Search Documents

The more than 40,000 mining industry professionals that are expected to attend the National Mining Association’s(NMA) MINExpo International2000 trade show and conference will be treated to the exhibition’s largest display ever. The exhibit is expected to cover more than 60,385 m2(650,000 sq ft) and feature more than 1,300 exhibitors. The event is set for Oct. 9-12, 2000 at the Las Vegas Convention Center in Las Vegas, NV. Richard L. Lawson, NMA’s president and chief executive officer, said, “MINExpo 2000 will showcase everything that mining is proudest of. This is the largest premier mining exposition in the world.” MINExpo is held every four years.

Jan 1, 2000

By William Hodder, Ehsan Alavi, Nader Ghasempour, Daniel Cressman

The Don River & Central Waterfront Coxwell Sanitary Bypass Tunnel (CBT) Project in Toronto will extend approximately 10.5 km from Ashbridges Bay Treatment Plant west under Lake Shore Boulevard, north under Bayview Avenue and east through the Don River park area to the Coxwell Ravine Park. The tunnel is currently being mined by using a shielded dual-mode tunnel boring machine (open and close) capable of operating in EPB mode and lined by using a precast concrete segmental tunnel linear with an internal diameter of 6,300 mm and external diameter of 6,900 mm. The CBT is expected to be excavated mainly through shale bedrock of the Georgian Bay Formation, at approximately 50 meters deep. The tunnel crosses a buried bedrock valley in two locations, in the southern portion of the alignment, adjacent to the Don River, and at the northern portion of the alignment approaching the CX-1 shaft. In these two locations, the bedrock cover is expected to be less than 6 meters. The risk of encountering weathered bedrock, significant ground water inflows or surficial soil deposits through these buried valleys was identified during the design phase. The contract required the TBM to be designed with the ability to probe drill ahead of the TBM and convert to EPB mode if necessary, to cross this area. This paper will discuss the additional exploration that was performed by the contractor to identify the extent of this buried valley, the plan going into the zone of potential weathered shale, and the actual conditions encountered.

Jun 13, 2021

By Werner A. Ruemmele

Eisenhower Memorial Tunnel, called Straight Creek Tunnel during construction is located 60 miles west of Denver, Colorado at 11, 160 ft. elevation. It is 8, 510 feet long, and carries two lanes of 1-70 traffic under the Continental Divide. This paper describes improvements and changes made in construction methods for utilities, concrete lining, ceiling, wall covering and paving to allow maximum offsite fabrication and activity overlap resulting in a one-year faster completion for traffic. The substantial changes proposed on a design-and-construct basis by the contractor and put into effect after State approval were: 1. Substitution of ductile iron and thick-wall P.V. C. pipes for clay pipes allowing placement and operation before hole-thru. 2. Outside pre-assembly of large rebar mats, using a novel tension-splice with cable clamps. 3. Arch concrete placement method modified to make 4, 322 ft. of lining in 10 weeks possible. 4. Safety barriers precast and epoxy coated offsite instead of cast-in-place and tile faced. 5. Prestressed hollow ceiling slabs with porcelainenamel coated steel sheets assembled offsite, instead of in-place glazed tile and in-place cast concrete ceiling. 6. Glazed tile wall panels 8 ft. long by 11 ft. high assembled off site and erected using vacuum pad mounted on special lift. 7. Asphalt paving while other work proceeded, instead of reinforced concrete slab and asphalt overlay. Work started in January 1968, but advance came to a one-year standstill for major structural redesign and negotiations of a new agreement during 1970. Using multiple drift construction followed by top-heading and bench excavation, it then progressed to hole-thru in July 1972. As a result of art 18-month overlap of activities the tunnel was opened for traffic only eight months later in March 1973. Gibbons and Reed Company of Salt Lake City, Utah sponsored the joint Venture of Al Johnson-Gibbons and Reed-Western Paving-Kemper during 1971, 1972, and 1973. The tunnel was the subject of a previous paper delivered at the RETC '72 in Chicago by R. C. Hopper, T. A. Lang, and A. A. Mathews, describing geology, unusually severe structural loading and multiple-drift tunnel excavation.

