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By Ben L. Seegmiller

Artificial support of rock slopes in mining applications may consist of rock anchors with and without auxiliary support systems, but- tresses or shotcrete. The use of artificial support systems is not applicable in all cases of slope instability. Some pit slope problems simply cannot be cured with a support system. In other cases, a sup- port system which would solve the problem would be uneconomical. Rock anchor design may be undertaken using an active or tensioned system or a passive or untensioned system. Failure problems to which artificial support systems are most commonly applied include planar, wedge, rotational and toppling failures. Design of auxiliary support systems and rock anchor peripheral items may be initially estimated using analytical concepts, but field trials are commonly used to determine final requirements. Field procedures usually require a close coordination between mining personnel and the support installation team. Great care must be exercised during installation to prevent numerous potential problems including poor anchorage, excess bearing and corrosion. Displacement monitoring of the completed system is a must if the effectiveness is to be closely judged by means other than total slope and/or support system failure. The cost of a support system is relatively high when compared to other remedial measures that may be taken to solve a slope instability problem. Therefore, the system costs play a vital role in determining whether or not artificial support should be considered beyond the initial assessment stage. Case histories are few, but do include examples of each type of support system.

Jan 1, 1983

In a straight caving system, the ore is first undercut and then broken down by its own weight or .by the weight of the overlying rock, or by a combination of both. Operations that involve the caving of the material overlying an orebody as an essential part of the work are also classed as caving, though practically all the ore is broken by drilling and blasting. Actually there are two distinct methods—sublevel caving and block caving, and modifications thereof. The mines described are Miami and Alaska Juneau.

Jan 1, 1925

By F. G. Cottrell

About a year and a half ago, at the San Francisco meeting of the American Chemical Society, in connection with the excursions to local smelting-works, I had occasion to show some lantern-slides illustrating the recent commercial development of electrical methods for precipitating the suspended matter from smelter-smoke, the underlying phenomena of which were clearly brought to the attention of the technical public by Sir Oliver Lodge as long ago as 1884. In the .Journal of Industrial and Engineering Chemistry, August, 1911, most of these views were reproduced, together with an account of the work from its beginning up to July, 1911. To-day I wish particularly to show you some of the further developments of the work since that time; but in order to make these clear they will be prefaced by a brief abstract of the article above referred to. The removal of suspended particles, from gases, by the aid of electric discharges is by no means a new idea. As early as 1824 we find it suggested by Hohlfeld ' as a means of suppressing ordinary smoke, and again a quarter of a century later by Guitard.2 These suggestions, which do not seem to have stimulated any practical study of the question, were soon entirely forgotten, and only brought to light again by Sir Oliver Lodge: many years after he himself had independently rediscovered the same phenomena and brought them to public attention4 in a lecture before the Liverpool Section of the So-

Jan 1, 1913

By L. A. Wright, H. L. McKinley

PINE Creek mine of Union Carbide Nuclear Co. is some 23 miles northwest of Bishop, Calif., in the Sierra Nevada Mts. Office and mill are 7800 ft above sea level, the 1500 level portal is at 9300 ft, the A level portal at 10,800 ft, and the 3050 portal at 11,500 ft. Original claims were located in 1916, and the mine worked intermittently until 1936, when it was purchased by Union Carbide Corp. Since then the property has been operated continuously, except for two brief periods when operations were suspended because of manpower shortages. Mine production through 1956 amounted to 2,792,425 dry tons of ore.

