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By Jack Parker

"The original design of mine openings and pillars at White Pine was based upon traditional assumptions; i.e., that the principal load is due to the weight of overburden, and that horizontal stresses are equal to one-. third of the vertical.Beginning January, 1964, borehole deformation measurements confirmed suspicions that the principal stress is horizontal and several times greater than the vertical.Vertical stress appears to be directly related to depth, but lateral stresses vary considerably in direction and magnitude. The direction of major principal stress lies parallel to the bedding and is apparently parallel to tension joints. Lateral stresses appear to originate from an igneous intrusive.Mining induces stresses which add to the primitive stresses, in some areas precipitating failure. In this paper, rock failures are illustrated, methods of measurement and typical results are given, and measures to counter or utilize the lateral stresses are described."

Jan 1, 1966

By M. L. Trépanier

"Engineering and technical services are supplied by the Engineering Department, located at Thetford Mines, Quebec, approximately 60 miles southwest of Quebec City. The department serves the three operating mines in the Thetford area, the Asbestos Hill mine at Putuniq, Nouveau Quebec, and the Nordenham plant at Nordenham, West Germany. The Engineering Department is responsible for supplying the following services. 1. Administration and coordination of capital projects. 2. Engineering, design and drafting services for in-plant changes or improvements. 3. Preparation of geological plans for mine planning and ore reserves determinations. 4. Short-, medium- and long-term mining plans. 5. Rock mechanics studies and monitoring. 6. Grade control monitoring. 7. Environmental control engineering and construction. Details of the organization and services rendered will be the basis of the paper."

Jan 1, 1976

By C. A. D' Odorico

The zinc pressure leaching (ZPL) plant at Teck Cominco's Trail Operations was started up in 1981 and represented the world's first commercialization of the technology. From the outset, the process was designed to operate using iron-rich Sullivan Mine zinc concentrate. When the Sullivan Mine reached the end of its life in 2002, the ZPL plant underwent a significant process change with the treatment of 100% Red Dog zinc concentrate. Through careful improvements to existing plant processes, controlled changes to plant operating parameters and a rapid adjustment to the modified process by operations personnel, the plant has been successfully converted to processing a feed of 100% Red Dog zinc concentrate. This paper discusses the challenges faced during the conversion and describes the modifications to plant operating procedures, as well as changes to plant processes.

Jan 1, 2004

By R. T. McAndrew

Introduction Drinnan is situated in the Prairie Creek coal area in the Foothills belt of Alberta. It lies on the main line of the Canadian National railway from Edmonton to Jasper. The exact location is shown on the map (Figure I). Interest in the field was aroused by several circumstances: Its proximity to Brule and Pocahontas on the southwest and to Coal-spur on the southeast led to the belief that coal might be economically produced here. There was already at Hinton a 3 ft. 9 in. coal seam being mined by Seabolt. The coal was of very good grade, being black and shiny in appearance with well defined cleavage and a heat value of 12,000 B. t.u. Outcrops of coal had also been noticed on the north side of the Athabaska river and Fish creek. These facts led the Jasper Coal Company to investigate the field. This Company considered taking over the Seabolt property at Hinton, but, owing to the size of the seam, this plan was abandoned and prospecting by diamond drills and test pits was started two years ago in the district east of Hinton. After prospecting had been completed, the most favourable district was found to be in township 51, ranges 24 and 25, west of the 5th meridian. The Company's lease includes all or parts of sections 18, 19, 20, and 28 in range 24, and sections 10, 11, 12, 13, and 14 in range 25. The approximate boundaries of the property are the Canadian National railway on the north, Happy creek on the west, and Cache Percotte creek on the east. The lease comprises 3,100 acres, and the total amount of coal in sight is estimated at 100,000,000 tons.

