Search Documents

By Y. Luo

Surface subsidence process due to underground coal mining often has the potential to cause problems to buried pipelines. In this paper, a technique for assessing the stress level on a subsidence-affected pipeline is introduced. The main contributors for the stresses on the pipelines are identified. Mitigation techniques for reducing the stress on the pipeline have been proposed and successfully tested.

Jan 1, 1997

By W. P. Arnott, P. Nascimento, X. L. Wang, K. C. Kocsis, S. J. Taylor, H. Firouzkouhi

We report the first spectral photoacoustic measurements of silica, coal, and kaolinite dust absorption coefficients from 11 to 13 μm at 5 nm resolution made with a tunable quantum cascade laser. This is important because airborne silica dust and coal dust within mining environments continue to be a problem for mine workers and staff due to their severe health effects on the respiratory system, while other dust types are potentially interferents to their detection. Our real-time spectra compare favorably with the non-real-time filter-based Fourier transform infrared spectrometer (FTIR) spectra obtained using the sampling system developed by NIOSH for their end-of-shift method to determine silica dust concentrations using a portable FTIR. We discuss our new dust generation system and instrument testing chamber. We also show that our PM4 silica mass concentration measurements by a low-cost air quality sensor (SPS30) are in good agreement with the TSI Aerosol Particle Sizer instrument, the NIOSH end of shift method, gravimetric mass, and correlate well with photoacoustic light absorption measurements at a wavelength where silica absorbs strongly.

Aug 20, 2022

By S. N. Chadha

INTRODUCTION The work described here refers to the Genesee River Interceptor Southeast Project. This project is a part of the Combined Sewer Overflow Abatement Program, Phase I, for the Rochester Pure Water District, Rochester, New York. Our contract required the design of a 13,200-feet long main tunnel, 14 feet finished diameter, approximately 100-120 Feet below ground; drop shafts and diversion tunnels to deliver surface flow to the main tunnel; a gate chamber whereby the main tunnel is dropped 35 feet, and provision made for connection to the future tunnel in Phase II, as well as a host of other surface structures. Cross sectional dimensions for the structures involved varied from 16 feet circular to a 20'x50' horseshoe, in a competent rock formation consisting of Lockport Dolomite and Rochester Shale. In the construction of a rock tunnel, the problems of the tunnel designers are as follows: 1. To evaluate stresses in the rock as a result of excavation. 2. Design a temporary support system to prevent any rock failure during the period of construction. Design of this temporary support system is empirical. Design loads given by empirical relations are dependent upon the rock quality and size of opening. Temporary support system may either be steel frames closely spaced along the length of tunnel and tied together, in the case of poor rock, or, an even spacing of rock bolts in the case of competent rock. 3. Design a final lining for the service loads. Service loads, in our case of a water-carrying tunnel, are hydrostatic pressure due to ground water, deadweight of lining) pressure of contained water and time dependent rock loading. The constitutive properties of the rock are extremely complex because of discontinuities, pre-existing stresses due to overburden, material symmetries and changes of initial state associated with the process of excavation. The changes of initial state may be changes of stress fields along with the consequent yield of the material or the extension of existing discontinuities.

Jan 1, 1977

By Robert W. Burns

Gentlemen, my subject today is glass reinforced plastics. By definition, this encompasses a wide variety of materials: at least a half dozen basic varieties of polyester, epoxy, and phenolic; virtually infinite compounding variations within the basic groups: literally limitless variations in the amount and the nature of the glass reinforcing. Complicating all of this is the fact that different modes of application of the same material fall appreciably alter' the product's general strength and suitability. These many, many differing materials are what we conveniently call "glass reinforced plastics" or, more simply, fiberglass". This common name is actually a large part of the problem when dealing with fiberglass materials. Far too often a specification is written calling for simply "fiberglass reinforced polyester', based on successful prior use of a polyester laminate. Such a specification is very nearly worthless since such tremendous variation is possible under it. Success of a laminate furnished under such a specification is entirely dependent on good fortune

