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By A D. Campbell

The Homer Tunnel is located in a remote area of the South Island of New Zealand and carries large numbers of tourists to Milford Sound through an avalanche prone area. The tunnel is 1280 m long with a steep ten per cent unidirectional grade descending to the west. Construction of the tunnel began in the 1930s and was completed to a nominal 6 m width in 1954. In 1996, two passing bays were stripped-out to accommodate bi-directional flow of tourist coaches. During all phases of construction and widening there have been episodes of strain bursting.The condition of the tunnel and standard of internal services is below current international practice, principally in terms of; in-tunnel air quality, fire life safety, ground support, and road safety. A number of near-miss events have occurred involving coach fires on the approaches and inside the tunnel. The national road authority, NZTA, is considering a substantial investment to improve amenity and safety of the tunnel.This paper describes the rationale for the proposed upgrade works and the investigations undertaken to enable that design. A holistic approach to road tunnel safety has been adopted that balances the key interrelated safety drivers, namely; tunnel lining, traffic operations, ventilation, power supply and egress while ensuring continuity of safe access to Milford Sound.

Mar 8, 2011

By Michael Arnold

"BAUER Foundation Corp. was one of three contractors awarded with the installation of a cut-off wall at the Herbert Hoover Dike Rehabilitation project. The cut-off wall was constructed up to 84 feet deep and 25 inches thick. It extended from the crest through the middle of the existing dike into the underlying peat, sand, and rock layers. BAUER used the cement deep soil mixing method of Cutter Soil Mixing (CSM) to install the wall. Soil mixing was facilitated by first removing the peat layer in the wall alignment using Kelly drilling and replacing it with suitable backfill, resulting in a secant pile wall arrangement of replacement columns. BAUER successfully finished four task orders with a total length of just over 10 miles. Up to six rigs of the types BAUER BG 28, BAUER BG 40 and RTG RG 25 were concurrently used to perform the replacement columns and the cut-off wall installation.The paper introduces the project, the geotechnical site conditions, and the requirements specified by USACE. It focuses on the specific adaptation of the CSM method to the site conditions and on the equipment used. Strength and permeability results obtained from an extensive testing program are presented. The impact of the curing conditions on lab and in-situ test results is studied, and test results are related to soil conditions.PROJECTThe Herbert Hoover Dike is a 143-mile-long dike encircling Lake Okeechobee in south central Florida. When it was constructed in the 1930s and 1960s, the purpose of Herbert Hoover Dike was flood protection from hurricanes. However, during the 1970s a higher lake level was maintained permanently to provide local agriculture with water. Later, damage became apparent during two nearly back-to-back high water events in the 1990s, when numerous sink holes, seeps, pipes, and boils were observed (Fig. 1). In 2000, the Congress approved USACE to propose rehabilitation measures. The installation of a cut-off wall into the existing dike was chosen during the initial design process as the preferred measure to improve the safety of the dike (Davis et al. 2009).The first section of the dike to be rehabilitated was Reach 1 located along the southeast side of the lake between the towns of Port Mayaca and Belle Glade. An indefinite delivery indefinite quantity (IDIQ) multiple award task order contract (MATOC) was issued for this 22.4-mile-long stretch by USACE in 2007. BAUER Foundation Corp. (BAUER) was one of the three contractors that succeeded in the qualification process. Each of the three successful contractors had their own novel construction techniques. In the years 2008 to 2012 BAUER executed four task orders totaling over 10.0 lineal miles of cut-off wall with 3.3 million square feet of design surface area."

