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By Mostafa Mossaad, Ali Helwa, Manal Salem

Support of excavation (SOE) design practice tends to model SOE elements using two-dimensional (2D) analyses to avoid the complexity associated with three-dimensional (3D) analyses. Such practice overlooks soil arching in the horizontal plane and prevents designers from accounting for elements such as capping beams as part of the statical system. This study simulates square excavations supported by cantilever slurry walls in dry cohesionless soil using 2D and 3D finite element (FE) models. First, side support wall behavior is compared from 2D and 3D FE models for variable excavation length to depth (L/H) ratios. Second, the effect of slurry wall lateral bending stiffness on wall behavior is studied by modeling the wall using plate element with isotropic and anisotropic wall stiffness. Finally, the sensitivity of cantilever wall behavior to the presence of capping beam is illustrated. The study concludes that unbraced excavations with L/H ratios greater than 5 almost resemble plane-strain conditions. Slurry walls are better simulated in 3D FE models by dividing the plate element into discrete panels or by assigning anisotropic bending stiffness to the plate element. Finally, the presence of capping beam affects the behavior of cantilever walls resulting in reduction of deflections and redistribution of bending moments. INTRODCUTION Support of excavation (SOE) design practice ranges in complexity from conducting simple hand calculations to performing three dimensional numerical modeling depending on several factors among which is the geometry of the design problem. This paper addresses walls that are designed using numerical modeling, and discusses the factors governing the choice of the most suitable modeling approach. It has been believed for a while that modeling excavations using 2D numerical models would lead to a more conservative solution, which turned out to be incorrect in specific cases. This paper attempts to describe cases where 2D finite element modeling could be on the conservative side and other cases where it could be less conservative than the more complex 3D modeling.

Jan 1, 2018

By A B. Christie

Known epithermal deposits in the Coromandel region belong to the low-sulphidation type, represented by three subtypes: (1) andesite-hosted epithermal Au-Ag, (2) rhyolite-hosted epithermal Au-Ag, and (3) andesite-hosted polymetallic veins. Paleo-depths for a range ofdeposits are estimated using various features including: paleo-surface indicators (e.g. sinters), hydrostatic pressures estimated from homogenisation temperature measurements on fluid inclusions, and alteration mineralogy. Paleo-depth estimates to the base of the ore zone for the rhyolite-hosted Coromandel deposits are in the range 200 to 500 m. Andesite-hosted Au-Ag deposits have more variable paleo-depths, and are deeper (up to 950 m) in those deposits with base metals at depth. The majority of Coromandel Au-Ag deposits have limited depth extents (<200 m) of economic grade mineralisation, although Waihi and Karangahake are notable exceptions with depth extents of 575 m and 700 m respectively. Limited depth extents of economic ore are a feature of epithermal systems worldwide and are commonly attributed to gold deposition from boiling fluids. Under hydrostatic conditions in epithermal/geothermal systems, boiling in an up-flowing hydrothermal fluid is controlled by the boiling point for depth (BPD) curve. From fluid inclusion studies of many low-sulphidation epithermal systems, deposition of electrum in economic concentrations appears to be confined to a temperature window of 260 to 180¦C. This means that for dilute, gas-poor fluids that follow the BPD curve, gold deposition is limited to a vertical depth zone of about 400 m, with its upper boundary at about 100 m below the ground surface. The greater depth extent at Waihi and Karangahake, can be explained by mixing of/a deep, hot (300¦C) fluid with cooler (c. 200¦C) heated ground waters. This has the effect of lowering the 260¦C isotherm by up to 300 m, thereby increasing the depth range of economic grade gold deposition within the 260 to 180¦Cwindow of electrum deposition.

Jan 1, 2000

By N. Shariatmadari

In recent years, determining bearing capacity of piles from in-situ testing data as a complement of static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating base bearing capacity of piles from SPT data has been compared and evaluated. A new method for pile base bearing capacity in sand is proposed using SPT records. Data averaging, failure zone extension, and plunging failure of piles have been addressed in the proposed approach. A data bank comprising 10 full scale static load tests on instrumented piles and 26 dynamic tests, analyzed with signal matching technique by CAPWAP software, was used for validation. The SPT data that was performed close to pile locations is also included in the data base. Comparison of current methods by error investigation with Log-Normal approach demonstrates that the proposed method predicts pile base capacity with more accuracy and less scatter in comparison to other methods.

