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By Weber D, Knox PR

The criteria developed for the Argyle Diamond Mine process plant control system are reviewed. The control system installed is described along with a discussion of the method of implementation adopted. The control system was extensively tested prior to instal- lation at site. This approach led to signi- ficant time savings during plant commissioning and facilitated rapid escalation of plant production. The control system has performed satisfactorily with a high level of operator acceptance and basically satisfies the criteria Developed.

Jan 1, 1986

By R. L. Perrine

A stability theory is developed for miscible liquid-liquid displacement within a porous medium. In the usual case considered, a high-density high-viscosity "oil" is displaced downdip by a low-density low-viscosity "solvent'! Perturbation methods are used to find the conditions under which the spreading mechanism changes from the stable dispersion process to unstable viscous fingering. We find that instability is conditional, that there is a dependence on the shape of a disturbance leading to a"diameter" effect and that very difficult experimental scaling problems may result. A useful consequence is the definition of a minimum "slug size" for stable miscible displacement. This should make possible optimum use of the solvent process for oil recovery. The results may apply to many situations in which one fluid displaces another of somewhat different fluid properties within a porous medium. INTRODUCTION The process of miscible liquid-liquid displacement looked very favorable when it first received serious consideration as a means to increase petroleum recovery. Some early laboratory results were interpreted to mean that only a small "slug" of solvent was needed, perhaps 2 to 3 per cent of a hydrocarbon pore volume. This "slug" could recover the oil in an entire reservoir provided the fluids remained miscible.1,2 Only a slow growth of the "mixing zone", or gradual transition from oil to solvent, should occur. This would follow naturally from mixing by a dispersion mechanism such as that described by Scheidegger.3 And, indeed, laboratory cores have shown this kind of behavior provided solvent viscosity was at least as great as that of the oi1.2,4-6 The same kind of behavior has also been observed with solvent viscosity lower than that of the oil after the distance traversed became large. Not all laboratory results have been this favorable, however.7-9 Mixing zone growth may become proportional to the distance traveled rather than the square root of this quantity. Such behavior accompanies high rates in short systems of large diameter, provided the viscosity ratio is adverse. If this more rapid spreading were to persist in a reservoir, the solvent requirement for miscible "slug" displacement could exceed 30 per cent of a pore volume. There is considerable economic importance in the difference between 3 and 30 per cent solvent. A 1ogical conclusion is that two different kinds of flow behavior are possible, with each kind leading to a different result. One kind gives efficient displacement, the other does not. In the efficient case, the solvent bank spreads out only by the mechanism we have termed dispersion. Under these conditions, displacement is as near piston-like as possible. In the second kind of flow, found only with adverse viscosity ratios, viscous fingering occurs. That is, permeability variations cause a small finger of low-viscosity solvent-rich fluid to move ahead of its average position within the mixing zone. This creates a path of low resistance to flow, and an even greater amount of solvent-rich fluid follows. Thus, the process is autocatalytic. Once started, the fingering mechanism rapidly becomes dominant. The question to be answered is this. Under what conditions will each of these two different kinds of flow occur? In particular, what conditions denote the transition from dispersion to viscous fingering as the solvent spreading mechanism? The answer may tell us whether or not the desirable, near piston-like miscible displacement process is practical. An answer to this problem can be obtained from theory by the use of perturbation methods. The procedure is as follows. We first formulate a mathematical representation of the system. Then a small disturbance (or perturbation) in solvent concentration profile is introduced and observed to see what happens. Unstable flow is indicated when a small disturbance will grow larger. This will lead to eventual viscous fingering. If on the other hand the disturbance dies out, the displacement is stable. In this latter case, with dispersion as the spreading mechanism, near piston-like displacement is possible. Thus, this paper presents the development of a stability theory for miscible liquid-liquid displace-