Jan 1, 2015

By J. A. Rusnak, K. M. Mohamed, M. A. Van Dyke, M. M. Sears, G. Rashed

"Researchers from the National Institute for Occupational Safety and Health (NIOSH) recently developed a coal-mass model to realistically simulate the deformation and loading behaviors of the ribs of coal pillars in underground coal mines. The scale-dependent properties (stiffness and strength) of coal material were considered in the coal-mass model. In this paper the orientation of face cleat with respect to driving direction was integrated in the coal-mass model. The controlling parameters (dimensionless coal-mass scale and fracture strains) of the modified coal-mass model were calibrated using a published case study of coal pillar strength. Numerical models with wide ranges of controlling parameters were conducted to simulate the test pillar. The best match between the numerical modeling results and the measured stresses and deformations was achieved by using a coal-mass scale of 30 and fracture plastic shear and tensile strains of 3.25% and 0.325 %, respectively. INTRODUCTION The failure of coal pillar ribs by itself are a major hazard in underground coal mines. Furthermore, failing ribs can indirectly contribute to roof and floor instability by increasing opening widths across intersections and entryways. Over the past decade, rib failures have resulted in 12 fatalities, representing 28% of the ground-fall fatalities in U.S. underground coal mines. Mining depth has always played a very important role in assessing rib stability. Gauna and Mark (2010) completed an analysis of rib fatalities that occurred between 1996 and 2010. One of their most prominent and influential findings was the identification of a relationship among fatalities, depth, and mining height. Therefore, Coal rib stability will continue to be a challenge for future deeper mines in U.S. coal basins. In the past several decades, research efforts have focused on roof support. The current rib control practice in U.S. coal mines is to select rib bolts through a trial-and-error approach (Mohamed et al., 2015a). Rib failure incidents can be can be substantially reduced or even eliminated by adopting an engineering-based coal rib design approach. The factors affecting rib stability in coal mines are numerous and mutually dependent. These factors include but not limited to mining height and overburden depth, interburden thickness for multiple-seam mining, coal strength, cleat density, entry direction with respect to cleat orientation, existence or absence of partings in the coal, percentage of extracted roof and/or floor rock, density of rib bolt support (Mohamed et al., 2015a). Moreover, it is difficult to isolate the particular effect of a specific factor on the overall rib stability. Therefore, a reliable empirical rib design approach is not achievable because it requires a significant number of case histories to be collected in order to have a reasonable range of all of the critical parameters. However, numerical modeling can be a practical tool to assist with rib support design if the modeling is realistic, which can only be achieved through calibration and validation of the numerical model against field data."

Jan 1, 2018

Demonstrate the technical feasibility of using nontraditional, low-rank, coal-based fuels and new coal-based technologies for mineral and metallurgical applications. Approach A cooperative research effort was initiated between the Bureau of Mines, U.S. Department of Energy and the minerals industry to extend the application of the fixed-bed gasification process to low-rank Western coals. The research effort enabled cooperators to gain operating experience in the use of hot, raw producer gas for iron ore pellet induration and other high-temperature mineral processes. Researchers were able to gather data regarding the fundamental engineering aspects of the fixed-bed process and gas cleanup for a wide range of solid fuel properties. Applying Fixed-Bed Gasification As a prerequisite to gathering the data needed for the study, the Bureau of Mines designed and installed, at one of its laboratories, a 6.5-ft-diam. single stage, fixed-bed, air-blown atmospheric pressure gasifier. The gasifier was coupled with a hot, raw gas combustion system and iron ore pellet in. duration kiln. The gasifier is rated at 1.5 ton/h capacity of bituminous coal.

Jan 1, 1987

By Mark P. Juzli

During the 1980s, a revolution has been taking place in industrial minerals marketing. Transportation deregulation and a handful of creative marketing and distribution managers have completely changed the rules for marketing many industrial minerals. Minerals are being transported much farther than in prior decades and at much less cost. Bulk and package terminals are becoming increasingly common as a means to take advantage of freight rate savings and to provide enhanced service to faraway customers. Water and rail transportation are being used increasingly to penetrate markets considered unreachable just a few years ago. No longer do the textbook rules of thumb for industrial minerals marketing apply. This author recalls three of those rules he was taught in mineral economics graduate school in the 1970s. As recorded in class notes: • construction aggregates are seldom shipped more than 32 km (20 miles) from the quarry; • cement is sold within 240 km (150 miles) of the mill; and • industrial sand is sold regionally - it is freight constrained to a market radius of no more than 320 to 400 km (200 to 250 miles) from the plant. And yet, the author looks up in 1989 and observes overland movements of aggregates of many hundred miles, overland movements of cement and industrial sand of 1600 km (1000 miles) or more, and water movements of both aggregates and cement into the United States from sources halfway around the world. Truly, industrial minerals are in the midst of a marketing revolution. The companies that have led this revolution have enjoyed considerable financial success in the 1980s. They have enhanced their profitability by increasing market share, capacity utilization, and average selling prices by taking product to remote markets where premium prices are available. They have consistently outperformed their competition, many of whom remain unaware that the marketing revolution going on around them is actually a transportation/distribution revolution. The successful industrial minerals company of the next 10 to 15 years must participate in the transportation revolution as it continues to evolve. Additional human and capital resources must be committed to maximize the effectiveness of a company's transportation and