Jan 1, 2006

By Germán Rodolfo Ocampo Castillo

El presente texto señala la incrementación de la productividad de la mina Xstrata Tintaya -Antapaccay a través del contrato de personal adicional, donde se reemplace a los operadores titulares durante la hora de refrigerio y asi mantener una operación contínua en la mina. Como consecuencia de ello, se incrementará la cantidad del mineral descubierto en la mina y por ende, el costo unitario de las libras de cobre adicional por operación contínua se reduce.

Sep 12, 2011

By Gerald Whittle

What is Enterprise Optimization? Releasing value through better planning decisions: Philosophy, Methodology, Software The key to 5% -35% increase in enterprise value (NPV) The culmination of 25 years development in optimization for the mining industry ?Jeff Whittle Simultaneously optimizing: ?all steps in the value chain ?all assets in the enterprise portfolio ?all periods together

May 1, 2010

By Cameron J. Clayton

Cumberland Resources Ltd. is currently planning to develop the Meadowbank Gold Project located some 70 km north of Baker Lake, Nunavut in the eastern Canadian Arctic region. The Meadowbank Gold Project currently consists of up to 6 main gold bearing deposits within relatively close proximity to one another which are planned to be mined primarily as a truck-and-shovel open pit operation and using conventional gold milling and extraction. The mining plan indicates that approximately 20 million tonnes of ore will be mined over a mine life of 8 to 10 years. The operation will generate approximately 160 million tonnes of mine waste rock and about 20 million tonnes of tailings. The site is located in an area of continuous permafrost with mean annual average air temperature of -11 °C and average annual precipitation in the range of 100 to 200 mm. Lakes cover a large portion of the site, including some of the ore deposits. The location of the site, and the physical environment, pose challenges to development. This paper presents some of the designs considered to effectively manage and utilize the waste products of mining at the project.

May 1, 2004

By Robert Thomas

DURING the past 20 years the advantages of reinforced concrete as a substitute for timbering in so-called permanent mine openings have been fully recognized, and its use has become almost general practice in the larger mines. The term "permanent mine openings" is used advisedly and is assumed to embrace such openings as ventilation shafts, material shafts and main hoisting shafts, with their adjacent stations, ore pockets, etc. In the concreting of such openings, the actual cost as compared with that of timbering has been of secondary consideration, the support of large openings, elimination of fire hazards, and prevention of inter-ruptions to production being the primary objectives. The ultimate economy, however, of lining such openings with concrete when they are to remain in use during the entire life of the mine, and especially when they are in bad ground, will seldom be questioned. During this 20-year period there have appeared in engineering publi-cations a number of interesting articles on the use of concrete in mines, nearly always describing some specific project of major proportions, such as the concreting of ore pockets, large stations or main hoisting shafts. Such articles are unquestionably of interest, since the projects require considerable engineering thought, not only in the method of excavating large openings, but in their engineering design as well. Concreting of main hoisting shafts, particularly when this is done with the least possible interruption to production, provides some interesting problems. The concreting of haulage drifts of the dimensions commonly found in mines, on the other hand, soon develops into a routine operation, there-fore it is with some hesitancy that the author attempts to prepare an article on this subject. The writer can recall only one article on the concreting of mine haulageways, although several articles have been written concerning the concreting of tunnels considerably larger in dimensions than those required in general mine practice.

Jan 1, 1936

By K. E. Barnes

"The IsaMill was developed for fine-grained ores that required at least double the grinding efficiency of ball or tower milling to be economic. This was achieved, but in practice, the benefits of using inert media (eg sand, slag, ore, ceramic) have proven to be at least as important as the higher grinding efficiency. Flotation selectivity and rate was improved for all particles, particularly fines. This allowed a dramatic simplification of the Mount Isa lead zinc flotation circuit – adding 6 MW of ultrafine grinding power reduced reagent addition and flotation volume and increased plant energy efficiency. This was quite unexpected.This paper examines four orebodies that were enabled by inert grinding – McArthur River, George Fisher and Black Star Open Cut Mines (complex fine-grained lead zinc orebodies in Australia), and the Western Limb Tailings Retreatment plant (a PGM operation in South Africa). In a unique case history, the operating performance of the Mt Isa lead zinc concentrator is explained by size-by-size mineralogical data collected over 25 years, systematically explaining the impact of declining ore quality, and the effects of additional conventional grinding, inert grinding, and circuit and reagent redesign.The mineralogical case histories are so compelling that it is argued that the advantages of inert grinding should not be confined to difficult, fine-grained orebodies. The availability of largescale efficient inert grinding mills could have profound impact on circuit design for many orebodies.INTRODUCTIONThe IsaMill was developed by MIM (now Xstrata) to enable the development of the McArthur River Orebody in the Northern Territory of Australia. This ultra-fine grained ore needed a grind size of 80% passing 7 microns to produce a saleable concentrate. Such a fine grind was not economic with conventional ball or tower milling. Below about 25 microns the low energy efficiency and high media consumption of these mills is prohibitive. Critically, the high steel consumption and associated change in pulp and surface chemistry also seriously affects flotation metallurgy."

