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By F. P. Schwarz

Even in an otherwise care-fully done sampling procedure, reducing subsample weight, or splitting, when the grain size of material is too large commonly generates significant error. Such error can be estimated from the standard deviation of differences between values of PAIRED ASSAYS. Samples from split-ting steps immediately before comminution, and showing a restricted range of grade, generate paired assays. Splitting steps characterized by relative standard deviations exceeding 16% generate nonrepresentative data. Such steps should be redesigned to optimize reliability of assay-dependent studies. A sampling scheme can be graphically characterized, and then redesigned as appropriate, using a SAMPLING NOMOGRAPH. Use of the nomograph avoids continued replication of assays. Generally at a splitting step, excessive error can be reduced by comminuting more material. Unnecessary effort can be mitigated by comminuting less finely and/or by splitting to a smaller weight.

Jan 1, 1992

By Ginger L. Hustrulid

Conveyor belts are a critical component in tunneling projects. This paper reviews current design considerations for conveyor belts. Rubber compounding differences to meet local fire resistance regulations or certain cover characteristics such as higher abrasion resistance or low carbon footprint rubbers for applications are reviewed. Evaluation of fabric belts, steel cable belts and the benefits of each carcass design for a particular use is also examined to help with proper carcass selection to decrease downtime from unexpected failures. Finally, this paper takes a look at some of the differences when working in metric versus imperial units.

Dec 1, 2022

By Justin Kolster, Donald Benjamin, Kyle White

Expansion of the Plum Island Wastewater Treatment Plant requires interconnection of three operating pump stations using only two existing 10-ft diameter shafts for access. These two existing shafts require additional support to allow access 130 feet below grade. Interconnection requires rehabilitation of an existing tunnel, excavation of two new tunnels, and abandonment of additional existing tunnels. Construction has discovered unexpected conditions at all three connection points. The CMAR contracting method has effectively accommodated project team discussion, value engineering decisions, and allocation of risk during preconstruction and construction phase services.

Dec 1, 2022

By James A. Clem

Approximately 2,000 years ago, the Lord Admonished the Scribes (Lawyers) and Pharisees (Religious leaders of that time) that they had paid the tithe but had omitted the weightier matters of law, Judgement, Mercy, and Faith. (Matt. 23:23). I want to talk about "The Weightier Matters of Law." In a situation where big government is trying to have an effect on even small details of a work activity, otherwise simple situations become complex. Regulations are written to such detail that constant compliance with strict interpretations can be a nightmare--not to mention off the target of the intended purpose for the regulation. One soon re- cognizes the oneros characteristics of Federal statues

Jan 1, 1979

By Francesco Chiappalone, Franco Gasperin, Fabrizio Fara

This document describes the challenging task of mining through tiebacks using a 21'-8" diameter Tunnel Boring Machine (TBM) as part of the Ship Canal Water Quality Project. The mining operation involves navigating through 17 tie-backs that are evenly spaced at 8-foot intervals, with many intersecting the full face of the cutterhead. Detailed analysis and review of TBM parameters specific to this area have been conducted to ensure operational efficiency and safety. Hyperbaric interventions have been planned and coordinated, encompassing pre-mining preparations, continuous monitoring and adjustments during the mining process, as well as post-mining measures. The document highlights the complexity and importance of strategic planning and execution to successfully overcome the tie-back intersections during the mining operation.

Jun 23, 2024

By Dan Ifrim, Andre Solecki

Tunneling could be a major challenge to tunneling contractors as tunneling operations can be seriously affected by the Tunnel Boring Machine (TBM) performance. Specifying the appropriate TBM methodology, selection of systems and features, is critical for managing tunnel risks and contribute to successful tunneling project. The paper analyzes tunneling records from the recently completed City of Toronto’s Ashbridges Bay Treatment Outfall tunnel project and underlines the righteous selection of the TBM type and associated TBM systems in achieving good advance rates during tunnelling and managing project risks. The paper intends to draw attention of a few aspects of TBM technical specification importance and highlight the lessons learned from this process.