Jan 1, 1931

By N. Melnyk

"FOREWORDThis paper provides a unique description of a method devised for mining a very thick steeply dipping seam of soft gassy coal which was prone to spontaneous combustion. The editors con¬sider that the information in this paper should be important to those who may have to consider mining such seams again at some time in the future and therefore believe that the paper warrants reprinting in the present volume. The author was ask¬ed to review the paper and to add any additional relevant in¬formation. He provided the accompanying footnote, only a month before his death on April 22, 1982.IntroductionIn the past, the Cadomin Coal Company has opened four mines, all in the same coal seam or its folds. Three of these were opened from river level by horizontal entries or rock tunnels. and the fourth, the present working mine, by vertical shafts. This paper deals largely with some operating phases of this fourth mine, with which the writer has been associated.The seam worked here is a thick, steep, bituminous seam, and the writer feels there is a paucity of published data on the mining of such seams. Possible reasons for this are that such seams do not lend themselves to intensive development or mining, there is little chance to mechanize because of the extreme pitch, and operations are fraught with many problems. In addition the present operations in this particular' seam are being carried on at a level below the former workings, introducing new problems, not encountered on the upper level.Coal will, without question, long continue to be an impor¬tant factor in the national economy, and some of the best coal is to be found in thick, steep seams. But with the exhaustion of the easily-mined coal near the outcrops, future coal will have to come more and more from lower levels. At Cadomin there is still considerable coal on the second level, below the old river-workings, and there is a possibility that, in the future, still lower levels will be worked. It is the purpose of this paper to indicate some phases of such lower-level operations and to invite discussion."

Jan 1, 1985

By J. Gray, J. Peck

As the turn of the century approaches, traditional open pit mining methodologies and processes are being modified through the introduction and use of new technologies. As in other industries, the personal computer is dramatically changing the traditionally conservative mining industry by allowing mines of varying size and capacity to increase their productivity and efficiency through the use of easy to use, office software. Computer-based monitoring and control systems are also being used more frequently to measure and optimize, in real-time, the performances of operating equipment. When communicated to an end-user, this information can provide accurate and timely answers to questions of how much, where, when, and by whom. This capability forms the foundation of a more comprehensive, proactive management and planning facility where, ultimately, information acquired from the producing equipment will be used to optimize and control machine and human activities. As these technologies mature and become essential tools in a mine, they will eventually serve as the basis for more robotic and autonomous mining operations.

Jan 1, 1999

By A. G. Ballachey

Introduction This paper will describe the mining plant and underground operations at Quemont. Details of geology and milling are beyond its scope. Papers on these subjects will be prepared and presented separately. A detailed account of the exploration and development, 1944 to 1947, has been given by W. L. Brown (1). Location The mining concessions of Quemont Mining Corporation, Limited, are in Rouyn township, Rouyn-Noranda county, northwestern Quebec. These concessions total about 640 acres in area. They lie within the limits of the City of Noranda, contiguous to, and directly north of, the Horne mine of Noranda Mines, Limited. A large area in the southern part of the property is covered by the north arm of Osisko lake. Production The present operating rate is about 2,100 tons per day. Three flotation concentrates are produced: copper, containing a large proportion of the gold and silver in the ore; zinc; and pyrite, which carries an appreciable additional proportion of gold. The copper and zinc concentrates are shipped to smelters as produced. The pyrite concentrate is cyanided to recover additional gold, after which it is filtered, dried, and shipped for the manufacture of sulphuric acid. The principal revenue metals are copper, gold, and zinc. Silver and pyrite are important by-products.

Jan 1, 1952

By A. Boehm

"For recycling LD slag into the steel making process, the phosphorous containing calcium silcate phases have to be removed from iron oxide phases. One possible technical solution could be magnetic separation in a wide range of susceptibilities from ferromagnetic to paramagnetic. To check the feasibility of magnetic separation the distribution of the magnetic susceptibility in size classes as well as the liberation of the phosphorous containing phase were evaluated by a new method combining two dimensional physical property analysis with QEMSCAN analysis. The particle size classes of energy controlled comminution products were subdivided into fractions of defined magnetic susceptibility using a hand magnet of well known field properties (pick up method). On the one hand the susceptibility classes were wet assayed on the other hand analyzed by QEMSCAN followed by data evaluation using iDiscover 5.3.1(FEI), which was adapted to the data structure of two physical properties (size and magnetic mass susceptibility). The results allow the comparison of mass based (3D) cumulative distribution of grades from the wet assays with the area based (2D) distribution from QEMSCAN analysis, in order to control a systematic (size dependent) stereological error for this special type of material. As the physical separation property forms a crucial parameter the results from the liberation analysis by QEMSCAN can be interpreted more profound with respect to an expectable separation result. Once the various mineral compositions of the particles are assigned to the physical properties the Henry Reinhardt chart serves to predict the best possible separation result and thus the feasibility of a separation technique.INTRODUCTIONThe two Austrian steel plants operated by voestalpine AG produce about 650,000 t (voestalpine 2014) of LD slag in the course of steel production from pig iron according to the basic oxygen process blowing oxygen in the converter by an oxygen lance. The process is also known as the Linz Donawitz (LD) steelmaking process. By the addition of lime (CaO), carbon, phosphorus, silica, manganese and sulfur, which are present in the molten pig iron, shall be oxidized and bound in the slag either as oxide or silicate phases, or leave the slag in the gaseous phase (CO). The average chemical composition of the investigated LD slag is given in table 1."

