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By Newell Alford

AT its meeting in the fall of 1937, the Executive Committee of the Coal Division considered the growing scarcity of young engineers entering coal mining with serious intentions. This scarcity was the cause of con-siderable alarm and a committee consisting of C. T. Hayden, E. A. Holbrook, C. E. Lawall and L. E. Young, with the writer as chairman, was appointed to gather factual data on the current trend. A questionnaire1 was designed and mailed to the heads of the 60 mineral technology schools listed by Prof. W. B. Plank in his article in September 1937.2 Replies were received from 46 institutions, not all from heads of coal-mining courses but all from men that at one time or another have had experience with some kind of coal-mining curricula and know current student impressions. Our committee is indebted to all of these gentlemen for their cooperation. Our committee hoped by this means to quickly reach the root of the trouble and make a set of comprehensive recommendations to the Coal Division for relieving the industry immediately from the growing dearth of youth who yearn for coal-mining careers, but the condition is more serious than at first diagnosed. We must now refer the question back to the Coal Division, with the recommendation that the Division get the industry's permission for still another major operation on its frame of mind. In addition to 10-year statistics on the first pay received by graduates in coal mining and other technical work, we requested enrollment data for 20 years from all schools with either mining engineering or mineral technology curricula. Nine leading questions were also plied, as shown in the Appendix. Every one of the answers was significant and inter-esting. Fortunately, we encountered positive frankness that was extremely helpful.

Jan 1, 1938

By Dr. Hans Von Höfer

APART from the hypothesis of a .cosmic origin (which failed of acceptance because it was not adequately supported by facts), the only important controversy concerning the origin of petroleum has been, for a long time, between the advocates of inorganic and of organic origin respectively. Each of these theories has had a long history of development, and is still being perfected, under the influence of two causes: (1) the increasingly extensive and thorough study of the oil-fields (of which new examples are periodically discovered and opened); and (2) the progress of synthetic experiments devoted to this question. Moreover, the advance in our physical and chemical knowledge of the properties of this peculiar natural product has necessarily modified all criticism of conflicting views. I. THE HYPOTHESIS OF INORGANIC ORIGIN That the notion of an inorganic origin of petroleum, first set forth by Berthelot in 1866, and afterward ingeniously developed and formulated by Mendelejeff, should thus have proceeded chiefly from chemists, is quite natural; for the question was one of possible chemical processes in the earth's interior, and of imagined chemical reactions to be, verified by experiment. Hypotheses of this kind were suggested by many chemists, of whom two, P. Sabatier and J. H. Senderens, may be specially named by reason of their highly interesting chemical experiments. Among geologists, Mendelejeff's hypothesis was received at first with much interest and favor; for it rested on the assumption of a central terrestrial mass of iron carbide, and the geologists had good reasons for adopting that assumption. Yet comparatively few of them attempted to furnish geological proofs of the hypothesis: the majority either silently believed in it, or for one or another reason rejected it altogether.

Jan 5, 1914

By Newell G. Alford

At its meeting in the fall of 1937, the Executive Committee of the Coal Division considered the growing scarcity of young engineers entering coal mining with serious intentions. This scarcity was the cause of considerable alarm and a committee consisting of C. T. Hayden, E. A. Holbrook, C. E. Lawall and L. E. Young, with the writer as chairman, was appointed to gather factual data on the current trend. A questionnaire1 was designed and mailed to the heads of the 60 mineral technology schools listed by Prof. W. B. Plank in his article in September 1937.2 Replies were received from 46 institutions, not all from heads of coal-mining courses but all from men that at one time or another have had experience with some kind of coal-mining curricula and know current student impressions. Our committee is indebted to all of these gentlemen for their cooperation. Our committee hoped by this means to quickly reach the root of the trouble and make a set of comprehensive recommendations to the Coal Division for relieving the industry immediately from the growing dearth of youth who yearn for coal-mining careers, but the condition is more serious than at first diagnosed. We must now refer the question back to the Coal Division, with the recommendation that the Division get the industry's permission for still another major operation on its frame of mind. In addition to 10-year statistics on the first pay received by graduates in coal mining and other technical work, we requested enrollment data for 20 years from all schools with either mining engineering or mineral technology curricula. Nine leading questions were also plied, as shown in the Appendix. Every one of the answers was significant and interesting. Fortunately, we encountered positive frankness that was extremely helpful.