Jun 13, 2023

By Sam Rosenblum

The anomaly ratio is obtained by dividing the analyzed value of an element by the anomaly threshold value of the element. The sum of anomaly ratios for all anomalous elements in a sample may be compared with similar sums for other samples, so that the samples having the greatest anomaly-ratio totals can be recognized easily. In partial or full-suites-of-ore-elements the use of anomaly ratios is more meaningful than analyzed values because the ratios quickly indicate anomalous elements and call attention to samples and localities that should be investigated.

Jan 1, 1980

By Ivan V. Klumpar

If components of a gas-liquid stream react with each other and with stationary solids, involving parallel and sequential, reversible and irreversible, and slow and instantaneous reactions, the process can be defined by a set of simultaneous differential rate equations and simulated as multistage semibatch re¬actors. Each stage is divided into finite time increments. Within each increment, even the simultaneous reactions are treated as sequential. The proposed method follows process evolution from non-steady state startup to normal operating conditions. It allows computing byproduct buildup in recycles, tracer response curves and, in case of underground processes, expansion to adjacent parts of the deposit.

Jan 1, 1979

By James K. Kindig

Hazen Research, Inc., has developed a new process for removing pyritic sulfur and ash from coal. Feed coal is contacted with iron carbonyl vapors, Fe(CO)5, at 190°C which puts a thin skin of magnetic material on the pyrite and ash, but does not affect the coal. Thus, low intensity magnetic separators yield a nonmagnetic coal, low in sulfur and ash, and a magnetic refuse, high in sulfur and ash. Results are given for clean coal produced by this method. A comparison is made between results of the magnetic process and the U. S. Bureau of Mines two-stage flotation process cleaning identical samples of Pittsburgh Coal. Capital and operating costs of the two cleaning methods are discussed.

Jan 1, 1976

By Robert C. Maxton

The foundry industry is a basic source of structural component for all industry. Millions of tons of castings are produced annually in both ferrous and nonferrous alloys. These castings are subjected to a wide variety of heat treatments, finishing techniques, mechanical tests and machining operations. Through all of these steps the quality of the casting is of paramount importance to the end use of the product. The Quality Assurance Program at Minneapolis Electric Steel Castings Company is designed and established to provide a superior product for both original equipment manufacturers and the mining industry.

Jan 1, 1982

By Thomas H. Dubaniewicz

(XP) enclosures to enclose electrical ignition sources to prevent propagation of an internal methane-air explosion to a surrounding explosive atmosphere. Researchers at the National Institute for Occupational Safety and Health (NIOSH) conducted a lithium-ion battery thermal runaway test within a modified MSHA-approved XP enclosure to assess thermal runaway containment. Thermal runaway produced jet flames emanating from the cover joint at several locations and distorted the cover joint and bottom plate of the enclosure beyond allowable limits. The test demonstrates that XP enclosures may not provide adequate explosion protection against lithium-ion battery thermal runaway. This paper suggests some approaches to mitigate the hazard.

Feb 1, 2024

By Jeffrey Peterson, John Beesley, Martino Scialpi, John Cassidy

The DC Clean Rivers Project is DC Water's ongoing program to capture and treat combined sewer overflows (CSOs) during rainfall before they reach the District waterways. The Anacostia River system was designed to reduce CSOs into the Anacostia River and includes the Blue Plains Tunnel, Anacostia River Tunnel, First Street Tunnel, and Northeast Boundary Tunnel. A portion of the Anacostia River system was commissioned in March 2018 and the final component, the Northeast Boundary Tunnel, was placed in operation on September 15, 2023. This paper provides a summary of the experience gained during construction of this +$2.9 billion project, an overview of the system performance since its activation in 2018, and a look-ahead to the next phase of the DC Clean Rivers program: the Potomac River Tunnel.

Jun 23, 2024

By Robert T. Chapman

Many of us are privileged in that we have witnessed the transition from mining methods used in the first quarter of the twentieth' century to those practiced today. In the late Twenties, for example, many mines still used hand mucking methods. In the middle Thirties, more than one large metallurgical limestone quarry still used the 4 cubic yard railway steam shovel formerly in use at the Panama Canal. Mules could occasionally still be found underground, where they provided the-main-source of motive power. Within the last decade, and even within the past five years or less, great improvements have been made in blast-hole drilling, ore loading, and ore hauling equipment. Industrial demand for minerals can be expressed in exponential terms as compared to that at the turn of the century. Even marine mineral resources are receiving accelerated attention. One overall result is that larger and lower grade orebodies can be exploited at a profit. This profit must be made despite, for example, a static monetary price for gold, and despite the continual cost escalation involving labor, materials, supplies, and equipment. Accordingly, the application of the necessary degree of knowledge and judgment required to meet production, cost, and profit goals is paramount.

