Search Documents

By Glenn Boyce, Paul Gribbon, Gary Irwin, Greg Colzani, Jim McDonald

This paper discusses the process utilized by the City of Portland Oregon’s Bureau of Environmental Services (BES) to procure and compensate Impregilo-SA Healy (I/H)for the West Side Willamette River Combined Sewer Over?ow (CSO) Project. The contract method is a three-phase process consisting of qualifications based contractor procurement, pre-construction phase design assistance/construction planning, and facility construction where the contractor is compensated on a cost reimbursable-fixed fee basis. The paper focuses on pre-construction phase lessons learned from the development of the contract general conditions, establishment of a construction budget and cost control program, incorporation of contractor recommended design changes, and development of a subcontractor procurement program for construction.

Jan 1, 2003

By Ronald D. Hill

The occurrence of acid mine Drainage (AMD) with coal mining has been well documented. (1) Less documentation is available of its association with other types of mining, e.g., copper, gold, zinc, and sulfur. Yet there are many locations in the western states where acid mine drainage is as great a pollution problem as in Appalachia and in some cases, because of the high copper, zinc, and arsenic concentrations, they present an even more difficult problem. Until a few years ago, it was generally believed that the neutralization of acid mine drainage was uneconomical thus, AMD was allowed to discharge freely into our streams. However, the demand for good water finally dictated that the mining industry be included under pollution laws. In 1964 the Commonwealth of Pennsylvania passed a law requiring that all active mine discharges meet a discharge standard of pH 6-9, iron less than 7 mg/1, and the water must have a net alkalinity. Several other states now require active mines to treat AMD. In all but a few cases, lime neutralization, often in conjunction with aeration, has been the treatment method used. The high cost of lime as compared to limestone and the poor quality sludge, (slow settling, large volumes, and low solids content) has stimulated work in the utilization of limestone. This paper reports on the current state-of-the-art of limestone treatment of AMD.

Jan 1, 1970

By J. Holmes Armstead, John L. Dobra

This paper examines some lesser known risks in foreign investment by U.S. companies that derive from international judicial activism by U.S. courts and the potential for extending U.S. anti-trust regulations to companies' foreign operations. The discussion of international judicial activism reviews the implications of the U.S. Second Circuit Court's ruling in the Union Carbide/Bhopal case for U.S. companies investing abroad and the discussion of extending U.S. anti-trust regulations focuses on proposals coming out the Clinton administration's Justice Department.

Jan 1, 1996

By J. Perlacia, J. M. Eguiluz

"INTRODUCTION The Bulk Handling Technology has suffered an important development in the recent years, allowing the use of conveyor belts in the most important and critical applications. As a consequence of this, the reliability and lasting performance of the conveyor belt components is becoming more and more significant, thus the implementation of preventive maintenance programs is a must. The rollers are one of the consumables in the conveyor belts, which have to be changed once arrived to the end of life. The actual ways of detecting this moment always require intensive use of labour and they are not very accurate. Indeed, if the rollers get broken before replacement, the consequences could be very important, generating additional costs and operational losses. The R&D Department of ULMA Conveyor Components, has been working since early 2012 on the development of Monitored Rollers along with a Management Software to provide users the capacity to Manage and Monitor the rollers from its desk, getting continuous online information on the internal temperature of the bearings, on the working status of the rollers as well as the identification of the rollers close to their end of life so that they could be changed during the next maintenance stop of the conveyor belt. In short, a system of Preventive Maintenance for Conveyor Belt Rollers BACKGROUND AND CURRENT STATE The malfunction of a single roller in certain conveyor belts can suppose the standstill of the whole installation until its replacement, due to the risk of greater and more expensive failures like the rip of the belt. In the case of a bulk handling installation where a continuous supply of material is necessary, a bare stop of one hour could entail huge economical losses. What’s more, many conveyor belts are several kilometers length or the access to some parts of them is very complicated. Due to these difficulties the inspection and maintenance operations can become expensive and hard going, with staff going over the whole area checking the correct condition of the conveyor and rollers, which means a dangerous activity. In addition, it’s quite common to find rollers working in very harsh conditions, completely exposed to the elements or working in corrosive closed environments like underground mines. These tough working conditions together with the very demanding features of Bulk Handling sector (high loads, speed, dangerous materials etc.) can bring the unexpected failure of a roller, even being designed to support them. Thus, to have the working conditions of the rollers real time is clearly required, in order to achieve an actual predictive maintenance of the system and avoid fatal failures. Nowadays the most common procedures to identify a broken roller is to hear how it sounds or use thermo-graphic cameras to measure their internal temperature, both of them implying workers inspecting the whole length of the conveyor while the conveyor is running. This means intense use of workmanship and operational safety level reduction."