Jan 1, 2016

By L. Li

To accommodate the large payloads and harsh operating conditions associated with heavy vehicles in the mining industry, off-the-road (OTR) tires are typically used with heavy mining vehicles. These tires have increased abrasion and wear resistance due to their thicker tread, sidewall and bead thicknesses. Given these features, OTR tires are much stiffer than conventional passenger vehicle tires and cannot be mounted to a single-piece rim without damaging the structural integrity of the tire during the mounting process. Therefore, multi-piece wheels are used with OTR tires to facilitate mounting. While these assemblies are necessary, several instances of their failure have been reported to result in injuries or fatalities within the mining workplace. Many of these failures were specifically reported to be caused by the disengagement of the wheel lock ring - a component used to securely engage the assembly during operation. In this study, a threaded-connection locking mechanism has been proposed in place of the traditional lock ring design. The performance of this threaded-connection was numerically evaluated in a pull-out test against a conventional five-piece wheel assembly. The pull-out test was devised as a means of quantifying the engagement ability of each wheel?s locking mechanism. A high degree of modelling accuracy was maintained throughout the analysis by validating the vertical and horizontal static loaddeflection behaviour of the rim model of the five-piece wheel assembly against experimental data. Through validation, the model data were found to be within 10.5 and 4.80 %, for vertical and lateral loaddeflection behaviour, respectively. Results from the pull-out analysis found that the threaded-connection demonstrated a 113 % increase in the force required for disengagement to occur relative to the conventional five-piece design - a force of 9,550 kN in total.

Aug 1, 2013

By Francis Breton, Daniel Larouche, Pierre Heugue, Rémi Martinez

"Nowadays, in order to fit environmental restrictions, automotive markets are demanding cast aluminum alloys working at high temperature (180–300°C). New generations of alloys are required for higher strength components in engine downsizing or start-stop systems which lead to higher loading and higher specific power and stretch current materials to their limits. Recently, transition metals, such as zirconium and vanadium, have been added as alloying elements into an AlSi7Cu3.5Mg0.1 alloy to improve physical, mechanical, thermodynamic properties with the aim of increasing service life of parts. In such alloys, the best mechanical properties are associated with the formation of precipitates through an optimum heat treatment sequence, including: solutionizing, quenching and artificial aging. This study is focused on the modified AlSi7Cu3.5Mg0.1 cast alloy with Mn, Zr and V additions for high temperature application. The characterization of the cast alloy in this study, firstly, helps to evaluate and understand its performance both chemically and structurally according to their physical state: as-cast or as-quenched. Comparison of precipitation kinetics between a binary Al-3.5%wt.Cu alloy and the AlSi7Cu3.5Mg0.1 (Mn, Zr, V) alloy has been characterized by differential scanning calorimetry, TEM observations and micro-hardness testing. The Kissinger analysis was applied to extract activation energies from non-isothermal DSC runs conducted at different stationary heating rates. The study focuses on the impact of the chemical composition such as Si content on the kinetics parameters.INTRODUCTION Pure metal Aluminum shows poor mechanical properties and its malleability is high, that is why alloying elements are added to the mixture before casting to improve physical, mechanical and thermodynamic properties (Javidani, 2015); such as Silicon (Si) for casting properties (castability, cold crack capability, wear resistance, shrinkage behavior), Magnesium (Mg) and Copper (Cu) to generate precipitation hardening systems. Aluminum hypoeutectic alloys (<12% Silicon) with Cu, Mg additions used in the automotive industry for manufacturing mechanical parts (Larouche & Javidani, 2014) are mostly subject, after casting, to precipitation hardening heat treatment (Mohamed & Samuel, 2012) according to specifications and associated standards. The best mechanical properties are associated with the formation of precipitates through an optimum heat treatment sequence, generally including: solutionizing, water quenching and artificial aging (Manente & Timelli, 2011). Hypoeutectic aluminum-copper alloy with amount of Cu around 1 to 4.5wt% is an elementary case for precipitation in heat treatable aluminum alloys. Researchers essentially focused their work on the full precipitation sequence of binary Al-Cu alloy during aging which is presented below."

