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By S. Serata

Background Results of the above study in the August 1991 issue of Mining Engineering offer valuable lessons in the solution of cutter-roof problems. The original study plan was initiated by the discussion authors to solve the problems using the "stress control method" of mining (Serata 1976,1982; Serata, Carr and Martin, 1984; Serata and Gardner, 1986; Serata, Gardner and Preston, 1986; Serata, Gardner and Shrinivasan,1986; Serata and Kikuchi, 1986; Serata, Preston and Galagoda, 1987) However, the plan and the planner were changed to the arrangement reported in the paper. The change was considered reasonable at the time due to the mine engineers' uncertainties about the stress control method. Consequently, the basic principle of the study was shifted from the original stress control method to the method described in the paper, which will be called the "yield pillar method" for the purposes of this discussion. The paper convinces the reader that the yield pillar method fails to solve the cutter-roof problems. This doesn't mean that the stress control method also fails. Actually the contrary is true, as discussed below. Limitation of the yield pillar method The paper illustrates clearly how poorly the yield pillar method performs in solving the problem. The reason for this failure is the lack of the protective stress envelope needed to stabilize the cutter roof. Unfortunately, the protective envelope cannot be formed properly without utilizing the stress control method of mining. Changing the pillar size does not make much difference in the roof stability.

Jan 1, 1992

By Bryce Sullivan, Cliff Baratta, Ehsan Alavi, Timothy Dobbs, Lisa Mori

"Soil conditioning is one of the main factors in successful application of EPB machines in tunneling projects, which involves changing the characteristics of the ground in order to make it suitable for the tunneling process. Selection of the type of conditioner mainly depends on soil type, properties of the tunnel boring machine, and most importantly geological condition. Proper EPB tunneling and soil conditioning in ground above water table is challenging. This was encountered in Northgate Link Extension Tunneling Project in Seattle, WA. In order to improve the tunneling operation, a novel algae-based encapsulated oil was used as a conditioner and as a result the operation of the TBM was improved significantly. This paper reviews the traditional soil conditioning measures that were adopted in University Link and Northgate Link projects in Seattle, WA and compares the results with results when using the encapsulated oil additive. INTRODUCTION Soil conditioning agents are used in EPB tunneling to transform the excavated soil into a workable paste with the desired hydrological and mechanical properties. Reducing wear, power consumption, friction, adhesion, and improving the face stability and material flow are some of the benefits of using soil conditioners in EPB tunneling. Soil conditioning is performed by injecting foam, polymer, water, and bentonite to the tunnel face, excavation chamber and screw conveyor. Selection of conditioning agent mainly depends on soil type, geological condition (groundwater and soil permeability) and TBM features (injection points, open or closed cutterhead, type of foam generator, etc). The most widely used soil conditioners are foam and polymer and in some cases due to existing conditions, clay dispersion or anti-wear additives are also used (Milligan 2000, Langmaack 2000). Foam. Foam is created by dispersing air in a surfactant solution. A different combination of surfactant type and foam parameters should be used for different soil types. Laboratory tests on virgin soil should be performed to identify the best surfactant and foam parameters for the specific soil type (Langmaack 2000). The foam parameters can be described as follows:"

Jan 1, 2016

By S. K. Kawatra, A. K. Bakshi

Mineral suspensions in water show Newtonian flow properties at low percent solids. However, this changes to a non-Newtonian regime as the pet-cent solids increases. For Newtonian fluids, viscosity is independent of shear rate, hut, for non-Newtonian fluids, viscosity varies with shear rate. Therefore, if the slurry is non-Newtonian, attempting to measure the viscosity at a shear rate different from the shear rate experienced by the fluid within the process is futile. This is especially true for a hydrocyclone, where the rate of shear is different at different points within the hydrocyclone. In this case, it is very important to determine the flow type of the suspension before attempting to establish any correlation between the viscosity and the process efficiency. A new technique to distinguish such changes inflow type was developed. This involves two viscometers: a coaxial cylinder-type viscometer that measures apparent viscosity at low shear rates and a vibrating sphere-type viscometer that measures the apparent viscosity at high shear rates. For each of these instruments, special precautions were taken to allow, for the measurement of the viscosity of rapidly settling mineral suspensions. Because the vibrating sphere viscometer is operated at a much higher shear rate than the rotating viscometer, the two instruments together could determine the shear-rate dependency of the viscosity. Ground silica (80% passing 65 µm) in water was used to prepare slurries at concentrations ranging from 10% to 70% (by weight) solids. The viscosity of each slurry sample was measured simultaneously by both viscometers, and the results were compared. With this technique, it was found that all of the silica-slurry samples tested were in the Newtonian flow regime for up to 70% (by weight) solids. Methocel and Cellosize polymer solutions showed clear non-Newtonian behavior using this technique. This confirmed that non-Newtonian behavior of the silica slurries, if present, would have been detected by this arrangement.

