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By L. H. Munson, E. H. Carbaugh, D. E. Hadlock, L. F. Munson, R. L. Gilchrist

As a result of the Three Mile Accident and because of evidence indicating radiation protection problems, the U.S Nuclear Regulatory Commission (USNRC) undertook a major effort, with the assistance of the Pacific Northwest Laboratory (PNL), to analyze radiation protection programs at 47 commercially operated nuclear power plants. This effort, the health physics appraisal program (HPAP), using a modified management oversite and risk tree analytical logic methodology (MORT) which consisted of analytical trees with applicable questions for each tree, was subsequently extended to include USNRC licensed uranium mills. In the uranium mill appraisal, a team of four senior radiation safety professionals spent a week at each mill evaluating the total health physics program. Prior to the HPAP, the USNRC inspection efforts were designed to determine if the licensees were fulfilling the requirements of the code of federal regulations and the mills source material license. The HPAP, however, was designed and structured to facilitate an integrated look at the total program. It is also directed into areas for which explicit NRC regulatory requirements may not currently exist. The latitude of the HPAP was designed to allow professional judgement in the evaluation of program adequacy, because merely meeting the explicit regulatory requirements does not necessarily ensure an adequate and effective health physics program. The results of the first eight site visits and the generic health physics problems identified within the uranium milling industry will be identified in this paper.

Jan 1, 1981

By Lennart Bergstedt

Boliden Aktiebolag, the prime base metal mining company of Sweden, annually treats some 11-12 million tons of sulphide ore in nine concentrators. Its first flotation plant was established in the early thirties for the complex Boliden ore. Since then, the number of mines and plants has gradually increased. Considerable effort has been devoted to the development of all phases of the technology of ore prospecting, mining, milling, smelting and refining. This has been necessary due to the complex and low-grade ores. The development of concentration has mainly been directed toward the arts of grinding and flotation. During the forties and fifties, open-stage fine crushing followed by two-stage grinding in rod and ball mills with cyclone classification was successfully introduced and used throughout the plants. The increasing cost of grinding media led to studies of an autogenous grinding technique as early as 1945. Basic test work commenced during the early fifties, with a. number of ores tested for pebble grinding. In 1956 a new pilot plant was built, with equipment installed for the continuous testing of pebble grinding and, later, for primary autogenous grinding of run-of-mine ore. The intensive test work showed that pebble grinding was feasible in almost all of the plants. At this early stage of testing, however, the merits of autogenous grinding could not be fully evaluated. As a. consequence the rod mill/ball mill grinding systems were converted to rod mill/pebble mill systems whereever possible. In parallel with the converting of grinding systems the development work concerning the merits of autogenous grinding went on. The major result

Jan 1, 1977

By Edmond O’Donovan

Mooranbah North is a new greenfield project in Australia's Bowen Basin that is projected to produce 4 mtpa of hard coking coal from a single longwall. Located in Central Queensland in Australia's northeast, this is one of Australia's main coal producing regions. From the outset, Mooranbah North's approach to equipment selection has differed markedly from that usually taken in the mining industry, and the conveyor industry in particular. Until recently, no performance requirements have been placed on conveyor equipment suppliers. This arose from a practice of purchasing components in an ad-hoc manner from a variety of sources, and the mine then configuring the system. More recently, single source supply has been adopted as a means of obtaining some performance guarantee, usually expressed in terms of system availability. Unfortunately, the term "availability" has a multitude of definitions, particularly in the underground coal sector. A conveyor availability of 98% is a common goal but this rarely means the conveyor must operate 165 hours/week, 52 weeks/year. There are mines that have one maintenance shift for each production shift and claim availability of 100%. What is meant is that no down time is logged to the conveyor during the hours that it is wanted. This "generous" definition of availability would not be tolerated in many industries and nor should it. Unfortunately, a true definition of availability, such as is applied to steam turbines in the power generation industry, is not particularly helpful. Five day/ week operations would immediately face a 28% penalty against 7 day rosters, and there would be no sensible manner in which weekend maintenance could be incorporated into the availability formula. The approach adopted by Mooranbah North was to specify a period of "Failure Free Operation," which would be followed by a maintenance period. This

Jan 1, 1998

By T. B. Linde

The Morenci In-pit Crusher and Conveyor System has been designed with safe production and cost savings in mind. Large open pit mines around the world have been installing semi-mobile crushers and linking them with a pit conveyor system to lower unit cost. At Morenci two 60/89 in. gyratory crushers are incorporated into the semi-mobile crushing plants. The ore is reduced to -8 in. and transported out of the mine on a 60 in. steel cable belt. This paper includes an overview of the Morenci In-pit Crusher and Conveyor System from the drawing board to open pit installation and finally a discussion on operating and repair considerations.

