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By Mukhopadhaya K. K, Cory A. H

The concept of using travelling magnetic fields created by linear motors was stimulated by Laithwaite who advanced ideas on motors with shaded poles (Laithwaite, 1968), rack and pinion motors (Laithwaite, 1970) as well as low speed, brushless motors and three dimensional motors (Laithwaite, 1973a and 1973b).Sudan (1963) and Sundberg (1969) had applied the concept to metallurgical processes. However, the use of travelling magnetic fields has not been used widely to produce conditions for the separation of magnetic from non-magnetic minera1s or even magnetic materials from non-magnetic materials, although some attempts were made by McCarthy (1922), Davis (1934), Dean, Gottschalk and Davis (1934) and Gottschalk (1934).Laithwaite (1973, a) while working with linear motors made suggestions for designing separators and in the work described here, the observations of Laithwaite and others are extended to determine the characteristics of the motor with a view to using it as a magnetic separator.

Jan 1, 1980

By Richard F. Zaffarano

The Bureau of Mines compiled information for the nonspecialist about natural gas liquids recovery from hydrocarbon streams in natural gas processing plants. Attention is directed to the impact of the technology of processing and the quality of gas processed in view of the increased availability of natural gas for processing. Significant changes in product and market trends within the natural gas processing industry are highlighted. Fixed capital-plant costs for grassroots, refrigerated-oil absorption and conventional adsorption schemes, adapted from published studies, are presented giving ranges of cost estimates for medium-sized plants. Marketed products of the natural gas processing industry are briefly discussed in relation to automotive air pollution problems and approaches to their control.

Jan 1, 1970

Environmental information is an essential part of successful mine design and approval. In order to be most effective in its application and availability, this information needs to be collected in programmes with defined objectives and deadlines. Applied Geology Associates have established a methodology to facilitate the structured collection of environmental data, which provides for the diverse needs of both engineering design and applications for statutory and non-statutory approvals. Principal aspects of this methodology are the scope, timing and management of the environmental studies within the overall project planning framework.

Jan 1, 1987

By G. A. Mallory

"The South Bay Division of Selco Mining is located fifty-four miles northeast of Ear Falls Ontario on Confederation Lake. The concentrator operates five days a week and processes six hundred tons per day of copper zinc silver sulphide ore. The concentrator is comprised of crushing, grinding, differential flotation, thickening and drying circuits. The major constituents of the concentrator feed are: chalcopyrite 7%, sphalerite 20%, pyrrhotite 3%, pyrite 25 - 30% and felsitic volcanics 40 - 50%. The mine went into production in March 1971 with an anticipated three year life and is now scheduled for closure in the summer of 1981. Recent mine production has been limited to three cut and fill stopes which have widely varying ore grades, therefore mill feeds vary from 0.25 to 4% copper, 3.5 to 27% zinc, 0 to 0.4% lead and 15 to 30% iron.In mid 1977 Selco negotiated a six month rental purchase agreement with Outokumpu Instruments Canada Limited for a five stream analyser system. The Minexan 202 probes were the first Outokumpu probe type analysers installed in Canada although Outokumpus' Courier systems are well known. Installation of the system took place in April 1978 and after numerous hardware faults the six month evaluation began in August. By December it was obvious that the Minexan 202 probes with proportional detectors did not have adequate resolution to determine low copper values in either of the tailings streams. Outokumpu offered to replace the tailings analysers with a new prototype solid state detector probe the following summer. The evaluation on the five Minexan 202 probes continued until August 1979 when the new solid probe was installed. The Minexan S (solid state) probe was evaluated with the three remaining Minexan 202 probes until December 1979 when Selco elected to purchase the system."