Jan 1, 1997

By R. Tanaskovic

Unfavourable climatic conditions in stopes are of significant economic and social importance due to the following reasons: - Working effect is much lower leading to decreased output and work productivity disregarding implementation of mechanization. - Manpower operating capability decreases much faster under unsatisfactory climatic conditions. Under normal climatic conditions a workman would expend much less effort in line with a shorter effective time for the achievement of identical production effects since the work would be more efficacious. The objective of study of problems and climatic conditions is to make the working environment in mines suitable for normal development of operations. Lowering of mining works to increasing depths and winning of a growing number of small orebodies over a broad area makes the problem of creating suitable climatic circumstances more complex. Mining costs are growing due to bench conditions in line with decreasing metal content in the ore, so frequently the investments required for creating favourable climatic conditions represent, in addition to the selection of mining technology, a very important parameter when making decisions regarding exploitation. As known, the basic factors affecting climatic operating conditions in mines-are: temperature, humidity and speed of air flow, implying that the climatic operating conditions are closely related to mine ventilation. Usually, the concept of unfavourable climatic operating conditions includes increased mine air temperature and humidity and low air flow velocity so that heat exchange between human organism and the working environment is impeded or reduced to minimum. Metal mines in Yugoslavia are characterized by the existence of a large number of active faces - stopes and horizons and lowering of mining operations to increasing depths, so that face ventilation solutions are more and more complex. Since its foundation (1961), our Institute is engaged in investigation of factors influencing climatic circumstances improvement of calculations for air distribution and distribution control in complex ventilation networks and study of problems related to ventilation of large volume and irregular configuration faces, as well as application of gained knowledge in our mines. The paper presents the knowledge and experience gained in the case of Lead and Zinc Mine "Trepca" - Stari Trg.

Jan 1, 1980

By M. Gershon

The article is an excellent one, providing a basis for the conduct of the major tasks in underground mine planning and scheduling. I object to only one word. Since that word is featured in the title, it is a strong objection. The word used erroneously is optimization. There is no optimization performed in the article. By definition, an optimization is an approach that yields the best of all possible solutions. We can limit this definition to its narrowest sense, the optimization techniques of operations research such as linear programming, or broaden it to include less sophisticated search procedures that find the best mine plan or schedule. No such claim is made in the article. No optimization of any kind is performed. The major tool used is a simulation, which, in truth, is probably more appropriate for this problem than any optimization. But simulation does not optimize. It only allows for quick evaluation of many options, leading to the selection of the best plan "of those tried," not "of all possible plans." This article, of course, is not the first mining paper to make this error. It seems that the word optimization is used more to impress people than to refer to any act of optimizing. It is used in a way that implies "try to optimize" or "come close to optimize," but not to really do it. It is usually appropriate to quietly ignore this error. But when Dr. Chatterjee, who has done so much good work in true optimization projects and whose work I have come to admire, makes such an error, it is time to publicly dispute it. Having discussed this very point with him in the past, I am sure that he will agree. If he can support this position in his response, perhaps people will start to listen and we can reduce the number of false claims of optimization. This should be easy for him in this case since the approach he used, simulation, is the more appropriate one anyway.

Jan 1, 1987

By P. B. Queneau, J. E. Litz, T. P. McNulty

I. INTRODUCTION Modern hydrometallurgy has its roots in such notable successes as heap leaching for recovery of copper, cyanidation of gold ores, the Bayer process, the Oxland process for tungsten, electrorefining of copper, roast/ leach/electrowin process for zinc, and production of yellowcake from lowgrade uranium ores. Metallurgical testing techniques, sampling and analytical procedures, operating and maintenance practices, and improved methods and materials of construction which were pioneered in these processes have promoted the extension of hydrometallurgy into other applications. Periodically, new tools such as solvent extraction, resin ion exchange, and flocculants have opened new avenues to hydrometallurgists. Conversely, pursuit of more complex mineralization, the rising costs of energy and environmental quality preservation, and declining ore grades continue to create new challenges. For much of this century, it can be fairly said that practically any hydrometallurgical development moved the frontier of technology. The 1970's and 1980fs, however, have seen a significant maturing of hydrometallurgy's role in process metallurgy. Simplistically, this maturing seems to derive from a growing awareness of the strengths and weaknesses of hydrometallurgy and a determined effort to capitalize on the strengths. For example, many of us were among those revolutionaries of the 1960's and 1970's who taught that "chemical smelting" was the answer to the treatment of all sulfides. We now recognize, however, that only in very special cases can hydrometallurgy offer economic advantage over the generally less energy-intensive pyrometallurgical systems. The maturing of hydrometallurgy does not, however, signal stagnation. Important innovations are being studied and developed in most extractive areas, and a number are approaching or have achieved commercialization. From our company's perspective, that of an organization dealing with the development of the most economic solutions to metallurgical problems, innovation must be defined as the commercially successful reduction of an idea to practice. There appears to be no shortage of ideas, nor has there ever been a shortage. Many ideas now being implemented were conceived decades ago, but reduction to practice was foiled by the lack of such technology as responsive process control and economical materials of construction capable of withstanding highly corrosive or erosive environments. Commercialization of a new process is a particularly challenging undertaking. Even if technical risks are reduced to a minimum through careful and thoughtful process development, there are inevitable uncertainties in feed characteristics, variable costs, and product prices. Commercialization takes courage, both on the part of innovators who may be staking their careers or reputations and of investors who may face financial disaster in the event of project failure. This paper discusses innovative programs and recently commercialized processes which either have been discussed in the literature or disclosed to Hazen Research staff in private nonconfidential conversations with contacts in industry. Regarding this latter category of information, relative ease of communication has resulted in many of our observations being of North American origin.

