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By Robert H. Merrill

INTRODUCTION In most cases, the design of an underground mine is based upon the premise that the ground either will cave or will be stable. This chapter concerns the design of a mine in ground that will cave readily or with some as¬sistance, such as by long-hole drilling and blasting. Some of the more widely used caving systems of mining are panel caving, block caving, sublevel caving, and large pillar recovery. Some of the less widely used systems are glory-hole, top slicing, and induction caving. Al¬though the common practice of pillar robbing is not usually considered to be a caving system, this subject will be treated as a part of this chapter. BASICS OF CAVING Caving systems are most successful in ground that will cave in sizes that will flow through openings and grizzlies, and will easily load in cars or on belts for haul¬age. The ground most likely to cave well is highly frac¬tured and contains breaks, flaws, or other discontinui¬ties that form planes of weakness. Also, caving action can be greatly enhanced if the host rock itself is low in compressive, shear, and tensile strength. Ideally, a cav¬ing system of mining is best employed when the criteria for caving is a feature of the ore body and the develop¬ment drifts, haulageways, and drawpoints can be mined in a highly competent rock beneath the mineralized zone. However, the development is often in the same, or similar, fractured rock and the openings require sub¬stantial artificial support to assure stability. Several clues can be assembled to identify potential caving ground; however, for borderline cases, no sure method has been devised to date. The diamond-drill cores taken for exploration can provide an excellent clue provided drilling is performed carefully by experienced drillers. For example, if the ground is cored in such a manner that the breaks in the core are caused more by failure of the rock than by whipping core barrels, plugged drill bits, or other drilling causes, and the intact core lengths are consistently long [say, 0.6 to 3 m (2 to 10 ft) of unbroken core], there is little reason to believe the ground will cave without considerable as¬sistance. This is especially true for rocks with compres¬sive strengths above 34.5 MPa (5000 psi) and tensile strengths above 2.1 MPa (300 psi). On the other hand, if core recovery is low (below 80%) and the recovered ore is broken in small pieces and the breaks are along obvious weaknesses in the rock, the chances are excel¬lent that the ground will cave. This is true even when the rock between the defects has high compressive and tensile strength. Another clue has already been mentioned, that is, the measurement of the physical properties of the rock and the natural planes of weakness or defects in the rock. The planes of weakness in the rock can often be detected from outcrops, cores, or other exposures of the rock under consideration. Some rock types are known to be strong and will sustain large, unsupported open¬ings and would be difficult to cave intentionally. Yet the same rock type can also contain unbonded or weak planes of weakness or fractures, and in these locations the rock would undoubtedly cave with little assistance. Therefore, although the inherent strength of the rock is a factor in caving, the natural defects in the rock are more often the deciding factor. DESIGN CONCEPTS For the most part, the design of openings for caving ground is a problem of the interaction of openings over a relatively large area of the mine. To illustrate, Fig. 1 is a simplified section of a series of openings along the grizzly level or draw level of a block caving or panel caving development, and above this opening is a simpli¬fied section of a room-and-pillar arrangement on the undercut level. At this stage of the development, the stresses around the openings on the grizzly level are only moderately influenced by the openings on the undercut level and vice versa. Therefore, the stresses around the openings are approximated by the stresses around single or multiple openings in rock, the values of which are de¬scribed in the literature (Obert, Duvall, and Merrill, 1960; Obert and Duvall, 1967). Once the pillars on the undercut level are blasted (Fig. 2), the situation changes abruptly. The undercut opening (prior to caving) now can be approximated as an ovaloidal opening above the grizzly drifts and this opening tends to shield the vertical stress field. As the caved stage is drawn the stope approximates a much larger rectangular or square opening filled with rock, and if the rock is not sustaining a major portion of the stress field, this opening can be considered (for en¬gineering purposes) to be empty and the stresses that interact between the larger and the smaller openings take on a totally new perspective (see Fig. 3). Next, let the material cave to the surface, and let the caving ma¬terial sustain some stress, but much less than if the ma¬terial were intact. This condition is similar to a soft inclusion in a rigid body and has been treated in the literature (for example, Donnell, 1941). At this point in time, the grizzly drifts are subjected to the stress con-

Jan 1, 1982

Good morning ladies and gentlemen of the AIME. I was doubly pleased when Toby Yu asked me to present to you my thoughts on the past, the present, and the future of bulk transportation by barge. My first pleasure comes from sharing with you the subject that has been my career for many years. I love this industry in the same way Mark Twain loved our rivers. Somehow, I can find in all of the activities that make up this crazy barge business the same sort of excitement that he found in "steam boating." The second reason for my enthusiasm is that Toby carefully pointed out that the presentation had to be kept to a maximum of 15 minutes. I can promise you that I will hold to his maximum time limit.