Jan 1, 1962

By Rao Balusu, Bharath Belle, Krishna Tanguturi

A collaborative research project is undertaken by Anglo American Coal and CSIRO to develop appropriate strategies for gas and spontaneous combustion management of longer panels. Extensive computational fluid dynamics (CFD) modelling studies have been conducted and calibrated using operational longwall goaf gas data to obtain a fundamental understanding of goaf gas flow patterns in longwall panels of 1.0-km and 3.0-km lengths and a detailed investigation of the effect of various mining and operational parameters on goaf gas flow patterns. The modelling studies have also been used to investigate the performance of various gas drainage and proactive inertisation strategies during various stages of longwall panel extraction. Simulation results indicated that apart from tailgate (TG) side goaf holes, gas drainage from maingate (MG) goaf holes and the mid panel start-up goaf holes would be useful for flat seam field conditions. Operation of 8–10 goaf holes is recommended for field site conditions with high goaf gas emissions of 6000 L/s. The modelling results indicated that the traditional inert gas flow rate of 500 L/s currently used in some mines would be insufficient to achieve effective goaf inertisation in long panels. Results indicate that 3.0- km-long panels would require 1500 L/s of inert gas and there is a need for multi-point inert gas injection strategy for effective goaf inertisation. In this paper, details and results of modelling investigations and recommended strategies for gas and spontaneous combustion management in 1.0-km- and 3.0-km-long panels are presented.

By Simon D. Strauss

The recession that began in late 1980 has proved to be not only prolonged and severe, but in certain ways unique in its effect on the mineral industries among the periods of economic slowdown experienced in the Western world since the end of World War II. This time almost all minerals have been affected. In previous business turndowns, by contrast, some mineral sectors have with-stood economic adversity well. They experienced little or no adverse effect-thanks either to a strong secular expansion in the markets for their particular product or to specific factors that caused demand to be well maintained. For example, aluminum, molybdenum, and nickel are three metals that enjoyed extraordinary growth in applications during the years 1946-1973. These metals were little affected during the recessions that occurred in that era. Similarly, coal did not suffer a pronounced drop in sales in the 1974-75 turndown because, with the price of oil rising sharply, a switch away from oil and back to coal was clearly indicated for some energy-intensive applications. Oil itself was largely impervious to the ups and downs of the business cycle until very recently. And the precious metals, gold and silver, have often been regarded as benefiting from reduced economic activity because labor becomes more available, productivity rises, and operating costs diminish. In the current recession, however, no major mineral has escaped the broad trend. The secular growth factors that were previously so evident for aluminum, molybdenum, and nickel have disappeared, at least temporarily. The stable pricing behavior that previously characterized all three of these commodities has been replaced by extreme price weakness and apparent inability of the major producers to continue their roles as market leaders. Coal and oil both have suffered from a sharp drop in energy requirements. There are those who now anticipate a collapse of the market control over oil prices so clearly exercised by OPEC since 1973. If oil prices are no longer effectively controlled by the governments of the exporting countries, then coal prices are also certain to be affected. And the combination of high interest rates, tight money, and a change in public perceptions of precious metals put the skid under gold and silver quotations in 1981 and early 1982. Although inflation has been viewed as the scourge of most Western countries ever since the oil crises of 1973-74, prices-in constant dollars-of most minerals have not risen. On the contrary, with the exception of the precious metals and oil, for most minerals the prices that prevailed at the end of 1982 were close to the levels of the Great Depression of the 1930s in constant dollar terms. Table 1 compares prices for copper, lead, zinc, and aluminum at the end of 1982 with the average prices in 1934, stated in constant 1967 dollars. This emphasis on prices for mineral commodities reflects the fact that profits of mining enterprises vary directly with the level of prices. Manufacturing and retailing enterprises march to a different tune. They establish sales prices based on costs. Their profits tend to vary with volume. Commodities are for all practical purposes fungible, that is the advantages of known brands in marketing manufactured goods have little application in a commodity market. Thus the individual seller of minerals is unable to establish his sales prices. Except where a monopoly is present, he must sell at the going market. His option is to abstain from selling if he finds the price unremunerative. In past recessions, some mineral producers chose to do precisely that-either accumulating a substantial share of their output in inventory or, in prolonged downturns, abstaining from production. During the current recession, however, private-sector mining companies did not have the option of accumulating inventories to any great extent. Capital costs for new mineral projects or for expansion of existing facilities have escalated at an alarming rate since the early 1970s. Added to this has been the heavy cost of installing pollution control or safety equipment to comply with the regulations adopted in most industrialized countries (and particularly the United States) since 1968. The consequence has been that the financial position of most major mineral enterprises in mid-1980 was already strained. To finance increased inventories meant incurring additional funded debt at high interest costs, thus impairing the concern's credit rating. Management Choices Private-sector managements have had to face up to the alternative of either continuing to produce at an unchanged rate and marketing output at unremunerative prices or reducing output. The latter has meant either operating at a curtailed rate, with con-

