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By James D. Piper

In the summer of 1957,9 the University of California sponsored a World Conference on Prestressed Concrete in San Francisco to which were invited a number of Soviet engineers. While attending the conference, these engineers in turn asked the University to form a delegation of American engineers to visit the Soviet Union the following year for the purpose of studying Soviet advances in concrete technology. A six man delegation was formed, and the dates of the Russian tour fixed for May 10th through May 21st, 1958. Before arriving in the Soviet Union, the American Delegation attended the Third International Congress on Prestressed Concrete in Berlin. While there, we noticed that the delegation from the U. S. S. R. used displays and showed motion pictures of many construction projects which we later were shown in Moscow. Our delegation left East Berlin by Russian aircraft on May 11th, and arrived in Moscow that afternoon. We were met by our Russian engineer hosts from The Academy of Construction' and Architecture who made all subsequent arrangements for our itinerary. This Academy has no counterpart in the United States. It. does 40 per cent of all engineering-and scientific work in the building construction field and coordinates 60 per cent of that done by other Soviet agencies. Due to the prestige of the Academy in Russian affairs, our delegation was able to obtain a surprisingly broad picture of construction activities in Moscow and Leningrad in just ten days time

Jan 1, 1960

By W. A. McKinney

The U.S. Bureau of Mines, Kennecott Copper Corp., and New Mexico Institute of Mining and Technology are cooperating on a research project to improve extraction of copper from previously leached waste dumps that are in part compacted and impervious to leach solutions. The field work is being done at the "J" leach dump, Chino Mines Division, Kennecott Copper Corp., Santa Rita, N. Mex. The laboratory percolation leaching tests were made at the U.S. Bureau of Mines Salt Lake City Metallurgy Research Center on drill core samples from the "J" dump to determine how much copper might be leached if permeability could be restored by explosive heaving or other means. The core samples from nine drill holes on "J" dump contained from 0.06 to 0.14 percent copper. Copper extractions ranging from 15 to 3 percent were obtained in 75 days by percolation leaching of minus-1-inch material with dilute sulfuric acid. The tests results indicate that about 2'7 percent of the copper remaining in the "J" dump could be extracted under ideal leaching conditions.

Jan 1, 1970

By Behzad Khorshidi

"The ultimate objectives of the post-tensioned strands are to connect the precast segments into a ring and provide pre-stress in the tunnel circumference. The method involves inserting the strand through the preliminary embedded duct in the precast concrete segments and then tensioning the strand by jack and fastening it. The post-tensioned strand eliminates the necessity of bolt connections between the segments and may reduce the labor cost and increase speed of lining construction. Pre-stressing of the segmental lining reduces the steel reinforcement or fiber volume in precast segments and/or thickness of the precast segments which would result in reducing the manufacturing cost of them. Pre-stressing would reduce cracking and increase water tightness, and would provide smooth intrados due to eliminated bolt joints and pockets in the tunnel lining. Pre-stressing would increase resistance to internal pressures as well. Further, this system could work very well structurally in tunnels with squeezing rock or tunnels with high seismic loadings. INTRODUCTION OF THE METHODPost-tensioning is commonly used in the construction of bridges, large buildings, nuclear power stations, and water tanks but its utilization in tunnels is still in its infancy.The precast pre-stressed concrete segmental lining can be used for shield tunnels. It provides a reinforced lining ring by the following construction stages and as shown in Figure 1:1) Segments to be assembled by TBM to complete a full ring2) Steel strand to be inserted through embedded duct (sheath) within the segments3) The strand to be tensioned by Jack after anchorage of the other end4) The strand to be fastened after reaching required tension load5) The horizontal strands (if necessary) to be installed, tensioned and fastened6) The recesses and gap between strand and duct to be filled by groutingFurther, Figure 2 shows an unbonded post-tensioning strand model; Figure 3 shows an anchor sample (Xanchor); Figure 4 shows a duct (sheath) and anchor within reinforcement; Figure 5 depicts the posttensioning of a strand by jack; and Figure 6 is an image of the Midorigaoka Trunk line tunnel in Sagamihara, Japan which was constructed using this system."

