Search Documents

By M. A. Trevits, G. W. Luxbacher, L. D. Patts

"It is almost a given that post-disaster mine conditions will have compromised the mine ventilation system, resulting in a hazardous atmosphere in portions of the mine, and often complicated travel through debris fields and roof falls. Robotic technologies provide the opportunity to gather valuable information to assist decision making or lessen exposure to dangerous conditions. MSHA's Mine Emergency Operations Division (MEO) has utilized a fully permissible mine robot, the V2, for a number of years, constantly updating the unit as new technologies became available. The National Institute for Occupational Safety and Health, as part of the MINER Act Extramural Contract Program, examined the need for additional robotic units and ultimately funded three different types of prototype technologies: two robots, the Snake Robot and the Gemini-Scout, and a mine rescue robotic assist vehicle known as the ""Mule"". The Snake Robot is designed to be lowered through a borehole and to conduct surveillance (gas monitoring, video and audio) in the immediate vicinity, while the Gemini-Scout, designed to be deployed in the mine opening, serves as a more mobile and agile exploratory tool as compared to the MSHA V2 robot. The Mule was developed in response to needs expressed by mine rescue teams for a versatile remotely operated support vehicle and it will move from prototype to MEO utilization in the near future. This paper describes the development of the robot prototypes and discusses their limitations in the prototype stage, possible enhancements and potential applications, as well as the utilization of the Mule. INTRODUCTION The conditions in a coal mine may be dramatically altered after a mine fire or explosion. For example, the ventilation system may not be functioning correctly as control devices may be compromised or damaged beyond repair. The visibility in the mine opening may be limited due to accumulated smoke and dust. Roof support systems may be damaged or no longer functional. Equipment and materials may be strewn about the mine opening. Debris fields, blocked openings, roof falls, flooded areas, gas accumulations and active burning make it very difficult or impossible for those managing the post-event emergency to permit mine rescue teams to enter the mine to conduct search and rescue operations. With the evolution of robots and robotic assist technology there has been a proliferation of purpose-built units for the military, police and law enforcement agencies, urban search and rescue and those contending with hazardous environmental conditions. In each case, the technology used is designed to limit human exposure to the unsafe conditions or to provide access to areas under difficult conditions. For example, a specially-designed marine robot has been deployed into the damaged core of the Japan’s Fukushima Daiichi Nuclear Power Plant to assess the conditions of the containment vessels, where melted fuel is believed to have accumulated. Human access to the area is prohibited due to dangerously elevated levels of radioactivity [1]. Multiple robots were deployed in Amatrice, Italy, to assist in the response after the 6.2-magnitude earthquake devastated the town. The robots were used to explore two medieval churches that were severely damaged and deemed too dangerous for human entry [2]. Tactical robots are regularly used by police and law enforcement agencies when the conditions of the emergency place intervening officers directly in harm's way [3]."

Jan 1, 2018

By John L. Shafer

Often an in situ leach is the only practical economic method for copper recovery from small low grade oxide deposits. The decision to develop a copper property by an in-situ blast and leach is strongly dependent on ore grade, tonnage, hydrology, and the copper extraction and acid consumption rates. The inherent "leachability" of the ore will in part determine the desired amount of fracturing of the ore deposit by the blast in order to obtain a copper extraction rate that is economical. For the last several years Occidental Research Corporation (ORC), the corporate R&D for Occidental Petroleum has under-taken a modest effort to address the question of "how to best identify and determine the information necessary to predict and control the operation of an in-situ leach for the economic recovery of copper."

Jan 1, 1977

By Alan Bauer

In recent years there has been increasing interest in employing the technique of explosive casting in strip mines. Explosive casting, applied to dragline mining, describes the procedure whereby the overburden is horizontally displaced by blasting causing a portion of the material to be thrown into the previously mined cut. Therefore, it is not necessary to subsequently excavate this waste with the stripping equipment. In addition, allowing the overburden unrestricted movement during the blast most often results in improved fragmentation and enhanced machine productivity. The method is receiving attention because the capital and maintenance costs of stripping equipment has risen rapidly in relation to explosives costs. Improved productivity is necessary to maintain unit costs at an acceptable level.