Jan 1, 1989

By James M. Barker

Industrial minerals are critical to most aspects of modern society. They are pervasive in both industry and in everyone's lives (McVey, 1989; Barsotti, 1993). They are also the dominant class of minerals produced in the United States but this fact is little known outside the industry. For example, in 1993 (U.S. Bureau of Mines, 1995, table 1) industrial mineral dollar value was double that of metals ($20.86 billion vs. $10.88 billion) and employment levels were nearly so (74,000 vs. 40,000). A further difference is that transportation tends to dominate production costs (FOB end user) whereas they are much less significant in other mining ventures or other industries. Finally, metal mines are more concentrated west of the Mississippi; industrial mineral operations are more prevalent to the east (U.S. Bureau of Mines, 1995, p. 16-17). The significance of transport cost is discussed in Part 2, which is essentially Barker and Austin, 1995. Part 1 will update and expand portions of Barker and Austin (1995) and provide a more detailed discussion of import/export relationships using a China/United States reference point because of China's dramatic influence on some industrial mineral markets since the mid-1980s (barite, etc.).

Jan 1, 1996

By C. A. Heiland

IN the third year of war, geophysical oil exploration broke all records to keep pace with the demand for increased reserves. Geophysical prospecting for strategic and other minerals also grew in scope. The trend of geophysical oil exploration throughout the war is indicated in Fig. 1. This figure resembles the one presented in the last annual review issue of M&M (February 1944, p. 62), corrected for data on-operations in the last months of 1943 and extended into 1944. The average number of geophysical oil prospecting crews in the field in 1944 was 451, whereas the total in 1943 was 340. An upward trend in the use of all geophysical methods is clearly evident throughout the year. Seismic operations were 67 per cent, gravimeter surveys 28 per cent, and other methods 5 per cent of the total. Seismic reflection and refraction crews increased 181/2 per cent over the 1943 average, gravimeter operations increased 73 per cent, and other methods gained 92 per cent. The increase in seismic and gravimeter operations, particularly the latter, is probably due to an increased production of equipment and the organization of new service companies. Miscellaneous methods gained largely through a revival of magnetometer work, and an increase in the use of torsion balances and electrical equipment. In comparison with the prewar average of 1941, it is noteworthy that seismic operations increased 58 per cent, gravimeter operations 88 per cent, and miscellaneous other methods gained as much as 283 per cent. Unfortunately the expansion in the number of geophysical crews does not indicate a proportionate increase in efficiency or in areal coverage, as will be brought out later.

Jan 1, 1945

By T. Hudaverdi

Several studies have been conducted on blastability and prediction of fragmentation. The term blastability is used to refer the susceptibility of the rock to blasting and is closely related to fragmentation. Parameters that determine fragmentation by blasting may be divided into two groups. The first group consists of blasting design parameters. The blast design parameters are controllable parameters and determined by the explosive engineers. The burden, spacing between holes, bench height, drillhole diameter, stemming height and explosive density are all design parameters. The second group consists of rock mass parameters that are referred to as uncontrollable parameters. The uncontrollable parameters are physical and mechanical properties of rock and rock mass structure. The strength, modulus of elasticity, density of rock, number of joint sets, joint orientation and joint spacing are among uncontrollable parameters. The rock mass parameters and blast design parameters should be considered together to explain fragmentation process. In this study, a blast database was accumulated to use for multivariate analysis. The blast database contains the blasts performed near Istanbul region quarries and the blasts that were preformed in various mines in the world by the blasting researchers. The cluster analysis was used to separate the blast data into different similarity groups. Group memberships were analyzed and checked by the discriminant analysis. Then, the multivariate regression analysis was used to develop a prediction equation for blast fragmentation for each group. Finally, a validation of the suggested models was performed for various mines. The model comprises blast design parameters, mechanical properties of rock and rock mass structure.

Jan 1, 2011

By Philemon Desrochers, Ken Qian Liu

Following the success of the West Ore Zone distress mass blast in 2001 at Brunswick Mine, a similar approach was taken to distress the North Regional Pillar (NRP) which contained over 3 million tonnes of high grade ore. The NRP is located on the 1000 m Level with very poor hanging-wall (H/W) rock mass qualities. After an extensive geotechnical review, the distress slot is located close to the foot-wall (F/W) of the NRP in order to have the competent ore as H/W. The longitudinal area to distress covers 115 m along the strike and 85 m high from 1000 1-sub to 850 Sill. Prior to the final mass blast, 3 voids were created to allow rock swelling: the North void, the South void and the trench just below the mass blast. After over one year of preparation, the mass blast of 202,000 tonnes was successfully initiated on February 7, 2003 with 1561 electronic detonators and 210,000 kg of emulsion explosives. The blast achieved its objective of distressing the NRP as indicated the mine-wide micro-seismic monitoring system. This paper describes different stages of the project from void preparation to the mass blast itself, as well as some detailed aspects such as muck-pile prediction for mucking sequence with the help of DMC_Blast simulation code and electronic detonators.