Jan 1, 2016

By Fred C. Bond

Any improvement in the accuracy of commercial comminution calculations under the Third Theory must be accomplished either by increased precision in energy input measurements, or by a better evaluation of the total new crack length produced, as indicated by the feed and product size distributions. Since at the present time feed and product sizes are approximated solely by the microns 80% passes, the most promising opportunity for increased accuracy lies in consideration of their plotted size distribution characteristics. This paper shows how more accuracy can be obtained over an increased range of feed and product sizes from size distribution studies.

Jan 1, 1962

By J. F. Colinet, W. R. Reed, J. D. Potts

Dust surveys were conducted at six underground coal mines to determine if deep-cutting practices expose face workers to higher levels of respirable dust. The surveyed mines were able to successfully mine deep cuts without significantly increasing the dust exposures of face workers. In general, all of the selected mines exercised good dust control practices by maintaining water sprays, scrubber airflows, proper curtain setback distances and providing sufficient airflow to the active faces. For exhausting face ventilation, field data indicate that scrubber airflow is the most important factor for controlling dust. Data collected for this study indicate that 20-mesh screens should be cleaned for every 12.2 m (40 ft) of advance, because 22% of the deep cuts surveyed for this study experienced a 20% to 35% decrease in scrubber airflow over the course of the cut. For blowing face ventilation, field data and past research indicate that dust control is aided by maintaining a proper curtain-to-scrubber airflow ratio of 1.0 (measured before scrubber activation), as well as a curtain setback distance that allows the miner operator to stand at the mouth of the curtain for the entire cut. Dust levels on the bolting faces did not appear to be affected by the longer cycles associated with deep-cut mining when good ventilation practices were used.

Jan 1, 2011

By B. Anameric

Considerable effort has been directed towards understanding the carbothermic reduction mechanisms of self-reducing, fluxing dried green balls to produce pig iron nuggets. Given the geometry of the situation, some investigators believed that the shrinking core model was applicable. Hence, this study involved investigation of the applicability of the shrinking core model to pig iron nugget production. The experiments involved heat treatment of dried green balls utilizing either a laboratory-scale resistance box furnace or a gas-fired muffle furnace at various furnace temperatures and residence times. The products were analyzed for the following: (i) preferred reaction pattern, (ii) distribution of the metallized areas, (iii) % iron content variation in the pig iron nuggets from surface to center, (iv) carburization pattern and (v) physical and chemical properties of the pig iron nuggets. It was determined that the reduction of iron oxide occurred simultaneously throughout the sample and not beginning at the surface and propagating inward; thus the shrinking-core model was not applicable. Heat transfer and gas diffusion from surface to center were not the rate-limiting steps for reduction and carburization reactions.

Jan 1, 2011

By L. Adler

The valuable Maximum Utilization Factor (MUF) concept has been extended to other rotating excavators beyond stripping shovels and draglines. In this concept the boom reach and bucket capacity are multiplied to get an MUF, then normalized by dividing by the equipment weight. Statistical analyses were applied to the remaining shovels (hydraulic and cable), draglines, and backhoes. Positive correlations were found. Stripping shovels and draglines were also re-examined. The results provide an estimate of equipment diggability and encourage versatility by the interchange of the boom and the bucket. The concept further clarifies the existing equipment classification by delineating general excavating, loading, and stripping kinds. The results also forecast trends, and noted innovative advances and possible retrogression. Extension to other boom excavators, such as front-end loaders is recommended. The MUF concept provides one of the few indices of gross external characteristics available to the engineer-user of equipment.

