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By Jung-Joo Kim, Jong-Uk Kim, Turab H. Jafri, Han-Kyu Yoo

"INTRODUCTION Steel sets such as H-type and lattice girders are often installed in the tunnels before the hardening of shotcrete to ensure the stability of conventional tunnels in soft ground conditions. In practice, while designing the tunnels with the help of numerical analysis, steel sets are generally considered only as temporary support elements. Only a few studies propose the direct application of composite support in the tunnel design, based on large-scale experiments and numerical analysis. In order to assess the structural performance of the composite support consisting of shotcrete and steel sets, large-scale experiments were performed on two types of arch-shaped specimens by applying the combined effects of axial forces and bending moments. Based on the experimental results, numerical analysis was performed to assess the application of composite support in tunnel design. The crown settlement, axial forces, bending moments, and load distribution in the composite support were analyzed in the light of different structural patterns. LARGE-SCALE EXPERIMENTS USING COMPOSITE SUPPORT Preparation and Procedure of the Experiments The preparation setup as well as the organized procedure of the large-scale experiments using composite support is shown in Figure 1. An appropriate geometry of the specimens was selected by considering the standard cross-section of a two-lane highway tunnel in South Korea. Under the loading conditions meant to develop the axial forces and bending moments simultaneously, arch-shaped specimens were assembled with the ends of the specimens subtending a 60° arc angle at the center of the arc circle as shown in Figure 2. The fabrication of six specimens was completed in two groups based on the dimensions of steel sets, with the first group of three specimens being reinforced by H100 (No.1, No.2, No.3) and the other three by H125 (No.4, No.5, No.6). In order to reduce the voids on the boundary of the shotcrete and steel sets, concrete was casted over the steel sets instead of using shotcrete. The specimens were designed to incorporate the uniaxial compressive strength of 21 MPa. Shear keys and steel plates were installed at the ends of the specimens, so that shear failure could be avoided at the ends and the specimens could also be protected from detachment at the fixation. Translational and rotational movements at the ends of specimens were fixed."

Jan 1, 2016

By Wangzhi Zhou, Jian Xu, Jing Zhang, Xuecheng Gong, Mingsheng He, Guohua Xie

Graphite, which has a unique stack structure that enables a small friction coefficient, is used as one kind of the best hearth rolls to support and convey silicon steel strip in continuous annealing furnace. However, the buildup formation in/on the surface of carbon sleeve has always been a worldwide difficulty in the silicon steel industry. Based on the analysis of the microstructure, topography and composition of the buildups, combined with simulation experiments, the mechanism of forming buildups is discussed. The results show that buildups experience the process from nucleating to growing-up, and buildups are formed by nano liquid phase sintering (NLPS). Meanwhile, some countermeasures to reduce or prevent the formation of the buildups are proposed.

Mar 1, 2018

By Zibo An, Yong Hu, Hao Zhang, Hong Cao, Jun Xue, Zhen Luo

Phosphogypsum (PG) is a by-product of solid waste produced by the phosphate chemical industry. Owing to large emissions and massive storage issues, it causes a potential threat to our environment. Hereby, a method based on the precipitation and crystallization properties of calcium phosphate-magnesium ammonium phosphate (CP-MAP) followed by its adsorption on active solid waste powder is used as the main principle to treat PG harmlessly. The treatment process and its influencing factors for orthogonal experiments along with the associated environmental safety have been studied in detail. The results showed that this method could simultaneously remove soluble phosphorus and soluble fluorine from PG. When ACP, FA, HBM, and Ur were added to PG at a dosage of 3%, 13.5%, 0.04%, and 0.04%, respectively, the residual phosphate and fluoride contents was 0.061 mg/L and 0.856 mg/L respectively in the PG leaching solution. Compared to state-of-the-art approaches, this method exhibited higher efficiency in removing phosphate and fluoride. Most importantly, this method does not cause any secondary pollution in the process, thereby showing a novel application in large-scale industrial treatment.

