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By R. E. Zimmerman

The separation of fine sizes of coal from its impurities by means of various flotation methods has become of increasing importance in the coal industry. This, no doubt, will be even more so in the future as the quantity of high grade coal is depleted, particularly that used for metallurgical purposes. The purpose of this paper is to describe and report the results of research work done under the auspices of the Pittsburgh Coal Co. to determine the amenability of their bituminous fine sizes of coal to flotation, to investigate the value of various reagents and factors affecting their use, and compare the results between froth flotation and bulk oil flotation. Compared with the preferential flotation of complex minerals, or ores, the flotation of coal is comparatively easy. However, this statement should not lull one into the feeling that there are no special problems involved. For instance, the separation of coal from pyrite in high sulphur coals is still far from being 100 pet successful. Size consist has considerable effect on reagent consumption and recovery. Other factors will be described and finally it must be remembered that in the flotation of coal a low priced material is being treated and thus economic considerations govern more closely its application than is generally the case in treating other minerals. As a result of the research work done by the Pittsburgh Coal Co. on the flotation of coal, it was concluded that it was practical to clean the —48-mesh coal commercially by froth flotation and after several different types of flotation units and circuits were investigated by means of pilot plants, large scale units were installed at their Champion Nos. 1, 4 and 5 Preparation Plants for the cleaning of —48-mesh slurries. These large scale operations have been recently described by D. H. Davis.' C. P. Proctor and C. B. Carlson2 in their chapter on Froth Flotation of Coal in the AIME Seeley W. Mudd series book on Coal Preparation describe some of the practical applications of our Pittsburgh Coal Co. laboratory work in actual plant practice as well as summarizing part of the investiga-tional work. The author presents this paper, however, as a supplement to their reports, and records the basic research accomplished in the laboratory investiga-tional work as well as the results of experiments using bulk oil flotation. In presenting this work the author wishes to state much more work must be done in applying the principles of flotation to cleaning coal, especially in view of recent studies and practices in other mineral beneficiation fields. Methods of Conducting Laboratory Tests The bulk of the research work was conducted in the laboratory of the Champion No. I Preparation Plant. This plant has elaborate facilities for sampling and analyzing coal and proved to be an admirable location for the investigational work. Four types of laboratory flotation ma-

Jan 1, 1949

By B. Ramaswami, Y. Nakada, U. F. Kocks

Compression tests were performed on single crystals of aluminum, silver, gold, and a Ag-10 pet Au alloy, with height-to-width ratios from 8:1 to 1:1. As this ratio decreased, so did the amount of easy glide until, for cubic specimens of all the pure materials, it was entirely absent. Heterogeneity of deformation is proposed to he a major contribution to the explanation of easy glide in slender specimens. For comparison, one single-crystal cube of zinc was tested and showed a behavior very similar to that in tension. Beyond easy glide, tension and compression curves are very similar. It is concluded that, in this range, neither grip effects nor orientation change influence the work-hardening characteristics to any significant extent. (121) and (100) crystals of all materials had similar stress-strain curves in tension and compression, except that the stress level of the flat portion of aluminum (109 crystals at high strains mas somewhat higher in compression. These results are at variance with previously proposed mechanisms of orientation dependence by both Hosford and Kocks. The compression tests themselves are described in detail and it is shown that they are essentially frictionless and produce single slip when the crystal is suitably oriented. DEFORMATION in uniaxial compression does not necessarily give the same result as deformation in uniaxial tension, essentially because the boundary conditions chosen are practically always different. 1) The shape and size of the specimens are usually different, and any genuine effect of size on work hardening should thus influence the result. 2) The grip constraints are usually different and can vary substantially for different kinds of tests. If the compression specimen is a thin plate and the friction on the platen is large, the grip contraints are more serious than in tension and lead, in the extreme, to uniaxial strain rather than uniaxial stress. If the specimen is roughly cubical and the friction is low, the specimen is less constrained than in tension inasmuch as displacements in the contact face are allowed. 3) The orientation change of single crystals is of opposite sign in tension and in compression; it is furthermore different in detail, because the relevant orientation in a squat specimen is the normal to the contact face, whereas that in a slender specimen is the generator of the side faces.' The considerable dependence of work hardening on the initial orientation in tension would suggest that the orientation change should also be very important. 4) Finally, localized deformation instabilities found in tension tests, such as necking and Lüders band propagation, are not possible in squat specimens. This is, for some investigations, a favorable consequence of the large grip influence. Even if one is not interested in any of the effects mentioned above, compression tests are often desirable just because the specimens needed are so much smaller and sturdier. For example, they have been very helpful in the investigation of latent hardening by means of alternate longitudinal and lateral compression of cubes,* and for testing

Jan 1, 1964

By N. P. Goss

Asterism appearing in X-ray Laue diagrams is an extremely sensitive index of changes in the internal structures of individual grains of polycrystalline metals. It indicates the existence of various forms of subboundary structure or subdivision within the grain. The present viewpoint is that the grain is made up of lattice blocks having substantially the same size and shape.l-4 When these blocks all assume exactly the same orientation, the crystal is perfect and asterism is absent. Cleaves and Thompson5 observed that the hardness of iron is virtually constant over a range of grain sizes. It is quite possible that the subboundary structure caused this, and that the latter is just as important as grain size itself. While the experiments reported here are not conclusive, they do support this viewpoint. Metals can, under certain conditions, be prepared entirely free from asterism, but this preparation does not necessarily require long heating or slow cooling, as will be shown here. In this paper a distinction is made between mosaic and distorted grain structures but the difference is only a matter of degree. In a previous paper9 it was shown that the grains can become distorted even during heat-treatment. The block structure exists inherently, even in a perfect crystal; the size and shape of these crystallites, or lattice blocks, varies, depending upon a number of factors. Goetz, for example: has shown that a metal before crystallizing from the molten state must go through a paracrystalline phase with oriented groups of atoms about 10-l4 to 10-l5 c.c., or 10-15 cm. in size. These crystallites, or blocks, appear to survive the most drastic cold-working, for it has been shown, and more elaborately by Wood's recent work," that cold-working cannot reduce the size of these crystallites smaller than of the order 10-5 cm. The interesting correlation brought out by the experiments of Goetz and Wood is that the block size after severe cold-working is of the same order of magnitude as the groups that formed in the metal just before crystallizing from the molten state. The work of Ewald and Rennenger17 and the now classical experiments of Darwin and James12,13 all strongly suggest the existence of a periodic structure of crystal. lites smaller than the grain itself. Related to this effect is the appearance of veinlike markings in the microstructures. Ammer-man and Kornfeld,16 in their experiments, did not observe any evidence of veining in specimens of alpha iron annealed below A3 and believed that veining was not due to impurities in the iron, as Northcott16 suggested; veining was observed by them only in specimens annealed above A3. Hanemann,16 Schrader and Tangerding found that annealing in hydrogen did not diminish veining and so it could not be caused by oxides. They concluded that veining was due to a slight difference in the orientation of ferrite lattice blocks. This viewpoint is well supported by the evidence presented here.

