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By Li Keqiang

Among the pile foundations of the 156 tall buildings over 18 storeys in Shenzhen, 86. 5% of them are constructed by slurry drilled piles, bored piles and excavated piles (hand-dug caissons). Based on the experiences of the engineering practices, the paper points out that the main quality problems of pile foundations in Shenzhen are: insufficient bearing capacity of single pile; poor concrete quality of pile; damage of the precast pile; pile tip not reaching the required bearing stratum and the thickness of bored/drilled sediment exceeding the specified. etc. The quality inspection methods that have been used include: check of construction records and excavating; static loading test; core sampling test; non-destructive test, etc. Treatments of quality problems used in Shenzhen are also introduced in this paper.

Jan 1, 1991

By S. Ndlovu, M. Malatse

"The Witwatersrand Basin is the heart of South Africa’a gold mining industry. The cluster of gold mines located in the Witwatersrand Basin generates a significant amount of mine tailings, which have adverse effects on the environment and ecological systems. In addition, disposal costs are very high. The exponential population growth in the Witwatersrand area has resulted in pressure on the reserves of traditional building materials. Quarrying for natural construction material is very expensive and damages the landscape. This work therefore examines the use of gold mine tailings in the production of bricks.Different mixing ratios of gold tailings, cement, and water were used. The resulting bricks were then cured in three different environments - sun dried, oven dried at 360°C, and cured in water for 24 hours. The bricks were then tested for unconfined compressive strength, water absorption, and weight loss. The results showed that the mixture with more cement than tailings had a compressive strength of approximately 530 kN/m2. It was also found that the best brick curing system was in a water environment. Bricks made from tailings cost more than conventional bricks because of the higher quantity of cement used, but the manufacturing process consumes less water. Overall, the results indicated that gold mine tailings have a high potential to substitute for the natural materials currently used in brickmaking.Paper written on project work carried out in partial fulfilment of BSc. Eng. (Metallurgyand Materials Sciences)"

Jan 1, 2015

By Gray Mullins

This paper presents experimental results from a study to assess the interface bond between a cast-in-place concrete seal slab and prestressed concrete piles in cofferdams. Three different seal slab placement conditions - fresh water, salt water and bentonite slurry - were evaluated and the results compared against controls where no fluid had to be displaced by the concrete. Normal pile surfaces were investigated. Additionally, the situation of ?soil caked? piles was also investigated. Both model and full-scale tests were conducted. In the model tests, twenty eight 15 cm square prestressed sections were used with the embedment depth varied between d-2d, where d is the width of the pile. In the full-scale tests, 16 specimens were tested. The prestressed piles were 36 cm square with the embedment varied between 0.5d-2d. Four of the sixteen piles were cast with embedded gages located at the top, middle and bottom of the interface region. The results showed that loads were transferred to the piles over an effective area, not the entire embedded depth. Significant bond stresses developed even for the worst placement condition. Recommendations are made for revising current values in specifications.

Jan 1, 2013

By Dennis Nottingham

Spin-fin pipe piles can develop large loads in tension, thus have evolved as a foundation product of great potential. Currently, over 500 spin-fin piles have been used successfully in dolphins, docks, buildings and bulkheads. Spin-fin piles are pipe piles with plates welded near the tip at a batter-in-screw fashion. Thus, as the pile is driven, the pile screws into position. Tests show this pile type to have highly unusual stress/strain relationships, wherein plunging failure is usually never reached either at normal or large deformations. Tension capacity can approach pile capacity in bearing; thus, large reserves are usually available for tension. Tests have been performed on 8-5/8-inch to 24-inch-diameter piles in silt, sand, and gravelly soil, to provide a broad spectrum of data.