Aug 29, 2022

By T. J. Neil, C. B. Manula, O&apos

This paper describes a simulation model developed to analyze truck haulage problems as they are found in the open pit mining and construction industries. The model, using a computer, cycles trucks between their assigned loading and discharge points over a measured haulage route. Required parameters for model operation include the number and type of operating trucks and loading units, maximum truck acceleration and velocity, a realistic vehicular deceleration rate, and the ratio of ore to total material loaded at each origin. Equipment performance characteristics, system profile characteristics, and service time distributions are also included. Records are kept of all waiting times at the loading and discharge points and of any truck interference on the haulroads (moving queues), and a current journal of ore and waste production is maintained. In the pursuit of reduced truck haulage costs, management is confronted with three particular problems in truck and shovel mines. 1) What is the best assignment of trucks to shovels in the system? 2) If new equipment is needed, which new shovels and trucks will operate most effectively in the system? 3) Are any physical changes in the haulage layout warranted to increase productivity? For small open-pit mines the answers to these questions may be obvious. However, for larger operations complex problems are encountered with production and system configuration relationships usually being unknown. The mining simulator discussed here was developed to aid management in evaluating alternative pit-haulage schemes to reduce the risk involved in the selection and assignment of equipment in open-pit truck and shovel mining systems. There are two fundamental differences between this model and other truck haulage simulators: one is a difference of degree, the other a difference of kind. This model can simulate more complex systems than previous models by allowing transportation of material from multiple mine faces to multiple mine destinations and by being readily adaptable to a wide variety of mine layouts. The second difference that characterizes the model is the standard simulation of truck movements. This technique enables each vehicle to perform according to its mechanical capabilities and the physical profile of the haul road. Among the similarities between other truck haulage simulators and this model are the recognition of the probabilistic nature of certain service times in the system and the use of a digital computer to operate the model. The computer inherits the staggering computational and bookkeeping work loads and provides a means for compressing the time scale by allowing several days' operations to be simulated in a matter of minutes. DISTRIBUTION SYSTEM Basic aspects of the system analyzed here may be brought into focus by referring to Fig. 1, a schematic of the typical open pit truck-shovel operation programmed into the simulation model. A single stage materials handling scheme is employed to transport both ore and waste. Loaded trucks are directed to a crusher or stockpile if ore is being mined, while overburden is conveyed to a waste dump. Each shovel has a given number of assigned trucks and has two associated haulage routes, one for waste and one for ore. Up to 5 shovels and as many as 10 trucks per shovel (or a total of 50 trucks) can be operated in the model. Essentially the model, using a computer, cycles trucks between their assigned shovels and the proper discharge points over measured haulage routes. Required input parameters for model operation include the number of shifts to be simulated, operating time per shift, number and type of operating trucks and shovels, maximum truck acceleration and velocity, a realistic vehicular deceleration rate, and the ratio of ore to total material loaded at each shovel. Equipment performance characteristics, system profile characteristics, and service time distributions are

Jan 1, 1968

By Y. Lahaye, O. Martinsson, B. I. Palsson

"Four main and three minor rare-earth-element (REE)-bearing minerals were identified and quantified in the Kiirunavaara apatite iron ore tailings using optical microscopy, an electron probe microanalyzer (EPMA) and a mineral liberation analyzer, and their chemical compositions were analyzed by the EPMA and laser ablation inductively coupled plasmamass spectrometry. REEs are shown to be contained in the minerals apatite, monazite, allanite, titanite, zircon, thorite and synchysite. In zircon, thorite and synchysite, they occurred in only trace amounts and contributed limited amounts to the total REE budget, and these are consequently of minor importance. Monazite occurred as inclusions in apatite and as free particles, 90 percent liberated. Allanite occurred to some degree in mixed grains with magnetite but also as free particles. Monazite mainly reported to the apatite concentrate, while allanite and titanite largely went to the tailings, the latter preferably to those fractions smaller than 38 µm. The amount of titanite in the finest tailings fraction was 2.3 weight percent, containing close to 1 percent REEs, with heavy rare earth elements (HREEs) making up 28 percent of the total REEs. However, a texturally distinct group of titanite grains showed an HREE/REE ratio of up to 67 percent. Furthermore, titanum dioxide analyses indicate that titanite is preferentially released into the tailings from the secondary magnetic separation step in the concentrator. Our data therefore suggest that titanite, occasionally enriched in HREEs, can be extracted from the processing stream and might thus be considered a new source for REEs at Kiirunavaara and similar deposits.IntroductionDeposits of apatite iron ores are the major source for iron in the European Union and are exploited by Luossavaara-Kiirunavaara AB (LKAB) in several mines in the Kiruna-Malmberget area in northern Sweden. Kiirunavaara is the largest of the apatite iron orebodies in Sweden, comprising more than 2 Gt of iron ore with 60 to 68 percent iron (Fe). At the end of 2015, the total accumulated production of crude ore from openpit and underground mining since the start of mining was 1,566 Mt, with ore reserves of 644 Mt grading 46.3 percent Fe (LKAB, 2016). The deposit defines a steeply dipping tabular body, approximately 6 km long and up to 180 m thick, extending at least 1,500 m below the surface. It is situated in the middle part of the Palaeoproterozoic Kiirunavaara Group of volcanic rocks and follows the contact between a thick pile of trachyandesitic lava and overlying pyroclastics (Martinsson, 2004)."