Jan 1, 1974

By Mike Wardell-Johnson, Chris Campbell-Hicks, Craig Bitmead

Faster, simpler, cheaper and more accurate cyanide ex­tractable gold procedures are now available for grade control assay. Cyanide 'bulk leach extractable gold' or BLEG assays have previously been seen as desirable, due to the large sample size that can be treated, but not in common use due to the 24hr total assay time required. Sample sizes from 50g to several kilos can now be accurately assayed in less than 4 hours total time with the larger sample size increasing accuracy, without loss of precision, while greatly reducing the 'nugget effect' or coarse gold bias. Typical assay size is 200g, equivalent to 4 x 50g Fire Assays or 10 x 20g Aqua Regia Assays. Ongoing modifications and refinement of the procedures and reagents used also indicate applicability to the treatment of coarse gravity gold where substantial savings in both capital and operating costs for these circuits are possible. The successful use of this cyanide assay at the Bannockburn and Windine Well operations are cited to-gether with a compre­hensive comparative testwork program by Newcrest. Testwork at Gidgee and Lynas Gold operations is currently being initiated. Other operations using the method include Red Dome and Kidston; with Placer(Granny Smith) and PMA's Palm Springs operations to commence shortly.

Jan 1, 1995

By K. Dagdelen

The definition and shortcomings of traditional cutoff grades are discussed. The concept of optimum cutoff grade policy which maximizes the Net Present Value (NPV) of annual cash flows coming from a mining project is introduced within the basic framework outlined by K. F. Lane. Several examples are used to demonstrate the shortfalls of cutoff grade policies obtained by various heuristic optimization techniques. An algorithm to obtain an optimum cutoff grade policy which maximizes the NPV of a project is given and described in detail.

Jan 1, 1993

By Nenad Spoljaric

Greensand, greensand marl, and green earth are names given to sediments rich in the bluish green to greenish black mineral known as glauconite. The word glauconite is derived from the Greek word glaukos, meaning bluish green. The term "greensand" as a rock name for a glauconite-bearing sediment is more appropriate than "greensand marl," a term that has been doggedly perpetuated in the literature. Because of its potash and phosphate content, greensand was mined and marketed as a natural fertilizer and soil conditioner for more than 100 years. The advent of manufactured fertilizers with adjustable nutrient ratios led to a decline in the use of greensand in agriculture. The material has since been recognized as useful in water treatment. Unfortunately, despite large reserves and world- wide distribution, glauconite has not been utilized to any significant commercial extent because no major application has been found for a substance with its chemical composition and properties. This is probably due mostly to a paucity of research on its potential commercial uses. Extraction of potash received considerable attention during and just after World War I. Because of relatively high extraction costs and a generally low potash content (viz., less than 8%), glauconite lost its appeal as a source of this commodity. Historical Background Greensand was used as a fertilizer in New Jersey in the latter part of the 1700s. During the early 1800s its use became more common; applications of as much as 22.5 kg/m2 were sometimes made, although recommendations for agricultural use suggested 4.5 to 11 kg/m2 (Tedrow, 1957). Many crops, especially the forage type, were said to improve with greensand application; however, because of its slow release of potash, large quantities were required. Certain greensands that contain sulfur and sulfide minerals are harmful to plant growth, and these were classified as poison, burning, or black marls. The availability of higher grade potash salts from other mineral sources and the manufacture of prepared fertilizers displaced the agricultural use of greensand during the latter 1800s. During the mid-1800s the greensand industry, centered in a small section of the eastern United States, grossed more than $500,000/y. Toward the end of the century, however, annual production had dwindled to less than $100,000 in value. By 19 10 there were only six or eight greensand producers grossing less than $5,000/y each (Tyler, 1934). There was a brief revival of the US industry during World War I because of the curtailment of foreign potash, especially from Germany. During the latter 1940s and early 1950s greensand was again recommended as a food nutrient for plants and farm crops. Agronomic studies discussed its potential as a soil additive that gradually releases potash and many trace element nutrients essential for plant growth (Tedrow, 1957). Greensand was sold with the idea that it would condition soil and absorb and hold water while its base exchange properties would release trace elements. For a short time glauconite was used in certain parts of New Jersey as a binding additive in the brick industry, and in the 1800s it was used for making green glass (Cook, 1868). In the early 1900s the base exchange properties of glauconite were recognized for water treatment and the mineral gained acceptance as a water softener. Mansfield (1922) does not mention base exchange even though this phenomenon was known in 1916 or earlier. From 1916 through 1922 several patents for the use of glauconite as a water softening agent were granted. A method was also patented for treating greensand to improve it for water softening and ready regeneration with common sodium chloride brine (Borrowman, 1920, Spencer, 1924, Kriegsheim and Vaughan, 1930). Treated glauconite, on contact with water containing magnesia or lime, takes up magnesium or calcium ions and releases sodium ions. This exchange is limited to the outer surface of glauconite grains, and when all the surfaces have absorbed their capacity, the grains must be regenerated. Regeneration, simply stated, consists of treating or backwashing the glauconite with a sodium chloride solution, which replaces the hard water elements with sodium, thus reviving the glauconite. The process has become more sophisticated due to competition among companies in the water softening business. Greensand products for water softening generally consisted of several different grades distinguished by the particular treatment the glauconite was given during processing. The standard greensand water softener was produced from natural glauconite that was only washed and classified. Its characteristics for water softening are given in [Table 1].