Jan 10, 1957

By H. P. Greenwald, H. C. Howarth

The rapidly increasing use in coal mines of portable auxiliary fans, which are generally 'blowers" employed in connection with canvas tubing, raises questions concerning the hazards of such equipment, especially where the practices are opposed to established methods of ventilating face workings. Half a dozen or more coal-mine explosions and some fires have been attributed to the use of auxiliary fans; moreover, competent mining engineers have found many dangerous installations and methods of use-for example, intermittent running of the fans in gassy mines with consequent accumulations of firedamp at the faces. These facts have led the U. S. Bureau of Mines to issue this recommendation: "In the interest of safety, the Bureau of Mines, Department of Commerce, recommends that auxiliary fans or blowers should not be used in coal mines as a substitute for methods of regular and continuous coursing of the air to every face in the mine." The comparatively recent introduction of new types of mining machines, mechanical loaders, face conveyors, and slabbing machines has encouraged the trial of new systems of face mining, all of which have for their object the rapid advance of the faces. Although the latter has certain economic advantages, in gassy mines the rate at which gas is given off is generally found to increase in proportion to the speed of advance into new territory, which in turn increases the difficulties of efficient ventilation of the face workings. Some of the systems of advance mining being tried in connection with new mechanizing methods practically compel the use of blower fans and tubing, as single narrow places arc now driven 300 ft. or more without crosscuts. In some instances a series of parallel headings are driven without crosscuts pre-

Jan 1, 1928

By R. A. Sharma, F. D. Richardson

Manganese oxide acitivities and sulfide capacities have been measured at 1650°C in mixtures of MnO + A1203 and MnO + SiO2 - Al2O3. Sulfide capacities have also been measured at 165O0C for melts of MnO + SiO2, MgO + SiO2, MgO + SiO2 + Al2O3, MgO + MnO + SiO2, and SiO2 + Al2O3 and for crystalline CaO. The activity coefficients of the sulfides of manganese and magnesium have been derived where possible. It looks as though the activity coefficients of sulfides are greatest at compositions where the free energies of formation of the silicate mixtures have their maximum negative values. The amphoteric nature of alumina is reflected in the results for the binaries and ternaries in which it is present with silica. The limiting solubility of CaS in CaO at 1650°C is 6.3 x 10-4 mole fraction. THE activities of manganese oxide have been measured in a variety of silicate and aluminate melts by use of the equilibrium (MnO)slag = [Mn]pt .½O2 [l] and the experimental techniques described previously.' Sulfide capacities (CS = wt pct S (PO2/PS2)½) have also been determined in a series of melts, by use of an established method2 which exploits the equilibrium (O°) + ½S2 = (S") . ½O2 [2] If CS and the activity of a metal oxide are known in a melt, the activity coefficient of the metal sulfide can be calculated by use of the equilibrium constant K, for the pure phase reaction MO i ½S2 = MS + ½O2 [3] The activity coefficient of the sulfide is then given by the equation

Jan 1, 1965

By Douglas Bunting

The first presentation of this paper was before the Pennsylvania Anthracite Section of the Institute in May, 1914, after which a committee was selected to verify and add to the data contained in the original paper. The author is indebted to G. W. Engel, H. W. Montz, R. V. Norris, and H. H. Otto, of this committee, for additional information. I also wish to acknowledge the courtesies extended me by a number of the mining companies for information relative to accidents, systems of proving, and mining practice. The paper should bring forth additional criticism and recommendations, which will be of value in establishing future practice relative to this subject. Throughout the northern anthracite field of Pennsylvania glacial and alluvial deposits of sand, gravel, and clay exist in varying quantities. The extent and character of these deposits are described by N. H. Darton in Bulletin 45 of the U. S. Bureau of Mines, entitled, Sand Available for Filling Mine Workings in the Northern Anthracite Basin. It is estimated that the northern field contains 10,000,000,000 tons of these deposits, or a sufficient quantity to cover the 176 square miles of coal area to a depth of about 25 ft. These deposits of sand, etc., overlying the coal measures attain a maximum depth of more than 300 ft., and are usually saturated to such an extent as to render them semi-fluid. It is this condition of fluidity that limits the mining of coal seams cropping in or in close proximity to these deposits, and it is in the interest of safer and more efficient mining methods under these conditions that the study of this subject is here presented. The dangers incident to mining under deep deposits of sand have long been realized by operators in the northern anthracite field, and much has been done to prove the contour of the rock and vein croppings underlying these water-bearing deposits of sand and gravel. Although, as far as we know, the accidents of the past have not resulted in the loss of life, except in two instances, yet nearly all were attended with more or less miraculous escapes of men working in the vicinity of the breaks, so that the probable existence of pot holes, etc.,

