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By David Dardick

Tround International Inc. is developing rock excavation and drilling devices which utilize a simple patented mechanism for firing frangible projectiles. This system launches a salvo of three projectiles with every shot in automatic sequence. Studies conducted by Physics International Inc. have demonstrated that firing projectiles into hard rock such as granite creates fragmentation which is much faster and cheaper than conventional drilling and blasting. The Tround salvo approach enhances this further by a controlled stresswave interaction created by a slight time difference during impact of the individual projectiles. The University of Maryland is conducting additional studies to optimize these parameters.

Jan 1, 1981

By C. Cánepa

In the treatment of many problems related with the optimization of a given ore dressing process, microscopic studies can provide invaluable assistance. Such studies are generally carried out through mineralogical determinations both qualitatively and quantitatively. Frequently the solution of a specific problem requires the combination of these in adequate proportions. Often the nature? of the problem poses some conditions regarding the way the microscopic determinations are made in order to yield useful information. Most publications applied to mineral beneficiation show results of ore microscopy without mentioning the methodological details involved in the determinative work and therefore it is not possible to judge their reliability and/or their relevance. As methodology must necessarily change from case to case, it is very important for the microscopist to identify first the direct and indirect mineralogical information required to solve the problem. Without such guidelines selection of methods for the qualitative and/or quantitative determinations cannot be made.

Jan 1, 1981

By D. D. Marsden, L. E. Kun

Although a regulation is in force that all water used underground shall be free of bacterial contamination, in practice it is often very difficult to accomplish this. The standard method of disinfection m South African mines IS treatment with calcium hypochlorite, although liquid sodium hypochlorite is used at a few sites. Primarily because the process depends on human control for the addition of the hypochlorite and the regulation of its now, it is frequently found difficult to disinfect mine water adequately and continuously. In many marine environments, chlorine generated by the electrolysis of seawater in its passage through an electric cell is used for disinfection. The generation procedure is continuous and needs no human control except for occasional checking of the equipment. This paper describes the successful implementation of the process, suitably .modified, .at four underground sites. After severe scaling problems had been overcome, a procedure resulted that chlorinates considerably more effectively than the previous system (dosing with calcium hypochlorite), and that has a lower amortized operating cost.

Jan 1, 1981

By Richard Gallagher, Russell K. McFarland

INTRODUCTION The Southern California Rapid Transit District has commenced Preliminary Engineering for an 18 mile Metro Rail Project. This initial line will consist of approximate 36 miles of single track tunnel and 16 subsurface stations. The estimated cost of $1.2 Billion in 1978 dollars, places it in the category of a major public works project. During the planning phase of this project, particular attention was paid to the National Academy of Science Reports, "Better Contracting for Underground Construction" (1974), "Better Management of Major Underground Construction Projects" (1978), and "Management of Urban Construction Programs" (1980). The improved transportation service that this project will furnish the Los Angeles Metropolitan Area will result in significant benefits that will add immensely to the economic well being of the community-which is one of Webster's definitions of improved productivity. RAPID TRANSIT PROJECT BACKGROUND Rapid Transit studies have been going c in the. Las Angeles area since 1925. In 1969 and 1974, sales tax ballot issues were not adopted by the electorate of the county mainly because the pre-ponderous of County voters are outside the City of Los Angeles.

Jan 1, 1981

By W. J. Guay

Carbonaceous gold ores containing gold dispersed in sulfides are refractory to cyanidation because: ( 1) the carbonaceous materials adsorb gold during cyanidation; (2) a portion of the gold is so finely dispersed in the sulfide mineral lattice as to preclude contact with cyanide solution; and (3) a portion of the gold is chemically combined with carbonaceous material. Techniques which have been used to treat these ores are: (1) roasting or chemical oxidation to decompose sulfides and carbonaceous materials; (2) flotation to reject carbon; (3) the use of kerosene or other reagents to passivate the adsorptive carbon compounds; (4) carbon or resin in pulp; (5) flotation of a bulk concentrate which is treated by one of the above methods; and (6) the use of chelating agents which have a stronger affinity for gold than the activated carbon in the ore.