Jan 1, 1941

By N. P. Goss

Asterism appearing in X-ray Laue diagrams is an extremely sensitive index of changes in the internal structures of individual grains of polycrystalline metals. It indicates the existence of various forms of subboundary structure or subdivision within the grain. The present viewpoint is that the grain is made up of lattice blocks having substantially the same size and shape.l-4 When these blocks all assume exactly the same orientation, the crystal is perfect and asterism is absent. Cleaves and Thompson5 observed that the hardness of iron is virtually constant over a range of grain sizes. It is quite possible that the subboundary structure caused this, and that the latter is just as important as grain size itself. While the experiments reported here are not conclusive, they do support this viewpoint. Metals can, under certain conditions, be prepared entirely free from asterism, but this preparation does not necessarily require long heating or slow cooling, as will be shown here. In this paper a distinction is made between mosaic and distorted grain structures but the difference is only a matter of degree. In a previous paper9 it was shown that the grains can become distorted even during heat-treatment. The block structure exists inherently, even in a perfect crystal; the size and shape of these crystallites, or lattice blocks, varies, depending upon a number of factors. Goetz, for example: has shown that a metal before crystallizing from the molten state must go through a paracrystalline phase with oriented groups of atoms about 10-l4 to 10-l5 c.c., or 10-15 cm. in size. These crystallites, or blocks, appear to survive the most drastic cold-working, for it has been shown, and more elaborately by Wood's recent work," that cold-working cannot reduce the size of these crystallites smaller than of the order 10-5 cm. The interesting correlation brought out by the experiments of Goetz and Wood is that the block size after severe cold-working is of the same order of magnitude as the groups that formed in the metal just before crystallizing from the molten state. The work of Ewald and Rennenger17 and the now classical experiments of Darwin and James12,13 all strongly suggest the existence of a periodic structure of crystal. lites smaller than the grain itself. Related to this effect is the appearance of veinlike markings in the microstructures. Ammer-man and Kornfeld,16 in their experiments, did not observe any evidence of veining in specimens of alpha iron annealed below A3 and believed that veining was not due to impurities in the iron, as Northcott16 suggested; veining was observed by them only in specimens annealed above A3. Hanemann,16 Schrader and Tangerding found that annealing in hydrogen did not diminish veining and so it could not be caused by oxides. They concluded that veining was due to a slight difference in the orientation of ferrite lattice blocks. This viewpoint is well supported by the evidence presented here.

Jan 1, 1941

By J. J. Gilman

THEORIES of fracture in metals have been based primarily on the dependence of fracture strength on grain size. This dependence was first observed by Masing and Polanyi.l These workers, as well as 0rowan12 and Davidenkov and Wittman,' thought the grain size could be equated with the crack size in the Griffith condition for crack propagation.4 In this way they could account for the observed proportionality between fracture stress and the reciprocal square root of the grain size. The chief results of recent investigations of the fracture strength of polycrystals are summarized in Fig. 1. Low for iron,5 Petch for iron,' Greenwood and Quarrel for zinc, Petch and Zein for zinc,' and Hauser, Landon, and Dorn for magnesium'' have all found that the fracture stress of a polycrystal is proportional to the reciprocal square root of the grain size. Also, they find that, for large grain sizes, the fracture stress lies near the extrapolation of the yield-stress curve determined at small grain sizes; where measurable plastic strain precedes fracture. Low9 has gone a step further and shown that, in Range 1, the fracture stress in tension is almost identical to the yield stress in compression for a given grain size. Homes and Gouzou, 10 and Low also have shown that, in Range 2 of Fig. 1, microcracks form when the yield stress is reached, but they do not cause failure until the stress reaches a much higher value. The fact that yielding always precedes fracture suggests that fracture is induced by plastic flow. A mechanism by which this might occur was first proposed by Zener.11 He pointed out that blocked dislocations would cause stress concentrations which might cause fracture. The blocking would be caused by grain boundaries. This idea has been developed by Eshelby, Frank, and Nabarro,12 by Koehler,13 and by Stroh.14 By means of etchpits blocked dislocations have been observed in brass by Jacquet,15 in zinc by Gilman,16 and in lithium fluoride by Gilman and johnston. The blocked-dislocation theory and the experiments that bear on it have been summarized by Mott.18 One of the strong points of the blocked-dislocation theory is that it can explain the grain-size dependence of the fracture stress in a natural way. However, Low9 has pointed out that the theory is not satisfying when it is considered quantitatively. Gilman10 also has criticized the theory and presented an alternative interpretation of the relation between fracture stress and grain size. Since the blocked-dislocation theory is not the only theory that can explain in the grain-size effect, it is necessary to find other evidence either to support or deny it. In this investigation the following points were studied: 1) If blocked dislocations normally cause fracture, then the fracture stress ought to be very high in the absence of plastic glide. Is it? 2) If dislocations must be blocked in order for metals to fracture, then certain types of grain