Jan 1, 1985

By Alden B. Carpenter

Brines (a solution containing more than 100,000 mg/l dissolved solids) in sedimentary basins are genetically related to evaporites in one of three ways: (1) dissolution of evaporite minerals, generally halite; (2) interstitial fluids in evaporites which are expelled from their source rock during compaction; (3) incongruent alteration of hydrous evaporite minerals (carnallite). Most brines of commercial interest originate as interstitial fluids in halite-rich rocks. These fluids are initially rich in magnesium, sulfate, and potassium but evolve in composition to an Na-Ca-Cl brine during their migration to their present host rock. A particularly important reaction in this process is: 2CaCO3 + Mgt+ = CaMg(CO3)2 + Cat (1a) This reaction reduces the magnesium content of the brine and ultimately converts it to a calcium-rich brine. The loss of sulfate occurs by two mechanisms. One of these is by direct precipitation as calcium sulfate (either as gypsum or anhydrite): Ca 2+ + SO4 2- = CaSO4 (2a) Additional sulfate may be lost from the brine by sulfate reduction: S042 + 1.33CH2 + 214- = H2S + 1.33CO2 + 1.33H20 (3a) The loss of carbonate species occurs by precipitation as carbonates: H2O + C02 + Cat = CaCO3 + 2H+ (4a) The net result of reactions 3 and 4 is: Ca 2+ + SO4 2- + 1.33CH2 = H2S + CaCO3 + 0.33H2O + 0.33CO2 (5a) The loss of potassium from brines is caused by the formation of potassium aluminosilicates: 2K+ + Al2Si2O5 (OH)4 + 4SiO2 = 2H + 2KAlSi2O8 + H2O (6a) The hydrogen ions produced by this reaction dissolve carbonates: 2H+ + CaCO3 = Ca 2+ + CO2 + H2O (7a) The net result of reactions 6 and 7 is: 2K+ + CaCO3 + Al2Si205 OH)4 + 4SiO2 = Ca2 + 2KA1Si3O8 + H2O + C02 (8a) A study of brines from central Mississippi has shown that the composition of these brines is related to the interaction of pore fluids from evaporites with minerals in the enclosing sedimentary rocks.

Jan 1, 1978

By Christopher Bambridge

The Washington State Department of Transportation (WSDOT) is constructing a new tunneled route under Seattle to replace the existing State Route 99, Alaskan Way Viaduct (AWV), which follows the historic waterfront for several miles. The viaduct separates the businesses that rely upon the tourist trade from the down-town area. The reconnection of the city to the waterfront areas will occur following the completion of the SR99 Re-placement program that replaces the aging structure that was severely impacted by the 2001 Nisqually earthquake, with a state-of-the-art, twin-deck highway with a world record-breaking 17.4-m (57.3-ft) bored tunnel. Constructed in the 1950s, the double-tiered viaduct is nearly 3.2 km (2 miles) long and runs parallel to city?s waterfront. The viaduct, which is partially supported by the seawall, is a vital local and regional transportation link and carries about 110,000 vehicles each day. The seawall, built from concrete and timber in the 1930s, extends along Seattle?s waterfront and supports the soil behind it. Studies in the 1990s showed that the viaduct was nearing the end of its useful life, apparent by its exposed rebar and weakened columns. The 2001 Nisqually earth-quake further damaged the viaduct, forcing WSDOT to temporarily close it for inspection and limited repairs. The viaduct and nearby seawall are vulnerable to an-other earthquake and continue to show signs of age and deterioration. Following a collaborative process, WSDOT developed the following guiding principles to the viaduct replace-ment:

Sep 1, 2013

By R. N. Chakravorty, R. J. Kolada

Introduction Spontaneous combustion in coal mining is recognized as a major hazard in terms of safety and economics. A survey by Olaf (1979) revealed that 80% of coal mine fires were caused by spontaneous combustion. Modern mining methods demand a high capital investment. Closure of a working face may then result in a huge loss. Even a short production interruption can prove expensive. Spontaneous combustion may also produce lethal amounts of carbon monoxide, thus posing a serious threat to the health and safety of underground miners. The worldwide recession in the early 1980s resulted in a number of mine closures and production cutbacks. So large stockpiles at mine sites were common. Experience has shown that stockpile fires are difficult to extinguish. Critical factors influencing spontaneous combustion There is no simple method of predicting whether a particular mining method applied to a specific coal seam will result in spontaneous combustion. Under favorable conditions of heat accumulation, spontaneous combustion can occur with any type of coal. It is known that subbituminous coals are more susceptible compared to low volatility bituminous coals, and that a high ratio of exinite increases the risk. However, the inherent moisture content of the coal and the exposed surface area may be more significant. Actual mining and ventilation conditions also strongly influence susceptibility. In practice, the experience gained with the mining method applied to a particular type of coal seam must be carefully evaluated with respect to the factors responsible for spontaneous combustion. Feng, Chakravorty, and Cochrane (1973) summarized the critical factors influencing spontaneous combustion in coal mines (Table 1). Prevention methods and strategies Mine layout is the most important factor preventing spontaneous heating. Working districts should be designed so that a particular section can be isolated on short notice without affecting production in others. Sites for preparatory seals should be identified and marked during planning. With coal seams that are highly susceptible to spontaneous combustion, the retreat method of working is preferred. This is because the gob is not subjected to a large difference in ventilation pressure. Coal pillars should be designed to resist excessive crush. The panel system of working is preferred, particularly for mining coals susceptible to spontaneous combustion. The size of each panel is calculated based on the incubation period and the rate of extraction. Controlling air leakage is also important for controlling spontaneous combustion. This is usually achieved by minimizing ventilation pressure difference, proper siting of doors, and avoiding unnecessary stopping and starting of fans. Air leakage is also reduced by sealant coating, injection of cements in cracks and crevices, and by maintaining good gateside packs. Application of inhibitors to control spontaneous combustion met with limited success. Chamberlain and Hall (1973) concluded that borate solution or Montan powder sprayed in the gob area or infused into a low rank coal would reduce the possibility of spontaneous combustion. Early detection of heating Significant research is being conducted worldwide to develop methods for early detection of heating. Monitoring combustion products during the early stage of heating is the most suitable method for detecting spontaneous combustion. The major gaseous products resulting from low temperature oxidation of coal are carbon dioxide, carbon monoxide, and water vapor. In mining operations, carbon dioxide monitoring is considered unsuitable because there are sources other than spontaneous heating from which this gas may originate. Carbon monoxide, however, is a more specific product of combustion during low temperature oxidation of coal. Over the years,

Jan 10, 1988

By Nellie E. Guernsey, Louis J. Sousa, Alfred Weiss, Nickolas J. Themelis

Over the past decade, numerous factors have led US copper firms to face increasingly severe competition from low cost foreign producers. As a result, greater attention is being devoted to developing and implementing new technology that can reduce costs and maintain the competitive position of domestic firms while simultaneously meeting environmental requirements. To obtain a better understanding of the likelihood of the development, adoption, and use of innovative copper technologies in the future, the Bureau of Mines contracted with Mineral Systems Inc. of Stamford, CT, to undertake a systematic survey of technological experts in industry, government, and the academic community. According to the survey, major developments in exploration over the next 25 years are likely to be in technologies that facilitate analysis and interpretation of deposit data rather than those that enable the collection of additional data. Most new copper mining and beneficiation technologies are likely to represent evolutionary extensions of existing systems with a notable increase expected in the application of information systems technologies and computer control methods. A possible movement towards increased usage of continuous mining systems in copper was also noted. Experts indicated that several copper smelters are under consideration for extensive renovation and, as a result, flash smelting technology is expected to become much more widely used in the US. A gradual movement toward continuous smelting methods was also forecast. In copper refining, the major technological change expected is the gradual automation of various refinery operations. Finally, though increased usage is expected, in situ solution mining and hydrometallurgical processing of sulfide ores are not expected to become widespread over the forecast time horizon. This first article in a two-part series describes the survey method chosen and the technological innovations selected for eval¬uation. Also discussed are the assessment panels, background scenarios, critical events, and diffusion forecasts. Next month, part two will address technology forecasts resulting from the study. Featured are discussions on future copper exploration, mining, beneficiation, smelting, refining, and recycling. A cost/benefit analysis will also be included. Methodology Selection of Assessment Method To develop a consensus forecast of technological change in the copper industry, a technique for systematically polling subjective opinions of experts was required. After conducting a literature survey and some preliminary testing, the direct probability assessment method was selected. With this assessment method experts are asked to express in quantitative terms their judgment of the probability that a specified event will occur, usually over a series of time frames. The method was chosen because the experts were observed to be more comfortable with this approach during the testing period, and the results of this process effectively satisfied the assessment objective. The experts generally could provide more precise estimates of the timing of future events using this technique because it was the least cumbersome of the assessment methods tested. Identification, Selection, and Description of the Technologies The initial list (Table 1) of innovative copper technologies assessed in the study was developed from two principal sources: knowledge and expertise of the study team and a review of relevant technical literature. From this list of 47 potential technologies, 10 were selected for detailed assessment. Table 2 lists 35 technologies that were subsequently identified in the first series of assessments. Twelve technologies from this list were also selected for detailed evaluation in a second assessment round. Criteria used for the final selection of technologies for detailed assessment specified that: • The expected impact of each technology on copper supply (i.e.,