Jan 1, 1981

By Albert G. Funk, Gary M. Thornley

The available energy of aluminized ANFO and aluminized slurry blasting agents has been measured by seismic methods, calculated theoretically, and compared. With aluminized ANFO it is concluded that aluminum concentrations should be restricted to less than 10 percent because of diminished energy yields at high aluminum concentrations. However, with aluminized slurry it is concluded that efficient use of aluminum can be made at aluminum concert"rations up to 18 percent. It is further concluded that the difference in efficiency of use of aluminum by these two classes of blasting agents results from a higher contribution to useful work from the condensed detonation products of the relatively higher density aluminized slurry blasting agent.

Jan 1, 1981

By Joginder S. Bhore, Francis M. Keville, David E. Puza, Roger C. Borggaard

A portion of the Massachusetts Bay Transportation Authority's Red Line Extension through Somerville, Massachusetts consists of 1,553cm (5,092 LF) of hard rock tunneling 6.7m (22 ft.) diameter horeshoe, 148m (485 LF) of mixed face tunneling, 7.2m (23 ft.) diameter circular, beneath an active railroad in a heavily commercialized business district. This paper will deal with the excavation of the mixed face area without the use of a shield. It will address the special excavation and support problems encountered during tunneling operations using the floating crown bar and modified spiling methods. Topics covered will include excavation and support methods, cement grouting, compaction grouting, and instrumentation. PROJECT DESCRIPTION The Davis Square to Porter Square Tunnels and Shafts Somerville/ Cambridge, Massachusetts is part of the Massachusetts Bay Transportation Authority's (MBTA) 5.1km (17,000 ft.) Red Line Extension. This extension runs from Harvard Square, Cambridge, to Alewife Brook Parkway, Cambridge through Somerville. This portion (MBTA Contract #091-106) required the excavation and concreting of 1,701m (5,580 LF) of single track twin tunnels consisting of 1,553m (5,092 LF) of conventional hard rock tunneling under 56 residential properties and 148m (485 LF) of mixed face tunneling beneath an active railroad in a heavily commercialized business district. The mined diameter of the mixed face tunnel is 7.16m (23.5 ft.) Access to the tunnel was via the Summer Street vent shaft, and the two Grove Street access shafts where all tunnel excavated materials were removed.

Jan 1, 1981

By F K. Buckley

Currently, Kanieri Gold Dredging Limited operates the only large scale gold dredging operation in New Zealand. It dredges a claim in the Taramakau River using the bucket dredge 'Kanieri'. This dredge, a 'Yuba' type, was designed and built in the 1930s. On the current claim it works about 12 hectares of ground a year. Because of its design, the tailings from the 'Kanieri' make land restoration difficult. This was unimportant until it commenced its new claim ML-32-310 in 1978. The conditions, attached to this licence required it to restore the land for afforestation, the designated use fur the Crown land being mined. With the company planning to work future claims on the Grey River, it decided to undertake restoration work on the Taramakau to demonstrate its capability of establishing pasture land on tailings, a more difficult task than restoring the land for afforestation. After two years and the restoration of two blocks totalling 22 hectares, reasonable pasture establishment has been achieved. Much has been learned to date and further refinement of the techniques used will take place over the next two years. The quality of the tailings produced has improved as a result of the limited modifications possible on the existing dredge. This has been significant in achieving better results. The knowledge gained will be taken into account in future dredge design. Both the Company and its Consultant are confident of achieving satisfactory restoration of dredge tailings for pasture land.

Jan 1, 1981

By H. Seguin, J. A. Le Gac, S. Bernhard, P. R. ZETTWOOG

The "Service de Protection Technique"of the "Institut de Protection et de Sûreté Nucléaire" was asked by the Commission of European Communities to conduct measurement campaigns which would make it possible to evaluate, on an experimental basis, the collective risk to miners exposed to radon in underground, non-uranium mines located in countries within the European Community. 1. METHODOLOGY USED TO CONDUCT THE CAMPAIGNS This campaign is original in that direct measurements of the individual monthly exposure to potential [a]-energy from short-lived radon daughters are made using personal [a]-dosimeters described previously (1). We call this type of dosimetry "personal dosimetry". The workers who wear the personal [a]-dosimeters were selected taking into account the various categories of workers and their work assignments in the various areas of the mine. Another way of finding out the occupational exposure of these miners consists in making numerous measurements of the radon concentration at the various work places, taking into account the time spent at each place by each worker. This procedure is too complex for an evaluation of the collective risk as requested by the Commission of European Communities and was therefore rejected. Additional data was gathered during these measurements campaigns using the following techniques (table 1). [ ] (1) Current [a]-dosimetry as practiced in France - SPT international report N° 234 - February, 1981 - P. ZETTWOOG The mines were chosen to include a larger variety of types of ore, of geological situations, and of mining methods. 2. RESULTS OF THE RADON DATA-GATHERING CAMPAIGNS 2.1 – [Uranium content of the surrounding rocks and ore] The samples taken during the campaigns make it possible to establish the U content in the rocks of the mines selected. These values, from 2 to 15 ppm, are slightly higher than those usually found (2 to 5 ppm) (table 2). [ ]

