritic deposits, and the fact that while the deposits are associated in a general way with the contact of an eruptive rock with limestone, which it penetrates, the garnetization has taken place not in the limestone, as is the usual case, but in the igneous

Mar 1, 1907

By Persifor Frazer

THE following notes on the Whopper and adjoining mines in the Gunnison district of Colorado were made in the spring of this year. The time chosen for the author to visit the region was, unfortunately, the most unfavorable of an exceptionably unfavorable year. About the middle of May all the hill slopes, which at this period of the year are generally covered with pasture, were thickly covered with snow. The unusually large precipitation of this year caused local mountain torrents at every few hundred feet, which wore away the soft foothills into gulches, gouged great chasms out of the roads, and transformed miles of usually dry soil into dangerous quagmires. Travel was totally interrupted for weeks, except on horseback or afoot, and even then with great difficulty and some danger. The Whopper mine is situated on the Whopper Mountain, about two miles from the headwaters of Rock Creek, and on the right bank of that stream. The Whopper Creek flows into Rock Creek from the east, and, by a precipitous descent, offers excellent facilities for its utilization as a source of power. This stream, which pours past the picturesque Whopper Cabin .about thirty tons of water a minute, has a fall of 100 feet in 400 yards, and is said to be a stream of some size, even at the seasons of the year when-drought prevails. The Whopper claim extends down the bill a distance of about 250 feet to its intersection with the Whopper Creek (on the other side of which is a small tunnel on its extension called the "Teller ") and over the steep hill northwest to the limits of the claim about 1250 feet. The part of the mountain in which this mine is situated is remarkable for its splendid forest, the spruce, fir, and quaking asp covering the mountain-sides with a green growth of valuable timber. The distance from Gothic City to this mine is about eight miles along the valleys of East River and Rock Creek, and on the divide which separates them. The elevation of Gothic City is given from the engineer's notes as 9500 feet above sea-level, and the mean of several observations with a Beck watch-barometer made the elevation of Whopper Cabin (which is about fifteen feet above the floor of the Whopper upper tunnel) about 1250 feet above Skiles's Cabin in Gothic City. The record of this instrument must, how-

Jan 1, 1881

By Saverio Agresti, Giuseppe Lunardi, Donato Basta, Roberto Trapasso

"At a distance of 10 years from the first application of the Nazzano Method, the widening under traffic of a tube of an existing motorway tunnel was realized near Ancona, along the A14 Motorway in Italy. This paper describes the works for the enlargement with conventional method of the second tube, very close to that already widened under traffic.This enlargement was realized very fast, taking into account the advantages of some interesting technological improvements of the Final Design proved in the first tube.INTRODUCTION TO THE WIDENING OF EXISTING MOTORWAY TUNNELSThe widening of a twin-bore motorway tunnel usually considers the double option of creating a third bore as an alternative or closure to traffic of one of the two bores with the resulting reduction in the level of service for users.On the contrary, the extension in situ of a road, motorway, railway or underground tunnel in the presence of traffic, made possible by an inspired idea of Prof. Pietro Lunardi, enables the level of service of the infrastructure to be maintained without the need to resort to alternative routes to create new permanent or temporary bores, not always feasible because of the lack of the necessary space.This construction technique, known as the ‘Nazzano Method’, is part of the technologies refined and offered by the ADECO-RS approach to tunnel design and construction (Lunardi P., 2008) which is increasingly used in the world, leading to the industrialisation of tunnelling (meaning respect for the times and costs set out during detailed design) both in conventional and mechanised (through TBM) excavations.The first true experimentation of the ‘Nazzano Method’ was carried out between 2004 and 2007 to enlarge the two-bore ‘Nazzano’ tunnel (Italy, Milan-Rome A1 motorway) in the presence of traffic, widening it to house from two to four lanes in each direction (Lunardi P. et al., 2007). Following the success achieved in this first application, the Nazzano Method was strengthened considering all the possible suggestions arising from the previous experience and then taken up to enlarge the north bore of the ‘Montedomini’ two-bore tunnel (Italy, Bologna-Taranto A14 motorway), in situ and the presence of traffic."

