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By P. Roghanchi

The Rock Mass Rating (RMR) system is an internationally recognized classification system that can be used for preliminary ground control design. The RMR system assigns quantifiable values to predefined classified parameters of a rock mass. Assigning a single value rather than a range to each parameter is a source of uncertainty, however, assigning a single value can be useful for further studies related to RMR ratings. Fuzzy systems are being used in an increasing number of application areas where linguistic rules are used to describe the system. In past decades, fuzzy systems have been successfully used in geotechnical and mining engineering problems to cope with uncertain data as well as with vagueness. In such scenarios, linguistic rules and rating-based classification of rock masses have always been questionable. The objective of this study is to apply fuzzy set theory to the RMR classification system. The fuzzy system proposed in this study is specified for weak and very weak rock masses (RMR<50) based on data collected from Nevada gold mines where 68% of RMR data is in the ?poor? and ?very poor? classes. In this approach, a Mamdani fuzzy algorithm has been constructed to evaluate basic RMR89 rating for the ?wet condition.? Comparison between basic RMR89 and fuzzy RMR shows the fuzzy RMR system is valid to predict RMR from the discrete rating of each input parameter.

Feb 27, 2013

By P. M. Prasad

Off-grade molybdenite concentrates, mainly derived from secondary sources as by-products of the processing of copper, uranium and tungsten ores, do not satisfy the purity requirements (percent MoS2) for the production of molybdenum bearing products. This investigation is a continuation of a successful effort to refine a low-grade molybdenite concentrate to prepare a high-grade MoS2 using a mixed acid (HF + HCl) leach procedure. Specifically, this investigation is concerned with an understanding of the separation chemistry underlying the removal of the oxide/silicate gangue and the base-metal sulfide associations present in the low-grade molybdenite by their selective dissolution in the two acids. Experiments were conducted on an off-grade concentrate containing 42.6% Mo. Results of the controlled dissolution tests indicate that both HCl and HF are suitable for the removal of the associated alumina and both work well for iron, nickel and copper. However, HF was found to be the most effective for dissolving silica/silicate and magnesia. An attempt was made to rank the leaching efficiencies of the acids used singly, sequentially or in a mixed mode. Scale-up (300 to 2,000 g) experiments were conducted to validate this approach. Excellent purification of the concentrate was possible by processing the off-grade concentrate with 10% HCl plus 15% HF at 363 K for 7.2 ks in open polypropylene reactors with internal stirring. These conditions leached practically all of the oxide and silicate gangue and 96% of the metallic impurities. Starting from the low-grade molybdenite concentrate (42.6% Mo; 71.1% MoS2) it was found feasible to obtain a refined product containing 97.8% MoS2, which is suitable for industrial use.

Jan 1, 2007

By M. Javier

Mining, waste is growing problem both physical accumulation and increasing toxic uncertainties it presents in the long run. Its value ?zero? is strictly calculated by economy. This mining model begs the question: What is the value of waste & what does it represent to the mining industry? Waste is widely accepted as a ?by product? generated as a consequences of the mining process. The abundant waste accumulation affects society, as receptor, in many ways and the waste piles of materials has no use and no destiny. In reality, this waste is monument of imperfection of the extractive industries worldwide. Our planet is finite and has strict limitations, which mining has traditionally ignored. It is time to design a new system, in which clearly, waste design must be integrated in whole mining process; it has no room to postpone. This paper presents a concept in waste design by which toxic mining waste not only can be rendered inert but also act as nutrient to help balance the ecosystems. This concept calls for extractive industries to pursue EQUILIBRIUM with nature (Geomimic). Also, this concept offers countless gains and opportunities fro the industry and by converting liabilities into assets; mining engineers become the managers and stewards of nature. Also, waste design offers new solutions for proper and sustainable waste management of the mining industry.

Jan 1, 2011

By R. C. Milici

Historical production data and reserve decline rates can be used both to predict future coal production rates and to estimate when the reserve will be depleted. Reserve estimates inferred herein from historical production data and decline rates are commonly lower than estimates made from geologic data. The latter include significant amounts of lower quality (deeper, thinner, higher sub) coal which may be mined when the better deposits are depleted.

