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By James J. Roettger, Robert J. Mitchell

"The results of a series of model stope pours designed to investigate working pressures on bulkheads during hydraulic pouring of classified tailings backfill are reported. Total bulkhead pressures and fill water pressures were monitored under the condition of a fully saturated backfill. Similitude of the model testing is discussed and equations are developed to estimate bulkhead pressures under prototype conditions. The model results show that good base drainage, combined with a bulkhead setback, can reduce the expected bulkhead pressures to values such that timber or concrete block structures should be capable of supporting a saturated backfill. Introduction Bulkheads are used in underground running operations to block drift openings in order that hydraulically placed sand backfill can be contained in stope pours. Whenever possible, the sand fill is designed to have sufficient percolation rate so that excess hydraulic transport water will gravity drain out through the bulk headed drifts. This avoids costly decanting systems. Early bulkhead design assumed that the bulkhead pressure could be as high as 0h = Hy where H is the fill height and ""y is the saturated unit weight of the fill (Thomas et al., 1979)(1). A typical design pressure for a 50 m fill height would be 1250 kPa giving a design force of 12,500 kN on a bulkhead located in a drift of 10m2 in area . Typical bulkheads were 1 m thick heavily reinforced concrete structures formed and poured into a notched drift. Not only were these expensive structures but the associated problems of inside drainage systems and curing time delays increased production costs. As experience with bulkheads for large bulk pours increased and fill pressure measurements became available [see, for examples, Libby et al., 1975(2), Askey et al., 1978(3)] , 'free drainage' timber and concrete block bulkheads were designed. Substantial savings have been realized using these types of bulkheads but greater engineering design and monitoring of backfill pours is necessary to ensure that backfill pressures do not exceed the bulkhead design pressures.The effective and total stress components of fill pressure, the engineering concepts associated with the 'free drainage' design and some detailed design considerations have been discussed by Smith and Mitchell (1982)(4) . It is important to the safe use of these designs, however, that the basic engineering concepts be demonstrated and communicated to those responsible for the day-to-day backfill operations. This paper describes and explains observations from a series of model studies designed to measure bulkhead pressures in a saturated fill."

Jan 1, 1984

By Heinz Distelmeier

The New Austrian Tunneling Method was, as is well known, developed from conventional rock tunnelling. In Germany about 10 years ago the NATM began to be applied to partially stable soils by incorporated excavation and support methods to allow its use with these soils. The advantages of this tunnelling technique - adaptability, ecomomy, and quality have resulted in its widespread usage. Today, about 85 % of all mined tunnels in Germany are produced with this technology. This rapid development has resulted in about 40 companies operating within a geographical area about the same size as the state of Illinois that are capable of utilizing the NATM. In most cases German contract/award procedures allow the contractor to develop alternate design and plans. As a result of this flexibility and intense competition, safety factors have been gradually reduced to the lower limit of what could be regarded as demonstrably safe, and the utilization of the NATM has expanded to include higher risk conditions, namely * excavating larger cross sections. * working with less overburden. * work undertaken under less stable soil conditions.

Jan 1, 1983

By C. G. McLachlan

THIS paper outlines a series of tests carried out during the first six months of 1927, in the laboratory and mill of the Moctezuma Copper Co. The object of the tests was to determine whether the soluble salts present in the mill circuit water were having a detrimental effect on the recovery made by flotation. To accomplish this object a series of water analyses were made, followed by flotation experiments in which definite quantities of the salts found were added as addition agents. Before proceeding to describe the results obtained in the course of the investigation, reference will be made to five articles that have appeared during the last two years in which the action of such salts is discussed. Two of these are by A. T. Tye1,2 and describe flotation practice at Cananea and the way in which water high in ferrous and ferric salts is conditioned for differential flotation. Two, one by A. C. Munro and H. A. Pearse3 and the other by H. A. Pearse,4 outline Britannia milling methods, and the advantages that have been derived from ore washing; while in the fifth, A. W. Hahn5 summarizes the results of laboratory experiments in which ferrous, ferric and aluminum sulfates have been added in varying amounts. The mill of the Moctezuma Copper Co. has a daily capacity of 3000 tons, and is situated about 75 miles south of Douglas, Arizona, on the Rio de Nacozari, in the Mexican state of Sonora. The ore treated is mined from the company's mine at Pilares, about 5 miles southeast of the Concentrator. This ore contains about 2.5 per. cent. copper -- present almost entirely as chalcopyrite-and 10 per cent. iron, of which