Jan 1, 1994

By Ryota Kasahara

In 1981, a gas outburst accident occurred in the Yubari Shintanko coal mine, the only expectant mine in Japan, it caused 93 deaths. As a result, Yubari Shintanko closed in 1982. This major disaster was a turning point for sustainability of Yubari City, the largest coalfield in Japan. Finally, Yubari City was bankrupted in 2007. This paper aims to explore how miner’s children experienced this disaster and felt about region, family, and themselves, and to explain the relation between region declining and children’s lives. The data of this paper are the archived 600 essays, written by the junior high school students at the time of the disaster. There are three findings. First, the children who lost their father were the most shocked. They faced profound sadness. But they expressed that they had decided to overcome their sadness with surviving family. Second, the children who didn’t lose their father were also influenced. They were anxious about the future of Yubari, their family, and themselves. Furthermore, they decided to strive for their future. Third, they understood the disaster as a turning point of Yubari declining and looked ahead their future outside of Yubari. In conclusion, this disaster created their hopelessness to Yubari region and, as a result, promoted the decline of the city through their migration to other city. Furthermore, it is important to clarify that Yubari City has to continue the struggle to the regeneration.

Jan 1, 2017

By D. R. East

The concept of sub-aerial tailings deposit.ion using a managed rotational deposition system to form a deposit of partly-saturated tails for North American conditions was introduced by Knight and described by Knight and Haile (1983). The application of the sub-aerial technique, together with continuous removal of all surface waters and underdrainage outflows from the Key Lake uranium mine I s tailing storage facility in Northern Saskatchewan, Canada, has been documented by Knight and Haile (1984). Since then, the concept is being applied in the United States to tailings facilities in California, Nevada, Arizona, Utah, Colorado, Idaho and South Dakota.

Jan 1, 1989

By NEHA PANDEY, Sunil Kumar Tripathy, ARIJIT BISWAS

Due to the growing market of Electric Vehicles (EVs), there is a rise in battery demand. Nickel can be used as a potential element in cathode for lithium-ion batteries. Nickel can provide thermal stability, high energy density, and conductivity in cathodes of lithium-ion batteries. Low-grade chromite overburden from Sukinda mines contains less than 1 wt% of nickel, which can be utilized to extract nickel. Recovery of nickel from such low-grade overburden can help in value addition. The present study provides deeper insight into the aspects of extraction of nickel product derivatives (NPDs), mainly mixed hydroxide product (MHP), through the hydrometallurgical route. The current study focuses on extracting nickel and cobalt from a mine overburden with 0.41% nickel with major silicate gangue. MHP can be processed further for nickel sulfate production, a potential raw material for cathodes in EV batteries. The study discusses a process flowsheet to recover nickel and cobalt from overburden through atmospheric leaching with pre-calcination. It is observed that the step of pre-calcination improves the effective recovery of nickel from overburden. The leaching reactions are effective at a temperature of 90 °C and 1 atmosphere pressure. The orthophosphoric acid was used as a lixiviant for the selective recovery of nickel and cobalt from overburden. Recovery of nickel and cobalt obtained at optimum conditions is 84.0% and 39.9%, respectively. The iron impurity in the leachate solution is 1.27%. It is concluded that the process with pre-calcination along with acid leaching is effective for extracting nickel and cobalt at atmospheric pressure.

