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By Kirk Ellison, Eric S. Lindquist, Peter Faust, Stephen M. McLandrich

"The 181 Fremont Tower will be an 800-foot high-rise with a 60-foot deep basement located in a dense urban part of downtown San Francisco. The design and construction methods of the subsurface elements navigated a variety of site constraints such as loose fill and soft estuarine soils, shallow groundwater, contaminants, historic obstructions, small work area, proximity of adjacent buildings, and the on-going excavation and build-out of the adjacent Transbay Transit Center (TTC) train box. Design of the approximately 260-foot-deep drilled shafts (some of the deepest foundations ever constructed in San Francisco) was proven by a full-scale load test that provided unique data on the frictional capacity of the deep soil and Franciscan Complex bedrock in the region. Design and construction of the shoring system for the 5-story basement excavation was exceptionally challenging because of the on-going construction for the TTC. To allow for flexibility during construction, hydraulic rams were placed in a transfer waler along the shared TTC shoring wall that could adjust the forces transferred through to the TTC excavation if required. Open and steady communication between the shoring engineer, the geotechnical engineer, and the shoring/foundation contractor was crucial in order to satisfy the complex constraints of this site.INTRODUCTIONThe 181 Fremont Tower is a new build mixed-use tower, currently under construction in the dense urban core of the South of Market District of San Francisco, California. This high-rise will consist of 54 above ground floors with the roof level 700 feet high. Atop the roof will be some architectural features including a spire that will top out at just over 800 feet, which will make it the second tallest building in San Francisco upon completion.The tower is being developed by Jay Paul Company and the architectural design is by Heller Manus. The structural engineer and geotechnical engineer for the project is Arup North America Ltd (Arup). The shoring designer is Brierley Associates (Brierley). The general contractor is Level 10 Construction (Level 10) and the specialty foundation contractor and excavation contractor is Malcolm Drilling Co., Inc (Malcolm)."

Jan 1, 2017

Following a short review of selected literature, a back analysis of stress measurements of stress regeneration in a closed mini-longwall is shown. The agreement is good, lending confidence to the parameters used in the proposed numerical model. Foundation yielding was modelled in the absence of total stope closure. A ?Prandtl? wedge was formed, coinciding with the yield point of the pillar/foundation system. Some theoretical work is used as a starting point for the formulation of a new design methodology for strike or dip stabilizing pillar/foundation systems in deep level goldmines. The existing guideline for the stability of foundations (APS< 2.5UCS) is critically examined. Finally, the advantages of the new approach, and the work required to substantiate the proposed new design methodology, are outlined.

Jan 1, 1998

By Aris Tambunan, Nella Lubis, Nurafrianti Saala, Komang Widhiayanto, Herry Saputra, Rudolf Sitorus

Maximizing mining recovery rates and minimizing ore loss are pivotal objectives for economic efficiency and operational effectiveness. This study explores methods to address these imperatives by enhancing ore production and recovery through improved blasting techniques and spillage control in the Martabe Gold Mine Project in North Sumatra Province, Indonesia. Between 2018 and 2021, the average mining recovery rate stood at 93%, resulting in a potential annual ore loss of 7% and a potential quarterly financial impact of close to $2 million. Maintaining and enhancing mining recovery became crucial, with a planned 30% increase in total material movement for 2022. The mining recovery target for 2022 was set at 96% based on best achievement historical data from 2021 to increase ore tonnage by 203 KTon per annum. To achieve the primary objective of increasing ore production by improving mining recovery, the study focused on predicting and controlling the movement of blasted ore to reduce spillage and enhancing the grade control model to reflect actual conditions post-blasting. Several alternative solutions were explored, primarily emphasizing drilling and blasting activities. Essential methods included capturing the actual blasting movement to adjust the ore block based on blasting design data and post-blasting muckpile topography. This approach minimizes ore loss by providing output as ore block adjustment based on post-blast movement data. In addition, the tie-up design was adjusted to control ore spillage outside the pit ridge. The implementation of these methods yielded significant improvements. Adjusting the ore block based on actual blasting movement contributed $1,545,764 in benefits. Controlling ore spillage outside the pit ridge achieved a 10% reduction in spillage, contributing $79,184 in benefits. These enhancements successfully met the 2022 mining recovery target of 96%, marking a 3% increase from 2021. Consequently, ore loss was reduced by 178 KTon throughout 2022, resulting in a financial impact of $7.3 million. The study underscores the significance of precise blasting techniques and effective spillage control in enhancing mining recovery rates.