Jan 1, 1990

By J. A. Cole

The mill project at Lone Tree was commissioned in October, 1993, followed by the commissioning of the autoclave pressure oxidation circuit in February, 1994. Discussion of the first year of milling operations at Lone Tree is presented. The mill is currently operating above the design rate of 2,267 mt/d (2,500 st/d). Both phases of the start-up were essentially trouble free. The few problems that were encountered and the respective solutions are addressed.

Jan 1, 1995

By M. J. Laurila

Elemental analysis of slurry streams using X-ray fluorescence (XRF) has long been employed. However, detector technology has limited the application of XRF devices. Using detector technology employed on NASA's Mars Pathfinder to analyze soil samples, Process Control, Inc. has developed an on-line analyzer to mount on a sampling system. The prototype XRF elemental analyzer was installed at Detroit Edison's Monroe Power Plant in January, 1998 and has been employed to monitor feedstock quality. A slurry system has been developed for flotation control. This paper describes the testing of the analyzer using the new, draft ISO standard for evaluating the performance of on-line analyzers (ISO/DIS 15239).

Jan 1, 1999

By R. S. Datta

Regulations on sulfur emissions have caused the electric utilities to evaluate various methods of meeting them. Low-sulfur, low-volatile coals can be burned alone or blended with high-volatile? coals. This option may be a cost-effective alternative to the installation of scrubbers on coal-fired combustion systems. In some blending applications, problems may be encountered because the low sulfur content and high calorific value of the low-volatile or other clean coal allow it to economically upgrade extremely poor quality coal. While this is done to meet specification purposes, actual boiler performance may be dominated by the poorer quality coal. Thus, the reputation of the low-volatile or other clean coal suffers. As a result of laboratory and full scale testing, conducted over the last five years, a model has been developed to evaluate the relative combustion characteristics of various coals and coal blends. A database for different coals has been gathered. This paper presents the model and shows how power plants and coal mine personnel can use it to evaluate their coals from different sources. It can be used to blend two or more coals from different sources so that thee blended coal has flame stability characteristics which are similar to those of the baseline coal.

Jan 1, 1991

By R. K. Mehta

Conventional triboelectrification based dry coal beneficiation methods require ground coal as a prerequisite feed material, energy intensive static-in-line mixer or cyclonic tribocharger configuration, and transport and/or improvement in the design of free-fall separators to improve the separation efficiency of [me pyrite/mineral matter from coal. The proposed paper illustrates the two concepts. First, the use of ceramic media in a polyurethane lined attitor in achieving simultaneous grinding and differential charging. Second, the use of an electrocentrifuge to selectively separate coal from mineral matter present in the triboelectrified mixture. It is of interest to note that some ceramic media can satisfy the requirements of both desired density and work function to achieve grinding and differential charging.

Jan 1, 1996

By C. R. Tatman

Failure to achieve the planned production rate at new mines and mine expansions has a major adverse impact on a project's economics. A study of 60 steeply dipping tabular deposit-type underground mines showed that 35% of the mines did not achieve their production goals. An empirical formula based on the geometry of the deposit and expressed as a rate factor is applicable to select a production rate for this type of deposit. The formula is: Annual production rate = Rate factor x Rate multiplier. The appropriate rate multiplier for each category of deposit thickness and the associated risk can be used to select an appropriate production rate.