Jan 1, 1938

By G. D. Tranter

The importance of ladle and teeming practice and its relationship to the yield and quality of the product has focused considerable attention on this phase of open-hearth operation. Inherently bad steel cannot be perfected by manipulation during teeming, but through the proper handling of "off heats" serious losses, which in many cases arise, can be greatly minimized. Conversely, good steel can be ruined as a result of poor workmanship in the pit, and rendered unsuitable for application to orders where exacting surface and physical requirements are essential. Sufficient evidence has been secured to warrant careful investigation of pit operations when an abnormal number of basic defects develop in the semifinished product or are found on the inspection table. This paper is written from the standpoint of the problems involved in making satisfactory ingots for sheet rolling. Furthermore, since rimming steel is almost universally used for manufacture of sheet, the data presented herein refer particularly to that type of steel. Going back some 30 years in open-hearth history, the word "pit" properly described the hole into which the ladle was lowered to receive the metal tapped from the furnace. The working space was necessarily limited, and the disposal of slag and metal overflowing the ladle or lost because of breakouts presented a serious problem. The equipment, of course, was rather crude in the light of present-day development. Often no ladle stands were provided, the ladle being hung on the crane beneath the runner. When delayed taps occurred, the ladle was often held in position for many hours, thus tying up pit operations and causing delays to adjacent furnaces. Because of crowded conditions, slag thimbles were not used and a network of cast-steel triangles and old tapping bars, placed before the heat was tapped, was the means for removing slag from the hole. Furnaces of different capacities were used

Jan 1, 1935

Endurance Properties of Non-ferrous Metals Discussion of the paper of D. J. McADAM, JR., presented at the Syracuse Meeting of the Institute of Metals Division and issued, as Paper No. 1506-E, with Mining AND METALLURGY, October, 1925. H. F. MOORE,* Urbana, Ill. (written discussion).-This paper says that the results of tests of some non-ferrous metals made at the University of Illinois and in the testing laboratories at McCook Field are abnormal when they do not agree with results obtained by the author. The writer can see no inherent reason why results of the type uniformly reported in this paper are any more normal. The knee of the stress-cycle, or S-N, diagram comes at different lengths of life for different metals. For steel, the knee occurs after from 1,000,000 to about 4,000,000 cycles, and for some non-ferrous metals not before 20,000,000 of 30,000,000 cycles. The writer can see nothing inherently abnormal in finding certain nonferrous metals for which the knee of the stress-cycle curve occurs at 1,000,000,000 cycles or higher. The writer has had experience with both the cantilever and the rotating-beam testing machine, and thinks that the chance of whipping action in the cantilever machine is a more serious handicap than the action the author has pictured. Furthermore, the writer questions whether the author has shown the existence of a clearly marked and definite endurance limit for all the non-ferrous metals he has tested including the following: Nickel (CT and A-16, Fig. 1), monel (CS-5.5 and BK, Fig. 2), bronze (F and CK, Fig. 4), aluminum bronze ( BJb-1, Fig. 6).

Jan 12, 1925

By Alfred F. Brainerd

Some fifty years ago, iron-ore was discovered near the town of Sheldon, Franklin County, Vermont, in a vein out-cropping on a knoll near Black Creek, which empties into the Missisquoi River a couple of miles away. A short time after this discovery, the owners, Mr. TV. 0. Gadcomb and Hon. Lawrence Brainerd, both of St. Albans, commenced mining (mostly by open cut), and also erected a Catalan forge, from which iron blooms were produced, most of which were worked into bar-iron and used in the neighborhood of the forge, while some were shipped by Lake Champlain to Troy, Albany and New York. But by reason of the lack of any railroad connections, and an insufficient demand for the blooms, this forge was subsequently abandoned, and the material used in its construction removed to other places. Mr. Keith, of Sheldon, used for many years a mixture of this ore with bog-ore from Swanton, in a charcoal blast-furnace, the product of which he consumed partly in his own foundry, shipping, however, a considerable amount to Troy and New York. Accurate data as to this enterprise are not at hand. The same vein has since been traced for some 20 miles, and some prospecting has been done 011 its outcrops at Berkshire, Enosburg and a few miles east of St. Albans; but the vein being small, only a few car-loads of ore were taken out from these places. The commencement of the St. Albans Iron and Steel Works in 1872, and the erection in 1877 of a ten-ton Siemens open-hearth furnace for the manufacture of steel rails, opened a new use for this ore. The furnace-charge consisted of pig-iron, old mils, steel scrap, and magnetic iron ore, added towards the close of the heat. The ore

