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By Jan Zwarcendyk

This study is primarily directed toward providing an understanding of the economic complexities associated with subsidence damage on the surface resulting from underground mining. Some of the pertinent theories on the physical stresses involved are reviewed, and both remedial measures and relevant laws in various countries are discussed. Part I (Chapters 1-3) is an historical overview of various aspects of subsidence problems (theoretical, remedial, and legal) during pre-World War I, between World Wars, and post-World War II, respectively. Part II (Chapters 4-9) presents a comprehensive analysis of the economic aspects of subsidence in relation to the following mining alternatives: (a) carrying out the lowest cost mining method without regard for any surface subsidence, (b) special mining techniques, (c) partial mining, (d) full recovery with stowing, and (e) sterilization or leaving the mineral unmined beneath selected areas. These alternatives are evaluated in terms of their measurable expenses.

Jan 1, 1971

By G. H. Keith

Electrowon tungsten powders were investigated with respect to consolidation, fabrication, and mechanical properties. Sheet, 0.03 inch thick, was produced and its tensile strength measured between 250° and 1,935° C. The large particle size of electrowon tungsten effectively precluded sintering to a density sufficient to allow hot working to sheet or bar. The powders were consolidated by die pressing to 70-percent density, sheathing in molybdenum, and high-energy-rate extruding to either round or sheet bar of 100-percent density. The material was then rolled conventionally to sheet. The mechanical properties of the sheet prepared from the electrowon powders compared favorably with those reported in the literature for sheet prepared from commercially produced hydrogen-reduced powder.

Jan 1, 1970

By S. F. Radtke

The properties and characteristics of lead and zinc have made these metals useful to man in many ways since the days of antiquity. Despite their long history of use, however, these metals have proved to be extremely resilient and responsive to modern needs. New alloys and compounds continue to be developed, adding to the growth of these metals. Consumption data is given for 1969 and compared with one and two decades ago. Trends in major markets also are cited and explained. Uses for lead and zinc which have come into prominence within the past few years are described and explained, with emphasis on the role played by the industry's cooperative research program. Current efforts in the research phase are discussed, with details given on major efforts for both metals, including new alloys, process developments, applications research, finishes, coating, paints and pigments, batteries and fundamental research. A forecast is given of promising new areas and a projection made on a longer term of new applications that may emerge from current research.

Jan 1, 1970

The Bureau of Mines analyzed the cycle of secondary gold to determine the quantity of gold not being recovered from scrap, and to identify areas for research to increase the supply of gold from scrap. Secondary gold in 1967 was estimated to be 2.4 million troy ounces; this excludes secondary gold which is recycled within consuming plants. Firms contacted included consumers using about 41 percent of the gold in 1967, And refiners that recovered about 90 percent of the secondary gold. Results of the study indicate that loss of gold is small, and refiners and consumers are accelerating programs designed to reduce recovery costs. With the increasing generation of low-grade industrial scrap, research is needed to improve present recovery techniques and to develop methods to accelerate the flow of secondary gold back to supply.

