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By R. Karl Zipf, Z. T. Bieniawski

"Fracture mechanics plays an important role in studies of geologic materials such as rock and coal. Yet fracture data are scarce for rock and most limited or unreliable for coal. A testing system was developed which can apply mixed mode loads to a crack tip in many rocks and geologic materials. It is possible to subject the test specimen to pure mode I, various mixed modes and a nearly pure mode II fracture load. The system is currently used to study the mechanics of fine fragment formation in various coals. Experimental measurements include KI and KII' fracture velocity and acoustic emission.INTRODUCTIONA major research program at The Pennsylvania State University is directed to understanding the fundamental mechanics of fine fragment formation in various coals. The program represents an effort to reduce the incidence of coal workers pneumoconiosis (black lung) in coal miners. The principal source of the respirable coal fragments is the cutting operation which forms and liberates the particles by a fracture process. Present understanding of the mechanics of the events which form and liberate these particles is meager (Cook, 1982).Current knowledge of the fundamental mechanisms of coal dust generation and entrainment in terms of the underlying fracture mechanics is critically needed to improve and possibly control the processes involved. Whether the cutting operation is done with a 'continuous miner' cutting machine, a plow or a longwall shearer, it is fundamentally a problem of mixed-mode crack propagation. When a cutting tool interacts with coal, it causes numerous cracks to propagate through the intact material. Numerous larger fragments are broken free, but another quantity of undesirable fine fragments is also created. The formation of these respirable fragments may be a direct result of the crack propagation process; hence, a thorough understanding of the fracture mechanics of coal is required to minimize production of the unwanted fine fragments.In most rock engineering applications, the rock material properties are of secondary importance to the rock mass properties; however, for rock fragmentation and rock cutting problems, it is rock material properties such as fracture toughness which are of prime interest (Bieniawski, 1980). Several rock cutting and rock failure theories have been proposed, but it is only very recently that fracture mechanics concepts have been successfully applied to the study of rock cutting mechanics. All cutting models seek to predict the cutting forces and the cutter geometry necessary to cause rock breakage and chip formation given some fundamental mechanical properties ~f the rock. Such models have wide applications in drilling, tunnel boring and mining problems. Nelson et al., (1985, 1986) has provided a very useful correlation between the laboratory measured fracture mechanics properties of rock and the performance of the disk cutters on tunnel boring machines."

Jan 1, 1989

By Luis E. Vallejo

The strength measured by the uniaxial compression test is a parameter that is widely used for the engineering classification of rocks. Sedimentary rocks such as shales, however, are difficult to evaluate by uniaxial compression tatting because the rocks slake during the preparation of the standard samples required for the tests. Indirect methods such as the point load test have been proposed to determine the unconfined compressive strength of shales and other soft rocks. It is current practice to use 24 as the conversion factor between the point load strength, Is, and the unconfined compressive strength, sf (sf = 24 Is). The present study investigated index-to-strength conversion factors for shales and sandstones obtained from surface coal mining sites in the Appalachian region. Regression analyses indicate that a conversion factor of 12.5 best correlated the strengths obtained from the point load and unconfined compression tarts in the case of shales. For the sandstones, a value of 17.4 best correlated the strengths.

Jan 1, 1989

By David L. Shearer

INTRODUCTON James Howden first secured an order for two Service Tunnel Boring machines in November 1986. These Tunnel Boring machines were 5.7 and 5.4 metres in diameter and the full length including back up was 215 metres. Manufacture commenced in December 1986 at the Glasgow factories of James Howden & Company with the deliveries to site of the machines in September 1987 and March 1988 respectively. In December 1987 two further orders were secured for the land running tunnels at 8.7 metres diameter. This paper presents some of the challenges in building tunnel boring machines for the Eurotunnel project between Britain and France. The general specifications of the Tunnel Boring machines and length of drives are shown in Appendix 1. DESIGN PARAMETERS The specification given by the Consortium TML on behalf of their client Eurotunnel cleary indicated that cutting of the face should be concurrent with the building of the precast concrete lining rings. In order to do this a telescopic machine was thought to be the best solution. Ground conditions were described as chalk marls of homogeneous nature with the possibility of friable areas and some revelling. A shielded type TBM with open cutter head was chosen together with a telescopic section and a rear