Jan 1, 1885

By Peter Nalle

12.3-1. Reporting. NEED. It seems almost unnecessary to comment on the need for reporting research and development results and activities, and yet much of the difficulty and misunderstanding surrounding a Research and Development (R&D) group results from poor or nonexistent reporting. Certainly no evaluation can be made without reports of results or plans. It is as important to report accurately and fully for the department's own use as it is for external use. Research unreported might as well be considered research undone. This section will discuss, in part, the need for reporting, the general types of reports which may be generated to satisfy the need, and finally, the evaluation of a project as judged by various commonly used standards. PURPOSE. Some specific observations might be appropriate concerning the reporting of R&D results. The requirements and background of the group receiving the report must be considered. A particular report is usually directed towards the background of a particular group, such as ((technical," "operational," "financial," or "marketing." It is essential that the emphasis and coverage be geared to the training of people receiving the report. It should be obvious that the financial department will be less interested in the technical details of the process and more interested in the capital funds and tax implications involved in the project. Operating personnel will be greatly interested in the effects of a new method on mining plans, and so on. This does not mean that the reporting in any way should slight pertinent details, nor should a patronizing attitude be assumed by the writer. However, it is essential that the needs of the reader be recognized. For reports that might have large and varied distribution, it is often feasible to group, either as sections or appendixes, the special details and information of interest only to certain functions within the organization. A

Jan 1, 1968

By Daryl L. Gusey, John T. Neubert, Matthew A. Sares

The Colorado Geological Survey completed an inventory of environmental degradation associated with abandoned and inactive mines on National Forest System lands in Colorado. In the course of the inventory, areas with naturally occurring acid rock drainage were also noted. Approximately 18,000 abandoned mine- related features were inventoried, including about 900 features that are considered significant enough environmental problems to warrant further investigation. Water quality data, such as pH and conductivity were gathered at all features where water was present, such as draining adits, seepage at the toe of dumps and tailings, and standing water in shafts. Samples were taken where field tests indicated low pH andlor high conductivity, including several areas with naturally occurring acid rock drainage. Samples were analyzed for dissolved and total metals, and for selected anions. All mine locations and data collected by the field geologists were entered on field forms and, subsequently, into a computer database and GIS format. With the information provided by the inventory, the Forest Service, in cooperation with other agencies, has been able to prioritize abandoned mines for reclamation. In most cases, cleanup is approached on a watershed basis. Mines in priority watersheds have been selected for reclamation first. Watersheds where studies prerequisite to cleanup are occurring include the upper Anirnas River, Willow Creek (tributary to the upper Rio Grande), Chalk Creek (tributary to the upper Arkansas River), the Uncompahgre River, and the Alamosa River. During the inventory, evidence of naturally occurring water quality degradation was found in areas where little or no evidence of mining activity exists. These areas include the upper Alamosa River, the Middle Fork of Mineral Creek, Peekaboo Gulch, and Handcart Gulch. Water from these natural sources has been found to significantly exceed Colorado water quality standards for several metals.

Jan 1, 2000

By A. C. Fieldner

The usual analytical determinations made in analyzing coal are comprised in the proximate and ultimate analysis and the determination of calorific value. The proximate analysis includes determinations of moisture, volatile matter, fixed carbon and ash; the ultimate analysis determinations of carbon, hydrogen, oxygen, nitrogen, sulfur and ash. The proximate analysis is an empirical process, and the results, obtained, especially for volatile matter and fixed carbon, are materially influenced by the method of conducting the determinations. This fact must be kept in mind in comparing coal analyses from different laboratories for classification purposes. Unless these laboratories have followed the same standard methods, differences due to variations in the analytical methods may, in some cases, be large enough to change the classification of the coal. It is unfortunate that the determinations of volatile matter and fixed carbon, which are most used in coal classification, are the two that are subject to the greatest variations. Moisture comes next in the scale of variation. The ultimate analysis is less influenced by method, since it comprises the determination of definite chemical elements. However, even the ultimate analysis is subject to errors, due to inorganic carbon from carbonates and to inorganic hydrogen from water. For these reasons it is evident that the Committee on Coal Classification must be informed on the evolution of methods of coal analysis in America and the average differences in analytical results that may be expected from variations in methods. The committee should be informed also on which methods should be accepted as standard for classifying coal and on the magnitude of the differences in results that may be expected from duplicate samples of the same coal sent to different laboratories for analysis by the same standard methods. It is the purpose of the present paper to provide this information. The subject will be discussed under the following main heads:

Jan 1, 1930

By Hsun Hu

NOT much data are available in the literature on textures in cross-rolled metal sheets. Among the body-centered-cubic metals, a few investigators have studied the preferred orientations developed in cross-rolled and in subsequently annealed molybdenum specimens.1-4 Semchyshen and Timmons5 onstructed complete pole figures for the cross-rolled and subsequently annealed arc-cast molybdenum. They used the conventional photographic method. Similar data on cross-rolled iron are still lacking. In view of the fundamental importance of iron as a basic metal for magnetic alloys and many industrial steels, the present investigation was undertaken in an attempt to understand more about its properties. The material selected for the present work was of high purity, and the textures were determined by the Geiger counter spectrometer technique, which permits the construction of quantitative pole figures. Experimental Procedure The material used for this investigation was NRC (National Research Corp.) high-purity, gas-free iron. The total gas content (N2 + O2 + H2) given was less than 0.026 pct, and the carbon content, less than 0.005 pct. Spectrographic analysis of a 2 in. cast ingot showed the percentage of metallic impurities as 0.0004 pct Cu, 0.0002 pct Mg, 0.001 pct Mn, 0.01 pct Ni, and 0.006 pct Si. A 1 in. thick slice was cut off from the 2 in. cast ingot. It was hot-forged at 850 °C to destroy most of the cast structure. Surface scale was removed by milling the forged piece to a size 2 in. long, 1½ in. wide, and ¾ in. thick. After normalizing at 915 °C for 15 min, the piece was alternately cold-rolled 40 pct and annealed at 750°C in hydrogen to a final thickness of 0.165 in., with a resulting uniform grain size of 0.1 mm.

Jan 1, 1958

By Stanley W. Sundeen

2.3-1. Introduction. The subject-"Preliminary Evaluation of Coal, Metallic and Industrial Mineral Deposits for Surface Mining'-seems at first glance to be definitive and not likely to be misinterpreted. Nevertheless, there are widely divergent opinions as to what is meant by "preliminary" and even as to what is meant by "evaluation." Some definition and qualification is necessary in order to provide a readily recognized basis for discussion. Evaluation evokes the idea of organizing extant data and judging its significance especially in the economic sense. It also may evoke the concept of the physical processes of acquiring the data that will characterize the deposit such as the geologic mapping, drilling, etc. Castle (5) considers that evaluation may embrace psychological aspects wherein human traits as, for example, over optimism might cause the evaluator to overlook obvious project weaknesses. In this chapter, evaluation is discussed primarily from the viewpoint of economically appraising a project from data available at a given point in time. The qualifying adjective "preliminary" is not easily defineable. In fact, some kind of evaluation proceeds, if not continuously, intermittently over the full span of exploration and early stages of development of a deposit. Bailly (1) comments: "Sometimes, before starting exploration in new areas or countries for a given commodity, we establish models to define what minimum combinations of re- coverable grade and tonnage are needed to give the minimum acceptable rate of return established by corporate policy. Then, before starting physical exploration in any target area we try and guesstimate optimistically what best 'geometry-grade-tonnage' can be expected. If these are acceptable in light of above minimum combinations, exploration is started as soon as funds are appropriated for the target area.''