Jan 1, 1981

By Sergio Cattalani, David J. Kerr, Harold L. Gibson

Abstract - The Horne mine was truly a world class Cu and Au deposit. Between 1927 and 1989, it produced some 260 t of Au and 1.13 Mt of Cu from 53.7 Mt of ore that averaged 2.22% Cu, 6.1 g/t Au and 13 g/t Ag. The total value of Au and Cu production from the Horne deposit at metal prices of US$300/oz Au and US$1.00/lb Cu is an outstanding US$5.2 billion. The Horne mine was also a company builder. After optioning the property from Ed Horne (Tremoy Syndicate) in 1922, the Thomson-Chadbourne Syndicate discovered the deposit in 1923 and quickly grew to become Noranda, one of the world’s premier mining companies. This discovery fuelled exploration and, along with subsequent discoveries in the Val d’Or-Cadillac camps, led to the "economic development" of northwestern Quebec. The Horne deposit influenced and continues to influence genetic models for volcanogenic massive sulfide (VMS) deposits. Early observations at Horne contributed to an epigenetic replacement theory for VMS deposits. The most recent genetic model for the Horne, invoking sub-seafloor sulfide replacement of silicified and sericitized volcaniclastic host rocks within a graben, has subsequently been proposed for another giant VMS deposit, the Kidd Creek mine. The Horne and Kidd Creek deposits show many similarities, such as localization within synvolcanic grabens, long-lived hydrothermal activity uninterrupted by volcanism, sub-seafloor replacement sulfides, stacked sulfide lenses, zone refining, silicified footwall rocks characterized by high positive ?18O values, and association with FIII rhyolites. Notable differences between the two deposits include the lack of andesitic, basaltic or komatiitic flows at Horne, different inferred water depths, high Au content at Horne versus negligible Au, but sub-economic to economic concentrations of Sn, In and Cd at Kidd Creek.

Jan 1, 2000

By J. J. Stacey

Large mining companies generally follow the distributed ownership corporate model, with a board of directors responsible for decisions that affect both shareholder value and stakeholders of the company. The board is simultaneously responsible for setting the culture and values of the corporation, which drive performance and priorities. Companies listed on the Johannesburg Securities Exchange (JSE) commit to sustainable development in various ways, either by virtue of implementing the King Code of Governance 2009 (King III) and/or through their own public reporting on social and environmental matters. Many mining companies make public statements regarding their support for environmental stewardship, ethical behaviour, and fair treatment of communities. It is a local, regional, and indeed, global phenomenon that companies fail to deliver on these statements. Research was carried out through the Institute of Directors of Southern Africa in 2007, and followed up in 2012, regarding directors? understanding of sustainable development issues, the relative priorities, what is needed for ?radical change? to effect sustainable development, and what enables or constrains the latter. Pertinent findings of both surveys are presented in this paper, and it is suggested that ?on-the-ground? performance may be indicative of the nature of leadership and decisions in the topmost ranks of the company. The results indicated that environmental concerns fall consistently below social issues. Financial capital ranked most important, and while environmental issues are recognized as being of strategic concern for the long-term, they ranked as being the lowest importance of all ?Five Capitals? (Financial, Manufactured, Social, Human, and Natural). Social capital ranked second lowest, with black economic empowerment being the only high-priority social issue. There is also evidence that certain companies within the mining sector fail to recognize their absolute dependence on natural resources. Much is made in academic and popular literature of the need for a new type of leadership for the radical shift to sustainable development: at company level this implies therefore a new type of director. The research found that only 14 per cent of directors felt that board decisions are consistent with their personal values; while intentions are strong to behave ethically and serve sustainable development, actions to give effect to these intentions lag significantly. Respondents indicated that the top impediments to courageous leadership for sustainable development related to personal issues of maintaining the image of being a director, fear of appearing weak, fear of being a lone voice, and bowing to board-colleague peer pressure.

Jan 1, 2014

By Donald Leroux, Dave Scott, Giovanni Di Prisco

"The Lady Loretta lead-zinc deposit in Northwest Queensland, Australia contains an average of 5.9% lead, 17.1% zinc and 97 g/t silver. Ore mineralization is mostly comprised of fairly complex intergrowths of pyrite, sphalerite and galena. Starting in 1998, Noranda Inc., the major joint venture partner of the project, conducted extensive metallurgical test work, which culminated in July - August 2000 in a series of Pilot Plant tests. A common thread to all the metallurgical work has been the deportment of a large portion of silver into non-payable metallurgical products. Average silver distribution from four Pilot Plants shows a distribution of silver in lead concentrate of 28%, whereas silver in zinc concentrate was 49%, and 23% in the final tails.The consistently poor silver recovery as well as the fairly unusual silver distribution, particularly in zinc concentrate, was considered an issue to be thoroughly investigated. A mineralogical plan was devised to determine if these particular metallurgical results were somewhat related to the nature and mode of occurrence of silver carriers. Work was performed to determine discrete silver-bearing minerals and/or silver contained in solid solution in a suite of commonly occurring sulphides. Ore microscopy, SEM methods, Electron Microprobe and Ion Microprobe analyses were all used to answer these questions, and to find the silver carriers, so a metallurgical plan could be devised to improve silver recovery.INTRODUCTIONPotential economic exploitation of the Lady Loretta deposit in Queensland, Australia is driven by revenue derived from zinc and lead flotation concentrates and co-product silver recovery in lead. Relatively low recoveries of payable silver to lead concentrate, and high silver distribution to zinc concentrate necessitated an investigation into the natu"