Jan 1, 1966

By J. R. Patts, A. B. Cecala, E. J. Haas

Exposure to respirable crystalline silica (RCS) remains a serious health hazard to the US mining workforce who are potentially exposed as various ore bodies are drilled, blasted, hauled by truck, crushed, screened, and transported to their destinations. The current Mine Safety and Health Administration (MSHA) permissible exposure limit (PEL) for RCS remains at approximately 100 μg/m3 , but it is noteworthy that the Occupational Safety and Health Administration (OSHA) has lowered its PEL to 50 μg/ m3 (with enforcement dates staggered through 2022 for various sectors), and the National Institute for Occupational Safety and Health (NIOSH) has held a 50 μg/m3 recommended standard since 1976. To examine a method for reducing RCS exposure using a NIOSH-developed video exposure monitoring (VEM) technology (referred to as Helmet-CAM), video and respirable dust concentration data were collected on eighty miners across seven unique mining sites. The data was then collated and partitioned using a thresholding scheme to determine exposures that were in excess of ten times the mean exposure for that worker. Focusing on these short duration, high magnitude exposures can provide insight to implement controls and interventions that can dramatically lower the employee’s overall average exposure. In 19 of the 80 cases analyzed, it was found that exposure could be significantly lowered by 20% or more by reducing exposures that occur during just 10 min of work per 8-hour shift. This approach provides a method to quickly analyze and determine which activities are creating the greatest health concerns. In most cases, once identified, focused control technologies or behavioral modifications can be applied to those tasks.

By Gary Brierley, Lok Home

"The majority of tunnels for civil engineering applications are now being constructed using some form of mechanical excavation. Beginning in the 1960s with rock tunnel boring machines (TBM), the tunneling industry has introduced both earth pressure balance (EPB) and slurry pressure balance (SPB) soil machines; mixed soil and rock machines and a variety of different mechanical devices for the construction of small diameter tunnels. Over time, these machines have become more powerful and more adaptable to a wider variety of ground conditions; so much so that tunnels are now being constructed in ground conditions and in the vicinity of third-party impacts that would have been considered beyond the state of the art just 10 years ago. Figure 1 is an example of a mixed ground crossover TBM used successfully at Mexico City’s Túnel Emisor Poniente II.All of the above is highly advantageous for the tunneling industry, but it has also placed a much higher level of risk on the performance characteristics of the tunneling machines, on the contractors operating those TBMs and on the manufacturers of those machines. Most of the risks for a tunneling project are associated with creating the space inside of which the finished facility will be constructed. In order to create that space, the tunnel contractor must make many decisions about the best way to excavate the ground, the best way to control the ground at the face of excavation and the preferred method for supporting the ground around the tunnel in a manner that is safe for the workers and stable with respect to all of the overlying and adjacent existing structures. If it is proposed to use some form of TBM in order to build the tunnel, then the TBM becomes central to all three of these activities and becomes an integral part of managing the risks associated with these activities."

Jan 9, 2018

By Joel L. Morrison

Wet bituminous coal fines from active and abandoned slurry impoundments are currently being examined as a recoverable feedstock for the production of coal water slurry fuel (CWSF). Preliminary analysis indicates that these coal fines can be converted into low solids, low viscosity CWSF with acceptable stability without the use of viscosity modifiers (dispersants) or stabilizers. Efforts are now underway to determine if the impounded coal fines can be economically cleaned by froth flotation to an ash level of < 12 wt. % and a total sulfur content of 1.2 wt. %.