Jan 1, 1968

By W. L. Austin

The advance made in recent times in this branch of metallurgy is indicated by the attention the subject is receiving from important American copper-producing companies. Reference to the files of publications devoted to the mining industry discloses that some 20 American companies are actively investigating the amenability of their ore, or other material, to leaching methods, and that plants of varying capacities up to 10,000 tons per day arc under construction or are projected. Several leaching works are in commercial operation. It has been frequently pointed out that no method of leaching is universally applicable, for the reason that each ore differs in some particular from apparently similar ore found elsewhere, and also because local conditions are rarely the same even where the ore closely approximates in character that being worked at some other point. For this reason the older companies are approaching the matter in a conservative manner, experimentally determining for themselves the salient features in each instance. In considering a leaching proposition three factors at once fix the attention: (1) disengaging the metal from mineralized forms in which it is found in nature; (2) recovering the metal in a commercial state after it has been dissolved; (3) the apparatus best adapted to carrying out the several operations. Bringing the Metal into Solution This feature.has been found to present no serious difficulties. Numerous solvents for copper are known, and it has been repeatedly demonstrated on a commercial scale that from 80 to 90 per cent. of the metal contained in an ore can be rapidly brought into solution. It is interesting to note, however, that all of the companies above referred to have selected sulphuric acid as the basis for a lixiviant. Where oxidized ore practically free from precious metals is treated simple leaching with

Jan 1, 1915

By Harold L. Bare, Frank R. Barnako

Coal mining historically has been a. hazardous occupation but, in recent years, tremendous progress has been made in reducing accidental coal mine deaths and injuries. The purpose of this chapter is to discuss the basic principles of accident prevention as they are related to coal mining. Accident prevention fundamentals are no different for coal mining than for any other type of work. The fundamentals apply to all industries. Construction workers may be struck by falling tools and materials, and miners may be struck by falling slate and coal. Sailors may be trapped by shipboard fires, and miners may be trapped by mine fires. Railroad brakemen may lose hands and fingers positioning couplers, and miners may lose hands and fingers positioning couplers. Many other examples could be cited, but the point is that accidents that happen in coal mines are basically similar to accidents that happen in other industries. Thus, the basic principles for preventing accidents apply in coal mining as they do in any other type of work. COAL MINE ACCIDENT EXPERIENCE The US Mine Safety and Health Administration (MSHA) is the main source for accident experience data in coal mines. Coal mine operators are required, by law, to forward to MSHA monthly the number of fatal and disabling injuries, man-hours worked, and tons of coal mined. This information is compiled and published quarterly, with annual summaries, by MSHA. Trends in the number of fatalities and fatal injury rates are shown in Fig. 1. Major coal mine disasters, with number of miners killed, and dates of coal mine safety legislation are shown in Table 1. The fatal and disabling injury frequency rates for the coal industry are shown in Fig. 2.

Jan 1, 1981

By Donald L. Katz, Michael J. Rzasa

With greater effort being devoted to the discovery of new oil and gas reserves and a consequent increase in bottom hole pressures due to greater drilling depths, the phase relationships of hydrocarbon fluids at pressures above 10,000 lb psi are becoming increasingly important. The present paper discusses the results of research with a windowed cell on a methane-Kensol 16 system to pressures of 25,000 Ib psi and temperatures to 260°F. Kensol 16 is a commercial high narrow-boiling-range oil. It is shown that for the temperature range of 60 °F to 260 °F, this particular system exists in two phases to pressures of approximately 14,000 lb psi, and data are presented giving the relative amounts of liquid and vapor phase? coexisting under these conditions. Partial phase diagrams are shown for six different mixtures of methane and Kensol 16, three of which include the critical region. In contrast to mixtures composed of substances of fairly close volatility. critical opalescence was noted for as much as 200°F of the critical temperature. The critical locus of the methane-Kensol 16 system was estimated and the conventional pressure-composition and temperature-composition diagrams were prepared. From these, the equilibrium vaporization factors for methane and Kensol 16 were estimated for temperatures from 60 °F to 700 °F and to pressures above 12,000 lb psi. The relations of this study to petroleum production problems and other phase equilibria research are discussed. INTRODUCTION A knowledge of the physical behavior of naturally-occurring hydrocarbon mixtures is fundamental to a thorough treatment of nearly all operations involved in the recovery, refining, and transportation of petroleum. The operations may involve the applications of phase relationships, and the relative