Jan 1, 1959

By G. E. Warner

This paper presents a review and analysis of a highly stratified Burbank sand waterflooding project in Osage County, Okla. Permeability values in this reservoir range from less than 0.1 md to nearly 3 darcys, and 90 percent of the permeability capacity is contained in approximately 26 percent of the reservoir volume. To date, the project has recovered 103 bbl/flood-acre-ft since waterflood initiation, which represents 50 percent of the total preflood cumulative and 12 percent of the original stock-tank oil in place (OSTOIP). The outstanding feature of this project has been the economical recovery of a sizable quantity of oil at water-oil ratios higher than those normally considered prohibitive. Nearly 70 percent of the recovery to date has been achieved at water-cut values greater than 95 percent. An ultimate waterflood recovery of 138 bbl/flood-acre-ft, or 67 percent of the preflood recovery and 16 percent of the OSTOIP, is predicted. The ultimate primary and secondary recovery will be 302 bbl/acre-ft and approximutely 40 percent of the OSTOIP. The actual performance is compared with the predicted performance by both the Stiles and the Dykstra-Parsons methods, and applicabiliry of these methods to this particular reservoir is evaluated. The performance of this project indicafes highly stratified reservoirs can be successfully and economically waterflooded when either reservoir or economic conditions preclude the use of mechanical and chemical means of mdbility control. Introduction The concept of the stratified reservoir has been used by reservoir engineers for many years to describe the vertical variations in permeability within a reservoir. Numerous techniques have been advanced to predict the expected waterflood performance of the stratified reservoir, and in most cases they prove reasonably accurate. The advisability of undertaking a prospective waterflooding project is determined, based on these predictions. This paper presents a review of a waterflood project in a highly stratified reservoir that normally would be considered a marginal prospect, at best, when evaluated with any prediction technique properly adjusted for reservoir conditions. This kind of project can be successful if the predictions are used to design a waterflooding system capable of economically recovering an oil cut of 1 to 2 percent. Experience gained in the early stages of the project's development was profitably applied in the later development of the entire reservoir and could prove beneficial to other projects with similar reservoir stratification or fracture characteristics. The East Burbank pool waterflooding operations have been developed in three separate stages, each of which has been a separate project: Mid-Burbank Unit, Flood A, and Stanley Waterflood. When referred to collectively, these projects will be called the Composite Project. The Skelly Oil Co.'s Barber lease — the only portion of the pool not included in the three projects — is operated as a separate facility with a cooperative injection-well agreement. It contains less than 80 productive acres and would not significantly affect the over-all performance picture.

Jan 1, 1969

By N. S. Dalal, B. Jafari, V. Vallyathan

Electron spin resonance measurements have now been completed on the decay kinetics of the organic free radicals formed on crushing or grinding of a well characterized anthracite coal. The free radicals exhibit a complex decay pattern for the first few hours after the grinding, and a smooth decay thereafter. Parallel hemolysis studies indicate. a half-life of the decrease in the cytotoxicity of the fresh· dust to be about half-a-day. The cytotoxicity of the freshly-made dust decreases on addition of superoxide dismutase, catalase and sodium benzoate. The hemolysis rate is lower for the dust stored in buffers as compared to air. A chemical model will be presented to accomodate the cytotoxicity and spectroscopic data, and ~heir implicati6ns to pneumoconiosis.

Jan 1, 1988

By Edward D. Graf

Once the heavy work of mining, supporting and completing an underground structure is finished, there is frequently the problem of handling unwanted water infiltration into the opening. Methods of controlling the infiltration vary from collecting and channelling the inflow to shutting off the water at the surface of the opening or within the ground formation. Discussed are various methods of controlling ground water inflow from within the structure including collector pipe systems, shotcrete, cement grout, bentonite, and various chemical grouts. Case histories illustrating some of the methods and materials will be presented.

Jan 1, 1987

By Whiten W. J

A simulation model was used to study the performance of various types of screen cloth on industrial vibrating screens. The model takes into account the effect of loading upon screen performance and predicts both themass flow rate and size distribution of the screen products.It was found that the use of the simulation model allowed the reconstruction of data for identical conditions and hence has simplified the analysis of the comparative performance of the screens. The dependence of performance upon operating conditions was found to vary markedly with screen cloth type.