Jan 1, 1989

By Jerry E. Olson

In 1988, at the request of the Bureau of Land Management, the U.S. Bureau of Mines studied additional areas, encompassing 11,303 acres, on the east and west sides of the 20,727-acre Badlands study area (Olson, 1987) in order to evaluate their identified mineral resources. The Badlands study area additions are located in Crook and Deschutes Counties, OR, about 10 and 18 miles east of Bend, OR. No mineral resources were identified. The additional areas studied are underlain by Tertiary-and Quaternary-age basalt flows which are largely covered by a veneer of sand and silt. No mines, prospects, mining claims or mineralized areas occur within or near the Badlands study area additions. Slab lava of marketable grade and quantity was not found in either area. None of the study area is of current interest for geothermal resources, but the eastern study area addition has been leased (1984) for oil and gas.

Jan 1, 1989

By Jasinder S. Jaspal

Most of the underground coal in the United States is mined via room-and-pillar mining methods with continuous miners. These machines operate intermittently because they have to wait for shuttle cars to interchange positions. To overcome this discontinuity in shuttle car haulage and to realize the full production potential of continuous miners, the U.S. Bureau of Mines developed a multiple-unit continuous haulage (MUCH) system through a research contract with Jeffrey Mining Machinery Div. (JMMD). The MUCH system consists of 12 rubber-tired vehicles and a bridge conveyor. The rubber-tired vehicles are connected by a unique mechanical linkage system to form a 250-ft train. The mechanical linkage permits the vehicles to track-retrack the preceding vehicle in both inby and outby directions. The cut coal cascades from one vehicle to another until it is discharged on the section conveyor belt. The MUCH system provides continuous haulage to the continuous miner. The MUCH system was initially surface tested by JMMD. Subsequent extensive testing was conducted by the Bureau at its test facilities at Bruceton, P A. Deficiencies found during testing were corrected. This report summarizes initial tests by JMMD and subsequent extensive tests and evaluation by the Bureau.

Jan 1, 1989

By Laxman S. Sundae

A U.S. Bureau of Mines designed and fabricated in-seam tester (1ST), retrofitted with a dust shroud, was used to establish a respirable dust index (RDI) and to determine cutting forces from a variety of bit types in four coal mines and a salt mine. Results from cutting tests at four coal mines showed that radial bits required the lowest cutting force and the least specific energy. Generally, for each conical bit the RDI and cutting force increased when the included bit tip angles increased from 70° to 90°. During field tests it was not possible to measure the total quantity of respirable dust produced by each cut; therefore, attempts were made to determine the amount of dust that became airborne from each test cut. The test results show that the quantity of airborne respirable dust is very erratic and cannot be related to bit type. Two statistical methods were employed to analyze RDI, but no correlation was found between the RDI and bit type. Despite scatter in test results for RDI, significant difference was found in RDI generated in four coal seams. In general, RDI increased with the increased cutting force for each coal seam from mine 1 through mine 4.