Jan 21, 2025

By A Vakili

Dilution is associated with considerable direct and indirect costs in underground open stoping operations. As shown in previous works, an improved ability to predict dilution enables the economic risks associated with unplanned dilution to be reduced. Depending on the width of the orebody and depth of mining, the economic performance of an open stoping operation can become even more sensitive to dilution. It is shown in several well-documented studies that as little as 1 per cent of additional dilution can impose millions of dollars of lost profits per annum. Optimisation of a stoping operation is therefore largely dependent on the ability of the operation to minimise dilution. This can only be achieved through sensible analysis of past and future performance of mined stopes using the most appropriate recent available technologies and tools. This article presents a new design process that utilises advanced geotechnical numerical modelling and various other analytical tools to assist with a more robust mine design of open stoping operations. The focus of this design process is on geotechnical factors affecting dilution during the life-of-mine. A recent application of this optimisation method for a mining operation is presented in this paper as a case study. Through the application of this method and various other operational improvements, the mine was able to deliver more consistent production and lower operating costs over its life-ofmine outlook and was able to reduce dilution by up to 50 per cent and achieve sustainable record high production rates.

Mar 29, 2023

By R. Minto, W. G. Davenport

The slag removed from the reverberatory furnaces of copper smelters contains significant copper values. A serious financial loss is involved, as further recovery operations are not normally carried out. This paper describes the factors affecting physical transport of matte into slag by gas bubbles, and the subsequent entrapment and flotation of matte drops. Three distinct patterns of transport behaviour have been identified from studies of a number of liquid/liquid systems, including liquid metal and liquid matte systems. A theoretical approach is proposed to explain these behaviour patterns, and to predict transport and entrapment behaviour in matte/slag systems. The concepts of "Film Coefficient" (ø) and "Flotation Coefficient" (?) are introduced. The effects of smelting process variables on the physical loss of copper matte in slag are also discussed.

Jan 1, 1972

Detailed mineralogical investigation of a tailing sample from the Juno plant circuit at Tennant Creek was carried out to determine the nature of the unrecovered bismuth and whether any possibility existed for improving bismuth recovery. The investigation showed that the Ibismuth was present in a complex mixture of Bi-Pb-Ou-Se-S minerals (termed &quot;bismuthinite&quot;), of which about 74 per cent was locked (mainly with magnetite) and 26 per cent was liberated (18 per cent in the minus 7 &#181;m slime). The results suggested that attention should be directed to both finer grinding and improved flotation of slime &quot;bismuthinite&quot;, and testwork carried out by Peko Mines N.L. on the basis of these recommendations led to a significant improvement in bismuth recovery.Detailed mineralogical investigation of two Juno concentrates was carried out to determine the nature of the selenium present and whether any possibility existed for improving the selenium grade. The investigation indicated that virtqally all the bismuth, selenium, and lead was present in &quot;bismuthinite&quot;, which showed a composition range of 32-82 per cent Bi, 0-42 per cent Pb, 0-24 per cent Se, and 5-18 per cent S. Differences in the Bi/Se ratios of the two concentrates could be attributed to different average Bi/Se ratios of the constituent &quot;bismuthinite&quot;, and the relatively low selenium grade of the &quot;bismuthinite&quot; precluded the possibility of obtaining a high grade selenium concentrate with high selenium recovery.However, differential flotation and/or low intensity magnetic separation to remove chakopyrite, and magnetite, the main diluents of the concentrate, could be expected to upgrade the selenium content byup to 80 per cent (relative) and .festwork carried out by Peko Mines N.L. on the basis of the recommendations of the mineralogical investigation confirmed that depression of chalcopyrite in the flotation circuit could produce significantly improved selenium grades.These investigations illustrate the application of mineralogy to the practical problems of improving plant performance. Mineralogy has an important role to play in providing quantitative data on which the metallurgist can evaluate plant performance and base a programme of metallurgical testwork, and early mineralogical investigation of feeds, concentrates, middlings, and tailings can lead to the avoidance of much abortive and expensive metallurgical testwork.

Jan 1, 1974

By Natalie Zeleznik, Brian Hawkins, David Bradley, Rachel Gooding, Patrick Wilson

"An Event Tree Analysis (ETA) is an established approach for logically deconstructing and assessing scenarios for probabilistic risk assessment. This deconstruction into a series of understandable eventsfacilitates probability estimation for explicitly defined explosive terrorism scenarios with consideration of modes of possible failure during execution (a scenario is defined through selection of a target, selection of an explosive material, and interdiction prior to arriving at general target location, etc.). Further, each event is decomposed into a range of possible outcomes. The physical action or reality ofthe outcome is statistically represented by “branches” of the event tree (e.g., the terrorist may choose totarget a stadium, hotel, or subway; terrorists may be successful or unsuccessful in acquiring the material)."

