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By S. Kobayashi, A. E. Armenákas, C. Mylonas

Earlier work1-4 has shown that commercial mild steels under static loading at the lowest natural operating temperatures fracture in a brittle manner only when damaged by a suitable history of straining. Notched and then compressed plates have fractured in subsequent tension at loads as low as 10 pct of the limit load and precompressed smooth bars at a subsequent extensional strain as low as 0.01. The comparison of the average net fracture stress with the flow limit stress was shown to be an excellent criterion of brittle or ductile behavior of mild steel structures when only loads and general stress levels are known. The present investigation shows that the deformation at fracture is a far more sensitive measure of brittleness than the fracture stress. Both criteria, deformation and stress, are used to determine the amount of uniform precompression of two mild steels, ABS-B and Project E-steel, resulting in brittle fracture under the strong constraint of a subsequently machined severe circumferential groove. The fracture stress equaled or exceeded the theoretical flow limit Ól = 2.680., ('based on the elevated yield stress at each prestrain) up to prestrains of about 0.20 and then fell off to about 1 at prestrains of 0.60. Yet a prestrain of only 0.05 reduced the elongation at the shoulders by a factor of about 4. The total plastic elongation of a region surrounding a sharp notch in prestrained steel deternines whether or not fracture will be initiated in large structures, hence is a direct and realistic measure of the remaining ductility and provides an excellent test of the material's resistance to embrittlement. ALMOST all engineering structures of mild steel which failed in service in a so-called "brittle" manner exhibited appreciable local plastic deformation (more than 1 pct) and a mixture of "cleavage" and "shear" fracture surfaces. Furthermore, the peak local stress in an advancing crack is always high. Such simple criteria as pure cleavage, absence of plasticity, or fracture stress, so useful in other fields, are insufficient to characterize brittleness in engineering structures at ordnary temperatures. The "brittle)' behavior of engineering structures is caused by the limited ductility at cracks or notch regions, as shown by recent work at Brown University summarized and extended in Refs. 1 to 4. It was also shown that the local ductility of mild steel may be catastrophically reduced by a suitable strain and temperature history similar to those which may occur in real structures. Localized yielding begins at the notch roots at low loads but is contained by surrounding elastic regions. The plastic strains are hence small. They increase slowly with the load up to the flow limit or limit load for an ideally plastic material. Unrestricted plastic flow then occurs. At such strains the real material locally st rain-hardens and fractures. With work-hardening materials no flow limit exists, and the transition from low to high plastic strains is gradual but increases more rapidly at loads close to the flow limit of an equivalent perfectly plastic material. When the available ductility is sufficient for reaching the limit load, the behavior is normal or "ductile". With insufficient ductility, fracture will occur at a low load and will be defined as "brittle". Accordingly the sufficiency or not of the ductility at a notch is reflected in the magnitude of the fracture load or average net stress as compared with the limit load or flow limit. The application of this criterion gave surprising results. Service failures under semistatic loading occurred mostly below the limit load, hence were "brittle". On the contrary all static tests with undamaged commercial mild steels reached the limit load in spite of the deepest notches and temperatures below Charpy impact transition (say about -30°F or higher). Notched bars showed no brittleness even under fully dynamic axial loading up to 1.5 x107 psi per sec at -23°F and about 2.5 x l06 psi per sec at -ll0°F, but broke in a brittle manner at -200°F and l03 psi per sec.' To propagate a fracture at low load, experimenters had to trigger it by superimposing a strong dynamic impact at a notch cooled by liquid nitrogen as in the Robertson5 or Esso tests.' Once started the cracks would run through warmer regions of smaller stress. Obviously the ductility of the apparently undamaged commercial steels was "sufficient" in the laboratory tests but not in the service fracture, where it must have been reduced by some embrittling procedure of fabrication or service. These conclusions were confirmed by the achievement of low static stress (brittle) fracture initiation in unwelded steel after a local reduction of ductility by simple prestraining. Symmetrically notched plates of undamaged mild steel cooled below the Charpy V-notch transition range were tested in central static tension: Undamaged plates withstood loads of limit intensity, but when subjected to prior in-plane com-pressive prestraining perpendicular to the notch axis and to accelerated aging, the plates fractured completely or partially at very low static loads, as low as one-tenth of the flow limit.2-4 However, damage could not be easily related to the strongly variable prestrain around a sharp notch. To obtain easier strain measurements, it was decided to use axially precom-pressed bars and bent bars. Final testing was done by