Jan 1, 1990

By A. Noble

The design of separation circuits can be a complex, labor-intensive and costly process. While the engineer?s experience along with extensive data sets and simulation are crucial tools for determining the final solution, a more fundamental approach is suitable to compare preliminary options and reduce the number of potential alternatives. In light of this need, the authors have developed the Circuit Analysis Reduction Tool (CART?). This software package relies on the fundamental principles of linear circuit analysis; however, the solution methodology has been streamlined to automatically incorporate stream splitting and unique separation performance for each unit. The resulting tool allows preliminary analysis of circuit designs without the need of detailed feed characterization. In addition to the basic analytical approach, this paper supports the veracity of the methodology with several simulated examples for various separation models.

Feb 27, 2013

By J. R. Piper

“Old Borate,” located in the Calico Mountains east of Barstow, California, lead domestic colemanite production from 1884 through 1907. Mineral exploration at “Old Borate” in the early 1980's, examined borate mineralization in Tertiary lacustrine strata. Surface sample and drill hole locations, geology and structure, were hand-drafted on paper maps. To re-evaluate this data, the information was digitized using Geographic Information Systems software. Digital Elevation Model based terrain modeling integrated surficial samples with drill hole data to locate favorable drilling targets. Structural relationships were used to identify hypothetical resources formed by the leaching of boron from surface exposures, redeposited at depth.

Jan 1, 2001

By Rodrigo Jerez

Advances in inexpensive computer automation led to the development and use of a computerized ore control system at the Cyprus Copperstone Gold Mine near Parker, AZ. These new ore control practices improved accuracy, performance and productivity of the ore control effort. An automated system for data collection, including bar coding of blasthole samples, laboratory analysis, data management, grade estimation, cut delineation and ore zone stake out, plays a major role in ore control practices. This is of particular interest because of the large amount of blasthole information being processed, analyzed and reported daily. Copperstone Gold management has been progressive toward new, efficient methods regarding ore reserve estimation, long-term mine planning, short-term mine planning, ore control and surveying. Technological advances, including powerful personal computers, applicable mine planning software and surveying instrumentation, have become readily available and affordable. The computerized ore control procedures used at Copperstone include sample data collection, laboratory automation and computerized data management. These have reduced the time to complete ore control on a blast pattern by 50% to 75%. The final product - ore control - is generated in a more timely and accurate manner.

Jan 1, 1991

By Michael McVay

The use of augered cast-in-place piles has seen tremendous growth under commerical structures in the past twenty years. Problems with vibration, soil densification and/or heave associated with driven piles do not occur with properly installed augered piles. Augered cast-in-place piles were originally constructed (1950s) with diameters of .31 m (12 in.) and lengths up to 6.1 m (20 ft); however with the advent of better drilling equipment, diameters varying from .41m(16 in.)to .61 m (24 in.) and typical depths ranging from 18.3 m (60 ft) to 24.4 m (80 ft) are achievable. Reinforcement may vary from a single high strength rebar (Grade 60) at the top of the pile to a continuous steel cage depending on loading (compression, tension-uplift, and lateral). Typical axial design loads (compression) for a single augered cast-in-place pile are in the 445 kN (50 tons) to 890 kN (100 tons) range.

Jan 1, 1997

By Geoffrey Fosbrook, Donald Phillips, Anil Parikh

The Second Avenue Subway is a $16.8 billion project planned by the Metropolitan Transportation Authority (MTA) in New York City. It will reduce overcrowding and delays on the Lexington Avenue Line, improving travel for both city and suburban commuters, and improving access to mass transit for residents of the East Side of Manhattan. The project is a new, two-track, 13.5 km (8.5 mile) subway extending from Lexington Avenue at 125th Street in Harlem on the north end of Manhattan, to Water Street at Hanover Square in Lower Manhattan. The first phase of construction includes rock tunnels from 92nd Street to 62nd Street and connection to the existing 63rd Street station, three new stations, and track and systems from 105th Street to 63rd Street, allowing service between 96th Street and Brooklyn via an existing Broadway Line. The following describes the Project in detail, discusses the construction challenges addressed in the design, and the initial design/build contract to be awarded in 2005. A discussion of the planned mined construction of two rock caverns and a cut-and-cover station construction are also included.