Jan 1, 2002

By Harry R. Price, Bharat Doshi, Awni Qaqish, Abdul-Ghani Mekkaoui, Thaddeus Znoy, Ramesh Shukla

In 1992, a detailed inspection of the Southfield Sewer revealed a reach of approximately 0.8 kilometers in length, located directly below the freeway lanes, which was severely distressed. Failure of this section of the sewer would result in the closing of the busiest roadway in the state as well as the potential backup of sewage into homes and spilling into nearby surface waters. As such, repair of the distressed section required development of a procedure that would not jeopardize the conveyance of flow through the existing sewer nor impede travel on the overlying freeway. Based on these constraints, the DWSD and NTH team developed a repair concept that entailed the mining of a new, 3.05-meter (10-foot) diameter bypass away from the traffic lanes. The new bypass section was connected to the existing sewer, up stream and down stream of the distressed area, using a “top down” construction approach, that required only minimal freeway closures during weekend periods. This paper, prepared jointly by the Owner, Consultant and Contractor will describe existing conditions, design considerations and construction methods.

Jan 1, 2001

By Wesley Schmutzler

The Deep Mixing Method (DMM) was employed to raise and support the LPV (Lake Pontchartrain and Vicinity) -111 Levee in New Orleans. Even using innovative technologies, the tight schedule to achieve the 100 year elevation by June 1, 2011 was a daunting endeavor. The size and scope of DMM proposed for LPV-111 was on a scale never attempted outside of Japan. Over 1.65 million cubic yards of DMM was installed. LPV-111 is adjacent to the Bayou Sauvage Wildlife Refuge, which is the largest urban National Wildlife refuge in the United States. By utilizing DMM to control settlement and improve stability of the taller levee, side slopes were steepened from the conventional 1V:4H to 1V:2.85H, thus avoiding encroachment into the Bayou Sauvage and reducing the amount of clay needed for the completed levee. The COE utilized Early Contractor Involvement (ECI) for this contract. The ECI process allowed for input from the DMM contractor, TREVIICOS South, in order to optimize equipment resources and material requirements. This paper gives an overview of the extensive DMM requirements for LPV-111 and explains the benefits of the ECI process.

Introduction Some people say it is almost impossible to get mining permits in California. Some say the day of the lone mining entrepreneur is past. And some say you cannot make money mining gold where old-timers have already mined it, especially in Tertiary gravels. But a young mining operator and SME member, Tim Callaway, is proving these ideas wrong. Callaway's company, Brush Creek Mining and Development Inc., has the necessary permits for its Gardner's Point gold mine in Sierra County, CA. And, Callaway has secured funds for the 7.7 km'/d (10,000 cypd) Tertiary gravel operation. The company's initial goal is to produce 373 to 466 kg/a (12,000 to 15,000 oz per year) of gold at Gardner's Point mine at a cost of less than $6.43/g ($200 per oz). Feasibility studies are currently being conducted to consider product levels up to the 1555 kg/a (50,000 oz per year) involving additional plants and infrastructure. While exploring for other hard-rock properties, the Brush Creek company already operates the Brush Creek lode gold mine. The mine sits high on a ridge south of Goodyear's Bar, which is located on the North Yuba river. It might be noted that the Brush Creek mine has been the subject of media stories recounting how a mine can operate with sensitivity to the environment. Gardner's Point project In 1983, Callaway negotiated with the Gardners Point Ltd. Partnership for control of the Gardner's Point property. The Partnership had been engaged for three years in securing permits, mapping and drilling, and test mining. The Partnership actually mined about 43.5 dam3 (57,000 cu yd) of gravel, which yielded 25.2 kg (810 oz) of free gold. Later, the Brush Creek company acquired ownership of the property. The company then began its own exploration and development program. As underground development proceeded at the Brush Creek mine, plans matured for a high-volume operation at Gardner's Point. Australian and English investors contacted Callaway. A joint venture was negotiated. The Australian owners became majority participants; the Brush Creek company, a minority participant and the operator. The Australian investors agreed to contribute $3.5 million (60%) to the Brush Creek Joint Ventures. The Brush Creek company will contribute its expertise as well as assets and liabilities valued at $2.3 million (40%). About $2 million has been allocated to the Gardner's Point project. Later, Brush Creek Mining and Development Inc. sold 50.4% of the company's common stock to English investors for $5.4 million. Callaway negotiated this private placement, which permits further exploration of projects being investigated. Geography and history The Gardner's Point mine is located in the northern Sierra Nevada of California, about 9.6 km (6 miles) east of the little town of La Porte in Plumas County. The mine lies high on a ridge above Slate Creek, which divides Plumas and Sierra Counties. La Porte is accessible from the Sacramento area by a winding, paved, two-lane highway. But the mine is reached only by two different unpaved county and Forest Service roads. Both roads include steep grades in and out of the Slate Creek canyon. Mine elevation is about 1.4 km (4600 ft) above sea level. The area is thus threatened by occasional heavy winter snows, though it