Dec 28, 2023

By A. W. Jenike

Mine backfilling is a desirable method for the disposal of retorted oil shale. Hydraulic, mechanical and pneuna.cic transport and stowing methods were investigated, and the mechanical transport and stowing method using conveyors was selected as the most promising system. Transport of retorted oil shale at the rate of 3000 cons per hour (2700 t(h) to the backfill level, situated about: 2000 feet (610 m) below surface, with skips or conveyors is uneconomic. Hence, borehole transport utilizing gravity flow was investigated. This paper describes the theory of flow, flow properties of retorted oil shale, and the design of a borehole and hopper system.

Jan 1, 1978

By J. Rothschild

I would like to thank the Society of Mining Engineers for inviting me as well as the other distinguished panelists to spend a morning reviewing and discussing the handling and shipping of industrial minerals. I also would like to thank my management, Cometals. Inc. for permitting me to take time out from the daily hectic pace of marketing and trading to share with you some of our experiences and expertise. Cometals, Inc. is a wholly-owned subsidiary of Commercial Metals of Dallas. The transportation and handling costs of industrial minerals frequently are a major component of the value of the goods marketed and, therefore, it is only natural that close attention should be paid to them. Many of the industrial minerals require special handling to assure that the material reaches the consumer without being contaminated or getting wet. I invite you to accompany me through the various steps involved in "delivering the goods" to the consumer.

Jan 1, 1989

By A. M. Raichur

The selective adhesion of hydrophobic Mycobacterium phlei to coal particles is responsible for flocculation of fine coal from associated ash forming minerals. The driving force for the differential adhesion is the hydrophobic interactions between the fatty acid surface of the organism and hydrophobic nature of coal. The effect of Mycobacterium phlei on surface hydrophobicity, surface charge and mechanism of adhesion on coal and associated minerals are controlled by several factors including hydrophobicity and surface and solution chemistry of the system. Adhesion measurements indicate that maximum adhesion occurs below the isoelectric point (IEP) of the coal particles. While massive adhesion of Mycobacterium phlei is observed on coal, however, negligible amount of Mycobacterium phlei attaches to mineral pyrite and quartz.

Jan 1, 1995

By Charles H. Wells

This paper describes a commercial installation of a sophisticated instrumentation and control system designed to maximize the performance of heavy medium cyclones. Samples of plant feed and its products were collected and analyzed for ash content so that measures of efficiency could be determined for plant operation under (1) manual control and (2) automatic (computer) control. The heavy medium cyclone control strategy and its digital computer implementation are discussed in detail. The sample results are analyzed and the economic benefits of automatic control are discussed. Results from the initial data sets quantify the economic benefits of automatic closed-loop control; viz, increased recovery and reduced clean coal variability have been clearly demonstrated.