Jan 1, 2017

By Jagdish C. Agarwal

Although copper ranks very low in the order of abundance of elements in the crust of the earth, it has been one of the first metals utilized by mar, at his emergence from the Stone Age, about 10,000 years ago. Use of copper for weapons, tools, utensils and ornaments dates back to the twilight of history, 6,000-5,000 B.C. Native copper outcrops and the malleability of the metal explain its very early use by the cave-dwellers. The working, melting and extraction of copper from its minerals are among the oldest metallurgical achievements of the human race. The oldest complete smelting installations for the extraction of copper from its minerals, dated about the fourth millenium B.C., were recently discovered in the Timna Valley, Wadi Arabah, Israel. (1) The history of the developments of the extractive metallurgy of copper has been adequately reviewed recently. (2,3) The center of copper production migrated from the Eastern Mediterranean to Northern Europe (Mansfeld, Germany, Swansea, Wales) towards the end of the Middle Ages (1500 A.D.). The production of the metal was boosted tremendously in North America since the end of the nineteenth century (Fig. 1).

Jan 1, 1976

By S. Hamilton

Borates are essential to life, and to many products that are essential to an acceptable standard of living. They occur naturally in seawater at an average concentration of five milligrams of boron per liter. Fresh water lakes, rivers, streams and ground water generally have concentrations of about one milligram boron per liter. Borates are also present in soil at concentrations ranging from 0.1 to three milligrams of boron per kilogram. Because most of that boron is locked into insoluble minerals, clay or organic matter, boron deficiency is more widespread than boron enrichment. Borates evaporate into the atmosphere from seawater, rain, snow and hot springs. In rain and snow, natural boron concentrations range from 0.002 and 0.1 milligrams boron per liter. All told, boron moves through the atmosphere at a rate of 5 Mt to 7 Mt/a (5.5 million to 7.7 million stpy).

Jan 1, 2005

By V. Avzian Belozersky reg 453524, Vasily V. Lodeischikov, Adolf F. Panchenko, Til E. Vidusov, Olga D. Khmelnitskaya, Vladimir E. Dementyev

"Presently, there is a number of gold deposits which cannot be developed using the conventional technologies with acceptable economic indices due to low gold content, high depth of ore occurence and other conditions. For such ores, an innovation technology of underground gold leaching in the place of their occurrence is of special interest. The technology excludes ore mining and hoisting to the surface. This enables the production cost of 1 g of gold to be considerably reduced in comparison with conventional methods of gold recovery.The Maminskoye deposit oxidized ores were chosen as the subject of underground leaching because they are ideally suited for this purpose due to their composition and hydrological parameters. The ore reserves within the underground leaching block are 90, 000 t with 0.7 g/t average gold grade.An experimental system for underground leaching with a throughput of 15 cubic m solutions per hour was developed. A combined filtration-and-infiltration system of the ore massif development by holedrillingwhere pregnant solutions are air-lifted was worked out.The underground leaching flowsheet includes Au dissolution by chlorine-containing solutions, Au adsorption from solution onto active carbon, carbon concentrate ashing and calcine melting to produce Dore metal."