Jan 1, 1977

FEBRUARY GENERAL MEETING The January General Meeting of the Institute was held in Kelvin House, Johannesburg on 21st January, 1970, at 4.30 p.m. Mr V. C. Robinson (Vice-President) was in the Chair. There were also present eighteen Members, Messrs M. Barcza, A. R. C. Fowler, R. C. J. Goode, Prof J. de V. Lambrechts, Messrs T. C. A. Meyer, J. A. Nixon, V. C. Robinson and P. W. J. van Rensburg (Council Members), C. A. Border, D. F. H. Grave, S. D. Hill, A. F. Lee, W. L. le Roux, C. S. Macphail, D. L Starkey, S. G. Taussig, W. T. L Wayman and Dr A. Whillier. Three Associate Members, Dr M. I. Brittan, Messrs R. Hemp and M. J. Martinson. One Student, Mr R. P. W. Henrard. Two Visitors, Dr N. G. W. Cook and Mr J. B. Smith. Secretary, Mr D. C. Visser. Total present: Twenty-six. 1. OBITUARY The Vice-President: "It is my sad duty to announce the death of the following members of the Institute: Reginald Gordon McConnell, Member, who joined the Institute on 24th April, 1946 and passed away on 26th September, 1969. James Henry Moore, Member, who joined the Institute on 28th February, 1951 and passed away on 2nd January, 1970. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask those present to stand and observe a few moments silence." 2. MINUTES The Vice-President: "May we confirm the Minutes of the General Meetings held on 15th October and 19th November, 1969, as published in the December, 1969 issue of the Journal?" 3. MEMBERSHIP The Vice-President: "I have pleasure in announcing that the names of the under-mentioned candidates, having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following grades: Member: Woodford Anson Gilbert. Associate Members: Michael John Harvey Tonking, Schalk Willem Vorster, Edward Alfred Cole, Johannes Godlieb Bosch. Graduate: Leonard Raymond Kilpatrick. Affiliates: Clive Frere Knight Pouiton, David Philip Ayliff, Kenneth Gillings, Edward Gilbert East. Students: Stirling Graham Low, Petrus Stephanus van der Merwe, Louis Johannes Fourie, Clive Maxwell Winterstein. MEMBERS TRANSFERRED TO A HIGHER GRADE From Associate Member to Member: Albert Arthur Hazell, Neville Martin Hayne. "I welcome the newly elected members to the Institute and congratulate the members who had been transferred to a higher grade. 4. GENERAL BUSINESS The Vice-President: "I wish to announce that except for the student prizes awarded at the November meeting, Council has decided to make no awards for 1969. Are there any further matters to raise under the heading of General? If not, we will proceed to the next item on the agenda which is the presentation of tonight's paper. 5. PAPER FOR PRESENTATION The Vice-President: "Professor Starfield may I call on you to deliver the paper entitled "A rapid method of calculating temperature increases along mine airways". After the presentation of the paper, the Vice-President said: The Vice-President: "Thank you very much, Professor Starfield. Gentlemen, I think that many of you here, who have to do with the design of mines in an age where costs and difficulties generally, are increasing at a rate which we find almost impossible to keep up with, I would agree with you that we are fortunate to have a band of people like Professor Starfield, and others who are dedicated to producing the tools, and methods which we need to sort out these problems. I am sure that you would agree with me, that the old rule-of-thumb methods are finished forever, that we can never go back to the methods which served us in the past, when we were close to the surface and had not met the conditions which we are meeting now, and which we are going to meet in an increasing degree in the future. It is to people like Professor Starfield, with these clear, completely logically described new methods, that we look for the solution of our problems in the future. I think the whole problem of layout of any mine, is one where you can reliably prognosticate what you are likely to find in a variety of circumstances to meet the wide range of things which must happen when you consider the costs in these modern operations. Thank you very much, Professor Starfield, for coming and giving us this paper. Thank you for making plain to me how these mathematical models of yours are used. I am sure that what you have said will be a very valuable addition to the archives of this Institution. Thank you very much, indeed, and Gentlemen, will you please show your appreciation in the normal way." (Applause). Professor J. de V. Lambrechts, Mr R. Hemp and Dr A. Whillier then contributed to the discussion. (These contributions will appear in a later issue of the Journal.) PAPERS OPEN FOR DISCUSSION The Vice-President: "Listed on the agenda are papers open for discussion. I would suggest that anyone wishing to contribute to these papers submit their contributions to the Secretary in writing." CONCLUSION The Vice-President: "I wish to thank members and visitors for their attendance, and now declare the meeting closed." The meeting closed at 5.30 p.m

By L. W. Swent

Dr. Emrick, honored guests, distinguished speakers, ladies and gentlemen, I am Langan Swent, Vice President for Environmental Affairs and Occupational Safety and Health, of Homestake Mining Company. Today, I appear on behalf of the American Mining Congress, as chairman of its uranium mine health subcommittee. The American Mining Congress is a trade association of several hundred members, which include the producers of a large proportion of the nation's uranium. I've been asked to make a statement of principles for the uranium industry. There are two types of principles that apply to industry in general, and specifically to the uranium industry. Some have external origins and apply regardless of what industry does or thinks. Others are generated by industry itself and serve as goals for the industry. I'll discuss some of each type. I'll limit my statement to those principles related to the subject of this conference--radiation hazards in mining. I won't take your time trying to explain some of the unrelated principles that we must all contend with, such as Parkinson's Laws, Murphy's Law, and the Peter Principle. First and foremost, industry has a sincere interest in the well-being and health of its employees. There are two basic reasons for this. One is a basic respect for human lives, especially those of people we see and work with every day. No one in management wants to carry the lifelong burden of blame for a life lost due to poor working conditions. Most uranium and other mining is done in small communities. Production workers, maintenance workers, service workers, shift bosses, foremen, superintendents and managers all live in the same community. They attend the same churches. They serve together in civic activities. Their children go to the same schools. If one employee in such a community loses his life due to poor working conditions, those remaining know in a daily and intimate way the resulting personal tragedy, usually of a bereaved widow and fatherless children. This sad experience makes the community, including industry management, intensely sensitive to the need for maintaining good working conditions in the mines. But what about the segment of industry that does not live in the mining communities? Corporate and owner's offices are frequently hundreds of miles from the communities where the mining takes place. Many of these people are not personally acquainted with the workers, and there are few close personal ties between the two communities. The distant staff are, however, still human beings and motivated by the same basic human respect for life. Mr. Manuel Gomez of MSHA and a member of the planning committee for this conference summed this point up expressively when he told me: "No one group has a corner on compassion." In addition to compassion, there is another factor. In both communities the basic assignment to everyone is to produce profits. In carrying out this assignment, supervisory and management people are acutely aware of the high cost of illnesses and accidents. Their objective of maximizing profits is advanced significantly by minimizing illnesses and accidents at the mines. A business that has illnesses and accidents generally suffers from poor employee morale and high employee turnover, both of which detract from profits. Next, I would like to talk about what industry has done in the field that is the subject of this conference. We have worked at all sorts of methods to reduce exposure of employees since the exposure standards were first introduced and then lowered. Other speakers will go into details of technology, and I'll simply comment on exposure results. These are best shown in Table 1. The table shows the average WL to which miners in U.S. underground uranium mines have been exposed since 1937 through 1980. The trend of decreasing radon daughter concentrations throughout the period is obvious. Figure 1 presents this data graphically and shows the trend at a glance. This record begins in 1937 when uranium, as such, really wasn't being mined or sought. The concentrations given by the U.S. Public Health Service were for a few small vanadium mines which carried uranium as a by-product. A few years later, when the Manhattan project to develop the atomic bomb was begun, these mines became the first U.S. uranium mines and the vanadium became the by-product! The radiation hazard then also received attention and the average concentrations began to decline. As knowledge of the reality of the hazard spread, conditions improved. The search for uranium in the U.S. turned up new and larger ore bodies that had to be mined by large underground mines. These mines involved ventilation planning from the beginning, and when they came into production in the late 1950's they lowered the average concentrations greatly. Then in 1960 the American Standards Association adopted a standard setting 1 working level as a satisfactory condition, and several action levels up to 10WL, at which point removal of people from exposure was called for. As a result of the uranium producing states governors' conference in December 1960, state mine inspection agencies, in the early 1960's, began to adopt and enforce the ASA standards. As a result, average concentrations again declined. In 1967, the Federal Radiation Council recommended an annual limitation of 12 WLM per individual. This represented a great change in the methods of