Jan 1, 2016

By Hugh S. Spence

This paper deals with an occurrence of radium ore near Wilberforce, Haliburton county, Ontario, upon which development work has recently been undertaken and which seems more likely to prove of commercial grade than any other deposit' of radioactive minerals hitherto found in Canada. This occurrence is sometimes called the Richardson property, after Mr. W. M. Richardson, the discoverer, and will be so referred to in the present paper. Occurrences of radioactive minerals are not uncommon in eastern Canada, and a number are recorded in the literature. The earliest of such references is probably that in Geology of Canada, 1863, where is mentioned an occurrence of uraninite at Mamainse, on the east shore of lake Superior. The mineral was first described by J. L. Leconte, in 1847, under the name of coracite, and was said to occur in a two-inch vein at the contact of trap and syenite. Search for this locality in recent years has proved unsuccessful. Obalski, in 1894, mentions (1) the occurrence of uraninite at a mica mine near Murray Bay, Que. In 1903, Obalski records (2) tests made on this uraninite by Rutherford and the Curies and the determination in it of the then newly-discovered element radium. In 1901, he mentions (3) the occurrence of uraninite at the Villeneuve mica mine, on the Lievre river, and of samarskite at the Maisonneuve mica mine, in Berthier county.

Jan 1, 1930

By Cameron Dunn, Callum Fryer, Carmen Hu, Craig Sewell, Peter Stakne, Andrew Raine

The Woodsmith Project is located in north-eastern England within the North York Moors National Park. The strata contains the world’s largest known high-grade Polyhalite resource of around 2.66 billion tonnes. The Project was initiated by York Potash Limited (YPL), a subsidiary of Sirius Minerals plc., but in March 2020, a takeover was completed by Anglo American, one of the largest mining companies in the world. Polyhalite is an evaporite mineral and contains essential nutrients required for plant growth. The Polyhalite will be extracted via two deep mine shafts and transported underground from the mine site to a Materials Handling Facility on a Mineral Transport System (MTS), which comprises a high-capacity conveyor belt system located within a 4.9 m ID tunnel. In 2018, STRABAG were awarded with the design and construction of the MTS tunnel and associated infrastructure, including the high-capacity conveyor system. The scope of work consists of 300 m of open cut, 100 m SCL tunnel, 36.5 km TBM drive (originally anticipated as three separate TBM drives) along with a network of underground caverns at the Woodsmith Mine. The construction of two 380 m deep intermediate access shafts was later awarded as Amendments to the Contract. The tunnel is constructed using a Herrenknecht Single Shield TBM. As a result of how the various elements of the project have developed over time, the first TBM drive has been extended to ~29 km making it the worlds longest single heading TBM Tunnel when complete. The option of completing the entire tunnel length with a single heading TBM drive is currently being assessed by Anglo American and STRABAG. This unprecedented tunnel length requires two intermediate shafts to provide essential access and services, the first intermediate shaft is at Lockwood beck (LWB) and the second is at Ladycross (LDX). The LWB shaft has been constructed utilising the innovative Blind Boring technique never used before in the UK. This paper will explain the methodology and technical risk management associated with this technique. The authors believe that the collaborative approach between all contract partners is and continues to be the important contributor for the success of this project.

Jun 13, 2023

By O. W. Ellis

Introduction During the month of September, 1928 enough money had. been promised by private individuals and corporations to comply with the Research ?Foundation Act 1928 (Chapter 57, 18 George V) of the Province of Ontario. The Ontario Research Foundation (referred to below as O.R.F.) may be said to 1iave come into being at that time. Under the terms of this Act, the Treasurer of the Province was empowered to match dollar for dollar of the sums subscribed by private .corporations and individuals up to a limit of $1,000,000. However, the response to the appeal for this by the Premier of the Province, the Honourable Mr. G. Howard Ferg uson, was so exceptional that the Act was amended in 1929 so as to empower the Treasurer to increase the maximum contribution on the part of the Province to $2,500,000. In March, 1933, the Chairman of the Foundation, Sir Joseph Flaville, Bart., was able to report that, in the interval between the Premier's appeal and December 1st, 1932, private enterprise had paid ?into the treasury of the Foundation $1,670,050, and that the Provincial Treasurer had assumed responsibility for a like sum. The endownment Fund of the Foundation was, therefore. $3,340,100. This sum was ?invested a lm~ s t entirely in Government securities, in securities guar. anteed by the Government, and in 1mmicipal securities. Sir Joseph Flavelle remarked at that time that "The payment of $1,670,050 to the Endowment of the Foundation by private persons and corporations is a somewhat remarkable performance when it is remembered that for three of the five years the business of the country has been suffering from a severe depression". Since that time it has been the consistent policy of O.R.F. to live within the income derived (1) from the investment of its Endowment Fund and (2) from fees collected for services rendered.