Feb 24, 1997

By J. E. Kogel

Industrial minerals play a central and dual role in the sustainable development (SD) of natural resources. Over the past decade the mining industry has increasingly focused on sustainably extracting and processing industrial minerals. This trend has been driven by higher energy costs, diminishing water resources and sensitivity towards environmental stewardship. Industrial minerals have been used throughout human history as low cost, naturally occurring, materials. Today they are critical components of recycled packaging, energy efficient building materials, light weight paper coatings, and other products critical to the responsible utilization of global resources. As industrial minerals become more widely used in ?green? products, mining companies have established best practices for the sustainable management of industrial minerals mining and processing. These management practices include reducing energy consumption, minimizing water usage, increasing waste recovery through recycling and process optimization, and maximizing the amount of ore extracted per acre of disturbed land. With the commitment to SD principles, quantitative methods for objectively measuring SD performance have become increasingly important. Measuring sustainability impact is a valuable tool for effectively applying SD principles and for making choices that balance sustainable development against other business objectives. SUSTAINABLE DEVELOPMENT AND MINING Sustainable development is a term that has become a common part of our lexicon; however, it has multiple meanings and interpretations leading to a sometimes confusing and contradictory array of definitions. The absence of a single, precise definition reflects the fact that SD is a broad concept or paradigm that offers guiding principles as opposed to a specific set of criteria or regulations enforceable by government or other oversight agencies. While a principle based conceptual approach allows businesses to broadly apply SD practices that are tailored to their specific situation, it has also led the public to sometimes view voluntary corporate SD programs with a degree of skepticism (Walker and Howard 2002). This is particularly true in the mining industry. One reason for this skepticism is that the relationship between SD and mining is misunderstood and to many, sustainably developing non-renewable mineral resources is a contradiction (Rajaram et al. 2005). However, this view takes a very narrow interpretation of the tenets of SD. The second is that mining carries a legacy of poor environmental stewardship that does not accurately reflect current corporate environmental practices Many minerals companies have adopted the Brundtland Comission?s definition of SD (United Nations 1987): ?? development that meets the needs of the present without compromising the ability of future generations to meet their own needs?. This definition is very broad and can be interpreted in a number of ways. It provides a general context for sustainable development and is not intended to provide detailed guidelines addressing specific aspects of sustainable development. To fill this gap the following SD principles were drafted by the international minerals community in 2003 (ICMM 2003): 1. Implement and maintain ethical business practices and sound systems of corporate governance. 2. Integrate sustainable development considerations within the corporate decision-making process. 3. Uphold fundamental human rights and respect cultures, customs and values in dealings with employees and others who are affected by our activities. 4. Implement risk management strategies based on valid data and sound science. 5. Seek continual improvement of our health and safety performance. 6. Seek continual improvement of our environmental performance. 7. Contribute to conservation of biodiversity and integrated approaches to land use planning. 8. Facilitate and encourage responsible product design, use, re-use, recycling and disposal of our products. 9. Contribute to the social, economic and institutional development of the communities in which we operate. 10. Implement effective and transparent engagement, communication and independently verified reporting arrangements with our stakeholders. These guidelines insure that SD concepts are applied equally across the industry while setting a clear performance standard and benchmark against which to evaluate success. By adopting these principles and issuing the Milos Statement (http://www.sdimi.org/milos_decl_October%206_2003.pdf), which provides a more detailed vision for integrating SD into everyday business operations, the minerals industry has embraced SD as a core corporate value. The unifying and holistic approach embodied in SD principles impacts the entire mine to market life cycle and addresses the economic, environmental and social consequences of mining. INDUSTRIAL MINERALS The world economy relies heavily on minerals; they are essential to economic prosperity and the quality of life. Industrial minerals are non-metallic, non-fuel minerals that provide the raw materials for a vast range of products used in most every aspect of daily life. They are mined and processed worldwide and they span the spectrum from relatively low value, high volume commodities (e.g. common clay, crushed stone) that are usually mined locally to high value, low volume specialty materials that are sourced from unique one of a kind deposits (e.g. barite, talc, mica). High volume commodity mining operations are often located near the end use market which, in most cases, means areas of high population density where construction and other urban activities drive demand. In these situations the strict adherence to SD principles is particularly critical as these are highly visible operations that must meet the public?s demand for good corporate citizenship. These operations are similar to chemical or other manufacturing facilities that operate near population centers. In contrast, some mining operations are located in remote but environmentally sensitive regions of the globe where the pressure to mine sustainably is driven by the need to preserve habitats and other

