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By Laurance Reid

HIGH compression ratios, resulting from high injection pressures and relatively low recovery process pressures, constitute a major problem, which has confronted those engaged in gas recycling for condensate production since the beginning of that practice. Despite the numerous process developments and improvements, no entirely satisfactory solution for this prob-lem has been presented to date. Often, where the residue gas from the recovery process must be recompressed for subsurface injection, there is a substantial difference between the required injection pressure and the plant-operating pressure required to produce maximum recovery of condensate. These limitations result in high compression ratios, which, in turn, neces-sitate excessive compressor investment and operating cost. As an alternative, the operating pressure may be increased in order to lessen the compressor requirements but such a saving often is purchased at the expense of decreased condensate recovery, caused by operation at the higher pressure. Regardless of the choice, the net result is a diminished return on the capital invested in the project. The goal of future development in this field must be the complete recovery of all valuable hydrocarbon components in the reservoir fluid at pressures that, regarded as compressor suction pressure, will require minimum compressor horsepower to inject the residue gas into the formation. A com-pression ratio of 1.5 has been established as an optimum for modern compressor equipment." Therefore, in order to con-form to this optimum condition, a 3000-lb. injection pressure would require that the condensate recovery process be operated at 2000 lb. per sq. inch.

Jan 1, 1940

By R. D. Lama

Coal mining is one of the major sources of methane release to the atmosphere by human industrial activities and is believed to contribute to -30% of the total methane emissions from industrial activities. In 1993, world saleable black coal production, attained almost 3.5 billion tonnes from which around 65% was produced underground. Coal in underground mines can contain high quantities of methane and some deep coal seams have methane content as high as 50 cubic meters per tonne of coal. Gas is re- leased during coal mining from the mined seam and in a higher degree from the neighboring unmined seams and gas bearing strata which are fractured as mining advances. This paper de- scribes a study which was undertaken to estimate the extent of methane emissions from coal mining in the world. Measured emission related data were collected from most underground coal producing countries in the world. The data included methane flows in the ventilation system, methane flows in gas drainage system, in-situ gas content, methane utilization and coal production. More comprehensive data were collected from a range of gassy and non-gassy Australian mines. Residual gas content of samples from run of mine were also measured. Using the Australian data, mathematical expressions were established to evaluate methane emissions as a function of coal production and in-situ gas content for other mines. These emission models were then used to evaluate the emissions for the countries or coal basins without measured emission data. Trends in methane emissions from underground mining for the year 2000 and beyond were also estimated.

Jan 1, 1997

By James Norman

SPODUMENE is a lithium-bearing pyroxene, and is an important source of lithium compounds. Because of its high alumina and lithia content, it might be a desirable constituent of glass batches. The use of spodu-mene in ceramics will undoubtedly increase, as it has been shown that a mixture of the proper proportions of this mineral with soda feldspar and potash feldspar has a much lower maturing temperature upon firing than has any one of the three components.1 The mineral spodumene seldom occurs as pure mineral, but ordinarily with feldspars, mica and quartz. All spodumene-bearing rocks tested contained these minerals as gangue. Small amounts of iron and manga-nese oxides also were present, usually as stains on the silicate grains. Mica associated with the spodumene carried a considerable amount of lithia. This was discovered in flotation tailings, which, although virtually free of spodumene grains when examined microscopically, showed 0.4 to 0.5 per cent Li2O on chemical analysis. The lithia content of micas picked from the North Carolina spodumene rock was variable. Some samples contained little lithia, others more than 3 per cent. In 1938, under the supervision of Oliver C. Ralston, ? the Bureau of Mines, in cooperation with the Tennessee Mineral Products Corporation, undertook to study the beneficiation of North Carolina spodumene by froth flotation. The Bureau had previously published investigations on the beneficiation of spodumene.2,3 The methods described in the second publication' did not give good results with badly weathered spodumene rock, so that more thorough investigation of the subject was warranted.