Jan 1, 1970

By Cuppam Dasarathy

The incidence of liquid inzmiscibility in binar)) indium alloys has been theoretically analyzed on the basis of the Hildebrand-Alott equation. Bedictions of miscibility or otherwise Imve in general been found to agree with those phase diagrams that are already publislzed in the literature. Out of a total of 27 systems, where either the complete phase diagrams are published or liquid immiscible behavior is reported, the Predictions agree with the experimental data in 25 systems, the exceptions being the Te-In and Ni-In systems. According to the equation, liquid immiscibility is also indicated in the binary alloys of indium with K, Rb, Cs, Na, Sr, Ba, Ti, Zr, V. Nb(Cb), Ta, W, U, Re, Ru, Rh, Os, and Ir. RECENT investigations by the author have shown that indium when alloyed with iron, chromium, and cobalt shows liquid immiscible behavior.1"3 The Fe-In phase diagram shows a wide range of compositions where the liquids are immiscible.4,5 No intermediate phases are present in this system. No precise information is available about the extent of liquid immiscibility in the Co-In system. However, it is certain that there is a range of compositions where the liquids are immiscible and that there are two or three intermediate phases,376 in the system. Liquid immiscibility is also strongly indicated in the Cr-In system and no evidence was obtained in the brief investigation to indicate the presence of intermediate Cr-In phases.2 The present paper deals with a theoretical analysis of binary alloys of indium with certain elements of the periodic table and indicates the systems where liquid immiscibility may be expected. The incidence of liquid immiscibility in binary systems has been theoretically examined by many workers and many excellent papers are available on the subject. In this paper, the alloy systems are examined on the basis of the more recent ideas proposed by Mott.7,8 It has been claimed8 that the Mott parameter predicts the incidence of miscibility or otherwise with reasonable accuracy and consistency. BACKGROUND TO MOTT&apos;S APPROACH Hildebrand applied his immiscibility rule for non-polar liquids to various alloy systems.9 The basis of this rule is that the equation for the excess free energy of formation of a liquid solution is rather similar to the theoretical expression for the energy of mixing of a regular solution. He postulated that when the heat of mixing is sufficiently high, separation into liquid phases will occur and the condition for complete CUPPAM DASARATHY is at the Research Centre, British Steel Corporation, (South Wales Group), Port Talbot, Glamorgan, Great Britain. Manuscript submitted March 12, 1969. IMD miscibility was shown as where VA and VB were the atomic volumes of the components A and B, and ?EV the energy of vaporization of the component. The term (?EVA/VA)1/2 was regarded as a measure of the binding energy of the component A and was called the L&apos;solubility parameter" 8A. On this basis immiscibility occurs when 1/2(VA+VB)(bA-bBf > 2RT [2] Apparently, however, there were several inconsistencies in that according to Eq. [2] several systems known to be miscible in the liquid state were predicted as immiscible. MOTT&apos;S ANALYSIS ~ott&apos;" regards that the reason for the inconsistencies arising out of Hildebrand&apos;s equation was largely due to the electrochemical attraction between the two elements, not being considered. Hence, Eqs. [I] and [2] were modified by taking into account the electro-negativities of the two elements XA and XB, and Mott arrived at an equation for immiscibility, i(VA + VB)(6A - aB)2 - 23,Q60n(XA - XBf > 2RT [3j which can be written as i **&£*&* >&apos;*°™- &apos;• HI T being the melting point of the more refractory component of the system. In Eq. [4], the numerator was called the Hildebrand term, the denominator, the electronegativity term, and their ratio, the Mott number. Mott observed that if the Mott number of a given binary system was greater than the maximum number of Pauling bonds which the two metals could form, then liquid immiscibility could be expected. The maximum number of bonds formed by a given metal was considered to be directly related to the number of bonding electrons available, i.e., to its maximum valency. Since the valencies of the elements considered vary from 1 to 6, Mott assumed that if the ratio of the Hildebrand term to the electronegativity term was >6, then immiscibility could be expected. On the contrary, if the ratio is <1, the metals should be miscible. Further, the alloying behavior is not only influenced by the valencies of the two elements but also by the relative atomic sizes that influence the types of packing and hence the coordination number. Mott considers that on average the maximum number of near neighbors of unlike atoms is 6. Thus, on both valency and size factor considerations, Mott concludes that the maximum number of bonds&apos; possible in any system was 6, this being the upper limit of the Mott number for miscibility. In considering the alloying behavior of systems with Mott numbers between 1 and 6, Mott plotted the num-