Jan 1, 1989

Between 1985-1986, the Bureau of Mines reviewed the mining history and minerals information for areas in and near the San Isabel National Forest to appraise the mineral resources present and determine the types of deposits, and their location in the Forest, that could be mined economically if sufficient demand and metal prices existed. The two major metallic deposit-types that are of national mineral resource significance within the Forest are stockwork- molybdenum (with tungsten and tin) and carbonate-replacement zinc-lead-silver deposits. Historically, small gold placers, gold-quartz veins, silver-quartz veins, skarn iron and copper deposits, volcanogenic copper-zinc-precious metal deposits, and base- and precious-metal veins have been mined. Barite, carbonate rocks, gypsum, other non-metallic deposits, and pegmatites, have also been mined. Sand and gravel, present in large volumes, occurs along and has been mined outside the Forest along the upper Arkansas River valley. Turquoise and gemstones are present in small amounts and are of interest to collectors and jewelers. Geologically, sediment-hosted uranium and copper are present in small occurrences but no resources have been identified. Geothermal resources are related to the Rio Grande rift which parallels the central part of the Forest. Four hot spring areas are present - two of these are within the Forest. Because of the low power requirements of the region, and the presence of other generating facilities, these geothermal resources have had only limited local use. Evaluation of mine models that may be found in the region show that base-metal deposits require a high precious-metal component to be economic. Although molybdenum can be produced at economically competitive prices, there is little demand for the product. Capital costs to start new molybdenum mines would be very high and it is not likely that new mines will be put into production in the near future.

Jan 1, 1989

By A. M. P. Henderson

Twelve members of the Witbank/Middelburg Branch, on a technical excursion, were hosted by the Technical Department, Pinelands site, of AECI on 10th February, 1989. The tour opened with some well-presented talks on 'Permitted Emulsion Explosives', and the application of the 'French' test to the development detonators.

Jan 1, 1989

By James R. Arnold

Gold Fields Mining Corporation started processing ore from it's Chimney Creek operation in northern Nevada in November, 1987. Since that time production has averaged about 200,000 ounces per year from the milling and dump leaching circuits combined. The events that led up to commissioning of the plant started in January of 1985 when the Gold Fields exploration team drilled their first hole in an area now known as Discovery Hill. The major orebody was located later in the year in what is currently the major focus of activity, the North Pit. Subsequent drilling since plant startup has found another 14 million tons of ore two miles south of the original orebody. This South Pit orebody is currently being stripped and metallurgical testing is underway. Engineering Engineering on the Chimney Creek plant started in earnest in May, 1986. Davy McKee Corporation from San Ramon, California, did both the engineering and the construction management. Before engineering began the entire senior staff of the Plant Department was hired and assigned to the project. Senior staff included the Plant Superintendent, Plant General Foreman, Maintenance General Foreman and Chief Metallurgist. Gold Fields does not employ an internal central engineering staff to design their plants. We feel that the people who design the plant should be the ones who will be required to run it once it has been commissioned. This philosophy affords a continuous accountability from start of design through commissioning and operations. All four of the senior staff spent the most critical phase of the engineering stage at Davy McKee, so the plant is truly a reflection of all four disciplines. In bringing on the Maintenance General Foreman from the start, there was a focus placed on ease of maintaining the plant. Another philosophy that was adopted from the start was that the plant be easy to work in and maintain for both operators and maintenance personnel. Numerous design criteria were given to Davy McKee to ensure this. For example, we required that every piece of equipment could be reached easily with a crane or fork lift. All conveyors were required to have walkways on both sides for ease of maintenance and a minimum of 30 inches of clearance under them for ease of cleanup. Visibility for operators was considered very important and the control rooms and general plant layout were designed with this in mind. A list of about 100 general rules were given to Davy McKee during the early layout meetings and these were held as the general design criteria throughout engineering and construction. While engineering was progressing in San Ramon, California, dump leach test work was being done at the site. Three 6 foot diameter fiberglass columns were constructed and filled to a 20 foot height with low grade ore. Leaching characteristics were determined and the dump leach design was based on information collected from these columns. Construction The major contractors on the project were The Industrial Company for the bulk of the piping and structural, EMKO on the electrical/ instrumentation and Hunewill for most of the earth work and leach pad construction. All plant operating and maintenance personnel were employed eight weeks before startup for intensive training. Instructors were Gold Fields personnel, including foremen, and Davy McKee engineers. On occasion, selected suppliers representatives were brought in to discuss major pieces of equipment. Project completion was targeted for January, 1988 at a projected cost of 78.9 million dollars. Actual startup was about 1 1/2 months ahead of schedule and slightly under budget. Full design capacity was achieved the first full month of operation. Crushing Run of mine ore is delivered to the crusher and dumped into a 90 ton hopper which is topped with a 30" X 30" opening stationary grizzly. Ore is fed to a 50" X 60" Telsmith jaw crusher with a 5' wide apron feeder. The closed size setting of the