Jan 1, 1970

By Paul Nicholas, Raju Gottumukkala

"India’s economy is expanding with rapid urbanization. Improvement in infrastructure is a keystone to the Indian government’s economic plans, including expansion of transit systems. Most of these systems are designed with elevated and underground sections. New Delhi, a city of 23 million people, suffers from heavy traffic congestion and pollution. The transit (metro) system is seen to be of critical importance. Phase 3 of the Delhi transit system project is 140 kilometers (km), with 40 km of twin-bore tunnels requiring 35 tunnel boring machines (TBMs) for construction. Transit systems are also under design or construction in Chennai, Bangalore, Kolkata, Hyderabad, Jaipur and Mumbai. Most have twin-bore tunnels. At present, 55 TBMs are operating on underground metro construction, and future projects will increase this number. This paper highlights the unique challenges of construction of underground metro systems in highly congested urban environments, using Kolkata and Delhi systems as examples. INTRODUCTION The first transit system in India was constructed in Kolkata (India’s third-largest city by population.) This line is 28 kilometers (km) in length, has underground and at-grade sections, was built in phases, runs north/south, and has 24 stations. This project was sanctioned in 1972, started construction in 1984, and was completed in 1995. The tunnels were constructed primarily by cut and cover methods with some open-face, compressed air shield tunneling. In 2006, the urban transport policy recommended construction of transit rail systems in all urban cities with a population exceeding 2 million. Further, in 2014 the central government stated that it would assist in financing transit systems in all cities with a population of over 1 million. In 2015, the central government approved the development of transit systems in 50 additional cities across India with a budget of $75 billion (see Figure 1). Transit development is just part of a huge expansion in planned rapid transport systems, which include metro, bus, high-speed rail, and monorail systems. Metro systems will include elevated and underground sections with twin-bore tunnels and underground stations. In the Delhi/National Capital Region (NCR), now the largest city in India by population, Delhi Metro Rail Corp (DMRC) was formed in 1995 as a joint venture company between the central government and Delhi state. DMRC operates the Delhi metro system. (see the case studies described later in this paper). DMRC has developed an external function to carry out studies and to offer consultancy to other cities planning transits. Since its inception, DMRC has produced Detailed Project Reports (DPRs) for every metro and monorail project in India. In 2012, DMRC became a partner in the management consultancy for Jakarta Mass Rapid Transit System, its first project overseas. DMRC became a model organization for other cities to follow. These cities have included Chennai, Hyderabad, Kolkata, Bangalore, Jaipur, Mumbai, Ahmedabad, and Nagpur. Other cities (e.g., Lucknow and Patna) are in the metro planning phase. Metro systems are under construction or partially operating in Hyderabad, Bangalore, and Jaipur."

Jan 1, 2016

By Matteo Cortinovis, Giuseppe Gelmi

"INTRODUCTIONEdilmac dei F.lli Maccabelli (hereinafter referred to as Edilmac) has recently developed a special civil engineering application using the Raise Boring technology with the assistance of Inrock MGS (Magnetic Guidance System). Applying the Paratrack Magnetic Guidance System coupled with a directional mud motor to the drill string allows a better accuracy compared to standard drilling, as showed in our tests. This is the first time the Paratrack System has been applied to the Raise Boring technology. RAISE BORING METHOD STATEMENT The Raise Boring technology was born in North America during the Sixties. In 1962, Ingersoll and Robbins were the first companies to produce Raise Boring Machines (RBM). The technology was first used in the underground mine industry, in order to bore ventilation shafts and passes through different levels, thus reducing the cost of haulage. The Raise Boring method is only feasible in stable rock conditions. The Raise Boring method consists of drilling a small diameter pilot hole that reaches a tunnel located at the bottom of the drilled hole. Once the pilot hole reaches the tunnel, a reamer head is installed at the end of the drill string and pulled up, creating the hole with the designed diameter (Figures 1 and 2). The main equipment, which is required to perform Raise Boring activities, is the following: •,An RBM; •,A tricone bit; •,Drilling rods; •,A reaming head; The standard mucking of the pilot hole is done with water or bentonite mud. For the last 30 years, Edilmac has developed a mucking process, which uses compressed air with the addition of foam or a small amount of water for dust control.Pilot hole tricone. The drilling of the pilot hole is usually performed with a tricone bit having a diameter between 11” (27.61 cm) and 15” (38.10 cm) (Figure 3). High strength rods. They generally have a diameter ranging from 10” (25.40 cm) to 12 ?” (32.70 cm) (Figure 4), depending on the length and the final diameter of the shaft."