Jan 1, 1981

By P. Bissert, M. Klein, L. Yan, D. Yantek

"Mine Safety and Health Administration (MSHA) regulations require underground coal mines to use refuge alternatives (RAs) to provide a breathable air environment for 96 hrs. One of the main concerns with the use of mobile RAs is the heat and humidity buildup inside an RA. The accumulation of heat and humidity can result in miners suffering heat stress or even death. MSHA regulations require that the apparent temperature in a fully occupied RA must not exceed 95°F. To investigate this issue, the National Institute for Occupational Safety and Health (NIOSH) conducted testing on a 23-person tent-type RA in its Experimental Mine (EM) in a test area that was isolated from the mine ventilation system. The test results showed that the average measured air temperature within the RA increased by 9.4°C (17°F) and the relative humidity (RH) approached 94 %RH. The test results were used to benchmark a thermal simulation model of the tested RA. The validated thermal simulation model predicted the average air temperature inside the RA at the end of 96 hours to within 0.6°C (1.0°F) of the average measured air temperature. INTRODUCTION If an accident occurs in an underground coal mine, miners who fail to escape from the mine can enter an RA for protection from adverse conditions, such as high carbon monoxide levels. One of the main concerns with the use of mobile RAs is the potentially adverse thermal environment inside an RA from the metabolic heat of the occupants and the heat released by the carbon dioxide (CO2) scrubbing system. Moreover, the humidity within the RA will increase through occupants’ respiration and perspiration and from the chemical reaction within the CO2 scrubbing system. The accumulation of heat and humidity can result in miners suffering heat stress, heat stroke, or even death. In its 2007 report to Congress, the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) recommended that RAs should be designed to ensure that the internal apparent temperature (a temperature-humidity metric) in an occupied RA does not exceed 35°C (95°F). However, a standard method to determine compliance with this metric does not exist. The heat transfer process within and surrounding an RA is very complex, and is not easily defined analytically or experimentally. To investigate the related issues, OMSHR conducted heat and humidity testing on a 23-person tent-type RA in its Experimental Mine (EM) in a test area that was isolated from the mine ventilation system. During the testing, numerous parameters were measured: heat input to the chamber, the air temperature and relative humidity inside the RA, the air temperature in the mine, the mine strata temperatures versus depth, and the airflow inside and outside the chamber. The focus of this paper is on the temperature rise within an RA. TAITherm heat transfer analysis software was used to develop a thermal simulation model of the RA as it was tested in the mine, using the test results as the benchmark. Both sensible and latent heat were used in the test and the model."