Jan 1, 2003

By C Zhang, G Si, J Oh, X Zhu

The presence of rock joints has a huge impact on the strength, deformability, and permeability of fractured rock masses by providing surfaces of weakness on which further deformation are more prone to occur, and by serving as the major channels of water flow due to low matrix permeability. In earlier studies, water flow-through rock joints is often assumed as laminar flow between two ideal smooth parallel plates, and the well-known cubic law was derived and widely used to characterise the hydraulic behaviour of rock joints. However, natural rock fractures are irregular and of spatially varied aperture. Thus, the concept of equivalent hydraulic aperture was introduced to modify the cubic law. Numerous works have been conducted on the relation between hydraulic aperture and mechanical aperture incorporating various geometrical parameters. The surface roughness is one of the most sensitive factors for water flow-through rock joints. The aperture distributions are irregular in natural roughed fractures relative to the parallel plates. Barton et al (1985) and Olsson and Barton (2001) incorporated the joint roughness coefficient JRC in evaluating hydraulic aperture and proposed an empirical equation based on fluid flow tests. However, their equations do not conform to the dimensional consistency. Many other researchers (Zimmerman and Bodvarsson, 1996; Xiong et al, 2011; Li et al, 2019) considered aperture distributions in their equations. But the aperture distributions change during shear was always neglected. The contact of rock joints also has a significant impact on the hydro-mechanical behaviour of rock joint, since fluid tends to flow-through a rough joint along connected channels while bypassing the contact obstacles with tortuosity. Nonetheless, previous research mostly considered joint roughness or aperture changes based on 2D joint profiles, while the contact and tortuosity based on 3D surfaces were often overlooked. Only a few works have been made on quantifying the effect of contact area on flow behaviour (Walsh, 1981; Zimmerman et al, 1992; Zimmerman and Bodvarsson, 1996; Yeo, 2001), and mostly ignored contact area change induced by shearing and the associated impact on flow behaviour. Summarily, the quantification of fracture geometry effects on water flow in single rock joints still needs further investigation, especially when considering coupled shear-flow processes. This paper, therefore, aims to study the impacts of contact area and aperture distributions of the single rock joint on the flow behaviour. The evolutions of contact area and aperture distributions induced by shear are considered. Then, an improved model for estimating the hydraulic aperture with the mechanical aperture incorporating the above factors is developed. Finally, a series of shear and shear-flow tests are conducted on artificial joint samples and the model performance is verified by comparing against the results of experimental tests.

Nov 29, 2022

By John Nunes, Frank R. Larson

Temperature-dependent functions of various ten-sile flour stress and fracture parameters were investigated on iron and low composition alloys of Fe-C, Fe-Cr, Fe-Mn, and Fe-Ni. Data were obtained over a range of test temperatures from 200" to -196"C at an initial strain rate of 0.01 min". It was found that the strain-hardening exponent, n, for the Fe-Ni alloys increased significantly at very low testing temperatures with increased alloy addition. Also, the stress and strain at fracture followed a predictable transitional type of behavior. The flour stress-temperature dependence was evaluated employing the relation: M where it is shown that composition can strongly influence the constant M. An empirical formula describing this effect is as follows: M = MI (equivalent at. pct Ni)-'" Some preliminay, tests were run on several commercial steels to test the generality of this relationship. One of the phenomenological explanations of the ductile-to-brittle transition encountered in bcc metals is based upon the difference in the temperature dependence of the flow and fracture stresses.' It states simply that the fracture stress is relatively insensitive to temperature and that the yield or flow stress rises rapidly with decreasing temperature so that, when the flow stress reaches the fracture stress, brittle fracture occurs without appreciable plastic deformation. This behavior is illustrated schematically in Fig. 1 where the ductile-to-brittle transition is shown to occur at two possible temperatures. The lowest temperature, TB, represents essentially completely brittle behavior while the higher temperature, TN, represents "notch" brittle behavior. Support for this theory is obtained when it is observed that fcc metals, which do not commonly have a ductile-to-brittle transition, also do not commonly exhibit any strong temperature de- pendence of the yield stress. This relationship of yield or flow stress behavior with the ductile-to-brittle transition has been generally observed for most metals representative of these two crystallo-graphic structures. One exception to this generalization appears in the case of tantalum where no apparent ductile-to-brittle transition has been observed. However, this may simply be an indication that this type of behavior is not directly related to the flow stress and that some other mechanism such as twinning must also be operative. A comparison of the typical temperature dependence of the yield stress of some representative metals is shown in Fig. 2. In the study of the temperature dependence of the strength of metallic materials, considerable ef-