Jan 1, 1983

By Jian Deng, Hehua Zhu, Lianyang Zhang

Rockburst is defined as a sudden and violent explosion of rock on the surface of a rock excavation. Rockburst has been regarded as the least understood and most feared hazard problem for underground rock excavations. Traditionally, rockbursts were classified into the strain, pillar, and fault-slip categories. However, rockbursts are also known to occur at stress levels well below the rock yield strength, in mines where the rock is far from brittle, or without the presence of geological discontinuities. A plausible explanation of rockbursts is buckling, which has been identified as one of the main mechanisms for rockbursts. It is observed that rockbursts are often induced by dynamic loadings (pulses) from adjacent blasting. Therefore, the present paper studies the effect of pulse shape and amplitude on pillar rockbursts induced by dynamic loadings from blasting using the method of numerical analysis. The governing equation of a pillar’s motion is set up and the mechanism of pillar rockbursts is investigated through a practical example. The results show that it is not the shape of a pulse but the impact energy to decide the occurrence of pillar rockbursts. If all other parameters remain the same, pillar rockbursts are more likely to occur when the pulse duration is longer. The parametric resonance and the perturbation of dynamic loadings are also found to play an important role in the occurrence of rockbursts. These insights would provide invaluable clues about the mechanism and for better control of pillar rockbursts.

Apr 26, 2022

By F. A. Baczek

The Electroslurry TM electrowinning concept has been incorporated into a process flowsheet for recovering copper from smelter flue dusts. The process has averaged 96% recovery of the copper as high-grade electrowon while at the same time removing a majority of the impurities that degrade drawn copper as a result of recycling flue dust and liberator cathodes: The dust is processed through several stages consisting of leaching, copper precipitation, Electroslurry TM electrowinning and waste liquor treatment. The process may be integrated into a smelter operation and become an effective and feasible means of maintaining good product purity.

Jan 1, 1980

By John H. N. Yen, James M. Marquardt, Larry H. Heflin

INTRODUCTION On February 17, 1995, WMATA Contractor J.F. Shea holed through the last segment of rock tunnels of the planned 103-Mile Rapid Transit System for the Washington Metropolitan Area Transit Authority. Through the joined efforts and cooperation between the owner and the contractor, the project was completed on time and within budget. The Glenmont extension is on schedule to open in Mid-1998. The complete 103-mile system is scheduled to open in 2001. WMATA’s earlier 19 miles of rock tunnels had been done since 1976 ? By drill and blast with heavy horseshoe steel sets, sets with shotcreting over wire-fabric by TBM and NATM. All rock tunnels were primarily in metamorphic gneiss and schist, part of an east coast lithology that outcrops in a band running from below Richmond, Va. To above New York City. The 5,400 ft. long twin six meter tunnels of the Glenmont line had been earlier de-signed in 1979 by URS of NYC using Jenny Engineering of Pittsburgh, Pa., as a tunnel design specialist sub consultant. Jenny had provided two alternative designs, one conventional drill and blast horseshoe and one for Tunnel Boring Machine. Funding considerations had put the design on the shelf and it was clear that the state of the art had led to improved design methods in the intervening years. Before URS was tasked to update their design in1992, the Authority reviewed its earlier hard-rock experiences in light of the funding mandate to complete each segment on a limited budget and an expedited schedule. Many factors considered and many opinions were in leading to a final decision to drop the earlier designs and redesign for a single designated means of tunneling. That method was the New Austrian Tunneling Method. The NATM had been used earlier on WMATA for both soft-ground and rock tunnels. In the public’s eyes the NATM had become inextricably linked with the use of PVC’s and filter material enveloping or partially enveloping the underground structures to give the holy grail of tunnels, a water-tight structure. Although this link of waterproofing methods with excavation and support methods was essentially severed, a general feeling of their interdependence no doubt helped lead to acceptance of the NATM decision because of the waterproofing design that accompanied it. The Authority decided to drop the TBM and conventional options and provide bid documents for NATM only. URS asked LAW Engineering of Atlanta to provide the NATM design of the tunnels and associated shafts.

Jan 1, 1997

By W. T. Robertson

My charge is to review briefly "Coal In The Electric Utility Industry - Present and Future." Thus, I will not dwell on the overall energy picture, other than to express what most others involved in the energy picture know - we're in trouble! Several years ago, speaking to another engineering society, I said, "Much has been and yet will be said and written about the energy situation in our Country." What an understatement! The energy question has reached crisis proportions and is a top priority item at the highest level of government, Unfortunately, it will be in that situation for some time to come. Many factors created this complex problem, and we all share some of the blame. But I am perplexed when I read in the popular press that environmental factors are unrelated to the energy crisis when I know this to be untrue. In the recent past all forms of energy have been cast in the role of villain, particularly coal with its problems of surface mining, mine safety, acid water drainage, sulfur content, and a multitude of other adverse factors relating to the environment in one way or another. As you know, the sulfur situation has led to the closing of numerous mines, resulting in the lessening of our mining capacity. Today, along the Eastern Seaboard, 60 to 70 million tons of coal are displaced by imported oil, primarily to meet air standards. Even in the Midwest, utilities sitting on enormous coal reserves are converting to other fuels or hauling low sulfur coal thousands of miles from the western Mountain States. [We will hear more about this coal from another speaker on the program this morning.]