Jan 1, 2005

By Richard K. Sandaas

Start Date: April 4, 1988 Completion Date: Dec. 29, 1989 Contractor: SCI Contractors Past and present transportation centers will come together at International District Station, located at the south entrance to the tunnel next to the turn-of-the-century Union Station train depot. The area will bustle once again with activity as commuters and visitors converge on the modern transit station at the edge of Seattle's International District. Buses coming from south Interstate 5 and Interstate 90 will enter the tunnel through this station. [ ] International District Station is an open-air station, 1,060 feet long and 82 feet wide (about 15,400 cubic yards of concrete were used to build the station). A concrete lid over the southern portion of the station staging area is held in place by 131 support piles. The station will include entrances on Jackson Street and King Street. Union Pacific Realty is planning to build an office and retail complex upon the lid. The station also has an international flair. Symbols of the Chinese zodiac will be etched into the station plaza floor. The station platform walls will be lined with large steel panels embellished with designs in origami?a Japanese folded paper art form. [ ]

Jan 1, 1990

By X. Louw

"This paper examines the change in surface properties of the Polyurea used on spirals at different operational times: unused spiral, 28 months in operation and 58 months in operation. This is being done to investigate the alleged statement that spirals have a decrease in spiral separation efficiency after a certain period of operational time. Observing the surface characteristics under 1.5x and 36x magnification it can be concluded that the surface roughness decreases with increased operational time. This may be explained by a decrease in air inclusions and streak lines as the spiral surface wears. Decreased surface roughness should in theory have a beneficial effect on spiral separation performance. This leads to the conclusion that if a decrease in spiral separation performance is observed after a certain period of operation, it can’t be attributed to the change in surface properties. Uneven wear of the spiral surface, material creep or application of force to the spiral will change the profile of the spiral and could cause an adverse effect on spiral separation performance. The metallurgical test work showed that the best results are obtained at 30 - 35% solids by mass in the spiral feed. The iron recovery was significantly higher in the new spiral in comparison to the 2012 and 2010 spirals. The mass yield to concentrate in the new spiral was approximately three times more than for the older spirals. In conclusion, the yield combined with the grade, which equals the recovery was the best for the new spiral.IntroductionAn investigation was launched to research the common belief that spirals experience a decrease in efficiency, and therefore recovery, after a certain period of operation (a period of seven years has been used in the industry). The properties of the spiral that may have an effect on the efficiency are:"

Jan 1, 2017

By Charles Stone, Madan Naik, Drupad Desai, Karel Rossler

Planning of New York’s new subway line dictated the location of shallow underground station caverns and track crossovers. Clear span openings ranging from70 feet to 100 feet and lengths in excess of 1000 feet, coupled with low rock cover ranging from 25 feet to 40 feet required judicious selection of construction methods, equipment, and proper sequencing of the excavation stages. Rock classifications alone could not predict the behavior of the rock mass during construction. A robust design procedure that considered most of the important aspects of rock behavior and elements of shallow tunnel design, minimized the negative impacts of variable geotechnical data. This paper describes the intricacies of the planning and design of the $16 billion Second Avenue Subway with insight into how to overcome the design complexities and construction challenges of the urban underground.

Jan 1, 2005

THE Australian States and New Zealand have for many years provided instruction in mining, metallurgy, geology, and their allied subjects through their Universities and Schools of Mines. Though such education has been provided at considerable expenditure, there is no legal recognition whatever given to the holders of degrees, diplomas, or certificates granted by the authorities controlling these educational institutions. Certain of the, Australian States and New Zealand require, however, that mine managers and other officials employed by the mining industry shall 'hold' certificates granted by their respective Mines Departments.The position at present is that each educational institution is practically a law unto itself, and therefore in many ways there is a want of uniformity amongst institutions all aiming at the same result the training of mining men. The object of this paper is, in the first place, to point out certain aspects of this want of uniformity, and thereby how disabilities accrue. Some points in connection with the granting of State certificates will also be...