Jan 9, 1983

By Aldo Bellone, Francesca Rossano, Massimiliano Bringiotti

"In 2004 works started for the now completed seven-level automated car park accommodating 480 parking spaces inside the pre-existent “Morelli cave”, located in a strategic area in Naples. Since 470 BC Greeks initiated the growth of the fascinating world of the underground Naples, of which this cave belongs. It seems that once here the god Mithras was worshiped. It’s also became a quarry for tuff extraction and in 1600s it became an aqueduct serving the area. In 1853 the Bourbon Tunnel, a project commissioned by King Ferdinand II of Bourbon to allow easy escape from the Royal Palace in case of riots, was connected to this network of tunnels. The cavern became an air raid shelter during the Second World War, then a deposit of cars and motorcycles in the '50s and' 60s, a disposal area and it has been abandoned in the last 40 years before it’s new utilization. INTRODUCTION Over time, the overcrowding and congestion of major cities’ historic centres has led to seeking spaces underground that can accommodate activities and car parks, as in the case of the Morelli cavity, site of the future car park by that name. Before describing its characteristics, design solutions, and executive problems, it is necessary to introduce the site historically into the broader landscape of the cavities present below ground in the municipality of Naples. The province of Naples, which includes the area of the Municipality of Naples, has a large number of cavities. The existence of “Naples underground” is connected with the morphological and geological conformation of its territory, consisting of tuff stone which has entirely special features of lightness, brittleness, and stability. The first transformations in the territory’s morphology, taking place thanks to the Greeks starting from 470 BC, initiated the growth of the fascinating world of Naples underground. These transformations were dictated by water provision requirements, which led to the creation of underground cisterns to collect rainwater, and by the need to recover construction material to erect the buildings of Neapolis. In subsequent centuries, the city’s expansion led to the construction of a proper aqueduct, which allowed drinking water to be collected and distributed thanks to a series of cisterns linked to a dense network of tunnels. During Roman rule, the existing aqueduct was expanded and perfected, but with the rise of the Angevins in 1266, the city saw great urban expansion, which obviously corresponded with increased extraction of tuff from the subsoil to construct new buildings. This confirmed a particular feature of Naples: that of having been generated from its own innards, with buildings rising directly above the quarry that provided their building material."

Jan 1, 2016

By D. Buranek, J. G. Wulff, F. W. Gifford

I. INTRODUCTION During the past few years, the state of the art of disposal of solid and liquid waste products from uranium mining and milling operations has experienced some rather interesting and significant changes. Some of these changes have resulted from technological advances in the milling operations and in the engineering aspects of the actual design and construction of the disposal facilities. However, the most significant changes, at least those which have had the greatest impact on the comparative cost and economics of modern disposal systems, have been environmental requirements and regulatory controls, which have become increasingly stringent in recent years. Without delving into the details of the myriad of new laws and regulations which now control the uranium industry, it can be stated with reasonable confidence that one of the principal purposes of more rigid state and federal controls over this industry is the basic desire to promote safer, more reliable and longer term means of effectively controlling and disposing of the potentially objectionable waste products resulting from uranium mining and milling operations. It is difficult to take issue with these basic goals because their need was spawned by past lack of awareness and inattention on the parts of both government and industry to the long term environmental problems and potentially hazardous conditions which can be created by limited planning and ill-conceived or poorly controlled and executed disposal practices. On the other hand, despite the good intentions of those who developed and those who are administering the regulatory controls now in effect, the basic danger exists that overgeneralization of the approach to disposal problems and overrestriction of the potentially acceptable solutions for uranium mine and mill waste disposal could have a significant, adverse economic impact on the mining industry and the ultimate consumers of their products. The regulatory pendulum, which perhaps swung too far toward lack of controls over uranium mill waste disposal in the 1940's, could now well be headed too far in the opposite direction, that is toward over-regulation in the form of restrictions based on technically unrealistic or weakly supportable

Jan 1, 1980

By Erik Westman, Enji Sun, Xu Ma, Ben Fahrman

"Shale gas has become an increasingly important clean energy, which has been explored worldwide in recent decades. Supercritical CO2 acts as fracturing fluid for shale gas production. The safety monitoring is essential to prevent any kinds of leakage from the reservoir as the supercritical CO2 physically stored hundred kilometres underground. Seismic tomography is an imaging technique that uses induced seismic waves to create three dimensional images of the subsurface. It is an effective monitoring method to evaluate the caprock integrity in the carbon dioxide sequestration storage (CCS). In this experimental research, a simulated uniaxial compressive load is applied on a granite sample to analyze the stress redistribution for long-term in-situ caprock integrity during CO2 injection. The induced seismic waves are recorded and seismic events are traced based on the Geiger algorithm. The frequency of seismic events correlates with the caprock failure evolution. The acquired seismic data is divided into four regimes based on the frequency of seismic events and the failure process to examine the failure evolution. Furthermore, the travel time and distance is plotted to analyze the variation of velocity. Finally, the double difference tomography (TomoDD) algorithm using arrival time is adopted to recalculate the locations of seismic events and velocity structure in each regime. The results indicate that the passive seismic system can map the caprock stress distribution and allow for imaging of the caprock integrity. TomoDD exhibits sound improvements to relocate seismic events both in relative and absolute locations as well as to characterize the local velocity structure. The study further reveals that seismic monitoring along with TomoDD could evaluate the caprock failure accurately in the CCS.Introduction To reduce the CO2 concentration in the atmosphere, CO2 capture and sequestration (CCS) has been suggested to as a means of continuing to use fossil fuel resources while offsetting their negative environmental impacts (Eiken et al 2011). A positive CCS project should retain 99% of the injected supercritical CO2 (pressure is greater than 7.38 MPa and temperature is above 31.04? and a density is of about 700 kg/m3) over at least 100 years (Davidson et al 2005). As large quantities of supercritical carbon dioxide are being injected into full scale storage projects, caprock stress is redistributing and the leakage could occur anywhere over a wide storage area (Hou et al 2012). Acoustic waves are emitted from the caprock, as it fractures due to the CO2 injection, which can be detected by passive seismic sensors (Shitashima et al 2013). Tomography techniques are advantageous for imaging the integrity of the caprock in the CCS projects. Velocity tomography uses waves to model entities based on the arrival time of waves (Westman et al 2001, Westman 2004, Luxbacher et al 2008). Seismic tomography is a data inference technique that exploits information contained in seismic records to constrain 2D or 3D models of the Earth's interior. It generally requires the solution of a large inverse problem to obtain a heterogeneous seismic model that is consistent with field observations (Kudryavtsev et al 2012)."