Jan 1, 1981

By Wm. J. McCracken

HISTORICAL REVIEW OF BOARD OPERATIONS The Ontario Worker's Compensation Board was established in law enacted by the legislature of the Province of Ontario in 1915. It was designed to pay insurance benefits to injured workers, and at the same time to protect employers from legal suit. It was based upon an enquiry system rather than an adversary system such as that used in the courts process. Initially, the system was designed to pay compensation benefits and subsequently, to pay for the cost of medical treatment and pensions for disability and disease resultant from the effects of traumatic injury. In 1947, the Act was changed to include industrial or occupational generated diseases, not specifically related to traumatology. Such occupational diseases were therefore accepted and benefits paid subsequent to that date. As will be discussed in several minutes, even today the vast preponderance of compensation claims with the Ontario Board continues to be related to the effects of trauma. HISTORICAL REVIEW OF EXPOSURE TO RADON GAS DECAY PRODUCTS In some areas of Ontario, especially in Northern Ontario, there is a natural leaching of radon gas from the underlying rock formation. This constitutes very low levels of radon gas decay product radiation exposure to those persons coming in contact and inhaling these substances. This paper however is designed to discuss the occupational generated types of radon gas exposures. For many years dating back to the 1930's, partially refined ores were being shipped from Northern Canada to a refinery located at Port Hope, Ontario, still in operation and currently operated by Eldorado Nuclear Limited of Canada. Initially, the purpose for the operation was extraction of radium to be sold on world markets for medical treatment purposes. With the advent of World War II, this market collapsed. Subsequent to World War II, the availability of other sources of radiation for medical radio-therapy generally replaced the requirements for radium. During World War II, a new market opened up for the Port Hope refinery however as work into nuclear chain reactions and the development of the atomic bomb identified the need for uranium and enriched uranium. During the period of operations where radium was being extracted at the Port Hope refinery, it is now known that an identifiable radon gas hazard did exist. This hazard disappeared when the production line for extraction of radium ceased operations. In 1954, uranium mining operations opened up in Ontario at two locations, Bancroft and Elliot Lake. At the peak of operations, 16 mines were operational and 11,000 workers were employed in these mining operations. A high level of mining activity continued over a 10 year interval with the Bancroft Mines closing permanently in 1964 following a 10 year life of operation. The other mines in Elliot Lake closed about the same time with the exception of two uranium mine operations which have continued to be operational up to the present time. By 1965, due to a dramatic drop in world demand for uranium, the total work force had fallen to 1/10 of the peak work force, and approximately 1,300 workers remained in employment. It is of interest to note that one significant difference in the work environment between Elliot Lake and Bancroft was the high silica content of the Elliot Lake ore. This gave rise to a number of cases of silicosis developing in relatively short intervals of time in the Elliot Lake miner population. No cases of silicosis were identified from the Bancroft operations. Based upon the experience in investigating and evaluating actual cases of lung cancer in the uranium miners over the years, the medical staff at the Ontario Board also developed the impression that radiation levels were much higher in the Bancroft operations, especially in the earlier years of operation, than at Elliot Lake. This resulted in accumulation of higher levels of Working Level Months (WLM), usually over a shorter exposure interval in many of the cases. This aspect will be further evaluated in this presentation. Subsequent to 1965, the work force remained quite static in numbers until 1975. At that time, there began to develop an increase in the work force, and this increase is continuing at a moderate rate up to the present. INITIAL METHOD OF HANDLING LUNG CANCER CLAIMS The first lung cancer claims in Ontario from uranium mining operations were accepted on the perceived cause-effect relationship. This relationship was based upon the data from the Colorado observations and the Czechoslovakia data. Initially, a series of regression equations on mortality were developed and used to estimate the effect of exposure to low cumulative doses of radon daughters as it might relate to the frequency of occurrence of lung cancer at any particular cumulative exposure level. A probability of cancer being radiation induced as against it being caused from other factors was calculated. This method was discontinued subsequent to 1972 due to problems encountered in carrying out this complex evaluation. Thereafter, each case was dealt with on an individual basis, being based upon whether or not the tumour was of the oat cell type, a cumulative exposure in excess of 120 WLM; latency periods in excess of 10 years, commencement of mining prior to