Jan 1, 1982

By L. G. Austin, P. T. Luckie, R. R. Klimpel, R. S. C. Rogers

1. INTRODUCTION The Bond method(1.2) for sizing tumbling ball mills has been used successfully for many years. The primary purpose of the Bond calculation is to predict the mill size and mill power to give a desired capacity (Q tph) from a wet overflow ball mill in normal closed circuit operated with a circulation ratio of 2.5. The input to the calculation is the make-up feed size characterized by the 80%-passing size in micrometers (xG), the desired circuit product size characterized by the 80%-passing size (xQ), and an empirical grindability number (the standard Bond Work Index) determined by a standard test. A series of empirical correcting factors(2) are used to convert the results to open-circuit or dry grinding in grate discharge mills. The Bond method has two major engineering advantages: (i) it is very simple; (ii) experience has shown that it works for many circumstances, as a reasonable approximation, because it is based on direct conversion of test data to results measured on industrial mills. There are four main disadvantages of the Bond method. First, there will be a range of error for any specific mill and material and set of operating conditions because the method does not explicitly include several variables which are obviously important: (i) recycle ratio and classifier efficiency (ii) mixture of ball sizes in the mill (iii) variations of residence time distributions with mill geometry and slurry density (iv) lifter design (v) slurry rheology (vi) different underfilling or overfilling of the mill as flow rate is changed. Second, the Bond method explicitly assumes that specific grinding energy E is not a function of ball load, whereas industrial practice and laboratory tests(3) show that the specific grinding energy (to go from a specified feed to a specified product) is less for lower ball loadings than the ball loading for maximum mill capacity. Third, the method uses only the 80% passing size of circuit feed and product to characterize the size distributions, whereas mill capacity in general must depend on the shape of the feed size distribution and the product size distribution. The prime example of this is the use of the reverse closed circuit which removes some fraction of the make-up feed before it is

Jan 1, 1982

By Robert J. Dompe

The objective of this program was to develop a cost effective microprocessor-based electronic image sensor system for monitoring pit slope displacement to detect and/ or predict impending slope failure in surface mines. A background study and data analysis yielded a performance specification for candidate Video Slope Monitoring Systems. A design concept was developed based on using a pair of solid state video cameras located on precision pointing assemblies. The digital images from the cameras are compared and, using electronic triangulation, slope topology is calculated. The current and past locations of operator selected features are compared to determine pit slope displacement. A proof-of-concept test was performed using a laboratory model of a pit slope. Based on the successful results of that testing it is recommended that an in-mine evaluation be performed using a full-scale prototype Video Slope Monitoring System.

Jan 1, 1982

By Tuncel M. Yegulalp

This final report contains the results of all work performed under BOM Grant J0333905. A preliminary systems analysis of coarse-particle coal slurry pipelines as a haulage method for longwall mining systems was performed. Two exhaustive literature surveys on state-of-the-art longwall mining and slurry transport technologies were prepared. Two representative longwall systems were designed, one with conventional haulage and one with slurry haulage. These two systems were then compared on the bases of cost, safety, and reliability. The conclusions were that for the case of a two-face longwall mine, a coarse slurry transport system does not have a clear-cut cost advantage over a conventional (conveyor-hoist) system. However, indications were that a cost advantage could occur under different analytical conditions such as: (1) a larger scale mine, (2) if intangible benefits were quantified, and (3) if new generation technology rather than currently available technology were applied to the study. Budget and time constraints prevented exploration of these conditions.