Jan 1, 2002

By Gordon M. Pugh, David G. Rasmussen

INTRODUCTION Variations of cut-and-fill stoping are the most com¬monly used methods for mining narrow, nearly vertical veins in the United States. These methods offer the best results for maximum recovery with minimum dilution of ore from veins that are irregular along either the strike or dip. The vein is developed along the strike length in 61 to 122-m (200 to 400-ft) blocks or stopes and vertical lifts of 48 to 61 m (160 to 200 ft). The level development is either on the vein or parallel to the vein with crosscuts intersecting the vein at right angles. Chutes, manways, and haulageways are established in the center of the stopes at the lower level of the ore block. Mining then proceeds by blasting down horizon¬tal cuts of the vein in both directions from the chutes. As the blasting continues to the outer limits of the stope, the broken ore is slushed into chutes. When a complete horizontal cut has been made, the service raise, including chutes, is raised to a height of a few feet from the back and the stope is filled with either sand fill or waste rock. Then the mining cycle is re¬peated until the stope reaches the level above. LEVEL DEVELOPMENT PRACTICES FOROVERHAND CUT-AND-FILL STOPING The two basic methods used are: the development of the haulage drift within the vein, or development of the haulage drift paralleling the vein in the foot or hang¬ing wall with crosscuts intersecting the vein perpendicu¬larly at 61 to 122-m (200 to 400-ft) intervals. The il¬lustrated methods of development show some of the variations which can be used to develop a stope block. Development for cut-and-fill stoping does not require the more elaborate schemes outlined for shrinkage or sublevel long-hole stoping. Many factors must be considered before deciding on a particular development plan and usually the nature of the vein or host rock will dictate which specific method to use. If the vein is relatively straight, then develop¬ment on the vein is feasible. Excessive ground pressures will necessitate the leaving of a sill pillar (Fig. la) and highly fractured or "heavy" ground will require timber¬ing (Fig. 1b). Development on the vein has the advan¬tage of reducing capital outlay and waste handling prob¬lems since the mined rock has value. But removal of the sill pillar is costly and time-consuming. Also, where no sill pillar is left, excessive timbering and subsequent level repair is a drawback. Development in either the footwall or hanging wall is the more common procedure and offers greater flexi¬bility in overall development of consecutive stoping blocks by partially disassociating the level development from stoping (Fig. 2). Chutes, manways, and service compartments com¬prise the next stage of development and are established in a variety of ways. They provide access to the stope, ventilation ducts, and muck removal. Several different development systems are in common use and average costs for each have been developed. Raise borers are used to establish ventilation and ac¬cess from level to level. They are normally reamed with 1.5 or 1.8-m (5 or 6-ft) cutterhead and may either be left bald or lined with a 1.2-m (4-ft) diam corrugated liner plate, depending upon ground conditions. The use of an Alimak raise climber is another effec¬tive method of driving a raise from level to level. The size usually is 2 m (7 ft) square. This will accommodate square-set timber which is later installed. This method of raising is not common, although it is a valuable tech¬nique especially when level spacing is several hundred feet.

Jan 1, 1982

By R. Riding

Degussa Corporation's peroxide-assisted leaching (PAL) process was evaluated in the batch concentrate leach circuit at Hecla Mining Company's Republic Unit. The product leached in this batch circuit is a high grade gold-silver sulfide (predominately pyrite) flotation concentrate. The primary objectives of the test program were to determine the effects of dilute hydrogen peroxide addition on leaching kinetics, sodium cyanide consumption and precious metals recovery. The results of the testing demonstrated that using dilute hydrogen peroxide produced the following benefits: - 1. Batch leach time requirements decreased by 80%. - 2. Sodium cyanide consumption in concentrate leach reduced by 55%, which translated to an overall plant reduction of 20%. - 3. In the concentrate leach process, gold recovery was increased by 1 to 2%. Because of the excellent metallurgical results achieved with the use of dilute hydrogen peroxide, as well as an economic incentive, PAL has become standard practice in the concentrate leach circuit operation. A complete description of the Republic PAL plant evaluation and performance is provided in this paper. In addition, process chemistry considerations in regard to the role of hydrogen peroxide are discussed.

Jan 1, 1992

By M. Ishaq, J. Rosami, J. Brune, E. Sidrow, C. Tsai, S. Slouka

Respirable rock dust poses serious long-term health effects to workers in mining and tunneling underground hard rock environments. When inhaled, respirable silica particles commonly found in quartz and other minerals will scar sensitive lung tissue and cause irreversible lung diseases. Characteristics such as concentration, type of mineral, particle size, and particle shape inhaled can harm workers to various extents. Therefore, this study characterizes rock dust particles less than 100µm in aerodynamic diameter that are released from cutting hard rock in the underground mining environment. In this study, laboratory full scale cutting tests on samples of potash rock were performed with radial picks to generate dust. Three stages of pick wear were tested: new, moderately worn, and severely worn. Comparisons between different stages of pick wear to dust concentration, size distribution, and particle shape characteristics are drawn from this study to start determining the scenarios when the released airborne dusts become potentially most hazardous for workers. Although further testing needs to be conducted to make viable conclusions, the moderately worn pick, or the pick with the most blunt tip, in these experiments are potentially the most dangerous. The blunt pick tip released the highest concentration of dust and generated particle shapes with the highest aspect ratio compared to the other two picks. The preliminary results of this study allow for the further development of optimum bit management and maintenance systems to control the exposure of respirable dust to mine workers.