Jan 1, 2004

By Thomas E. Brown

Commercd explosives have evolved through this century f?om dynamite through ANFO to the current lines of Water Gels and Emulsions. Water Gels and Emulsions evolved to counter the lack of water resistance and density of ANFO yet maintain its low cost position verses dynamite. Today, explosives must be safe and inexpensive and perform under a wide range of temperatures, function efficiently in wet or dry boreholes and have a good shelf life. Emulsions meet this criterion, which is why they are the current trend products worldwide.

Jan 1, 1998

By H. P. Cole

A team of researchers at the University of Kentucky, working under a USBM contract, developed over 65 simulation exercises for teaching and testing problem-solving and decision-making skills to miners and mining engineers. These skills involve both improving judgment and decision making in mine emergencies and enhancing the learning of real-world engineering design principles. The exercises are ideally suited for either latent image format or for computer-aided instruction. Exercise features are summarized, the structure and field testing of typical exercises described, and sample frames of individual exercises presented. Empirical data are summarized that describe the effectiveness of using these short, time-efficient performance tasks that simulate real problems and that provide immediate corrective feedback for teaching and testing critical skills. I

Jan 1, 1991

By J. D. Hanawalt

Significant strides were made in the year 1948 leading to further recognition of the place of magnesium as a common commercial metal, rather than as just a premium aircraft material. One of the factors contributing to this recognition was the price stability and, in many cases, price reduction of magnesium products in 1948. In contrast to most other metals, manufacturing advances in magnesium outweighed the effects of increased labor and other costs. At the present time, many magnesium extrusions, die castings, and permanent mold castings can be purchased as cheaply as their aluminum counterparts in these forums, though competitive prices for sheet still await the inauguration of a modern tandem rolling mill for magnesium, such as has already been demonstrated.

Jan 1, 1949

By Bruno Bussière

Le drainage minier acide (DMA) provenant de la circulation des eaux à travers les rejets miniers sulfureux est sans doute le principal problème environnemental auquel est confrontée l?industrie minière. Afin de prévenir les problèmes environnementaux reliés au DMA, on doit restreindre la présence de l?une et/ou de l?autre des principales composantes menant à la production d?acide, soit l?eau, l?air et les sulfures. Pour ce faire, différentes techniques ont été proposées au cours des dernières années, dont la désulfuration environnementale et les couvertures avec effets de barrière capillaire (CEBC). Dans ce papier, on propose d?utiliser ces deux techniques en combinaison. Ainsi, on produirait un rejet désulfuré à l?usine de traitement qui pourrait, par la suite, être utilisé comme matériau pour la couche de rétention d?eau de la CEBC. Dans un premier temps, on présente les résultats d?une étude de laboratoire qui montre qu?il est possible de désulfurer les rejets de concentrateur à l?aide de la flottation non sélective jusqu?à l?obtention d?un résidu non générateur d?acide. Par la suite, des essais en colonne ont permis de démontrer qu?il est possible de limiter la production de DMA d?un résidu sulfureux à l?aide d?une CEBC dont la couche fine est constituée de résidus désulfurés. Des prédictions théoriques estiment même que la présence de sulfures résiduels dans la fraction désulfurée utilisée comme matériau pour la rétention d?eau peut avoir un effet bénéfique en réduisant la migration d?oxygène. En effet, les sulfures contenus dans la couche de rétention d?eau peuvent consommer l?oxygène qui tente de migrer vers le bas et, ainsi, réduire les flux d?oxygène qui atteignent les rejets réactifs.