Jan 1, 2017

By Deepak Malhotra, Linda Battich

INTRODUCTION Mineral processing plants generally operate efficiently within the technical, economic and management constraints applied to them. They have no choice, because the dynamic and competitive nature of the mineral business dictates that survival and/or prosperity of the company depends on being a low cost producer. Progressive mineral companies realize that market downturns will occur, and they must continuously strive for lower unit production costs rather than be satisfied with the status quo. Mineral companies generally tend to reduce costs during market downturns. This short-term solution is achieved by high grading of ores, and cut-backs In waste stripping, exploration, and capital expenditures.(1) However, to remain a low-cost producer in the long term, companies must enhance revenue and reduce cost simultaneously. This Involves continuous evaluation of technologies and reagents, periodic audits to locate revenue losses; and gathering and analyzing statistical plant data to clearly understand the Impact of process variables on efficiency. Mineral companies are caught in a Catch-22. They need resources to accomplish the objectives outlined above. Most mill stuffs have been cut to the minimum level necessary to maintain production. Resources such as time, manpower and money are scarce, and mill metallurglsts struggle to use these resources productively. Is your flotation plant optimized? History Indicates that successful operations constantly tune the flotation circuits to Improve metallurgy or reduce cost. This Is the essence of evolutionary change In mineral processing operations. A plant auditing approach can play a key role in assisting the process engineers to achieve the overall objective of enhancing metallurgy and reducing cost with limited resources through evolutionary improvements. FLOTATION SYSTEM The flotation process is the most widely wed concentration process In the world today. The number of variables that can affect the flotation results Is very large, maybe over 100. These variables can be divided Into three main groups: (2) (1) ore and mineral properties; (2) reagent treatment; and (3) flotation machine characteristics. Some of these variables can be controlled while others have to be accepted. Recently, Investigators (3,4) have attempted to describe the flotation process as an engineering system which includes chemistry, equipment and operating variables. Though some of the variables are Independent, most are co-dependent. thus making it difficult to develop simple cause and effect relationships. For example, it is easy to understand the effect of reagent change on recovery and grade In the rougher circuit, but very difficult to quantify Its impact on filtration downstream. Plant audits on a periodic basis are necessary to develop an understanding of the Interactive nature of the system. Auditing provides comparisons of plant operating performance before and after variable changes. OVERVIEW OF PLANT AUDITING An audit Is a formal, thorough and periodic examination of a system. There are various types of audits (i.e., geological, environmental, metallurgical. economic, etc.), and each serves a different purpose. (5) The discussion here is related to plant and/or metallurgical audits. Neale and Flintoff note that two key factors governing changes In an operation are: (1) the opportunity must be recognized; and (2) the justification for change must exist. (6) Both factors emphasize the critical role of successful plant auditing. Without plant audits. many opportunities for improvement must go unrecognized. On the other hand, when a situation ripe for improvement Is recognized. the hard data from a plant audit can reveal the expected impact of an operating change.