Mar 2, 2022

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"Duluth & Iron Range Railroad. The Duluth & Iron Range Railroad was built from Two Harbors to the Vermilion range at Tower, a distance of 67.6 miles, in 1884, and extended to Ely, twenty-one miles east of Tower, in 1888. It was built into Duluth in 1886, and branches were extended from its main line to the Mesabi mines in 1892 and 1893. The original grades on this road are very steep, going north, and in the thirteen miles from Two Harbors to Highland there is a rise of 1,150 feet. A new line between these points has been built with an increase of three miles in distance and with maximum grades of 1 per cent. Duluth, Missabe & Northern Railway. The Duluth, Mis¬sabe & Northern Railway was constructed from Stony Brook to Mountain Iron, a distance of 48.62 miles, in 1892. The Biwabik branch from Iron Junction to Biwabik, a distance of 15.54 miles, was constructed in 1892. The Superior branch from Wolf to Hibbing, a distance of 16.06 miles, was co11structed in 1893. The Alborn branch from Coleraine Junction to Coleraine, a distance of 53 miles, was constructed in 1906. The total main line mileage is 242 miles, of which 82 miles from Duluth to Hibbing is double tracked"

Jan 1, 1920

By N. Arbiter

During the first four decades of flotation practice, close to 200 machine designs were patented, although only about a score were ever used commercially. By the end of that period, the rigors of use had resulted in obsolescence of most pneumatic cells, with a few mechanical cells dominating the field. After World War II, newer designs began to appear but most were modifications in varying degrees of older designs with special features added. Of the dozen or so most recent developments, almost all are pneumatic, relying on compressed air instead of impellers for motive power, although in several cases pumps supplement compressors. Table 1 lists a few of the more fully documented new cells, with their significant characteristics, along with similar characteristics of a widely used mechanical cell. New designs in general are emphasizing: bubble size control; in several cases, methods for delivering feed directly to the froth; methods for introducing and dispersing air through nozzles, eductors, packed beds, or permeable walls; and variable cell volumes, relative to capacities, ranging from very small, with less than a second of retention time, to the largest, with retention times of over 20 min. An important question is the extent to which any of the newer designs are based on locating weaknesses in current mechanical cell designs and then using these as a starting point for innovations. In the present study, the key subprocesses which must take place in a cell are outlined; mechanical cells are analyzed to establish where weaknesses may exist; and then alternative subprocesses are considered which could effect improvements. COMPONENTS FOR CELL DESIGN It is assumed that mineral surface chemistry has been modified as necessary to provide optimum potential floatability. While the cell process may affect this to a degree, cell design is primarily concerned with actualizing the existing potential floatability. The cell design problem is to provide more effectively for the following: 1) Dispersion of air to obtain an optimum bubble size distribution at an optimum ratio of air volume to feed volume. 2) A hydraulic environment which permits most effective contact of potentially floatable particles with bubbles: [Table I - Cell Comparisons* Cell Type Mechanical Column Deister Miller ASH No. of units Multiple Single Single Single Retention time min.10/20 17/27 3.8 ca. is Capacities mt/m3s 0.022/0.066 0.066/0.20 0.11 10.4 st/ft3d 1/3 0.3//0.9 m5.0 469 Air hold-up % 15/20 20 n.a. 50/80 Air escape velocity m/s 0.015/0.0200.020/0.025 n.a. n.a. ft/m 3/4 4/5 n.a. n.a. * References: Mechanical (Harris, 1976,1985), (Bassarear, 1985); Column (Travis, et al. 1987); Deister (Zipperian and Christophersen, 1985); ASH (Air-Sparged Hydrocyclone) (Miller 1989).]