Jan 1, 2017

The reactions between molten aluminium and cryoIite have been determined from a material balance of all components involved in the process. The interpretation of results were supported by x-ray diffraction studies of the evolved vapours, quenched electrolyte samples, and side-reaction products.The most important reaction involves the formation of both Na2F (sodium subfluoride) and chiolite in the fused electrolyte. The Na2F accelerates vaporization of the melt. Some AIF (aluminium monofluoride) may also be formed but the proportion of this is much less than for the former subvalent compound.

Jan 1, 1968

By J. E. Friant

Until 1956, drill and blast was the only way to excavate rock. In that year, a tunneling machine using disc type cutters economically bored a small Toronto tunnel. Its amazing 105 ft/day set a new world record and set the stage for a new industry. The Disc Cutter Role in Excavation Mechanical excavation of hard rock is by now deeply ensconced in the heavy civil construction industry. All over the world, from the Swiss Alp Melange to Hong Kong Granite, to New York Gneiss, huge Tunneling Boring Machines (TBMs) create transportation, water and sewer tunnels. Powerful machines, boasting as much as 6000 hp, bore through rock, excavating in excess of 1400 tons per hour. The tool that makes this tunneling phenomenon possible is the single blade, rolling disc cutter. These hardened steel discs, from 15 1/2 to 19 inches diameter are arranged on a rotating cutterhead, to cut concentric circles in the rock. As the machine is propelled forward under great pressure, rock below each cutter is crushed. But the efficiency of the cutterhead is derived from the science of cutter spacing (distance between cutter paths). The majority of the rock excavated is not crushed, but flakes off in chips and chunks. No pick, tooth, or drag type cutting tool can duplicate the performance of a disc cutter. The economic use of drag type tools is limited to as low as 5,000 psi UCS rock strength in massive formations. In weakly bonded, foliated rock, drag tools do better, but are still limited to rock generally less than 15,000 psi.

Jan 1, 2002

By Clarence Hall, CHARLES F. MUNROE

Of the common causes of the larger mine accidents, such as falls of roof and coal, gas and dust explosions, mine fires, and the misuse of explosives, all of which are often closely related, each must be studied and fought in a manner peculiar to itself. The last mentioned, the misuse of black powder and other explosives, is sometimes considered the least important of these causes of mine accidents; but its impor- tance is much greater than the statistics indicate, for the reason that the misuse of explosives is the true cause of many of the fatal mine fires, gas or dust explosions, and falls of roof that are credited to other causes. Both the quantity of explosives used and the number of purposes to which they are applied are increasing. They are now made at about 150 plants, in different parts of the United States, and the product of a single year is estimated at nearly 500,000,000 pounds. Nothing in all this material is a safe or "safety" explosive when in the hands of a careless or ignorant person; and this is true whether considered in connection with the shipment or the use of these explosives. In addition to the large losses of life and property resulting from an improper use of explosives in mining, the recent statistics of the railway bureau for the safe transportation of explo- sives have shown more than 400 persons killed or injured and over $3,000,000 worth of property destroyed by explosives in transit by rail. The fact that three years of cooperative effort under the wise supervision of this bureau has reduced these losses to almost nothing encourages the hope that similar cooperative effort may likewise greatly lessen losses of life and property from the use of explosives in mining. The additions to the large death roll of our mines make a recurring appeal to the public for fair treatment of the coal-mining industry, and to the miner and the manager that they join in every possible effort for greater safety. It may never be possible under conditions such as exist to-day to prevent mine accidents entirely. Little can be accomplished in that direction by either the operators or the miners working alone, but experience in all countries shows that

Jan 1, 1911

By Haigh J. E

An accurate measure of the earth&apos;s magnetic field can be made in a few seconds with the portable proton precession magnetometer. Such an instrument increases the applicability of the long successful method of magnetic prospecting for minerals. As an example of the usefulness of the proton magnetometer, a survey over volcanic rocks near Apsley (Tas.) was made.INTRODUCTIONA completely portable magnetometer whose operation is based on the free precession of polarized protons in the earth&apos;s magnetic field, is now available on the market at a price competitive with magnetometers based on the classical physical principles. The ease, accuracy, rapidity, and reliability with which measurements of the earth&apos;s total magnetic field can be made with the proton precession magnetometer, led to the try-out of the instrument in an actual field problem so as to evaluate fully the capabilities of the instrument. Such evaluation is important, because the history of magnetic prospecting has shown that whenever significantly improved instrumentation has been introduced, prospecting costs have been substantially cut and many areas in which the prospecting costs were formerly considered excessive in relation to probable returns, have become economic mineral prospects. The proton precession magnetometer offers the possibility of opening up new areas for successful magnetic prospecting.AN OUTLINE OF THE HISTORY OF MAGNETIC PROSPECTINGWhile an outline of the history of magnetic prospecting is not directly connected with the evaluation of a proton pre...