Jan 1, 1970

By W. T. Malone, J. R. Williams, R. L. Tiner, J. M. Tinsley

Hydraulic fracturing methods for production stimulation have become a common procedure in the oil and gas industry. Fracturing treatments are performed on wells of various potentials to help increase the production rate. In addition to the desire for increased production is the need to predict what increase might be expected. This knowledge is useful in economical treatment planning to accomplish the desired production goals for the well. Theoretical production increases due to horizontal radial fractures may be calculated using equations developed from mathematical analyses and electrical models.1,2,6 It also is possible to predict theoretical production increases due to vertical fractures using curves developed from electrical3 and mathematical models.8 However, these studies assumed that the vertical fracture height and the formation height were equal, which may not be true." In addition, the final fracture height through which fluid is produced may not be equal to the created height. The development of vertical fracture proppant transport relationships has made unrealistic the assumption that propped fracture height is equal to created fracture height. Through the use of published proppant transport equations,4&apos;12 it is possible to calculate the height of a bed of propping agent deposited in a fracture of a given height. Assuming that the fluid flowing in the fracture moves through only the propped portion of that fracture (i.e., that the un-propped part of the fracture heals) it becomes essential to know how production increase varies with the ratio of propped fracture height to formation height. It should be recognized that future investigation may determine that the fracture does not heal completely and that a highly permeable channel exists over the deposited bed of proppant. The effect of this channel was not considered for the present study. The following analysis of experimental data allowed development of curves to determine theoretical production increases considering fracture height as a variable. Discussion In designing a fracturing stimulation treatment a number of variables must be considered. The size of the treatment, type of proppant used, proppant concentration, treatment fluid properties and well conditions are all factors affecting the dimensions and permeability of the fracture. Production increase due to a vertical fracture is affected by propped length, height, width and permeability of the fracture for a given set of formation conditions. Production increase may be defined as the ratio of production rate after fracturing to the production rate before fracturing at the same pressure differential, pe — pw. The producing rate in an

Jan 1, 1970

By Larman J. Heath

Wellbore enlargement was tested using hydrazine hydrate in a gas-storage well in Ohio to increase the well productivity. The wellbore was to be enlarged by chemical disaggregation of the sandstone adjacent to the wellbore. Productivity immediately declined 49.1 percent and gradually declined to zero in 7 months. A down-hole camera survey showed a white-to-gray precipitate covering the entire wellbore surface. The precipitate was chemically analyzed and identified as mostly carbazic acid, a hydrazine derivative of carbonic acid. Formation of this precipitate was not anticipated; this viscous sub-stance caused the gradual loss in productivity of the well. The wellbore was not enlarged. Laboratory tests were run to determine what clay stabilization measures could be taken in sandstone cores to prevent clay swelling and particle migration caused by hydrazine hydrate. Normal clay stabilization methods did not prevent the virtually complete loss in permeability to hydrazine hydrate. Other laboratory tests using natural gas diluted with small amounts of carbon dioxide confirmed the ease with which carbazic acid could be formed in a hydrazine hydrate-saturated environment within and adjacent to the wellbore.

Jan 1, 1970

By R. L. Whiting, H. J. Ramey

The basic study from which this paper was prepared was started as the result of the growing need throughout the world for increasing quantities of energy in all forms. Quite obviously, natural forms of energy that are readily available at low development cost are those in greatest demand. The underdeveloped countries — and particularly those having little or no petroleum resources — are the countries in which the most interest is being shown in the newer energy sources. One of the least expensive energy sources is natural geothermal steam.&apos;-* Although this form of energy has been recognized for centuries, it has been only during the past 20 years that serious efforts have been made to harness it. Natural geothermal steam energy in Italy, New Zealand, Mexico, Japan, and California is now being produced through wells to drive turbines and generate electricity. Further, active exploration for natural geothermal steam is being conducted in Hawaii, Fiji, Taiwan, Chile, Russia, Greece, and Katanga. It is surprising to find that most geothermal steam exploration is in the "steam seep" stage. That is, surface studies are made and exploratory wells are drilled in the general area of steam seeps. However, in the larger geothermal steam areas, there have been efforts to apply the most modern geological and reservoir engineering principles in order to define the reservoir parameters, particularly those relating to estimates of reserves and future productivity. This paper is concerned with the development of appropriate equations and techniques to facilitate these estimates. Production of natural steam or hot water presents problems different from those experienced in the production of oil and gas. For example, steam or hot water systems may be essentially single-component systems, while hydrocarbon systems are most frequently multicomponent fluid systems. Heat effects are much larger for water than for hydrocarbon systems; and the natural steam production may or may not be isothermal, while production of petroleum reservoirs is considered normally to be isothermal. Petroleum reservoir engineering principles may be applied to natural steam or hot water reservoirs if the inherent differences in the systems are considered. The basic considerations involved in geothermal steam reservoir engineering are: thermodynamics, physical and thermal properties of water, materials and energy balances, fluid influx, and performance matching and predicting. Thermodynamics Fig. 1 is a pressure-temperature diagram for the liquid-vapor region for pure water, showing the critical point and five other points representing possible initial conditions for a geothermal steam reservoir. To generate a physical appreciation for the mechanics of natural steam production, it is helpful to consider