Jan 1, 1915

By John Birkinbine

The experience of the past five years has furnished opportunities to study and to partially explain the operation and some of the causes of the short blast of Warwick Furnace at Pottstown, Pennsylvania, as described in the paper read at the Lake Superior Meeting, in August, 1880.* The many inquiries concerning the details of furnace operation which followed the publication of the paper, and the expressed desire of furnace managers to be informed as to future operations of this plant, have encouraged the preparation of the following data. To make the record continuous, and add to the value of both contributions, the present paper commences where the review of a short blast of Warwick Furnace ended, and includes the data of another short blast of two months, and a subsequent continuous campaign of nearly five years, which, by comparison, we shall designate as "the long blast." Frequent visits to the plant in the five years, during which its operation could be studied, and correspondence with the manager, Mr. Edgar S. Cook, have given a knowledge as to general features and details, and the courtesy of the officers of the Company which has given free access to the books of record permits the presentation of data which it is believed will be welcomed by furnace managers. Interest will undoubtedly be increased by the remarkable results which Mr. Cook has achieved chiefly with anthracite coal in a furnace whose details of construction will scarcely be generally admitted as embodying advanced ideas, its height being but 55 feet, with a bosh diameter of 15 feet 6 inches, its bosh-slope comparatively flat, its crucible smaller than the average, and the heat of the blast never reaching 1000' Fahrenheit. At present writing the credit of the best anthracite blast-furnace practice recorded in our Transactions is conceded to be that pursued by Mr. Fackenthal, at the Durham furnace, and Mr. Cook, at War-

Jan 1, 1886

By Charles A. Ashburner

' I. Natural-Gas Explorations. The rapid development of the natural-gas* industry in Western Pennsylvania, and the great economy which results from its use, both for manufacturing and domestic purposes, has led to an inquiry as to the occurrence of this gaseous mineral in all thickly populated and large manufacturing centers of the United States. Natural-gas springs are to be found in almost every State in the Union, and in many States gas has been obtained in wells sunk either for water, oil, or gas, or in search of solid mineral deposits. The occurrence of natural gas is, however, not dependent upon mere chance, as is popularly supposed, but upon the existence of special geological phenomena; this fact is now recognized by professional men and by many practical men concerned either in the exploration for or in the use of this gas. The desire among our leading manufacturers, to emulate Pittsburgh, has led to the sinking of many wells in many localities, in search of natural gas. Some of these wells are now being located and drilled under the direction of professional experts, but many more have been, and are still being located by "quack " explorers, who often depend upon spiritualistic communications, or the diviningrod, or by intelligent persons, who are ignorant, however, of the geological and physical conditions under which gas has already been found. My attention has recently been directed to a number of these exploring operations where holes have been drilled, and, after failing