By George A. Morrison

The Columbia Chemical Division of the Pittsburgh Plate Glass Co. is at Bar-berton, Ohio, 35 miles south of Cleveland. For many years large tonnages of limestone have been brought to the Barberton plant from distant points. The stone is here burnt in vertical kilns, the resultant product then hydrated and the hydrated lime used in chemical processing. To eliminate the expense of these shipments, the company decided to investigate a limestone bed known to exist on company property at Barberton, where the stone is used. The bed lay at a depth of more than 2000 ft. and was known locally as the "Deep Lime." Chemical analyses of sludge from churn-drill holes made some years ago proved that the limestone was of sufficient purity to warrant diamond-drill exploration. Four diamond-drill holes were put down at well-spaced intervals, to represent fairly an area of four miles by one mile. Cores logged as to chemical and physical conditions were found to compare closely, and to corroborate the earlier evidence that the limestone was of superior quality for chemical use. A plant of 300 tons per hour was subsequently decided upon. SITe The yard at the chemical plant was already so congested that location of the projected mine within its area could not be considered. Eventually a site was selected 2 miles northwest of the plant, near the main line of the Erie Railroad. Here 412 acres were owned outright by the company and stone rights were obtained on 2 50 additional acres. This location required a transportation line of nearly 2 miles (8800 ft.), crossing two major highways, and to avoid interruption of deliveries to the plant, overpasses were planned. Geology The limestone in the immediate vicinity lies about 2200 ft. below the surface. Geologists* identify this stone as Delaware of Devonian age. It is overlain by 18 ft. of unconsolidated (sand and gravel), 100 ft. of water-bearing sandstone, and finally 2080 ft. of shale into which sandstone in thin layers is interbedded. The contact of shale and limestone is abrupt, flat-lying and very pronounced. Berea sandstone, often found at 520 ft., is absent, but Euclid sandstone was encountered, together with a seepage of oil and a small amount of methane gas. The limestone bed itself is 345 ft. thick, and overlies 200 ft. of gypsum. The lower part becomes dolomitic as it approaches the gypsum. A detailed study of the drill cores indicates that the upper 50 ft. are highest in lime and reasonably low in silica. The physical make-up shows several separating cherty layers. These occur at definite horizons and cause distinct partings, which become horizontal planes of

Jan 1, 1946

By Jei Y. Choi, P. G. Shewmon

Using a scratch smoothing technique, the magnitude and the ratio of the surface diffusion coefficients (D,) in two orthogonal directions have been measured on copper for over 100 different surface orientations. Anisotropy was found for all surface orientations except those lying near the (100) and (111); however, these anisotropies were rarely greater than 2.0. The direction of maximum D, appears to coincide with the direction of step edges on any given surface, and if no such steps exist, no anisotropy is found. Thus the jump frequency along a step edge is shown to be faster than the frequency of a jump over the step. The values of Ds and AH for the (100) and the (111) orientations agree quite well with those obtained earlier by the grain boundary grooving technique. It is proven that the directions of maximum and minimum D, (the principal axes) for any surface orientation are known if the perfectly ordered plane corresponding to the given surface orientation possesses a plane of mirror symmetry. Thus the principal axes of D, for orientations lying along the sides of the unit stereo-graphic triangle are always known independent of the extent of thermal disorder or impurity adsorption. The merits and shortcomings of King and Mullins' recently published equations relating Ds to the rate of scratch smoothing are discussed. 1N an earlier paper the authors have reported the variation of the surface diffusion coefficient (Ds) with surface orientation on copper.' In that study Ds was determined from the rate of growth of grain boundary grooves on symmetric bicrystals. This gave values of Ds from 850° to 1070°C in a given direction on each of the six surfaces. It was found that the activation energy for surface diffusion was essentially the same for all six surfaces. The theory developed to explain these data assumed that the free energy of any given type of surface site depends only on the number of nearest neighbors the atom has. This same theory predicted that on any given surface Ds should be independent of direction. The primary aim of this study was to check the validity of this prediction for a wide range of surface orientations on copper. The growth of grain boundary grooves is ideal for studying Ds in a given direction on a given surface over a range of temperatures, because the same specimen can be repolished and used again. However, there is considerable work involved in growing a symmetric bicrystal, and for a survey of Ds in two or more directions on many surface orientations, the technique would be arduous. A better technique appeared to be the scratch method used primarily by Mykura. 2 If a scratch is placed in a surface whose surface tension is independent of orientation, the surface will smooth out in time under the influence of surface tension. To determine D, from this flattening, Blakely and Mykura2 used an approximate solution which was assumed to describe the rate of flattening. Recently King and Mullins3 (hereinafter K and M) have given a more exact analysis of the flattening of an isolated scratch. A second aim of this paper was to check the validity of this newer analysis and compare the values of Ds determined thereby with the values obtained from grain boundary grooving techniques. EXPERIMENTAL PROCEDURE In an effort to work with a particular predetermined surface orientation, light orthogonal scratches