Jan 3, 1983

By William Gleason

"Ed Rapp is among those who believe in the saying that necessity is the mother of all invention. Rapp is the president of Caterpillar’s mining group. As such, he is tasked with leading the world’s largest mining equipment maker, and its customers, through this time of lower commodity prices, while also positioning his company to be prepared for better days that lie ahead.The decade-long mining boom fueled by growth in emerging markets and demand for commodities that led to record prices for some metals paused in 2008 with the global financial crisis. However, according to Rapp, thanks to stimulus packages around the world, and in particular the stimulus from China that was focused on infrastructure, the mining sector recovered fairly quickly, and from 2010 to 2012, mining was strong.And then the stimulus stopped. Credit dried up and global growth began to slow down and, in the three years since, commodity prices have declined by an average of 60 percent. Caterpillar expanded during the boom, acquiring Bucyrus, and investing billions into the mining sector. It has felt the pinch of the slowdown as much as any mining company in the world. These pages, and those of other mining publications as well as mainstream media, have been filled with stories of doom and gloom about the industry. But Rapp, while acknowledging that the difficult times have been painful, also said Caterpillar sees opportunity in the slow down and reaffirmed his company’s commitment to the mining industry as absolute."

Jan 1, 2014

Controlled-blasting experiments in small development drifts were conducted at CANMET's Experimental Mine in 1992 and 1993. The objective of these experiments was to develop suitable controlled-blasting techniques for small development headings that are drilled by jackleg with 32-mm-diam holes. The experimentation was also aimed at providing insight into blast-damage mechanisms. Particular attention was given to the physical-mechanical properties of the rock and the rock-mass structural data. The drift faces were approximately 2.4 by 2.4 m (7.9 x 7.9 ft) in size with 36 to 43 holes drilled to a depth of 2.4 m (7.9 ft). Cartridged water gels, emulsions and semigelatin dynamite were used in the cuts and as primers, ANFO was used as the main explosive and decoupled 19-mm (0.75 in.) diam semigelatin dynamite charges were used in the perimeter holes. Smooth-blasting techniques and presplitting were tested in the underground mine. All of the blasts were monitored with a multichannel blast-vibration monitor, to which was attached sets of high frequency geophones and accelerometers. These experiments demonstrated the efficiency of controlled-blasting techniques for the reduction of blast damage and also demonstrated the need to improve the safety and efficiency of using explosives.

Jan 1, 1997

By G. Brofas

The reforestation potential of bauxite mining spoils by seeding was examined on this research work. The experimental plot was established on the location Strofi Koukouvista 5, Ghiona Mountain. The experiment consists of 3 species (Pinus nigra, Robinia pseudoacacia, and Spartium junceum) with 4 sowing treatments and 2 sowing seasons (autumn and spring). The treatments were: (1) broadcasting; (2) broadcasting and soil cultivation; (3) broadcasting with straw mulching and straw binding with asphalt emulsion; (4) broadcasting with soil cultivation, straw mulching and straw binding with asphalt emulsion. Third year results show that spring is better than autumn as a sowing season. Only the Spartium junceum species were found to germinate and survive in autumn. The results are better for all the species on the spring seeding. The most effective treatments for Robinia pseudoacacia and Pinus nigra are 3 and 4 while for the Spartium junceum even simple broadcasting shows good results although the best ones are achieved with treatments 2, 3 and 4. The paper?s findings show that reforestation by sowing could be effective for some species but further experimentation with other species is recommended. Concerning Robinia pseudoacacia, testing of different seed preparation treatments is needed in order to maximize the germination of seeds.