Jan 1, 1989

By Pentti Kallio

From the aspect of economic feasibility of mining, ineffective use of expensive mechanization investments is becoming a problem. In many cases, the machinery is in operation only 50 - 60 % of the total working time. The lost time when the machines are idle means a considerable over-investment in machines. The lost time, with LHD equipment in particular, accumulates from the following constituents: - the needs of the person operating the machine trips to the work site, lunch, coffee and other breaks, want for comfort, etc. - deficiencies in the monitoring and control systems for machine operation waiting periods at loading and unloading stations, unnecessary and erroneous actions, inefficient work, etc. - deficiencies in the machine condition monitoring system , and inefficient service and maintenance work The data transfer and computer technology of today provides means for resolving problems in several areas - including the area of underground loading operations. In the paper those areas of automation and data handling are considered which make possible an improvement in the usage and monitoring of LHD equipment. These fields are: remote control of equipment, use of TV cameras and monitors in remote control, locating equipment and data transfer down the mine, measurement of the load and the data storing system, systems for following the condition of the equipment, unmanned operation of equipment.

Jan 1, 1989

By G. R. Larocque

"The Loss Prevention Program and management style applied at Kidd Creek enabled them to maintain a 1.02/200 000 man-hours accident frequency over a 20-year period. Falconbridge Limited, Kidd Creek Division operates a major zinc, copper, silver mine, two gold mines and a metallurgical facility in Timmins, Ontario. The metallurgical site and the base metal mine are 17 miles apart and joined by their own railroad. The minesite consists of two shafts, one 3000 feet deep and the other to 5200 feet deep, as well as the necessary maintenance and service shops. The metallurgical site consists of a 14 000 STPD concentrator, a zinc refining plant, copper smelter, copper refinery, and the necessary maintenance shops. The two gold mining operations are adjacent to the metallurgical site.At the time of writing this paper the workforce consisted of some 2500 people divided between the two sites. Nine hundred and ninety-two employees are stationed at the minesite, with the remainder at the metallurgical site and gold mines. The workforce in the Timmins operation is non-unionized and reflects the belief that employee interests are well served.Beside providing competitive wages and an excellent benefit package, Kidd Creek takes special pride in its employee relations practices and continued efforts in communication.In each of the programs referred to, there have been equal involvement by both management and the employees. Each crew, under the direction of a supervisor, makes up its own health and safety committee. To maintain a successful Loss Prevention Program, it is essential that management and the employees work closely together and provide meaningful input and effort to succeed.At this point, refer to the lost time injury frequency as a measure of failure and refer to the opposite end of the scale as the measure of success. The ultimate goal of every operating company is to have a zero frequency, therefore denoting 100070 success. The company uses most of the tangible safety aids found in other mining operations, such as safety posters, safety reminders, check lists, and the use of the Neil George Safety System. The difference is the manner and style of management at the Kidd Creek Division. Their ""open door"" policy and the close association, between management and the employees, has always served them well. Also, at Kidd Creek they believe they have a well-trained and dedicated workforce."

Jan 1, 1989

By Timothy M. Barton

The U.S. Bureau of Mines is conducting research to assess the effectiveness of different chain pillar designs in maintaining gate entry stability. A particular concern is ground control for deep-cover 1ongwalls located at depths in excess of 1,000 ft. The study described in this report was performed in two experimental sections in one longwall headgate section which contained three different pillar designs. Two of the designs used conventional abutment pillars, while the third was a total-yielding pillar system. Both of the test areas were located under 1,800 ft of cover. The purpose of this study was to evaluate the effectiveness of these three pillar designs for gate road stability. As the longwall mined passed the test areas, Bureau engineers monitored entry convergence, roof sag, and changes in roof quality. The study indicated that the all-yield system performed nearly as well as the better of the two abutment pillar systems; but all of the three designs would have failed to provide acceptable stability for second panel mining without considerable artificial support.