Jan 3, 1987

By D. A. Larson

The Bureau of Mines conducted basic experiments to study the process of crack propagation with a wedge indenter. The work was conducted under plane stress conditions in a hard, brittle limestone. The purpose of these experiments was to first gain an understanding of the basic crack propagation process under a sharp indenter, and second, to determine how the crack propagation process could be used to improve mechanical fragmentation systems. Three methods of rock fracture with the wedge indenter were investigated in this program. These were the confined indentation tests, the unconfined splitting tests, and the edge chipping tests. The confined indention tests represent worst case conditions for crack growth and formed the lower bound on fracture efficiency. The unconfined splitting tests represented best case conditions and fixed the upper bound of fracture efficiency. The edge chipping tests represented an idealized fragmentation process based exclusively upon the highly efficient fracture propagation process. Edge chipping achieved a specific energy of 25 in lb f/in3 compared to conventional drag cutters, which required a specific energy of at least 2,385 in·lb f/in3? Thus edge chipping is up to 100 times more efficient than conventional drag cutting. Because of these promising results, more work is planned with the fracture propagation process in three dimensions.

Jan 1, 1987

By Monika Patrycja Polak - Micewicz

This paper presents an approach for estimating the fatigue life for the base of powered roof supports (shield) manufactured by the FAZOS roof support company. FAZOS?s powered roof supports are designed to operate on an inclined coal seam in full caving with a medium, strong roof strength. This shield support is utilized in conjunction with a shearer and face conveyor for a complete longwall mining system. To design shield support, it is essential for contractor to know the physical (hardness, toughness, etc.) and mechanical properties of material (tensile strength, Young?s modulus, etc.) used for the shield support as well as the geotechnical properties of the mine site. The fatigue strength of the shield support material depends on the mean stress, alternating stress, cycle frequency, transport dimensions, mine environment and other factors. In order to estimate the fatigue life for a powered roof support system, it is assumed in this paper that the support must keep the roof stable in the mine under variable load cycles. The approach selected in this study contains Goodman?s model (Goodman, 1899) for all blocks in the design housing which is subjected to sinusoidal load. On this basis, the degree of fatigue damage was calculated and compared to the results of experimental tests. It will be shown that there is a significant detrimental effect on the fatigue life of the base of the powered roof supports due to geometrical notches. The Ramberg-Osgood model and damage accumulation rule (Palmgren-Miner) (Miner M., 1945) were used and numerical analyses were conducted, utilizing ANSYS finite element software. These analyses play a very important role in longwall casing design. The proposed method allows assessment of the yield state and forecast of the structure cracking, taking plastic strains occurrence into account. The presented method is universal and can be applied for fatigue life estimation of other subassemblies of powered roof supports. The final portion of the paper presents results of variable amplitude loading simulations on the S355N and S690Q steel used to make powered roof supports. The results of the physical tests were compared with the results from finite element methods. The proposed approach to calculate fatigue life gives the best correlation between the experimental results and calculated values of fatigue life for the powered roof support base. Finally, the design process uses a simple approach to predict fatigue life in a short time, reducing design costs and providing longer service life for roof supports.

Jan 1, 2012

By S. P. Ball, A. J. Monhemius

In a laboratory study under acidic oxidising conditions, the thiocyanate system gave results at least as good as cyanide and considerably better than thiourea, with modest consumption of SCN (less than 1 kg/t ore). For both cyanide and thiocyanate lixiviants a residence time of about 24 h was required for maximum gold extraction, which was generally in the range of 92-96%. The adsorption of gold from thiocyanate leach liquors was found to be rapid, but activated carbon catalyses the autoreduction of ferric iron to ferrous iron in thiocyanate solutions, suggesting that ion exchange may be a better recovery route

Dec 1, 1995

By Keith Pucalik

Understanding Vibrations fr om Blasting focuses on explaining blast vibrations and their effects on people and homes while keeping an eye on the importance of the use and significance of explosives in our daily lives. Unlike many predecessors, this film will help blasting pro f e s s i o nals explain blast vibrations and address many of the layman’s most fre q u e n t l y asked questions. The film can be used in pubic hearings, given to homeowners during preblast surveys, or played at educational seminars for professionals. The film can also be used after blasting has begun and residents have already experienced vibration events.

