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By P. R. Clifford

Phosphogypsum is a byproduct of the manufacture phosphoric acid. There are approximately one billion tons of phosphogypsum stored in stacks in northern and central Florida. The Florida Institute of Phosphate Research (FIPR) is investigating potential uses of phosphogypsum. These include using phosphogypsum as a road base material, as a soil amendment in agriculture, as a daily cover in landfills, and as a construction material. The results of this research will be presented and will be discussed in light of regulatory barriers to the use of phosphogypsum.

Jan 1, 2002

By S. H. Williston

IT not often that bore hole surveys can be checked by actual. civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bis-bee, Ariz., drilled a 1245 ft, 8 in. diarn, churn drillhole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Because of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results of doubtful value. Sperry-Sun gyroscopic well-surveying instruments were finally used to locate the bottom of the hole. These instruments consist of a gyroscope to determine azimuth and either a pendulum or bubble inclino-meter. A multiple shot camera photographs both instruments on a single film and superimposes the photograph of a watch. Coordination of depth with time at the surface makes it possible to select the corresponding picture for any depth. After making several runs of the empty instrument housing from the top of the hole to the bottom to make sure there were no obstructions in the hole, three surveys on wire line were completed during the afternoon. The three surveys, in which readings were taken at different points in the hole on each survey, were computed and gave the following locations of the bottom of the hole in relation to the surface collar: survey No. 1—24.92 N, 30.30 W; survey No. 2—24.24 N, 31.11 W; survey No. 3—26.54 N, 27.72 W. Then the data from the three surveys were combined into a single set of calculations which gave a location for the bottom of the hole: combined surveys—24.27 N, 30.16 W. (Fig. 1.) Immediately upon the determination of the coordinates at the bottom of the hole, a drift on the 1300 ft level was started toward the indicated loca- tion some 38 ft northwest of the coordinates of the surface location, The bottom of the hole was located within the drift round in which it was expected, and the transit survey run to the actual location of the hole indicated N 27.18, W 29.71. This shows a discrepancy between the well survey and the transit survey of 0.45 ft in the westerly direction and 2.91 ft in the northerly direction. All surveys, both gyroscopic and transit, fell well within the width of an ordinary drift. While this is satisfactory for almost any and all mining requirements, a theoretical examination was made as to reasons for the discrepancy. A study of the course of the hole indicates that considerable right turn or spiral existed, and in all probability the surveying instrument was pulled out of alignment while traversing the turn by approximately 0.05 ft at the top and another 0.05 ft in the opposite direction at the bottom of the instrument. If such an allowance were to be made, the survey calculations would almost exactly correspond with those determined by transit. This sort of discrepancy would be minimized by the use of stabilizing guides. It is unfortunate that physical laws probably effectively prevent the use of gyroscopic instruments in EX and AX diamond drill holes. The directive power of a gyroscope falls off inversely at some rate between the third power and the sixth power of the diameter. Present instruments can be run in casing 53/4 in. ID or over and might be adapted to somewhat smaller diameters, but the difficulty of reducing these diameters to 11/4 in. or 2 in. is almost insurmountable at the present time. Acknowledgment The author wishes to express his appreciation to the Phelps-Dodge Corporation for permission to publish this article, and to the Operating and Engineering Departments for their cooperation on the survey; also to Donald Hering, of the Sperry-Sun Well Surveying Co., who actually made the survey and calculated the results.