Jan 1, 2006

Gravity-driven rock falls account for a large proportion of all fatalities and injuries in underground mines. Potentially unstable blocks of rock are found in the hanging wall of excavations, which may be delineated by natural joints or stress fractures. These blocks, referred to as keyblocks, will fail if their weight exceeds the support capacity or if they are located between support units. This paper describes a computer program which simulates blocks in the hanging wall of an excavation based on measured properties of fractures and joints. Keyblocks are identified and placed at random locations in a predefined excavation. The keyblocks are tested against the support to determine whether they fail the support, drop out between the support or are stable. By repeating the procedure several thousand times, statistics of the probability of failure of the keyblocks are obtained. This approach allows the relative hazard associated with different types of support or excavation orientations to be obtained. It is concluded that a probabilistic approach is suitable for the evaluation of supports effectiveness in situations where large numbers of discontinuities or stress fractures are exposed in excavations.

Jan 1, 1998

By Masaki Kitazume, Yoshiaki Kikuchi

"Abstract Pile foundation is one of fundamental techniques to improve the bearing capacity and settlement characteristics of superstructures. Wide varieties of piles having various shape, size and material were developed and have been applied to a lot of construction projects throughout the world. The deep mixing method, an in-situ admixture stabilization method, was developed in 1970s in Japan and the European countries, and has been frequently applied to many construction projects for various improvement purposes such as increasing bearing capacity and horizontal resistance, reducing ground settlement, preventing liquefaction and so on. The design methods, execution procedure and quality control and assurance (QC/QA) of the method are standardized or specified in many countries. These standards, specification and/or technical manual have been a remarkable contribution to spread the techniques throughout the world. The QC/QA is one of the major concerns for clients and engineers who have poor or no experience of the technologies. In order to assure the high quality of deep mixing work in the global market, it is necessary to establish the concept of QC/QA and correlate the output of different procedures. Upon the request by the organizing committee of the DFI-EFFC International Conference on Piling & Deep Foundations, the authors conducted survey of the specifications and standards on the piling and deep mixing technologies in Asian countries. In this manuscript, the results of survey are briefly introduced by comparing these specifications and standards.IntroductionThe pile foundation is one of fundamental techniques to improve the bearing capacity and settlement characteristics of superstructures. Wide varieties of piles having various shape, size and material were developed and have been applied to a lot of construction projects throughout the world. The design method, execution procedure and quality control and assurance of pile foundations are standardized in many countries based on the accumulate research results, laboratory and field experiences. In Japan, steel pipe piles are mainly constructed by hammer driven in port construction. On the other hand, precast pre-stressed concrete piles or cast-in-place piles are mainly used in on land construction. When precast pre-stressed concrete piles are constructed, piles are usually set by inner excavation method because of preventing noise and vibration problems. More than 50 years ago, noise and vibration problems had not been serious problem in Japan, but around 50 years ago, they became serious and now less noise and vibration construction methods are used for pile construction on land in Japan. In Asian countries, though piles used for construction have a lot of variety, precast pre-stressed piles are commonly used. In this report, execution controls of construction methods of steel pipe piles and precast concrete piles are mainly considered."

Jan 1, 2014

By Shadia J. Ikhmayies

Nanocrystalline CdS:In thin films with particle size in the range (3-36 nm) were produced by the spray pyrolysis technique on glass substrates. The films were characterized by investigating their X-ray diffractograms (XRD), scanning electron microscope images (SEM), transmittance curves and photoluminescence (PL) spectra. The size of the nanocrystallites was estimated from XRD difractograms and then from the hyperbolic band model and the bandgap energies of the nano- particles, which were calculated from the positions of the minima in the first derivative curve of the absorbance. Fine-structured PL spectra confirmed the nanocrystalline nature of the films.