Jan 1, 1973

By Alphonse C. Van Besien

It is doubtful if anyone knows precisely how many U.S. coal miners have been killed by roof falls. In 1931, 51 miners were killed by falls or rock in every 10-day period (Paul, 1). Roley (2) indicated that from 1882 to 1945, over 3,700 men were killed by roof falls in Illinois alone. During this 63-year period, roof falls accounted for 47.6 percent of the coal mine accident fatalities. Similarly, Price and Nolting (3) reported that during the 10-year period beginning in 1937, roof falls claimed over 50 percent of the lives lost in West Virginia coal mines. Over 150 miners died under fallen rock in West Virginia alone, in each of those years. Certainly, the statistics have improved over the years. The Theodore Barry Report of 1971 (4) indicated that during, the previous 4 years, fewer than 100 miners per year lost their lives to roof falls--in the entire United States. The improvement is less remarkable when it is realized that the accident rate has declined only as the number of miners employed underground has declined. The TRW Report (4) pointed out that although the number of fatalities in underground coal mining (from all causes) had been cut in half from 1956 to 1965, the fatality rate per thousand miners had remained virtually constant. The decreased accident rate was due not to a reduction in hazards but to a reduction in work force. Roof falls still claim approximately 50 percent of the lives lost in underground coal mines. Considering the increased underground production of coal which must result from our energy crisis, the environmentalists' pressure against strip mining, and our inevitably diminishing supply of strippable coal, it is apparent that some means must be found to reduce the number of lives claimed by coal mine roof falls.

Jan 1, 1973

By I. Demers, A. Blier, M. Mbonimpa, M. Benzaazoua, B. Bussière

The Doyon Mine in Quebec, Canada, evaluates the possibility of desulfurizing its tailings to produce material to be used as cover for the acid-generating tailings disposal site. Laboratory tests showed that a single-layer cover made of desulfurized tailings placed over reactive tailings can prevent the generation of acid mine drainage. Modeling with the software Vadose/W was used to optimize the design parameters, namely, cover thickness, water table position and residual sulfide content of desulfurized tailings following laboratory work. It was found that the optimal configuration includes a 1-m (3.3-ft) desulfurized tailings cover containing 0.8% S, with the water table kept at the interface between the reactive tailings and the cover. To maintain the cover performance to reduce oxygen flux toward acid-generating tailings even in the event of a long dry period, a sand layer is suggested to protect the cover from excessive evaporation. It is possible to reach the environmental objective for oxygen flux chosen for the Doyon Mine (10 mol/ m2/year) with the protective sand layer, even in extremely dry conditions.

Jan 1, 2009

By R. R. Hall

Tests were conducted to assess the potential of column flotation for beneficiation of a talc ore from Montana. This ere contained approximately 80% talc, with the gangue comprised mainly of chlorite, silica, and dolomite. A tributylamine, MIBC, and sodium silicate reagent suite proved effective for talc flotation. Rougher-cleaner column flotation in a continuous open-circuit produced a final talc concentrate which contained 0.90% Al2O3. 0.17% CaO, and 1.28% Fe2O3. These analyses represented impurity rejections of 77, 85, and 65%, respectively. Weight recovery for this open-circuit was 52%; however, weight recovery was estimated to be 75% with cleaner tailings recycle. Results from this investigation show that column flotation is a viable means for beneficiating talc.

Jan 1, 1990

By H. EI-shall

Bench top centrifuge is used to study the consolidation behavior of phosphatic clays. A mathematical model (based on first order kinetics) is developed to describe the relationship between the void ratio (at any time) and the effective stress. Permeability of the sediment as a function of the void ratio is also described. The obtained data are compared with that obtained by other consolidation testing methods. Centrifuge results indicate that consolidation data may be developed in a short period of time (hours) as compared to days or weeks when other techniques are used.