Jan 1, 1940

By R. P. Carreker

GERMANIUM is a member of that group of ele-nents—carbon, silicon, germanium, and tin-— that are currently of particular interest because of their interesting electrical properties. Near room temperature these materials of diamond cubic crystal structure are characteristically brittle. However, there have been several recent reports that germanium is not brittle at elevated temperatures These observations may be summarized as follows: 1—Germanium single crystals were observed to creep in bending under a maximum fiber stress of 6 kg per mm&apos; (8500 psi) at 500°C and above.&apos; The creep curves were sigmoidal, with an induction period that decreased with increasing temperature. 2—Germanium crystal bars have been bent 90" about radii ten times the bar thickness at 550°C.&apos; 3—-Audible clicks were heard when l/4 in. thick crystals were bent drastically at 450" to 500°C. No microstructural evidence of mechanical twinning was observed 4—Slip lines have been observed in tensile specimens deformed at 600°C, and are coincident with (111) planes, the close-packed planes of the diamond cubic structure.] The slip direction has not been established. 5—A germanium crystal has been compressed approximately 20 pct along a <110> axis at 700°C." The results reported subsequently were obtained in exploratory experiments intended to indicate some aspects of the behavior of germanium single crystals when tested in simple tension. Specimen Preparation A single crystal bar of n-type germanium was used. It was of purity corresponding to a resistance range of 2 to 20 ohm-cm. Tensile specimens were prepared by cutting small rectangular bars

Jan 1, 1957

1. Healthy and active Local Section organizations are vital factors in promoting the vigor and growth of the Institute. 2. Activity on the part of Local Sections should be recognized and stimulated by appropriation of funds from the Institute&apos;s treasury; and these appropriations should be as large as is consistent with the relative needs for other activities. 3. As between different Sections, the amount of such appropriations should be based primarily on the extent of activities as reflected in the number and character of meetings held and " the attendance of the members at such meetings. 4. In making a request for funds for any year, the officers of a Local Section should submit a report on the printed form approved by the Directors at their meeting on November 19, 1937. 5. A standing Committee on Local Section Appropriations, consisting of one past chairman of a Local Section, one member of the Institute&apos;s Executive Committee, and one member of the Finance Committee, shall be appointed by the President and shall pass upon requests for appropriations and authorize payments within bounds of the budget. The committee will be guided by the principles herein outlined, always having in mind the vital importance of healthy, active Sections to the welfare of the Institute as a whole. 6. According to Article XI, Section 2 of the Bylaws, requests for appropriations shall be signed by the Chairman, Secretary and Treasurer of the Section. 7. Requests for appropriations must be in the hands of the Secretary of the Institute by February 15 of the year for which they are desired.

Jan 1, 1940

By Valentine Garfias

THE various phases of the Mexican oil industry have received so much publicity that there is little to add to the discussion of present and future production, extent and importance of prospective fields, and status of petroleum legislation, to mention but a few of the angles of the Mexican oil problem. However, out of this wealth of information, which is generally of contradictory nature, the average petroleum man is at a loss to know something definite regarding the various questions involved so, keeping the foregoing in mind, it has been the writer&apos;s aim to record in a concise form the most reliable and up-to-date information regarding the salient features of the Mexican oil situation. PRESENT STATUS OF MEXICAN OIL INDUSTRY Production During 1921 The Mexican oil fields, during 1921, produced in round numbers 203,000,000 bbl. of which 176,000,000 bbl., or 86 per cent., were exported, the bulk of -these exports, or about 73.3 per cent., going to the United States. The Mexican exports were divided by grades as follows: Light crude, 47.0 per cent.; heavy crude, 22.0 per cent.; tops, 3.5 per cent.; fuel oil from light crude, 24.0 per cent. The balance, or 3 1/2 per cent., includes the bunker fuel shipments and the coastwise trade in Mexico, which is not classified as to grades. The figures show that, in importance, the light-oil fields from about 755 per cent. of the Mexican petroleum industry.

Jan 4, 1922

By Charles F. Herbert

Placer mining in Alaska had a desultory inception at Sumdum in 1869 and, during the years 1880 to 1896, received thin nourishment from the readily exhausted gold placers at Juneau and the longer- lived deposits in the Circle, Fortymile, and Rampart Districts. Finally, in 1897, the great Klondike discovery in Canada&apos;s Yukon Territory brought thousands of gold seekers to the Far North. These men, in successive, far-reaching gold rushes, found the large, rich gold deposits at Nome, Fairbanks, and Iditarod, as well as many smaller placers. The hectic rushes during the years from 1898 to 19 10 were comprised of hundreds, sometimes thousands, of "stampeders," as they were called. Since very many Alaskan creeks, from the crest of the Brooks Range in the north to the Pacific Ocean in the south, carry at least a few flakes of gold, there was ample seed to start a new stampede. Of the 100s of reported "strikes," nearly 50 became more or less important placer mining districts; by 1910 they had produced about 184.2 fine Mg (6.5 million fine oz) of gold; the all- time peak production year was 1906. A few of the miners and prospectors prospered, but the total value of all gold produced failed, by a wide margin, to cover the aggregate costs incurred by them in the undeveloped Territory of Alaska. On the other hand, the traders with their readily salable supplies of food, tools, and hardware and the freighters with their teams of dogs or horses and boats of all kinds profited throughout the era of stampede.