Jan 1, 1981

By Harold A. Krueger

FACILITIES and mining operations of the National Lead Co., St. Louis Smelting and Refining Division, near Fredericktown, Mo., are situated in a famous mining area. Copper, lead, nickel, and cobalt have been mined here for more than 100 years, work having been started on a high sulphide copper outcrop in 1847. Lamotte sandstone is characterized by differential compaction on a rigorously eroded pre-Cambrian surface. The Bonneterre formation was therefore a good host for minerals not generally found in mineable quantities in these midwestern areas. Unusually complex minerals, however, make beneficiation difficult, and because of irregular ore thicknesses and elevations many engineers and operators have not attempted to mine the property. Others have tried who failed. This paper deals with economic, efficient, and competitive methods of mining these highly irregular orebodies, as compared to the open-stope, room-and-pillar methods normally used for horizontal-bedded lead deposits. For the purpose of this study it should be understood that the ore is found in two distinctly different types of occurrences, one to be designated as basin ore and the other as contact ore. Mining of basin ore is complicated by many faults, fractures, cross faults, and breaks. Contact ore is complex because it is found on flanks or slopes of pre-Cambrian knobs or highs. The dip of the mining floor for the latter type varies between 18" and 45". Occurrences of both types of ore are complicated by water courses or solution channels which carry unconsolidated shale, lime, sand, and dolomite. This material is also found between the bedding planes of the members of the Bonneterre formation. The water found where there are fractures, faults, and channels makes it very fluid and tacky, see Fig. 1, particularly after it has been blasted and handled by loading and hauling machines. Much of the ore can be wadded and thrown without dispersing. During early operations by the Buckeye Copper Co. in 1861 and the North American Lead Co. from 1900 to 1910, conventional narrow-gage railroad and side dump mine cars were used with hand shoveling. The complications of mining the contact ore, the only type attempted at this time, can be appreciated when it is realized that operators were obliged to use mules for haulage. Haulageways constructed on these slopes were of necessity similar to wagon trails or goat trails up the side of a mountain. In other words, it was merely a matter of going from side to side of the strike length of the slope, gaining a little in elevation on each shuttle trip. Production totaled only one to two tons per manshift. A few years later, about 1913, the property was purchased by combined Canadian interests known as the Missouri Cobalt Co., and the use of trolley locomotives was initiated. Between 1900 and 1928 a land agent using churn and diamond drilling methods prospected scattered sections of the area. In 1928 the first property was purchased by the present company, then operating as the St. Louis Smelting and Refining Co. Check drilling and prospecting was carried out by the company at various times between 1928 and 1939 to correlate the erratic mineralization. Much information about both types of orebodies was accumulated, but it was still questionable as to whether money should be invested to work these occurrences. In anticipation of high lead and copper prices, about the time World War II started, it was decided to develop and bring into production some of this ore. In 1942 No. 1 shaft was put down on the largest basin-type orebody and in 1943 No. 2 shaft was put down on contact-type ore. Operations were expanded when No. 3 shaft was completed in 1943, and progressed further in 1948, when National Lead Co. dewatered and opened No. 5 and 6 mines, old workings of the North American Lead Co. and the Missouri Cobalt Co. Because of the differential compaction of Lamotte sandstone over the pre-Cambrian porphyry, in some instances mineable thicknesses of basin-type ore occurred 20 to 30 ft above the sand. This is the exception rather than the rule, since most of the mineralization starts at the sand and is variable in thickness. The ore was attacked, therefore, by development drifts and crosscuts at the lowest possible elevation, where the ore immediately overlying the Lamotte sandstone could be drained and made accessible for mining. It was planned to connect to the drifts and crosscuts with raises to mine ore deposited 20 to 30 ft higher. The higher orebodies were thus mined as slusher levels. Slusher hoists were used to drag the ore into the raises, which were made into hoppers. The ore was then loaded into 32x32-in. ore cans, hauled to the shaft by battery locomotives, and hoisted by the conventional Tri-State method. The rate of efficiency was 5 to 6 tons per manshift underground. The contact-type ore was attacked in a similar way, except that the orebodies were not nearly so wide, so that they were more flexible for slusher loading into cans. This advantage was offset, however, by haulage complexities, since the railroad was constructed on steep slopes. Through experience and ingenuity, many improvements were made in mining both types of ores. The two levels, so-called, in the basin-type ore-bodies were connected as previously planned, more efficient locomotives replaced the older ones, and a

Jan 1, 1954

By C. W. Binckley, F. R. Burgess, E. R. Haymaker

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By R. P. Laforce, ZJ. R. Low, A. M. Turkalo, D. F. Stein

The interaction of the crlloying eletnenls, nickel and chromium, with the impurity elements, antimony, pIzosphorus, tin, and arsenic, to producse reversible temper brittleness in a series of high-purity steels containing 0.40 wt pct C has been investigated. The alloyed steels contained approximately 3.5 pcl Ni, 1.7 pct Cr, and 0.05 to 0.08 pct of the particular irnpurity to be investigated. Susceptibility to teirlper embrittlement was measured by comparing the notched-bar transition temperature of each steel after quenching from the final temper and after very slow cooling (step cooling;) following the final temper. A plain carbon steel without alloying elements, bu/ ud/h 0.08 pel Sh, does not embrittle when step-cooled through the emzbrittling range of temperatures. The same embrittling treatment, applied to a steel with about the same antinzony content but with nickel and chvonziunz added, causes a 700°C increase in transition temperature. If chromium or nickel is the only alloying element, the increase in transition temperature is only 50%, again with antimony present. A carbon-free iron containing nickel, chromium, and antimony shou~s a 200°C shift in transition temperature for the same thermal treatment. Specific alloy-impurily interactions are also observed for the other impurity elements, phosphorus, tin, and arsenic. Additional investigations involving electron microscopy, trzicrohard-ness tests of vain boundaries, minor additions of zirconiutn and the rare earth and noble metals, nzainly with negative results, are also described. HE particular type of embrittlement investigated is that which is encountered in alloy steels tempered in the temperature range from about 350" to 525'C or slowly cooled through this range of temperatures when tempered above this range. This type of embrittlement is sometimes called reversible temper brittleness to distinguish it from the embrittlement indicated by a minimum in the room-temperature V -notch Charpy energy vs tempering-temperature curve encountered in the range 28 0" to 350°C. Temper brittle-ness seriously restricts the use of many alloy steels since it precludes tempering or use in the embrittling range of temperatures and may significantly raise the ductile-brittle transition temperature of heavy-section forgings and castings tempered above the embrittling range, since such sections cannot be sufficiently rapidly cooled after tempering to avoid embrittlement. The very voluminous literature of temper brittle-ness up to about 1960 has been reviewed by woodfine' and LOW.' Of particular significance to the present investigation was the demonstration by Balajiva, Cook, and worn3 that high-purity Ni-Cr steel does not exhibit temper brittleness and the subsequent detailed and systematic study by Steven and Balajiva~ of the effect of impurity additions on the susceptibility to embrittlement of Ni-Cr steels. Steven and Balajiva showed that, of the impurities which may be found in commercial steels, Sb, As, P, Sn, Mn, and Si could all produce temper brittleness in a high-purity Ni-Cr steel. The principal purpose of the present investigation was to study the effects of particular alloy-impurity combinations on susceptibility to temper embrittlement. The steels used were high-purity 0.30 to 0.40 wt pct C steels containing 3.5 wt pct Ni and 1.7 wt pct Cr, separately or in combination. The susceptibility of these steels was then determined when approximately 500 ppm by weight of antimony, arsenic, phosphorus, or tin were added as an impurity. The melting, casting, and forging practices used in the preparation of the materials investigated are described in Appendix A. Table A-I in this appendix shows the analysis of all steels to be discussed. The steels were produced as 20- or 2-lb heats. The smaller heats were used after it had been demonstrated (see Appendix B) that a small, round, notched test specimen could be used to measure the shift in the ductile-brittle transition temperature caused by temper brittleness with about the same result as that obtained by Charpy testing. HEAT TREATMENT Unless otherwise noted, all steels were tested for embrittlement in the tempered martensitic condition. A typical heat treatment for a 0.40 C, 3.5 Ni, 1.7 Cr steel was: 1 hr at 870"C, in argon, quench into oil at 100"C, quench into liquid nitrogen, temper 1 hr at 625"C, and water-quench. The warm oil quench was used where quench-cracking was encountered; otherwise the initial quench was into room-temperature oil or water. For other compositions austenitizing temperatures were 50°C above Acs with the remainder of the thermal cycle the same. Steels in this condition, with no further heat treatment, are designated as non-embrittled. The above quenching and tempering cycle for the 0.40 pct C steels resulted in as-quenched hardnesses of 48 to 53 RC and as-tempered hardnesses of 24 to 31 Rc except in the case of the plain nickel or plain carbon steels. In these, the as-tempered hardness was as low as 80 to 90 Rg. No attempt was made to adjust the tempering temperature to obtain the same hardness in ali steels since it was felt that a uniform thermal cycle was more important than exactly equivalent hardness values. Pro- the standard quench and temper described above, the standard embrittling treatment was "step-cooling". For this the thermal cycle was: 593"C, 1 hr; furnace-cool to 538"C, hold 15 hr; cool to 524"C, hold 24 hr; cool to 496"C, hold 48 hr; cool to 468'C, hold 72

