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By Qing-Wang Hao

In this paper, the authors attempt to develop engineering based approaches for estimating safety factors against pillar and floor failures and predicting likelihood of subsidence events over abandoned coal mines in Illinois. There are two critical problems involved in the analysis: determination of geotechnical properties, and consideration of time effect. The authors attempt to solve the problems by generating hypotheses, which are used to modify existing engineering models for estimating pillar and floor safety factors. The modified models are validated using data from two well established databases of subsidence events over active and abandoned mines in Illinois. The data analysis suggests that most of the trough type subsidence events in Illinois were caused by floor failures rather than pillar failures. The subsidence incubation period seems to be directly related to initial floor safety factors at the time of mining. This correlation can be used to predict the likelihood of subsidence and to assess subsidence risks within both spatial and temporal contexts where detailed mine maps are available.

Jan 1, 1986

By J. A. Marts, R. C. Gilmore, Jr. Bogin, S. A. Saki, J. F. Brune, J. W. Grubb

"Most, if not all longwall gobs contain explosive gas zones (EGZs), i.e., zones of explosive methane-air mixtures that can cause – and have caused – mine fires and explosions. If the coal is prone to spontaneous combustion, oxygen penetration into the gob must be avoided. This paper summarizes the significant research findings from five years of computational fluid dynamics (CFD) modeling research conducted at the Colorado School of Mines (CSM) under funding from the National Institute for Occupational Safety and Health (NIOSH). CSM Researchers have developed CFD modeling techniques to identify where and under what circumstances EGZs can form in longwall gobs and how EGZ formation and oxygen penetration depend on the ventilation method, face and bleeder ventilation parameters, injection of inert gases and the operation of gob ventilation boreholes. Recognizing these explosion and fire hazards is an important first step in improving the safety of longwall coal mines. CSM modeling research has shown that EGZ formation can be effectively controlled by adjusting ventilation parameters, choosing the proper ventilation pattern and injecting inert gases where necessary. INTRODUCTION In a project sponsored by the NIOSH Office of Mine Safety and Health Research, researchers at the Colorado School of Mines have examined gas compositions and flows in longwall gobs in order to assess explosion and fire hazards. Since gob areas are inaccessible, researchers developed a series of computational fluid dynamics (CFD) numerical modeling tools to characterize these hazards. A variety of CFD models were developed to cover progressively sealed as well as bleeder ventilated gobs for both coal and trona mines. The explosion and fire hazards posed by EGZs in longwall gobs can be summarized as follows.• If the EGZ lies closely behind the longwall face, flames and pressures from an explosion can penetrate the shield supports and reach the active face area, creating blast trauma, burn hazards and toxic, unbreathable atmospheres. • EGZs can be pushed around inside the gob by roof collapses and cave-ins. If they get pushed out into the face area, sudden methane inundations and explosion hazards in face areas can result. • Fresh air flowing into the gob can create an explosion hazard as the gas composition in the gob moves from fuel-rich inert to explosive, creating EGZs. • Ignition sources inside the gob can be frictional ignitions or spontaneous combustion. • Bleeder ventilated gobs are surrounded on all sides by an EGZ that forms along the fringe areas between the fresh-air ventilated bleeder entries and the methane-rich interior of the gob. It is suspected that diffusion flames can propagate rapidly along these EGZ fringes if an ignition occurs"

Jan 1, 2015

By Matthew Preedy, Anthony Pooley, Mike Wongkaew, Dirk Bakker, Raghu Bhargava

Sound Transit’s ST3 program will add 62 miles of light rail to the Puget Sound area, including connections to the neighborhoods of West Seattle and Ballard. These connections include considerations for both elevated and tunnel alternatives in West Seattle and Ballard, as well as a new tunnel and six underground stations in the densely developed downtown Seattle. This paper describes the conditions and constraints along the corridor, and the latest development in the ongoing process to plan the underground guideways and stations.