Jan 1, 1995

By F. Ansheng

Though it becomes increasingly important with the valuable minerals in their deposits tending to be fine and poor, the solid and liquid separation remains difficult especially when the particles are of micrometer size and of low density. Almost of all conventional thickeners result in that fine particles lose into overflows which often costitutes a loss of potentially valuable resources as well as an environmental hazard. The addition of flocculations may improve the settling of solids but may also not work well for the final removal of fine particles from the overflows (Ref.1).

Jan 1, 1990

By Daniel B. Brimhall

The research presented here was initiated to investigate the role of atmospheric oxygen in the leaching of copper waste dumps. The problem of increasing the recovery rate of copper from these dumps is or great importance considering there are by conservative estimate in excess of fifteen billion pounds of copper located in dumps in the western United States. At this time, there is an increased interest in recovering copper from these dumps on a large scale. Large tonnages of low-grade material are being placed on the waste dumps of most copper mining operations in the western United States each day. The size of these dumps ranges from 5.5 million tons at Mineral Park, Arizona, to 4 billion tons at Kennecott's Utah operation (1). Leach solutions are recycled and contain ferrous and ferric sulfates. Large quantities of dissolved aluminum, magnesium and calcium salts may also be present. To this solution make up water is added to maintain the solution inventory and sulfuric acid is added for pH adjustment. Iron is introduced into the leach solution by the dissolution of the iron-containing sulfide and oxidized minerals present in the ore deposit. In addition to the iron from dump leaching, iron is also introduced during the precipitation process when the pregnant solution is passed over metallic scrap iron if cementation is used to reduce the copper in solution.

Jan 1, 1972

By G. Soni

A first principle flotation model has been derived from the basic mechanisms involved in flotation. The model consists of a series of analytical equations for bubble generation, bubble-particle collision, attachment, detachment, and froth phase recovery. The model can predict flotation from both hydrodynamic and surface chemistry parameters such as bubble size, particle size, energy dissipation rate, ?-potentials, contact angles (?), etc. The model has been validated in a series of laboratory batch flotation experiments, in which mono-sized glass beads are used as feeds. The experimental results are in good agreement with model predictions both in terms of grade and recovery.

Feb 23, 2014

By I. H. Warren, F. A. Forward, D. E. Pickett, Ernest Peters, Alvin H. Ross, I. M. Masters, N. P. Finkelstein, R. Derry, A. W. Fletcher

In this section the chemical, physical, and mechanical principles of hydrometallurgical processes are developed and reviewed. Plant practice is not discussed other than to note the metals which are processed using the various systems that are available. These notations will permit the reader to refer to the appropriate section in Part II of the Handbook for specific details on a particular metal or mineral. The equipment used to accomplish the desired unit operation is de¬scribed. Comparative data are presented to illustrate performance characteristics of unit operations, process, and equipment. The economic efficiency of individual processes is outlined. Some of the chapters contain material that is covered in detail in other sections of the Handbook Such chapters are developed only sufficiently to indicate the specific application of the techniques to hydrometallurgical processes. In this section considerable cross-referencing to the other related sections has been done.

Jan 1, 1985

By Brian Fulcher, John Eastlund, J. B. Copeland

Following the completion of the 7,600 m primary access tunnel by Kiewit/Parsons Brinckerhoff (K/PB) in April 1997, an exploratory East-West Cross Drift Tunnel was constructed at the Yucca Mountain Project over the proposed future repository block for high level nuclear wastes. The 2,681 m (8,796 LF) East-West Cross Drift Tunnel was excavated through volcanic tuffs having zones of incompetent rock using a re-built Robbins 5.000 m (16’-5”) hardrock TBM with a special arrangement of supporting equipment. Details of the unusual site and contract conditions will be discussed as well as with the unique tunnel equipment specified by the Owner. This portion of the Yucca Mountain project required eight months to complete.