Jan 1, 1990

By Robert S. Foote

The U.S. Energy Research and Development Administration (ERDA) is currently conducting a national program to survey for uranium the conterminous United States and Alaska by 1980 using airborne and surface techniques. This paper discusses the techniques used and some of the results of airborne surveys conducted to date by Geodata International, Inc. Airborne gamma radiation and the earth's magnetic field data are measured to provide data leading to regions potentially more favorable for the exploration and discovery of uranium ore. High-sensitivity radiometric and magnetic field data have been gathered from an aircraft with an average surface altitude of 400 feet (Figure 1). Under most conditions, data are usable up to an aircraft surface elevation of about 1250 feet where limitations will be discussed. Results of data analysis under GJO-1632, GJ0-1644, GJO-1654 and GJO-1663 will be discussed.

Jan 1, 1976

By Alan Bauer

In recent years there has been increasing interest in employing the technique of explosive casting in strip mines. Explosive casting, applied to dragline mining, describes the procedure whereby the overburden is horizontally displaced by blasting causing a portion of the material to be thrown into the previously mined cut. Therefore, it is not necessary to subsequently excavate this waste with the stripping equipment. In addition, allowing the overburden unrestricted movement during the blast most often results in improved fragmentation and enhanced machine productivity. The method is receiving attention because the capital and maintenance costs of stripping equipment has risen rapidly in relation to explosives costs. Improved productivity is necessary to maintain unit costs at an acceptable level.

Jan 1, 1983

By Felicia F. Peng

Employing the combination of two types of polyelectrolyte might become necessary to enhance both settling rate of the flocs and water clarity of fine particle suspension in high capacity thickening process. The sequence of addition, mixing, type and dosage of polymer affect the overall performance and capacity of a thickening process. For the sedimentation of copper flotation tailings, the cylinder test results showed that two different techniques may be used to achieve the required performance including high settling rate of flocs, underflow density and overflow water clarity, by either adjusting pH prior to anionic polyelectrolyte flocculation, or using a combination of polymer flocculant and coagulant (dual polymer system). The dynamic thickening testing results showed that only the approach using a dual polymer system is able to meet the required performance. The effects of polyelectrolyte dosage, the sequence and numbers of polyelectrolyte addition, feed concentration, bed level and rake speed on the settling rate, underflow solid, and water clarity were studied in cylinder test and a laboratory dynamic thickening unit with various conditions related to the thickening process. The dynamic test is especially valuable in evaluating the addition and mixing of polymers. The results were evaluated quantitatively, using total suspended solids in supernatant, underflow density and capacity per unit settling area per unit time as the measure of effectiveness. The objective of this study is to quantify and explain some of the parameters involved in the sedimentation of copper flotation tailings.

Jan 1, 1997

By C. I. Basilio

The mechanisms involved in the adsorption of modified thiol-type collectors on sulfide minerals have been investigated in the present work. These collectors belong to the broad classes of thionocarbamates, thioureas, thiophosphates and thiophosphinates. They differ significantly from the traditionally used thiol-type collectors, such as xanthates and dithiophosphates, in terms of structural features that involve either the introduction of an additional oxygen donor or the alteration of electron densities on donor atoms. Electrochemical studies suggest that the adsorption of these classes of collectors is probably the result of a coupled reaction of the EC-type, involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the overall adsorption process is controlled by both the E, and pK of the system. The role of structural features in changing the interaction of the donor atoms with sulfide minerals is also discussed.

Jan 1, 1991

By D. E. Healy

In 1989 an Autogenous Grinding Task Force was formed to study potential autogenous grinding circuits to replace the existing semi-autogenous grinding at the National Steel Pellet Plant located in Keewatin, Minnesota. Pilot plant test work performed by the Hanna Research Center (HRC) indicated that fully autogenous grinding with pebble extraction and crushing could feasibly be incorporated into the existing circuits. In 1990, one of the existing ten grinding mills was converted for an in-plant test incorporating pebble crushing. The full scale test work conducted in 1990 and 1991 verified the pilot plant projections with primary mill throughputs from the fully autogenous circuit utilizing pebble crushing being greater than throughput of the existing SAG mill circuits.