Nov 1, 2002

By E. S. Longfellow, S. H. Katz

Poisonous hydrocyanic acid gas (HCN) is sometimes evolved in dangerous quantities from cyanides used in metallurgical and chemical operations. This gas is much used for fumigating buildings, ships, greenhouses, and such commodities as grain and cotton to destroy rats, mice and insect pests. Wherever cyanide fumes are evolved, thorough ventilation is necessary in order to render the sur- rounding air safe to breathe. Many persons have been killed by entering tanks and fumigated places too soon, and a simple test for this gas would promote safety. In view of the need for an easy method for quantitatively determining HCN in air, the three color reactions used originally for testing HCN in solution tions *** were modified and adapted. The reactions employ (1) picric acid (CH(NO2)3OH) which is yellow but combines with hydrogen cyanide to form a red- purple dye, isopurpuric acid****; (2) phenolphthalin (CH1604), which is a reduc- tian product of the phenolphthalein (CH4) used for acid indicator, this colorless substance is oxidized***** by presence of HCN to pink colored phenolph- thalin; and (3) guaiacum which oxidized from colorless to blue******. Phenolph- thalin and guaiacum require the presence of copper compounds which catalize the color formation by reduction of cupric cyanide. The chemical processes involved *Associate physical organic chemist, Bureau of Mines, Department of the Interior. **Assistant gas chemist, Bureau of Mines, Department of the Interior. 2014 20 *** Kohn-Abrest, E., Notice toxicologique sur les gas: Arnales des Falsifica- tions, vol. 8, 1915, pp. 215-35. (Tested air with picric acid and guaiacum papers). **** Élasiwietz, H., Ueber eine neue Zersetzungsweise der Trinitrophenylsaure: Anal. der Chemie, vol. 110, 1859, pp. 289-303. ***** Weehuizen, F., Phenolphthalin as reagent for HCN: Pharmaceutrisch weekblad, Utrecht, vol. 42, 1905, pp. 271-2. Abstract, Jour. Chem. Soc., vol. 88, part 2, 1905, p. 489. ****** Schonbein, C. F., Ueber den thatigen Zustand der Helfte des in dem Kupfer- oxydenthaltenen Sauerstoffs und ein darauf beruhendes hochst empfindliches Reagens auf die Blausaure und die loslichen Cyanmetalle: Jour. fur. Praktische Chemie, vol. 106, 1869, pp. 263-70.

Jun 1, 1923

By E. A. Schmidt

In 1962, while investigating the tungsten potential in the Thompson Creek area for Union Carbide Corp., Henry T. Eyrich obtained anomalous concentrations of molybdenum (up to 19 ppm Mo) from stream sediment samples collected along Pat Hughes Creek, a tributary to Thompson Creek. Follow-up investigations by Eyrich during the same year disclosed the presence of a hydrothermally altered and molybdenite-bearing granitic exposure in the headwaters of Pat Hughes Creek about 2.4 km (1.5 miles) upstream from the sample point. The altered outcrop measured about 549 by 305 m (1800 by 1000 ft), contained abundant northwest-trending quartz veins locally with molybdenite, and was overlain and surrounded by the Challis volcanic extrusive sequence of mid-Tertiary age. Eyrich's subsequent soil and rock chip geochemical sampling program over the altered outcrop area showed a general increase in the molybdenum content to the northwest toward the postmineral Challis volcanic cover. Over a distance of about 305 m (1000 ft), values in the altered intrusive rock increased from less than 5 ppm Mo to over 600 ppm Mo, with aconcomitant intensity of the hydrothermal alteration pattern. Based on these geochemical results and on preliminar; megascopic hydrothermal alteration studies, Eyrich correctly concluded that the altered outcrop is an erosional window and that molybdenum mineralization of sufficient grade could exist beneath the Challis volcanic cover some distance further to the northwest. His recommendation to test the area of potential molybdenum mineralization with several drill holes was, however, declined by Union Carbide in 1962. The property remained unclaimed until 1967, when Eyrich joined Cyprus Mines Corp. Acting on Eyrich's recommendation, Cyprus immediately staked 26 lode mining claims to cover not only the altered intrusive outcrop, but also the northwest trend of mineralization where it projected beneath Challis volcanic rocks. Eleven of these claims are now patented.