Jan 1, 2016

By Noel A. Genco, Edward F. McCarthy, Robert J. Piniazkiewicz

Talc, when it can be isolated as a pure mineral, has a composition of 63.36% SiO2, 31.89% MgO, and 4.75% H,O. However, as a commercial commodity less than half of all talc sold has a purity exceeding 95%. Nevertheless, impure talc products find a multitude of uses and few substitutes in many industrial applications. Minerals commonly associated with and sold together in talcose mixtures are chlorite, dolomite, mica, magnesite, and tremolite. Steatite was originally a mineralogical term applied to pure talc. Today steatite usually denotes a high-talc ceramic body used as an electrical insulator, and the talc used in such applications is known as steatitic talc. Steatitic talc generally is found in massive, high- purity form and in the past was machined directly into electrical parts, which rarely is done today. Impure varieties of massive or block talc are still commonly termed soapstone. Soft massive talc, suitable for crayon manufacture, has been referred to as French chalk. It has been common practice to discuss talc, soapstone, and pyrophyllite under the same general heading. In the case of soap- stone and talc this is natural, since many different types of platy, soft minerals exhibiting a high degree of lubricity (commonly referred to as slip) have been grouped together and called soapstone or talc. Further, there are mineralogical relationships between pyrophyllite and montmorillonite and between talc and hectorite. Thus, talc and pyrophyllite are sometimes referred to as clay minerals. When finely divided talc or pyrophyllite are combined with water in proportions to make a slurry, the end product does have the appearance of a clay-water mixture. Soapstone for utensils and ornaments was mined by prehistoric Native Americans on Santa Catalina Island, CA. In the mid- 1800s soapstone from deposits along the western foothills of the Sierra Nevada Mountains was used by white settlers as building and ornamental stone and for the linings and foundations of furnaces (Anon., 1956). Previous to 1916 the annual recorded production in California did not exceed 1.8 kt. From 1912 to 1918, however, output rose sharply when the Talc City, Western, and Silver Lake mines were put into operation. From 1916 to 1935, the state's annual output of talc was in the range of 8.2 to 18.2 kt. There was another increase in the mid-1930s, when the use of talc in wall tile grew rapidly. In California the production of talc grew to 57.2 kt in 1943. The post-war building boom helped California's production to grow to 108.9 kt in 1951. Production stood at 149.8 kt in 1968, 13 1.6 kt in 1969, 167.9 kt in 1970, and 140.7 kt in 1972. In the mid-seventies and early eighties, however, California's talc production declined to approximately 20 kt in 1992 due to reserves exhaustion and the material's tremolite content, which raised significant product liability concerns at the time. Talc mining in New York State dates from about 1878, when a Colonel Palmer and associates opened the first commercial talc mine on the Nelson Freeman farm near Talcville. In 1893 this operation was sold to International Pulp Co., which changed its name to International Talc Co. in 1944. The company was acquired by R.T. Vanderbilt Co., Inc., in 1974. A new talc operation, Gouverneur Talc Co., owned by R.T. Vanderbilt Co., began operations near Balmat, NY, in 1948. The initial capacity of the processing plant was 180 tpd (Gillingham, 1950). Subsequent expansions have increased capacity to more than 725 tpd. Talc was discovered in the area of Johnson, VT, in 1902, marking the birth of the Vermont talc industry. American Minerals Co. initiated plant operations at Johnson in 1904. MagnesiaTalc Co. opened a plant at Waterbury, VT, in 1913 (Burmeister, 1963, Trauffer, 1964) and acquired American Minerals Co. in 1923. The Waterbury mine had a long history as a producer of talc crayons. Eastern Magnesia Talc Co. was formed in 1924 by the merger of Eastern Talc Co. and Magnesia Talc Co. In 1956 Vermont Mineral Co., with a talc mine at Hammondsville, VT, was also acquired. A new plant was then built at Gassetts to produce roofing products. In order to produce high grade products for several markets, Eastern Magnesia Talc Co. began operating a modem froth flotation plant at West Windsor, VT, in 1964. The ore was provided by the Hammondsville mine. This operation, known as Windsor Minerals, Inc., continued from 1972 to 1989 as a subsidiary of Johnson and Johnson Co. In 1989 Cyprus Minerals Co. acquired Vermont Talc, Inc. and Windsor Minerals, Inc.. thus consolidating the talc mining and processing operations at Hamm, Windham, Johnson, Chester, Ludlow, West Windsor, Troy, and Reading, VT, under one ownership. As the result of Cyprus' sale of its worldwide talc assets to the RTZ Group in 1992, its US talc operations are now part of Luzenac America, Inc.

Jan 1, 1994

By T. McCallum, C. Cooper, B. Hutzler

"In copper solvent extraction, managing the quality of the organic phase is a key parameter to ensure optimal physical and metallurgical performance in the plant. Increased throughput as a result of declining ore grades coupled with advances in plant design and practice, resulting in reduced organic losses, has pushed the limits of the status quo with respect to organic quality. Clay treatment of plant and recovered organic at the optimal dosage is critical in maintaining quality, however, achieving the optimal dosage through existing filtration capacity and practice can be difficult. Cytec has developed a process aid that increases efficiency of existing filtration equipment that has been successfully implemented at two commercial SX operations. ACORGA® CB1000 enables higher dosages of clay while allowing for more efficient use of existing filtration capacity. This study analyzes results from commercial trials and demonstrates that improved organic quality and clarity is achievable through optimization of current treatment practices. INTRODUCTION Decreasing ore grades have prompted copper solvent extraction operations to raise PLS flow rates, increasing plant throughput to maintain production1. The ability to process higher flow rates through existing mixer-settlers historically came at the expense of increased entrainments2. However, advances in mixer-settler design, practices and improvements in organic recovery processes have enabled operations to maintain, and in some cases reduce organic losses while achieving higher flow rates through existing equipment. Based on the increased demand on the SX equipment and reduced losses (or more efficient recovery) maintenance of the circuit organic quality through efficient clay treatment is now more important than ever. This paper discusses common industry practices and related issues in organic clay treatment, and presents benefits achieved in commercial operations through the use of ACORGA® CB1000 Clay Binder. IMPROVEMENTS IN DESIGN AND PLANT PRACTICE Mixer-settler design has improved since the first commercial copper SX operation in the late 1960s. Advanced designs in mixer, settler, and settler internals have contributed to reductions in entrainments. For example, improved impeller designs have been reported to decrease organic in aqueous entrainment from the ‘old designs’ of 50-200 ppm3 to as low as 4 – 10 ppm confirmed via diluent and reagent consumptions . Similarly, operations are reporting a 20-50% decrease in reagent consumption when compared to the original design criteria3. Operations have optimized settler internals to increase coalescence and have improved settler operating practices which have been shown to reduce entrainments7. Comparison of the SX world operating data from 1999 and 2007 shows reductions in organic entrainment losses with increases in flow rates."