Jan 1, 2002

By J. Casado

This paper presents the results of an analysis and summary of relevant literature on the mechanism of cementation of metals in acidic aqueous media, with the aim of reconsidering the conventional assumptions. The simplicity of the process as a mere galvanic metal displacement is discussed, and the real effects of pH and hydrogen pressure in different cases assessed. Finally, an alternative mechanism scheme with respect to the role of hydrogen species, in agreement with reported data, is proposed.

By J. C. Norman

The boron review arrived too late to appear in the June issue. The United States was the world's second largest producer and the largest consumer of boron compounds during 1991. According to the US Bureau of Mines, boron mineral concentrate and chemical production in the US totaled about 1.1 Mt (1.2 million st), yielding about 608 kt (670,000 st) of BO, in 1991. Total estimated value was $440 million. That level of production was equal to 1990 revised production figures. Value was greater by $37 million, however, reflecting a strengthening of boron product prices. The US continued to supply essentially all its own boron while maintaining a strong position as a source to foreign markets of sodium borate products and boric acid. Domestic employment in the mining and beneficiation of boron products in 1991 remained at 1100 people, about the same level as in 1989. The Bureau of Mines estimated total world production of boron in 1991 - mineral concentrate and chemical - at about 2.9 Mt (3.2 million st). That corresponds to about 1.2 Mt (1.3 million st) of BO ,. World production in 1991 was about equal to revised 1990 levels. US production Mines and processing operations in southern California were the only domestic sources of boron mineral concentrates and chemicals in 1991. US producers, in order of quantity of production, were US Borax and Chemical Corp., North American Chemical Co., and American Borate Co.

Jan 1, 1992

By Liming Yuan, Wei Tang, RICHARD THOMAS, DAVOOD BAHRAMI

The location and orientation of fire suppression nozzles is critical in suppressing mobile mine equipment fires. To effectively suppress such fires, optimization needs to be considered for the suppression nozzle locations and discharge angle. Detailed experiments were conducted to study the effectiveness of fire suppression agents with different nozzle configurations. A variety of fire suppression systems including dry chemical, wet chemical, dual agent (dry and wet chemical), carbon dioxide, and water mist were used. Six types of nozzle locations were studied, and their fire suppression effectiveness were compared. Results from this work highlight potential considerations when determining effective fire suppression designs.

Feb 1, 2025

By E. Craig Simmons

Uranium is an element incompatible with respect to the major rock-forming minerals crystallizing from granitic magma, entering in- stead trace minerals such as zircon. The relationship between the saturation limit (SL) for such a mineral and the bulk distribution coefficient (Do) for U is central to understanding the distribution of U and its availability to late- stage fluids which can form ore deposits directly, or labile U which can be remobilized later. Low SL values imply early crystallization of zircon, but in very small proportions, minimizing Do and maximizing the degree of enrichment of U in late-stage fluids. Thus, granitic rocks with low Zr contents (due to a low saturation limit for zircon) are most likely to evolve U- enriched differentiates; this will be reflected in a high U content of the zircons (but not necessarily high U abundances in whole-rocks). Thus, the ratio of the U content of zircon to the Zr content of the corresponding whole-rock is potentially a very useful parameter in identifying granitic rocks which are most likely to have U-enriched solutions associated with them. The granitic rocks associated with the U deposits of the Midnite Mine area, Washington, have geochemical characteristics which fit very well the model presented here. The rocks are very low in Zr (100 ppm) and contain zircons with extremely high U contents (3,000-4,000 ppm).

Jan 1, 1981

By E. G. dos Santos, M. M. Veras, C. H. Sampaio, A. S. Young, R. S. Paranhos, C. O. Petter, A. C. Bastos