Jan 1, 1915

By R. Simonson

Agenda ? Need and Introduction ? Interface Management Programs ? Outcomes of Successful Interface Management ? Key Success Factors ? Lessons Learned ? Concluding Remarks Need for Interface Management ? Complex projects ? Larger in scale ? Physically dispersed and delivered remotely ? Involved with several stakeholders ? Risks thus imposed due to: ? Iterative and dynamic nature ? Large information flow ? Document revisions and information updates ? Related sources of Risk: ? Ineffective communication ? Poor work relationships ? Person to job mismatches ? Failure to clarify expectations

Aug 1, 2013

By L. M. Anisdahl

Ventiflex is a flexible ventilation duct system with a global market within mine and tunnel ventilation. The system is distributed in a wide range of qualities and dimensions. It is very important that ventilation systems are designed correctly in mines and tunnels. An incorrectly dimensioned system might result in bad air quality and too high costs. The objective of this study has been to assess some important design parameters for ventiflex comprising the friction loss factor for the duct wall itself, as well as the shock loss factors and the leakage factors for the different couplings systems. This has been obtained by carrying out a large scale experimental program on ducts with all the three different couplings: Velcro, zip and steel-ring. Pressure profiles and air flow rates have been measured, and based on these data the different factors have been calculated. The following results have been obtained: A friction factor l = 0,012 (K = 10) for the duct wall, a shock loss factor z = 0,0125 for velcro- and zip couplings, a shock loss factor z = 0,005 for steel-ring couplings, and a leakage factor f* = 0 mm2/m2 for all three coupling types. The latter result proves that no leakage is possible for a correctly installed duct with proper alignment. The results also confirm that ventiflex complies with class S, or better, according to the SIA-norm. However, whether ventiflex should be designed as class S, A or B according to the SIA-norm, depends on the particular application.

Jan 1, 2009

By D N. B Skinner, M P. Simpson

At Ohio Creek, 3 km northwest of the Thames bonanza goldfield, porphyry Cu-Au mineralisation is hosted in a dacite porphyry associated with porphyry intrusion breccias and overlying andesites and dacites. The geological setting is a Jurassic greywacke basement overlain by Late Miocene andesite-dacite volcanics which are extensively altered to propylitic and argillic assemblages. Diamond drilling at Ohio Creek in 1978-1981 by Amoco Minerals intersected low grade Cu-Au (0.12-0.20% C~ 0.23-0.4 glt Au) mineralisation An advanced argillic 'alteration cap containing quartz-alunite¦dickite or pyrophyllite-dickite¦diaspore is centred on the adjacent Lookout Rocks and has potential for high sulfidation Au-Cu mineralisation. There is a zonation from potassic K-feldspar-magnetitealteration at depth in the dacite porphyry, through an overlying phyllic quartzsericite- pyrite zone which is overprinted by pyrophyllite in the overlying advanced argillic cap. Early quartz stockwork veinlets associated with the potassic alteration contain fluid inclusions that trapped a highly saline (50-80 wt% NaCI equiv) fluid at high temperatures (450 to >600¦C) indicative of a magmatic fluid. Some chalcopyrite is associated with slightly later quartz-magnetite veinlets, but the bulk of the copper occurs as disseminated chalcopyrite associated with the phyllic alteration. The potassic alteration is surrounded and overprinted by propylitic chlorite¦epidote alteration. Late polymetallic sulfide-quartz-anhydrite veins occur within and around the margins of the porphyry system as in the Kaiser Reef. Fluid inclusions associated with these late veins were formed at temperatures of about 250-320¦C from low salinity (1-3 wfl~ NaCI equiv) fluids. The spatial association between porphyry eu-Au mineralisation, advanced argillic alteration and polymetallic sulfide veins suggests that they are genetically part of the same hydrothennal system. This is consistent with reconnaissanceK-Ar dates of 11.6-10.7 Ma for the intrusive porphyry at Ohio Creek, alunite in the advanced argillic alteration zone at Lookout Rocks and sericite selvedges from the Waiotahi gold-quartz veins at Thames.