Jan 1, 1928

By Paul Biggs

This report presents information on 77 waterflood projects in 31 Montana oilfields. The study shows the locations of the projects, the sources and amounts of injection water, and the results in oil produced. Waterflooding, a secondary recovery technique, began in Montana about 40 years after the initial oil discovery in 1920. Often, the difference between water disposal by injection and pressure maintenance operations is not clear. Water injected at the projects in 1973 was 157.7 million barrels. In 1973, the 31 fields having waterflood projects produced 28.3 million barrels of oil valued at $88.4 million. Both in volume and value, this represents over 80 percent of the State's 1973 oil output. The projects are making possible the recovery of additional oil, thus contributing to the conservation of oil and lessening the impact of the current oil shortage.

Jan 1, 1976

By Michal Topolnicki

Deep Mixing Series: This article is the second keynote highlighted from DFI's virtual Deep Mixing Conference in 2021, for which Topolnicki served as a committeee co-chair Polish applications of deep soil mixing (DSM) technology occupy a leading position in Europe. That includes use for road and railway embankments, bridges, residential and industrial build- ings, silos, commercial centers, slabs, car parks and storage yards, excavation supports and cut-off walls. In fact, more than 350 road and railway viaducts and 200 wind turbines have been founded nationally on DSM columns, which are firsts on an international scale. This represents more than 1,200 imple- mentations by the Polish geotechnical industry. Considering the need to update DSM design recommendations, this article will attempt to summarize the best practices of wet DSM design and implementation, in particular. It draws on 20 years of experience and will high- light the properties and principles of the design of stabilized soil and lessons learned. Case studies are included to fur- ther understanding of the careful con- siderations needed with this technology.

Apr 1, 2022

By W. Hurst, A. F. van Everdingen

A distillate-bearing sand complex is often made up of sand stringers of different permeabilities. In order to take into account the influence of the different permeabilities, "parallel flow" is defined, and this concept is used to compute the recovery efficiency of recycling such a sand complex. In the first approximation the position of the wells with respect to one another is not considered. In order to compute the effect on the recovery efficiency of the position of the wells, the area of a field is considered to be made up of rectangles; each rectangle containing one input well in the center and two producers located symmetrically with respect to the input well. Formulas are given from which to obtain the pressure and streamlines in a steady-state flow. A method is devised to compute rapidly the successive positions of the dry gas front. If the field is irregular in shape, pressure and streamlines can be obtained by a potentio-metric electrical model study. By using the concept of "parallel flow" and the results obtained by mathematical analysis or by electrical model study for a homogeneous formation, the effects of different permeabilities and of the location of the wells can be established. From these studies it is apparent that the efficiency of recycling can be profoundly influenced by differences in permeability among the various parallel strata. Introduction With the discovery of an increasing number of gas-distillate fields in the Gulf Coast, engineers have had occasion to give more thought to the performance of these reservoirs, as evidenced by the literature published in recent years. In the majority of studies published so far the formations are considered to consist of uniform, homogeneous sand. In this paper the authors wish to bring out the effect of variations in the permeability of the formations on the over-all recovery efficiency of wet gas in cycling operations. The importance of the permeability profile is clearly indicated by the fact that in gas cycling, highly permeable stringers in an otherwise tight sand can allow complete displacement of wet by dry gas in these stringers long before the wet gas in the tight portions of the sand is displaced. This by-passing will be reflected by a reduction in the condensate content of the production sooner than can be anticipated from a mathematical analysis or an electrical model study on uniform sands. Electrical model studies or mathematical analyses cannot take into consideration the manifold variations of permeability within the reservoir. Experimental as well as analytical difficulties make it necessary to consider the prototype for either of these studies as a perfectly uniform sand. Mathematical analyses are applicable only when a reservoir can be divided into units of simple geometrical form, of uniform thickness throughout. Electric model studies are capable of giving information on reservoirs of any shape or thickness, but it is essential that the sand be considered homogeneous, so that three-dimensional flow can take place. The method of approach in the following