Jan 1, 1963

By J. Petersen, T. Moyo, J. Dinga

The leaching of chalcopyrite in ferric sulfate media is notorious for its slow and inhibited kinetics. Different methods have been proposed to improve the kinetics, including the use of organic compounds as additives to the leaching media. In this study, the enhancing effect of methanol, ethanol, 1-propanol, and 2-propanol on the leaching of chalcopyrite in aerated acid ferric sulfate solutions using different reactor systems was investigated. The results revealed a clear improvement of copper dissolution by methanol and 1-propanol relative to tests with no additives under similar conditions. Operating a continuous-flow mini-column reactor yields surprisingly good results, potentially related to the maintaining of a consistent leaching micro-environment on the mineral surface. Scanning electron microscopy studies showed that the alcohols result in the removal of surface deposits formed during the anodic dissolution, potentially thus facilitating improved cathodic reduction of the ferric ion to drive the anodic dissolution.

Jan 1, 2023

By Tso-Min Shih, Ching-Hua Liu, Chung-Jen Lin, Hsi-Chiang Fang

This paper presented herein, describe the special design of an open type coal dust explosion apparatus and the laboratory works for investigating the effectiveness of the parameters on coal dust explosion and the prevention of the propagation of the coal dust explosion flame. Coal sample which were taken from the San-Ying collieries, were passed through the process of crushing ,grinding and screening to get the required particle size, ranged from 40 mesh to 200 mesh under size for testing purpose, the rock dust spreaded on the surface of coal dust and water mixed with coal dusts were employed for preventing the coal dust explosion and the propagation of the explosion flame.

Jan 1, 1991

By Anil K. Ray

This paper discusses in situ studies conducted at an Illinois Basin room-and-pillar coal mine to evaluate the performances of three different types of bolts under similar geologic conditions. The bolt types considered were the fully grouted passive rebar (FGPR), the resin-assisted mechanical anchor (RMAB), and the fully grouted tension rebar (FGTR). During the evaluations, the three types of bolts were installed in a single entry covering a span of three contiguous pillars with almost identical geologic conditions. The performances of the three types of bolts were investigated by instrumentting the bolts prior to installation as primary supports on cycle. Additional data on roof behavior was collected with extensometers and shear meters placed near the instrumented bolts. Excluding some time lapse right after installation, the performance evaluation of the three bolt systems was based on the data collected for over a year. Based on this study, it was found that the axial loads measured in the different bolt types did not show any identifiable patterns under the prevailing geological conditions at the mine. Therefore, the assumption that active bolts must be superior to passive ones is not always valid. Even though the studied mine did not have any thinly laminated, weak rocks in the immediate roof, the passive bolts performed as well as the active systems.

Jan 1, 2012

By Patrick R. Taylor

A novel method for Chemical Vapor Infiltration (CVI) using plasma technology is proposed, Plasma Enhanced CVI (PE-CVI). Due to the low rates at which CVI is currently performed, the use of plasma as a source of heat may be considered to be a faster and less expensive production method. Precursors fed in the hot region of the plasma gas are completely vaporized and forced by the same flow through a porous preform where it condenses as a new material. In this research, silica and methane where used as precursors to form SiC/on a / graphite felt (preform). To enhance the infiltration process, vacuum was used to increase the flow through the preform. Characterization of infiltrated graphite was perfontied using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). A uniform distribution of Sic was observed along the felt with only twenty minutes of infiltration process, yielding a 178% increment in weight.