Jan 1, 1963

By Harvey T. Kennedy, Erasmo T. Guerrero

In this investigation, the effects of the surface tension of brine and the interfacial tension between oil and brine on the recovery of oil by water flooding of Woodbine sand were studied. Variation of the surface forces was obtained by the addition of small amounts of commercially available chemicals, which did not appreciably change the surface tension of the oil. Fourteen surface-active agents, which were found to be effective in lowering the surface and interfacial tensions, were further investigated to determine the extent of their adsorption by the Woodbine Sand cores. It was found that adsorption was sufficient in all cases to prevent any substantial concentration of chemical at the flood front. The flow system was, therefore, brought to equilibrium with definite concentrations in the flood water by circulation before each test. The data thus have no relation to the results obtainable by using the chemicals in full-scale water floods, but should be helpful in predicting the performance of surface-active chemicals which are not lost by adsorption, if such can be found. Flow tests were made on various concentrations 01 six chemicals selected from the 14 investigated for surface activity and adsorption, with and without the presence of gas in the core. It was found that lowering the interfacial tension had a tendency toward reducing the recovery of oil and that the reduction of the surface tension of the brine had little or no effect. A substantial beneficial effect, however, resulted from the presence of gas in the cores. INTRODUCTION The movement and distribution of crude oil in a porous medium are governed by such factors as surfacc and interfacial tensions, viscosity of the oil, pore size configuration, and wetting characteristics of the medium. The knowledge of the part played by each of these factors is limited. If the oil is assumed to be distributed in droplets whose movement is restricted only by the pore openings, the following equation may be applied: ?P= 2r(1/r1-1/r2) .......(1) In this equation ?P is the pressure drop necessary to force an oil droplet through the construction, r is the oil-brine interfacial tension, r1 is the radius of curvature at the forward and smaller end of the deformed droplet, and r2 is the larger radius. This equation neglects the effects of viscosity, as a static or near static condition is assumed. It would apply equally well for a bubble of gas in liquid if r were taken as the surface tension of the liquid. This relation shows that droplets can be more easily displaced if the interfacial tension is decreased. The displacement of oil from the surface of a sand particle may also be considered from the basis of selective wetting assuming that the oil droplets are smaller than the pore constructions and that the sand surfaces may be considered as planes. A relation of the forces involved can be derived from Dupre's equation to give: Wos = row (1 +Cos?)........(2) where Wos = Work of adhesion between the sand and the oil row = Oil-water interfacial tension 0 = Contact angle ros = Oil-solid interfacial tension This equation would indicate that the displacement of oil from a sand surface is more readily obtained when the water-oil interfacial tension is reduced provided the contact angle remains constant. Evidently. however, the values of Cos 0 may vary along with the water-oil interfacial tension due to changes in the other surfaces of the system. The above theoretical considerations suggest that perhaps even the static behavior of a dispersed oil phase in a porous medium is considerably more complex than may be inferred by the simple systems

Jan 1, 1955

By Rajashekhar Marti, York R. Smith

Lithium is anticipated to be a key, strategic material in the clean technology economy. The majority of lithium reserves are contained in continental brines and sea water (>60%). Currently the most economical approach to recover lithium from such resources is through selective adsorption. Spinel type lithium manganese oxide and lithium titanium oxide have demonstrated to be excellent candidate materials (after de-lithiation). However, due to the small size of the powders, they have limited industrial application and require immobilization. In this work, we examine the application of novel manganese oxide nanowire composites for the extraction of lithium from dilute solutions. Manganese oxide nanowires were synthesized and simultaneously immobilized on diatomaceous earth via hydrothermal method. Lithium manganese oxide were then formed by solid-state reaction, de-lithiated and tested for lithium ion adsorption.