Jan 1, 1951

By S. H. Williston

IT not often that bore hole surveys can be checked by actual. civil engineering methods. A recent Arizona survey was checked by normal surveying methods and the comparison of the results should be of value to both oil and mining men. During the summer of 1948 the Phelps-Dodge Corporation, at its Copper Queen property near Bis-bee, Ariz., drilled a 1245 ft, 8 in. diarn, churn drillhole in a mineralized area and cased part of it, intending to use it to transfer mill tailings for stope fill. The hole, as frequently occurs, was not straight, and, in endeavoring to locate the bottom in the underground workings, they found no evidence of the hole at the underground coordinates directly below the surface location. The noise of the drilling tools was reasonably clear, but the direction of sound was uncertain. Preliminary tests with available equipment were not successful in locating the bottom of the hole. Because of the mineralized character of the area and the fact there was some casing in the hole, any magnetic method of well surveying would give results of doubtful value. Sperry-Sun gyroscopic well-surveying instruments were finally used to locate the bottom of the hole. These instruments consist of a gyroscope to determine azimuth and either a pendulum or bubble inclino-meter. A multiple shot camera photographs both instruments on a single film and superimposes the photograph of a watch. Coordination of depth with time at the surface makes it possible to select the corresponding picture for any depth. After making several runs of the empty instrument housing from the top of the hole to the bottom to make sure there were no obstructions in the hole, three surveys on wire line were completed during the afternoon. The three surveys, in which readings were taken at different points in the hole on each survey, were computed and gave the following locations of the bottom of the hole in relation to the surface collar: survey No. 1—24.92 N, 30.30 W; survey No. 2—24.24 N, 31.11 W; survey No. 3—26.54 N, 27.72 W. Then the data from the three surveys were combined into a single set of calculations which gave a location for the bottom of the hole: combined surveys—24.27 N, 30.16 W. (Fig. 1.) Immediately upon the determination of the coordinates at the bottom of the hole, a drift on the 1300 ft level was started toward the indicated loca- tion some 38 ft northwest of the coordinates of the surface location, The bottom of the hole was located within the drift round in which it was expected, and the transit survey run to the actual location of the hole indicated N 27.18, W 29.71. This shows a discrepancy between the well survey and the transit survey of 0.45 ft in the westerly direction and 2.91 ft in the northerly direction. All surveys, both gyroscopic and transit, fell well within the width of an ordinary drift. While this is satisfactory for almost any and all mining requirements, a theoretical examination was made as to reasons for the discrepancy. A study of the course of the hole indicates that considerable right turn or spiral existed, and in all probability the surveying instrument was pulled out of alignment while traversing the turn by approximately 0.05 ft at the top and another 0.05 ft in the opposite direction at the bottom of the instrument. If such an allowance were to be made, the survey calculations would almost exactly correspond with those determined by transit. This sort of discrepancy would be minimized by the use of stabilizing guides. It is unfortunate that physical laws probably effectively prevent the use of gyroscopic instruments in EX and AX diamond drill holes. The directive power of a gyroscope falls off inversely at some rate between the third power and the sixth power of the diameter. Present instruments can be run in casing 53/4 in. ID or over and might be adapted to somewhat smaller diameters, but the difficulty of reducing these diameters to 11/4 in. or 2 in. is almost insurmountable at the present time. Acknowledgment The author wishes to express his appreciation to the Phelps-Dodge Corporation for permission to publish this article, and to the Operating and Engineering Departments for their cooperation on the survey; also to Donald Hering, of the Sperry-Sun Well Surveying Co., who actually made the survey and calculated the results.

Jan 1, 1951

By Kim Lapakko

Increasing public concern over the welfare of the environment has placed demands on the mining industry to evaluate the environmental impact of mining development. This is a difficult task and involves considering the influence of a multitude of variables on complex processes over a long time period. Few studies which focus on the evaluation of the environmental impact of mining have been conducted and, therefore, there is little past experience to rely upon. This article describes some of the work done to evaluate the potential environmental impact of mining development in Minnesota. Interest in developing the major copper and nickel sulfide deposits near the wilderness areas of northeastern Minnesota aroused concern regarding the environmental impact of mining development in the region. As a result laboratory and field studies were initiated to investigate the potential for trace metal leaching and acid generation due to dissolution of Duluth gabbro. Chemical equilibrium computer modeling was conducted to aid in data interpretation. The goals of the study included the investigation of leaching mechanisms and rates of release (1, 2).