Jan 1, 1991

THE following employment items are made available to AIME members on a nonprofit basis by the Engineering Societies Personnel Service, Inc , operating in cooperation with the Four Founder Societies Local offices of the Personnel Service are at 8 W 40th St , New York 18, 100 Farnsworth Ave, Detroit, 57 Post St , San Francisco, 84 E Randolph St , Chicago 1 Applicants should address all mail to the proper key numbers in care of the New York office and include 6c in stomps for forwarding and returning application The applicant agrees, if placed in a position by means of the Service, to pay the placement fee listed by the Service AIME members may secure a weekly bulletin of positions available for $3 50 a quarter, $12 a year MEN AVAILABLE Executive Engineer, 37, married, 3 children Now Resident Manager nonmetallic underground mine and processing plant Management and operational experience in gold, copper, zinc, limestone and lime products manufacture Mine plant design and construction, underground mines and quarries Excellent references Currently employed but available reasonable notice Prefer U S M-687-426-E-5-San Francisco Metallurgical Engineer, 29, married, one child, B S Metallurgical Engineering Five years&apos; practical experience in milling and laboratory research Available thirty days Prefer West or Southwest U S A M-689¬522-E-1-San Francisco Experienced Mining Engineer, university graduate, 40, married Twenty years&apos; experience all phases metal mining, past 13 years as manager, excellent cost and safety record Available short notice Best references and complete professional record available upon request M-690

Jan 1, 1952

A group of prominent engineers and contractors of Chicago and vicinity have cooperated in forming a Joint Committee on Military Engineering. The founders are members of all of the leading engineering and contracting organizations of Chicago, including the local branches of the national engineering societies. The purposes of the Committee are to further military preparedness among engineers, contractors and their associates by the following means: (1) Courses of lectures; (2) assigned reading; (3) studies and practical instruction in military engineering;. (4) assisting engineers to qualify as officers in the National Reserve Corps of Civilian Engineers; (5) urging enlistment in and support for engineer troops of the National Guard and such other organizations as the Government may create; (6) furthering instruction in military engineering in training camps and the attendance in them of those qualified; (7) by such other means as from time to time may be deemed advisable. The Joint Committee has already prepared a program covering the vital points outlined. To date the program is practically complete for a period extending from April 20 to July 25. Something of interest will be taken up each week, including lectures by Lieutenant-Colonel W. B. Judson, Engineer Corps, U. S. Army; two lectures by Major P. S. Bond, Engineer Corps, U. S. Army; Lieutenant-Colonel Mason M. Patrick, Engineer Corps, U. S. Army, and several exhibition drills, terrain exercises and inspection trips under the direction and guidance of various officers of the Engineer Troops of the Illinois National Guard. Additions to the program will be made from time to time.

Jan 5, 1916

By F. A. Hill

Coal mining in the State of Washington offers many interesting problems for the mining engineer, due to the varied physical conditions occurring in different fields, and often in the same mine. The different coal seams worked in the same mine commonly require different mining and transportation methods for economical operation. The coal measures have inclinations ranging from 5&apos; to vertical, and in the same mine the dip of the coal may vary from 30&apos; to 50 . In all fields, the seams are extensively faulted, folded, and sheared. The quality of the coal produced ranges from brown lignite to bituminous coking coal, the following being typical analyses: Very little of the coal contains as much as 0.75 per cent. sulfur. The brown lignites occur mostly in Lewis and Thurston Counties, and as a rule are very cheaply mined. This coal has been successfully used in locomotives of the Oregon & Washington Railroad, after equipping them with specially designed fireboxes. The sub-bituminous coals occur in all the coal-mining counties. Their cost of production varies widely, according to the character of the formations, the pitch, and the wall conditions. This makes a fairly good steam coal, but the lump is used mostly for domestic trade, after grading into lump, nut, and pea. The coking coal is used for making coke, and for locomotive and other boiler fuel. It yields a strong metallurgical coke, quite high in ash, though seldom exceeding 18 per cent. ash. Most of it is susceptible to