Jan 1, 1887

LIST OF MEMBERS AND ASSOCIATES ARRANGED ACCORDING TO STATES AND TOWNS ALABAMA Aldrich, Aldrich, W F Anniston, Noble, A E, Smith, N B Aibacoche, Bradley, D II Bessemer, Fergusson, V Birmingham, Aldrich, T H, Aldrich, T H, Jr, Bowron, J, Bowron, C E, Davis, F H, Dimmick, F D, Hillman, McCarthy, M E , McCormack, McCrery, Ramsay, E, Shook, A M Bridge¬port, Wheeler, S K Ensley, McDonald, S, Shook, J W Fanbanks, Hamil¬ton, A L Helena, Squire, J Huntsville, Moss Lehigh, Toulmin Oxmoor, Green¬amyer, A G Plasma, Gage Rock Run, Garvin Sheffileld, Miller, D I Tuscaloesa, Lodge, J University, McCalley Woodward, Bukofzer, Woodward, A H ALASKA Dawson, Buck Douglas Island, Corbus, J P , Macdonald, J Hames, Le Wald, E A Jualin, Hoggatt, W B Juneau, Denby, Gaifield, Garside, Hamp¬ton, W H Rodman Bay, Phillpots Snettisham, Tisdale Sumdum, Thane Tel¬ler, Hirshberg, M R Treadwell City, Batcheller, J H , Kinzie Valdez, Esterly, G M Yukon, Dawson, Elmer, J M ARIZONA Bisbee, Clark, G C, Coombs, H L , Douglas, W, Hoatson, Parnall, S A, Pelton, R T, Ricketts, L D, Sherman, G F G, Smith, F W, Smith, H A Black Diamond, Bagge Blanchard, Cummins, Murray, J J Casa Grande, Rich¬mond, A B Clifton, Colquhoun, Grabill, Murray, H T , Plater, Smith, J D A, Veitch, Watson, W S Congress, Goodloe Crown King, Alexander, G E Douglas, Cornell, Kraemer, E L, Lee, G B, Rutherford, F Globe, Berray, Hoar, Snell Harrisburg, Smith, F C Jerome, Clark, W A, Thomas, C A Kingman, Treadwell, Wallace, J P Kirkland, Bretherton, G K Kofa, Lamp¬shire, J O , Pomeroy, H G Mayer, Haggott, E A Metca j, Blumenkranz, M , Forbes, D L H Morenca, Clark, C D, Fleming, J B, Honey man, Mills, C E, Wallace, L R Morristown, Stevens, H W Nogales, Glove, H G, Sandoval, A , Sandoval, P Octave, Rose, G W Phoenix, Armstrong, T , Butler, C E, Defty, Lindsay, L Prescott, Blauvelt, H , Bunker, C E, Claypool, W M , Drescher, F M , Fairbank, Nissen Tombstone, Gage, Poindexter, C L , Staunton, Walker, E W Troy, Cutting Tucson, Blake, W P, Burgess, De Lashmutt, I, McCleary, Mann, Prout, J W , Jr ARKANSAS Fayetteville, Purdue Fort Smith, Bache, F , Denman, H Little Rock, Fordyce, Scholz CALIFORNIA Alameda, Arents, King, L Arnador City, Downs, Tregloan Angeles Camp, Dig¬gles, R N , Kenney, C E Antioch, Belshaw Auburn, Coe, I J Ballarat, Thorns Berkeley, Abadie,, Christy, Dozier, Hall, F F , Hersam, Landfield, Lind¬say, L , Mansfield, N T, Morley, W S , Sharwood, W J Bag Oak Flat, Dron Bodae, Hamilton, W R, Hoover, T, Hoover, T J, Jackson, B L , Nutter , E, H Bullion, Power, H T Callahan, Scott, E H Campo Seco, Baird Cartero,

Jan 1, 1910

By Paul Sterling

The general impression regarding the preparation of merchantable anthracite is that it is confined to a colossal, grimy structure, called a " coal-breaker." This name is a misnomer; for the desired result is not to break the coal, but to prevent its being broken. Preparation may be said to begin at the face of the chamber, with the mining and loading of the coal. Local conditions vary, not only ill the same field or basin, but also in the same mine, so that there is no fixed empirical rule governing the method of blasting or cutting coal. Tests should be made, when possible, to determine the explosive, or the mechanical coal-cutter, which will produce the largest percentage of what are locally known as " lump " and " prepared sizes " of anthracite. The prepared sizes are those mostly consumed for clomestic purposes. All other sizes might be called by-products of the anthracite industry; for they are not especially desirable, being the degradation resulting from the mining and handling of a brittle or laminated material. Being low in volatile combustible matter, anthracite burns most successfully when nearly of a uniform size, permitting the easy passage of air through the voids. This accounts for the large number of sizes into which the coal is separated. Table I. gives the various sizes, the diameter of ring over and through which each size is made, and the usual purpose for which it is employed.