Jan 1, 1963

By H M. Parker, G Verly, T Postolski

Assessing the uncertainty and risk in mineral resource estimation is required for best practice and is implied by the public reporting codes in the categorisation of mineral resources and reserves. One industry best practice is quantifying the risk on future production for a given period, which can be done using two geostatistical approaches: conditional simulation and drill hole spacing studies based on estimation variances. Conditional simulation can provide a more complete and flexible answer to the problem, but it takes a fair amount of time to complete. Drill hole spacing studies are simpler, faster and can provide reasonable assessments of mineral resource uncertainty.This paper is a presentation of the principles, theory and practice of drill hole spacing studies. Various types of risk assessment are considered. Difficulties encountered in practice are discussed, and solutions are proposed. The important parameters impacting the results are reviewed. Examples of results and sensitivities are shown.CITATION:Verly, G, Postolski, T and Parker, H M, 2014. Assessing uncertainty with drill hole spacing studies – applications to mineral resources, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 109–118 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By K. E. Waters, N. Brodusch, R. Gauvin, H. Demers

"Rare earth elements are becoming increasingly in demand, due to their prevalence in both renewable energy devices and high-end electronics. The characterization of the composition, morphology and volume fraction of the various phases that have valuable rare earths in the ores are needed to find the optimal industrial process to extract the ores containing the rare earths. Rare earth-bearing minerals contain many elements with the M-and L-lines overlap, requiring a high degree of resolution, pushing the boundaries of scanning electron microscopy quantitative analysis. Enhanced microscopy at a high spatial resolution with improved x-ray quantitative analysis enables the accurate determination of the distribution of the desired rare earths in various mineral phases. INTRODUCTIONRare earth elements are becoming increasingly in demand, due to their prevalence in both renewable energy devices and high-end electronics. From batteries (lanthanum and cerium), to magnets (dysprosium and neodymium) and lighting (yttrium), the rare earth elements are crucial to the advancement of technology, and to energy saving devices (Crow, 2011). The goal of this project is to characterize the composition, morphology and volume fraction of the various phases that have valuable rare earths in the ores in order to estimate the economical VALUES (of the ores and to find the optimal industrial process to extract the ores containing the rare earths. High spatial resolution imaging and x-ray microanalysis are needed to reach this goal. In this work, the results obtained with a cold-field-emission scanning electron microscope (FE-SEM) and a silicon drift detector (SDD) energy dispersive spectrometry (EDS) detector at low accelerating voltage are compared to experimental conditions typically used with electron probe microanalysis (EPMA) instrument.With this improvement, a detailed scientific analysis of the composition of these, and other, ores will become possible with a SEM/EDS system. This will help to better understand how such ores were formed, hence assisting in finding them, and to better understand how to process them in preparation for high end industrial applications, namely through mineral processing."

Jan 1, 2012

By P M. Dight

Shotcrete usage in declines and developments has become pervasive as operators strive to achieve production improvements. Issues of mix control, fibreload, thickness control, temperature and curing conditions all play a part in the quality control. Often to overcome some of the quality control issues designers over specify the strength requirements in order to meet their operational constraints. Adherence to the standard civil testing requirements of 28 days moist cured at 21ºC without properly calibrating these results to the changing environment underground leads to contractual disputes. There are a number of standard tests specified including cylinder tests, cored tests, beam tests and round determinate panel (RDP) panel tests. The logistics of storing these samples and then transporting them to concrete testing laboratories without due regard to temperature changes with time can influence the results. All the samples can be readily handled by personnel except the RDP panel. The standard RDP panel is 800 mm diameter by 75 mm thick and requires an ITH machine at the mine and a fork lift at the laboratory to move it around. This paper will examine the possibility of a panel which provides scalable results to the standard RDP panel but can be easily handled by personnel and/or tested on site with suitable equipment. This allows for faster turn around and better quality control for the sample prior to testing. This enhances the identification of quality control issues at the mine and improves safety.