Jan 1, 2009

By William Gleason

"In a time that seems to be dominated with nothing but bad news coming from the mining industry, there is a success story that has been quietly happening in Southwestern Wyoming for more than 60 years, and it is one that is likely to continue for many decades to come.Beneath the wind swept high desert plains of Sweetwater County, WY, about 32 km (20 miles) west of Green River, lies the Green River Basin where five companies, including Tata Chemicals North America (TCNA), are mining the world’s largest known deposit of trona and, in turn, are collectively producing 15.3 Mt/a (17 million stpy) of soda ash.“We have a long-term growth story that has been, and will continue to be a steady earner for many years to come,” said J. Martin Keighley, managing director of TCNA who has been in charge of the mine, formerly known as General Chemical Industrial Products Inc., for Tata Chemicals for about three years.According to the U.S. Bureau of Land Management (BLM), Keighley is safe with his prediction of future success. The BLM estimates that there are enough reserves in the Green River Basin to last another 2,000 years. Currently, four trona beds in the Green River Basin are being mined and in all, there are 25 major trona beds that occur within the Wilkins Peak Member of the Upper Eocene Age Green River Formation. The trona deposit as a whole covers about 2,500 km2 (1,000 sq miles) within the Green River Basin.And imagine, this economic mainstay in the region was discovered accidently.Prior to 1948, soda ash, the salable commodity that comes from trona and is used in a host of products including glass and detergent, was produced synthetically. In 1938, an oil and gas exploration team working in the Green River Basin came away with a find that would change the soda ash industry and the physical and employment landscape of southwestern Wyoming forever. Within 10 years, the communities of Green River and Rock Springs, which were built largely on the back of coal mining and railroads, had another commodity beneath their feet."

Jul 1, 2016

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 Jafar Khademi Hamidi

The Zagros long tunnel is one of the main components of Sirvan water transfer project in western Iran. It is approximately 48 km in length and consisted of two lots. The second 26 km lot of this tunnel is under construction by a 6.73 m diameter double shield (DS) TBM. The tunnel passes through several formations with wide range rock mass qualities. During the tunnel alignment, changes in rock quality were highly frequent from poor to very good. The encountered geological conditions required TBM operation to change frequently from hard rock to soft, dry to flowing, sticky to nonsticky ground (and vice versa), more often than expected. In the course of tunneling, the machine has encountered nearly many adverse geologic conditions. The most important problems have been sudden high volume water inflow into the tunnel, sticky ground, and gas seepage, all of which resulted in reduced TBM advance rates. This study will high-light two difficult ground conditions including large water ingress and sticky ground and also the related problems encountered by the TBM along 8 km of excavated tunnel. In sticky grounds, cleaning of the clogged cutter head caused many delays and contributed to additional downtime. Application of some operational modifications, including decreased TBM thrust showed satisfactory results in such cases. While reduced thrust resulted in reduced penetration rate, but the overall TBM advance was greatly improved by the increase utilization rate and elimination of down time related to cleaning of the head. To cope with high water inflow, application of preventive measures such as pre-grouting has proved to be a more efficientsolution. The sealing of ground water inflow also decreased seepage of dangerous H2S gas and other chemicals such as hydrocarbons accompanying the groundwater.

By Bob Rautenberg

The Construction of Tunnel and Edison Force Mains contract involves the installation of two new force mains to provide a redundant means for sewage conveyance from Middlesex County Utility Authority?s (MCUA) Edison Pump Station on the northern shore of the Raritan River to the Central Wastewater Treatment Plant on the southern shore. The force mains will be installed in a 1,192 m (3,910 lineal foot) long tunnel with a 4.09 m (13&apos;-5&apos;) inside diameter, fully gasketed precast concrete segmental lining, which is to be tunneled underneath the Raritan River utilizing an Earth Pressure Balance TBM. The tunnel is anticipated to encounter flowing soils near and beneath the river. Two new 60-inch diameter Centrifugal Cast Fiberglass Reinforced Polymer Mortar force mains will be installed within the tunnel leaving an open utility corridor above the force mains for future consideration. The project also includes the design and construction of two slurry wall shafts with associated piping. The paper will provide an overview of design and provide a case history of the construction of the tunnel and highlights of the construction methods implemented to date.