Jan 1, 1989

By Hou Xilun

Three production methods of rapid cold bonding and low temperature bonding pellets using sponge iron powder as a binder have been successfully developed. These methods differ from ordinary bonding method by no addition of salt and other catalyzers, no corrosion of equipment and no pollution of environment. Mechanism of pellet bonding is studied. Experiment shows that these pellets have good metallurgical properties. A semi-industrial test has proven the laboratory results, with the production of metallic pellets continuous and stable. These methods are substituted for traditional high temperature firing of oxidized pellets in direct reduction. As a result, the plant for oxidized pellets can be saved and substituted for grate in the grate-kiln system. Thus, 20% of the investment could be saved. Production cost may also be decreased. The production of cold bonding pellets does not need additional area.

Jan 1, 1980

By K. N. Han, M. C. Fuerstenau, T. B. Onlin

An investigation of the removal of finely divided silica, coal, and alumina particles less than 20,µm in size has been carried out using liquid fluidized and packed beds. The bed particles used included 48x100, 100x150, and 150>200-mesh silica, corundum, and ilmenite particles. Important variables examined included surface charge, flow rate, pH and amount of bed particles. Surface charge has been identified as the most important variable in this system. Van der Waals force also assumes a very important role in the recovery of fine particles in fluidized and packed beds. In addition to interaction between large and fine particles, interaction between fine particles themselves assumes an important role in the overall recovery.

Jan 1, 1987

By Joe D. Allison, Tom D. Baugh

The analysis for total cyanides (CN, or the cyanide due to the combination of free, weakly associated and refractory cyanide complexes) is required by most regulatory agencies for determination of effluent compliance. This method requires a distillation of the sample at low pH's and is most often sent to contract laboratories at a high time and monetary cost. This paper describes a new micro­distillation apparatus which allows for a multiple of CN,"' analyses to be carried out simultaneously saving both time and money. It can be used in the field, since only electrical power is required for the method. While not being appropriate for reporting values to the respective regulatory agencies as of yet, it is quite valuable for screening a large number of samples prior to submission of the samples to a contract lab for "official" reporting.

Jan 1, 1990

By John G. Hall

Everyone forms his own mental picture when the subject of copper is mentioned. To an architect, copper is a warm, enduring metal with a quiet beauty; to the historian, man's first metal; to the product engineer, the best electrical and thermal conductor of all commercial metals; to the investor, a volatile stock; to the speculator, the daily price quotation; to those in the mining industry, the challenge of producing copper for rising needs in the face of rising costs and lower grades of ore. At this meeting, we will look upon copper as a key raw material in industry, in national defense, in technology, in world trade, and as a principal commodity in the economies of several developing countries. As miners, and most of us here are miners, we are prone to view our role as suppliers of copper. We locate, mine, smelt and refine the metal. In the complexities of today's world, however, following a period of the longest domestic copper strike in history which caused critical world-wide shortages and widely fluctuating prices; it becomes necessary for all of us to concern ourselves with the whole spectrum of copper affairs -"from mine to consumer " But first we need to look at the miner's side of the picture -- capacity and production. We will examine these functions in terms of the whole world -- not simply the free world. Nature did not endow all regions of the earth equally, and copper in world trade has a way of ignoring political boundaries. Science and technology, as well, know no national boundaries. It is said that the "Engineering & Mining Journal" has as many readers in the Communist World as in the Free World. Nor is this a one-way street. We presently have available to us in the. U.S., cover-to-cover translations of many Communist World mining and metallurgical journals.