Jan 1, 1920

Soil Testing for Engineers. By T. W. Lambe. Published by John Wiley & Sons. 165 P. $5.00.-Filling a need for a text for the teaching of soil testing in the laboratory, this book is also of value as a reference for practicing engineers and for personnel in soil laboratories. Following an introductory chapter on general laboratory procedures are chapters devoted to the individual laboratory soil tests which are commonly employed. Apparatus, supplies, recommended procedures, discussion of procedure, calculations results, and numerical examples are provided for each test. Brief derivations of formulas and explanations and discussions of calibration procedures and special techniques are given in the appendix. Mesabi Pioneer. Copyrighted 1951 by the Minnesota Historical Society.- Publication of this book has been made possible by a generous gift to Society from the E. J. Longyear Co. of Minneapolis. This book covers the evolution of the Mesabi Range from a wilderness into the nation&apos;s greatest iron producing area. In this book is found the first hand experiences of Edmund J. Longyear who saw the development of the range from its beginnings, and who himself took a notable part in it. In 1890 Edmund J. Longyear sank the first diamond drill hole on the Mesabi. During the next two decades he sank pits and holes- 7133 of them-throughout the length and breadth of the Mesabi Range, exploring for iron ore. He saw roads and railroads built. He watched the range communities--Hibbing, Chisholm, Biwabik, Mountain Iron and the others change from exploration camps to

Jan 11, 1951

By W. A. Oates, J. S. Blakemore, E. O. Hall

AS part of an investigation into the effect of hydrogen on the serrated yielding of Ni-Cu alloys,&apos; it was necessary to determine the solubility of hydrogen in the alloys of interest. With the exception of the work by Fukusima and Mitui2 who investigated the solubility of hydrogen in solid Ni-Cu alloys at 20 wt pct intervals at 1050°, 700°, and 350°C, the information in the literature is limited.3-10 Alloys were prepared from deoxidized Analar Copper and Mond Nickel pellets.&apos; Wire samples were hydrogenated at 7.8 atm in an autoclave consisting of 5 ft of thick-walled Inconel 600 tube with a resistance furnace around the middle portion. The top end, at room temperature, was fitted with a safety valve, a calibrated pressure gage, and a sample inlet, while the bottom end, again at room temperature, was filled with water. After reaching equilibrium samples were quenched by dropping from the high-temperature region of the autoclave into water. They were then quickly transferred to liquid nitrogen where they were stored until analyzed for hydrogen using an Exhalograph.11 The results, which are shown in Fig. 1, represent the mean of two separate determinations on each sample. Because of the lower level of hydrogen at the high copper end of the series, the results here are of poor precision using this method. Fortunately, the results of Himmler9 using the Sieverts technique are available for these copper-rich alloys (>80 at. pct Cu)

Jan 1, 1969

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) No. 504.-Member, technical graduate, draft exempt, who has been employed as research chemist in cyanidation and flotation for past 5 years, desires position with large company as metallurgist or assistant mill superintendent. Especially experienced in flotation of gold and silver ores, but am also familiar with flotation of lead-zinc ores. Foreign service not desired. Will be at liberty after Dec. 1, 1918. No. 505.-Member, graduate mining engineer, with 8 years&apos; practical experience, including experience as superintendent. Desires position as engineer, foreman or superintendent of mine. No. 509.-Petroleum geologist and engineer, member, now engaged in consulting work, with five years&apos; experience in Mid-Continent and Eastern fields, desires position with responsible concern either in South or South American countries. No. 510.- Chemical engineer, member, technical graduate, at present officer in Chemical Warfare Service of the United States Army, desires position in the East. Several-years&apos; experience in design, construction, and operation of chemical and metallurgical plants. Minimum salary, $200. Available Jan. 1, 1919. No. 511.-Mining engineer, 32 years old, single, desires position. Speaks Spanish and French. Recently manager of large copper mines. Experience in steam shovel and underground mining. No. 512.-Mining engineer, technical graduate, member, 32 years old, single, 10 years&apos; experience in United States, Mexico and Central America in mining, prospecting, milling, chemical research and business experience. Speaks Spanish. Open for engagement as superintendent or assistant. Can give references as to ability and integrity.