Jan 1, 2016

By Jacob A. Jordan, Rachel M. Garrett, W. Robert Thompson III, James C. Pegues

"Environmental control structures for an existing fossil-fuel power generating plant near Pascagoula, Mississippi faced several design and construction challenges due to space limitations. Conceptual design calculations indicated drilled shaft foundations would likely be needed to accommodate the higher lateral and compressive loads expected under some structures. A maximum drilled shaft diameter of 60-in was preferred due to various space constraints. Smaller diameter drilled shafts were deemed acceptable under structures with more moderate loading conditions. Furthermore, augercast piles were considered where lateral loading was not a governing design criterion.A series of SPT borings and CPT soundings revealed a subsurface profile consisting of soft to firm clays to depths of about 25 feet, underlain by fine to coarse sands. The apparent relative density of the sands was loose just below the clay, with increasing density noted with an increase in depth.Analysis of conventional drilled shafts indicated needed capacities could not be achieved unless shaft lengths exceeded 100 feet. Post-grouted drilled shafts were therefore evaluated to decrease shaft lengths by taking advantage of increased base capacity. Analyses showed the higher predicted capacities needed for some structures could be achieved with this approach. Final design for the project incorporated 90-ft long, 60-in diameter post-grouted drilled shafts; 60-ft long, 48-in diameter post-grouted drilled shafts; and 60-ft long, 48-in diameter conventional shafts. Both post-grouted and conventional trial shafts were installed as part of the detailed design phase of the project. Each trial shaft included CSL integrity testing and Osterberg-cell bi-directional load testing. Load test results revealed that additional base capacity was, in fact, achieved through the post grouting process. The 60-in diameter post-grouted production shafts and the 48-in diameter conventional production shafts have been installed at the site, with the project that would utilize the 48-in diameter post-grouted shafts deferred at this time."

Jan 1, 2015

By Patrick Moore

In 1971 the government of British Columbia issued a permit for the Island Copper Mine to commence disposal of 33,000 tons per day of mine tailings into Rupert Inlet, a marine fjord on the northwest coast of Vancouver Island. There was considerable controversy surrounding the development, public hearings were held, and as a requirement of the permit the company was obliged to carry out a comprehensive environmental monitoring program. The results of this program provide a thorough assessment of the environmental impact of submarine tailings disposal over the 24-year life of the mine. Following closure in December, 1995, the monitoring program continued for three years to determine the extent of marine ecosystem recovery and re-colonization. It is apparent from the findings of the monitoring program that the mine tailings were dispersed more widely than was originally predicted. It is also clear that widespread heavy metal contamination has not materialized. In retrospect it appears that submarine tailings disposal has resulted in far less severe environmental impacts than if the alternative of land disposal had been adopted. This review highlights significant aspects of public policy decision-making, design of environmental monitoring programs, and questions of interpretation of monitoring program data.

May 1, 2002

By Morgan M. Sears, Gamal Rashed, Michael M. Murphy, Brent Slaker

In this study, a parametric study was conducted using FLAC3D numerical models to examine the impact of oblique loading, generated from seam dip, on the strength and the failure propagation pattern of a stone pillar using two simplified geometry types. In type 1, the sidewalls of the pillars were assumed to be perpendicular to the roof and the floor, while in type 2, the sidewalls of pillars were assumed to be vertical. The complex pillar geometry in dipping mines was frequently modeled using these two geometries. To capture a complete picture of the effect of seam dip on pillar stability, the modeled width-to-height (W/H) ratio of the pillars, in situ stress field, and pillars roof/floor interfaces were systematically varied to account for the potential distribution of values for these parameters across the underground stone mines in USA. Results from the numerical modeling indicate that dipping pillars have reduced strength compared with horizontal pillars. Also, an asymmetric failure propagation pattern could be obtained depending on an interaction between the W/H ratio, seam dip, in situ stresses, and pillar geometry.