Jan 1, 1980

By Helmut Hass, Michael B. Gilbert

The extension of the commuter railway system (S-Bahn) in Leipzig, Germany willrequire the construction of an underground line crossing the downtown area of thecity to tie the Bavarian Station in the South to the Main-Station in the North. The City-Tunnel-Leipzig is currently one of the largest infrastructure projects in Europe. This system extension will have a length of approximately five kilometers. 3.9 kilometers of that length are currently being constructed using either cut & cover construction or tunnelingmethods. The design and construction of this project currently is and will continue facing very significant challenging urban and demanding geotechnical conditions.

Jan 1, 2007

By J. Matos e Silva

"Abstract Although one can think that it is very low the probability of a seism occurrence during the execution of an excavation in an urban lot protected by a diaphragm wall curtain, reality shows that whenever a seism occurs in an urban area several diaphragm walls will be affected by it. So it is advisable to consider the seismic action when designing a diaphragm wall curtain. The paper refers the main information about the seismic design of diaphragm walls according to the Eurocodes 7 and 8 and to the Portuguese Norms related to them (respectively NP EN 1997-1 2010 and NP EN 1998-5 2010), as the Eurocodes consider the possibility of each European country to adopt their own seismic parameters as the seismic risk is different in each country. Thus the so-called National Document of Application (in our case the Portuguese Norms) prescribes the seismic local parameters.1 - EUROCODES AND PORTUGUESE NORMS PRESCRIPTIONSAccording to Eurocode 8 - Part 5 and to the related Portuguese Norm NP EN 1998-5 2010, seismic actions on soils should be quantified adopting the Mononobe-Okabe method that gives goodapproaches when compared with reality.From paragraph 7.3.2.2 of the referred Norm, the horizontal seismic coefficient kh will be:"

Jan 1, 2014

By R. C. Milici

The primary factors that determine the marketability of coal from various supply centers in the U.S. are coal quality and supply; i.e. low sulfur, moderate- to high- Btu coals have large market areas when compared to less expensive but poorer quality coals. Price is the major factor in the competitive marketing of similar coal products. Good quality, (moderate- to high- Btu, low sulfur) coals from the Powder River and central Appalachian basins are marketed over large areas of the country, and central Appalachian coal is widely distributed in foreign markets, primarily as coking coal. In contrast, poorer quality bituminous coal (low calorific value and/or high sulfur) from the Illinois Basin, northern Appalachian Basin, and lignite from the Gulf Coast is marketed in or near the States in which it was mined even though the price at the mines may be lower than mine prices for central Appalachian coal. Widespread distribution of sub-bituminous Powder River Basin coal is enhanced by its exceptionally low mining costs, which offsets transportation costs to distant markets.

Jan 1, 2001

By F. L. Wilke

The prototype of an expert system, designed to assist layout planning of face operations, is presented. By specific combination of knowledge-based and conventional EDP techniques it has been possible to extend the known Kepner-Tregoe method up to the determination of mature layout solutions in difficult planning cases. It has been proven that the presented strategy - which can be applied to any kind of problem with similar structure - is apt to provide efficient EDP support for handling complex mining problems. Such support goes far beyond the purely numeric evaluation of envisaged alternatives.

Jan 1, 1989

By Ben R. Bjorkman

The future is here ? or at least that?s what Mine Planners predicted some 15 years ago ? that by 2004 we would have man-less mines running themselves using space-aged technology. Truthfully, though, there hasn?t been much change in mining methods in the past decade, but thankfully that?s all about to change. The benefits of autonomous ? even Tele-operated mining (especially in narrow-vein ore bodies) are wellknown: increased production hours by eliminating travel time to and from the face, continuous production at the face while crews screen and bolt behind the working equipment, less liability for workers? safety in certain areas, etc. But when plans are put in place to accomplish this vision, things stagnate and production carries on as before. This paper examines the components necessary to make that vision a reality. First we?ll detail the technology required to enable Tele-operation ? even autonomous operation of mining machinery, then we?ll look at what?s wrong with the current way we?re mining, and finally conclude with a critique of the machinery itself.