Jan 1, 1997

By O. C. Blade

This report on the properties of motor fuels sold through service stations in the United States was made in accordance with a cooperative agreement between the American Petroleum Institute and the Bureau of Mines of the United States Department of the Interior. By agreement with the American Petroleum Institute, identification of the Items is confidential. It present's analytical data for 4,608 samples, representing the products of 101 companies. The samples were collected during December 1956, January and February 1957. As in previous surveys, the gasolines covered by this survey include those from both large and small suppliers. The data were obtained by laboratories of various refiners, motor manufacturers, and chemical companies and submitted to the Bureau of Mines for compilation. A list of the Notional Motor Gasoline Survey reports published during the post 10 years is given on page 5.

Jan 1, 1957

By W. J. Kingwell

Where the equipment, technique and materials are available for the construction of large diameter rock socketted piles, this is frequently the most economical and environmentally acceptable method of supporting very large concentrated foundation loads in geoglogically appropriate areas. This paper outlines the current approaches in Australia to design and installation of large diameter rock socketted piles. The equipment and procedures described generally reflect those developed or used by Vibro-Pile (Aust.), a company which, while installing the usual range of driven and bored piles, specializes in the design and construction of large diameter rock socketted piles and possesses special expertise in drilling in high strength rock. A high capacity crane attached drill for large diameter drilling in rock is briefly described. Discussed in detail are the construction techniques employed and structural and geomechanical design methods adopted.

Jan 1, 1989

By G. Britsianes, T. L. Joseph

THE reduction of a lump of iron ore is a complicated sequence of up to three reactions proceeding simultaneously in a gas-solid system. As the ore moves down the blast furnace into zones of higher temperature and higher reducing power, it is successively reduced through the three oxides of iron into metallic iron. The reduction process involves much more than chemical problems. Physical factors add to the complexity of the overall process. Under optimum conditions, reduction of the ore is completed at a level about one-half way down the blast furnace stock column. At this point, the ore undergoing reduction has attained a temperature of about 1000°C and has been in the furnace for about 6 hr. On the practical side, the behavior of the ore during smelting has been of great interest to operators. Unsatisfactory blast furnace operation on burdens containing magnetite ore or badly slagged sinter has often been attributed to poor re-ducibility. The question of reducibility has also been raised in formulating quality standards for agglomerates such as nodules, briquettes, and pellets. In the present investigation, the solid phases formed during reduction were studied as a step toward a better understanding of the overall process. Equilibrium Studies The iron-oxygen equilibrium diagram shown in Fig. 1 reveal; a number of facts pertinent to the gaseous reduction of iron ores. This diagram is from the work of Darken and Gurryl, 2 and represents a correlation of the best available data. Four solid phases may exist during the complete reduction of hematite to metallic iron. These are hematite (Fe2O3), magnetite (Fe3O4), wustite (FeO), and iron (Fe). The wustite phase is a solid solution which is not stable below 570°C. At this temperature the solid solution undergoes a eutectoid-type of decomposition into the phases, magnetite and iron. Thus above 570°C, the diagram dictates that a hematitic ore should pass through a four-phase sequence on reduction to metallic iron. Below 570°C, only hematite, magnetite, and iron should appear. Information on the iron-oxygen system has been derived largely from CO and H2 reduction equilibria. The Fe-C-0 relationships have been studied extensively by R. Schenck and his coworkers and well summarized by H. Schenck.3 More recent studies have been made by Darken and Gurry.1, 2 Data from these sources have been combined and plotted in Fig. 2. With respect to the Fe-H-O system, the works of Emmett and Schultz4 seem the most reliable, and these data have also been included in Fig. 2. Certain physical properties of the solid phases of the iron-oxygen system are summarized in Table I. The crystallographic information is of special interest as much of the present work has been concerned with the X-ray analysis of the products of reduction. Reduction with Hydrogen The reduction of ore with hydrogen is the net result of two or more gas-solid reactions. Above 570°C, the reaction sequence may be represented by stoichiometric stages as follows: 3Fe203+ H2e2Fe,O, + H20 [1] 2Fe3O, + 2H2 6FeOw + 2H2O [2] 6FeOw + 6H3 ^ 6Fe + 6H=O [3] Fe2O3 + 3H2 ^ 2Fe + 3H,O. [4] These reduction reactions follow the general form: A (solid) + B (gas) e C (solid) + D (gas). This type of gas-solid reaction has been investigated by Langmuirl' who has shown that such reactions can occur only at the boundary between the two solid phases. Furthermore, a nucleus of the second phase must initiate the reaction. Once such an interface exists, the reaction proceeds through a layer of the solid reaction product (C). The specific mechanisms involved will depend a great deal on the properties and condition of this particular layer. A number of heterogeneous reactions such as the dehydration of single crystals of copper penta-hydrate and the calcination of limestone follow this type of process. It should be noted that the inter-facial type of reaction also occurs even in dense polycrystalline material which simulates a mono-crystalline behavior.