Mar 1, 2018

By Robert G. Pinkerton

Boyles Bros. Drilling Co. and Gibbons and Reed Company, both of Salt Lake City, Utah, have successfully combined into two joint ventures on the San Juan-Chama project of the U. S. Bureau of Reclamation. The Azotea Tunnel is 12.7 miles in length; the inlet portal is on the Navajo River in Archileta County, Colorado, and the outlet portal is in New Mexico, about 10 miles south of the state border. The Oso Tunnel lies immediately to the north of the Azotea Tunnel and discharges water directly into it. We are presently driving both tunnels with mechanical boring machines from their portals at the Navajo River. Both tunnels are circular, fully concrete lined. The Azotea Tunnel has a finished diameter of 10 ft. 11 inches while the Oso Tunnel is 8 ft 7 inches in diameter. Both tunnels are supported with circular, structural steel rings as required by ground conditions. In good ground rock bolts and steel roof plates are used.

Jan 1, 1967

By P. L. Sibrell

Previous research by the U.S. Bureau of Mines showed that autoclave cyanide leaching of used automobile exhaust catalysts for recovery of platinum group metals (PGM) was technically feasible. This work involves a more detailed investigation of the chemistry of the dissolution of PGM in cyanide solutions. The PGM species in solution identified by ultraviolet spectroscopy. Pt and Pd cyanide complexes were square were The planar in geometry, while the Rh complex was octahedral. The rate of dissolution of the PGM was also investigated using a rotating disk technique. Dissolution rates increased in the order of Rh, pt, and Pd, respectively.

Jan 1, 1994

By Stephen M. Voynick

Two hours driving time west of Denver, CO and 21 km (13 miles) north of Leadville, Bartlett Mountain rises 4,065 m (13,337 ft) high in central Colorado's Tenmile Range. Bartlett Mountain is one of Colorado's most recognizable peaks, especially when the late afternoon sun casts a surreal, reddish light across its most prominent feature - the Glory Hole. This is a gaping, half-mile-wide, 245-m- (800-ft-) deep crater. Created by subsidence from 60 years of massive underground mining, the Glory Hole is a monument to the Climax Mine, one of the great achievements in American mining and metallurgy. For most of this century, the name Climax has been synonymous with brilliant mining engineering, innovative metallurgical research and entrepreneurial promotion of a once-obscure metal - molybdenum. Climax overcame an array of economic, technological and social problems to become a model for underground development of massive deposits of low-grade ores. It is one of the few mines in the world where cumulative production is measured in the billions of dollars. The Climax mineralization was emplaced 30 million years ago. Magmatic intrusions formed a large, mineralized stockwork within the granite country rock of Bartlett Mountain. Associated hydrothermal events forced superheated metal- and quartz-rich solutions through fracture zones, silicifying the country rock and depositing huge amounts of molybdenite, or molybdenum disulfide. The mineralized rock, a light gray, finely crystalline, silicified granite, is laced throughout with blue-gray quartz veinlets containing molybdenite. Although the richest ores graded only about 1% molybdenite, the Bartlett Mountain deposit contained more than 2.7 Mt (3 million st) of elemental mo- lybdenum.

Jan 1, 1997

By Pedro Lucas Freitas

A elaboração de planos de mistura é feita em uma coqueria para uniformizar a qualidade das misturas. Um problema recorrente é a distribuição destes carvões nas dosadoras para serem misturados. A distribuição, no plano, destes carvões nas dosadoras é feita de forma manual, levando em consideração apenas o conhecimento do operador. A proposta é apresentar uma modelagem matemática de programação linear para resolver o problema da distribuição de carvões em dosadoras, segundo restrições de utilização das dosadoras dentro da faixa ótima, composição da mistura e uniformização das correias transportadoras, para reduzir sobrecarga nas linhas de dosadoras, com a finalidade de execução de um plano de mistura de carvões. Foram utilizados métodos de pesquisa operacional utilizando o algoritmo Simplex.

Aug 16, 2017

By Timo Toma

Hitherto flotation machines have by and large been operated and coaxed to best performance through the human endowments of sight and problem solving ability. A new device that measures accurately distinct froth characteristics on-line is now revealing fresh insights into the complexity of the froth removal, at the same time showing promise as a practical tool for the automation of stable control as well as flotation machine and flotation circuit performance optimization. The FrothMasterTM is introduced. Actual plant results are shown and discussed. A functional and practical leading edge solution to flotation machine control automation is presented.