Feb 5, 2021

By H Arvidson, J Vann

When only wide-spaced drilling is available, for example at concept, prefeasibility and feasibility stages, properly implemented linear estimation (including ordinary kriging) predicts grade tonnage relationships that are over-smoothed compared to final production estimates (and production). Non-linear estimation and conditional simulation are alternative geostatistical approaches that can provide more reliable estimates of the recoverable tonnage and grade from wide-spaced drilling. Non-linear estimation and conditional simulation have been rarely used on iron ore deposits. However, these techniques have had wide application in other commodities such as gold and base metals. Conditional simulation has been used in the iron ore industry (eg Guibal et al, 1997); however, its use here is outlined as a means of generating non-linear estimates, not just its use for variability and drill spacing analysis. As a rule, regardless of commodity, the decision to use non-linear geostatistics will necessitate increased skills and require more time. This decision must therefore be justified in terms of cost-benefit. Such cost-benefit analysis is not straightforward, and to help an approach for determining when linear estimates are inadequate is presented. Recommend in this paper is a well-established non-linear geostatistical approach, the global ædiscrete Gaussian modelÆ (DGM) of change of support, as a tool to establish whether moving from linear to non-linear estimates will materially improve estimate results. Also discussed is the additional use of DGM as a block model validation tool. One specific factor contributing to the lack of application of non-linear geostatistical methods in iron is the added difficulties that arise when conditional simulation and non-linear estimates are required to reproduce the numerous and often important correlations between variables in iron ore deposits. Consequently, presented in the paper is a synoptic review of non-linear estimation and simulation methodologies applicable to correlated variables.

Jan 1, 2007

By H. C. Cooke

This paper will discuss two comparatively unrelated subjects; first, a general review of the advances made at the more important properties in the last year; and second, a statement of the conditions controlling the deposition of the copper ores in the Rouyn area, as determined by last summer's field work. FIRST PART Development has been very rapid since I stood before the Institute one year ago to discuss this same subject. Then, there were many properties on which gold had been discovered, any of which might develop into a mine. Further work has eliminated the most of them as possible mines, or at least has shown that before they can attain that status further discoveries must be made on them. Then, all gold veins held forth much the same promise; now the indications are that one particular type of gold vein is of greater prospective value than others. Then, all eyes were turned toward gold as the metal of prime economic importance; now copper has taken the centre of the stage, and gold is distinctly in the background.

Jan 1, 1926

By C. C. CONCANNON

POTASH is an essential. It is necessary as an ingredient in fertilizers or as a plant food, and certainly one of the great problems, and one of increasing gravity, is the maintenance of agricultural fertility that we may have adequate food supplies. When one thinks of potash one thinks of Germany. The first and most important deposits of soluble potash salts were found in Germany, and it was through Ger- man research and the application of a highly developed knowledge of chemistry that the value of these deposits was recognized and appreciated in the field of agricultural fertilization. The Germans knew that they had something of great value in their potash resources, not only because of the advantage derived from the extensive use of it in their own intensive farming operations at home, but also because of the pressing need for it on the part of other countries. Appreciating the economic value of this in international trade, they fostered the industry to the fullest extent and devoted much attention to well organized propaganda designed to bring out the essential need for potash of German origin throughout the world. Thus every one came to believe that potash was an essential commodity of only German origin and as such it held an extraordinary position in world trade prior to 1914.

Jan 1, 1926

By Bernard Lewis

This report summarizes fundamental research end technical studies conducted in the Explosives and Physical Sciences Division, Region VIII, of the Bureau of Mines in the 2 years July l, 1950, to June 30, 1952. It is the fifteenth of a series of, ordinarily, annual reports whose aim has been to provide the reader with a resume of the research results that have appeared in published form during each fiscal year under the authorship of members of the staff. These are referred to throughout the report. ACKNOWLEDGMENTS Acknowledgments art, made to the following members of the Division wider whose mediate supervision the described studies were carried out. Stuart R. Brinkley, Jr., chief, Mathematical and Theoretical Physics Section, and special assistant to the chief of the division.

Jan 1, 1953

By E. Bauer, S. Moore

Technological advances in underground coal mining have led to a reduction in fatalities. This study demonstrated that the percentage of cumulative injuries remained largely unchanged across two decades of technological advances (1983-1984: 37%; 2003-2004: 33%). Furthermore, it was demonstrated that the average number of lost days due to cumulative injuries has increased (36±55 days and 62±82 days, respectively) which may have been due to the increased age of the work force or an increase in length of employment meaning that the mine workers injured in 2003-2004 had been exposed to ergonomic risk factors longer than those in 1983-1984. It is recommended that ergonomics processes be implemented as a means to systematically identify, prioritize, and resolve the root causes of these cumulative injuries.