Jun 13, 2023

By E. Fahrenkrog, D. Sbartaro, E. N. Cifuentes

An intelligent supervisor using expert system tools and applied to a crushing plant has been developed with a structure based on a model of a human operator. It consists of a knowledge base containing a qualitative model of the process and a rules base with the heuristic logic used by an operator when supervising a plant. The simulation results obtained show the potential of this type of system to supervise the automatic operation of a plant. There has been very significant development in artificial intelligence over the last two decades. Within this development, two approaches can be distinguished, (Winston, 1984). The "model approach," in which the main objective is to understand and model the be¬havior of living systems. The second approach is the "engineering approach." Here, systems capable of performing tasks usually requiring human intelligence are created. As part of this latter approach, knowledge engineering and its main achievement, expert systems, have been developed. Expert systems arose from the need to incorporate the abilities of a human expert in solving realistic problems in which the conventional approach has great difficulties. The first successful applications of expert systems were in medical diagnosis, geophysics, and fault detection. However, since 1971, when Fu (1971; defined intelligent control as the inter action of artificial intelligence and automatic control, some significant developments in the use of artificial intelligence tools for process control have been achieved (Astrom, 1986; Pinto 1988; Fahrenkrog, 1988; and Porter 1987). The modern control theory has made important advances. And, although successful in some applications, it has failed to cope with the practicalities of many industrial processes. As a result, the automatic operation of a plant has been confined to a small region around a normal operating point and to periods without any great disturbance. One of the main reasons for this is the lack of accurate and structured knowledge of the processes involved. Despite this, operators applying their knowledge, experience, and a little intuition, often obtain good results controlling the plant in such situations. Considering the above, the next obvious step is to include similar reasoning capacities in a computational system. The development of such an expert supervisory system prototype applied to a mineral crushing plant is presented. Problem description The problem is to conceive a control system with the ability to handle quali-

Jan 1, 1989

By Felicia F. Peng

In operation of column flotation of fine coal, the smaller bubbles are required to effectively recovery of fine hydrophobic particles. However, smaller size bubbles alone does not ensure an efficient flotation for fine particles. The sufficient available bubble surface area per unit column are essential for effective column flotation. The experiments are conducted in a lab-scale column using two different bubble size distributions and three different particle size distributions for flotation of Pittsburgh No.8 seam coal. The interaction between particle size, aeration rate, feed rate and wash water addition are examined in this investigation to establish the optimal operation conditions for flotation of fine coal. Despite of wide range of operation conditions used in this study, it is found that the experimental data fall in a single characteristic recovery-ash curve for a given bubble size distribution and particle size distribution. The major parameters affect the flotation performance points along -the characteristic recovery-ash curves are aeration rate/frother dosage, feed rate and wash water rate-.

Jan 1, 1994

The objective of the fines flotation step in a coal preparation plant is to maximize coal recovery subject to a constraint on the allowable ash in the concentrate. The objective is achieved when the incremental ash is driven to a target value determined by an economic constraint. In this paper, a phenomenological flotation model and ash analyzer combination are identified that allow the development of a soft sensor for incremental ash and subsequently a model-based strategy which manipulates key flotation variables to achieve the control objective. A combination of plant tests and computer simulations are presented to evaluate control-system performance in one operation.

Jan 1, 1999

By Youning Li, William J. Drury, Christopher H. Gammons

A demonstration scale, subsurface flow anaerobic wetland was built to treat zinc and other metals in surface drainage near the historic mining center of Butte, MT. Based on three years of continuous monitoring (1996-1998), copper and cadmium were effectively removed year-round, but attenuation of dissolved zinc was dependent on hydraulic residence time (HRT) and bacterial sulfate reduction (BSR) rates. BSR rates decreased in winter months, as did HRT due to the development of thick frost zones in the substrates. An additional problem was the inability of the wetland substrate to completely filter out fine-grained particles of ZnS forming in the anaerobic cells.