"The major challenges of the current mining are the energetic optimization, the lowest water consumption and minimizing environmental impact. One technique that eliminates much of the waste avoiding milling sterile, operating without water and to decrease the generation of waste at the end of the process, must be considered a major innovation. One of the most important developments in these past 10 years in the mining industry was expanding the use of high-tech sensors aimed at pre-concentration of ore. Among the mining areas where this type of technology is booming is the industrial minerals. The most common sensors are color sensors with Charge – Coupled Devices (CCD cameras) allowing through the RGB colorimetric system, the separation of minerals with different hues, and in many cases, a difference in brightness. More recently, the development of the use of dual energy X-ray transmission (DE-XRT) Dual Zone allowed the separation by atomic density of the mineral constituents of the rock. This paper presents a review of these two techniques (CCD and DE – XRT) as well some results showing the use of these two techniques for Earth Rare and Limestone. INTRODUCTION The mining industry is going through one of its biggest technological changes since the industrial revolution by the implementation of new technologies, according to Australian Mining Magazine (2015), whose theme emphasized one of the 10 greatest challenges that mining will face in the coming years. Optimization of the energy matrix in mining is focused on reducing water consumption and minimizing environmental impacts. The implementation of sensor technologies (Sensor-Based Sorting - SBS) allows elimination of mill tailings and permits the mill to operate with reduced use of water or totally eliminate this consumption (Young et al, 2016). According to Jönsson (2014) mining has undergone striking changes with the expansion of sensors of high technologies applied in the pre-concentration of mining ores. These techniques have contributed over the past 10 years in the recapture of mining areas with emphasis on the environment and/or operational optimizations. In line with the requirements of technological innovation, the mining industry is forced to make improvements in gravimetric processes ensuring better levels of Run of Mine ore feed in beneficiation plants. The implementation of automatic sorting, assisted by dual energy x-ray transmission (DE-XRT) sensor technology, or charged coupled device (CCD) image capture camera technology in the feed plant, allows for the selective sorting of individual particles into pre-concentrations (Veras et al, 2016)."

Jan 1, 2017

By R. H. Snow

Although industrial size reduction methods have an energy efficiency of only about 1 percent, methods of size reduction have not changed much for many years. One reason for slow progress has been the oversimple viewpoint that a single law should exist to relate size reduction to energy input. Modern simulation methods decompose the grinding process into a grinding rate function (selection function) and a breakage function. The breakage function is difficult to measure, and it usually requires tracers if it is determined from milling experiments. Prediction of breakage functions from basic principles is one objective of this paper. In this study we focus attention not on the gross energy input to the experiment, but on the spatial distribution of stress energy within the particle. We are led to this viewpoint by experimental observations of a few previous investigators (Bergstrom2, Rumpf3, Axelson4) and our own observations. Oka and Hiramatsu recently used their calculations of stress within particles for prediction of breakage, but again they tried to correlate the size of the fragments with the total stress energy, rather than the approach we propose. We assume that the stress energy is stored in the interior of the particle as the load is increased, until the particle breaks. We assume that each element of the particle breaks into fragments of a mean size that depends on the locally-stored stress energy. The size distribution of fragments is the computed from maps of the stress-

Jan 1, 1972

By M. L. Sharrah

Communication about the energy problem has come at us in great profusion during the last couple of years--reports, speeches, editorials, advertisements--and events. Events such as the Arab embargo on oil exports which vividly demonstrated the world's dependence on oil, a finite and nonrenewable resource. And the three-fold increase in the price of oil which provides a constant reminder of the political and economic implications of dependence on foreign oil. A distinction among countries exists today which was almost inconsequential two years ago--the oil exporting nations and the oil consuming nations. The only rational way for the consuming countries to lessen the political and economic clout of the OPEC group is to reduce their dependence on oil. The United States is capable of playing a significant part in such a move for several reasons.

Jan 1, 1975

By Christopher J. Farrow

This paper describes the grinding circuits installed at two remote sites in northern Canada. One is Cominco's Polaris Project at Little Cornwallis Island; a barge-mounted lead/zinc concentrator. The other is Echo Bay Mines' Lupin Project at Contwoyto Lake, 400 km northeast of Yellowknife, a gold mine, all components of which had to be flown to the site. Logistics and considerations of operating and maintenance presented challenges which were met by innovative design. The evolution of the grinding circuits is discussed. Both plants are operating at design throughput.