Jan 1, 1950

By M. Dondelinger

This paper presents a comprehensive review of steel sheet piling including internationally manufactured hot rolled sections, their history, applications, installation and driving techniques. The discussion will cover both temporary and permanent installations; temporary piling used in construction of cofferdams with various bracing systems, deep foundation installations for buildings, bridges and tunnels, etc., and permanent piling used for highway, railroad and bridge construction as well as for riverbanks, piers, wharfs and docks, normally required for port facilities. In addition, cofferdams, as self-supporting gravity structures where interlock strength is of prime importance, will be discussed. The design and application of light, intermediate and heavy sections will be presented including heavy combined walls and information on Z-shaped, U-shaped and HZ sections and their corresponding interlocks. Emphasis is placed on new developments for design applications for deep foundations and waterfront structures within the "state of the art".

Jan 1, 2010

By James A. Nunn

Location Xiaolangdi is located in the Henan province of the People’s Republic of China. The distance between Xiaolangdi and the capital of Henan, Zhengzhou, is about200 km. Xiaolangdi is located on the Yellow River at the end of its big characteristic knee. It can be easily found on the map by locating Luoyang. The closest big city to Xiaolangdi is Luoyang (about 45 km). This city has about1 million inhabitants and is well known also to foreigners for its famous historical past. It has been the capital of China through 10 dynasties in former times. Overview The Xiaolangdi Multipurpose Dam Project is located at the last gorge of the middle reach of the Yellow River. The main purposes of the project are: -flood control, - ice jam control, - sediment control, - irrigation, - water supply, - hydroelectric power generation. The project consists of many structures, these are 10 intake towers, 9 flood &sediment tunnels, 6 power tunnels, 1 underground powerhouse, and 1 zone dearth and rockfill dam with a sloping impervious core, 154m high, with a crest length of 1317m. The powerhouse mainly features 6 turbine and generator units of 300 MW, totalling installed capacity of 1800 MW and annual energy output of5.1 GWH. The total storage capacity of the reservoir is 12.65 billion m³ of which 5.1billion m³ is live storage. Of the Yellow River drainage basin, 694,000 km2 or 92,3percent is located upstream of Xiaolangdi Dam Site. Xiaolangdi is located in a key position for flood and sediment control of the Yellow River. Upon completion, Xiaolangdi Dam and Reservoir will effectively mitigate catastrophic floods, the control level will be increased from the present less than 100-year return period up to 10,000 years. Also, it will reduce severe flooding of the river bed of the lower

Jan 1, 1999

By Ken McIntyre, Trodel Wolf-Dieter

"Sirius Minerals is a UK based fertilizer development company focused on advancing into operation its polyhalite project in North Yorkshire, England. The operation is known as the Woodsmith Mine which has an estimated 2.7 Billion Tonnes of reserves and is currently in the construction phase. DMC Mining Services was selected to carry out the construction of four shafts for the project, a production shaft of 6.75m diameter to a depth of 1594 m, a ventilation shaft of 6.75 m diameter to a depth of 1565 m, and two additional shafts to support the construction of the material transport system (the MTS and Lockwood Beck intermediate) to 360m in depth for servicing the underground conveyor network for transport of product from the mine site to the costal port facilities located at Teasside. This paper will review the status of the project to date and the innovative approaches that DMC is utilizing to ensure a safe and successful shaft sinking project. INTRODUCTION The Woodsmith Mine in North Yorkshire is a Sirius Minerals-owned deep potash and polyhalite mine located near to the hamlet of Sneatonthorpe, Whitby in North Yorkshire, England, approximately 75 km east of York. The area of interest is more than 700 km2. The £3.2 billion project is to develop the Woodsmith Mine to extract polyhalite, and a tunnel system to transport it to a materials handling facility and harbour at Teesside. The site is the world's largest and highest-grade deposit of polyhalite and is expected to produce 20 million tonnes of polyhalite, potash and POLY4 per annum, as well as create over 1,000 direct jobs and many more indirectly. It has the potential to generate over £2 billion of annual exports for the UK. As the project will require mining to be undertaken in the North York Moors National Park, many objections were raised about the mine. Sirius Minerals has gone to great lengths to ensure that the project is sensitive to the local landscape, including: mineshaft head frames that will be positioned below ground to reduce their visual impact; surface buildings will be kept to a minimum; and the entire site will be landscaped and screened by existing woodland to blend in with the surrounding area. The project will also abide by strict environmental limits which govern our activity during the construction phase."