Jan 1, 2000

By David M. Stearns

Introduction Millions of tons of coal are shipped by rail each year in the US. Loading those trains efficiently is a topic being studied by coal producers and railroads. Alternatives range from volumetric loadouts to systems that weigh the product, using either belt conveyor scales, track scales, or weighbins. Each system has its proper application and each has pros and cons, depending on the volume, nature, and layout of the specific loading facility. In recent years, a batch weighing system has been developed that offers significant benefits to higher volume operations shipping by a unit train. The Unitrain Loadout System (ULS) features a precision electronic batch weighing system married to a mechanical loadout system by a microprocessor-based digital control system. A batch weighing loadout could be designed using analog electronics or even a mechanical weighbin. But it is the adaption and use of a microprocessor that provides the primary benefits of a unit train loading facility. Those benefits are accurate weight determination, optimum car use, overload prevention, speed in loading, optimum labor use, and documentation of the loading process. Unitrain History The first ULS was erected for iron ore applications in Canada during the 1960s. The first domestic system on coal was installed at Pittsburg and Midway Coal Co.'s McKinley mine at Gallup, NM, in 1978. At present, there are more than 20 Unitrain Loadout Systems in operation worldwide. They are loading minerals, concentrates, and coal. Eleven systems are presently in service or under construction in the US. In the last several years, a number of comparable systems have also been installed. As a result, the concept has been well proven and is now commercially available from several sources. Unitrain Operation The basic operation of a ULS involves loading a unit train with individually weighed batches of coal while it moves slowly under a loadout tower. Typical coal systems are designed to load at rates of 2.7 to 6.3 kt/h (3000 to 7000 stph). The contents of each car can be accurately weighed. This meets the requirements of the National Bureau of Standards Handbook No. 44 for static weighing. Also, cars can be loaded within very close tolerances. This optimizes railcar usage and prevents overloads. Principal components of the loadout system are the main feed conveyor, the surge bin, surge bin gates, weighbin, weighbin gate, flood loading chute, control room, calibration weights, and hydraulic and electrical systems (Fig. 1). Main feed conveyor: Coal is delivered from a storage area by the main feed conveyor. The conveyor fills the surge bin. It should be capable of conveying coal at the same rate at which it is being loaded. Usually the feed conveyor is equipped with a conveyor scale that can display rate in the control room and control feed to the belt. The surge bin will typically store 227 to 272 t (250 to 300 st) of coal. If the loadout is installed in an over-the-track silo, there is no need for a surge bin. Four double-bladed, hydraulically actuated gates are incorporated into the bottom of the surge bin. These gates open to fill the weighbin. Automatic pre-act points are selected by the control system. They shut these gates as the desired weight is approached. The final amount of coal is added by a single gate that closes. This results in a weighed batch of coal within ± 0.5% of the selected optimum load per railcar. Thus, if loading 91-t (100-st) capacity cars, the system is set to batch up 90.2 t (99.5 st) batches. Each car is expected to be loaded between 90 and 91 t (99 and 100 st). Weighbin: The weighbin is next in the flow scheme. Typically, it is

Jan 3, 1985

By Levent Ozdemir, Gerald Dollinger

An extensive series of linear and rotary cutting tests were run in soft and medium strength rocks at the Earth Mechanics Institute of the Colorado School of Mines to investigate the possibility of very high speed mechanical excavation for tunnel, raise, and shaft boring. The results of these tests demonstrate that cutter penetrations of 38.1 mm (1.5 inch) and cut spacings up to 228.6 mm (9 inch) are possible in such rock without exceeding the bearing capabilities of the cutters. It was also demonstrated in vertical boring tests that continuous excavation rates up to 38.1 m/hr (125 ft/hr) can be achieved with state-of-the-art technology provided sufficient thrust and torque is available. A predictor model for soft rocks was also developed using the test data. Analysis of this model shows that the errors between the predicted and observed cutter normal loads appear to be independent of cutter diameter, tip width, cut spacing, and depth of penetration. This suggests that the structure of the model is correct with respect to these variables. An analysis of the coefficients in the model was also made and a correlation found between the principal coefficient and Unconfined Compressive Strength. The second coefficient in the model was found to be similar in magnitude to rock properties such as Brazilian Tensile Strength, Shear Strength and Point Load Index.

Jan 1, 1989

By Gerhard Lang

"Slurry Microtunneling is a well-established technology building on over 20 years of experience in successful tunnel installations under all kinds of soil conditions across the U.S. and Canada. Recent microtunnel installations prove that initial hesitation, e.g. curved drives, is fading and long-distance pipe jacking projects as well as lake outfalls are being considered. One of the younger technologies is Direct Pipe®, which combines the benefits of HDD and Slurry Microtunneling. It fits exactly into the area where HDD is not feasible or too risky to apply. The paper points out the benefits of the Direct Pipe® technology for owners, engineers and contractors and discusses the latest developments of Slurry Microtunneling for long-distance, curved drives and sea/lake outfalls with wet recovery of the equipment such as on the ‘Keswick Outfall Project’ in Ontario. The first Direct Pipe® installation in the US was executed in August 2010. Since then, another 22 crossings have been carried out amongst a total of more than 60 Direct Pipe® crossings worldwide. INTRODUCTION Pipelines installed underground are indispensable for supplying the growing world population with water, oil, gas and electricity, for removing wastewater and for providing functioning telephone and communications networks. During recent years the limits of trenchless applications have been permanently shifted, leading to higher and more stringent project requirements and consequently new technologies, either as further development of existing methods, or through the development of new methods by incorporating elements of proven technologies. MICROTUNNELING TRENDS IN NORTH AMERICA Slurry Microtunneling has a wider geological application range in comparison to EPB and hard rock Microtunneling. The Slurry MTBM can be equipped with specific cutting wheels to cope with different soil conditions. The most flexible and most often employed type is the mixed soil cutting wheel, which contains a mixture of disc cutters as well as scrapers for varying soil conditions from cohesive soils (clay, silts) to highly permeable soils including sands, gravels and cobbles and even hard ground formations such as rock and boulders. A detailed geotechnical report provides the appropriate data to configure the MTBM and its features to the ground conditions expected. Mixshield or hydroshield (AVN/AVND) MTBMs in particular, can be safely operated with little overburden (~ 3-5 x machine diameter) and minimum risk of frac-out or settlement on the surface. This is especially beneficial in urban areas with sensitive buildings or for river crossings with protected fish habitats."