Jan 1, 2018

By Vanessa M. Torres

Diagnostic leaching tests provide a good indication of gold deportation in its various occurrence phases. With the results of these tests, possible flowsheets for difficult ore treatment can be established for further evaluation and plant operation can be optimized. The use of this technique can be extended, including heap leach evaluation and complex copper-gold ores. The results on the use of diagnostic leaching tests in gold ores from Companhia Vale do Rio Doce (CVRD) are presented and discussed, as well as the methodology to select steps and interpret results used at CVRD Technology Center (Sutec).

Jan 1, 1998

By Hongjie Yu, Mike Mooney

Transitions between geological/geotechnical soil units have a critical impact on the operation and performance of a tunnel boring machine (TBM). Geostatistics-based probabilistic modeling is used to quantify the uncertainty in soil transition locations. This paper presents two unique soft-ground tunneling case studies where the results from the geostatistics-based probabilistic modeling are compared to the TBM data and as-encountered ground conditions derived from the actual TBM data. The assessment enhances the confidence in using geostatistics to improve ground awareness for efficient tunnel construction, minimizing different site condition (DSC) claims, and improving decision-making on tunnel projects.

Dec 1, 2022

By R. J. Sandberg

The Copper Creek area, part of the Bunker Hill District, Pinal County, Arizona, lies within the southwest porphyry copper province of North America at the intersection of a northwest trend and an east-northeast trend of Laramide porphyry copper deposits. The Copper Creek area has been mined and explored for copper and molybdenum since the early 1900?s. The majority of this work focused on the more than 400 surface exposed breccia bodies. In the 1960 to 1970?s deeper drilling discovered a deep porphyry copper-like setting. Redhawk Copper currently has NI 43-101 compliant resources of about 0.652 billion pounds of measured and indicated and 2.745 billion pounds of inferred copper equivalent in breccia hosted and porphyry style deposits. See Figure 1.

Jan 1, 2010

By Ralph A. MacMillan

Electronic systems introduced for haulage equipment in recent years probably exceed what mine management is prepared to use. Haulpak trucks alone are equipped with General Electric's Statex III drive system controls, Detroit Diesel's DDEC, Cummins' Centry engine management system and the Haulpak Management System (HMS). The future holds promising developments of even more sophisticated electronics that will lead to unmanned truck operation and control. Trolley-assist will finally come into its own due to the importance of environmental issues, as well as the high potential for increased productivity with dramatically lowerfuel consumption. All of these high technology systems do not mean much unless they add value to mining operations. Some of the benefits that can be expected from these systems are reviewed. In the near future, haul truck control and monitoring systems will be fully linked by telemetry to a mine's dispatch system, as well as to its maintenance management information system. The manufacturer and distributor can also be kept in the communications loop, so that they can better serve customer needs. Portable computers will allow technicians to talk to machine systems to quickly locate a problem, look up service information, check what parts are required and electronically order them.

Jan 1, 1994

By M. J. DeJong, R. J. Mair, S. Ritter, G. Giardina

"For urban tunneling projects it is essential to predict and prevent building damage. Although various case studies and experiments have shown that buildings considerably modify greenfield soil movements, widely accepted damage assessment methods neglect this soil-structure interaction and simplify structures as linear elastic beams. This paper summarizes an experimental investigation of the response of more realistic structures to tunneling-induced deformations. Small scale structural models with façade openings and brittle material properties were 3D printed and tested in a geotechnical centrifuge. Soil and structure displacement data were obtained by image-based measurement. Results demonstrate that structures notably mitigate differential greenfield ground displacements. It is also shown that maximum soil settlements, horizontal soil displacements beneath the structure and structural damage in the form of cracking significantly depend on the position of the structure in the settlement profile. The results provide a basis from which to predict building settlement response with greater certainty. INTRODUCTION With continuing population growth and increasing urbanization expected in the next decades, there is an urgent need for a next generation of infrastructure. It is likely that a large part of this infrastructure will be underground. Such creation of urban underground space frequently involves the excavation of shallow tunnels in close proximity to existing structures and utilities. For example, along the Crossrail project in London more than 1,200 structures are located within a possible influence area of the tunnel construction (Torp-Petersen and Black 2001). The assessment of building damage plays a vital role throughout the planning, design and construction stage of urban tunneling projects. However, while predictions of tunneling-induced deformations in the greenfield can generally be made with some confidence, much uncertainty exists about how structures interact with ground movements arising from tunnel construction."