Jan 1, 2018

By H. C. Gunnings, C. O. Swanson

"The Sullivan mine; at Kimberley in southeastern British Columbia; is the largest silver-lead-zinc mine in the Empire and one of the largest in the world.The original discovery was made in 1892 by four prospectors. Until 1899, when the branch line of the Canadian Pacific railway from Cranbrook to Kimberley was completed, little work was done on the property. In 1900, systematic development was started, and during the next 3 years 5,000 tons of ore was shipped to the smelters at Nelson and Trail. By 1903, some 300,000 tons of ore was developed, and a smelter was started at Marysville, about 5 miles from the mine. However, this smelter closed down in 1907 because of metallurgical difficulties after treating 75,000 tons, and the property came under the control of the American Smelting and Refining Company. An option on the property was taken in 1909 by the Consolidated Mining and Smelting Company of Canada, who exercised their option in the following year. During the next 5 years by selective mining and sorting 188,000 tons of high-grade ore was produced and shipped to Trail. This tonnage came from the upper levels, about 4,600 to 4,800 feet in elevation. At the same time, deep drilling down to the 3,900-foot level showed the presence of an immense body of complex ore. In 1915, the main adit-the 3,900-foot level-was started, and by 1919 this had been driven a distance of 2 miles to develop the ore above this level. Meanwhile, progress was being made in overcoming the milling problems. An interesting account of this work was written by the staff ( 4). In 1923, the first unit of the present concentrator was erected, with a capacity of 2,500 tons a day, and thereafter the rate of production increased rapidly. In 1934 it was around 8,000 tons a day, and to date a total of about 30,000,000 tons of ore has been sent to the mill. In recent years, a considerable part of the production has come from levels between the 3,900-and 3,350-foot, which were opened by an internal incline shaft started in, 1930. In 1942, tin was added to the products separated at the concentrator."

Jan 1, 1954

By John C. Leighton, C. O. Brawner, Doug Stewart

"Despite the availability of established, sophisticated methods for planning and designing stable slopes in rock, comparatively little attention is usually paid to the problems of carrying out the excavation. Blasting should be carefully planned to obtain optimum fragmentation as well as steep, stable working and final pit walls. The principal difficulty facing a blast designer is the lack of prior information about the many critical blasting characteristics of the rock mass. The common practise of trial-and-error lasting will eventually lead to a suitable program, but must be repeated time after time in variable geology. This frequently results in many blast-damaged slopes. Recent research indicates that monitoring drill performance will yield a Rock Quality Index which correlates to a Powder Factor value. The drilling can provide a continual supply of data, reflecting changes in the rock mass which enables the selection of an economical powder factor.IntroductionWhen planning to excavate a large-scale rock slope, engineer s will generally spend considerable effort to produce a safe, feasible and economical design. Much time will usually be spent on the field map ping, &apos;structural geologic studies, surface and subsurface hydrology, determination of strengths and effective friction angles of discontinuities, and finally checking stability with the aid of mathematical and analytical models. If the rock cut is to be along a transportation corridor, the prime justification for this time and effort is to produce a clean, stable slope which will be safe for those travelling or working beneath it. For the walls of an open-pit mine, there is the additional economic incentive to maintain the steepest stable slope angle for the minimum stripping ratio (Stewart and Kennedy)."

Jan 1, 1982

By E. Esmaeilzadeh

There arc 8 primary ball mills in the concentrator plant and their task is material crushing. At the time of balls charge to mills, a lot of noise is produced. This noise would affect all grinding areas. The aim of this research was a reduction about 16 dB at source sound power level (SWL was 129.1 dB). With considering two noise control principles, noise producer sources and propagation paths were specified. For removing and reducing of noise producer sources, rubbers with a thickness of 5-20 mm were used on the all inside surfaces of charge box, ball transferring box and exit canal. For increasing transmission loss and damping coefficient of charge box body, rubber with thickness of 1 cm at outside surface of box was used. For reduction of noise propagation a secondary metal cover was designed and made. This cover includes two parts and was set around the charge box. Glass wool (75 kg/m3) with 10 cm thickness was used as acoustical absorbent between free space of two body&apos;s layers and from secondary cover side. The of the rest space was left empty. After installing of secondary cover on the ball charge box no.4, SWL showed a reduction about 16 dB. For studying of control system effect on noise reduction at points far from of charge place, measuring results at these points showed the maximum reduction 12.1 dB and the minimum 11.8 dB.