Jan 1, 1982

By R. W. Welker

A technique was developed for sampling and analyzing airborne dusts in diesel-operated, underground, metal, and nonmetal mines. Samples were taken using personal respirable samplers, operated as area samplers, and an 11-stage cascade impactor. Real-time particle size distribution and concentration measurements were made with a quartz crystal micro-balance cascade impactor and a portable electrical aerosol analyzer. The materials characterized were minerals (by XRD), elements (by XRF), particle size distribution and concentration (gravimetrically), and organic constituents (by HPLC). The method was used to characterize dusts generated at the chute pulling operations on the main haulage level of an underground tungsten mine. Analysis showed that respirable dust concentration ranged from 0.8 to 2.3 mg/m3. It consisted of silica (3-7%); organic constituents from diesel exhaust (0.11-0.31 mg/m3 equivalent airborne concentration); and mineral dust (39-100%). The remainder was diesel exhaust particles. It was concluded that size selective sampling may be used to estimate the ratio of diesel exhaust to nondiesel dusts in the respirable fraction.

Jan 1, 1982

By Richard Lusignea

A single boom roof bolting machine was outfitted with measurement and recording systems for detecting changes in machine parameters while drilling. The purpose of this instrumented bolter or "smart drill" is to detect changes in roof conditions from the machine parameters of penetration rate, thrust, rotation rate, torque, rejected light from rock cuttings, and vibration of the roof during drilling. The system was demonstrated underground in coal mine conditions and showed correlation between rock type and drilling parameters.

Jan 1, 1982

By R. J. Gunderman

A conventional trailing cable connection box on a continuous mining machine was modified by the addition of two innovative devices. These are a pressure vent to preclude buildup of high pressure due to an explosion in-side the enclosure, and a grommet-type cable entry to simplify and speedup cable entering procedures. The innovative devices were evaluated for eight and one-half months in a working section of an underground coal mine. Laboratory tests before and after the in-mine exposure show no measurable change in the devices. Following the favorable in-mine evaluation, technical performance criteria were defined to serve as the basis of approval for the use of the innovative devices. Additional tests to measure comparable gripping of the cable by asbestos rope, substitution rope materials and by the urethane grommet-type entry were included in this effort. Also, literature for the last 80 years was searched. Comments are provided as to how the innovative devices comply with 30 CFR Part 18.

Jan 1, 1982

By Corale L. Brierley

Beneficiation of phosphate in the southeastern United States generates a slurry of finely divided clay. These clay-wastes are impounded to allow the particulates to settle. The aggregation of phosphatic clay-slime wastes and slimes produced from potash beneficiation by microbial processes was studied using several bacterial species known to produce polymeric substances. Experiments included flocculation capacity of clay-slimes by whole cells, the determination of respiratory activity of whole culls in the presence of phosphatic clays, observation of clay flocculation rates by polymers derived from these organisms, and clarity of polymer-flocculated clay suspensions. The polymer-producing organisms exhibited little capacity for flocculating phosphate and potash clay-slimes. Fungal spores of Cladosporium cladosporioides (isolated from a phosphate clay-waste impoundment), when agitated with clay-slime for several days, caused the clay to form pellets. Separation of the clay/fungal pellets (density 1.1 g ml-1) from the process water might he possible using a screening technique. Studies with C. cladosporioides included the determination of suitable energy substrates and supplements for growth, absorption studies of a pigment produced by the organism, determination of the time required for bioflocculant production by the organism, and an elucidation of the conditions required for the pelletization of clay-slimes by the fungus.