Jan 1, 1968

By W. –E. Marx, M. Faber, R. Pollak, I. Astberg

INTRODUCTION Essentially three strategies are pursued in parallel for protecting the underground working force in mining against the consequences of methane ignitions which might lead to explosions: • Sufficient ventilation for avoiding the formation of explosive methane-air mixtures. • Avoiding sources of ignition caused possibly by electrical equipment or friction. • Structural explosion protection for limiting explosion propagation to the farthest-going extent for the case that methane is fired because of failing of the above preventive measures taken. The corresponding methods taken in mechanized roadheadings with point-attack roadheaders in German coalmining are subject of this paper. VENTILATION In ventilation of roadheading sites the following is to be considered in respect of methane control: • Sufficient air flows by volume being cycled to the heading face for diluting released methane to safe concentrations. • Sufficient local air velocities for effective mixing of methane and air in the whole heading site, in particular directly on the heading face and underneath the roof. Furthermore, ventilation needs to be laid out in a way that cut- ting does not result in health affecting dust exposure at any working place. Accordingly, the ventilation systems shown on Fig. 1 including primary and, if necessary, secondary auxiliary ventilation air ducts as well as dedusters, are used in roadheadings. This equipment is run according to the following principles: • If the roadheader is at standstill, the heading face is ventilated by the free air jet from the blowing duct closest to the face. In this operation phase the deduster is shut-down. • During cutting, the exhaust of the blowing air duct is automatically closed, and the deduster is taken into operation. The in- coming fresh air is now locally discharged via a lateral orifice, or distributed by Coanda-type ducts from the primary or secondary ventilation air duct. In this way, a stable dust wall not disturbed by the jet of the air duct is formed in front of the heading face. Only the ventilation air stream taken in by suction of the close-to-face deduster is passed through the inby zone of the heading face (over approx. 20 m). The clean exhaust of the deduster is dischayed to the roadway in some distance outby. Immediately at the heading face, methane accumulations possibly released by cutting are diluted by compressed-air jets from air-movers located near the roof which assure more rapid motion of the air without distuhing the dust wall. • In the zone of overlapping of primary and secondary duct and the deduster - that zone possibly is poorly ventilated during cutting - sufficient local air speed is assured by Coanda-type ducts or additional ventilation jets for avoiding methane accumulation. The regulations of the inspectorate specifies geometrical conditions to be met with these configurations of ventilation equipment. In-seam roadways are ventilated at rates > 0,5 m/s. For dedusters, present-day ventilation air flows are of 600-800 m+/ min. Ventilation monitoring and control is assured by units for measuring methane and ventilation air flows. If pre-set thresholds are exceeded or fallen short of, these measuring units shut-down - dependent on potential hazard - any not intrinsically safe electrical equipment in the roadheading, either totally or in limited zones. In addition, CO-measuring units near the roadway en- trance serve for early detection of mine fires. In spite of this ventilation layout and the equipment used and in spite of the water spray systems on the cutting head (discussed later in this paper) several cases of methane ignition and subsequent burning off (however, no explosions) have been recorded in the recent past. Therefore, the above-described ventilation is nowadays complemented in many cases by machine-mounted ventilation equipment for the immediate surroundings of the cutting head. Ventilation of the surroundings of the cutting head Investigations carried out subsequent to the above-mentioned gas ignitions have shown that the high ventilation air speed necessary for rapid dilution of methane could not permanently be arrived at in the following zones: • The direct zone of cutting, in particular during sumping. • The floor zone above the debris, predominantly below the cut- ting head. Accordingly, VOEST ALPINE-Bergtechnik, a producer of mining machinery, in cooperation with DMT developed for point- alttack roadheaders a novel machine-mounted ventilation equipment, the Jet-Block" (AERO SAFE Jet-Block) shown on Fig. 2. This system allows to ventilate the above-mentioned critical zones with high flow speeds. One AS Jet-Block is mounted on each side of the boom approx. 0.5 m behind the cutting head. The blocks discharge compressed-air jets with high energy from 10 nozzles per block into the hazardous zones (Fig. 3). Two nozzles of each jet block are tangentially oriented toward the upper circumference of the cutting head, the others are arranged fan-like with orientation to the heading face underneath the cutting head and the debris. The nozzle array of the blocks as well as the com-

Jan 1, 1997

By AMAN SONI, JONATHAN G. BAGGETT, Nino Ripepi, JUAN J. MONSALVE, Richard Bishop

Underground stone mines are vulnerable to karst void formations due to the erosion of carbonate rocks by groundwater flow. The voids or cavities may lead to hazards including ground collapse and sudden outflow of clay-rock sediments during the development of the mine. This study evaluates the effect of karst voids on the strength of pillars in an underground room-and-pillar limestone mine. Ground-penetrating radar (GPR) surveys were interpreted to map the void boundaries inside a karst-affected pillar. A combination of LiDAR scanning and virtual discontinuity mapping is used to formulate the discrete fracture network (DFN). Discrete element modeling (DEM) helps simulate the effect of karsts and discontinuities in the pillar models with varying stress. It is observed that the cavities may lead to a significant reduction in pillar strength. Apart from posing a hazard to miners and machinery, any advance into these cavities may disrupt mine operations. This research serves as an initial step toward understanding the importance of pillar design in underground stone mines affected by karst voids to prevent local instability or pillar failures.

Sep 1, 2022