Oct 1, 2004

By Jan L. Reichelderfer, Thomas L. Richardson

Completion of the H-3 Highway Tunnel Project was a critical element in opening this award winning project. The exploratory tunnel was completed as a maintenance tunnel and included difficult shafts extending into the main tunnel cross passages. The project also involved a major addition to the traffic operations center including a deep excavation in close proximity to the tunnel portal structures. The projects also included various completions and improvements to the main tunnels, such as paving, drainage, maintenance, and a variety of critical life-safety issues, such as radio systems, telephones, etc. The highway opened in December 1997.

Jan 1, 2001

By G. H. Clamer

Page Bronze Bearing Metals. By G. H. Clamer............... 162 Pennsylvania Railroad Anti-friction and Bell Metals. By F. M. Waring .. 166 The Tin-plate Industry. By D. M. BUck. Discussed by G. H. ClameR, J. W. RICHARDS............................ 168 The Aluminum Bronze Industry. By W. M. Corse............ 171 Bronzes, Bearing Metals, and Solders. By G. K. BURgess and R. W. Woodward. Discussed by G. H. Clamer, R. T. Roberts......... 175 Babbitts and Solder. By G. W. Thompson................ 184 The Cadmium Supply of the United States. By C. E. Siebenthal. Discussed by M. L. Lissberger, C. W. Hill, F. F. ColcoRd.......... 185 Solder, Its Use and Abuse. By M. L. LissbergeR............ 192 Bronze Bearing Metals G. H. ClameR,* Philadelphia, Pa.—Unfortunately, prior to the war no serious attention was given to the conservation of tin, notwithstanding that this country is practically dependent upon outside sources for its entire tin supply. Tin is of vital importance in many industries, but it is surprising how many and how excellent are its substitutes when we become acquainted with them. Tin has always been a relatively high-priced metal, and it is part of the human attitude to associate high prices with high standards; it is not until the price of a commodity becomes well-nigh prohibitive that we hunt for substitutes, because the idea of substitution seems always to involve an assumption that the substitute must necessarily be inferior. The history of the development of bearing bronzes is a striking example of this policy. In the early days, copper-tin alloys were almost universally used, the idea then being prevalent, which is still held by many, that a bearing to resist wear must be hard, and the harder the better. The favorite bronze bearing contained 90 per cent. copper and 10 per cent. tin; frequently, in service which was considered severe, even higher proportions of tin were used. Such hard alloys have great resistance to compression, but as a rule they had a very wide factor of safety in this

Jan 1, 1919

By W. B. Daly

THE sampling and estimating of, the orebodies in the mines of the Anaconda Copper Mining Co., at Butte, have been made a part of the work of the geological department. The wisdom of this assignment is apparent, considering the organization of that department, the nature of, its records, and the scope of its regular work. In the first place, the district is divided into units of two or three mines each and a geologist is assigned to each group. His trips to all the working places are frequent and he follows the mining operations closely. His notes are graphic and detailed. In the office, he posts his notes on the standard maps and sections and on special maps for correlation purposes. With the approval of the chief or assistant chief geologist, he recommends development work underground and watches its progress. This gives the geological department a precise knowledge of the character of each orebody. Sampling is done by one or two samplers at each mine working under a chief sampler stationed in the geological office. The chief sampler has access to all the office maps and is in frequent consultation with the geologists; his instructions to the samplers are issued with the approval of the chief or assistant chief geologist. Not only is it important that the geologic information be used to direct the sampling but the reports of the samplers and the records kept by their chief are useful to the geologist, who needs them in his work of I estimating ore reserves and deciding on recommendations for development work. The sampler, moreover, is at the mine every day and makes a daily report, which keeps the geologist in close touch with 'the progress of development work. The sampler is attached to the mine office and thus comes under the jurisdiction of the operating department. In fact, any special orders prepared by the chief sampler are submitted to the general superintendent, after approval by the geological department. The mine foreman may.

