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By Joseph A. Newman

THE first trial of longhole drilling of raises began in June 1949 at the Holden mine, Chelan Div., Howe Sound Co. The cost of this raise was about the same as the average cost of raising by normal methods which was sufficiently encouraging to give the method further trial. At Holden, the Noranda method of blasthole drilling is used except that percussion drills have replaced diamond drills for making blastholes in all but certain special situations. Two thirds of these holes are between 40 and 70 ft long.

Jan 10, 1951

By Jack F. B. Silman

Proving up any large, open pit ore deposit by normal exploration drilling under the best of conditions is a noteworthy accomplishment. But, when adverse conditions preclude standard drilling methods, and the same end result is achieved by a relatively new and little known type of drilling, special comment is in order. Three major problems confronted exploration drilling at the Questa molybdenite mine of the Molybdenum Corporation of America-sampling, terrain and time. Surface and underground longhole drilling provided the needed solutions, thus making the greatest single contribution to an exploration and development program that was successful in proving a major, open pit molybdenum deposit.

Jan 5, 1965

By Matthews SM, Gooding JE

N Longhole Open Stope at The Zinc Corporation Mine was developed in an area with large and continuous tension cracks. These cracks resulted fran widespread block subsidence into previously mined areas. The practical problems encountered and their solutions are discussed together with an outline of a new method of stope wall support using large diameter dowels installed sub-parallel to the stope wall.

Jan 1, 1985

By Jackson GS

Since 1983 Cobar Mines Pty Ltd has madea concerted effort to improve the performance of its long hole open stopes, especially in the areas of dilution and fragmentation.This has resulted in modifications to stope design, drilling and blasting practice.

Jan 1, 1985

Longhole open stoping was introduced in the zinc-rich 'B' lode at New Broken Hill Consolidated Limited (NBHC) during 1968. Since then one longitud- inal and a series of transverse longhole open stopes have been developed. The longholes are drilled using Gardner Denver airtrac drilling jumbos and the broken ore is loaded from drawpoints and transported to chutes using Wagner ST5 scoop- trams. The holes were drilled from sill stopes 160 ft apart. The width of an emptied transverse longhole stope was successfully widened by blasting rings of blastholes drilled parallel to the stope wall. Proposed stope and pillar designs for a series of transverse longhole open stopes were assessed using a method of finite element analysis, applied to a longitudinal section through the area. Blastholes have been surveyed for dip and bearing using an Eastman borehole survey camera. The data produced has provided the basis of a study of blast- hole deviation. Deviation of boreholes is considered to be the major cause of the formation of benches in longhole stopes.

Jan 1, 1971

By P Ormsby, T Hewitt

Ore in pillars constitutes a significant proportion of the ore reserve at PasmincoÆs Broken Hill Mine. Many of these pillars are narrow (5 -6 m) and high (16 û 35 m) vertical blocks. High-grade ore has been left between primary horizontal cut and fill stopes. These stopes were mined from the late-1960s until the early-1980s. Fill material is a variety of hydraulically stowed sand, sand-cement, and remnant timber support. Many pillar cut-throughs were made between the old stopes. In order to gain access for the current pillar recovery operations, it has been necessary to develop pillar drill drives through, and adjacent to, the hydraulic filled stopes. Whilst long hole recovery of vertical pillars is not new, some notable successes using innovative ideas have been achieved during 1997. These innovations include:The use of steel mesh reinforcing in shotcrete when mining through, or adjacent to, hydraulic fill. Construction of steel sets to support vent rises and haulage ways encountered in the cut-throughs. The use of ground movement monitoring equipment. Survey lasers with chain droppers and convergence monitors were installed in the 18 Pillar to detect any movement of the pillar block and decrease risk to personnel. The development of a three-dimensional computer model of primary stoping, using Vulcan software, to assist in the design of pillars. Maximisation of recovery using different drilling and firing practices.