Jan 1, 1946

By W. Hurst, A. F. van Everdingen

A distillate-bearing sand complex is often made up of sand stringers of different permeabilities. In order to take into account the influence of the different permeabilities, "parallel flow" is defined, and this concept is used to compute the recovery efficiency of recycling such a sand complex. In the first approximation the position of the wells with respect to one another is not considered. In order to compute the effect on the recovery efficiency of the position of the wells, the area of a field is considered to be made up of rectangles; each rectangle containing one input well in the center and two producers located symmetrically with respect to the input well. Formulas are given from which to obtain the pressure and streamlines in a steady-state flow. A method is devised to compute rapidly the successive positions of the dry gas front. If the field is irregular in shape, pressure and streamlines can be obtained by a potentio-metric electrical model study. By using the concept of "parallel flow" and the results obtained by mathematical analysis or by electrical model study for a homogeneous formation, the effects of different permeabilities and of the location of the wells can be established. From these studies it is apparent that the efficiency of recycling can be profoundly influenced by differences in permeability among the various parallel strata. Introduction With the discovery of an increasing number of gas-distillate fields in the Gulf Coast, engineers have had occasion to give more thought to the performance of these reservoirs, as evidenced by the literature published in recent years. In the majority of studies published so far the formations are considered to consist of uniform, homogeneous sand. In this paper the authors wish to bring out the effect of variations in the permeability of the formations on the over-all recovery efficiency of wet gas in cycling operations. The importance of the permeability profile is clearly indicated by the fact that in gas cycling, highly permeable stringers in an otherwise tight sand can allow complete displacement of wet by dry gas in these stringers long before the wet gas in the tight portions of the sand is displaced. This by-passing will be reflected by a reduction in the condensate content of the production sooner than can be anticipated from a mathematical analysis or an electrical model study on uniform sands. Electrical model studies or mathematical analyses cannot take into consideration the manifold variations of permeability within the reservoir. Experimental as well as analytical difficulties make it necessary to consider the prototype for either of these studies as a perfectly uniform sand. Mathematical analyses are applicable only when a reservoir can be divided into units of simple geometrical form, of uniform thickness throughout. Electric model studies are capable of giving information on reservoirs of any shape or thickness, but it is essential that the sand be considered homogeneous, so that three-dimensional flow can take place. The method of approach in the following

Jan 1, 1946

By Carl P. Venzke

Mining lignite in the Gulf Coast often requires some interaction with shallow ground water system. Suggestions for determining ground water data and analysis requirements for regulatory compliance are given. Simple methods for estimating mine inflow seepage, ground water level declines, and changes in ground water chemistry, which may result from mining, are discussed. The mining of lignite often results in interaction with shallow ground water systems. An evaluation of the interaction is required as input to mine permitting and engineering. Your evaluation will proceed more smoothly and produce more meaningful results with some planning prior to performing your evaluation. The following are tips to consider in planning and carrying out a successful study.