Jan 1, 1912

By Carlton D. Hulin

The usual concurrence in time and space of intrusive igneous activity, favorable structural disturbance and mineralization, which is so manifest in the mineralized district necessarily indicates a close interrelationship between these events. Evaluation of available evidence leads to the recognition that an appreciable time interval exists between the emplacement of the igneous intrusive and the formation of associated ore deposits. During this interval known portions of the intrusive are completely solidified, highly differentiated magma facies are injected as dikes, and important faulting occurs, which may fracture and shatter the solidified intrusive body. The highly differentiated dike types could only have originated in some deep portion of an underlying plutonic body that had reached an advanced stage of magmatic differentiation. Appearing after these dikes, the mineralizing solutions may likewise be presumed to have originated at great depth. Certainly no source for these solutions can be found in near-by portions of the intrusive igneous body. The association of igneous intrusives and clustering ore deposits must be recognized as resulting from structural control. The emplacemerit and the subsequent solidification and cooling of the intrusive set in operation forces that are responsible for the favorable structural disturbances that control the mineralized district. The emplacement of the body of fluid magma weakens the crustal rocks to the extent that failure due to strains originally present in the rock body may occur. Faulting of any type and of any magnitude may be the result. Subsequently, owing to the change of state from fluid magma to crystalline granitic rock, volume decreases approximating 10 Per cent may Occur, with resultant shrinkage and collapse within the rock body. Following solidification, thermal contraction, induced by cooling of the rock body, causes a further volume reduction of 6 per cent. This thermal contraction, extending over a lengthy period of time, results in a succession of minor fault movements. These small fault movements, occurring progressively throughout the period of mineralization, are responsible for maintaining the permeability of the rock body, without which access of the mineralizing solutions and the formation of the ore deposits of the mineralized district would be impossible. Introduction A proper understanding of the causes that have localized our mineralized districts should be of considerable value to geologist and engineer alike. under current conditions the known ore reserves of productive mining camps are being rapidly depleted. Although ore of the future will be derived in part from deposits now known and from Ore bodies that are still to be discovered within the limits of productive mining districts, in part at least it must come from mineralized districts whose existence or importance yet remain to be recognized. The mining geologist is thus faced with two problems of paramount importance: (I) the location of new ore bodies within known mineralized areas and (2) the location of new mineralized districts within whose confines, previously unknown, valuable Ore deposits may occur. Any contribution to our knowledge concerning the causes for the localization of mineralized districts

Jan 1, 1949

By Carlton D. Hulin

The usual concurrence in time and space of intrusive igneous activity, favorable structural disturbance and mineralization, which is so manifest in the mineralized district necessarily indicates a close interrelationship between these events. Evaluation of available evidence leads to the recognition that an appreciable time interval exists between the emplacement of the igneous intrusive and the formation of associated ore deposits. During this interval known portions of the intrusive are completely solidified, highly differentiated magma facies are injected as dikes, and important faulting occurs, which may fracture and shatter the solidified intrusive body. The highly differentiated dike types could only have originated in some deep portion of an underlying plutonic body that had reached an advanced stage of magmatic differentiation. Appearing after these dikes, the mineralizing solutions may likewise be presumed to have originated at great depth. Certainly no source for these solutions can be found in near-by portions of the intrusive igneous body. The association of igneous intrusives and clustering ore deposits must be recognized as resulting from structural control. The emplacemerit and the subsequent solidification and cooling of the intrusive set in operation forces that are responsible for the favorable structural disturbances that control the mineralized district. The emplacement of the body of fluid magma weakens the crustal rocks to the extent that failure due to strains originally present in the rock body may occur. Faulting of any type and of any magnitude may be the result. Subsequently, owing to the change of state from fluid magma to crystalline granitic rock, volume decreases approximating 10 Per cent may Occur, with resultant shrinkage and collapse within the rock body. Following solidification, thermal contraction, induced by cooling of the rock body, causes a further volume reduction of 6 per cent. This thermal contraction, extending over a lengthy period of time, results in a succession of minor fault movements. These small fault movements, occurring progressively throughout the period of mineralization, are responsible for maintaining the permeability of the rock body, without which access of the mineralizing solutions and the formation of the ore deposits of the mineralized district would be impossible. Introduction A proper understanding of the causes that have localized our mineralized districts should be of considerable value to geologist and engineer alike. under current conditions the known ore reserves of productive mining camps are being rapidly depleted. Although ore of the future will be derived in part from deposits now known and from Ore bodies that are still to be discovered within the limits of productive mining districts, in part at least it must come from mineralized districts whose existence or importance yet remain to be recognized. The mining geologist is thus faced with two problems of paramount importance: (I) the location of new ore bodies within known mineralized areas and (2) the location of new mineralized districts within whose confines, previously unknown, valuable Ore deposits may occur. Any contribution to our knowledge concerning the causes for the localization of mineralized districts