Jan 1, 1970

By K. Thirumalai

This study forms a part of Bureau of Mines continuing research on thermal fragmentation of rocks. The potential of internal heating techniques for rock fragmentation is discussed. A concept of rock fragmentation with rapid inter¬nal heating of a localized inner volume of rock is advanced The energy required for rock fragmentation is made available by creating a required vol¬ume of localized heating. The fragmentation of rock using the proposed method is analyzed and qualitatively compared with the results of experiments with Charcoal granite, Dresser basalt, and Sioux Quartzite. High frequency dielec¬tric heating below 100 MHz is used in the study as an example to examine the working of the concept. The selection of operating conditions for the experi¬mental heating is explained. Fragmentation of Charcoal granite and Dresser basalt test rock blocks is achieved for localized heating below 550° C. The heated volume required for fragmentation is observed to be less than 2 percent of the test block volume and the electrical energy consumption is in the order of 3.5 to 6 5 kwhr/m3 The method offers a possibility for in situ fragmenta¬tion of rocks, favorable for internal heating. The method is highly dependent on rock properties governing internal heat generation The efficiency of dielectric heating in the experimental study is observed to increase with increasing dielectric loss of the rock material, ranging from about 10 percent in Sioux. Quartzite to about 50 percent in Dresses basalt

Jan 1, 1970

By S. Akhtar

Interstitial compounds of iron, cobalt, and nickel, and their binary and ternary mixtures with silver, gold, palladium, and platinum were prepared and tested as fuel cell catalysts. The first step in the preparation of the interstitial compounds consisted of preparing finely divided metals. This was done either by the Raney method or by reduction of precipitated hydroxides of the metals. The finely divided reduced metals were then treated with carbon-and/or nitrogen-containing gases to prepare their carbides, nitrides, and nitrocarbides. The materials were tested for cathodic activity towards O2 and for anodic activity towards H2, C3H8, NH3, CO, and N2H4 in acid and alkaline electrolytes at 25° to 90° C in half-cell assemblies. Samples of carbided and nitrocarbided INi-lAg-1Au were about one fifth as active as Pt-black in the reduction of O2 in 35 percent KOH solution, whereas the activities of several interstitial preparations exceeded the activity of Pt-black in the reduction of O2 in 12M KOH containing N2H4. Nitrocarbides of x-Fe2C, 3Ni-1Au, and 1Ni-3Au were effective catalysts for oxidizing N2H4 in liquid NH3 containing NH4SCN. Corrosion of the catalysts by electrolytes was severe in many cases.

Jan 1, 1970

By Meyer Klein

Decision theory is the formal theory of the logic of decisions in view of the decision maker&apos;s objectives, preferences, I beliefs, and available information, It usually deals with weighty economic problems involving irrevocable (or costly to reverse) decisions. Capital investment planning problems constitute an instance par excellence for application of the decision theory concepts. Decision theory as it is presently conceived has evolved in recent years. At first it concentrated on decisions in the face of total lack of information and on games with intelligent adversaries. The results of these efforts proved theoretically interesting, but practically of little applicability. In the last few years, stress has shifted to the introduction of subjective probabilities and preferences, and the results have been eminently successful in applications both in government and with- in business firms in the resolution of complex problems.

Jan 1, 1970

By Joseph L. Condon

Fifteen shots of three explosives with charge weights of 0.52, 1.1, 3.1, and 5.1 kilograms were fired in a pond to study the seismic effects of detonating explosives in water. Shock pressures and bubble periods were measured with pressure transducers in the water. Vibrations were measured on land in three orthogonal directions with particle velocity gages. Statistical tests indicated that a charge weight exponent of 0.43 best scaled the data. While shock pressures and bubble periods showed considerable differences in explosive performances, the amplitudes of ground vibrations showed less difference, and one prediction equation was therefore derived to estimate vibration amplitudes from all the explosives.