Jan 1, 1982

By T. V. Moore, H. D. Wilde

In many of the important problems of the petroleum engineer, it is necessary to know accurately the laws governing the flow of gas and liquid mixtures in vertical pipes. Although much work has been done along these lines, no satisfactory solution to the problem has been found. A good theoretical discussion of the energy balance in a gas-lift has been published by Versluys.1 One of the most important factors affecting the efficiency of the flow of oil and gas mixtures is slippage, and in most of the experimental work that has been done no provision has been made for the measurement of this quantity. As Versluys pointed out, since there is no method now known to estimate it from the data usually taken, slippage must be determined empirically. This paper presents the results of some work carried on to measure slippage in short experimental gas-lifts. As shown herein, slippage can be easily calculated in a vertical pipe carrying a mixture of oil and gas if the fractions of the pipe occupied by liquid and gas respectively are known. In this work, the fraction of the pipe occupied by the liquid was measured under a wide variety of conditions and the relationship between this fraction and other quantities, which are easily measured in ordinary work, was determined. It was hoped that the quantitative relationship obtained from this work could be used for making accurate calculations in flowing or gas-lift wells, but unfortunately it did not check satisfactorily when applied to actual wells. Apparently flow in long flow pipes is more efficient than in the short ones used for the experimental work. Nevertheless, it is felt that the data themselves arc of interest; that the method of attack may be of value in future work and that the relationship derived between slip and the relative velocities is a contribution toward the solution of the gas-lift problem.

Jan 1, 1931

By J. M. Lovejoy

Various estimates have been made as 60 the percentage of oil left in a field after the wells have become so small that it is no longer practical to produce them. Engineers have given the matter much study and can substantiate their figures by data taken from fields from the Appalachians to California. The average oil sand has a porosity of about 20 per cent., which gives a capacity per acre-foot of approximately 1500 bbl. The sand thickness in Oklahoma pools averages 20 ft. With 20 per cent, porosity and a 20-ft. sand thickness, the capacity per acre is 30,000 bbl., yet these pools will seldom yield more than 5000 bbl. to the acre. These figures gupport the theory that at least 50 per cent. of the oil remains in a sand after all known methods to recover it have been used. Certainly we can never recover all the oil, unless in years to come oil becomes so rare and yet so necessary that the price will justify sinking shafts into the abandoned fields and regular mining methods of drifting and stoping. However, with improved methods of production and conservation of the natural agencies of expulsion, we should be able to increase recovery. It is with this in mind that this paper, relating to the effect of back pressure on wells, is presented. Except in the fields where production is caused by hydrostatic pressure, the chief agency for getting oil out of the sand into the hole is the gas that occurs with the oil. After the pressure has declined, probably gravity also is a factor, but not an important one. With a given amount of oil in a sand and a given amount of gas occurring with the oil, the ratio of gas volume per barrel of oil is the key to the ultimate recovery from that sand. Our efforts should be along lines that will lower this ratio and make the gas, the agency given us by nature, do its work better and yield more of the oil, of which it is a part. T. E. Swigart,' of the U. S. Bureau of Mines, has published an extract of the paper he is preparing under the title "The Effect of Back Pressures. on Wells." The experiments described were made on two

Jan 1, 1924

By N. A. Stockett

Southeast Missouri is the largest and oldest lead-producing district in the United States. For the year 1941, the statistical picture of pig-lead production, stated in short tons (partly estimated by the Engineering and Mining Journal) is as follows. Tons World production................. 2,000,000 United States Production .........- 460,000 Southeast Missouri production..... 142,000 The consumption of primary lead in the United States in 1941 was approximately 900,000 tons, or almost double the country's production. The largest previous year's in in the United States was 718,000 tons, in 1926. The largest quantities of lead are used for cable sheathing, storage batteries and white lead. During 1941 tetraethyl lead for auto and aviation gasoline consumed 50,000 tons of lead. The entire lead production of Southeast Missouri is now mined by the St. Joseph Lead Co., whose dominant position as the largest producer in the United States of lead directly from ores is best shown by the fact that in 1941 it produced approximately 31 per cent of the lead production of the United States from its mines in southeast Missouri, where 22,000 tons of ore, averaging over 3.00 per cent lead, is mined per working day. It is known that lead was mined at Mine La Motte, Madison County, Missouri, by Renault in 1723. Other white men and Indians probably did some mining prior to that time. Since 1865, the recorded production to Jan. I, 1942, shows that the St. Joseph Lead Co. and the various other companies that have operated in St. Francois County mined lead ore, which, after milling and smelting losses produced 5,980,000 short tons of pig lead. • About 95 per cent of the present lead production of Southeast Missouri is mined in St. Francois County. The northern part of this area is 60 miles south of st. Louis. The remainder of the lead is obtained at Mine La Motte, about 25 miles southeast from the center of the producing area in st.Francois county, Prospecting In this district, most of the ore is discovered by surface and underground diamond drills and by prospect drilling underground with rock drills. Each 2-ft. length of the cuttings from these Jack-hamer prospect holes is assayed for lead. These holes are marked and the records are entered on maps. It has been found that close drilling—100-ft. centers of holes, and sometimes less—is necessary in order to locate most of the smaller commercial ore bodies, many of which previously had been missed by drilling the areas with holes spaced 200-ft. centers or more. To date, geophysical and other methods of prospecting, apart from diamond and Mining Practices of the St. Joseph Lead Company in Southeast Missouri