Jan 1, 1981

By Anthony Busigin, Stephen Pogorski, Colin R. Phillips

The precision of radon daughter measurement techniques is a complicated function of uncertainties arising from concentration and flowrate fluctuations during sampling, counting statistics and many other factors. Optimization of a measurement technique requires that all these uncertainties - not just counting statistics - be considered. In this work, the optimization procedure of Busigin and Phillips (1980) is tested against Monte Carlo experiments for the case of the modified Tsivoglou method.

Jan 1, 1981

By John H. Paugh

Hydraulic slurrying and pumpability characteristics of phosphate matrix (ore) have not been quantitatively defined. An elemental triangular diagram analysis of rock/sediment texture is used to classify the nature of the ore; then related to empirical field data of hydraulic pressureand production yardage ratios. This experiment is applied as a geotechnical tool to provide empirical data of ore slurry and pumpability characteristics as key considerations in the design of slurry pipeline systems. A real texture variability maps are developed on a section of land to assist mine engineering planning.

Jan 1, 1981

By J. W. Cooksley

Pyrometasomatic zones are a type of replacement deposit, normally in a carbonate rock unit, which consists of a zoned, coarse-grained, generally iron-rich mixture of calcium and magnesium silicates. These zones or rock masses are also called ?skarn,? and ?tactite?. They are formed as a result of the interaction of a shallow intrusion of magma with a carbonate or calcareous host rock and are considered to be of hydrothermal origin. Three environments of pyrometasomatic deposits are depicted in Figure 1. Of course, the interaction takes place at high temperatures. Pyrometasomatic zones are categorized as calcic or magnesian, depending on whether the intrusive interacts with a limestone or a dolomite. Common pyrometasomatic zone minerals are garnet, epidote, quartz, calcite, wollastonite, actinolite, hedenbergite and diopside. Pyrometasomatic zones are of considerable economic importance because they contain ore deposits of tungsten, molybdenum, copper, lead, zinc and iron. According to Rose and Burt (1979), the chronological sequence in the formation of a ?typical? pyrometasomatic deposit is as follows: 1. Shallow intrusion of magma at 900-700°C into carbonate sediments.