Jan 1, 2007

By Lex L. Udy

External-detonation-generated plasmas, highly ionized zones of reacting material ejected from the surface of detonating explosive charges, are shown to be the cause of channel desensitization, i.e., the self-quenching of a detonating explosive column loaded in a borehole with an air annulus between the explosive and the borehole wall. The effects of this phenomenon on several explosive compositions and types are demonstrated and discussed. The explosives tested include aluminum-sensitized and explosive-sensitized slurries, ANFO, liquid explosives and dynamites. Various techniques are described that can be used to reduce or eliminate the plasma effect.

Jan 1, 1979

By The Staff

Introduction In this paper it is proposed to discuss briefly some of the problems confronting the management of a gold mine in choosing a method of milling to recover the gold from various classes of ore. In order to simplify the discussion, the more common types of gold ores are classified from a metallurgical point of view as follows: Class 1?A: Free-milling ores which require only relatively coarse crushing. B: Free-milling ores which require finer grinding to release the gold. Class 2?A: Gold ores which contain the gold partly in the flee state and partly associated with a small amount of iron sulphide, and which do not require fine grinding. B: Gold ores similar to 2A, but which require fine grinding. Class 3?A: Gold ores containing copper in quantities insufficient to interfere to a serious extent with cyanidation. Gold ores containing copper in sufficient quantity to interfere with cyanidation but in which a large proportion of the gold is in the free state, the remainder being chiefly associated with the copper mineral, chalcopyrite. Gold ores containing copper and other sulphides, such as pyrite, etc., in which the gold is principally associated with these sulphides.

Jan 1, 1931

By H. C. Boydell

Those connected with mining, prospecting, or mining geology in northern Ontario are familiar with the fact that it is a comparatively unusual thing to have assayed a sample for which the assay report shows no gold. Values of 20 cents to 80 cents per ton, or even higher, are extremely common. Whilst contamination by fluxes, faulty manipulation, or a desire, on the part of the assayer, to sugar-coat the pill for the client, may account for 20 to 40 cent values at times, it is un1ikely that they would a1ways do so. Exonerating the assayer from being necessarily at fault, what can be the cause of such a widespread distribution of gold (and silver) in minute quantities- of a dissemination .that, in the writer&apos;s experience, and so far as he is? aware, is not met with on a simi1ar scale in other parts of the world? Explanations that suggest themselves are, that the dissemination is due: 1. To a very widespread auriferous minera1ization, post-dating (epigenetic) the formation of the rocks in which it occurs. 2. To a general syngenetic distribution of gold in the volcanic rocks of Keewatin age that form so large a part of the sections of northern Ontario that have been prospected.

Jan 1, 1928

By S. Goodman

Successful exploration for and exploitation of a mineral deposit requires an accurate understanding of the deposit architecture in 3D, and of the development of the mineralizing system through time, which requires a thorough comprehension of the structural framework of the deposit. The integration of geological, geophysical and geochemical datasets to arrive at a 4D structural framework is well-established and has been successfully applied by SRK Consulting in projects from deposit to regional scale. In some cases, we can go beyond this, applying the SEEBASETM technique, which utilizes a ?bottom-up? approach to basin analysis. SRK?s approach primarily relies on the interpretation of magnetic and gravity data, calibrated with many other datasets including mapped geology, topography, event histories, wells/drillholes and seismic data. The SEEBASETM model is a culmination of this data integration and is produced through an iterative process of structural interpretation and geophysical modeling, where an interpretation of basement composition and 4D structure is used to constrain depth-to-basement geophysical modeling, and the modeled depths are then used in conjunction with the structural interpretation to constrain contouring of the basement topography. The result is a rigorously calibrated, 3D view of the basement surface, which can be used to understand the basement and basin architecture, and thus serves as a predictive exploration model. This technique, which was developed for use in the petroleum industry, is now finding success as a predictive tool in mineral exploration.