Jan 1, 2007

By Charles Janin, HENNEN JENNINGS

Many articles have been written on the general principles and details of gold dredging, a but it is not possible within the limits of this paper to recapitulate them, and it is thus necessary to assume some knowledge of this literature by the readers of this paper. Although the purpose of this paper is to describe gold dredging in Montana, a brief mention of some early appliances used in New Zealand, Australia, and California may serve as a world-connecting link in our consideration of the development of gold dredging. DREDGES EARLY USED IN NEW ZEALAND, AUSTRALIA, AND CALIFORNIA. Spoon dredges operated by hand were tried in New Zealand on rich spots in the Clutha River with some success as early as 1865. A dredge of this kind is shown in Plate I, A. In 1870 a modification of the spoon, operated by steam and being thus a primitive steamshovel dredge, was worked in New Zealand. Steam-shovel dredging was attempted in California as early as 1888 and 1893, and with some success in later years. The elevator gold dredge with endless bucket chain was put into operation in New Zealand in 1882. Plate I, B, illustrates a type of this dredge operated by current wheels. Plate II, A, shows a steam-operated dredge of this class, also started in 1882. In 1897 R. H. Postlethwaite, connected with the Risdon Iron Works, San Francisco, introduced the dredging practice of New Zealand into California. The first dredge built sank in the turbulent current of the Yuba. The second at Oroville, owned and operated by W. P. Hammon, proved effective and was the start in California of successful gold dredging. Since then the growth of the golddredging industry in California has been so rapid that the gold output from dredges in that State exceeds that of all other States in the Union, and, in fact, of any other country of the world, the value of the gold produced in California by dredging from 1897 to the end of 1914 having been about $71,000,000.

Jan 1, 1916

By Mokka Rao, Arturo Valles, Jose Rodríguez

"This paper shows a mathematical model based on finite elements, applied to bottom poured shell ingots of C.V.G. Sidor Plant. The model was used as a strategy to determine the thermal effects that are produced when solidification conditions are modified without interfering with the production process. The modification consisted of placing a thermal insulator on top of mould.The results obtained by the model indicated that the solidification time increases with insulator on base of the mould. With these results a significant number of casts were run with and without insulator. Latter by means of a metallurgical analysis it was determinated that the ingots cast with insulator reduce the level of non-metallic inclusions and the presence of internal blistering in seamless pipes.IntroductionThe process of fabrication of seamless pipes in SIDOR involves various steps of processing, such as heating the ingots, fabrication of the prelaminated, fabrication of the bored pipe, lamination of the pipe by passing through the pellegrine mill, heating the pipe in a walking bean furnace and final calibration through a calibrator mill. The material utilized for producing these pipes is provided entirely from a electrical arc furnace and casted ingots, especifically, from the superintendence of bottom pouring.The process of bottom pouring consists of positioning twelve moulds of diameters 415, 480 or 505 mm over a plate of grey cast iron in which exists a system of communicating vessels. The ingots are distributed around a central duct from which the steel flows down and filling gradually, each one of the moulds (Fig. 1)."

Jan 1, 1997

By E. Hinton, L. Bloomquist

"This paper describes a guidance system for autonomous underground mining vehicles, which does not require any infrastructure or inertial positioning systems to aid the guidance process.BackgroundINCO Limited mines approximately ten million tons per annum through 12 operating mines in the Sudbury, Ontario, area (Fig. 1). With challenges from operating in a cyclical marketplace as well as new technologies making alternative nickel ores more competitive to refine, the Mines Research department embarked on a strategy that pointed toward automation as a tool to help the company become even more economical in mining.The mining industry has been looking for ways and means to mine orebodies more and more inexpensively. Automation and the lessons learned from manufacturing had a great influence in the direction of research at INCO Limited over the past ten years. Guidance systems have evolved over the years but the majority of commercially available systems rely on some form of infrastructure. This, in part, has caused some resistance from operators to install and maintain automated or semi-automated systems for guidance of underground machinery.Internal industrial studies cited travel time to and from the workplace as one of the major time sinks in the shift of underground miners. Depending on the mine, it may be as much as two hours moving in and out of an area. Some work areas have accommodated this by having “hot changes” at the work place. However, at some point in time, there are two people tasked with the same job and on site at the same time to make this overlap occur.Tele-operation of underground hard rock equipment eliminated this overlap and also provided a comfortable environment in which to work. By taking advantage of the communications network installed, the miners proved that they could operate three machines with relative ease. This was accomplished by a vision-based, “painted line,” autonomous guidance system termed the light rope system.With a few years’ experience with the system, some issues have arisen, including the cost of the rope itself (Fig. 2).The vehicle’s route is limited to the paths defined by the light rope, and a system of switching power to the light rope to select different routes is required. The rope itself is subject to damage from nearby blasts. Also, the system offers no obstacle detection; the vehicle may be switched off as a means of shutting the machine down thus protecting personnel in the area."