By V. Rajagopal

Corrosion and abrasion properties of a series of chromium-containing cast iron balls with Cr contents ranging from 0 to 29% was evaluated and compared with austenitic stainless steel and mild steel balls. Marked ball wear tests were performed on artificial ore samples consisting of 95% quartzite with either 5% pyrrhotite or 5% chalcopyrite under a nitrogen or oxygen atmosphere. The electrochemical mechanism was investigated by correlating the corrosive wear with the corrosion currents obtained from potentiodynamic polarization curves under abrasion. An offset in their electrochemical activities was observed somewhere between 16 and 26% Cr. In fact, 26 and 29% Cr cast irons showed an excellent corrosion resistance approaching that of austenitic stainless steel. Flotation recoveries were estimated on a 95% quartzite + 5% pyrrhotite sample ground with various cast iron ball materials under an oxygen or nitrogen atmosphere. Electrochemical results are found to be in good agreement with corrosive wear obtained from marked ball wear test and with flotation results.

Jan 1, 1991

By N. Loganathan, Tan Boon Tee, Joe O’Carroll, Richard Flanagan

In recent years, tunnelling activities in Singapore have increased considerably with the construction of extensions to the existing sub-surface transport system, a deep tunnel sewerage disposal system, and tunnels for the laying power cables and other utilities. These tunnels are excavated through urban areas, adjacent to high-rise buildings, depressed road structures, beneath other tunnels, and buried services. Earth pressure balance (EPB) tunnel boring machines (TBM) have been used extensively in Singapore with great success. The risk associated with soft ground tunnelling, including tunnelling through Old Alluvium, can be minimized with an understanding of the geology, geotechnical parameters, and the tunnelling-induced behaviour of Old Alluvium (OA The purpose of this paper is to present some design and construction aspects of EPB TBM tunnelling through Old Alluvium.

Jan 1, 2005

By P. Zhang

A multiyear, comprehensive study of flotation reagents used in phosphate beneficiation was conducted. The study involved the evaluation of pure fatty acid compounds, comparison of various anionic collectors and testing of iso-acids. Various C12 to C22 fatty acids were tested as Florida phosphate collectors. The saturated fatty acids were found to be very poor collectors when using the standard conditioning procedure, whereas the unsaturated C16 to C22 fatty acids showed fair to good phosphate collecting ability. The C18 fatty acids oleic, impure oleic and linoleic and the C20 eicosenoic acid were shown to be the best phosphate collectors. The best flotation results were obtained using Liqro GA tall oil and oleic acid. Four isostearic/iso oleic acid type fatty acid collectors were compared with a commercial grade oleic acid and with Liqro GA tall oil as phosphate collectors using standard laboratory conditioning and flotation procedures. The most selective collector evaluated was Century 1108, a high isostearic acid-type reagent. However, it was concluded that this excellent-performing reagent was too expensive for commercial use. Overall, the most promising reagent was probably Century MO-5. This collector is essentially an iso-oleic acid/stearic acid mixture (not isostearic acid), and it costs much less. This program laid a sound foundation for developing single collector, all anionic flotation processes.