Jan 1, 1991

By Vince Luongo

PROJECT DESCRIPTION The York Durham Sanitary System (YDSS) Interceptor in the Town of Richmond Hill located just north of Toronto, Ontario, Canada will see the construction of a tunnel extending along 19th Avenue for a length of approximately 3.8 Km from Yonge Street, east to Leslie Street and will have a minimum internal diameter of 2.1 m. t to Leslie Street and will have a minimum internal diameter of 2.1 m. The tunnel will connect into four shafts, for which two of the shafts will be constructed using the slurry wall construction method given the high water table and difficult ground conditions encountered at these locations. The two shafts noted as Access Shaft No. 2 and No. 3 were designed and constructed to meet regulatory conditions, which required a sealed shaft construction method. GEOGRAPHICAL PROFILE The ground conditions in the Toronto region consist predominately of glacial till, glaciolacustrine and glaciofluvial sand, silt and clay deposits, and beach sands and gravels. The shallow geological formation found in the project area consists of four types of deposits: Oak Ridge Morain deposits, Halton Till, Glacial lake deposits and Organic soils. The Oak Ridge Morain is the dominant deposit encountered along the tunnel alignment. This formation consists of three deposits: The Upper Till, Middle Sand and the Lower Till. Standard penetration tests (SPT) carried out in these deposits measured N-values ranging from 2 to more than 100 blows/300mm which indicate very loose to very dense soil conditions. The Middle Sand deposit will be the dominant feature within the slurry wall construction at access shafts 2 and 3. Access Shaft 3 The base of the slurry wall will be 20.5 M below the ground surface. Slurry wall excavation will be within peat and organic soils found at the upper 3 M, followed by 5 M of the Upper Till. The remainder of the excavation will be within the Middle Sand. The piezometric head elevation is found at the ground surface. Access Shaft 2 The base of the slurry wall will be 22.5 M below the ground surface. Slurry wall excavation will be entirely within the Middle Sand 2.The piezometric head elevation is found at 7 M below the ground surface.

Jan 1, 2007

By C. Hsu

Underground coal gasification (UCG) is becoming more popular as the reserves of good quality, mineable coal are starting to diminish, and yet the global energy demand from coal is still increasing. The purpose of this research project was to investigate cavity formation within a coal block due to the combustion reactions in the context of UCG. The cavity plays a pivotal role in the UCG process, as it is essentially the gasification reactor. Cavity formation in an in situ gasification process using the forward combustion linking method (FCL) had been investigated, and a laboratory model was created to simulate the process. The experiment was performed by drilling a U-shaped tunnel into a coal block, which was then combusted internally with air that was fed through an injection hole. A heating element (at approximately 500°C) was used to supply the required heat for combustion at the base of the injection well. The coal blocks were analysed using micro-focus X-ray tomography. The tomography results showed that the coal tended to crack along the bedding plane after a short duration of combustion, due to either the formation of clinker or the expansion of swelling vitrinite along the horizontal tunnel. The deposit was thicker at the base of the injection well compared to the base of the production well; this may have been caused by the turbulence of the air flow and the relatively high oxygen concentration at the base of the injection well. A comparison of the results with work by Daggupati et al. (2010) showed the same trend, despite the slightly different methodology applied.

Jan 1, 2014

By Ray Brainard, Adriana Ventimiglia, Amanda Kerr

Preliminary design is underway for a new Southern Nevada Water Authority (SNWA) project that will ensure one of America’s most reliable water systems by providing continued, reliable water service to existing and future customers. The Horizon Lateral is a $1.6 billion water transmission pipeline that includes 7–10 miles of 108-inch finished diameter rock and soft-ground tunnels. The tunnels will traverse volcanic rock in or around the McCullough Mountain Range and the surrounding alluvial basin. The tunneling community will find relevance in hearing about this critical infrastructure project from a leading wholesale water utility owner with a proven track record for on-time, collaborative projects.

Dec 1, 2022

By The Staff

"THE Wabana iron ore mines, owned and operated by the Dominion Steel and Coal Corporation, Limited, .are on Bell Island in Conception bay, on the east coast of Newfoundland. Mining began on surface in 1895 and, although open-pit work is still done on a small scale, the entire output may be considered to•be derived from extensive submarine workings. In 1958 the average daily production of hematite ore was close to 12,000 tons, almost all of which was concentrated in a heavy-media plant. SUMMARYThe character, occurrence, and extent of the submarine bedded deposits enabled early operators to meet prevailing market demands with the minimum attention paid to exploration. Mechanization of the mine and the pressure for sustained high tonnages since 1955 have emphasized the importance of an expanded exploration and development programme.A serious handicap has been the impossibility of utilizing normal diamond drilling methods to explore ore conditions in advance of mining faces. Drilling between tl1e bedded zones has been done but the major difficulty has been to delineate ore reserves in the lower bed, which has the greatest ore potential of the three mineable seams."

Jan 1, 1960

By D. Malhotra

The economic viability of a mining operation depends on continuous process improvements. Diagnostic testing and plant auditing are essential useful tools to improve performance and reduce operating costs. Case studies are discussed to illustrate benefits of these techniques to improve plant efficiency.

Jan 1, 2001