Jan 1, 1983

By Robert Klug, Nils Engelke

"In order to extract proportionately small quantities of valuable minerals, mining companies move large amounts of earth. A resulting waste product of this process has traditionally been stored in a semi-liquid phase known as tailings, typically stored in a large pond created by an earthen dam at the low end of a drainage basin. It is generally expected that these dams are stable enough to withstand the pressure of the stored material. Unfortunately, history shows us that this is not always the case. The Baia Mare dam in Romania failed in 2000, causing tragic and prolonged environmental damage to several major European rivers. The Bento Rodrigues dam in Brazil failed on Nov. 5, 2015, and that event resulted in the loss of 16 lives.In hard rock mining, many minerals are imbedded within the ore. As part of the mining process, valuable minerals are extracted from the ore; often, the mineral content is only a fraction of the total ore volume processed. To extract the minerals, the ore is typically crushed and pulverized into very fine particles, then wetted to form slurries. The minerals are extracted from the slurries through a series of flotation and/or sedimentation steps with the aid of water-soluble separation chemicals typically known as reagents. Following the mineral extraction, the resulting residual wetted ore cuttings are labeled as tailings. At the end of the extraction process, the tailings are in a thick semi-fluid sludge state, often with trace elements of the extraction reagents.Historically, these tailings are deposited in giant basins or sludge ponds, where they pose a great threat to the environment while binding large volumes of waste process water.Process water recovery and achievingdry tailingsCurrent generation engineering studies, trials and successful field implementation have shown that an alternate process known as dry stacking is practical. The dry stacking process deposits dewatered tailings into containment areas that are smaller in overall footprint and significantly safer by reducing the transfer of reagents into the tailings storage area. In addition to achieving the dry tailing benefits mentioned, it is possible to recover valuable process water while dewatering the tailings sludge utilizing modern separation technology."

Jan 4, 2018

By C. L. Wilsey, K. M. Oakes, W. J. Reich, M. J. Protani

The time frame required to complete the National Environmental Policy Act (NEPA) process for a new mine or the expansion of an existing mine can range from nine to 24 months, or even longer. The time frame will vary depending on whether an environmental assessment (EA) or an environmental impact statement (EIS) will be completed Completing properly designed baseline studies to collect natural resource data to support the EA or EIS prior to the start of the NEPA process can shorten this time frame. In this paper, a two-year natural resource baseline study by Homestake Mining for the Ruby Hill Mine, Eureka County, NV, is used as a case study to describe how a properly designed and executed natural resource baseline study streamlined the NEPA process.

Jan 1, 2003

By L. Yuan, J. H. Rowland, R. A. Thomas

"Hydrogen (H2) gas released during battery charging can result in cross-interference for carbon monoxide (CO) sensors used for early fire detection and compromise the integrity of the mine atmospheric monitoring system (AMS). In this study, a series of laboratory-scale and full-scale experiments were conducted to evaluate the responses of different CO sensors to H2 gas. In the laboratory-scale experiments, constant H2 concentrations in the airflow, from 100 to 500 ppm, pass through sensors. While in the full-scale experiments, increasing H2 concentrations generated as a byproduct from charging the batteries at the battery charging station rise to the sensors under different ventilation scenarios. The H2 concentrations at the CO sensor location were measured using H2 sensors and were correlated with the CO sensor response. The effects of ventilation and sensor location on the CO sensors responses were also analyzed. The results of this study can help mining companies to select appropriate CO sensors and improve the deployment of these sensors to ensure the safeguard of underground miners. INTRODUCTION As many types of battery-powered mining equipment such as scoops and shield haulers are used in underground mining operations, charging stations are required to charge the equipment batteries. These batteries are of lead acid chemistry. A safety issue exists with the battery charging stations as all lead acid batteries produce flammable H2 gas during the normal charging process. Overcharging or excessive heat can quickly cause batteries to produce even more H2. If H2 is not appropriately diluted or dispersed, it builds up, and the risk of fire and explosion increases. Mine Safety and Health Administration (MSHA) regulation (30 CFR Part 75.340) requires that battery charging stations should be housed in noncombustible structures or be equipped with a fire suppression system. When a fire suppression system is used, the battery charging stations must be ventilated with intake air that is directed into a return air course or ventilated with intake air that is monitored for CO or smoke using an AMS. The monitoring of intake air ventilating battery charging stations should be done with sensors that are not affected by H2."

Jan 1, 2018