Jan 1, 1969

By E. R. Haymaker, C. W. Binckley, F. R. Burgess

A method of establishing stabilized back-pressure curves for gas wells producing from formations of extremely low permeability is presented. Actual well performance under many different operating conditions is shown by the stabilized back-pressure curve. By use of the method. it is possible to conduct back-pressure tests with a critical-flow prover on wells that stabilize slowly, and save approximately 88% of the gas ordinarily vented to obtain satisfactory test data, with a great reduction in time required for testing. INTRODUCTION The reasons for establishing dependable back-pressure curves on gas wells have been pointed out by previous publications. The publication most referred to. of course, is the United States Bureau of Mines Monograph 7, titled "Back-Pressure Data on Natural Gas Wells and Their Application to Production Practices". The technique generally established therein has been accepted and used by many engineers; and, when proper tests are conducted, the results can be used for the analysis and solution of several practical problems concerning field operation and development. Even where formations of low specific permeability are encountered, the determination of a well's actual performance by the back-pressure test method permits the engineer to analyze many problems in individual well operation and also to predict necessary future field development. Such problems as the determination of the ability of a well to produce into a pipe line at a predetermined line pressure, the design of gas gathering systems and meter settings, and the determination of the time and the number of wells required to be drilled to meet future market obligations, can be solved, in part., by the use of a reliable back-~ressure curve. In addition, the computed well delivery rates determined by data from backpressure tests ordered by state regtilatory bodies, when compared with the true back-Pressure curve, permit the operator to ascertain whether such data represent unstable or relatively stabilized delivery rates for given pressure conditions of the well. The technique of back-pressure testing, as described in this report, was developed by Phillips Petroleum Company engineers from data obtained during a testing program that started in 1944 and has been continued to date. Three hundred and eleven back-pressure tests were conducted on 299 wells located in the southern part of the Hugoton Field. The gas-bearing zone is composed of several dolomitic formations of the Permian Age; the important ones are the Herington, Upper Krider, Lower Krider, and Winfield. The average bottom-hole temperature is approximately 91 °F.. and the initial wellhead shut-in pressures range from 400 to 440 psig. The spacing pattern is 640 acres per well with each well located near the center of the section. The range of back-pressure potentials on wells tested was from 500 to 23,000 Mcfd. All gas wells were acidized, and the quantity of acid used, expressed in 1574 hydrocloric acid, varied from 12,000 to 22,000 gallons per well. The quantity and concentration of each treatment depended on the stage, the formation being treated, and experience gained from previously completed wells. The gas in the Hugoton Feld is a "dry" gas. It has a gasoline content of approximately 0.25 gallons per thousand cubic feet, as determined by charcoal test, and its specific gravity averages about 0.71 as compared to air (air = 1.00 at 60°F.). Of the wells tested, 71 were completed with 7" casing, 3 with 9 5/8" casing, and 1 with 6%" casing set on top of the upper producing formation with the well bore through the gas bearing formations being open hole. Two hundred and twenty-four were completed with 5 1/2'' O.D. casing set through the gas bearing formations and perforated. For the purpose of establishing reliable back-pressure curves in the area, Phillips Petroleum Company personnel has computed data on the basis of 24-hour flows per point. Early in the program, many tests were actually permitted to flow 24 hours to obtain data for each plotting point, at great expense in man power and time. Presently, however, such tests have been replaced by tests of short duration flows which can be made to effect results that correspond to the tests obtained by flows of much longer duration. METHOD When a gas well producing from a reservoir of low permeability is opened for production through a constant size orifice, both the rate of flow and working pressure decline. first at a high rate and later at a lower rate until after several hours the decline becomes difficult to ascertain. In this paper the rae of flow and working pressure are considered to be stabilized when it becomes difficult to observe changes in working pressure during a period of three hours by the use of a deadweight pressure gage. Stalibization of pressure in the literal sense is never obtained in a producing gas well. In formations of low permeability. such as those in the Hugo-ton Field, most wellhead working pressures approach stabilization closely enough to be used satisfactorily in the determination of a back-Pressure potential curve after flow periods of 24 hours. We shall therefore describe the backpressure curve calculated from ohserved rates of flow and working pressure at the end of 24-hour flow periods.