Jan 1, 1970

By D. A. Keefe, O&apos

The electrowinning of beryllium from beryllium oxide (BeO) using a molten-salt electrolyte composed of 56 LiF-37 BeF2-7 BeO (mole-percent) was investigated. Anodes made of porous carbon were found to be superior in current-carrying capacity and gave a lower cell voltage than other types of anode material tested. When porous carbon anodes were used) the resultant increase in anode area prevented anode passivation. The cell voltage was 3.3 volts) and electrode current efficiencies of 50 to 70 percent were obtained. The electrodeposited beryllium was recovered as beryllium powder or was coalesced to metal beads by heating to 1,300° C.

Jan 1, 1970

By H. R. Babitzke

As part of a continuing project to develop refractory metal alloys for high-temperature structural applications, the Bureau of Mines applied solid solution and precipitation strengthening techniques to improve the properties of columbium alloys. The purpose was to investigate the effects of hafnium, tungsten, and boron on the formability, strength, and oxidation resistance of columbium. The experiment was of factorial design with two replications which called for 72 ingots of 36 basic compositions, weighing 150 grams each. Hafnium, tungsten, and boron were evaluated at 3, 3, and 4 levels, respectively. Values of alloy content are all in atomic percent. The highest strength observed was 29,000 psi at 1,200° C for alloys Cb-15Hf (No. 3), Cb-7.5Hf-5W-2B (No. 14), and Cb-15Hf-5W-2B (No. 15). At 1,200° C, the ternary alloy Cb-15Hf-5W (No. 6) which has shown good properties in previous Bureau of Mines investigations was the most resistant to oxidation For boron additions, the alloys oxidized more readily with increasing amounts of this element. The fabricability of the alloys high in boron became increasingly difficult, resulting in an inadequate number of alloys required for a complete statistical analysis for all the tests. As a result of the decrease in ductility, an insufficient quantity of tensile samples were available for a proper analysis for the high-temperature strength data.

Jan 1, 1970

By J. E. Terry

This paper outlines the steps that are being taken to close the gap between training and industry and indicates areas in which more work needs to be done. Although based on experience in the Maritime Provinces, it is applicable to industrial and educational studies across the length and breadth of Canada.

Jan 1, 1970

By V. A. Cammarota

In this report, the effects of anode-production variables, such as aggregate coke sizes, pitch binder content, and baking cycle, were investigated. A small alumina reduction cell proved effective in evaluating anodes prepared from commercial materials and from lignite coke and pitch. Compressive strength was found to be the physical property most significantly influenced, but it did not appear to affect anode consumption. Specific carbon consumption, that is, the ratio of carbon in the anodic gas to carbon theoretically oxidized at the anode, was used as an index of anode consumption. It was found that an anode made with lignite coke and commercial pitch was very low in consumption; however, anodes made completely from lignite but by a different fabrication method showed high consumption and anode deterioration. Microscopic examination of anodes after electrolysis showed evidence of higher consumption at low current densities, and was useful in judging overall anode quality. Based on the physical properties of the anodes and their consumption during electrolysis, lignite can be a suitable material for anodes, provided the proper fabrication conditions are used.

Jan 1, 1970

By D. E. Kirby

The electrochemical reduction of AlC13 was investigated as a process for the production of aluminum. An externally heated, single-compartment cell with a rammed refractory lining was used with molten KCl-NaCl-AlC13 electrolyte. Aluminum was deposited qt 700° to 760° C with a current of 100 to 200 amperes on a molten aluminum cathode. Chlorine was evolved at a graphite anode and collected and measured to provide a quantitative evaluation of the AlC13 reduction. Aluminum was removed from the cell by siphoning or ladling. Granular AlC13 was added periodically to replenish that depleted from the electrolyte. Concentrations of 7.5 to 17.5 percent AlC13 in the electrolyte were optimum for operation. Anode current efficiencies of 83 to 85 percent were attained, using anode current densities of 5.9 amperes per square inch and an anode-cathode distance of 4 inches. The chemically bonded, alumina liner was resistant to attack by aluminum and chlorine but susceptible to erosion at the surface of the electrolyte. Titanium diboride proved suitable for the electrical connection to the molten aluminum cathode. Aluminum of a purity equal to or better than 1100 series metal was electrowon continuously from commercial AlC13 for a period of 4-1/2 months.