Jan 1, 1949

By V. Koump, T. F. Perzak, R. G. Olsson

The vate of dissolutioz of carbon in molten Fe-C alloys urns studied by votating- cylindrical g-vaphite sairlples in a stationary crucible containing the melt. The rate of dissolltion was determdined from the change in the bnth co)npositiorz. Alccss-tvansfev coeffi'cients, calcilated with the assurlption that the inte)yacial liquid ulas saturated with carbon, were found to be in agreement with an existing Correlation fov mass transfer jroni votating cylinders. It is corzcllrded tlat, itz the wnge of- Reynolds' numbers itzvestigated (790 to 18,000), the vate of dissolutio of carborz in Fe-C alloys is controlled by tile rate of carbon difirsion from the interface. The dissolution of carbon in molten Fe-C alloys has been the subject of a number of investigations. Most of these investigations have been inconclusive because of poorly defined experimental variables. Two of the more sophisticated studies are summarized below. Dahlke and Knacke' studied the phenomenon by, in part, immersing graphite rods into 0.5 pct carbon-steel for different lengths of time. Since the experiments were conducted in air or in CO atmospheres, the melt was strongly agitated by gas evolution. It was concluded that the change in bath composition as a function of immersion time was in agreement with the assumption that the dissolution process was transport-controlled. The hydrodynamic conditions in these experiments, however, were not well-defined and gave no indication of the nature of the dissolution process at higher fluid velocities. In a recent study Shurygin and ruk investigated the dissolution of carbon in molten Fe-C, Fe-Si, Fe-P, and Fe-Ni alloys. Small graphite disks were rotated in a crucible containing molten alloys under such conditions that only the lower face of the disk was exposed to the melt. The results of this investigation indicate that, over the range of velocities (100 to 1000 rpm) and bulk liquid concentrations (0.7 to 4.5 wt pct C) considered, the dissolution of carbon in the iron alloys is limited by the diffusion of carbon from the interface to the bulk liquid (a transport mechanism). For the particular geometry used by these authors, exact analytical solutions of hydrodynamic and diffusion problems are aailable. Hence the experimental results obtained by Shurygin and Kryuk permit the evaluation of diffusion coefficients of carbon in the four systems investigated. In the present investigation a series of experiments were conducted in which the rate of dissolution of carbon in Fe-C alloys was measured under conditions which permitted wide variation of the fluid velocity and the carbon concentration of the bulk liquid. Graphite cylinders were rotated at different speeds in a stationary concentric crucible containing various molten Fe-C alloys. THEORETICAL DEVELOPMENT In general, the resistance to mass transfer from a solid interface to a turbulent liquid is assumed to reside in a laminar boundary layer adjacent to the interface. If it is also assumed that the diffusion coefficient is independent of concentration, the steady-state rate of dissolution for the case of arbitrary liquid and solid densities can be obtained from the integration of the equations of continuity. The derivation is similar to that used by Lommel and chalmers4 for the case of pl = ps. The solution, expressed in terms where N = rate of diffusion of the solute from the interface. Exact analytical solutions of the hydrodynamic equation for the boundary layer thickness are available for only a limited number of geometries. Consequently, a mass-transfer coefficient, k, is usually