Aug 25, 2002

By Louis A. Panek

INTRODUCTION AND SUMMARY With respect to the geomechanics aspects, the primary technical objectives in mining by an undercut-cave method are to achieve a controlled, sustained caving of the mineral body and to remove the fragmented ore with a minimum of dilution from surrounding unmineralized rock, while maintaining stability or control of the rock structure around the access openings. The structurally ideal ore body probably does not exist. If the rock mass is so weak as to cave on a short span, it may tend to be too sticky for easy drawing and handling, or create special problems in regard to support of the access openings. If the ore is strong, caving may be difficult and the caved fragments may be of such a large size as to require special equipment for transferring the ore from the caved zone. Given enough time and money to generate data and conduct trials, engineering and ingenuity can devise an appropriate combination of mine layout, sequence of extraction, and mechanical equipment to achieve a technically successful caving extraction operation to meet the foregoing requirements in many types of deposits. The large capital investment involved, however, reduces the freedom to make major changes once the mine development is well under- way, and the penalties for failure to accurately anticipate operating conditions militate against selecting any but the most obvious candidates for mining by an undercut-cave method. The demonstrated capability to extract large, deep, economically marginal deposits by this low-cost, high-volume method of mining provides an incentive to develop a rationale for predicting the cavability and stability characteristics of a deposit prior to mining, so that the undercut-cave method may be extended to a much wider range of mineral deposit characteristics. The ultimate goal is to establish as explicitly as possible the quantitative interrelationships between the measured rock-mass characteristics, the caving span, the size distribution of caved ore fragments, and the sizes and locations of stable access openings. Lacking an understanding of these relation- ships, a designer may readily change some factor in the wrong direction (e.g., excessively reduce the distance between the extraction level and the undercut to increase the convenience of operations for the undercutting crew, increasing the frequency of repairs to the extraction-level support system) or create unnecessary problems elsewhere in the system by introducing a design change that can achieve only minimal improvement in the factor of direct interest (e.g., unnecessarily complicate the ore-transfer system by changing the orientations of the openings, with- out succeeding in the objective of improving the ground support conditions). Although successful predesign is the prime objective, subsequent modifications in mine lay- out and sequence of extraction operations are inevitable. In developing the modified solution, systematic experimentation based on an understanding of the underlying structural relationships, coupled with monitoring measurements of selected diagnostic structural-behavior parameters, can achieve an acceptable solution in a minimum number of steps, which is far superior to the typical operational trial-and-error approach, in view of the cost of implementing each successive change. Since a drill-core sample of ore rock from a successful undercut-cave operation may exhibit a uniaxial crushing strength in excess of 100 MPa, the caving of such a rock mass is now commonly believed to be ascribable to the presence of discontinuities such as joints or fractures throughout the ore body. An essential part of the present investigation was therefore to characterize the natural discontinuities at each of the test sites by measuring their attitudes and spacings. The term "fracture" is used herein in a general sense to include any planar discontinuity without implication as to its suggested mode of origin. Most, but not all, of the fractures are properly termed joints. As a point of departure we may consider the possibility that the rock mass is transected by three families of joints, each family possessing a distinct orientation, such that parallelepipeds of intact rock are delineated by the jointing. Even if cementation is absent between adjoining parallelepipeds, the undercutting of the rock mass will not necessarily initiate sustained caving--owing to the all-around confinement, an arch may tend to stabilize over the undercut unless prevented from doing so by the failures of key blocks of intact rock. Thus, although the jointing can be assumed to weaken the rock mass, creating preferred directions of