Jan 1, 2001

A real Dorothy Dix title has been selec- ted for this paper. It has the advantage, however, of being capable of being interpreted in many different ways and hence I can select my own approach. You probably are thinking that this topic would be more appropriately handled by an Accountant. I wish to make it clear at the outset that I am not skilled in the sometimes mysterious ways of Accountants - likewise that profession frequently has difficulty in pinning down economists. We have our own strange ideas about profits, marginal efficiencies, cost/benefit analysis etc. What follows is in the main a mixture of two disciplines, probably in a form that few of the purists from either side would accept. Nor do I expect the reader to accept my own prejudices. The paper is designed to stimulate thought and discussion'on the subject. Emotive words such as "profit" and "loss" make for wide differences of opinion. At the time of writing there is a surprising degree of acceptance of the viewpoint that profits in Australia are too low and one is tempted to make this point of near agreement a starting Point.

Jan 1, 1975

By G. A. Moruzi

Two sulphide dust secondacy explosions have occurred in the mines of the SUdbury operations of Falconbridge Ltd. during the past 18 months. 'Ihe main similarity between the occurrences is that they both happened in vertical crater retreat blasthole stopes. A relatively high p:,v.tier factor was noted in both instances. other details are enumerated and examined, as well as some results of tests done by Noranda Research on company ore samples.

May 11, 1988

IT has often been stated in the past that the materials known as inert fillers were merely adulterants nsed in the manufacture of paint, and that their purpose was to cheapen paints made from more expensive pigments, such as zinc oxide or white lead. In recent years, however, practical tests in various parts of the world have proved that many of the inert fillers, when used with wisdom, possess very definite and advantageous properties.Another oft-repeated statement which had a far-reaching effect in the past, and which is not without influence to-day, is that the very best paint must always be made from a pure pigment, without admixture with either a fellow pigment or an inert filler. Both or either of these statements may be true in a few isolated instances, but for the vast majority of ordinary painting conditions there is an abundance of experimental evidence to prove that neither is true.With the desire to further investigate these points and po 'determine the best combination of pigments and fillers for use as an outside white paint on plant buildings, a number of panels were prepared in the laboratory of this company.

Jan 1, 1924

By C. M. Jones

Cyprus Sierrita Corp. has developed a training program that has led to several significant improvements in safety performance and productivity. Truck productivity has increased 6% as measured by truck cycle times. Increased skill levels and awareness on the part of the mine's operators are due to the new training effort. Costs associated with productivity training have been about $185,300. This includes program development and execution costs, as well as lost productivity during the training itself. These costs are offset by $1.9 million in savings attributable to the increased skill levels of technicians due to the training effort. Cyprus Sierrita is a subsidiary of Cyprus Amax of Englewood, CO. The company operates a copper and molybdenum mining and processing facility south of Tucson, AZ, near the town of Green Valley. The Cyprus Sierrita operation produces about 109 kt/a (240 million lbs/ year) of copper, 11.3 kt/a (25 million lbs/year) of molybdenum, 31.1 t/a (1 million oz/year) of silver and 1.8 t/a (4,000 lbs/year) of rhenium. The opera¬tion employs 770 people at the site. About 200 of these employees work in the mine operations. Mining at Sierrita uses standard open-pit techniques. Crews of 43 people rotate on 12-hour shifts. Hourly technicians are nonunion and do not use rigid job classifications to define pay. Rather, the system is designed to pay employees for what they are able to do. Administering this effort requires that training opportunities are provided to those people who desire them. Successful training opportunities al¬low people to gain skills. The more skills an employee can demonstrate, the higher his or her "tech level." A technician's pay is commensurate with his or her tech level. Much of Sierrita's training in past years concentrated on building basic