Jan 1, 1943

By N. A. Stockett

Southeast Missouri is the largest and oldest lead-producing district in the United States. For the year 1941, the statistical picture of pig-lead production, stated in short tons (partly estimated by the Engineering and Mining Journal) is as follows. Tons World production................. 2,000,000 United States Production .........- 460,000 Southeast Missouri production..... 142,000 The consumption of primary lead in the United States in 1941 was approximately 900,000 tons, or almost double the country's production. The largest previous year's in in the United States was 718,000 tons, in 1926. The largest quantities of lead are used for cable sheathing, storage batteries and white lead. During 1941 tetraethyl lead for auto and aviation gasoline consumed 50,000 tons of lead. The entire lead production of Southeast Missouri is now mined by the St. Joseph Lead Co., whose dominant position as the largest producer in the United States of lead directly from ores is best shown by the fact that in 1941 it produced approximately 31 per cent of the lead production of the United States from its mines in southeast Missouri, where 22,000 tons of ore, averaging over 3.00 per cent lead, is mined per working day. It is known that lead was mined at Mine La Motte, Madison County, Missouri, by Renault in 1723. Other white men and Indians probably did some mining prior to that time. Since 1865, the recorded production to Jan. I, 1942, shows that the St. Joseph Lead Co. and the various other companies that have operated in St. Francois County mined lead ore, which, after milling and smelting losses produced 5,980,000 short tons of pig lead. • About 95 per cent of the present lead production of Southeast Missouri is mined in St. Francois County. The northern part of this area is 60 miles south of st. Louis. The remainder of the lead is obtained at Mine La Motte, about 25 miles southeast from the center of the producing area in st.Francois county, Prospecting In this district, most of the ore is discovered by surface and underground diamond drills and by prospect drilling underground with rock drills. Each 2-ft. length of the cuttings from these Jack-hamer prospect holes is assayed for lead. These holes are marked and the records are entered on maps. It has been found that close drilling—100-ft. centers of holes, and sometimes less—is necessary in order to locate most of the smaller commercial ore bodies, many of which previously had been missed by drilling the areas with holes spaced 200-ft. centers or more. To date, geophysical and other methods of prospecting, apart from diamond and Mining Practices of the St. Joseph Lead Company in Southeast Missouri

Jan 1, 1943

Leichhardt Colliery is developed for underground mining of coal seams at depths exceeding 280 m. Investigations of the area were conducted in phases, each designed to delineate seam characteristics more accurately and to indicate with increasing precision the nature of local geological features and the ranges of those coal properties susceptible to variation. The investigational campaign is described phase by phase summarizing evaluation of the area at the conclusion of each phase. Predictions of geological conditions likely to influence engineering planning are contrasted with actual conditions observed during trial mining.

Jan 1, 1974

By George Carlos dos Santos Anselmo

O efeito de memória de forma tem como principal objetivo a recuperação da forma por meio de aquecimento acima das temperaturas críticas de transformação. Fitas das ligas Ti50Ni46Cu4 e Ti50Ni44Cu6 (% at) foram preparadas através do processo melt spinnig com velocidade da roda de 38 m/s e 50 m/s. A caracterização das fitas foi feita por Calorimetria Diferencial de Varredura (DSC) e Microscopia Eletrônica de Varredura (MEV). Foi observado que com o aumento da velocidade de rotação da roda de 38 para 50 m/s um refino de grão foi observado e as temperaturas de transformação diminuíram chegando à variação de aproximadamente 7°C. A solidificação rápida produz defeitos na estrutura da liga e, consequentemente, uma maior dificuldade de ocorrer as transformações de fase, bem como produz um refino de grão.