Jan 1, 2015

By Rusdian F. Kayadoe, Michael B. Hutahaean, Sandi A. Firmanulhaq

Deep Mill Level Zone (DMLZ) mine is located in Papua, Indonesia operated by PT Freeport Indonesia (PTFI) with approximately 1,500m below surface. The ore body extend 1230m width from northwest to southeast by 300–400m length east-west. The mine currently produces at full production of 80,000 tons per day until 2041. Part of the extension of current active production block and mitigation sits 225 m above the production block 1 (PB1) and 2 (PB2A and PB2B) which located in 2590L, named production block#4 (PB4W and PB4E). As the mining continues at PB1N, PB2A, and PB2B, the cave growth vertically and laterally to south perimeter of the footprint affecting the integrity of PB4W/E footprint. Currently, PB1N and PB2N are in active production whilst PB4E development continues from South against PB1N cave, as can be seen in Figure 1. A slight overlapping between PB1E and PB4E intentionally to promote cave connections between the two caves. Despite low stress model in the PB4E near existing caves, the PB4E cave propagation expected by the large strain and will be propagating in tension failure to the PB1E cave. Hence, designing the drill drives edge and first drawbell location as close as possible to the PB1E cave is necessary to guarantee cave connection. Since PB4 footprint development commenced in December 2021, there have been a substantial cave propagation observed from existing downhole monitoring. As the PB4 footprint designed perpendicular to existing DMLZ PB1 cave, adjustment of the development edge design is necessary to reflect the progression the loosening zone propagation to the South. Final life of mine design for extraction, undercut and ventilation level were decided in October 2023 considering latest update cave (fractured/ yielded) boundary. Numerical model of potential rock mass damage also aids the decision to locate the drift edge design. Predicting the cave progression impact is critical to both production at the existing active blocks and development of the new area. The use of cave shape data from year 2021–2023 gives an insight of the cave shape estimation at the end of 2024 when the undercut drift will be developed. This paper presents actual cave growth of active production blocks and its relative vertical progression impact as the result of drawing in order to plan for acceptable rate and provide mitigation once the minimum acceptable rock mass condition and minimum pillar threshold achieved.

Feb 1, 2025

Acid mine drainage (AMD) forms when sulfide minerals are exposed to oxidizing conditions in coal and metal mining, highway construction, and other large-scale excavations. Iron sulfides common in coal regions are predominately pyrite and marcasite (FeS2), but other metals may be complexed with sulfides forming chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), and sphalerite (ZnS). Pyrite commonly occurs with these other metal sulfides thereby causing AMD where Cu, Pb, and Zn are mined. Upon exposure to water and oxygen, sulfide minerals oxidize to form acidic, sulfate-rich drainage. Metal concentrations in AMD depend on the type and quantity of sulfide minerals present. The drainage quality emanating from underground mines or backfills of surface mines is dependent on the acid-producing (sulfide) and alkaline (carbonate) minerals contained in the disturbed rock. In general, sulfide-rich and carbonate-poor materials produce acidic drainage. In contrast, alkaline-rich materials, even with significant sulfide concentrations, often produce alkaline conditions in water. Approximately 20,000 km of streams and rivers in the United States are degraded by AMD. About 90% of the AMD reaching streams originates in abandoned surface and deep mines. Since no company or individual claims responsibility for reclaiming abandoned mine lands (AML), no treatment of the AMD occurs and continual contamination of surface and groundwater resources results. The oxidation of iron disulfides and the generation of acidity occur through several reactions (Stumm and Morgan, 1970). The chemical equations can be found in Caruccio and Geidel (2000). If any of the processes represented by the equations were slowed or altogether stopped, the generation of AMD would also slow or cease. The equations show that 1000 Mg of rock containing 1% sulfur, all as pyrite, would yield upon complete reaction 31.25 Mg of acidity. Therefore, 31.25 Mg of 100% CaCO3 would be required to neutralize the acidity. The alkaline content of overburden determines whether there is enough neutralization potential (NP) to counteract the acid produced from pyrite oxidation. Of the many types of alkaline compounds present in rocks, only carbonates and clays occur in sufficient quantity to effectively neutalize AMD. A balance between the acid-producing potential and neutralizing capacity of an overburden sample will indicate the ultimate acidity or alkalinity that might be expected in the material upon complete weathering. Accurate prediction and control of AMD before surface mining require an understanding of three important factors: 1) overburden geochemistry, 2) method and precision of overburden handling and placement in the backfill during reclamation, and 3) the postmining hydrology of the site.