Jan 1, 1992

By J. E. Urosek

In October, 1990, a fire started in a large underground coal mine in Western Pennsylvania. During fire-fighting activities, an explosion occurred and all personnel were evacuated. Safe re-entry into the mine was not possible and the mine was sealed. Recovery efforts began in January, 1991 and continued until March, 1991, when permanent underground seals were installed between the fire area and the mine openings. This paper describes an extensive atmospheric monitoring program conducted by the Mine Safety and Health Administration (MSHA), Pittsburgh Safety and Health Technology Center (PS&HTC) including the analysis of mine fire gases, natural ventilation, fan pressure and air quantity distribution.

Jan 1, 1993

By W. Bakiewicz

The Lower Indus Basin deposits form a substantial unconfined alluvial aquifer of excellent quality. This aquifer contains basically highly saline groundwater, overlain in places by considerable amounts of freshwater whose origin can be traced to the present and historical courses of the River Indus. In the past the main source of groundwater recharge has been direct river seepage and water tables were generally deep. Since the establishment of a perennial irrigation regime however, deep percolation from the increased irrigation supplies has predominated and the water-table has risen to within a few feet of the surface. The river system itself is being progressively developed for irrigation and very shortly a situation will arise where the entire low winter flow will be utilised. Fresh groundwater will then be exploited to supplement the surface supplies, and at the same time a drainage system, mainly based on wells will be used to stabilise the water-table at safe depths. This paper discusses some of the methods used to ensure optimum-economic development of the fresh groundwater and describes the general design philosophy evolved by the authors firms for both irrigation and drainage wells, with respect to both well configuation and operation. Water quality standards are discussed in as much as they affect subsequent use of the groundwater. A few particular aspects are considered, including that of the values of the relevant aquifer constants, the construction of wells and the determination of screen losses. A major problem solved during the Lower Indus Project investigations has been the design of wells to-produce fresh water from layers overlying saline water. This solution is also discussed.

Jan 1, 1967

By Bauer, Steve, Colin Goodwin, Gerald, Randy Dempsey, Courtland

"The City of Ottawa’s Combined Sewage Storage Tunnel consists of two interconnected tunnels totaling 6.2 km with a diameter of 3m including access shafts and hydraulic structures which connect to the City’s most critical sewers. This tunnel will be built 15m to 30m below ground in the downtown core adjacent to, and crossing below, the Light Rail Tunnel, which introduces additional considerations in terms of sequencing and risk mitigation. The City embarked on a unique Procurement Process to address the risks involved with a large tunnel project and those associated with tunneling below downtown, underneath and adjacent to UNESCO World Heritage Sites, and connecting to live critical sewers. This paper describes the unique procurement approach employed and the contractual risk mitigation measures developed to provide the best value while minimizing risk. Specific features include Market Sounding, using a Fairness Commissioner, Contractor Prequalification and Risk Mitigation Measures in the Tender documents. INTRODUCTION This paper describes how the City of Ottawa (the City) and the project design team developed a strategic Procurement Process and Tender that incorporated industry best practices for technical and contractual risk management for the Combined Sewage Storage Tunnel (CSST) project. The process was unique in that, while it employed a systematic review of project risks, it also solicited input from industry, stakeholders and provincial and federal partners to develop the request for Tender for this traditional design-bid-build project. Key drivers for this approach were initiated from the City’s concerns for cost control, cost certainty and overall project risk mitigation. To address these concerns, the City implemented the risk review and mitigation process right from the project design team selection. It was critical that the project design team embraced this risk management philosophy and carried it through each phase of the project. This paper serves as an excellent resource for municipalities or other owners embarking on a similar tunnel project, on how to properly apply industry best practices and the benefits of using them."

Jan 1, 2016

By P. G. Dempsey, J. R. Heberger, J. P. Pollard

During a mine disaster or emergency, underground air can quickly become contaminated. In these circumstances, all underground mine workers are taught to don breathable air supply units at the first sign of an emergency. However, no contemporary oxygen consumption data is available for the purposes of designing breathing air supply equipment specifically for mine escape. Further, it would be useful to quantify the oxygen requirements of breathing air supply users for various escape scenarios. To address this need, 14 participants crawled a distance of 305 m each while their breath-by-breath oxygen consumption measurements were taken. Using these data, linear regression models were developed to determine peak and average oxygen consumption rates as well as total oxygen consumption. These models can be used by manufacturers of breathing air supply equipment to aid in the design of devices that would be capable of producing sufficient on-demand oxygen to allow miners to perform self-escape.