Jan 1, 1981

By G. H. Thomas, M. C. O’Riordan, S. Rae

INTRODUCTION The British mining industry comprises 228 nationalised coal mines producing some 113 million tonnes of deep mined coal and employing 242,600 persons of whom 185,200 work below ground. There are in addition 174 small privately-owned coal mines employing 1500 persons underground and producing 1.5 million tones of coal. In the non-coal sector there are 108 privately-owned mines producing some 20 different minerals, including tin, wolfram, fluorspar, potash, rock salt, china clay, ball clay and fireclay. There are currently 4,100 persons employed in these mines of whom 2,346 are employed below ground. One mine producing potash employs 870 persons of whom 465 are underground workers. Since 1975 all matters relating to the health and safety of persons at work and of the general public who are exposed to industrial hazards have come within the purview of the Health and Safety Executive (HSE). The Mines and Quarries Inspectorate (MQI) is a constituent part of that organisation and enforces legislation applicable to all mines and quarries. The National Radiological Protection Board (NRPB) is a statutory and independent body that was established in 1970 to advance knowledge and provide information and advice about radiological protection. The NRPB has an agency agreement with HSE to provide advice and services relating to radiological protection, including protection against exposure to radon decay products in mines. There are as yet no statutory requirements controlling exposure to this source of radiation in Britain. Investigations for the presence of radon in British coal mines were begun in the mid 195Os. The concentrations found were of low order, typically around 2 pCi/l (Duggan et al., 1968). This was not surprising since big coal mines are well ventilated to control methane and airborne dust and it is now generally accepted that radon and its decay products do not constitute a health hazard in British coal mines. At one or two small mines where igneous intrusions were in close proximity to the coal workings, slightly higher readings were recorded. The MQI then commissioned NRPB to make investigations at metalliferous mines and in these much higher readings were detected. It was later agreed that the NRPB should undertake a survey of all non-coal mines in Britain to establish the extent of the problem. This survey was conducted mainly in 1973, (Strong et al.,1975) and follow-up surveys at various mines have since been conducted by the MQI. These investigations revealed that radon readings could be high in mines producing tin, haematite and fluorspar. Some small mines working other minerals in the same localities also showed high readings. More recently owners have been making environmental measurements at mines where there was some cause for concern. LEGISLATION AND RADIATION STANDARDS As a result of the survey work for MQI the Board in 1975 recommended an occupational limit of 4 WLM in a year from radon decay products together with a programme of radiological supervision (Strong et al., 1975). The MQI accepted the recommendation and advised employers and employees that the 4 WLM limit should be adopted. The limit corresponds to a concentration of 0.3 WL, equivalent to 30 pCi/l of radon-222 in equilibrium with the decay products, and was in accordance with an earlier recommendation by the International Commission on Radiological Protection (ICRP, 1959). ICRP recommendations are usually endorsed in Britain. It was recognised that some years would probably be required to achieve general compliance, and this is proving to be the case. Some confusion has been caused in Britain by the conflict between successive Euratom Directives on this and other standards of safety. As relative newcomers to the Community, we were not affected by earlier Directives, but the situation is different now. In 1959, the Commission of the European Communities provisionally recommended a maximum permissible concentration for radon-222 and daughters of 3 x 10-7 µCi/cm3, which corresponds to 300 pCi/l (CEC, 1959). The number was affirmed in 1962 (CEC, 1962) and reaffirmed in 1966 (CEC, 1966) but without any specification of the state of equilibrium. In 1976, the CEC again recommended 300 pCi/l, but on this occasion, the daughters were assumed to be present in the same quantities as in unfiltered air (CEC, 1976): this implies 40 WLM a year in poorly-ventilated mines. The formula is repeated in the latest version of the Directive (CEC, 1980), but the value is now said to be an interim one because it might not ensure compliance with the appropriate dose limit. ICRP (1955) recommended 300 pCi/l in equilibrium with the decay products in 1955 and reduced this value to 30 pCi/l for unfiltered air in 1959 (ICRP, 1959), endorsed it for equilibrium conditions in 1976 (ICRP, 1976), and held to it until 1980: these values imply respectively 40 and 4 WLM a year. The recent recommendation of the ICRP (1980) that the annual limit of intake for the decay products should be 0.02 J in a year corresponds to 5 WLM, but there is a rider that reduction should be made for exposure to gamma rays and long-lived airborne radioactivity. An allowance of 20% is suggested for uranium mines, implying 4 WLM a year for the decay products. The

Jan 1, 1981

By W. A. Cincilla, Z. T. Bieniawski, E. Unal

Although coal mine tunnels such as the main haulageways or roadways are the lifelines of coal mines, little attention has been paid to them in terms of pre-construction planning and design. This paper presents the results of research aimed at improving design methods for coal mine tunnels. Studies of the current practice and design needs in the United States were performed for coal mine development entries. A design approach evolved for coal mine tunnels is presented. It is based on field investigations and laboratory model studies aimed at integrating into reinforcement guidelines for coal tunnels. An up-to-date bibliography on coal mine tunnels is provided.

Jan 1, 1981

By Stanley J. LeFond

The Republic of Botswana, one of the newer countries of southern Africa, attained independence on September 30, 1966. It covers an area of about 225,000 square miles (582,000 square kilometers) which makes it slightly larger than France, or slightly smaller than Texas. It is bounded by Zimbabwe, the Republic of South Africa and Namibia, including the Caprivi Strip. Angola and Zambia are close neighbors. (Map 1). Botswana lies at the center of the southern African plateau at a mean elevation of 3,300 feet (1,000 m). It is a natural habitat for most species of African fauna. The rolling sands and extensive grasslands of the Kalahari Desert cover the southwest. The climate is sub- tropical. Summers, although tempered by north- easterly breezes, are hot, but mean maximum temperature seldom rises above 100°F (38°C). Winters are dry with wide temperature variations, which often give rise to frosts.