May 1, 2003

By A. Rahmati

Geological and geo-statistical modeling of the ore deposits play a prominent role in resource and reserve estimation for geo-statistical evaluations. Sheytoor iron deposit is located in the Bafq iron ore district (Central Iran) and in the south-east of the Esfordi 1:100000 sheet. According to the geological data, limestones and dolomitic limestones are situated in the north and central parts of the area, on the other hand, iron ore outcrops are observable in the center, south-west and south-east of the studied area. Meanwhile this ore deposit represents a sulfide one. Based on the boreholes data, geological and geostatistical models of the high and low grade iron mineralization zones were generated by Rockworks v.15 software. The IDW method was selected and employed for processing the collected data and a good adaptation between the results was revealed. The distribution model of Fe concentration displayed a relatively high grade Fe in the center, south and south-east parts of the area. Furthermore, this model illustrated a relatively high grade S and P in some parts of the center, north and south-east of the area. The Fe concentration, in the high grade mineralization zone, was between 45 and 61.5%. In addition, in the low grade mineralization zone, it was between 3.64 and 57.64%. Moreover, in the intrusive granites, the Fe concentration was between 30 and 48.73%. Due to the significant amount of the sulfur in the deposit model, most of Fe-bearing minerals are pyrite, so it is recommended an evaluation on Cu-bearing minerals and their related elements in the area to get done. Additionally, there are too much Fe values in granitic zones which could be caused by possible measurement errors and the geological classification of the area. Therefore, it should be done more carefully.

Aug 1, 2013

By G. A. Young

THE Geological Survey was created in 1842 to aid the development of Canada&apos;s mineral resources. Although the institution has been in existence for nearly 100 years and has accomplished an immense amount of work, the need for its services remains as great as ever and, indeed, it is difficult to imagine a time when the country will no longer require a Geological Survey. This is so because of the tremendous effort required to make an adequate geological examination of so large an area as is embraced by Canada and partly because what today may seem an adequate geological examination proves, later on, to be inadequate. The ultimate objective of the Geological Survey is to complete the study of all phases of the geology of Canada, that is, to determine how and when the physical features originated, how and when the soils and other unconsolidated deposits were formed, and how and when the solid rocks and associated deposits were produced and assumed their present conditions. When the study has been completed, any only then, will it be possible to make a reliable estimate of the country&apos;s mineral resources. This appraisal embraces more than determining the value of already discovered deposits: it also involves attempting to establish what kinds of undiscovered deposits may be present and where they may occur. The estimating of the potential mineral wealth can be clone only after the geology of the country is known. Not until then will it be possible to forecast what types of valued deposits may occur in a district and what types will almost certainly be lacking. A thorough knowledge of the geology of the country is desirable not only to permit estimating the potential mineral resources but also as an aid in locating and developing mineral deposits whether these are of the nature of a bed of limestone, a seam of coal, a reservoir of petroleum, a vein, an irregular body of sulphides, or any other type of deposit.

Jan 1, 1940

By H. C. M. Gordon

IT is essential to the success of any mining op::ration that the roadways through which the material wrought and ocher materials and supplies are to be transported should be kept in such condition that this transportation cart be effected rapidly and without difficulty. The longer the roadway and the greater the tonnage to be taken over it, the more necessary it becomes chat the construction and maintenance of the road be such chat traffic delays can be reduced co a minimum. le is proposed co deal with the development and construction of roadways serving longwall operations and, since a recreating system of longwall is worked, as a rule, only where roadways driven in the solid coal can be readily maintained, the discussion will be confined co advancing longwall roads which are driven through areas from which the coal seam has been totally extracted. In order to construct a roadway through extracted ground in such a manner that it will remain in a state of reasonably good repair without undue maintenance, it is necessary chat everything possible be done to bring the overlying strata co a state of equilibrium as quickly as this can be effected, and the operations should be so planned that future workings will not disturb the equilibrium so set up more than can be avoided. Obviously, the readiest way to obtain a stable roadway is to develop it by tunnelling through a settled waste. However, this cannot always be done, as some of the roadways must be developed and constructed as the walls progress, but level or lateral cut-offs can be constructed in this manner. Main-slope roads can be developed in a similar manner after the coal has been extracted and a waste formed for at !east five hundred feet on either side of the line of the permanent roadway from temporary subsidiary roads developed for this purpose along one or other of the flanks of the waste to be formed. This interval must be obtained in order chat the lacer extraction of the seam will not set up movements in the waste immediately overlying or adjacent to the constructed roadway, thus upsetting the equilibrium of the strata and distorting the road.

Jan 1, 1940