Jan 1, 2019

By Phillips H. R

The action of free rolling disc cutters is well understood, relationships between disc geometry and performance having been established both in the laboratory and under field conditions. However, under severe operational conditions a malfunction of the disc bearing assembly is likely to produce a definite change of cutting action. Collapsed or siezed bearings can even prevent the disc from rolling and thereby create what is equivalent to a drag pick. This paper describes a programme of laboratory experiments using deliberately stalled discs. Their performance under such conditions is contrasted with that for a free rolling disc and also with a drag pick having a ridged front developing into a negative radiused back clearance angle. In conclusion an assessment is made of the influence stalled discs can have on the torque and thrust requirements for a tunnel boring machine.

Jan 1, 1981

By R. V. Ramani, R. Bhaskar

"IntroductionThe behavior of dust clouds in mine atmospheres has been a subject of longstanding interest due to both health and safety reasons. Pioneering studies in Germany and SMRE focussed on ambient dust concentration, principally aimed at determining optimum velocities for effective dilution. A summary of studies related to this area is provided by Hall,(l) Efforts to understand dust deposition from the explosion hazard point of view led to experiments in return airways (2-4) followed by experiments in longwalls.(5) Concerted efforts, either experimental or theoretical, were not made until recently to relate ambient concentration with dust deposition in mines. In 1974 Hwang et a1 (6) developed a computer model to predict dust concentration which considered deposition-concentration relationships. Also, experimental studies involving concurrent dust deposition and ambient concentration were conducted in the U.S. by Courtney et al (7 ) in operating mines. Efforts to relate theory with experimental results have been made by Owen (8) and Hwang et al (6 ) for dust deposition. There has been limited work, however, to determine the application of the theories and assumptions from aerosol sciences for modeling dust flows in mine atmospheres. (9 ) This is the objective of the work currently underway in the Generic Technology Center on Respirable Dust since· 1983 under a project titled, ""Prediction of Ambient Dust Concentration in Mine Atmospheres."" The scope of the project activities include:1. Development of a mathematical model to predict dust deposition and concentration in mine atmospheres.2. Experimental studies on dust transport and deposition in mine airways.3. Comparison of the model results with the experimental data."

Mar 1, 1989

By J-T Zhu, Q-Y Tu, S-L Kong, L Wang, Y-P Cheng, H-Y Liu, Q-L Yang

China is the largest coal-producing country in the world, while the geological conditions of deep coal mining are extremely complicated with high ground stress, high gas pressure and low permeability, which results in the difficulty of gas drainage and aggravation of gas explosion and coal and gas outburst disasters. Co-extraction of coal and gas is an effective method to eliminate coalmine gas disasters and realise the safe exploitation of coal and efficient gas drainage at the same time. This concept is widely accepted by the main coal-producing countries around the world, while the concrete definition of co-extraction is vague and not unified, and there is little accurate theoretical support for co-extraction of coal and gas, which makes it hard to determine efficient gas drainage methods correspondingly according to the features of coal seams in a comprehensive and systematic way. Based on theoretical analysis, laboratory test and field observations, basic thoughts and specific definition of co-extraction of coal and gas were put forward after analysing the occurrence characteristics of coal seams in China. We obtained the mechanism of mining-enhanced permeability and established the corresponding theoretical model, which is the process of fracture network formation through opening recovery of the original fractures and new fractures produced by unloading damage. Based on the core idea of ‘mining-enhanced permeability’, engineering approaches of ‘unloading by boreholes drilling’ for the single coal seam and ‘unloading by protective seam mining’ for the coal seam group were proposed to realise safe and efficient co-extraction of coal and gas. Meanwhile, combined with engineering practice, we put forward the construction principle of coal exploitation and gas drainage system in different coal seam occurrence conditions. The above methods were applied successfully in the Tunlan coalmine in Shanxi Province and the Panyi coalmine in Anhui Province, which had established the ‘underground-surface united’ spatial gas drainage modes, and could ensure safe and efficient co-extraction of coal and gas in the outburst coalmines.CITATION:Cheng, Y-P, Wang, L, Liu, H-Y, Kong, S-L, Yang, Q-L, Zhu, J-T and Tu, Q-Y, 2015. Theory of safe and efficient co-extraction of coal and gas and its applications, in Proceedings The Australian Mine Ventilation Conference, pp 79–92 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By Peter F. Strong, Robert L. Lagace, Alfred G. Emslie

This paper is concerned with the theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a comer. Of prime interest are the nature of the propagation mechanism and the prediction of the radio frequency that propagates with the smallest loss. Our theoretical results are compared with measurements made by Collins Radio Co. This work was conducted as part of the Pittsburgh Mining and Safety Research Center's investigation of new ways to reach and extend two-way communications to the key individuals that are highly mobile within the sections and haulage ways of coal mines.

Jan 1, 1973