Jan 1, 1981

By D. Malhotra, R. M. Hoover, F. N. Bender

The paper discusses the effect of aeration and agitation on grade and recovery of molybdenite. A series of factorially designed flotation tests were carried out in a "Leeds Automatic Laboratory Flotation Cell." Analysts of flotation results indicate that molybdenite has fast floating and slow floating components. The rates of fast floating components, which do not create a problem inflotation, could be varied by changing agitation or airflow rates. However, the rate of slow floating components was stable and was only a function of residence time. Aeration has a significant effect on the grade of MoS2 and only a slight effect on the recovery of MoS2. Agitation has a slight effect on the grade, but does not effect the recovery of molybdenite. The implications of the results on the design of flotation cells and control and optimization of the existing circuits are also considered.

Jan 1, 1981

By David T. Kao

The energy situation the world faced during the decade of the Seventies resulted in actions throughout the free world to reduce its dependence on OPEC oil. Many nations heeded the indicators early in that decade and commenced efforts to reduce their oil requirements. Those nations which did not heed these warnings had the message brought to them more emphatically in the last portion of the decade with the further rapid and continuing rise in prices of OPEC oil. Furthermore, the demonstrated unstable nature of large oil-producing countries has made it clear to all free world nations that their energy demands of the future must be provided for by some more stable and assured supply. Now, early in the decade of the Eighties, we see the need for expanded use of coal as an energy supply to be essential. The result in 1980 and 1981 has been a great increase in demand for steam coal worldwide. In essence, a new business for the United States has developed in steam coal export. In the United States, the large growth in foreign demand for our steam coal is now well recognized and documented. A major impediment in meeting this growing demand became abundantly clear in 1980. This impediment is the congestion existing at U.S. coal export ports. With the recognition of this constraint, a plethora of activity has been observed in announcements for alleviating the problem by improving and expanding current export port facilities. In addition to improvement and expansion, an abundance of totally new facilities has been announced in an effort to find ways to meet this large demand in the new business of steam coal export. This is needed; and hopefully, many of these plans will be translated into action. While total implementation of all stated plans is not expected, much of the implementation depends upon large- scale dredging, large waterside ground storage sites, and improved handling equipments in the conventional type of export ports. The time and capital required for implementation is great, and environmental problems associated with dredging are substantial. Host significantly, and unfortunately, implementation that does include dredging our ports will still not permit use of the truly large colliers of 140,000 DWT and greater, which are evolving as the "state of the art" in long-distance sea transport.

Jan 1, 1981

By William L. Carter

Through your presence here this morning and your membership in the Society of Mining Engineers, you have shown that you are interested in keeping abreast of the latest technology and mining procedures, want to be part of the continuing progress made by those in your profession, and are looking for ways to participate in expanding your professional and personal experiences and skills. All of these factors are part of your continuing education, the need for peer identification or recognition, and the desire to make a specific contribution to strengthening your profession. However, you may be here with or without your company support and financial backing, unless you are self-employed. Whether you are here for the above reasons, or for many others, your presence reflects a recognition of the importance of participating in the organizational structure of your profession.

Jan 1, 1981

By H. L. Fraser

A review of the possibilities of performing microchemical analysis in thin sections using a combination of scanning transmission electron microscopy and energy dispersive spectroscopy of x-rays is given. Particular attention is paid to the factors that limit accurate analysis at the highest spatial resolution. As an example of the use of these techniques applied to a potential problem in minerals processing, the identification of iron pyrite and pyrrhotite particles in Illinois, Herrin #6 coal is presented.

Jan 1, 1981

By P. S. Daly

"The purpose of this paper is to describe the types of instrumentation used at Sherritt Gordon's Ruttan Mine to monitor the"" effects of mining. The aim of the monitoring program is to establish parameters to achieve a maximum ore recovery with minimum dilut ion in a safe environment.The copper-zinc Ruttan Mine is in northwestern Manitoba, approximately 760 km from Winnipeg (Fig . I) . Production commenced in 1973 from the open pit at the rate of 10,000 tons per day. Pit bottom lies 58 metres above the first mine level. Underground development has overlapped with open-pit mining throughout. The open pit was phased out in the latter part of 1980.Underground production began in early 1979. The mining method employed in the first lift is sub-level blasthole open stoping with delayed hydraulic filling. Large-diameter (6.5-in.) holes are being drilled in the crop stope area and are also planned for some other areas for vertical retreat mining into a slot. GeologyThe orebody consists of numerous sulphide lenses of variable size, geometry and geology . The lenses occur within volcanoclastic host rocks which exhibit a strong variability in intensity and type of alteration and structural characteristics. Stope design and sequencing were based on these complex geological factors."

Jan 1, 1981