Aug 16, 2017

By Johns D. R

The producers of mineral sands on the East Coast of Australia might be regarded as having a simple task of selling Rutile and Zircon. Such is not the case. Differing quality and grain size requirements plus the dramatic increase in the percentage of mineral sold in a processed form have meant a large increase in the number of different end products handled. The resulting sales control problems are compounded by the need to be able to deliver against a large number of separate contracts which may relate to spot or long term sales in small quantities or in bulk shipments. Methods of helping management control this situation have been devised and incorporated into a suite of computer programs. Experience with the approach has been very satisfactory. The effect of changes to shipping schedules, commitment to new or changed orders, or proposed changes to production can be evaluated as and when necessary with little bother. Confidence in decisions taken is high since the process of data collection has been designed to involve

Jan 1, 1977

By Roy A. Lindgren

Since the year 1643, when the first blast furnace in America for treating iron ore was built at Saugus, Mass., out of mica schist quarried in the neighboring district, the procurement of a suitable refractory for furnace lining has been a problem of concern to the operators of furnaces. The stacks built of mica schist continued to smelt iron ore until about 1836, when, according to F. H. Norton, the first firebrick were produced1, at Queens Run, Pa. Other writers speak of brick having been molded and burned in Massachusetts about the year 1834. In 1841, Andrew Russell began to produce medium refractory plastic clay brick near East Liverpool, Ohio, that were used for lining blast furnaces1. The well-known Kentucky clay-producing district was not opened up until the year 1871, but since then it has produced a large percentage of the linings for iron blast furnaces. While some strides have been made by the refractories industry during the 100 years that have passed since the first firebrick were produced, it has been only during the last two decades that any real progress has been made towards bettering the product, even though the method of production had improved. Perhaps the fault lies with the user of the brick rather than with the producer, for not sooner demanding a superior product. During the past 15 years the tonnage produced per lining has increased from 500,000 gross tons to 1,000,000 gross tons, and now some furnaces are producing 1,600,000 gross tons and better on a single lining. It is true that enlarged capacity of furnaces and improved practice have accounted for some of this increase in tonnage, nevertheless better quality in firebrick must be given credit for its share. However, we are not yet ready to say that we have reached a maximum life of furnace lining. We believe that a better product can be produced and that the refractories industries of America will, through their extensive research depart-

Jan 1, 1937

Gold and copper mineralization in the Parkes area is hosted by a meridional sequence of Late Ordovician to Early Silurian igneous and sedimentary rocks on the central northern edge of the exposed Lachlan Fold Belt. The mineralized area straddles two zones separated in part by the Parkes Thrust and exhibiting different styles of deformation and mineralization (Figure 1). The western zone is characterized by gently folded rocks, with shallow dips and weak to non-existent axial plane cleavage. Faulting is restricted to directions oblique to bedding. Numerous occurrences of minor copper mineralization are known, but of recent national importance is the discovery of the Coradgery- Goonumbla porphyry copper-gold deposits by Geopeko Ltd. A resource in excess of 250 million tonnes has been delineated (Jones, 1985), and this represents the first porphyry deposit of sufficient grade and tonnage to be potentially mineable in New South Wales. The eastern zone is much more strongly deformed. Folding is tight with strongly developed axial plane cleavage. Faulting is abundant both parallel and oblique to bedding. Quartz veining is also abundant, and a narrow belt of gold mineralization adjacent to the Parkes Thrust stretches from Forbes in the south, through Parkes and Peak Hill, to Tomingley in the north. Over 31 tonnes of gold have been produced from this gold belt, mostly before 1914, and now three deposits show good potential for redevelopment - Peak Hill, and the London-Victoria and Lachlan lines of lode.