Jan 1, 2002

By Shimi Tzobery, Jay Davenport, Raymond Henn, Sam Bandimere

Over the past several decades, the use of cement-based grouts using ultra fine cement as a replacement for portland cement has begun to gain acceptance as an alternative to chemical solution grouts used in permeation grouting. The amount of information currently available on grouts made with ultrafine cement is limited. The authors used a previously developed field testing program to perform additional tests to evaluate the permeation performance of portland and ultrafine cement-based grouts. For the first time, the 2003 testing program included an attempt to determine the 28 day compressive strength of the sand permeated by the grout.

Jan 1, 2005

By D. McElhinney, J. Winfield, G. Buchan, B. Slaker, A. Iannacchione, T. Minoski, G. Rashed, M. Van Dyke, M. Murphy

"The National Institute for Occupational Safety and Health (NIOSH) has previously established pillar design guidelines for the underground stone mining industry. These guidelines were created from an empirical database of pillar observations and were largely drawn from shallow, flat-lying mining operations. Current trends forecast a great amount of underground stone mines developing under deeper cover, higher seam dips, and more frequent multiple-seam mining configurations than in the past. The complex loading conditions and limited experience in these environments presents a substantial increased risk of ground failure. To investigate these loading conditions, NIOSH has installed a pillar and roof monitoring system at an underground limestone mine in central Pennsylvania. The mine is operating in a seam with dips ranging from 13 to 18 degrees and overburdens ranging from 275 m (900 ft) to 425 m (1,400 ft). Instrumentation installed in an undeveloped pillar and in surrounding strata is currently measuring pillar and roof behavior in response to stress redistribution during excavation. Laser scans are being used to measure ground displacement and changes in conditions associated with local mining conditions and significant geological features. Initial stress measurements show a gradual increase in stress in response to mining, and stress changes that correspond with blasts. The seismic system is operational, with calibration events signaling on each of the 18 sensors. INTRODUCTION Improving mine-wide ground control stability can help reduce the potential for catastrophic failure of underground structures. The National Institute for Occupational Safety and Health (NIOSH) has conducted prior research in stone pillar design and has established fundamental pillar design guidelines for the underground stone mining industry, which resulted in the development of the S-Pillar program (Esterhuizen et al., 2011; Esterhuizen and Murphy, 2015). The data that constitute the S-Pillar program were derived from past mining experience that was almost exclusively drawn from shallow, flat-lying, single-level mining operations1. Stakeholder interactions with NIOSH researchers have indicated that increased numbers of underground stone operations are expected to mine under significantly deeper cover, with greater seam dips, and under multi-level operating conditions (Slaker and Murphy, 2016). The complex loading conditions and limited experience in these challenging environments present a substantial increased risk of ground failure. Inadequate pillar design in these new and challenging environments could result in catastrophic wide-area pillar collapses and an increased safety burden to miners working in the U.S. limestone mining industry. To develop design guidelines and prevent inadequate pillar designs for these challenging environments, NIOSH is currently conducting detailed pillar response investigations at case-study mine sites operating in challenging environments."

Jan 1, 2018