Jan 1, 1919

By I. Iwasaki

In the flotation of iron ores and nonmetallic ores desliming is the key to a successful operation; the technology of flotation of well-deslimed ores has become fairly well established. When finely disseminated ores are ground to liberation, however, conventional desliming of the fully dispersed pulp results in an excessive loss of valuable constituents. Selective flocculation of iron oxides followed by removal of dispersed siliceous slimes is a new development and is one of the most promising approaches to the treatment of finely disseminated, oxidized iron ores, available in vast quantities both here and abroad (1,2,3). To apply selective flocculation to the variety of refractory iron ores or to cope with the fluctuations in an individual ore and the make-up water, the factors governing this technique must be clearly formulated. For the removal of siliceous and clayey slimes from oxidized iron ores by selective flocculation, the optimum conditions are extremely sensitive to the mineralogical characteristics of the ore, the type and the amount of soluble salts in pulp solutions, and the mesh-of-grind. Certain starches appear to function better than others (4, 5). Selection of the proper reagents and their judicious use is important not only for their efficient utilization but also for minimizing the adverse effects they might exert on the flocculation and flotation steps, and the pollution the effluents might cause when discharged, either intentionally or accidentally, into lakes and streams. In the present article some of the major factors that influence the selective flocculation of iron ores are summarized.

Jan 1, 1979

By Alp Gokalp

The aim of this article is to present an application of jet grouting technique in stiff clays for foundations of the natural gas combined cycle power plant, under construction in Aliaga, Turkey. The plant site is in the Aegean coastal region and 60 km north of Izmir. The foundation soil is composed of quaternary alluviums on top and tuff base rock. The thickness of the alluvium varies between 16 m to 30 m. Groundwater was observed 2.5 m below the ground level. At the design stage, settlement analyses were carried out for the various buildings and facilities in the power plant. Based on the analyses, it was predicted that total and differential settlements are not tolerable, thus jet grouting is implemented as a ground improvement under the majority of the foundations of the power plant. This paper also describes the selection of jet grouting technique, application type and details of the process parameters such as injection pressure, number and size of nozzles, lifting and rotation speeds. Prior to the commencement of the jet grouting works, a number of preliminary parameter tests and preliminary pull-out tests were carried out throughout the site in order to define and verify the jet grouting process parameters to achieve the required diameter of 600 mm and minimum jet grout strength of 3.2 MPa. Moreover as part of the comprehensive quality control and quality assurance program pursued in the project, a number of tests; such as continuous coring, integrity testing, installation of confirmatory jet grout columns, were carried out during the production of jet grout columns.

Jan 1, 2002

WHEN Magma Copper Company in 1952 set about finding $100,000,000 to finance the project of developing and equipping the property of its lusty progeny, the San Manuel Copper Corporation, A. J. McNab, president and guiding genius for both companies (and incidentally a mining engineer by profession), determined that he would avoid the mistake frequently made in such circumstances, of underestimating the cost, and thereby running short of funds before the job was completed. The fear that this might happen was one of the reasons why insurance companies, one potent source of "big" money, were reluctant to finance the enterprise. How, they asked themselves, would Magma, a relatively small company, get additional money in such a contingency? Insurance officials&apos; thumbs were turned down. Conditions Imposed by R.F.C. The upshot was the negotiation by Mr. McNab for San Manuel of a contract with the Reconstruction Finance Corporation, dated July 10, 1952, whereby needed monies in amount up to $94,000,000 would be advanced as a loan, bearing 5 per cent interest. Arrangements were made for the separate financing of the new $10,000,000 town, needed for the project, through the Del E. Webb Construction Company of Phoenix, Arizona, and M.O.W. Homes, Incorporated, of Los Angeles. Thus the $94,000,000 drawing account was believed ample to provide for building the railroad, the mine plant, the concentrator, and the smelter, as well as for the underground development of the mine needed to start production. As a matter of fact, only

Jan 1, 1957

By K. L. Rubow

"Diesel exhaust and mineral dust concentrations have been measured for aerosols generated in the laboratory and as found in five underground coal mines- 3 utiliting diesel-powered hallage equipment and two electric-powered equipment. Two source apportionment techniques have been applied to differentiate between the mineral dust and diesel exhaust aerosol concentrations. The first technique, using a microbrifke uniform deposit impactor CMOUDI) for size selective sampling, is based on modeling aerosol size and the premise that the diesel exhaust portion of .the aerosol is predom1nately submicrometer and the mineral dust portion is mostly greater that one micrometer in size. The second technique, Chemical Mass Balance CCMB) modeling, was used to referee the analysis of diesel exhaust and mineral dust aerosol concentrations from the size selective sampling results. ,The MOUDI size distribution data were modeled to obtain parameters describing the fine and course fractions of the sampled aerosol and to estimate the contributions to each mode from both mineral ·dust and diesel exhaust aerosol sources. The results showed the size distribution of the mixed aerosols exhibited two definite modes with the minimum between the modes occurring at 0.8 um. For the diesel equipped mines, this analysts yielded an average value for the fraction of the fine aerosol attributable to mineral dust of 1 pct. Less than 5 pct of the coal mine diesel aerosol was found in the coarse size fraction. CMB analysis confirms the original premise for using aerosol size to separate diesel exhaust and mineral dust aerosol during sampling."