Jan 2, 1922

By Frank Haas

Many articles on the physical properties of fire damp have appeared in the Transactions and elsewhere but practically nothing has been written in regard to its occurrence or fluctuation in quantity in an ordinary mine. After the Monongah explosion in 1907, with the loss of 361 lives, the Consolidation Coal Co. sought a method by which such catastrophes could be prevented. While the cause of this particular explosion was attributed to coal dust, some of those acquainted with the mine thought that fire damp was involved, if it was not the initial cause. So the literature on the subject was studied and mines where similar conditions prevailed in this country and Europe, were visited, with the view of establishing some system by which gas could be more easily detected and controlled. The results of this study were disappointing for no method was found other than the time-honored fire boss with his safety lamp, with some variations in the rules and regulations governing his inspections and reports. Duties of the Fire Boss Pending the development of a better method, it was decided to standardize and perfect the duties of the fire boss and the reports based on his observations. Those who were then in service were closely examined, various lamps were experimented with and the lamps and individuals tested under known conditions. It was found that a fire boss could tell whether gas was present but his estimate of quantity was not even an approximation; therefore, while the services of fire bosses were indispen-sible there was need of additional information by which the quantity of gas could be estimated with some precision in order to determine its variation from time to time. Chemical Process for Determination of Methane After considering all methods known at that time a chemical process was adopted. The principles involved in the process are that in an enclosed receptacle, in the presence of excess air, methane will be completely burned by means of a hot platinum wire to carbon dioxide and

Jan 1, 1927

By R. G. Gillies

The pipeline transport of paste, backfill or thickened tailings slurries is an important component of the tailings disposal process in many mines around the world. These mixtures contain significant fractions of fine (clay) and coarse (sand) particles, causing them to exhibit non-Newtonian flow behaviour and high frictional pressure gradients. There is often economic incentive to operate these pipelines in the laminar flow regime. Irrefutable evidence has shown that coarse particle settling can occur during the laminar flow of these slurries even when static settling tests show no indication of such behaviour. Previously, a ?rule-of-thumb? minimum frictional pressure gradient of ~1.5 to 2 kPa/m was suggested to ensure effective sand transport, based on the results of tests conducted using viscous Newtonian oils. In this paper, we examine the results of laminar flow tests of non-Newtonian, coarse-particle laden slurries conducted with pipeline loops of 50, 100, 150 and 250 mm in diameter. The results indicate that the ratio of the mean wall shear stress to the mean surficial particle stress is a better indicator of laminar flow settling tendency than frictional pressure gradient.

Jan 1, 2007

TABLE TUNNEL NAME OWNER LOCATION STATE TUNNEL USE LENGTH (FEET) WIDTH (FEET) BID YEAR STATUS Gateway Tunnel project Amtrak Newark NJ Subway 14,600 24.5 2015 Under study

Sep 1, 2013

By Lan Vu

"The Ferderber mine consists of a series of Archean gold-bearing quartz lenses within a shear zone that crosscuts the central part of the quartz diorite Bourlamaque batholith. This zone has sharp contacts with the enclosing quartz diorite, and on average strikes N70E and dips 65SE. Along the contact with the shear zone, the quartz diorite is chloritized, sericitized and carbonatized. The chlorite schist within the zone is probably derived from mafic dykes.The geometry and distribution of structural features within the Ferderber shear zone suggest a long history of repeated movements. The majority of gold-bearing lenses were first emplaced during a probable early period of brittle shear which resulted from strike-slip movement. They were then folded and pulled into boudins by a later episode of reverse movement that accompanied ductile shear. New mineralized veins were emplaced in the shear zone and deformed at this time.Mineralized veins are dominated by quartz, carbonates, tourmaline and micas. Gold is more common within pyrite where chalcopyrite is abundant and is generally in contact with both pyrite and chalcopyrite at ""triple point"" grain junctions. This intimate association suggests that copper may have played an important role in gold deposition.Recent exploration has shown that the Bourlamaque batholith is cut by many parallel or en echelon shear zones. Study of ""Landsat"" and aerial photographs has indicated a number of linear structures striking ENE-WSW and ESE-WNW which form a conjugate system. The intersection of these two structural trends presents an interesting exploration target."