Jan 1, 1995

By H. Kimura

A new technology for ironmaking based on direct gaseous reduction of iron ore concentrate is under development. The process is based on the flash reduction of the concentrate particles in a gaseous reducing agent, such as hydrogen, natural gas, a reducing gas generated by partial combustion of coal, or a combination thereof. This technology is expected to drastically lower CO2 emission and reduce energy consumption by about 38% of the blast furnace requirements. The energy savings are possible largely due to the elimination of pelletization and cokemaking. Process design and simulation using hydrogen as the reductant for iron ore concentrate have been performed. A process flow sheet composed of a flash reactor, heat recovery system, water removal system for purifying recycled hydrogen, and all connecting streams was evaluated using the METSIM software. Ironmaking using two reactors was also designed and simulated, which could reduce the total required amount of hydrogen although it would increase the complexity of the flow sheet and operation.

Jan 1, 2010

By J. M. Goris

The U.S. Bureau of Mines, in cooperation with the Homestake Mining Co., and the University of Utah, is conducting a field demonstration to evaluate the behavior of rock masses supported with cable bolts. One of two rock masses being studied is supported with both conventional and birdcage cables. This rock mass is located between the 6500 and 6650 levels of the 45-4BN stope. 21 ledge. The second rock mass is the hanging wall of the D-limb stope between the 3500 and 3650 levels near the Ross Shaft and is supported with conventional cables. The primary objectives of the project are to monitor the behavior of the two rock masses during mining using extensometers and cable support strain gauges, after which the rock will be modeled using the finite-element code UTAH III. Field data will be used to verify the modeling. In addition. a comparison between the effectiveness of conventional and birdcage cables will be made.

Jan 1, 1991

By James E. Jones

The coal mining industry is being called upon to vastly increase production in the coming years. Many mining operations will have to prepare an environmental impact report of some kind and all will have to comply with various types of environ- mental regulations. Therefore there is a great need within the industry for access to environmental data, information, and literature. This paper discusses the informational resources available, the current lack of access to these resources, and the Environmental Data, Information and Literature (EDIL) Bank of the Kentucky Institute for Mining and Minerals Research. The bank&apos;s major emphasis concerns the environmental, social and economic aspects of producing clean solid, liquid, and gaseous fuels from coal. The data bank promotes information interchange between other related governmental and private projects and the energy development community.

Jan 1, 1976

By K. P. Wang, Ta M. Li

The Chinese energy and mineral industries are readying themselves for a period of dynamic transition, unprecedented in the country&apos;s long and sometimes turbulent history. The transition comes as a result of the government&apos;s new program of "Four Modernizations" in its agricultural, defense, industry, and science and technology sectors. The announced program is generally considered by Western observers to be a moderate, pragmatic approach to get China on the road to industrial parity with Western nations by the year 2000. The game plan calls for integration with the West to beef up Chinese know-how and the purchase of foreign technology to supplement areas where China lacks the ability to do so itself. While the role of energy and minerals is not specifically mentioned in the program, it was made clear to ME that China realizes the basis of any sustained modernization program is tied closely to the health of its minerals sector. Various published reports have indicated the existence of an already vibrant energy and minerals sector with world rank production in coal, iron ore, tin, antimony, cement, pyrite, asbestos and tungsten to name just a few. For the most part, except for the export metals, the primary focus of China&apos;s production has been on fulfilling domestic needs. Now the new initiatives are aimed not only at self-sufficiency, but also on propelling the country&apos;s natural resource clout into international prominence. With a mineral resource base that is considered by many westerners a potential bonanza, China&apos;s new long march toward modernization will be an exciting adventure, well worth watching. Big Projects Spark Excitement China&apos;s renewed commitment to a more liberal program is as much a desire to "walk on its own two legs" as it is a backlash from the frustrating years that followed the Cultural Revolution of the 1960s and early 1970s. Much of the early excitement was initiated by China&apos;s Premier and Party Chairman Hua Guo-feng in speaking to the fifth National People&apos;s Congress (NPC) in 1978. Here, Chairman Hua presented the Communist Party&apos;s 10-year blueprint for economic development. Specifically, the Party&apos;s plans called for completion of 120 large-scale industrial projects by 1985. Mentioned were 10 new iron and steel works, 30 power plants, six new railways, 10 oil and gas fields, nine nonferrous metal

Jan 3, 1980