Jan 1, 1998

By R. W. Hodder

"Archean lode gold deposits of both vein and chemical sedimentary types typically have major enrichments of certain rare elements, including Au, Ag, As, Sb, B, W, Se, Te and Bi, coupled with low or negative enrichments of the more abundant and mobile base metals, Cu, Pb and Zn. On the other hand, in massive base metal sulphide deposits Au, Ag, Cu, Zn and in some instances Pb are all enriched by a factor of 200 to 2000 t:'Jf'1pared to background and there is no large separation of gold relative to the base metals.The fluids from which gold was precipitated in veins were at temperatures of 320 to 480°C, at lithostatic pressure, had significant C02, and Na """" K; whereas the fluids which generated base metal deposits were at 250-300°C, at hydrostatic pressure, had C02 < < H20 and Na > > K.Many lode gold deposits are characterized by K, C02 and Si additions to their enveloping rocks, whereas base metal deposits typically have a fixation of Fe, Mg, Si and S in footwall rocks. Lode gold deposits may also have a relatively large halo of low-temperature oxidative, sadie spilitization in enclosing volcanic rocks, where seawater has later streamed into cooling stocks or flows that have initially acted to focus gold mineralizing fluids along thermal contraction fractures. The submarine environment is one hydrologically appropriate for the mixing of two initially independent hydrothermal systems, and the blending of their separate characteristics. Hence, lode gold and base metal massive sulphide deposits appear to be products of two distinctly different crustal and hydrological regimes. The former involves a high-temperature, high-pressure discharge of fluids which probably were generated during dehydration accompanying burial and progressive accumulation of volcanic-sedimentary sequences, with an additional influence of marine water in the near-sea-floor environment. The latter represents thermally driven convection of ocean water at lower temperatures and under hydrostatic conditions.Auriferous fluid systems with only minor base metal content could plausibly be generated during dehydration accompanying burial and metamorphism, when the water-to-rock ratio is low and halogen availability is limited by crustal abundance (- 60 ppm Cl). These two factors may constrain the uptake of the abundant base metals into fluids, but the solubility of rare elements is not constrained by limited fluid; and preferential uptake of Au along with other rare elements may be promoted if such elements compete more successfully for the limited halogens than the base metals, and/or have an alternative complexing agent such as CO or C()j-."

Jan 1, 1982

By Ross Byron, Ken Roberts

"During the fall of 2001 a program was initiated to determine the feasibility of improving the metallurgy in the flotation circuit at the Penhorwood Talc Concentrator located near Timmins, Ontario. Bench scale testwork led Plant staff to believe that opportunities existed to improve the flotation performance. Pilot scale testing was then conducted using two vendors and their respective cylindrical type flotation cells to indicate where these opportunities existed.The results of the test program determined that the replacement of the existing flotation circuit (roughers, scavengers and cleaners) with new flotation cells could be economically viable. Justification was due to a reduction in installed horsepower, maintenance costs and a subsequent increase in recovery and throughput while maintaining product quality. Unforeseen benefits included reagent and air reduction, accurate level control as well as improved working conditions due to the removal of the antiquated equipment and ancillaries.This paper will detail the justification, installation and implementation of the new flotation circuit. A special emphasis will explain the hurdles encountered while trying to install and commission the circuit in an operating Concentrator with minimal interruptions to production.INTRODUCTIONThe Penhorwood mine and Concentrator is 28 yrs old and has gone through many ups and downs with different owners, Johns Manville, Steetley Talc and now Luzenac. It has also been expanded twice, with flotation and grinding capacity being added in recent years.All of the concentration is completed at the mine site while the fine grinding takes place in the Timmins micronizing plant.Luzenac’s Philosophy is to be the world leader in Talc production, technology and sales, having about 70% of the current world High Grade talc market."