Jan 1, 1988

By K. Twite, K. Mujinga, J-M. Dereydt, P. Louis

"GECAMINES is a large mining concern and the world's leading cobalt producer having some of the richest cobalt deposits in the world. Cobalt is associated in the ore with copper as sulphides and oxides and in some locations with nickel too. Specific hydrometallurgical processes have been developed by GECAMINES which had done an important contribution to the development of the cobalt hydrometallurgy.In the Shituru plant, cobalt is obtained from an unique in-pulp electrolysis process, while in Lullu, cobalt is electrolyzed in a clear acidic solution giving a purer deposit. In the beginning of 1996 Shituru started the treatment of mixed Cu-Co-Ni Shinkolobwe hydrates obtained as by-product of an uranium solvent extraction plant. A typical analysis of this feedstock is: 2% Cu, 8% Co and 4% Ni.The nickel sulfide depolarized cementation process developed previously by GECAMINES was inefficient to treat such a high level of nickel contamination and it was decided to produce alloyed Cobalt-Nickel cathodes in the Shituru tankhouse.As anticipated from laboratory tests as previous studies and publications, a lower Ni/Co in the deposit was obtained compared to the Ni/Co ratio solution, despite the nickel reversible electrochemical potential is somewhat higher than the one of cobalt (-0.25 V vs -0.28 V).In this paper, the process flow-sheet and production data are given. Cobalt alloy with 5 - 20 % Ni was obtained at a production level of 300 t per month. The process developed is a new contribution to cobalt hydrometallurgy."

Jan 1, 1997

By K. Rubow, Z. Zhlqun, V. Marple

A theoretical technique has been developed and verified experimentally for determining the aerodynamic diameter of irregular shaped particles. The aerodynamic diameter of a particle is a very important property in determining where that particle deposits in the respiratory tract. Many instruments, such as impactors and cyclones, will determine the aerodynamic size distributions of aerosol particles but few analyze the particles individually. The theoretical approach of our technique is to solve, by use of high speed computers, the three dimensional Navier-Stokes equations to obtain the flow field around an irregular shaped particle of any contour. The computer program will then determine the drag on the particle, and thus the aerodynamic diameter of the particle can be calculated. The experimental approach has been to pass the particles through a centrifuge and collect the particles upon a collection foil. The position of a particle on the foil is an indication of its aerodynamic diameter. These particles were then shadowed in two orthogonal directions and inspected under an SEM. The top view of the particle in the SEM plus the views of the two orthogonal shadows allows one to determine the three dimensional shape of the particle. Studies have been performed on silica, coal and talc particles with aerodynamic diameters in the 1 to 4 um size range. The three dimensional shape, as is determined from SEM analysis was used in the theoretical computer program and the results compared. It was found that in most 'cases the agreement between the experimentally and theoretically determined aerodynamic diameters was within 5%.

Jan 1, 1988

By C X. Zhang, W K. Ru, S C. Hu

To study the creep properties and the energy evolution characteristics of the weakly cemented rock (WCR) in western China, the creep deformation damage law of weakly cemented mudstone (WCM) under graded loading and the energy evolution characteristics of each creep stage were analysed based on the triaxial graded loading creep test of WCR. The results showed that as the confining pressure increased, the creep failure strength of the WCM increased from 9.5 to 24.8 MPa, and the relative displacement of the mineral particles in the mudstone increased gradually, resulting in a reduction in the fracture angle from 79.7° to 58.3°. At the same stress level, the strain energy Ue, the total energy U, and the dissipation energy Ud all increased as the confining pressure increased, but the growth rates of U and Ud decreased gradually, while the growth rate of Ue remained high. At the end of the stable creep stage, Ue increased slowly with the confining pressure, while U and Ud increased rapidly with the confining pressure, and their growth rates were basically the same. At the end of the accelerated creep stage, the growth trends of these three energies were all positively correlated with the confining pressure, Ue was significantly lower than that at the end of the stable creep stage, and Ud and U were further increased. These results revealed the unique creep properties and energy evolution characteristics of the WCR, providing a theoretical basis for long-term stability control of roadways that are built with WCR.

Nov 29, 2022