Jan 1, 1981

By Nagarajan. D, Raja Rajan. K, Vijayakumar. T

Major bridges crossing mighty rivers must be constructed in flowing water. Constructing the sub-structure in water has been a challenging job for contractor. Special construction techniques with marine fleets to be adopted for waterfront construction. Enabling works like temporary piling platform and cofferdam used for pile and pile cap construction. Apart from this, enabling works like load out jetty to transport the materials from land to water; temporary walkway for access of workman to work location; temporary access bridge for construction vehicles movement; temporary liners for tower crane foundation; Concrete block to act as dead man anchor for barge movements were all required by the contractor for smooth functioning of site as per construction schedule. Investment in enabling works by contractor plays a significant role on profit margin of the project and of course with utmost safety. Design of enabling works for waterfront structures involves hydrological data like afflux, bathymetry survey, current force, scour depth and wave force to be taken cautiously for safe and economic design. Type of foundation and pile/well cap top level corresponding to water levels shall influence the construction scheme. Usage of geotechnical software like Wallap and Plaxis required for enabling work design to enhance the safety of the structure. Bathymetry and soil condition play a critical role in design and construction of enabling works. Water Discharge quantity in river along with water levels like low water level, high flood level, seasonal fluctuation of water levels has a great impact on design of enabling works. Establishing enabling works for waterfront construction near to an existing bridge is an additional challenge for the contractor. Along with design, constructing the enabling works in water requires special construction methodology and sequence of work. This paper shall provide insights on overview of design and construction of enabling works for waterfront construction.

Nov 1, 2022

By J. D. Miller, C. L. Lin, J. Dong

Nano clay mineral particles such as kaolinite — with primary particles typically smaller than 2 μm in size — can cause significant problems in flotation processes and tailings disposal, including the processing of Florida phosphate rock and Canadian oil sands. In this study, the consolidated state of flocculated kaolinite sediment was examined, and high-resolution X-ray microtomography (HRXMT) was applied to describe the structure of the consolidated sediment. Using this tomographic information, the complex geometry of the channel network structure for the consolidated flocs was established for the first time. With the establishment of the experimental channel network structure, permeabilities were estimated by flow simulation using the Lattice Boltzmann method. Results for kaolinite sediment with and without polymer are compared and discussed. Results for flocculated kaolinite sediment in a gravitational field are also presented and discussed. The results show that as polymer dosage increases, the permeability of flocculated kaolinite sediment increases, and as suspension pH increases, the permeability of flocculated kaolinite sediment decreases.

By Joe Welna, Lola Moussey

The Minnesota Department of Transportation (MnDOT) evaluated several concepts to minimize flooding of Trunk Highway 35W (TH35W) near downtown Minneapolis. A deep stormwater storage facility (SSF) was selected for final design. Given the constricted project footprint, open trench excavation construction methods were not feasible, and a top-down construction approach using diaphragm walls (d-walls) was utilized. The SSF is located near the edge of a glacial valley containing glacial and alluvial deposits including cobbles and boulders. Categorizing ground conditions was critical in assessing constructability of the SSF and determining project cost. Multiple phases of geotechnical investigation were conducted including geotechnical borings, geophysical surveys, and pump testing. Obstructions (including cobbles and boulders) were encountered at some of the borings conducted and therefore were anticipated to be encountered during construction. As part of development of a project risk register, it was decided by the Owner that the Contractor should assume no obstructions during d-wall construction, and obstructions encountered during construction would be paid using funds allocated in a project risk pool, which was informed by a Geotechnical Data Report (GDR) and Geotechnical Interpretive Report (GIR). The cells of the structure were successfully completed in 2022 with final completion anticipated for the fall of 2023.

Oct 31, 2023

By C Armstrong, B Wentzinger

Upstream embankment raises often represent the lowest cost option for increasing the capacity of tailings storage facilities (TSF), but also pose the highest stability risk due to constructing on top of previously deposited tailings.This paper presents an overview of key aspects in the geotechnical investigation and design of upstream raises and some recent lessons learnt from experience across a number of TSFs in Australia. A summary of recommended field investigation and laboratory testing methods is provided with a focus on collecting quality information for design purposes. A strong focus is given in developing an accurate assessment of pore water pressures, which, if not correctly understood can have disastrous consequences on tailings strength parameter interpretation and wall stability assessment in static and post-seismic conditions.The assessment of the contractive or dilative shearing behaviour of the tailings material and rigorous interpretation of design characteristic values are presented. Some comments on stability analysis options and proposed methodology are also provided.CITATION:Wentzinger, B and Armstrong, C, 2018. Lessons learnt in geotechnical investigation and stability analysis for upstream tailings storage facility raise design, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 333–348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By Glen R. Andersen