Mar 21, 2011

By Caitlin Rogers

The environmental and economic sustainability of froth flotation is dependent on effective management, which in turn improves the performance of a concentrator. In economic terms this means improved recovery of valuable minerals, in environmental terms this means effective management of acid generating tailings. Three indicators were selected to measure the performance of an integrated flotation system. The system consists of two stages of flotation; valuable mineral flotation followed by environmental desulfurisation by froth flotation. The suitable indicators were selected based on their fulfilment of four attributes. An attribute is a desired aspect of an indicator. The four attributes were: comprehensive, relevant, sensitive and quantitative. Two environmental indicators and one economic indicator were selected. They represent revenue generation from valuable minerals and environmental cost of management. The suitability of the selected indicators was shown using illustrative scenarios.

Jan 1, 2014

By Joe N. Magee

As part of the important program of promoting conservation and efficient utilization of petroleum, Bureau of Mines engineers are making studies of secondary oil-recovery projects throughout the United states and publishing reports setting forth the pertinent facts so that others may profit by the experience gained. This report presents the results of a study by engineers of the Bureau of Mines, stationed at Franklin, Pa., of secondary oil recovery in a part of the Cabin Creek field, Kanawha and Boone Counties, W. Va., where natural gas is injected into the reservoir to stimulate oil production. Most oil produced in the Appalachian region at present is obtained from stripper fields in which almost all natural energy has been dissipated. Secondary-recovery methods are used extensively in many oil-producing areas of New York, Pennsylvania, West Virginia, Ohio, and Kentucky for recovering oil not produced by primary-production methods. The part of the Cabin Creek field reported in this study is shown in figure 1 and has been designated by the operator as project 4. In 1944 the developed area of the entire field was approximately 4,200 acres, and the area of project 4 was about 600 acres. In the developed area of the project the oil reservoir is in the Berea sandstone and occurs at 2,914 to 3,410 feet.

Jan 1, 1952

By James S. Graham

Specifications for treated round wood piling are presented for the engineers consideration. Included in the text are background information, technical committees, Chellis, quality, treatment, static and dynamic stresses, accessories, and existing codes and standards. The specifications are also available using Word Perfect on 3.5 or 5.25 inch size disks provided by the National Timber Piling Council. Note: DFI recommended wording is wood, head, and toe, instead of timber, butt, and tip.

Jan 1, 1992

By E. H. Bunce

CONTINUED progress in zinc metallurgy has been shown during 1933 by the adoption of new methods as well as the modernization of old processes and equipment, and by the initiation of new fields of activity for future advancement. The use of suspension roasting continued to grow as its advantages and adaptability became increasingly, apparent. The process developed by the National Smelting Co., Ltd., several years ago, of completely roasting on large sintering machines with utilization of the gas for acid manufacture has worked so successfully that an additional machine was installed during the year. At both the Swansea and the Avonmouth Works all of the ore for smelting is now roasted on the large sintering machines, thereby completely eliminating the old hearth-roasting furnaces. Work continued on obtaining partial purification of zinc ores from lead and cadmium by close control of conditions on the sintering machine, and in a few instances by chlorine additions to the ore before sintering. Ores so treated were either partially roasted or com-

Jan 1, 1934

The National Institute for Occupational Safety and Health (NIOSH) has continued study of the Personal Dust Monitor (PDM) developed by Rupprecht & Patashnick Co. Inc. through a CDC contract and currently being commercialized by Thermo Fisher Scientific. This report examines the effect of oversize particles, cyclone inversion, and cleaning procedures. Clean and exposed filters were examined using light microscopy and particulates counted before and after various instrument manipulations. The data presented show that the dry cleaning procedures do not cause significant (greater than limit of detection) sample contamination by respirable or oversize particulates and that the cyclone is resistant to particulate carry over during inversion.

Jan 1, 2009

By B. Hearn, Malcolm J. McPhersqn

Since 1993 Inco Ltd. has been using wet shotcrete at Stobie Mine. Through an evolving process the mine has reduced the thickness and fiber content of its steel fiber reinforced (sfr) shotcrete. However, the shotcrete support is used without any other type of ground support. A process referred to as bolt less shotcrete. Boltless shotcrete is used as the primary ground support method in development headings when the sub level caving front passes through the development drifts which now serve as migrating ore draw points. Although there are references of drifts and tunnels supported by shortcrete only, written accounts are rare. The empirical nature of most underground support designs makes them of limited value in a boltless environment. Considerable amounts of material testing and insitu trials have been completed in order to estimate material property strengths. Material testing, for adhesion, flexural strengths and compressive strength along with observational insitu data have been used to evaluate the performance of shotcrete. Punch tests on panels have also been undertaken in order to gain insights on the limitations of the two dimensional testing common to the laboratory. All these design aspects have been successfully utilized to design an efficient ground support process.

Jan 1, 1998