Jan 1, 1998

By S. Dereski, G. Chancellor

"INTRODUCTION Barrick Goldstrike underground mine is located in Northern Nevada on the Carlin trend. The underground mine produces approximately 1.5 to 1.8 million tons a year and approximately 400,000 ounces of gold a year. The mine is comprised of two main mining methods, underhand drift and fill and long hole stopeing. The mass blast project stated in 2012 as Value in Use project between Barrick, Southwest Energy and Orica, the goal of this project is to be able to blast an entire drilled stope in one blasting event instead of taking multiple blasts. This will improve productivity by eliminating intermediate blasts, reducing additional blast time, eliminate drill hole cleaning due to the previous blast. Project implantation started in the fourth quarter of 2013 and mass blasting has been common practice throughout all of 2014. STOPPING PRACTICE AT GOLDSTRIKE BEFORE MASS BLAST PROJECT The production from the Goldstrike mine is approximately 70% from stopes. The timely completion of all stoping blocks is imperative to maintaining the plan, delays in the execution of any particular block can have detrimental ripple down effects as neighbouring stoping blocks become delayed. Before the implementation of this project the standard practice for Goldstrike was to: 1. Drill the entire stope 2. Blast a bottom shot, normally between 10 feet and 20 feet off the bottom of the slot rings. This would be mucked out before the next shot 3. Blast a pull through shot, this included the raise and one or two production rings. Again mucking this out before the next shot 4. Blast production rings, one or two more blasts depending on stope size. In most cases between each of these blasts the holes in the other rings of the stope would have to be cleaned. This meant either cleaning manually using air and water, or mechanically cleaning with a bench drill. In many cases this resulted in delays in completing the stoping block."

Jan 1, 2015

By H. Bogart

The Golden Sunlight Underground Mine located near Whitehall, Montana was portalled from the bottom of the existing Golden Sunlight Pit in July 2002. Gold was mined by sublevel stoping in the larger ore zones and longhole back stoping in the narrower ore zones. The stopes varied from 30 feet to 100 feet in width, extended up to 200 feet in height, and were completely unsupported. Underground production averaged 1,500 tons per day with a staff of35 people. The mine operated with a break-even cut-off grade of0.080 ounces per ton.

Jan 1, 2004

By Charles B. Henderson

DESPITE the loss, by enemy conquest, of a high percentage of our normal sources of supply for tin, the position of this important metal is easier today than that of rubber and a long list of other strategic materials, many of which are produced in this country. Actually, there is no shortage of tin for essential war purposes, owing to a strict control of its use, to increasing considerably the amount of secondary tin available, and to the foresight of the Government in authorizing the Reconstruction Finance Corp., as early as June, 1940, to acquire and produce certain critical and strategic materials of which tin was one of the most important. The construction of the Longhorn Smelter on the Gulf Coast in Texas is an important part of this program.

Jan 1, 1943

Hoisting ropes are constructed of wires and strands positioned helically around the axis. This helical positioning causes that, in the rope loaded at the end with the weight Q, the longitudinal displacement u, axial force P, torsional displacement v and constant torsional moment M are generated. More over, the proper weight of the rope q gives the force acting along the axis of the rope. This force changes its value from 0 at the bottom to qL at the top. This force gives, along its length, a variable torsional moment making the rope rotate. During the movement of the conveyance downwards the falling part of the rope rotates, which makes it untwist on the section up to the half-depth of the shaft and twist on the other half-depth. As the result, the twisting lay of the rope changes increasing in the upward direction and decreasing downwards. The angle of twist of the strands changes in an apposite way. When moving upwards, the uplifted rope does not twist and retains its state of deformation up to the moment when it passes over the pulley. Next, the cycle of untwisting and twisting repeats during the movement of the other conveyance downwards. This phenomenon is known from mining practice. It was also analysed, in the works of Glushko (1966) and Popowicz (1963).

Jan 1, 1995

By B. B. Broms

The high transverse tensile stresses that develop in precast concrete piles during driving have been investigated experimentally from pile load tests and theoretically using the finite element method (FEM). These tensile stresses can be high enough to cause longitudinal splitting of the piles just below the pile cap. Test data and FEM indicated that the maximum transverse tensile stress will increase with increasing thickness of the cover. The maximum tensile stress can be high especially if the pile is eccentrically loaded. The results from the experimental investigation and from FEM are described in the paper as well as a simplified method based on the stress distribution in a concrete cylinder at an indirect tension test.