Jan 1, 1998

In 1970, the U. S. Bureau of Mines contracted with Theodore Barry and Associates, a management consulting firm, to perform a one-year industrial engineering study of working-face hazards in underground bituminous coal mines. The field data was accumulated from industrial engineering observations in fifty underground mines. Supporting data for the analysis was derived primarily from the Bureau's fatal accident reports for the years 1966 through 1970. This report, Industrial Engineering Study of Hazards Associated with Underground Coal Mine Production, consists of three main parts: 1) The Fatal Accident Reports Analysis, 2) The Industrial Engineering Analysis, and 3) Multiflow Process Charts and Standard Time Data. The Fatal Accident Reports Analysis (Volume I, Section II) is based upon individual USBM fatal accident reports for 1966-1970. These were read, coded and computerized in terms of 84 significant variables. Cross-tabulations of these variables have been used to identify major underground hazards and to quantify significant causal factors. A very strong relationship was found to exist between fatal accident occurrences and low task experience. This led to a recommendation for formalized training, certification and supervision programs for miners. Victim compliance with federal regulations, mine regulations and supervisor instructions was analyzed, indicating that supervisors provide the most crucial communication link to workers. Thus, every attempt should be made to ensure the competence of immediate supervisors in the industry. Analysis of roof fall variables revealed a fatal propensity on the part of the miners to work under unsupported roof or under support conditions that are marginal. The technical approach to the problem is to make it physically impossible for a miner to work under these conditions; the behavioral approach is to ensure adequate training and develop proper safety attitudes among the miners. The Fatal Accident Reports Analysis revealed a need for normalizing data to interpret the results more accurately.

Jan 1, 1971

By Leo F. Reinartz

Part II of a four-part series on the history of steelmaking in the US, points out the inadequate safety and living conditions that existed in steel mills at the turn of the Century. Also defined are furnace and process developments. OPERATIONS in steel plants today are highly mechanized. Men work in light, clean, orderly melting shops, making it difficult for old timers to convince young men that primitive, hazardous conditions existed in steel plants at the turn of the century. Working conditions then were very poor as compared to present day standards. In small plants especially, sanitary, locker, and washroom facilities, first-aid practices and stations were un- known Accidents were frequent and severe. Workers had a fatalistic attitude toward getting hurt. He who had an accident was looked upon as a hero. A dirty bandanna often served as a bandage. Infections were frequent. Electric cranes were in their infancy and broke down often Cables had not as yet replaced chains. Pig iron and scrap iron were loaded by hand in the stockyard, and stockyard locomotives were un- known; mules served as the usual motive power. It was not unusual to see recorded a delay of ½ hr in charging a furnace because of a balky mule. Furnace operations A few plants had primitive charging machines, but most furnaces were charged by placing scrap or pig iron on the paddle of a long peel, which rested on a bar across the furnace door opening. Laborers at the handle end of the peel, using the bar as a fulcrum, would heave the material into the furnace by a down and sideward motion of the peel handle. In time they became expert in placing these materials in the furnace, but it was hard, hot work, and a long time was required for charging. Cold charges of 25 tons required more than 12 hr for melting and re- fining the steel. Ports, doors, and frames were not water cooled. The charging and working area in front of the furnace was covered with steel plates. They were hot and often warped by the intense heat of the un- insulated checker chambers directly below. In the summer, working conditions on the charging floor were almost unbearable. Silica refractories were of poor quality. Because of this, and the inadequate training of furnace men in fuel control and furnace operations, roofs, front and back walls, and ends burned out rapidly. Dolomite machines were unknown; consequently, furnace banks and hearths were fettled with dolomite by the use of hand shovels. The round system required six or more men. Each man took a shovelful of dolomite and, in his turn, deposited it on the back wall and bank by a dexterous forward swing and twist of the shovel. The upward swing of the shovel partially protected his face from the searing heat of the furnace coming out through the wide-open door. Considerable skill and stamina were required to do this job properly. Reverse valves, usually of the cast-iron butterfly type, were located below the charging floor. They were operated by long levers on the charging floor level men they became warped, because of heat and abuse, great strength and skill were required to reverse them. Furnace operations were difficult. The quality and quantity of producer gas coming from irregularly stoked, hand-operated gas producers was uncertain and unreliable. Furnace Linings and ports were quickly burned out. Poor bottom and side-wall refractories, indifferent and inexperienced crews, as well as irregular re-

Jan 1, 1961