Jan 1, 1990

Ladies and gentlemen, distinguished guests and fellow members of The AusIMM, good morning.   Thank you for the opportunity to address you all today, Crown Minerals are very pleased to be associated with the conference again this year, and I commend the committee on their organisation and delivery of this yearÆs event.   As you can see from the topic of my discussion, I would like to broach the subject of collaboration between ourselves û Crown Minerals û and you our clients, and convince you that we are on the right track but can each do more.

Jan 1, 2007

By Ray L. Tobie, Douglas E. Julin

GENERAL DESCRIPTION Block caving is a distinct caving method applied mostly to large, massive, ore bodies because of its in¬herent low cost and high production capabilities. Areas of sufficient size are removed by undercutting so that the mass above will cave naturally. Drawing of the caved ore at the bottom of the ore column causes the caving action to continue upward until all of the ore above the undercut level is broken into sizes suitable for handling. When properly applied, block caving results in a lower mining cost per ton than any other under¬ground method. There are three distinct forms: (1) dividing the horizontal area into rectangular or preferably square or nearly square blocks, drawing evenly over the entire area to maintain an approximately horizontal plane of con¬tact between broken ore and caved capping; (2) divid¬ing the horizontal area into panels across the ore body, retreating by undercutting manageable areas from one end of the panel to the other and maintaining an in¬clined plane of contact between the broken ore and caved capping (thus the name panel caving); and (3) no division of horizontal area of the ore body into defi¬nite blocks or panels (this is termed mass caving). Undercutting may be from wall to wall, retreating from one end of the ore body to the other, maintaining an inclined plane of contact between the broken ore and caved capping. The total active caved area is deter¬mined by the size of block that will not produce undue stress on workings below the undercutting level and by total production requirements. This type of operation is also referred to as panel caving at some properties. SUITABLE ORE BODIES Block caving in its various forms is applicable to deposits of various shapes and ores of various strengths. Its success is governed by rigid requirements and limi¬tations. In unsuitable deposits or where improperly em¬ployed, the loss of ore may exceed that of any other mining method. Good planning, systematic work pro¬cedures, careful supervision, and good judgment con¬tribute to its success. Ore Characteristics Included as a necessary characteristic in an ore body suited to a successful block-caving operation is a proper fracture pattern. Ore hardness should be another gov¬erning factor, and the toughness or softness of the ore should be considered. There must be sufficient horizon¬tal area available for expansion of the undercut, if neces¬sary, to start the caving process. Large, massive, ore bodies usually meet these conditions. Veinlike deposits must be wide and dip rather steeply to conform to the block-caving limitations. The capping must be of such a nature as to cave when the underlying ore is being removed since the weight of the overburden aids in crushing the ore. The most favorable capping character¬istic is that it breaks into coarse pieces and resists attrition as the block is drawn. Soft capping, by breaking into fine pieces and sifting into the ore or channeling through the ore to the drawpoints, can seriously dilute the ore and hinder the extraction of clean ore from the blocks. Types of Ore In block caving, a fairly uniform distribution of val¬ues in the ore is necessary. Grade values may range from low grade to high grade, but most often the sys¬tem is applied to low-grade ores. Wide veins, thick beds, or massive deposits of homogeneous ore overlain by ground which will cave constitute suitable ore bodies. The ore must be such that it can be supported while blocks are being developed and undercut but breaks up readily when caved. Some applications include porphyry copper, disseminated molybdenite, hematite in the Lake Superior iron district, limonite deposits in northern Spain, the diamond mines of South Africa, asbestos and nickel in Canada, and massive magnetite in Pennsylvania. Size and Shape Outline of the ore body should be fairly regular, and the sides of the ore body should dip steeply. It may not be economical to mine small portions of ore extending into the walls of the deposit, and low-grade inclusions in the ore cannot be left unmined. Some dilution of the ore, as mining progresses, by low-grade or barren cap¬ping is inevitable and, unavoidably, some clean ore is left between drawpoints. Determining Cavability The use of rock mechanics is sometimes advantageous in helping to determine the cavability of an ore deposit. The US Bureau of Mines has information and testing ability which can assist in determining the cavability of ore types. Several competent consulting orga¬nizations knowledgeable in rock mechanics can also as¬sist in evaluating the cavability of an ore body. Some recent work has been done to better define the cavability index of various ore bodies; an example of how this was determined is discussed by McMahon and Kendrick (1969). The intensity of the fracture pattern is a critical parameter to be analyzed. The question to be answered is, "How intense must the fracture pattern be?" Table 1 is a tabulation of the size of rock fragments that appear at the drawpoint of various block-cave mines around the world. These are indicative of the fracture-pattern spac¬ing and, as can be seen, they vary substantially from the almost sandy material at the Mather mine to fairly sizable blocks at the Grace mine. Several sets of fractures are essential to promote good caving. Ideally, two vertical sets at nearly right angles to each other and a third set nearly horizontal are required to insure a good caving ore body. Since initial caving of an ore mass is almost always by the action of gravity acting on these planes of weakness, it is doubtful