Jan 1, 2010

By Stein Wennberg, Snorre Tessem

INTRODUCTION The mine is situated in the middle of Norway 150 km north of the town Trondheim. The iron ore deposits were discovered in 1906 and have been continuously mined since. The first owner was A/S Nordiske Grubekompagni. In 1912 Fosdalens Bergverks-Aktieselskab was established; since World War II it has been a wholly state-owned company. The location is advantageous, with mining facilities, ore dressing plant and stockpile situated near the northern head of the Trondheimsf jord. The iron ore always occurs in Ordovician lavas and sediments, now altered to greenschists, keratophyres and limestone. The ore bearing zone is 150 km long. The deposits consist of two parallel linear ore bodies lying one above the other in the same stratigraphic horizon which dips 70' to the south. The upper body is 50-100 m high, the lower one 250 m high, while the distance between the two bodies in the East mine varies between 20 and 60 m. The ore width varies between 5 and 8 m. The ore bodies strike WSW and plunge between 10' and 15" in this direction. To date continuous ore has either been worked or opened up along a total strike length of 10 km. Until 1969 all ore was mined in the western part of the deposit called the Western mine. In the spring of 1969 production started in a new mine, the Eastern mine. The ore bodies in this new mine are geologically the same as in the old mine, but they have been displaced 700 m downwards along a major fault in the Fosdalen valley.

Jan 1, 1981

By Robert Semrad, J. Colin Anderson

INTRODUCTION Sulphur is a mineral which accounts for 0.05% of the earth's crust and may be found either in its elemental state or as a compound. References to sulphur production and consumption are found in early antiquity and international trade of sulphur from volcanic deposits in Sicily began in the 1880's. The supply of sulphur consists of two components: the first is production, and the second is inventory. HISTORICAL SUPPLY Production World sulphur production in 1984 was approximately 53.5 million metric tons, compared to the 1970 level of 42 million metric tons. Of this 11.5 million metric tons production increase, brimstone accounted for close to 90%. Production distribution in 1984 was 62% brimstone, 21% pyrites and 17% other forms, while in 1970 it was 55%, 28% and 17%, respectively. Brimstone Production is derived either from mining operations (Frasch, underground melting and native refined) or as a by-product from hydrocarbons. World production in 1984 exceeded 33 million metric tons, up approximately 10 million metric tons from the 1970 level. This increase was uniformly distributed throughout the world as shown in Table A.

Jan 1, 1986

By D. G. Krige

The problem of a realistic investment analysis for a new mining venture that sells its products on the international metal markets IS studied against the background factors, firstly, of different inflation rates between the countries hosting the mines and those. hosting the metal markets; and, secondly, of the changing pattern of currency exchange rates between such countries. The purchasing-power parity theory is used to establish a pattern of relationship between these two factors, and to develop a more logical approach to the long-term forecasting of metal prices in the currency of the country in which the mine is situated.

Jan 1, 1979

By P Lever, D Hainsworth, H Gurgenci

The ACARP Landmark initiative has created the opportunity to advance the level of automation in the coal industry by first focusing on the core production area of longwall mining. A Landmark Longwall Automation project was commenced in July 2001. The major outcome of automation using on-face observation has been divided into ten outcome areas that have been fully scoped for a three-year initial project life. A major facilitating technology has been the implementation inertial navigation system (INS) technology that can map the shearer position in 3D. A focus of the project is to deliver a system that is at least as productive as the current most productive manually controlled longwall face.

Jan 1, 2002

By E. O. T. Simpson

"IntroductionAS COMPARED with coal mines in the United States, and even with some of those in eastern Canada, the coal mines of western Canada, generally speaking, :have made little progress toward mechanization at the working faces. So far as Vancouver island is concerned, there are three main reasons for this : ( 1 ) in some areas, conditions• easy for hand-loading but unsuitable for mechanical loading make high outputs per man •possible by the former method; (2) faulting of the coal seams in ..some areas precludes long-term planning and the introduction and efficient use of expensive equipment; (3) thinness •and other characteristics of the seams in many areas favour hand-loading.No. 8 MINENo. 8 mine of Canadian Collieries (Dunsmuir), Limited, is located in the Cumberland sub-area of the Comox coalfield on Vancouver island about 90 miles west-northwest of Vancouver. The geological structure of this coalfield has been described by J. D. McKenzie. The seams occur in the Comox formation, a subdivision of the Upper Cretaceous Nanaimo Group. The formation is of near-shore origin and was laid down on an irregular surface of' older rocks. The irregular generally have a northeasterly dip, modified by gentile folds and by a •few large, and a number of smaller, faults.Four seams have been worked in the Cumberland area and all vary in thickness and in the amount and number of interstratified bone and rock •bands."