Jan 1, 1982

By Robert L. Sundeen, Richard V. Wenberg

Service vehicles, often called support vehicles or auxiliary vehicles, are used in secondary functions to support production activities such as loading, drilling, and timbering. Probably the most common support vehicles are the personnel carriers used to move miners to and from work areas. Utility designs are used to transport supplies and various less mobile equipment. Specific application designs are used for special work such as explosives transportation and loading, equipment maintenance, and equipment lubrication. PERSONNEL CARRIERS Personnel carriers are available in a wide variety of sizes and configurations. Some are two-wheel drive, though most are four-wheel drive. Smaller versions carry at least two men and usually have sufficient capacity to carry a small payload of supplies or equip¬ment. The American Motor's 05 Jeep, equipped with an optional diesel engine, has been adapted successfully for this light duty. Larger personnel carriers with ca¬pacities of 12 to 20 or more men currently are available, as shown in Fig. 1. The designs often are customized to the operating characteristics of each mine. All meet the latest federal requirements for rollover protection, emergency brake systems, etc. UTILITY VEHICLES Utility vehicles are adaptable to numerous duties. Probably the most common are ordinary haulers with a flat bed or low-sided box. They are used for hauling supplies and equipment from one point to another. Some occasionally are used for towing and may pull one or more trailers. Fig. 2 shows a typical utility truck. SPECIAL-APPLICATION VEHICLES Special-application vehicles are possibly the most important of all support types since these vehicles di¬rectly support and maintain production equipment. Such vehicles are available in a wide variety of sizes, mechanical functions, and operating specifications. Most versions are four-wheel drive and articulated. Among the more common vehicles are explosive haulers and loaders, mechanic's trucks, lubrication trucks (Fig. 3), and special carriers. TYPICAL APPLICATIONS Development Utility haulers are essential in trackless operations to bring supplies to advancing headings. Some utility haulers may be dedicated to bringing in steel sets and may be equipped with boom lifts to unload heavy sup¬ports or even place them as required. A rockbolt hauler may have a boom-mounted operator's basket which can be used for bolt installation or inspection. Various mechanic's trucks and pipe trucks service the heading to keep power, air, water, and ventilation at the face and to keep face equipment at maximum utilization. Production Production operations require a variety of support equipment. Because of the larger crew size brought about by the addition of the production force, personnel carriers play a greater role. Correspondingly, steel¬support hauling equipment and bolting trucks usually see limited application. PRODUCTION UNITS Capacity Personnel carriers are available to carry almost any number of people desired. Likewise, other types of carriers or haulers can and are built to fit specific re¬quirements. Physical size, capacity, and operating char¬acteristics can be varied to fit any size of opening and operating condition. Generally, articulated models offer greater maneuverability than straight frame-axle steer designs. Most vehicles of this type are lower in power than production units, generally under 74.6 kW (100 hp). Operating performance still compares favorably to that of production equipment, i.e., the support vehicles can travel at equivalent speeds on the various mine gradients. Manpower Auxiliary vehicles should require only a single opera¬tor. Specific application vehicles may require more than one person. For example, ventilation trucks usually require a crew of two where pipe must be installed.

Jan 1, 1982

US 4,183,899 - Flow process for chlorinating ilmenite. A laminar flow of a mixture of ore, a carbonaceous reductant, and chlorine gas or other chlorinating agent is passed through a reaction zone maintained at a temperature of 1350 to 1950°C and a product stream Including titanium tetrachloride is withdrawn from the zone. The atomic ratio of carbon to oxygen in the feed mixture is greater than 1:1, and the molar ratio of chlorine to titanium solids In the product stream is between about 0 5.1 and 2:l. Titanium chlorides and metallic iron are recovered separately from the product stream. J.P. Bonsack, assigned to SCM Corp, Jan. 15, 1980 21 pp. (423-79). Filed. 3-10-78 (885,442).