Jan 1, 1950

By John W. Brauns, David H. Orr

9.1-1. Description and Basic Function. A conventional railroad haulage system for a surface mine performs the function of transporting the ore and/or waste out of the pit to a crushing plant or dump. Trains consisting of a locomotive and gondola or side-dump care suitable for loading by power shovels are used. Gondola cars are restricted to hauling ore as a rotary dumper is required to unload them. Side-dump cars are more versa- tile, being satisfactory for carrying both ore and waste; but because of their additional dumping mechanism they are likely to be more expensive to maintain (12). Also they weigh up to two times as much as a flat-bottom car of the same capacity, and, therefore, fewer cars can be hauled per train. Standard-gauge track is most commonly used. Track systems incorporate temporary track of low quality in areas where moves are frequent and permanent track of high quality on main lines. Rail haulage enabled open pit mining to establish its reputation, for efficiency. Prior to World War II it was the principal type of transportation used in large pits. Other successful surface mine haulage methods have been developed since that time. These have served to supplement railroad transportation, permitting selection of a method that is best adapted to the peculiar requirements of each mining project. 9.1-2. General Applicability and Controlling Physical Conditions. For handling rough rock, the shovel-train system is unexcelled (6). The ideal application is in a physically large, but not excessively deep, open pit mine from which the coarsely blasted ore and waste must be transported distances in excess of three miles. If, in addition, a high production rate is to be maintained, railroad haulage will probably afford a lower cost per ton transported than will any other haulage method. Relatively gentle

Jan 1, 1968

By Gary W. Kramer

The Bureau of Mines has developed a rapid analytical method for the determination of anions by ion chromatography (IC) in phosphate rock mining materials and cement kiln dust (CKD). The procedure employs an Na2C03 fusion of the sample, followed by a water extraction that allows direct injection of the sample into an ion chromatograph without separator column poisoning by the transition metal ions. Fluoride (F-) and phosphate (P043-) were determined in 24 phosphate rock processing and waste material samples by the IC method. The results were compared with a pyrohydrolytic distillation-titration method for F-and a colorimetric procedure for P043-. Excellent analytical agreement was obtained for F-and p043-values determined by IC and the comparable wet chemical methods. Fluoride values ranged from 0.3 wt-pct in the filter cake to 3.6 wt-pct in phosphate rock concentrate. Phosphate values ranged from 1.2 wt-pct in the filter cake to 33.8 wt-pct in the rock concentrate. Fluoride, chloride, phosphate, nitrate, and sulfate in several CKD samples were determined by the IC method and standard wet chemical techniques. Excellent agreement was obtained between the two methods for all anions. A total of 113 CKD samples from all areas of the United States was analyzed by the IC method. Fluoride values ranged from <0.01 to 0.36 wt-pct. Chloride values ranged from <0.01 to 12.5 wt-pct. Sulfate values ranged from 0.41 to 31.6 wt-pct. Phosphate and nitrate were detected in only about 25 pct of the samples at >0.02 wt-pct. Maximum phosphate and nitrate values were 1.0 and 1.6 wt-pct, respectively.

Jan 1, 1982

By Roy H. Grau, John C. LaScola

"This Bureau of Mines report contains a tabulation of methane emissions during 1980 for all coal mines located in the United States with emissions greater than 0.1 MMcfd. Listed for each mine are methane emission quantity, location, and coalbed. The report also compares records of 1975 and 1980 and describes relationships between emissions in 1980 and the Bureau's coalbed gas content data on 11 mines.INTRODUCTIONMethane gas is a threat to safety in underground coal mines. Research by Government and industry has led to great gains in reducing methane gas ignitions and explosions. The development of advanced methane control techniques is necessary for the safe operation of more gassy mines and the implementation of rapid mining techniques.As part of this research, the Bureau of Mines has surveyed total methane emission data from underground bituminous coal mines in the United States and tabulated emissions from mines producing over 0.1 MMcfd of methane. This report is an update of similar studies previously described in Information Circulars 8733, 8659, and 8558 (2-4).3The data from 1980 were compiled from Mine Safety and Health Administration (MSHA) records of air quality-quantity inspections made quarterly at each mine. The inspections involve measuring airflow and collecting air samples in the main returns. From these data, an average methane emission is calculated and used to represent the daily mine emission for each quarter. The methane emissions given in this report are the averages of the four 1980 quarters and do not include mine emissions from other sources such as degasification projects. Since a previous Bureau study showed that emissions from mines emitting less than 0.1 MMcfd represented only 2 pct of all emissions, 0.1 MMcfd was chosen as a lower limit for data collection (4)."