Jan 1, 1967

By W. G. Bearden, P. P. Scott, G. C. Howard

This paper concerns the rupture or breakdown of rock formations as related to drilling, completing, and stimulating production of wells, and comprises data compiled from a study of literature and records of treatment of oil and gas wells. and from tests conducted in bores drilled into rock cores and outcrops of rock. Results of the investigation indicate that the internal pressure to rupture cylinders of rock and to breakdown rock formations surrounding a bore in the earth is dependent upon the extent of intrusion of fluids. the position of bedding planes. the ratio of internal to external diameter, the tensile strength of rock, and magnitude of confining pressure, and is independent of the size of bore, degree of fluid saturation. and temperature of rock within practical limits. It is concluded that the mathematical relationship of pressure in bores and stresses in the surrounding rock must not be limited by the simplifying assumptions of homogeneity. isotropy, and impermeability; that the incidence of lost circulation of drilling fluids to induced fractures may be reduced by preventing intrusion of fluids into the small intrinsic fractures along weak bedding planes; and that the magnitude of the breakdown pressure of wells to be treated may be lowered by removal of mud cake. INTRODUCTION The purpose of this paper is to present and discuss the results of tests which may serve to broaden the understanding of the phenomena of rupture or breakdown of rock and thus contribute to the improvement of the techniques for drilling and completing wells. including such operations as preventing lost circulation, stimulating production, and placing cement. Since the early recognition of the possibility of rupturing rock adjacent to a well by fluid pressure, the distribution and magnitude of stresses around a well and the internal pressure to cause failure have been expressed mathematically by application of the principles defining the elastic and inelastic behavior of thick-walled cylinders of a homogeneous. isotropic, impermeable material. In either the elastic or plastic state, if the conditions of homogeneity. isotropy, and impermeability were the normal characteristics of rock. there would be no reason to question the validity of the above principles when applied to rock. However. since most rock formations are characteristically permeable to some degree, contain bedding planes and small intrinsic fractures. and are heterogeneous, rendering invalid the assumptions of homogeneity, isotropy, and impermeability, the application of the thick-walled cylinder theories to the behavior of rock formations penetrated by a bore appears illogical. Also the failure to consider the effect of the properties of the drilling fluids, which certainly intrude in various degrees into most rock formations. is further cause for questioning the application of these principles. Even in the case of cylinders of hardened chrome-nickel steel, which would he considered relatively homogeneous isotropic. and impermeable, as compared to rock, it has been observed that the internal pressure capable of being withstood by the cylinders varied with the sizes of molecules comprising the rupturing fluid used. Because of these apparent weaknesses in the theories of the behavior of thick-walled cylinders when applied to bores in rock, and the importance of knowing the true behavior of rock under the influence of fluid pressure when planning drilling and completing procedures for wells, tests were undertaken to determine by observation the actual rupturing pressure of cylinders of rock and the effects of such variables as environmental conditions and characteristics of rock formations, fluid properties, and bore dimensions. It was intended that by these tests the validity of the thick-walled cylinder theories when applied to rock would be determined and, if found invalid, mathematical expressions would be derived for predicting stress and rupturing pressure of rock formations under various conditions. Since the derivation of mathematical expressions has been only partially completed, all of the results of the latter phase are not included in this paper. PROCEDURE The investigation was initialed with a study of the theories pertaining to the rupturing of thick-walled cylinders of homogeneous. isotropic, impermeable material and a study of the

Jan 1, 1953

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Jan 1, 1881