Jan 1, 2010

By Charles De Witt

The ore treated at the reduction plant (called Yangdei) of the Chiksan -Mining Co., Korea, is brought from four of the company mines, and from the small tribute mines. The largest shipments conic from Sajunkohl mule, situated about a mile and a half from the mill (Fig. 1). The ore is quartz of medium hardness. The overage assay value in gold is $6.95 per ton. At the mine the ore is put into bin,, and is Mien trammed over an 8 per cent. grade to the tipple bins above the mill, where the ore is drawn through the hull holes as desired. The capacity of the tipple bins is about 3,500 tons. On, from Moonsukohl, Chung Tarrie, Yang Chun, and the tribute mines is brought in by bulls and bull wagons. The bulls carry from 350 to 800 lb.; the average wagon load is about 1,200 lb. (Fig. 2). One shovelful of ore out of every ten is taken as a sample. Considerable ore

Jan 5, 1915

By Arnold Hammons

Automated temporary roof support (ATRS) systems have been incorporated into roof bolters since the 1970?s. During roof bolting, many injuries have occurred from large pieces of draw rock falling inby the ATRS beam and tipping back into the operator?s area. Other injuries have occurred due to smaller, sharp rocks falling onto the operator?s hand and arm during initiation of roof bolt drilling. These injuries are attributed to weak immediate roof, sometimes called roof skin failure. Even though ATRS systems support the roof and provide a measure of protection against roof skin failure, additional hazards sometimes do exist immediately inby and outby the supported roof. Design innovations such as the ATRS mounted rocker pad deflector systems have been designed to improve the roof bolter operator safety. This paper will inform the reader of the hazards, machine evolution through different design solutions, and the current state of the art in preventing roof skin failure injuries when roof bolting.

Jan 1, 2009

By Fisher N. I

Disequilibrium ratios (U3O8/eU3O8), which assess the degree to which gamma activity represents the uranium content of a sample, have been measured on a representative set of samples from the ore zone of a carnotite ranium deposit located at Yeelirrie, Western Australia. A statistical analysis has been performed to investigate the dependence of the ratios on lithology and on the location of the sample in the orebody. The analysis indicates that dependence on lithology and on position across the orebody is negligible. Samples from the western end of the orebody and those from below the water table level tend to have slightly lower ratios than samples from other positions, although these trends are small compared with a large random variation in the data. The large random variation could result from some redistribution of the daughter isotopes of uranium within the orebody. On the basis of the results from all the samples, the estimated deficiency of uranium relative to radium in the ore zone of the deposit is 11 per cent.

Jan 1, 1980

By Steven Dapp

A new hyperbolic model for generating P-Y curves is developed for use in lateral analyses of cemented soils (a ?C-F? soil with both cohesive intercept and friction angle), and includes degradation of the static loading soil response to model the effects of load cycling (repeated loading) with load cycle number. The p-y curves, for both static and cyclic loading, were derived from full-scale lateral test results conducted on a set of six drilled shafts in a loess deposit at the Kansas DOT test site. Values of the model parameters obtained from the load testing at this site are presented, as well as a discussion of the model parameters effect on the results such that the model may be rationally applied to other sites with C-F type soils. A step-by-step procedure is presented to illustrate the application of the model. Correlation of the model to the CPT cone tip resistance (qc) from CPT testing is made, as this was found to be the most reliable; However, the model is applicable to other methods, both in-situ and laboratory, of assessing the soils strength.

Jan 1, 2011

By TvS. von Moltke

Steel is a highly versatile material due to its low cost and good mechanical properties, but typically needs some or other form of corrosion protection due to its tendency to corrode when exposed to atmospheric conditions. In the case of organic coatings, the corrosion protection and functionality of the final product is critically dependent on the adhesion of the coating to the surface of the steel. In this work the effect of contaminants and the nature of the surface layers present on industrial steel products are investigated by means of paint adhesion tests, Auger electron spectroscopy (AES), and X-ray Photoelectron spectroscopy (XPS). It was found that the presence of sodium species on the surface is very detrimental to paint adhesion under wet conditions, while satisfactory adhesion may be obtained even in the presence of silicon and carbon residues. It was also found that the nature of the Fe-O layer, formed under wet conditions is labile and different from that formed in dry air, and that subtle changes in process conditions, such as changing the oxygen content of the quench water, may change the adhesion of paint to the surface of the steel. Lewis acid-base interactions are discussed as a mechanism that may determine the bonding between the steel and polymer coating.

Jan 1, 2003

By Noel Dent

Increasing interest is being expressed in the development and availability of Electronic Delay Detonators throughout the world. Particularly in open-cast mining, the benefits associated with precise, reliable initiation systems are perceived to be considerable. Many of the systems currently being developed have sophisticated programming requirements associated with them, or are numbered systems that require predetermined layouts to determine timing patterns, and importantly are far more expensive than existing initiation systems.