Jan 1, 2016

By Cleophus Short

[Of the many occupations in and about the coal mines, those of the haulage crews are among the most hazardous. Statistics ship that the second greatest number of fatalities about the coal mines occur during haulage ion and through the use or misuse of haulage equipment. During the five year period between January 1, 1957 and January 1, 1962, the m stone mine had a. Sack haulage frequency of 4098 and mined 3, 541,939 toads per haulage fatality. Coal mire haulage is similar in respects to railroading. We gee very serious consideration to the instillation of tack and to the selection of the haulage crews. In doing this, we are attempting to have our coal mine haulage as. Safe as that of the railroads.]

Jan 1, 1963

By R. F. Harig

Designing an underground nuclear waste repository is a complex process. Although many decisions are involved before the design is complete, the first three--what the target horizon is, what the underground boundary is, and where the entry point will be located--are important because they establish the basis for the entire repository design. Even more important than these decisions, however, is the data on which the decisions are based. Because the current data are limited, an aggressive data gathering program is needed during the next design phase to augment information about the intricate interplay among all facets of the repository design and the geologic medium in which the proposed repository is to be developed. Although unique to modern engineering enterprises, the challenges involved in designing a repository in the unsaturated zone are within current technology and engineering practices.

Jan 1, 1991

By Michel Dagbert

The determination of the precision of reserve estimates (tonnage, grade, quantity of metal) for an entire deposit or a large block in a deposit has received some attention in the early developments of geostatistics. A general formula to derive the estimation variance of any linear combination of a large number of sample values can be found in any geostatistical textbook like David (1977) or Journel and Huijbregts (1978). A particular case of this general formula is of course the kriging of the entire deposit. However, besides the technical difficulty of dealing with many samples the application of this formula necessitates the knowledge of the covariance between any two samples in the deposit. This is quite unrealistic in the usual case of limited stationarity where the assumption of a covariance or a variogram just function of the distance vector between two samples is only valid for samples within the same area of restricted size.

Jan 1, 1982

By Tadashi Nishida

Subsidence due to mining caused various kinds of damage to the surface structures, and actually great deal of mining damage becomes the severe social problem at some time in many coal fields, but the most of mining damage was restored at present. Recently, the effect of old coal working on the deformation of newly constructed structures has become into question, because it was obliged to plan many engineering structures in old mining areas for the shortage of adequate construction sites and the difficulty of getting location. That is, building, dams, bridges for railroads and highway, power plants, tunnels, storage tanks and so, have to be built on the ground which has old coal working.

Jan 1, 1982

By P. Oghazi

It is possible to have traceability in the mining industry, by parameters and signatures like particle mineralogy, mineral association, texture and mineral liberation. The study is on an apatite-iron ore deposit at Malmberget, Sweden, and characterizes an ore body both mineralogically and texturally in a quantitative manner by using analytical methods like optical microscopy, microprobe (EMPA) and an automatic SEM based system, Particle Texture Analysis (PTA). The mineralogy was evaluated by PTA and characterized by modal mineralogy, mineral liberation and mineral associations. Magnetite has a simple outline and straight grain boundaries and the gangue minerals have a finer particle size with a more complicated texture. The PTA analysis also shows that apatite is associated to magnetite as mixed particles, while smaller grains of magnetite are inclusions in feldspar. Result from particle texture analysis shows that there is a connection which link to the mine-to-mill context, and it may be used to create traceability. This link is not the associations of the main ore mineral magnetite, nor the modal mineralogy. Instead, it is the mineral associations of contaminating minerals (apatite and feldspar) that appear to be most promising since they survive from mine to mill. The modal mineralogy may be used to understand how contaminated minerals break into or out of particles size fraction during grinding.

Jan 1, 2010

By E. Watkins, S. J. Schatzel, K. Ajayi, V. Gangrade

The National Institute for Occupational Safety and Health (NIOSH) has been conducting research related to unconventional gas wells positioned in abutment pillars associated with active longwall mining in Southwestern PA. The Ventilation and Explosion Prevention Team at NIOSH is working toward predicting and characterizing a hypothetical casing breach and its effect on the safety and health of mine workers, gas well workers, and the general public. An important aspect of this research is to distinguish coalbed gas from shale gas in the mine environment as an indicator of a casing breach. Another noncoal gas source exists in the region in the form of underground gas storage fields which also have the potential to migrate towards mine workings. During a potential gas breach, the addition of excess natural gas to coal mine environments will exceed the anticipated ventilation loading and can create a mine explosion hazard. A methodology has been developed to distinguish these gas sources. Gas samples from the three sources were analyzed by gas chromatography, and interpretive methods were applied to distinguish the populations graphically and statistically. Bivariate plots using the hydrocarbon index and the normalized molecular ratios showed that the sources occupy different regions of the graphs. All samples of non-coal gas contained under 2% CO2, and all coal samples included greater than this amount. A multivariate T-squared (T2) test analysis relating comparing data in pairs showed a low p-value (dimensionality parameter) and a high T2 test statistic for all comparisons, indicating that these sources are different and distinct gas populations. Ultimately, stakeholders from the mining and gas production industries can utilize this method to identify gas sources and a potential casing breach.