"Two of the greatest challenges we face in managing our aging infrastructure are to perform accurate condition assessments and to realistically predict the risk of non-action. The aim of this paper is to discuss common pitfalls we face in performing accurate condition assessments of our aging infrastructure using the case history of a recent near miss at the Lake Manatee Dam in Central Florida. The dam was placed into service in 1967 and was inspected every couple of years by dam safety engineers beginning in 1978. Although there was substantial and repeated evidence of a serious piping and internal erosion problem in each of these inspections, the problem was overlooked by most of the inspection teams. In 2012, the inspection team concluded that: “the Lake Manatee Reservoir Dam is well maintained and is in very good overall condition.” However, in 2013 a new team inspected the dam from an entirely different perspective, identified potentially serious conditions, performed an integration of the historical inspection data and concluded that: 1) the Lake Manatee Dam was in a severely distressed state; and, 2) without an immediate intervention there was a high risk of an uncontrolled release of the reservoir most likely following a large rainfall event and prolonged opening of the service spillway. This case history highlights human factors contributing to the near miss including group think and focusing on changes from prior inspections. The integration of historical inspection data is recommended for managing our aging infrastructure.INTRODUCTIONThe engineering analytical techniques most appropriate for assessing an aging infrastructure can be distinct from those used for the original design. To adequately manage our aging infrastructure it is necessary to change our perspective from anticipating failure mechanisms and designing to prevent them to assessing condition, detecting the presence of potential failure mechanisms, and assessing the potential risks. In many circumstances the failure mechanisms currently active may not have been anticipated by the original design team.We have developed a substantial body of experience in the design of our infrastructure. Full scale and laboratory testing coupled with the application of scientific principles to model behavior has led to many powerful design tools. The continued serviceability of our infrastructure as its elements reach their design lives stands as a legacy to our profession. However, under the sustained effect of limited resources for maintenance and rehabilitation parts of our infrastructure are in a highly deteriorated state. Unfortunately, the condition of some of these has not been properly assessed. This paper focuses on the Lake Manatee Dam in Central Florida and the process used to clearly identify its highly deteriorated state. While there are many factors that contributed to the lack of a proper assessment of its condition, the focus herein will be on human factors and in particular how “Group Think”, “Aversion to Bad News”, and “Condition Assessments Based on Changes to Prior Condition” may have contributed to not properly identifying the development of a serious failure mechanism."

Jan 1, 2017

By R Araya, G Harbort, D R. Seaman, L Huynh, P D. Munro

In today’s operating environment many conventional cleaner circuits struggle to produce final grade concentrate with acceptable levels of non-sulfide gangue and/or penalty elements. This is primarily due to poor selectivity and the entrainment of gangue, and is further exacerbated by the processing of lower grade ores with more complex mineralogy that require finer grinding for liberation. In new concentrators, the standard approach to cleaner circuit design is to define the number of stages of mechanical cells required to achieve the desired concentrate grade. Residence time is the primary factor to size cells and to determine the number of cells required to attain target recovery. While it is required for recovery, a bank of mechanical cells is not the ideal solution to maximise concentrate grade. Relatively coarse bubble size means slow flotation of fines, requiring long residence times. The combination of long residence times and no froth washing means higher entrainment as the pulp becomes more barren and froth stability decreases down a bank.In recent years, the Jameson Cell technology has been retrofitted into a number of concentrators around the world to solve both cleaner circuit capacity and concentrate grade issues. Jameson Cells have been installed at the head of conventional cleaner circuits to produce final grade concentrate in a single step of flotation using a single cell (referred to here as ‘cleaner scalping’ duty). The experience gained from these installations has provided the platform for the design of improved and simpler cleaner circuits that will perform better and be more robust to operate. This paper analyses traditional cleaner circuit designs and explains the philosophy behind new hybrid cleaner circuits, which use Jameson Cells to produce final concentrate and mechanical cells for a ‘cleaner scavenger’ duty. The advantages of the new cleaner circuit design are demonstrated by a case study from an operating plant. Engineering studies show that the better metallurgical performance can be achieved with less equipment than conventional cleaning designs, reducing capital cost, operating cost, and with more than 30 per cent energy savings.Finally, the paper describes simple modifications to the standard laboratory flotation test procedures which accurately simulate this new cleaner circuit using routine equipment.CITATION:Huynh, L, Araya, R, Seaman, D R, Harbort, G and Munro, P D, 2014. Improved cleaner circuit design for better performance using the Jameson Cell, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 141–152 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