Jan 1, 1982

By R. L. Armstrong, C. I. Godwin, V. M. Kruan

"The Scheelite Dome tungsten-bearing skarn property, central Yukon Territory, is in metasediments in contact with a quartz monzonite intrusion. Contact metamorphism to biotite-muscovite- andalusite hornfels and calc-silicate hornfels is superimposed on low-grade regionally metamorphosed rocks represented by quartz-mica pelitic schist and muscovite-biotite pelitic schist.Metasediments are likely Precambrian in age, even though Rb-Sr whole-rock analyses indicate an early Paleozoic age (511±41 Ma); this apparently too young radiometric age is due to partial loss of radiogenic strontium during regional metamorphism. The minimum age of the quartz monzonite intrusion is Cretaceous at 90.4±2.6 Ma (K-Ar on biotite) and its initial 87Sr/86Sr ratio is 0.7121. The high initial ratio of the intrusion is due to the addition of radiogenic strontium from the metasedimentary country rocks and perhaps an underlying older basement.Scheelite-pyrrhotite-chalcopyrite mineralization occurs in diopside-zoisite skarn pods within the calc-silicate hornfels near the quartz monzonite intrusion. The source for lithophile tungsten is probably the same as for the granitic magma, namely Precambrian sialic basement.IntroductionThe Scheelite Dome tungsten skarn property is within the Mc-Questen map-area (NTS: 115P/16),28 km northwest of Mayo, Y.T., at latitude 63°47' north and longitude 136°15' west. The property can be reached by helicopter or by four-wheel- drive vehicle from Mayo.This paper summarizes the geology of the Scheelite Dome property, which has been described in a general way by Little (1959) and Cathro (1969). Geological mapping and sampling were done by the first author (nee Steffler) during June 1979. Field work was supplemented with detailed work at the Department of Geological Sciences of The University of British Columbia during 1979 and 1980 (Steffler, 1980). Whole-rock chemical analyses were done by Cominco Ltd."

Jan 1, 1982

By Robert R. Turner

This paper discusses wet and dry primary autogenous and semi-autogenous grinding, including a description of the equipment and its mode of operation, testing and the scaling-up of test data. Lists of selected literature references are included.

Jan 1, 1982

By Robert J. Pokora

This report summarizes the work performed under USBM Contract No. J0100038, "Demonstration of Noise Control Techniques for the Crushing and Screening of Nonmetallic Minerals." The objectives of the program were to: a. Identify the prevalent sources of crushing and screening noise in portable and stationary plants b. Design retrofit noise control treatments for those sources c. Field test control treatments under actual operating conditions. A census of the nonmetallic industry was performed to determine the number and types of crushing and screening equipment. Based on the census, eight plants were selected and surveyed to assess the variety of noise sources, determine the worker noise exposure to those sources, and to identify possible constraints that had to be considered in designing and installing the retrofit controls. Three plants were selected from those surveyed and retrofit noise control treatments were designed, including: a. A primary crusher operator control booth b. Screen decks made of resilient cloth c. Screen feedbox impact pads d. Rubber feed plate for secondary crusher e. Rubber feed chute linings for secondary crusher f. Noise attenuating curtain for secondary crusher. A new primary crusher control booth was installed at one plant, and the operator noise levels were reduced from 97 dBA to 78 dBA. Screen noise at the two secondary crushing plants was reduced by 3 dBA to 7 dBA; crusher noise was reduced by 5 dBA at one of these two plants. Noise levels at normal outside operator and cleanup locations were reduced by 4 dBA to 7 dBA at one secondary plant, but operator/cleanup noise levels were not significantly reduced in the second plant due to rapid wear of installed materials. At one of the two secondary plants the retrofit noise control materials displayed excellent wear characteristics. The rapid wear of retrofit materials at the second plant was due to improper materials being supplied and changing circuit conditions.

Jan 1, 1982

By E. Concha

The concept of an Automated Continuous Explosive Excavation system (ACEE) for the underground mining applications of development drifting and room and pillar mining has been evaluated in comparison with conventional drill, blast and muck operations. The role and possible extent of application as this method was identified. The evaluation examined each element of existing and of proposed ACEE design concepts in a defined mine environment. Step by step procedures were developed to quantify the evaluation process where this appeared feasible. One conclusion drawn was that a system approach to ACEE design is not only feasible but attainable within the state of the art. Several preliminary design concepts were formulated and examined in order to determine what further research or development might be needed to realize them.

Jan 1, 1982

By L. A. Morely

The overall objective of the subject contract was to investigate the application, economic, and safety considerations of electrical-shock prevention techniques applied to surface and underground mines. Volume I of the four-volume final report starts by summarizing all research performed, and synopses of the three other report volumes are included. The balance of this volume concerns one major task of the contract, the protection of maintenance personnel. After specifying the scope of work for the task, electrical is defined, and needed ground-fault relay characteristics to prevent ventricular fibrillation are established. This is followed by an analysis of alternating-current systems, a comparison of these systems with respect to body currents, and the advantages and disadvantages of the various ground-fault protection techniques. An analysis of direct-current systems for off-track vehicles is then covered. These analyses form the basis for the research recommendations which along with suggestions for future research, conclude the report volume.