Jan 1, 1987

By R. E. Perry

To develop new or improved flotation methods for beneficiating low-grade red iron ores, the Bureau made many bench scale and continuous anionic flotation tests on ferruginous sandstones and calcareous iron ores from the north-eastern part of the Birmingham, Ala., iron district. The ores contained about 21 to 36 percent iron, a to 11 percent lime, and 22 to 64 percent silica. Production of iron concentrates containing 48 to 52 percent iron was technically feasible in batch tests, and the iron recoveries ranged from 85 to 92 percent. In continuous tests 49 to 51 percent iron products were obtained with 80 to 90 percent recovery.

Jan 1, 1962

By John Ralston, Jinming Duan, David R. E. Snoswell, Daniel Fornasiero, Jingwu Yang

The colloidal stability of synthetic silica spheres with clean, methylated and dehydroxylated sur¬faces was studied at different concentrations of dissolved gas and KCl electrolyte at a fixed pH of 4.2. A classic stability ratio/electrolyte concentration analysis shows that hydrophobic, methy¬lated particles undergo faster rates of aggregation with increasing concentrations of dissolved carbon dioxide. Similar data for hydrophilic particles and dehydroxylated particles show no change as a function of dissolved carbon dioxide concentration. Zeta potential data behave simi¬larly, showing a strong influence of dissolved gas only for methylated particles. The results are interpreted in terms of DLVO theory, with the surface-to-surface interaction dominated by the presence of very small protruding bubbles. Direct evidence for the existence of these very small gas bubbles (or "nanobubbles") was obtained using tapping mode atomic force microscopy. Small bubbles do not form on smooth, hydrophilic, or dehydroxylated silicon oxide water sur¬faces immersed in aqueous solutions under known levels of gas supersaturation. Randomly dis¬tributed small bubbles were observed over the whole surface of observation on methylated surfaces of controlled roughness. Bubbles formed on rough, methylated surfaces were larger and less-densely distributed than those on a smooth surface of similar hydrophobicity. The process of bubble coalescence was observed as a function of time. The macroscopic contact angle, measured with respect to the aqueous or gas phase, is very different from the microscopic contact angle detected by TMAFM and appears to be due to the influence of line tension at the pinned three¬phase contact line. The latter has a value of -3 x 10-10 N and acts to stabilize the small bubbles, flattening them and thereby reducing the Laplace pressure.

Jan 1, 2005

By Anthony Finch

Many mines combine open pit with underground mining, and on many occasions the underground mine is an extension of the open-pit. In these circumstances the decision about where the open-pit stops and the underground starts is crucial and driven by many factors. This paper looks at some of the ways that this cut-over can be calculated and specifically examines the calculation of it using modern mine optimization software. The paper provides a case study which will review various outcomes using these techniques, and demonstrates the influence of various factors on the optimal transition cut-over point. Biographies Mr Finch is a Divisional Manager and a Principal consultant at Snowden Mining Industry Consultants in Vancouver, Canada. At Snowden Mr Finch leads a team of engineers that perform mining engineering studies for projects around the world. Prior to joining Snowden Mr Finch was the Mining Manager at Barrick?s Henty mine in Tasmania Australia. Prior to that Mr Finch has held a variety of roles in both consulting and operations working for various organisations at various levels in the Asia Pacific region. Mr Finch gained a bachelor?s degree in Mining Engineering from the University of Queensland in 1986, and a bachelor?s degree in Economics from the University of Queensland in 1993. His expertise is in mine planning, mine optimisation and mine management. Dr Elkington is a Consultant at Snowden Mining Industry Consultants in Perth, Australia. He is responsible for the design and implementation of Snowden?s proprietary optimization software products. Prior to joining Snowden Dr Elkington completed his PhD in Mine Optimisation at The University of Western Australia, and bachelor?s degrees in Engineering (Hons) and Commerce from The University of Western Australia. He specialises in optimization and trade-off studies, and has consulted on projects across all major commodities and regions.

May 1, 2011