Jan 1, 1949

By J. F. Neill, O&apos

The manganiferous schists occurring in the vicinity of Kings Mountain, North and South Carolina, suggest significant tonnages of potential submarginal ores. Although some reconnaissance work in connection with these deposits has been reported, no recent information has been published. Evaluation of the schists as a possible domestic manganese resource has not always adequately considered the fact that the manganese content occurs quantitatively both as oxide and as the silicate, spessartite. The Bureau of Mines investigation herein reported includes preliminary studies to indicate the extent of manganese oxide mineralization and to deter-mine the amenability of the material to sulfur dioxide leaching. The field reconnaissance studies suggest a resource containing in one area an average of 6.4 percent manganese as oxide. The procurement of depth information was beyond the scope of the investigation.

Jan 1, 1962

By M. G. Zabetakis

This publication describes an investigation conducted by the Federal Bureau of Mines regarding the cause of an explosion of a dephlegmator or fractionating column at the Cities Service Oil Company Refinery, Ponca City, Okla., January 22, 1959. The column was that used with the refinery's No.1 Dubbs Coker. The explosion caused the death of an employee of the refinery and resulted in extensive damage to the refinery and to nearby property. The Bureau's study of the explosion began January 26.

Jan 1, 1960

By Frank Pepe, Nestor Garavelli

The 2023 Rapid Excavation and Tunneling Conference (RETC) will be held in Boston, MA and will include the presentation of 133 papers divided into 20 technical sessions during the 3 day conference that were selected from over 200+ papers that were submitted to the committee. The selected papers are included within this book to provide a comprehensive recap of the conference while also providing a source of reference for contractors and engineers in the future. The selected papers will include contributions from all divisions of the tunneling industry plus risk management and best contract practices. Boston is known to the tunneling industry for its complex and difficult tunneling history, specifically of recent memory the Central Artery/Tunnel Project also know as the “Big Dig” of the 1980s and early 1990s. The selection of Boston as a host city was fitting from a historical perspective and as avenue for the city to present its upcoming tunnel projects. RETC began in 1972 with the idea of sharing ideas, design and project construction experience, and new technology, between contractors, designers, owners and suppliers. The ability to provide a single location every other year for all facets of the tunneling industry to gather and discuss the aforementioned was and still is viewed as a way to help the tunnel industry grow. The lessons learned from completed projects, the advancement of technology which could be implemented into design and the presentation of new projects by owners/designers and contractors allows for the limits and complexity of upcoming projects to be expanded beyond our current capabilities. Our industry has never been as busy as it currently is, and we are seeing more future projects coming out for solicitation across all business sectors. With the good fortune that all of us have been blessed with one of the biggest challenges that we have been faced with is the shortage of future management on all levels for our projects including the labor force. We all want our industry to continue to grow and succeed, our most important assets are the people that we employ. Investing in the education and continued training of our work forces to be up to date with the latest technology and methods is the key to our success. This also includes develop, recruiting and mentoring of young students graduating college to join our industry so that we can all continue to grow. We hope that all those attending the conference will have the ability to attend as many sessions as possible and to expand their network within our industry. As in past years, scholarship students will be in attendance and we encourage all to offer these students an opportunity to visit jobs, attend learning sessions or future internships to expand their interest in our industry that needs an injection of young engineers to contribute and lead our future Rapid Excavation and Tunneling Conferences. The program chairs wish to thank the session chairs, co-chairs, authors, and other members of the RETC Executive Committee for their dedication to this conference. Last but certainly not least, we give special thanks to the SME staff for their hard work and enthusiastic support in making this conference possible.

Dec 1, 2023

By Brandon Buschmeier, Frederic Masse

"Inclusions are a type of ground improvement that provide an improvement of a soil mass by insertion of a material with better characteristics than the surrounding soils. There are primarily two types of inclusions: “Soft” inclusions which are constructed of granular material (Stone Columns, Rammed Aggregate Piers, VibroPiers...), and “rigid” inclusions which are constructed of grout inserted with or without pressure (VibroConcrete Columns, Controlled Modulus Columns, Soil Mixing Columns).While the central principle of the inclusions is similar (i.e., overall improvement of characteristics of the soil mass below the structure), the load transfer mechanism is radically different for each technique. Therefore, the applicable design methodology is specific to the type of inclusions and there exists no universal method of design which spans across all inclusions.This paper will present an in-depth comparison between the standard design methods used for “soft” granular-type inclusions (Priebe modified, Balaam & Booker, Goughnour & Bayuk...) and the methods used for “rigid” inclusions which mainly rely on finite element analysis. The paper will explain why the design for soft inclusion methods cannot be applied to rigid inclusions and vice-versa. Each design method will be reviewed in detail to better emphasize its limitations and advantages.Two case histories will also be presented; one for each type of inclusions in order to illustrate the concepts developed in the first part of the paper.1 INTRODUCTION1.1 GENERAL OVERVIEW OF GROUND IMPROVEMENT WITH INCLUSIONSThe use of ground improvement methods to provide the appropriate amount of foundation support is a growing and constantly evolving industry. Traditional structural foundation methods including ‘shallow’ and ‘deep’ foundations do not adequately address the wide range of settlement tolerances, soil conditions, and loading considerations inherent to each unique potential project. In some instances, ‘shallow’ foundation solutions are simply not feasible due to soil and loading constraints. Furthermore, ‘deep’ foundation solutions are used to ‘bridge’ the soft compressible soils, ensuring that the entirety of the load in the structure is transmitted through individual elements into competent layers below the ground surface (bedrock, dense residual soils). Highly concentrated structural loads are transferred into the individual elements by means of direct contact requiring the use of structurally rigid surficial components (structural slabs, grade beams, and pile caps).Ground improvement bridges the gap between these two traditional methods, offering adequate foundation support while using more costeffective techniques and design methodologies. Inclusions are a type of ground improvement used to provide a reinforcement of the soil mass through the vertical insertion of a material with better characteristics than the surrounding soils. Much like deep foundations, inclusions are installed through soil layers with high compressibility and/or low bearing capacity and terminated in a suitable bearing stratum. However, unlike deep foundations, ground improvement inclusions rely on a distribution of load between the soil and the inclusions. By doing so, some of the structural load is applied directly to the soil in a proportion equal to its bearing capacity and compressibility limits, while the rest of the load is shed into the vertical inclusions down to the bearing stratum. Load sharing is a critical aspect in the performance and design of the various ground improvement methods."

Jan 1, 2015