Jan 1, 1982

By M. Viswanathan, M. J. Jorgensen, N. K. Kittusamy

Operating heavy construction equipment is often associated with elevated rates of low back discomfort (LBD). However, there have been few formal studies that dealt with evaluating controls that can reduce the LBD among these workers. The objective of this study was to determine the effectiveness of using a continuous passive lumbar motion system (CPLMS) in reducing low back discomfort among operators of heavy earthmoving equipment. The CPLMS is an additional seat support that has a lumbar support bladder and a pump to provide cyclic inflation and deflation. Two groups of operators were identified as potential subjects for this intervention study, the intervention group with a mean age of 41.2 years and experience of 9.7 years used the CPLMS, and the control group with a mean age of 37.5 years and experience of 7.6 years did not use the CPLMS. Body part discomfort surveys were collected from both groups. In addition, the intervention group completed a CPLMS preference survey. The body part discomfort survey was collected up to eight days at three different times of the day. Results from the body part discomfort survey showed a decreasing trend the longer the CPLMS was used, for both the upper and low back region. A decreasing trend for the low back was also found comparing morning to evening discomfort scores across the days when using the CPLMS. When compared to their regular seat, 54% of the operators felt very comfortable in using the CPLMS, 36% of them wanted one for their equipment, and 54% showed interest in experimenting with the CPLMS for a longer time period. Results from this study indicate that the use of a CPLMS can effectively reduce the low back discomfort experienced by operators of heavy construction equipment.

By H. Shaw

IT is now generally recognized that the gravitational method of geophysical surveying is a valuable aid in elucidating the geological structure of the subsoil and enables the practical geologist to deduce the presence of useful deposits. The particular suitability of the torsion balance to the location of large and important subterranean structures has given rise to a wide. application of this method by many of the important oil companies in their search for future supplies, and so intense have been these efforts that little has been heard of the method in other connections, with the exception of occasional references to its application in the location of hidden deposits of metallic ores, salt and lignite, and a number of accounts of its use in the elucidation of geological structures. Its success in the location of salt domes is well known, and. establishes it as one of the most important of the geophysical methods, especially for the indirect location of oil. In the British Isles, however, no large occurrence of oil is likely to be revealed, and here the practical application of the gravitational method has been restricted almost entirely to the search for ores. This type of survey possesses well marked characteristics, and presents a gravitational problem that has necessitated the development of a special and probably unusual plan of campaign, full details of which it is hoped will shortly be published. The problems and difficulties encountered in this work are of necessity fundamentally related to those met with in the search for oil by means of the torsion balance, but they also possess several special and distinctive features which undoubtedly differentiate them from the obstacles confronting the oil prospector, and which call for special consideration and treatment.

Jan 1, 1928

By John M. McAnerney

In 1955, the U.S. Army started to experiment in Greenland with tunneling in glacial ice and later in frozen glacial moraine. By 1960, long adits and experimental rooms had been successfully excavated. Full mechanization with coal-cutting machinery was most efficient in ice but drilling and blasting were necessary in bouldery moraine. In 1963, the U.S. Army Cold Regions Research and Engineering Laboratory, (USA CRREL; redesignated U.S. Army Terrestrial Sciences Center July 1, 1968) started a tunnel in the frozen silt of central Alaska near Fairbanks. The original adit of 360 ft (109 m) was successfully driven in the permafrost by a twin-rotor tunnel-boring machine, the Alkirk Cycle Miner. The workings were enlarged in 1966 and 1967 by standard mining techniques in which jackhammers, steam points, and augers were compared. A mechanical coal cutter was tried to supplement drilling and blasting. In 1968, airblasting techniques were used successfully for breaking out the frozen silt. All mine products were loaded mechanically and hauled by self-dumping shuttle car. Pneumatic methods of transport were tried for both dust removal and for conveying blast products up to 3-in. maximum size. Studies of the effects of natural winter ventilation through a shaft showed that tunnel closure could be reduced by lowering the adjacent ground temperature. It is concluded that underground openings in frozen ground should be cut and maintained at well below freezing temperatures to hold deformation to a minimum. HISTORICAL BACKGROUND This chapter deals with aspects of tunneling not previously discussed in the conference papers in this book. The chief differences are that the three tunnels lie entirely within frozen material and are relatively small, since they were constructed mainly for research. The primary objectives of the research were to develop underground shelters for military per-

Jan 1, 1970