Jan 1, 2015

By M. A. Cristovici

The possibility of using surfactants as wetting agents for the suppression of sulphide ore dust has been investigated. Numerous surfactants were examined to determine their characteristics and to investigate their ability to improve the wetting of the sulphide ore dust. However, the surfactants selected as suitable dust suppressors proved to have a negative effect on the flotation of the ore contaminated with such reagents. A method was developed to eliminate the detrimental influence of dust-suppressing surfactants. It consisted of surfactants adsorption on activated carbon and separation of loaded carbon prior to flotation. The technique is simple and requires minimal changes in the plant flowsheet.

Jan 1, 1990

By G. Nash

Despite further declines in production for some producers, 1986 proved to be a landmark year for the asbestos industry. The key event was the adoption of The Asbestos Convention by the Inter- national Labour Organization (ILO) and its 150 member countries. The document, entitled "Safety in the Use of Asbestos", reaffirms the international consensus on the "controlled-use" approach to chrysotile asbestos regulation. The decision of the ILO has come at a critical point in time. It represents a major turning point and provides an important building block for the long term future of the asbestos industry.

Jan 1, 1987

By Boleslav Taraba, Antonín Taufer

Thermovision monitoring of surface temperature has been examined for the purpose of detection of spontaneous combustion of early stage. Measurements were carried out in bituminous and subbituminous coal mines. It was found that surface temperature heterogenities can be considered as common phenomenon in mine openings. However, the most of the observed temperature heterogenities were not connected with coal spontaneous combustion of early stage. These, so called [non-spontaneous combustion] temperature heterogenities in surface of mine openings were found to be caused by: l. Different conditions of heat transfer between opening surface and air stream; 2. Low temperature (natural) oxidation of coal; 3. Dissipated heat loses of working machine. Sites of early stage spontaneous combustion of coal were characterized by: 1. More significant, local rise in surface temperature comparing with low temperature coal oxidation; 2. Evolution of carbon monoxide with local concentration near the surface of such site more than about 15 ppm (bituminous coals) or 30 ppm (subbituminous coals). INTRODUCTION Mine fires are a serious hazard to life and result in a considerable loss of coal reserves. Thus, great attention is paid to investigation of new methods enabling already early detection of self-heating of coal. The earlier a fire is observed, the easier would it be to deal with. Detection methods used in coal mines are mainly based on: 1. [Mine air analysis]. Changes in composition of mine air are examined. Products of spontaneous heating of coal, not being present in mine air under normal conditions, are considered as indicators of anomalous behaviour of coal (carbon monoxide, unsaturated hydrocarbons) (Mackenzie-Wood and Strang, 1990). 2. [Temperature measurements]. Sites of higher temperature level comparing surroundings are looking for underground using various direct or indirect methods of temperature measurements. This paper summarizes experience from thermovision monitoring, as one of the latest indirect temperature measurement technique, used for the purpose of early detection of self-heating of coal in mine openings. INFRARED THERMOVISION Infrared thermovision device of AGEMA Infrared systems AB (Sweden) was used for the in situ measurements. The constant value of emissivity factor, 0.95, was pre-set as the most probable level of emissivities of coal and rocks in mine conditions.

Jan 1, 1993

By P. E. Damon

An arsenal of isotopic techniques is avail-able that can date the full range of hydrothermal ore deposits. The following are prerequisites for ideal results: (1) Careful collection of samples that are related to the event in a field and process context; (2) Optical examination of the component selected for dating to be sure that it has not been altered; (3) Careful preparation of a pure component of the sample selected for dating; (4) Precise and accurate measurement; (5) Knowledgeable interpretation of the data with reference to decay systematics, properties of the component analyzed as well as the field context and thermochemical environment of the ore process.

Jan 1, 1992