Jan 1, 1993

By John R. Alderman

INTRODUCTION Uranium production in Saskatchewan commenced in 1953 at the Eldorado Nuclear Mine in the Beaverlodge area of North Saskatchewan, followed over the next few years by nineteen other smaller mining operations. Production rose from 453 600 to 2 721 600 kg per annum by 1958. Over supply and the closure of the U.S. market to Canadian uranium led to an equally rapid decline to an annual production which varied from 453 600 to 907 200 kg during the years 1964 to 1976. As the market strengthened there was a resurgence of the Saskatchewan industry and production from one underground and two open pit mines reached 2 809 000 kg in 1980 for a return of 232 000 000 dollars (Table 1). [ ] Future output will be increased by a potential 4 536 000 kg from the Key Lake mine now under construction and scheduled to commence production in 1983. Three other projects are in an advanced stage of planning and are currently in the regulatory review process. Several other prospects are being evaluated. Figure 1 shows the location of uranium mines in Saskatchewan and table 2 illustrates the present status of uranium mines and deposits in Saskatchewan. At present, 1400 workers are employed directly by the uranium mining industry. Saskatchewan has diverse mining conditions ranging from the underground mine of Eldorado Nuclear Limited 1870 m deep with a low grade ore deposit averaging from 0.17-0.20% with extraction by carbonate leaching through an open pit operated by Gulf Minerals with a moderate depth of 110 m and 0.37-0.5% grade to the shallow open pit of Cluff Mining 30 m deep with a very high average ore grade of 7.0%. Extraction at both open pits utilizes acid leach extraction processes, the latter after gravimetric separation. Key Lake mining has commenced development of the next mine to come into production which will have two open pits to a depth of 80 and 175 m with an average 3% grade to be followed by the deep open pit of Canada Wide Mines Ltd. to a depth of 205 m with average grade of 1.5%. One existing mine will transfer its operation from the present open pit to another of slightly higher average grade. From the Saskatchewan point of view, these different operating conditions present varied problems associated with occupational health and safety and concomitant solutions to reducing worker exposure to radiation. REGULATION OF URANIUM MINES In 1946, the Government of Canada enacted the Atomic Energy Control Act which established the Atomic Energy Control Board (AECB) and vested in that board powers to regulate all aspects of uranium mining. In the early years, the AECB relied heavily on provincial occupational health and safety agencies for the surveillance of uranium mining and milling operations, particularly with regard to "conventional" occupational health and safety, the AECB having at the time no specific regulations covering the mining industry. There has been considerable dialogue between federal and provincial governments since, traditionally, occupational health and safety is a provincial jurisdiction. Saskatchewan is strongly opposed to the intrusion of the federal government into the provincial domain, particularly as there is little justification for a federal presence in occupational health and safety in uranium mining and milling. The province does, however, accept the need for federal involvement in certain aspects of the regulation of nuclear industry, for example, international sales, research and security of reserves for domestic use.

Jan 1, 1981

By Slawomir Bock

One of the fundamental issues having a great influence on the safety of operations performed in underground mines is the support of workings which should assure their stability in a given geological setting and mining-technical conditions during the life of their use. The process of designing and planning support for roadways may use analytical and empirical, as well as numerical methods. In view of the rapid increase in the data processing capacity of computers and the development of more and more enhanced software for numerical modeling, it seems to be advantageous to use numerical methods in searching for design solutions ? especially in the case of non-typical mining and geological conditions and in cases that need to take into consideration a great number of factors. The assessment of rock mass quality is of basic significance in designing mine supports. Fractures, dividing the rock mass into blocks, have an essential influence on the stability of the rock mass and underground construction. This paper presents examples of the fundamental underground investigations on the rock mass conducted by the Department of Extraction Technologies and Mining Supports of the Central Mining Institute in Poland, such as: penetrometric tests, introscopic examination, laboratory testing of rock samples and ground penetrating radar. Moreover, this contribution also presents examples of applications of three-dimensional numerical modeling for the purposes of stress-strain analysis of the rock mass around mine workings and computer-aided support design by means of FLAC3D (developed by Itasca) and Cosmos/M (developed by Structural Research and Analysis Corporation).

Jan 1, 2009

By E. Sabina Brady

Over the next two decades there will be significant trade and development opportunities in China for mining, engineering, equipment, and construction companies interested in becoming part of the development of China's chemical and fertilizer industries. At last count, China's phosphate ore reserves of 11.8 Gt (13 billion st), ranked fourth in the world behind the US, the USSR, and Sahara-Morocco. However, a recent statement by the head of the Ministry of Geology and Minerals, Sun Daguang, claims that with increased prospecting in the last few years, China's phosphate reserves now rank first in the world. Whatever the actual size of its known and potential reserves, China's present phosphate processing capabilities fall far short of demand, while the substantial progress that has been made in this area points out the severity of the problems that still remain. Since 1949 China has developed 181 mines and increased its phosphate concentrate production from 10 kt (11,000 st) to 10.86 Mt (11.97 million st). By the 1980s, China was the third largest chemical fertilizer producer in the world-although this claim is slightly misleading as China's nitrogen/phosphate potassium ratios are far from average world ratios and even further from US standards. According to the Sixth Five Year Plan promulgated in 1982, the country's development plans emphasize the expansion and upgrading of key energy and industrial sectors, including that of fertilizer production-specifically phosphate and potash. Within the framework of the plan, the Ministry of Chemical Industry's development priorities are to: • Increase potash production by 150% to 50 kt (55,115 st). • Raise phosphate fertilizer production 21.2% to 2.8 Mt (3.1 million st), 46 kt (50,705 st) of which will come from new projects constructed and completed within the Sixth Five Year Plan, with projected new production of phosphate concentrate and complex fertilizer in the next decades totaling 500 kt (551,146 st). • Commence work to increase phosphate ore production by 8.33 Mt (9.18 million st). Facilities for 2.43 Mt (2.68 million st) will be completed and come on stream by 1985. • Commence work to increase iron pyrite ore production by 3.69 Mt (4.07 million st), facilities for 2.9 Mt (3.2 million st) will be completed and come on stream by 1985. • Verify 600 Mt (661 million st) of new phosphate ore reserves. Since the promulgation of the Sixth Five Year Plan, Chinese authorities have announced that 70 key construction projects will receive top priority in the implementation of the plan. These projects include five in the chemical industry area, including the construction of four fertilizer plants in Urumqi (Xinjiang), Zhenhai (Zhejiang), Beijing, and Lucheng (Shanxi), and a pyrite mine in Yunfu (Guangdong). In addition, by 1985 the state will expand or construct three major phosphate mines: Wangji in Hubei, Kaiyang in Guizhou, and Kunyang in Yunnan. Fertilizer Ratios In 1982, China's fertilizer production was slightly higher than 12 Mt (13.2 million st) and consisted of 80% nitrogen, 19% phosphate, and 0.19% potassium. By 1985, state officials project that fertilizer production will reach 13.4 Mt (14.8 million st) and consist of 78.4% nitrogen (10.5 Mt or 11.6 million st), 21.2% phosphate (2.8 Mt or 3 million st), and 0.39% potassium (52.3 kt or 57,605 st). To attain the world average using the country's 1985 projected production level for nitrogen, China will have to double its 1985 phosphate production to 5.76 Mt (6.35 million st) and increase its 1985 potassium production almost 80 times to 4.1 Mt (4.5 million st). These numbers demonstrate the seriousness of the fertilizer production problem in China today and the long-term nature of the problem's solution. Development Examples Yunnan is the third largest phosphate-rich province in China with verified deposits of 1.9 Gt (2.1 billion st). Despite this abundance, the province only mines around 3 Mt (3.3 million st) of phosphate rock annually. In June of this year, Yunnan announced its intention to initiate 39 development projects within the next two and a half years, requiring an estimated $200 million worth of foreign investment. The three areas receiving the most emphasis will be:

Jan 9, 1983

By Ernest Y. Baafi

The technique of linear kriging as a grade estimation method of mining blocks is reasonably established in the mining industry. Because of the nonbias condition imposed in kriging which requires that the kriging weights (?i) add up to one, negative weights are sometimes used in kriging. The use of negative weights is not justifiable from the practical standpoint. Also, negative block grades can be obtained in some extreme situations which makes no practical sense. To guarantee non-negative weights an additional constraint is required in the kriging system of equations. Unfortunately, the nonnegative weight constraint results in a set of non- linear system of equations. In this paper, a derivation of the resulting set of nonlinear equations is presented and a numerical algorithm is developed for the solution of the equations. Because the algorithm developed does not remove negative weights arbitrarily, optimal nonnegative weights are always guaranteed. Results obtained using the developed algorithm were compared with those using the standard linear kriging, in terms of computer time and the estimation results. Both the computer time and the kriging variance were found to be higher with nonnegative constraint, as expected. However, some systematic pattern was observed in the kriged values (i.e., over or under estimation) with or without the nonnegative constraint. The study also demonstrated when one should generally expect negative kriging weights in practice, and what practical impact the negative weights can have on the kriging estimates.

Jan 1, 1984

By David B. Cook, James R. Bieke

I. INTRODUCTION Lawyers are a cautious breed; and it might be expected that a paper concerning a broad and complex area of legal regulation, prepared by lawyers for presentation to a predominantly non-legal audience, would commence with several caveats. Ours are the following: First, we have written a broad (and, in some instances, simplified) overview of the regulatory system and of some of the more important requirements generally applicable to uranium mine and mill wastes in the United States. Our paper is not a legal opinion setting forth all of the governmental requirements that would have to be met by any particular mine or mill. Similarly, we do not imply that the requirements we mention are necessarily applicable to each and every mine and mill in the country; depending on the facts, some of the requirements may be inapplicable or avoidable through exemption or variance proceedings. Compliance decisions and strategies for particular facilities must be considered on a site-specific basis. Second, we have undertaken merely to describe the regulatory framework and some of the generally "applicable" requirements which have been promulgated and proposed by administrative agencies. We express no opinion on whether, under the U.S. Constitution and statutes, the existing and proposed agency regulations are valid in general or as applied to any particular mining or milling operation. There are, of course, procedures for judicial review of agency action; and newly promulgated environmental regulations have frequently been challenged, with varying degrees of success, before the courts. For us even to begin to consider such issues would expand an already forbiddingly long paper to totally unmanageable proportions. Third, in light of the subject of this Conference we have limited our paper to the legal framework and requirements applicable to uranium mine and mill "wastes" -- primarily mine overburden and waste rock and mill tailings (including waste tailings solution). We treat operating discharges (e.g., emissions from yellowcake drying) only peripherally. Fourth and finally, it is important to note that this paper, at least in so far as it concerns the specific requirements of particular regulations, will likely soon be out of date in some important respects. Despite

Jan 1, 1980

By Klaus Rieker

Over the last 30 years Wayss & Freytag Ingenieurbau AG has gained a lot of experience in mechanized tunnelling on various major projects. During this period most important developments concerning the machine technology for EPB- and Slurry-Shields have taken place. Since the first application of a hydro shield for the Wilhelmsburg Collector project in Hamburg in the early seventies, several stages of development have led to the current state-of-the-art in mechanized tunnelling. The continuous improvement of TBM techniques allows the execution of high quality tunnelling, particularly with regard to maximum safety and efficiency. The practical experience of the construction companies is of essential importance in order to continue further development and improvement.

Jan 1, 2005