Jan 1, 2004

By A. G. Doll

"Many power-based grinding models exist, and most operators are familiar with Fred Bond's ""third theory"". Bond's model is most commonly used to describe primary and secondary grinding to product sizes above, for example, 100 µm. Operators sometimes use Bond's equation to describe grinding in situations where it is not appropriate, such as fine grinding below 50 µm. Using an alternative model would be a better choice in this situation.Bond's equation is one in a large family of models. Related equations better suited to fine grinding include the “signature plot”, Von Rittinger's model and Charles' equation. These models have a similar form to Bond's and can be fit to industrial regrind mills and laboratory tests using the simple regression tools in the charts of computer spreadsheets. Operators will find that fine grinding calculations are both easier and more accurate when using the alternative equations to fit their regrind milling surveys or when performing laboratory regrind mill scale-up for plant design.None of these models are new: Charles' equation was published in 1957 and Von Rittinger's model was proposed in 1867. A quick refresh how to apply these equations can turn these oddities from the undergraduate curriculum into useful tools for plant optimization. They can be fit to any type of mill including stirred and tumbling ball mills.IntroductionBuilding a case for fine grind modelling requires reviewing some theory before building a framework for doing fine grinding calculations. The actual calculation procedure recommended is easy and can be applied by plant metallurgists. Don’t be frightened by the theory; the end result is reasonably simple.The observation that mineral breakage is related to the absorption of energy is usually attributed to Von Rittinger (1867). Lynch and Rowland (2005) describe that the ability to empirical test and calibrate energy models of breakage didn’t exist until the widespread adoption of electric motors in the mining industry during the 1930’s and 1949’s. A series of technical papers published by the Allis Chalmers company during the 1940’s demonstrate that they were attempting to do such a calibration using Von Rittinger’s model which is usually stated as: “the energy consumed in the size reduction is proportional to the area of new surface produced.”"

Jan 1, 2017

When perusing articles which treat of mining geology, and when talking with miners on the field, one is at times unable to follow the exact thoughts intended to be expressed, owing to the introduction of occasional technical words, the meanings of which are not thoroughly understood either by the speaker or by the hearer, or possibly by both and laymen at times accuse their technical brethren of attempting to confuse them by employing unusual words in their conversations and writings. Technical words are necessary adjuncts to all arts and sciences. They creep into our language, frequently unnoticed by those who employ them, as being more concise and convenient than longer sentences to explain frequently recurring expressions. In many cases these words give the finest shades of meaning, such as aglomerate and congzomerate, but in others they are extremely ambiguous, for instance black sand, which in some places means ilmenite, in others, chromite, tourmaline, cassiterite, in fact, any black mineral occurring in the form of sand. Then, again, much confusion is cansed by the same rock or mineral having different names, e.g, jlu01&apos;spa&apos;i&apos;, which is known as cand, cann, cauk, kawk, blue-John, Derbyshire spar, &amp;c. The multiplicity of local names is of course chiefly found among the more common minerals, which are widely distributed some people have a propensity for using words the meanings of which they understand as little as&apos; they do how to pronounce them. We have heard such persons speak &apos;of vughs as &quot;bugs,&quot; and oxides as &quot;ox hides,&quot; and to show that there was no mistake in their intentions, we have seen these and other words written in the same way as they were pronounced. Then, again, some persons, relying more on examples than definitions, get a very vague idea as to what the true meaning of a term may be the word dimite is an example in point, which we have frequently heard applied to any dyke rock that the miner was unable to recognise as granite in fact, he uses the word in a general sense, just as the field geologist provisionally employs the word &quot; greenstone &quot; for certain rocks, until he has an opportunity of thoroughly investigating their character.