Jan 1, 2016

By Prasad Kummarapurugu, Maija Teijonsalo, Sirkka-Liisa Jamsa-Jounela

There has been a significant progress in the use of mathematical modeling and simulation in the minerals industry in the last decade. Process models have moved from academic world to important industrial tools. This paper reviews the status of mineral processing simulators and recent progress in simulator development and applications is discussed. The simulation for process design and optimisation is now an established technique, as evidenced by its increasing use of practising engineers through commercially available simulator software. The paper presents a systematic approach to the process study procedure for the control system development, clarified by practical case examples calculated by SimCon - a novel steady-state simulator for mineral processes. Examples of the application of SimCon in drawing flowsheets, calculating mass balances and making simulations for grinding and flotation processes are presented. At the end of the paper, the state-of-the-art and the future of computer-aided pro- cess study at mineral processing plants is discussed. Keywords: Simulators, modelling, object oriented programming, computer aided control system design

Jan 1, 1996

By E. Topuz, M. J. McPherson, I. M. Konduri

The research is carried out to investigate the flow mechanics and effectiveness of face ventilation using induction fans, as an effort to provide a more efficient alternative to conventional auxiliary duct or brattice ventilation systems. The induction effects and plume longevity of fluid jets are being studied with the help of a plexi-glass model, using water as the fluid medium and creating a system that is dynamically similar to the flow in mine headings. This scaled model represents a typical 1.5m x 6m x 25m heading connecting to a crosscut. Reynolds Number criteria are used to obtain dynamic similarity of the flow in the designed model to simulate real mining conditions. The role of various parameters such as nozzle position in three dimensions, airway roughness, nozzle geometry, and flow rate in the jet are studied. During the laboratory tests, flow visualization techniques, coupled with still and video photography, were employed to identify the flow patterns. The results indicate that in typical coal mine headings, jet fans can produce effective face ventilation for distance up to 30 meters.

Jan 1, 1995

By J. A. Madonna

Universities and colleges in three countries, Australia, Canada and the United States, recognized the need to establish and/or reorganize geoscience programs at the vocational and two-year technical levels. To accomplish this goal, a cooperative study with industry in one state or province from each country was initiated. These include 1) Tasmania, Australia, 2) British Columbia, Canada and 3) Alaska, United States. Over one hundred mineral industry organizations cooperated in the study by providing information regarding their specific training needs for support personnel. The data gathered has been used to identify training areas for semi-skilled, skilled and technical personnel in geochemical mineral exploration, including, but not limited to, geological skills, geochemical skills, environmental skills and computer skills. With the areas of major educational need defined for geochemical exploration, an educational field skills model has been developed for the three levels of training. The depth of each level of education and the training objectives for the work force at each level will be discussed.

Jan 1, 1993

By M. D. Banghart

The Republic of South Africa is an outstanding example of the benefits to a new land by the application of individual enterprise, capital and know-how. While South Africa was colonized by European and Bantu people some 300 years ago, it was only 70 to 80 years agog when diamonds were discovered at Kimberley and gold on the Witswatersrand, that the mining, industrial and commercial potential of the country began to emerge. South Africa s national income rose from R1, 200 million in 1945 to over R4 billion in 1960 (1R = 10 shillings = $1.40 U. S.) The annual national income per head of population -- including all races -- is currently R254 (£127) This compares with £24 for India., £30 for Nigeria, and £50 for Ghana. Allowing for the increase in population, the increase in real income per head of population was about 40% during the past 15 years.