Jan 1, 2009

By I. G. Gonçalves

For most industrial minerals, the color is directly associated with economic value. In terms of physics, the principal property that defines the term ?color? is the intensity of light reflected (or transmitted) by an object over the visible band, comprehended between 400 and 700 nm. This reflectance spectrum serves as the starting point for a variety of color-describing factors, the most common in the mineral industry being the brightness (TAPPI, 1977 and 1986) and the L*a*b* system (HunterLab, 2008). Quality specifications for mineral products are usually based on these colorimetric parameters. This market is becoming increasingly more selective and demanding over the quality of raw materials and alongside the traditionally controlled characteristics, such as particle size distribution and chemical composition, a trend exists towards the establishment of increasingly more strict specifications for the optical properties of these materials. This is due to the fact that most plants consuming these industrial minerals incorporate them into products in which the visual appearance is controlled. For these plants, most of them being the manufacturers of plastics, paper, paints, and ceramics, variations in the color of mineral materials result in difficulties to achieve the right color in the final product. Therefore, these plants set strict specifications for colorimetric parameters such as whiteness and yellowness, as well as colorimetric coordinates like L*, a*, and b*. For the manufacturer of industrial minerals, this translates into difficulties simply because many of these parameters are usually alien to the tradition of the mining industry. The main quality parameter in the kaolin industry is brightness, which is a weighted average of reflectance values over the range of 400-510 nm (TAPPI, 1977). Due to the lack of a better property, producers tend to use brightness to also assess the quality of the in situ ore and along the processing operations. However, the unprocessed kaolin is often accompanied by ?contaminant? minerals. For Brazilian kaolins, which are the object of this study, the most important contaminants are hematite (Fe2O3), goethite (FeOOH), and anatase (TiO2). Each of these contaminant minerals has a distinct color and behaves differently during the processing of the kaolin ore. Hematite and goethite in particular are particularly strong pigmenting agents and at concentrations as low as 100 ppm they can make the difference between a high-quality white pigment product for paper coating and waste material. As each Fe-bearing contaminant has a different color and responds differently to processing operations (for example, magnetic separation, chemical bleaching, selective flocculation, and/or flotation in the case of kaolin), the in situ brightness tends to show a poor correlation with the brightness of the final product. Brightness measurements are sometimes complemented with X-Ray Fluorescence (XRF) analysis of Fe and Ti, but the total oxide content provided by XRF is also poorly correlated with product quality because Fe may be in the form of goethite, hematite, or inside the crystalline structure of kaolinite. Thus, a more robust technique capable of distinguishing each mineral phase is desirable. Diffuse reflectance spectroscopy has been used to analyze iron oxide/hydroxide content both qualitatively (Torrent and Barrón, 2003; Liu et al., 2011) and quantitatively (Jiet al., 2002 and 2006). These authors correlate slopes and inflection points at characteristic absorption bands with oxide/hydroxide content in natural soils. The approach presented here involves the extensive use of the Kubelka-Munk (K-M) theory, which has been used for color matching (Schabbachet al., 2009 and 2011) and particle size determination (Otsuka, 2004) in a simplified version. Unfortunately, the scattering constant S is very difficult to measure for dry powders, because the equations require a thin layer of material. Attempts have been made (Gonçalves and Petter, 2007, and Gonçalves, 2009) but the experimental errors tend to be high. Thus, this paper aims to develop a tool for the quantification of contaminant minerals in kaolin based on the K-M theory without resorting to measurements over thin layers. This tool is based on a new two-constant approach, which takes into account differences in scattering between materials over the whole measured spectrum. The experimental dataset consists of the reflectance spectra of mixtures between a bleached kaolin and synthetic Fe pigments.

Feb 27, 2013

By K. L. Lownie

For research and test data to serve a useful purpose, it is essential that it be derived from some known standard test procedure that allows for comparative analysis as well as independent replication and verification. Fan performance data provided by manufacturers is not absolute, and is influenced by the geometry of the test installation. For these reasons, fan test standards have been prepared in order to establish a clearly defined test procedure that allows for comparison of different fan designs, and also allows for the independent verification of test data. Internationally recognized Standards such as BS848, ISO5801, and AMCA 210 etc. are highly prescriptive, and precisely specify test duct configurations, measurement procedures, measurement planes and instrumentation to be used. Provided the laboratory tests are conducted strictly in accordance with the relevant Standard, the performance data will accurately reflect fan performance within the appropriate tolerances for efficiency, pressure and flow when tested in the defined configuration. Major differences in performance exist between a fan tested in accordance with a Fan Test Standard, and an identical fan installed in a mine ventilation system. The aerodynamic performance of any fan will be influenced by the quality of the fan manufacture, the flow system within which it is operating, the location of measurement planes, and the system stability. The flow distributions present in a standardized Laboratory test are unlikely to be repeated in mine ventilation systems, and this will also disadvantage fan performance. Unless the fan supplier takes all of these influences into account, there will an inevitable reduction in fan aerodynamic performance, and the end user will experience a shortfall in expected flow through the mine. The effect on fan performance can range from minor inconvenience to catastrophic fan failure resulting in major rectification costs and significant loss of mine production.

Jan 1, 2009

By David Belknap, Clay Haynes, David Egger

Rehabilitation challenges were met nearly two months ahead of contract schedule for the Design-Build, Fast Track Scituate Aqueduct & Tunnel project in Cranston, Rhode Island. The aqueduct and tunnel were built in the 1920s and consisted of three sections—a 2.3 m diameter reinforced concrete section that extends approximately305 m before it transitions to a horseshoe-shaped 2.3 m wide by 2.1 m high cast-in-place concrete tunnel that continues for approximately 5.3 km until it transitions back to a 2.3 m circular section that extends approximately 1.9 km to the end of this project. Major repairs were required to assure sustained operation of this water supply tunnel.