Jan 1, 1953

By Yu H, Wan B

40 percent of the coal reserves and 40 percent of the ouput of coal in China is of thick coal seams. The sub-level caving in Yangguan has evolved together with the hydraulic supports, to provide recovery rates today of 80 to 85 percent, waste ratios less than 10 percent and daily outputs exceeding 7,000 tonnes. Matching of rate of shearing bottom coal to caving of top coal is most important to achieve "simultaneous" operations. Spontaneous combustion in the goat, gas, including in the goal, and dust, are particular safety hazards which are combatted with various stringent measures.

Jan 1, 1991

By Carthew J

For more than 30 years shearer loaders have been the most important winning machines for,longwall mining. While the machines of the first generation had a driving power of only 100 or so kW, the present day shearer loaders may be powered by more than 1000 kW. Daily outputs of 24000 tonnes have now been reached, but this still does not set a limit. If the deposit conditions allow, further increases are possible. This requires the optimum coordination of all system components. For this paper the use of coal plows has been of little import as plows have found no favour, and nor are they likely to do so in today's economics in Australian coal mining.

Jan 1, 1988

Identify specific sources and the relative levels of contribution of various components of longwall shearer operations to the total airborne respirable dust generated during mining. Approach A research investigation was conducted in two phases by the Bureau of Mines at five mine sites to identify specific dust sources and their relative importance during long-wall shearing operations. During phase I of the project the specific longwall mining elements identified for evaluation were: cutting, sumping, tramming, conveying, and moving roof supports. During phase II of the project, two dust sources were evaluated: clearance ring cutters cutting in six-inch web width increments, and loading operations. Investigation Results As a result of dust measurements, the gage cutters were determined to be the major dust-generating source on the shearer. These cutters, at 6-inch web depth, produce three times as much dust per unit volume as is produced at 30 inches full web depth. The following list of averaged values for the mines tested shows that shearer cutting generated averaged dust levels four times as high as those generated by conveying, and approximately five times as high as those generated in moving roof supports.

Jan 1, 1984

By Thomas Collier

MR. PRESIDENT AND CO-WORKERS IN THE COAL INDUSTRY: I was requested by our president to prepare a paper on Longwall Coal Mining, to be read before this honorable organization. There are three general systems of Longwall, Longwall advancing and Longwall retreating, and the Nottingham system which is worked in England and South Wales. In Fremont county, where I am employed, the Colorado Fuel and Iron Company are working their mines on the advancing system. The face is started generally from the bottom of the shaft or other mine opening, or, at the outside of the pillar left to support the shaft or slope-bottom and advances toward the boundary of coal area. As the roads in this system are maintained by pack walls, it is sometimes called gob-roads system, and by these means the mine is opened up rapidly and consequently early returns are secured from the capital invested. By this method, there is no expense for narrow work, and a minimum amount of timbering of the roads is required. Now what I call ideal Longwall work is where there is about eight inches of dirt mining-and four and one-half feet of coal, .and when the entries and rooms will gob themselves, so that there will be no rock or dirt to haul out to the surface. But this is not the case in the mine I am in charge of. The entries and rooms will not gob themselves, therefor we have to haul the rock and dirt to the surface, which runs up the cost of production. Now the ideal roof in Longwall is composed of tough elastic and pliable strata that yield gradually by bending when the coal is removed, and throwing a sufficient weight or roof pressure on the coal face to break the coal when the same has been mined or undercut. Timbering should be done systematically, the coal well spragged before the miner starts to undermine the coal. Cogs or cribs are alright in their place, but I am not a believer in crib in Longwall working because they are too strong for the roof and do not leave the roof to squeeze .down gradually and break the roof around the crib. Longwall work requires particular skill on the part of the miner, and a familiarity with the conditions affecting room and pillar work, and a good room and pillar mail may not be successful in. Longwall work. A good Longwall miner realizes more than any one else the importance of being regularly at his place every working day. A day lost causes his place to fall behind the others which makes his work harder, and his daily output is further reduced by the amount of small coal that is liable to result from the excessive pressure where the face falls behind. The bad results are also felt by the miner working on each side of such place, as the roof pressure is often insufficient and the coal does not break as well as when the face is kept in a uniform line.

Jan 1, 1921