Jan 1, 1970

By A. U. Seybolt, R. E. Honnemon

THE purpose of this communication is to present activity data of nickel in the Ni-A1 binary system that was obtained for oxidation studies in this system. This data has been calculated from previous aluminum activity data at 1000°C1,2 by two types of Gibbs-Duhem integrations. These results should be of particular current interest to oxidation studies of aluminide coated nickel-base superalloys3 as well as other problems. The aluminum activity of Steiner and Komarek1 is plotted in Fig. 1 as a function of composition in Ni-A1 alloys at 1000°C. The dashed parts of the aluminum curves represent our approximate extrapolations from the directly measured regions. In the terminal solution regions (a and L phases) standard parabolic solution functions of the following form are assumed: where i is the component subscript, Ki is a constant at a fixed temperature, and xi is the atom fraction. The resultant nickel activity curve at 1000° C from the Gibbs-Duhem integration4 of the aluminum data is shown in Fig. 1. The solubility ranges of the phases present in the Ni-A1 binary at 1000°C are also denoted at the bottom of Fig. 1. Corresponding values of the nickel activity, aNi and yNi, are listed in Table I at useful compositional intervals. including phase boundary values. The aNi and yNi data listed in Table I are subject to the uncertainties present in the experimental aluminum activity data1 and to deviations from parabolic solution behavior in the terminal solutions. The errors introduced into aNi and yNi due to the parabolic solution assumption are expected to be relatively small (<20 pct of the values given) in all the phases except the liquid phase. Some deviation from parabolic solution behavior in the liquid phase is indicated

Jan 1, 1970

By F. S. Young

Previous laboratory and field experimentation has demonstrated the effect of several variables on drilling rate.1-5 These results have been incorporated into optimization theories6-" for the purpose of reducing drilling cost. Minimum-cost drilling theories rely on a combination of historical data and empirical prediction techniques for selecting optimum bit weight and rotary speed. Past solutions have required extensive use of computing equipment because of both the complexity of the mathematical formulations and the large number of parameters involved. Field attempts to apply these computed results have frequently failed because of the uncertainty of input data requirements. Humble has developed an on-site computer system to control bit weight and rotary speed and thereby implement the concepts of minimum-cost drilling. This system can (1) perform short interval drilling rate tests for formation evaluation, (2) use the results of these tests as input information to solve minimum-cost drilling formulas, and (3) control bit weight and rotary speed in accordance with these computed solutions. The purpose of this paper is to describe the computer control system and present results of initial field testing. Theoretical Considerations Minimum-cost drilling (MCD) requires a quantitative evaluation of the variables involved. Several forms of a basic mathematical model have been sug-gested.&apos;?,&apos; "he relationships reported here form the basis for the solution programmed in this work. Four equations are used, expressing drilling rate, bit bearing wear, bit tooth wear, and cost. A solution for minimum-cost drilling assuming constant bit weight and rotary speed over the entire bit life has been programmed for use in computing MCD schedules. This solution is subject to certain limiting assumptions such as those discussed by Graham et a1.I2: 1. Drilling cost is the summation of bit cost, rotating cost, connection cost and hoisting cost. 2. Diamond bits are excluded. 3. Bit life is limited by either bearing failure or tooth wear, or by a combination of operational factors that make it cheaper to pull an incompletely consumed bit. 4. Circulating hydraulics are adequate and do not limit drilling rate. 5. Bit weight considerations exclude hole deviation. 6. Drilling rate is a function of only bit weight, rotary speed, and degree of tooth dullness; that is, the effects of pressure, lithology, fluid properties hydraulics and drill string dynamics are ignored. In equation form, the four MCD expressions are as follows:

Jan 1, 1970

By R. C. Earlougher

Jan 1, 1970