Jan 1, 1962

By V. Svalbonas

In the establishment of a useful failure criteria for complicated, fabricated structures, two basic areas of knowledge must be evaluated: 1. The accuracy of the applied stress analysis must be known in comparison with actual stresses encountered during mill operation. 2. The metallurgical fracture properties of the basic materials must be established with reference to non-destructive examination (NDE) methods to be used during fabrication. Both of the above can only be evaluated by use of full scale tests on the structures, and/or components, of interest. This paper describes such tests and comparisons as applied to several large mill installations. In addition, weldment component fatigue tests arid flawed casting strain gauge tests are also discussed. The combination of such test results allows for the formulation of failure criteria directly applicable to the fabrication and examination procedures followed in grinding mill structure manufacture.

Jan 1, 1982

By William Gleason

"It has been more than 10 years since Montana Resources’ copper/molybdenum mine has had a lost-time injury at its site in Butte, MT. With more than 350 employees and an average production of about 15.5 Mt/a (17 million stpy), which includes 29.5 kt (65 million lbs) of copper and 4 kt (9 million lbs) of molybdenum, the mine’s journey to a decade of exemplary safety is an impressive feat that has required hard work, commitment and, most of all, leadership from every level of the operation.It has not always been an easy journey, nor has it been one without scrapes and bumps along the way, but it is one that has produced stellar results. Mike McGivern, vice president of human resources, and Pete Steilman, safety manager at the mine, spoke with Mining Engineering about how the operation transformed from a site that was accustomed to collecting citations for safety violations to one that is now collecting awards for its safety record.Simply put, Montana Resources has made safety a value and the people its top priority.The operations faced many predictable challenges in 2003, when the mine was being brought back online after three years of sitting in care-and-maintenance status. It had been shuttered in 2000 because of low commodity prices and high operating costs, and, in the three years that the mine was idled, the equipment became dilapidated, and some of it was no longer in compliance. Less than half of the workforce returned to the site for the restart, and the team was challenged with getting the gears turning again to produce copper and molybdenum. But the most daunting challenge of all of was keeping the workforce safe during the transition.In the first few years of operation the mine racked up citations from the U.S. Mine Safety and Health Administration (MSHA) at an alarming pace, so much so that in May 2006, Montana Resources received a letter from the MSHA District Office informing the company that the operation was being placed on the Potential Pattern of Violations list due to its excessive citation history and high rate of significant and substantial citations. It was clear that something significant had to be done to change the course of action at the mine."

Oct 1, 2019

By A. Zutshi

Production of CO2 is an inevitable consequence of burning fossil fuels, with the only CO2 sequestration technique feasible in the immediate future being its injection in various geologic media. This paper discusses the factors that influence the injection, movement, and storage of CO2 into deep coal seams, while simultaneously increasing the production of methane. The results of a laboratory-scale study to evaluate the movement of CO2 in coal, its ability to displace methane, and the capacity of coal to retain CO2 are presented. The findings are compared with observations at one of the two field-scale pilot operations practicing CO2 injection in coal. Finally, the paper summarizes the research issues that require further investigation.

Jan 1, 2006

By V. J. Kecojevic, W. A. Wilkinson

Mining companies are increasingly looking at Global Positioning System (GPS) technology coupled with 3D mine planning and visualization systems to deliver increased productivity and reduction in operating costs in drilling and blasting operations. Leveraging GPS into drill and blast operations requires that a drilling plan be developed and imported into the GPS to guide the operation to a planned and desirable outcome. State-of-the-art mine planning software systems provide the engineer with a 3D environment in which to design and visualize drill and blast plans. This paper discusses producing and exporting 3D drill and blast plans to GPS and how some coal companies are utilizing GPS and mine planning software technology in the drill and blast process.

Jan 1, 2004

By G. Chi, M. C. Fuerstenau, R. C. Bradt

Reduction of the total energy expenditure in mining and ore preparation processes was achieved by redistribution of the energy from the crushing and grinding steps to the blasting operation. Reducing the burden/spacing distance by 25% or increasing the charge length by 25% during blasting results in significant energy savings in subsequent comminution processes. The energy cost of mining and comminution is reduced by up to 10%.

Jan 1, 1995

By W. S. Sadik

This paper presents the ventilation design for an underground testing facility in a salt medium. The underground workings consist of two-12 ft. (3.66 m) diameter watertight shafts and approximately 6000 ft. (1830 m) plus of drifting. These facilities are designed for the purpose of providing access for an in-situ testing of a salt horizon in which a variety of hazardous and non-hazardous materials could be temporarily stored or permanently deposited. The ventilation system includes a design basis for gassy mine conditions and provides for the option of bulk air cooling and heating.

Jan 1, 1988