Jan 1, 1989

By Gerhard Sauer, Heimo Gold

The main advantage of the New Austrian Tunneling Method over conventional drill and blast techniques, TBMs and shields is its outstanding flexibility. Many different support concepts help to cope with all but the most adverse conditions. A considerable variety of unique additional support measurements provide a functional tool when dealing with particularly difficult conditions or restricting requirements. The resulting adaptability of NATM with respect to geometric and geologic changes is a cornerstone to providing an economic design and to a safe and unhindered execution of the tunnel work. To take best advantage of this flexibility and to emphasize its cost-saving capacity, NATM explicitly extends the design period into the construction phase. In accordance with corresponding ground classes or other anticipated conditions, a number of basic support categories and an array of additional support measurements are established during the actual design phase. The decision for applying a particular support category at a specific location and for necessary additions to the given support scheme, however, is regularly made on site after each advance, and is determined by the key persons involved in the construction. Contract documents must reflect this approach to facilitate the execution of the work and to curtail construction costs. Biased distributions of risks, however, can adversely effect the envisioned benefits. Consequently, the respective responsibilities of engineer, contractor, and client need to be redefined.

Jan 1, 1989

By P. C. Lighthall, D. W. Zandee, W. Shukin

"IntroductionThis chapter deals with the on land disposal and storage of fine tailing in slurry form behind dams. Other types of tailing, such as coarse dry cobbs from magnetic separation of iron ores and other dry materials, have special problems and are not addressed in this paper. The disposal of mine waste is not included, except as such materials may be of value in the construction activities related to tailing disposal.In earlier North American mining, mines were smaller and frequently disposed of their tailing by direct discharge into neighbouring streams or bodies of water. Where that was not practical or not permitted, the solids were collected in tailing ponds and only the effluent liquids were released or decanted. The dams used for these early impoundments were fragile structures and failures were common. With the advent of large, low-grade open pit mines, and increasing awareness of environmental and safety considerations, recently established mines have carefully-designed tailing disposal systems, with wellconstructed dams and attention given to protection of the environment. Older mines are being improved or at least being examined critically with a view to upgrading as necessary to meet the new standards.Modern tailing disposal systems are highly variable and unique to each mine. Tailing pond selection and design is dependent on available topography as also is the design of transport and water reclaim systems. Suitable sites that are at higher elevations than the mills or distant from them may require that the tailings be pumped. Dams, either earth or rock structures built of the most convenient and economic material, are usually a suitable mix of local borrow, mine waste and coarse tailings. The most economic structures are those built mostly of coarse tailing."

Jan 1, 1989

By W. R. Junge

The investigation, selection, and implementation of remedial activities for large, complex mining and milling sites is dependent on the cost-effective management of tailing and waste materials. Site investigations evaluate the contaminant source areas, assess the potential release rate of contaminants, and determine the acceptable contaminant release rate for the site. Selection of appropriate remedial activities is based on evaluation of constructability, reliability, performance, effectiveness, permanence and cost. Remedial technologies available for tailing and waste material include removal, consolidation, capping and drainage control. Proper implementation and documentation of the selected remedial activities are critical to the overall success or failure of the remedial program. A step-by-step process, established at the initiation of a project, should accurately document all construction activities, monitor environmental conditions at the site, assess the performance of the remedial activities, and, ultimately certify that the remedial activities have met relevant and appropriate standards. Case histories are presented for a uranium mill at Uravan, Colorado and a lead, zinc mine at Gilman, Colorado. These case histories provide examples as to the combination of remedial technologies that have been applied at these specific sites.