Jan 1, 2004

By K. P. Wang

Mining and metallurgy have had a long history in China, and resources there have always been considered promising. Under the People's Republic of China (PRC), a remarkable industrial renaissance is underway that should further gain momentum in the years ahead. Rapid development of minerals have not only brought the PRC prominence in industrialization, but also in world affairs. Chinese mineral developments, especially petroleum, have been increasingly in the news. Oil and gas may have great potential, but a very large coal industry is already in existence. The steel industry ranks fifth or sixth in the world. The PRC is also prominent in fertilizer, cement, and salt production. The export metals are well known. Also, the country is buying heavily in nonferrous base metals. The need to know and the intense interest in the subject have prompted this study. The world significance of Chinese minerals is pointed out. The history of growth and PRC's mineral supply position are reviewed. Evaluations are made of policy considerations and regional and technical factors affecting mineral development. PRC's mineral trade and efforts to obtain equipment, supplies, and know-how are assessed. Specific reviews are made of major mineral sectors, including coal and power, oil and gas, iron and steel, nonferrous metals, industrial minerals, and fertilizers and chemicals. The overall outlook is summarized.

Jan 1, 1975

By R. Boom, J. Halder, B. Snoeijer, B. Deo, A. Overbosch

Operational data of BOF and the slag samples for different starting conditions of phosphorus(0.06–0.26 per cent P) and silicon content (0.3–1.2 per cent Si) of hot metal have been analysed. The contribution of parameters that are well known to affect phosphorus distribution at tap, like basicity, temperature, FeO content of slag, slag mass etc., is investigated through the models of ionic theory of slag, optical basicity, regular solution approach and molecular theory of slag. The best overall results are obtained by the model based on molecular theory of slag in which several operational parameters are also incorporated. The investigations of different slag samples, based on optical, SEM, EPMA and X-ray studies, reveal the effect of MgO and Al2O3on slag morphology and phosphorus distribution in different phases. It is important to consider phosphorus distribution ratio in the solid and liquid part of slag. The solid part of slag, which is mostly dicalciumsilicate, can contain up to 5 per cent phosphorus. The phosphorus content of the liquid part of slag may depend upon the phosphorus content of hot metal or phosphorus load of slag. It is found that incorporation of effect of dicalciumsilicate in the model improves the accuracy of prediction. For better process control, the addition of iron ore towards the end of blow must be avoided while treating high phosphorus hot metal or during the production of ultra low phosphorus steels. Keywords: steelmaking, BOF, phosphorus distribution, slag morphology, MgO, Al2O3,dicalciumsilicate, process control, models

Jan 1, 2004

By A. C. Smith

Although only used in a few U.S. longwall mines, bleeder-less ventilation systems can be an effective spontaneous combustion control method in mines having a demonstrated history of spontaneous combustion. To provide insights for the optimization of bleederless ventilation systems for U.S. underground coal mines, a computational fluid dynamics (CFD) study was conducted to model the spontaneous heating in longwall gob areas using a bleederless ventilation system. A single longwall panel with a bleederless ventilation system was simulated, and typical longwall mine ventilation data were used in the simulations. The permeability and porosity profiles for the longwall gob were estimated using a geotechnical model and were used as inputs for the CFD modeling. The effects of gob permeability and resistance of the collapsed entries on the spontaneous heating were studied. The effectiveness of using nitrogen injection to prevent spontaneous heating in the gob was also examined.1