Jan 1, 1994

By D R. Peacor, J L. Mauk

Dioctahedral clay minerals in the volcanic-hosted Golden Cross epithermal Au deposit, New Zealand, have been investigated by petrography, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy/analytical electron microscopy (TEM/AEM) to determine the nature of these minerals in a hydrothermal ore deposit. Heterogeneity in the distribution of dioctahedral clays is observed from the hand-specimen scale to the TEM scale, indicating that primary rock textures and fluid pathways (related to rock type, porosity/permeability and fluid/rock ratios), in addition to temperature, are important factors controlling the distribution. As the proportion of illite in mixed-layer illite/smectite (I/S) decreases, TEM observations show decreasing layer stacking order, parallelism of packets, and packet size, and increasing apparent porosity. AEM structural data show a corresponding decrease in AlIV, AlVI, and K+, and an increase in Si, Ca2+, and Fetotal. The observations of this study indicate that local dioctahedral clay mineral reaction progress is controlled mainly by permeability and structure, but that this is superimposed on a predictable, system-wide clay mineral distribution that is controlled by temperature and fluid/rock ratio.

Jan 1, 1999

As the surface reserves are being depleted, more and more stone operators are seeking underground mining options. Stability of underground openings is a major concern for the safety and productivity. This paper relates to a field study conducted at a large underground limestone mine in Central Pennsylvania. Identification of hazards leading to ground failures and assessment of roof fall risks are important in mitigating injuries. Field observations at this mine were integrated with Roof Fall Risk Index (RFRI) mapping software recently developed by West Virginia University. The system is designed to combine field study data related to geologic factors, mining-induced damages, roof profile, and ground water influx to generate RFRI maps. The mine has adopted a proactive ground control program consisting of comprehensive examination of drilling and bolting logs; precision surveying of roof and rib; accurate mapping of cutters, falls, and geologic structures; and installation of extensometers and microseismic monitoring systems. Investment of time and resources has eliminated fatalities and lost-time injuries due to ground fall. This paper presents the geologic settings, mining conditions, ground control issues along with risk management and control techniques adopted at the study mine.

Jan 1, 2009

A dedicated tunnel construction version of the Caterpillar 328D LCR compact radius excavator is proving highly productive on the A9 Autoroute construction project near Visp, in Switzerland. It is the first machine of its kind to operate on a Swiss contract and uses a special dedicated front attachment designed and constructed by German Caterpillar dealer Zeppelin. The machine offers a powerful, stable and compact solution for tunneling contractors. A rear overhang of just 305 mm (12 in.) provides a tail swing radius of just 1.9 m (6.2 ft). The 328D LCR is ideal for the restricted working areas within a tunnel construction site. The machine is equipped with the wide tracks from the 330D L conventional crawler excavator, ensuring maximum stability when operating. In addition, the boom mounting has been moved further toward the center of the machine for the tunnel model, creating an increased lift capacity over the front end compared with a standard 325D L. The boom itself features a robust box section construction, with high-strength steels, additional supporting struts and reinforced bearings for maximum durability. All pins have hard-chromium plating for optimum protection against wear. Stick digging force is a powerful 134 kN, with up to 212 kN of bucket digging force available, for maximum penetration in blasted material. The 328D LCR is also equipped with a heavy-duty dozer blade as standard. This ensures outstanding stability when working and providing a useful secondary tool for clearing and leveling within the jobsite. Two 45° tilting mechanisms in the boom construction, allow the boom to be swung to 45° on either side of the machine. So the specially designed attachment linkage provides increased rollback for access to the roof of the tunnel. A Caterpillar CW45S mechanical quick-coupler allows rapid changes between specialist tunneling attachments, standard Caterpillar buckets and a range of Caterpillar work tools. The machine is powered by a Caterpillar C7 diesel engine. This six-cylinder EU Stage IIIA diesel motor [ ] offers 8 percent more power than its predecessor, with 140 kW (190 hp) available at just 1,800 rpm. Caterpillar?s ACERT combustion technology results in lower fuel consumption and reduced exhaust emissions. However, the tunnel machine is also equipped with a diesel particulate filter as standard, to further cut exhaust gases within the tunnel working. The 328D LCR is designed for use in transport tunnels of 6.8 m (22.3 ft) in height. With the tunneling boom in place, the machine has an operating weight of 42,540 kg (93,783 lbs), yet retains a transport height with the tunnel boom of just 3.9 m (12.8 ft). Transport width with 600 mm (23.6 in.) track shoes, is just 3.2 m (10.5 ft). On the A9 tunnel contract, the machine is being used by a consortium of Swiss and Austrian companies working for the canton of Valais? Routes Nationals Construction (RNC) department. The 31.8-km (19.7-mile) A9 Autoroute construction project will connect Sierre in the west and the town of Brig to the east. The tunnel that is bypassing the town of Visp is just one of a number along the mountainous route.

Jan 1, 2009