Jan 1, 1989

By C. W. Smith

The U.S. Bureau of Mines conducted research to determine the effect of ground water control on the dewatering of phosphatic clay wastes. Two storage impoundments were constructed. One impoundment was surrounded on three sides with a series of well points (shallow vertical wells) to lower the ambient water table and the second impoundment served as a control. Ground water was pumped from the area surrounding the test impoundment for a period of 490 days. A constant pumping rate of 60 gal/min resulted in a water table drawdown of 13 ft, approximating the bottom of the impoundment. At the end of the test period percent solids in the test impoundment was 35 pct, while in the control impoundment percent solids was only 26.8 pct. Percent solids of greater than 30 pct is required for capping and final reclamation using fertile overburden.

Jan 1, 1989

By G. W. R. Kuzyk

The Underground Research Laboratory (URL) , a major geotechnical research facility, is currently being developed by Atomic Energy of Canada Limited (AECL) , 120 km northeast of Winnipeg, Manitoba. The URL is part of the Canadian Nuclear Fuel Waste Management Program, which is assessing the concept of nuclear fuel waste disposal in a vault deep in stable plutonic rock of the Canadian Shield (Simmons, 1986). Comprehensive geotechnical research and development activities are being carried out in conjunction with excavation? and construction of the underground facilities.

Jan 1, 1989

By Larry A. Lass

The U.S. Bureau of Mines, in cooperation with the Iron Range Resources and Rehabilitation Board, investigated the potential of using northeastern Minnesota papermill waste sludges as a binder for Mesabi Range iron ore (taconite) concentrate. Sludges from five different commercial papermill waste treatment operations were evaluated in laboratory tests. Except for the coarsest sludge, all were fairly easy to blend with the taconite concentrate using conventional mixing methods. The coarsest sludge had to be reslurried at 2 pct solids before adding it to the concentrate in order to obtain pellets without visible sludge clumps. Drying and grinding the sludges made them less effective as binders because of a lower degree of rehydration. On a dry weight equivalent basis, twice as much raw sludge binder was required to obtain similar pellet physical properties as with bentonite; however, the pellets made with raw sludge had superior metallurgical properties. Over 30 pct higher reduction rates and over 1500 C higher softening temperatures were obtained with sludge binder than with bentonite. Sludge D, which had the lowest fiber and the highest alkali metal content, resulted in the lowest reducibility enhancement. Even though more raw sludge was required than bentonite, the sludges have virtually no value, and therefore may provide a cost-effective additive binder for producing improved metallurgical-quality pellets. Large-scale testing has not been done to confirm these laboratory results.

Jan 1, 1989

By J. Peshel

This paper presents a regulatory perspective of the design and construction of the Exploratory Shaft Facility which may become part of the future high-level waste repository. Site characterization concerns and long-term waste isolation concerns require the consideration of various shaft design and construction aspects quite different from that of conventional shaft sinking.

Jan 1, 1989

By George H. Schnakenberg

Automation of coal mining activities at the face offers improvements in worker safety, health, and productivity. Introduction of integrated computer-sensor systems to current mining machines will enable these machines to perform some of the most hazardous tasks through supervised teleoperation. The U.S. Bureau of Mines is pursuing the development of the enabling technology necessary to achieve this goal. The research program consists of both basic and applied research, each focused on the fundamental issues of computer and sensor technologies. Short-term research is directed to providing computer-assisted, remote supervisory operation of present underground equipment; the long-term goal is the development of progressively more intelligent mining systems. The research program includes a review of robotic machine and autonomous vehicle technologies and of current mining technology, which provides a base for developing innovative mining methods; research in navigation and guidance technology, emphasizing control of a continuous mining machine; research on coal-rock interface sensing technology for horizon control, and rib thickness control in highwall mining; the development of computer systems and hierarchical architectures for real-time control; and development of expert systems for machine system fault diagnostics and predictive maintenance. This report presents a brief background and the current status for each of these research areas.

Jan 1, 1989