Mar 2, 2022

By Herb Wilson

The Klondike symbolized one of mankind's driving forces - the desire to lay one's hands on a scarce resource, gold, in that case - and in doing so to make some money along the way. It can be argued that construction aggregates - a once lowly and ignored sector of the natural resource industries - have become the desired targets of their own "Klondike." This began in the 1970s and accelerated to a frantic pace in the 1980s. The scope of industrial minerals is very wide. It ranges from high value minerals such as talc, bentonite and kaolinite to the truly humble minerals of sands and gravels, limestones and granites. Their major end uses are in construction aggregates. A rich variety of different mineral types all make good construction aggregates. However, those successfully used have two fundamentals in common: • Their technical characteristics are appropriate for the requirements of their end use. • They are located within an economic distance from the market. The North American market This is the largest construction ag¬gregate market in the world. Consumption in 1990 reached 2.2 Gt/a(2.5 billion stpy). This rate of consumption has grown steadily over the past decades. In the United States, from 1963 to 1989, it averaged a 1.6% compound growth rate. Within this long-term trend, there are business cycles, because aggregate demand is closely linked to economic strength or weakness. The North American market also displays the greatest per capita demand for aggregates when compared to the major industrial economies (Table 1).

Jan 1, 1993

By S. C. Libby

The amount of fine material (minus 60 Tyler mesh) generated during calcination and/or handling of calcined abrasive grade bauxite from Alcoa's operations at Moengo, Suriname, has recently increased relative to past production experience. Bulk samples of raw abrasive grade bauxite from three deposits in the Moengo area have been studied in order to determine the factors controlling the generation of fine material samples from the Jones IC and Tapira deposits, which generate excessive amounts of fine material, have been compared with reference samples from the Begi Gado deposit, which does not generate excessive fine material. Additional type samples of abrasive grade and marginal abrasive grade bauxite from deposits in the Moengo area which represent different bauxite textures found in the Jones IC, Jones I, and Begi Gado deposits have also been studied. Field observations in the Moengo area have indicated that abrasive grade bauxites with a dull, earthy appearance generally do not generate excessive fines. On the other hand, excessive fines are generally associated with coarsely crystalline bauxite in which the gibbsite crystals appear to sparkle in sunlight.

Jan 1, 1980

By J. K. Ross, K. O. Hoal, S. K. Appleby

Understanding ore variability is a key factor in the geometallurgical analysis of a deposit and is beneficial to process development and mine planning. Ore variability is a function of the mineralogy of a deposit, in terms of both ore and gangue minerals and their textural relationships. This study integrates optical microscopy and quantitative mineral analysis to characterize the mineralogy and texture from 13 samples from different lithologic units at the Bingham Canyon Mine. The analysis identified several parameters, such as modal mineralogy, alteration assemblages, distribution of mineral phases and alteration assemblages and microfracture and void space distribution. These parameters can have an impact on the materials’ behavior during processing. This study demonstrates that quantitative mineralogical analysis can provide detailed information for improved understanding of ore variability.

Jan 1, 2010

By D. A. Fenton

The reliability of large diameter, high horsepower ball mill is paramount when large production and minimum downtime is required. The 17 ft. x 56 ft. double compartment ball mill at St. Lawrence Cement Company has the first gearless drive built in North America and has the world's largest hydrodynamic bearings currently built and running. The machine has seen three years operation and has met its specifications. The mill was designed by Aerofall Mills Limited and the gearless drive built and designed by the Canadian General Electric Company. This paper discusses the operation of the first North American installation of a gearless drive ball mill from the mechanical, electrical and process aspects.

Jan 1, 1977

By R. L. Shaw, D. W. Alexander

Consolidation Coal Company's Loveridge Mine operates the only coarse coal hoisting and overland slurry transport system in North America. The system has been in operation since April 1980 and according to current haulage levels will have handled over two million tons by this conference date. Original performance goals have been exceeded. The systems will be described and their application to rapid excavation and tunneling haulage needs will be discussed. Manuscript not received in time for publication.

Jan 1, 1983