Jan 1, 1999

By E. Watkins, S. J. Schatzel, V. Gangrade, R. Kimutis, J. Addis, C. Hollerich

The recent shale gas revolution in the United States has led to the drilling of hundreds of unconventional shale gas wells in active and future coal reserves in traditional coal-mining regions of Pennsylvania, West Virginia, and Ohio. This paper summarizes the impact of a shale gas well breach on the mine ventilation system of an operating longwall panel. This study utilizes a 1:30 scaled Longwall Instrumented Aerodynamic Model (LIAM) to simulate a single-panel longwall operation. The LIAM will be utilized to identify flow pathways and distribution patterns of gas from breached gas well scenarios in an operating longwall in the Pittsburgh Coal Seam. Sulfur hexafluoride (SF6) tracer gas is utilized to simulate a breached gas well. Preliminary findings suggest that the breached gas is diluted to regulatory levels and does not accumulate in the mine entries or in the longwall gob when the longwall panel is adequately ventilated. Overall, this study characterizes the potential interaction between shale gas wells and the mine environment in the event of a gas well breach, which provides critical information to the industry and regulatory agencies for improving safety, health, and welfare of miners.

Mar 2, 2022

By H. W. Judges

A 16.5-kt/day underground molybdenum mine is being developed at Questa in Northern New Mexico by Molycorp, Inc., a wholly-owned subsidiary of Union Oil Company of California. Construction of the underground mine began in 1979, and first production is scheduled for early 1983. A gravity block caving method has been selected for mining the ore. Access to the mine will be through a service shaft, development shaft, and a conveyor decline. The shafts are being sunk under contract and the conveyor decline is being driven by Molycorp. The driving of the decline began in February, 1979 with a 10-man mining class. By the first of May, enough men had been trained to begin a continuous operation and by March 1, 1980 the face had reached the 1500 m mark. The heading is being driven with trackless rubber-tired equipment using a three-boom drill jumbo, 2.7 m3 LHD units and 7.3 m3 trucks. Ground support has been by rock bolts and wire mesh, followed by Fibercrete. A 16.5-kt/d underground molybdenum mine is being developed at Questa in northern New Mexico by Molycorp, Inc., a wholly-owned subsidiary of Union Oil Company of California. The new $200-million underground project will revitalize mining and milling activity at Questa, where small scale underground mining first began in 1920. Large scale open-pit mining was initiated in 1965 but now, because of the high stripping ratio, surface mining is being phased out. Construction of the underground mine began in 1979, and first production is scheduled for early 1983. The company expects full capacity - 9 Gg of molybdenum per year - to be reached in 1984.

Jan 1, 1980

By Ernest N. Wolff

You here are all familar with the myriad of new laws, some enacted and some pending, that affect the mining industry. These laws, for example those dealing with suspended matter, affect us in Alaska as they do you. Likewise, our friends in government, the Geological Survey and the Bureau of Mines, provide us with the same fine services that they do elsewhere. I am not going to speak today about these, but concentrate on one act of Washington, D.C. the impact of which is felt, for now at least, principally in Alaska. A little more than a year ago, I spoke in Spokane on the subject, "Governmental Challenge to Mineral Development in Alaska." I outlined some of the policies of Government which were operating to change the rules under which the industry operates and to alter the relation- ship between government, industry, and the individual. At that time the Native Claims Settlement Act had not been passed, but was on the verge of being so. In reading over what I said in Spokane, I note that I touched on many points where Government was actually challenging mineral development in Alaska. With the passage of the Alaska Native Claims Settlement Act, many of these actions were given a cloak of legality, and machinery was set up to concentrate the drive to tie up the public domain, machinery which will allow govern- mental control and interference with the actions of individuals on something like 90% of Alaska's land surface. This remarkable law is going to affect each and every one of you. Now, a year after its passage, we are only just beginning to see its lesson for the future. It was created by a coalition of powerful groups, who got other groups to support them by promising to deliver something they had no intention of delivering. Alaskan issues are again being used to get various groups not to oppose legislation which will severely harm them. It will help to understand the nature of this new drive if we understand the Native Claims Act and how it came into being.

Jan 1, 1973

By A. R. Laplante

A test to determine the amount of gravity recoverable gold (GRG) in an ore is described. Typical GRG results are given; an error analysis is detailed; possible uses are discussed. Of the 38 samples tested, the lowest GRG content was found to be 25% (most below 25 11m, or 600 mesh), and the highest 94% (most above 300 11m, or 50 mesh). The average GRG content was 63%, with a standard deviation of 19%. Error analysis shows the test to be reproducible within 5 to 10%, depending on the size distribution and grade of GRG, and the sample extraction protocol. When using the same primary sample, reproducibility improves, 2 to 5%, depending on the amount of gold coarser than 850 11m (20 mesh) and sample weight. The test has been applied to greenfield project and retrofit applications, to determine the suitability of gravity recovery. For existing circuits, it has been coupled with a model of gravity recovery for optimization studies.

Jan 1, 1996