Jan 1, 2005

By S. Möllerherm, E. Drüppel

"The development of indicators to assess the sustainability of mineral raw materials operations is amajor task with respect to its actuality and difficulty. This holds true even more when dealing withenvironmental indicators.The use of existing environmental indicators in the mineral raw materials industry leads to false orat least distorted results. Therefore the Institute of Mining Engineering I from the RWTH AachenUniversity developed indicators and an assessment system for the mineral raw materials industryon operation, company and sector level on behalf of the Federal Ministry of Economics and Labour(Bundesministerium für Wirtschaft und Arbeit, BMWA) and the Federal Institute for Geosciencesand Natural Resources (Bundesanstalt für Geowissenschaften und Rohstoffe, BGR).In total 30 indicators were defined and designed to assess the performance of the mineral rawmaterials industry in terms of sustainable development, 10 indicators for each pillar (economical,ecological and social pillar).The following paper describes some of the results focussing on the development of environmentalindicators. These had to be adapted or completely new designed in order to match the specificcharacteristics of the mineral raw materials industry."

Jan 1, 2005

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007

By J. F. Lupo

Heap and valley leach operations rely on solution collection piping placed within the heap to enhance both solution recovery and to assist overall solution management. The most common piping used in leaching operations is solid or perforated High Density Polyethylene (HDPE) pipe and Corrugated Polyethylene pipe (CPE). These pipes are widely used because of their low cost, ease of installation, durability, and flexibility. The typical recommended maximum design depth of burial for HDPE and CPE pipes is on the order of 30 meters (100 feet). However, ore heap heights at many facilities exceed 30 meters and some are now approaching 180 meters (600 feet) in height. At very high ore heap heights, the stability and performance of HDPE and CPE pipes becomes a critical issue for leaching facility design and operation. Failure of solution collection piping can lead to poor solution recovery, high hydraulic heads on the liner system, and in some cases, unstable ore slopes due to high solution pressures near slopes. This paper presents a review of methods that have traditionally been used to evaluate pipe stability under high normal loads. A common shortcoming of these methods is the inability to account for beneficial effects of ore arching around pipes and the time-dependent creep (stress relief) behavior of polyethylene (PE) materials. A new analytical approach is developed and presented which includes the effects of ore arching around pipes and creep of PE materials. The results of the new approach show that PE pipes will deform under high heap loads, but can remain stable and functional. Pipe stability is shown to be dependent on the type of pipe backfill and initial backfill compaction. The new approach represents a useful tool for designing applications for PE pipe under high normal loads.

Jan 1, 2001

By I. Tsolas

This paper presents the use of non-parametric approach (i.e., data envelopment analysis, DEA) for the development of environmental sustainability indicators in mineral processing using environmental, economic and/or integrated indicators (i.e., indicators that interrelate two dimensions of sustainability). A case study based on real publicly available data is presented to illustrate how the proposed approach can be implemented in practice. The merit of this approach, which is based on the productive efficiency framework, is that it provides environmental sustainability indicators that can be used internally for benchmarking purposes and externally for sustainability reporting.

Jan 1, 2008

By Jeremy Theys

The Sacramento Regional County Sanitation District (SRCSD) is improving the sewer system in the Natomas area of Sacramento, CA. The Upper Northwest Interceptor (UNWI) system is an ongoing series of tunnel pipeline projects that will provide sewer conveyance for all residents of northeast Sacramento County to the New Natomas Pumping Station, located North of downtown Sacramento, also in the city of Sacramento limits. The New Natomas Pumping Station then carries wastewater flowsto the Sacramento Regional Wastewater Treatment Plant in Elk Grove via the existing Lower Northwest Interceptor. The Joint Venture of Traylor Brothers, inc. and J.F. Shea (TSJV) were awarded the UNWI 1&2 project in late September, 2007. The planned 5.8 km (3.65 mile) construction route for UNWI 1&2 begins at the New Natomas Pump Station and runs north along the East Drainage Canal to the begin-ning of UNWI 3&4 at Bridgecross Drive. UNWI 1&2 includes approximately 5.8 km (19,240 feet) of 3.65 m (144 inch) inside diameter pipe using Earth Pressure Balance Tunneling Methods. The project also includes 16.76 m (55 feet) of 3.04 m (120-inch) diameter interceptor pipeline, twenty three access manholes spaced approximately 305 m (1,000 feet) apart along the alignment, a 2.13 m (84-inch) by 3.65 m (144-inch) transition structure, a 3.65 m (144-inch) by 3.04 m (120-inch) transition structure, and the connection of three existing sanitary sewer lines to the interceptor.