Jan 1, 1982

By J. R. Johnson, C. G. Stewart, D. K. Myers

INTRODUCTION Radon-222 is an inert, radioactive gas formed by the radioactive decay of radium-226, a long-lived member of the uranium-238 decay chain. Radium is present in varying amounts in virtually all soils and, on the average, about 36,000 pCi (1330 Bq) of radon per square meter of soil diffuse into the atmosphere each day (UN 1977). Radon decays with a half-life of 3.6 days through four short-lived daughters to lead210 and it is these short-lived daughters[ [Ra A, (218Po, t, = 3.0 min) , Ra B, (214 Pb, t;, = 27 min), Ra C, (214Bi, t] = 20 min) and Ra C1 (214Po, t] = 2.5 x 10-6 min)] ]which cause the major health hazard associated with radon (Bale 1951). Atoms of these daughters, either unattached or attached to the ever-present particles in air, are deposited on the surfaces of the respiratory tract; alpha particles emitted in their decay can result in large doses to the cells of the bronchial epithelium lining the respiratory tract. These daughters will be present in air in varying relative concentrations depending on the "age" of the air (time since radon emanated into it) and on the amount of mixing of radon and radon daughter contaminated air with clean air. [The practical unit developed to quantify the amount of radon daughters in air is the Working Level (WL). This unit was historically related to the equilibrium concentration of 100 pCi (3.7 Bq) of the short-lived daughters of radon in one liter of air (cf. Holaday 1969) and is defined as any mixture of the short-lived daughters in a liter of air that have a-potential alpha energy of 1.3 x 105 Mev (2.08 x 10-5J) in their decay to lead-210. The working level month (WLM) was developed along with the WL, and was defined as an exposure to one WL for a working month (170 h). This is equivalent to 2.2 x 107 MeV•h•L-1 (3.54 x 10-3 J.h.m-3). If the average breathing rate is taken as 1.2 m3.h•1 (ICRP 1975), then one WLM is equivalent to inhalation of 4.24 mJ of potential alpha energy.] It is now generally agreed that the inhalation of radon daughters is the major potential radiation hazard in uranium mining, and contributes a substantial fraction to the natural radiation exposure of the general population due to the accumulation of radon and radon daughters from natural sources in buildings. Radon daughter concentrations in modern mines are controlled by ventilation, and by blocking off old working areas (cf. Simpson, 1959). However, before the hazard from radon daughters was recognized, considerably higher concentrations of radon daughters were present in some uranium and non-uranium mines. These high radon daughter concentrations resulted in an increase in lung cancers in the mining population, and it is these results that are our main source of information on the risk of inhaling radon daughters. HISTORICAL REVIEW Many excellent reviews of the history of understanding the health effects of inhalation of radon daughters are available (see, for example, Hueper 1942, Lorenz 1944, Sikl 1950, Stewart 1964, Holaday 1969, Lundin 1971, Cross 1979) but a brief summary of some of the highlights in this area may be of interest. [a] 1556: Agricola describes an unusual and fatal chest disease occurring among underground miners