"This model specification includes sample text shown in normal font with commentary in italics. The commentary is intended to highlight project-specific items the specification writer should consider during development of the specification. In some sections, typical values are presented to indicate common practice, and these values may be changed to reflect project-specific requirements. The commentary should be removed before using the specification for a project. 1. SCOPE The work consists of designing, furnishing, installing, and testing helical piles used to support foundation loads (compression, tension and lateral), and any ancillary materials (e.g., load transfer devices, etc.) according to the project plans provided and these specifications. Unless otherwise noted, the installing contractor shall provide all labor, tools, equipment and materials necessary to install the required piles. The parties referred to in this specification are as follows: • The Owner is the property owner. • The Owner’s representative is the individual or firm hired by the Owner to design and oversee the overall project. • The pile designer is the individual or firm generally hired by the installing contractor to design the helical piles. • Installing contractor installs and tests (if necessary) the helical piles, and possibly tasks associated with the project. It is important to clearly define the roles and responsibilities of every party on each project to promote good communication and reduce potential for contractual misunderstandings. Different types of contractual vehicles (design-build, value engineering, etc.) require different roles and responsibilities for the various parties, which should be considered in specification development. The Owner will provide suitable access to the construction site for the installing contractor’s personnel and equipment. Unless specifically noted otherwise in the contract documents, the Owner will remove and replace any structures, utilities, pavements, landscaping or other surficial improvements in the work area as necessary to facilitate the work. The Owner will be responsible for overall construction oversight to minimize potential for developing unsafe conditions. The work may include post-construction monitoring of pile performance if required by the Owner or the pile designer to confirm performance of the piles subsequent to their installation. The work may also include installation of additional piles if the initial installation does not meet specified capacity or performance requirements. Responsibility for providing subsurface investigation shall be addressed in the bid documents. The Owner is responsible for providing to the installing contractor all available subsurface soils, rock and groundwater information and geotechnical testing data."

Jan 1, 2015

By Eckl, Martin, Stefan Lemke, Martin Londschien

"Tunnels are built with a design life expectancy of over 100 years. One key component of such a design is the waterproofing system, which must reliably fulfil its function during the whole service lifetime of the tunnel structure. This paper deals with the determination of test criteria for the durability assessment of geosynthetic products in tunnel sealing systems. Hereby the understanding of the individual aging processes is crucial along with the long-term experience with these materials to ensure the transfer of the laboratory results and performance to site practice (test calibration) and vice versa. To verify the results of the new test procedure the material properties of geosynthetic products samples removed from older tunnels are investigated. Based on the presented results of the still ongoing research programs some preliminary conclusion regarding the updating of regulations for tunnel sealing systems are given. INTRODUCTION Watertightness is directly related to the durability and serviceability of the concrete lining. Therefore, modern traffic tunnels and shafts (Figure 1) are generally protected against mountain/ground water and water penetrating through rock fissures by a sealing system, for example with a loose-laid polymeric sheet membrane. Hereby the waterproofing sealing systems must be reliably fulfilling their function during the whole service life of the tunnel structure, regularly of more than 100 years. In consequence, the quality and lifetime performance of the waterproofing materials—beside the correct professional and careful installation in a tunnel infrastructure, is of great importance. The challenge for the industry, owners, operators and designers is ultimately the development of qualification testing and requirements (acceptance criteria) for products to ensure the design lifetime performance. Hereby the qualification procedure is seen as a routine integrated in standards, norms or guidelines, wherein test procedures should cover typical environments for the specific application fields. Polymeric synthetic raw materials are increasingly used in products with long service lifetimes (e.g. in injections, gaskets, waterbars, spray-applied and sheet waterproofing membranes). During service they are subjected to chemical (e.g. oxidation processes) and physical (e.g. changes in morphology) influences from the environment, which affect their mechanical properties—and they age. Hereby organic materials are more affected than inorganic materials. Also, polymers show strongly temperature-dependent properties compared with other construction materials. However, their long-term aging behavior is not given per se and has to be explored extensively by suitable tests, which simulate—under accelerated processes—real exposures and loads. Hereby the understanding of the individual aging processes is crucial along with the long-term experience with these materials to ensure the transfer of the laboratory results and performance to site practice (test calibration) and vice versa."

Jan 1, 2016