Jan 1, 1954

By Simon T. Johnson

Potential applications for boom tunnelling machines requires reliable assessment of in-situ performance. The majority of existing classification schemes concentrate on the prediction of excavation rate, neglecting the important influence of tool consumption rates. A statistical approach is taken to the analysis of the performance data, which was obtained first-hand through in-situ monitoring, and laboratory testing of representative rock samples. A statistical discrimination technique is used to produce a scheme for the prediction of performance groups, each of which covers a limited range of cutting rate and/or tool consumption rate.

Jan 1, 1984

By Geoffrey Hughes

The Narragansett Bay Commission (NBC) is a regional sewer authority that serves ten communities in the Providence, Rhode Island metropolitan area. From 1992 to 1999, the NBC developed a comprehensive facilities plan to abate Combined Sewer Overflow (CSO) pollution in the Upper Narragansett Bay. The plan underwent many major evolutions during this period, most notably the addition of a stakeholder?s process by which NBC demonstrated a site-specific plan to control the pollutants and meet water quality standards. The favored solution consisted of deep tunnel storage with treatment at existing wastewater facilities that had been recently upgraded. In 1999, a final plan was accepted which included two tunnels, five CSO interceptors, twelve sewer separation projects, a wetland facility, and a wastewater treatment facility upgrade. The program is to be constructed over 20 years in three sequential phases (Figure 1). Phase I of the program includes a 4,963 m (16,284 ft) long, 7.9 m (26 ft) diameter, 70.1 m (230 ft) deep storage tunnel; seven drop shafts with connecting adits; ancillary facilities; and a pump station. Construction of Phase I began in 2001 and is expected to be operational by October 2008. This paper focuses on design and construction of the Fields Point Tunnel Pump Station (FPTPS)located at the south end of the main spine tunnel. A189 Ml/day (50 MGD) pump station is required to lift CSO flows from the tunnel to the Fields Point Wastewater Treatment Facility (FPWWTF). The pumps are to be housed in a 35.6 m × 18.6 m ×20.7 m (117 ft × 61 ft × 68 ft), 91.4 m (300 ft) deep cavern excavated in a complex meta-sedimentary rock of the Rhode Island Formation, and connected to the surface by 9.7 m (32 ft) and 3.4 m (11 ft) diameter shafts. Factors which influenced selection of the size, configuration and location of facilities included the preferred arrangement of pumps, critical aspects of site geology, and estimated cost. Technical and value engineering reviews also affected the final design. Following Notice to Proceed (NTP), concerns were raised by the contractor regarding constructability and design. Additional geotechnical investigation and independent engineering review were employed to validate the design assumptions. The cavern was successfully excavated and sup-ported in rock, completed on schedule and within budget in 2005. In 1992 the NBC retained Louis Berger Group (LBG) as Program Manager (PM) for the CSO Abatement Program. LBG thereafter formed a design team including: Jacobs Engineering Group(JEG) as the designer for underground structures and near surface collection facilities; Black and Veatch(B&V) to design the pumping system and associated facilities; Haley and Aldrich (H&A) to oversee the geotechnical program; and Malcolm Pirnie to design the system-wide instrumentation and control system. Construction management, resident engineering, and inspection services were provided by the joint venture Gilbane/Jacobs Associates (G/J).

Jan 1, 2008

By T. P. Meloy

Riffles on a shaking table have a major effect on particle separation. This effect is modeled in a spreadsheet.

Jan 1, 1993