in the region of Schneeberg and Joachimsthal (Jachymov) in the Erz mountains in Central Europe. (It is of some historical interest to note that Agricola's book was translated from Latin into English by a mining engineer and his wife; the engineer later became President of the U.S.A.) [b] 1879: Haerting and Hesse indicated that the majority of deaths among Schneeberg miners were due to lung cancer; the lung cancers in these miners (who were incidentally not cigarette smokers) were observed twenty to fifty years after they began working in the mines. [c] 1896: Discovery of natural radioactivity by Becquerel, followed by discovery of radon by Dorn in 1900. [d] 1924: Ludewig and Lorenser report high concentrations (400 - 15000 pCi or 15 - 570 Bq per liter) of radon in the air in the Schneeberg mines and suggest that radon could be responsible for the high rate of lung cancer among miners. However, the reason why radon should cause lung cancer specifically was still not really understood up to twenty years later (Lorenz 1944). High concentrations of radon in the air in the Joachimsthal mines were reported by Behounek in 1927 and a high incidence of lung cancer among Joachimsthal miners (similar to that among miners at Schneeberg, which is only some 30 km distant but in a different political district) was noted at about the same time (Sikl 1930; cf. Sikl 1950). It is estimated that about half of the Joachimsthal miners died from lung cancer and about half from silicosis and tuberculosis (Sikl 1950). [e] 1930's and 1940's: Radioactive ores are deliberately mined in the U.S.A., Canada and other countries primarily as a source of radium for medical purposes and for luminescent dials; other radioactive ores are mined as a source of several non-radioactive minerals, while extensive uranium mining did not begin until the late 1940's. [f] 1940: Based on crude epidemiology and dose calculations, Evans and Goodman propose 10 pCi L-1 as a maximum permissible concentration of radon in continued human exposure. This is the first known recommended maximum permissible concentration for radon. This recommendation was adopted by the U.S. National Bureau of Standards in 1941 and reconfirmed in 1953. [g] 1945: Mitchell identifies the short-lived daughters in radon as a likely cause of the increased lung cancers in the Schneeberg-Joachimsthal miners

Jan 1, 1981

Abrasivity and wear resistance are not intrinsic properties of materials, but rather parameters describing the interaction between the wear part and the material exerting the wearing action. Moreover, wear or, at least, that part of the wear which is due to the cumulative effect of minute scratches, is linked to the hardness disparity concept. Abrasivity, in this context, is a relative concept, pertaining to a metal-rock pair, rather than to a rock. Based on this assumption, a methodology has been developed and checked against actual cases, enabling description of the abrasiveness of arock or the abrasion resistance of a metal through the ratio of comparable quantitative indicators. The paper describes the methods and provides examples of applications to practical cases(namely: rock cutting, excavation by means of tunnel boring machines (TBMs), rock crushing, and hydro-mill cutting).

Jan 1, 2012