Jan 1, 2008

By K. E. Brown, J. P. Brill, A. R. Hagedorn, T. C. Doerr

A recent correlation for multiphase vertical flow by Hagedorn and Brown1,7 has been used to examine the effect of numerous variables such as pipe size, gas-liquid ratio, liquid flow rate, liquid viscosity, liquid surface tension, oil API gravity, water cut, etc., on flowing pressure gradients. Most previous correlations were derived by using a form of the general energy equation which assumed negligible changes in kinetic energy. Under certain flow conditions this can lead to serious errors in predicting pressure traverses. Examples of traverses calculated both with and without the kinetic energy term are included here. The Chew and Connully correlation for calculating changes in viscosity with changing pressure and temperature has been extended so that the effect of a changing viscosity with depth on pressure gradients can also be predicted. Examples illustrating the effect of tubing size show the importance of this correlation in determining pipe sizes for initial well completions. Limitations on production rates in small pipe sizes from excessive friction losses can be predicted with greater accuracy. The combined use of a vertical-flow correlation with a horizontal-flow correlation provides a method for determining the maximum flow rate possible from both flowing and gas-lift wells. Examples are included to illustrate application of the combined use of vertical and horizontal-flow correlations in optimizing production rates and minimizing excessive costs from over injection of gas in gas-lift wells. INTRODUCTION The problems of multiphase vertical and horizontal flow are immediately encountered in any producing well. Fig. 1' shows three stages of production: flow in porous medium, vertical flow and horizontal flow. All three stages affect the production rate from a well. If we are confronted with a particular well and consider only the variables involved in the vertical and horizontal stages of Fig. 1, we should be capable of calculating the flowing bottom-hole pressure necessary to produce a particular flow rate. A change in any of the variables results in a new solution to the problem. Recent approaches in developing horizontal and vertical-flow correlations have improved to the extent that the solution can now be obtained with more confidence than previously. VERTICAL AND HORIZONTAL FLOW CORRELATIONS Since Poettmann and Carpenter's' original work in multiphase vertical flow, there have been many additional vertical-flow correlations developed which have greatly improved the accuracy of pressure-loss calculations. These

Jan 1, 1967

By G. H. McKay

AT the Eagle mine, near Gilman, Colorado, where the Empire Zinc Company have installed an underground mill, transportation problems were comparatively simple. A railway siding on the Denver and Rio Grande railway is equipped with an unloading dock or platform at the portal of their service incline adit to the mill. This 18-degree incline is approximately 600 feet long from the unloading track to the head of the mill skipway. For the Big Missouri mill, upwards of 2,500 tons of material and equipment had to be trucked from tidewater at Stewart, B.C., a distance of 21 miles to the Big Missouri camp at elevation 2,800. From that point, this freight had to be moved either over or through the Big Missouri ridge, rising to elevation 3,450, to its final location 800 feet from the surface between elevations 2,150 and 2,350. Immediately after leaving the government dock at Stewart, the road crosses the International boundary line into Hyder, Alaska, and then follows a water grade for eleven miles along the lower stretches of the Salmon river. leaving the river, the road climbs for two miles before crossing back into British Columbia territory at Silver Heights, and then continues for another mile and a half to where the Big Missouri road branches off from the main road to the Premier mine. For a distance of four miles from the junction of the roads, the Missouri road is very narrow, with many sharp curves and with irregular up and down pitches and grades up to 25 per cent until it reaches the Summit. From there on, a fairly easy grade leads a mile and a half to the end of the road on Joker Plats. In winter, the last stretch of road is subject to heavy snow drifting, especially through a narrow funnel-shaped gulch, known as 'The Gap', where the snow may pile up to a depth of over twenty feet.

Jan 1, 1938

By C. Dan Kealy

Recent antipollution legislation for the control of mine tailings and waste-water has required an increasing number of tailings ponds. Many of these new waste-retention ponds are being constructed in congested locations, or the older ponds have reached such a size that--if failure occurs--they pose a threat to human life and public property. Although the typical tailings-disposal embankment represents--to the casual-, observer or the economy-minded mine official--a rather ugly but benign and stable pile of waste, they are in fact an extremely sensitive structural mass, retained behind the frailest of dikes. Failure of the waste mass requires only a minor change in water retention or weather conditions, erosion or piping of the ground strata, shifts in load or slight earth tremors. When failures occur, the results can be disastrous. In the U.S., we have been fortunate that, so far, pond failures have not caused loss of life. Thus, failures in this country have attracted little public attention. Present tailings-pond construction methods used by the mining industry require the barest money investment, and little engineering effort. Unfortunately, this superficial approach may increase short-term profits, but the practice may be conducive to the construction of needlessly weak structures. In coming years many of these designs will probaly become corporate liabilities. A typical pond is portrayed in Figure IA. This particular pond in Arizona is 1 mile long and 3/4 mile wide. Illustrated in Figure lB is a representative pond in cross section. This paper in concerned with two basic features common to all tailings disposal: (1) location of the phreatic surface within a tailings-pond embankment because of its influence on embankment-slope stability, and (2) prediction of

Jan 1, 1971