Jan 1, 1982

By Linneas W. Laage

Coal production from underground coal mines has been important to the development of the industrial economy of the United States. Environmental problems have developed from some abandoned operations. These problems include: mine and refuse pile drainage, subsidence, unsafe mine openings and to a lesser extent mine gases, slope stabilities, mine and refuse pile fires and abandoned equipment and structures. Field investigations in three eastern coal mining districts, two in Ohio and one in Illinois, were performed to document the mine closure procedures used and subsequent problems that developed. The purpose was to identify, evaluate, and rank the seriousness of these problems. Based upon this evaluation, the undesirable present day situations could have been avoided or at least minimized by varying certain mining practices or mine closure procedures. It was found that federal regulations address all of these problems during the pre mining, active mining and post mining phases except for abandoned equipment which is the least threatening problem category. Ideally current practice would prevent future problems. However, the extensive and complicated nature of the legislation, environment and mining practices will necessitate adjustments to the law. The investigator recommends the following: 1) Goal oriented legislation encouraging complete resource extraction, standardization and compilation of mining generated hydrological data, periodic review of the coal mining regulations, and improved communication and cooperation between coal interests, regulators and the public. 2) Permitting effluent limitations to accurately reflect natural conditions. 3) Solidly back filling shafts and individual assessment of sealing or capping requirements. 4) Installing shaft vent pipes into the fill material to intercept and vent methane.

Jan 1, 1982

By S. K. Mathur

This report identifies all the possible activities, variables and factors that contribute to the surface subsidence process over room and pillar workings. These factors are responsible for mine instability and collapse that ultimately transforms into surface subsidence. Such a failure mechanism is initiated by the failure of the mine floor bed and or the failure of the pillars or the failure of the roof after second mining, which eventually brings down the roof. The individual responses of the pillar, floor and roof rocks to the mining induced stresses and the complex interaction between these components can't be attributable to any single factor. Also, no attempt has been made to quantify the significance of each of these factors and relate to the ground subsidence due to the lack of field data. The discussion here is centered primarily on the first mining though second mining is mentioned very briefly,

Jan 1, 1982

By William M. Hinton

This report describes the approach, procedures, and results of a program to develop training materials for roof bolter operators. The objective of the program was to design and produce a training sequence which would prepare roof bolter trainees for job performance. Data was collected and analyzed using the general procedures of Instructional Systems Development (ISD). Input data came from a previous roof bolter training analysis program. This data was expanded and structured through a series of ISD steps: objectives hierarchies, media selection, syllabus, lesson specifications, and train¬ing materials development. The resulting program consisted of an ordered sequence of 15 lessons. The media mix for the 15 lessons included lectures, slide-tape lessons, and hands-on instruction using operational roof bolters. Contents of all lessons were reviewed and approved by the Bureau. The key recommendations were to (1) validate the materials and measure relative effectiveness of media formats; (2) survey mines for training resources and conditions - match materials to user capabilities, rather than selection state of the art technology/media; (3) develop job performance aids (JPAs) rather than simulators; (4) create a style/media/JPA development guide for use in future projects of this kind.

Jan 1, 1982

By E. K. Stanek

This research study was performed on a case study basis and can be divided into two parallel thrusts: electrical and thermal energy conservation. Energy consumed annually in mining and refining operations represents about 6% of the 80 quadrillion Btu's consumed nationally. In the electrical portion of the study, five areas were addressed: optimal dispatching of on-site generation, high-efficiency motors, conductor selection, power factor correction, and high efficacy lighting. In the case study mine which has a multiple unit on-site generation system, optimally dispatching units can save significant energy. The other four methods are difficult to justify on a retrofit basis due to capital costs. In the thermal portion of the study, a thermodynamic analysis was performed on the reverberatory smelting process possible areas of energy conservation were identified as radiation and convection heat losses from the furnace arch and the dumping of high energy content smelting slag. It has been shown that materials currently available can provide the means of reducing heat loss from the reverberatory furnace. It has also been shown that a significant amount of energy may be recovered from the slag. However, these are both subject to further study and validation.

Jan 1, 1982