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By Z. Hyder, A. Urquidez

"INTRODUCTION The Waste Isolation Pilot Plant (WIPP) is located approximately 26 miles southeast of Carlsbad, New Mexico and is the nation’s first underground geologic repository for transuranic (TRU) and TRU-mixed waste (see Figure 1). The WIPP facility was opened for operation in 1999 when the first TRU waste shipment arrived at the WIPP facility for disposal.WIPP facility does not employ typical production aspects of a conventional mine. Instead, the mining focus is on the quality of the excavation to ensure safe disposal of TRU and TRU-mixed waste (Walls, 1991). GEOLOGY WIPP underground repository is mined within a 2,000 feet-thick bedded-halite formation (Salado Formation) (see Figure 2). The WIPP underground repository is located approximately 2,150 feet beneath the surface near the center of the Salado Formation. Geologic criterion and site-selection factors evaluated for the selection of the repository included topography, depth, thickness, lateral extent, lithology, stratigraphy, structure, erosion, dissolution, subsidence, surface water, aquifers, hydrologic transport, climatic fluctuations, manmade penetrations (U.S. Department of Energy, 1980).FACILITY DESIGN Profit did not play a major role in the WIPP’s conception like in a conventional mine. This was due to the extensive amount of additional regulations and safety controls that had to be built into the WIPP facility. Since it is nuclear and hazardous waste disposal facility, it must meet certain federal and state requirements for TRU-mixed waste. One of the major regulatory drivers for the WIPP facility is defined in the WIPP Land Withdrawal Act (LWA). One of the requirements in the WIPP LWA requires the DOE to submit documentation of continued compliance with Title 40 CFR Part 191, Subparts B, and C. These standards are regulated by the Environmental Protection Agency (EPA). The DOE must submit documentation of continued compliance (recertification) with these regulations every five years. In addition to the LWA, the Resource Conservation and Recovery Act (RCRA) is another major regulatory driver for the WIPP facility. Since the WIPP facility is categorized as a “Miscellaneous Unit” under 40 CFR, it must meet extensive environmental performance standards. These standards are defined in the WIPP Hazardous Waste Facility Permit (HWFP). The HWFP defines the terms and conditions that the Secretary of the New Mexico Environment Department has determined necessary to protect human health and the environment (U.S. Department of Energy and Nuclear Waste Partnership LLC, 2015)."

Jan 1, 2017

By Z. Yanni, W. Xuan, Z. Jingyu, D. Jun

"In order to conserve the coal resources, many coal mines which have been mined begin to re-mine. Re-mining face is of complicated circumstances and coal spontaneous combustion is unknown, so experiments are designed to study the characteristics of multiple oxidized coal samples. The investigation into the oxidation of coal is conducive to the safe mining of the coal seam groups and thick coal seams. The non-caking coal is collected as coal samples. The raw coal sample with initial oxidation and the sample after second oxidation and third oxidation are obtained after a certain treatment of the coal. The temperature-programmed system, and proximate and ultimate analysis are adopted to compare the releases of gaseous products of spontaneous combustion characteristic parameters of the multiple oxidized coal sample. With the increase of oxidation times, experimental results indicate that the oxygen consumption rate, the release rate of carbon monoxide and the intensity of heat release are significantly decrease. The characteristic temperature dropped and the size of the pores in coal is smaller as well. INTRODUCTION China accounts for 13% of global coal resources [1-2]. In recent years, more and more coal mines begin to re-mine in order to conserve resources. This production mode is to mine coal pillar left by last exploitation or unavailable for mining. In the process of slicing mining for coal seam groups or thick coal seams, the second or multiple oxidation due to the mining-induced effect, may take place in the goaf of the lower seam. So the spontaneous combustion is prone to occur in this area. The study on oxidation of coal is conducive to the safe mining of the coal seam groups and thick coal seams. Scholars [3-7] have discussed the workability of re-mining for coal mines, verify the feasibility of the existing mining technology for re-mining area, and set up the prevention measures of coal spontaneous combustion. But all these measures are only based on on-site observation data, instead of experiment on spontaneous combustion characteristic parameters of re-mining coal samples which have a great importance for early prediction and forecast. The authors aim at investigating the multiple-oxidated coal spontaneous combustion law, and perfecting the coal spontaneous combustion mechanism to provide a basis for the prediction and forecast."

Jan 1, 2015

By S. K. Kawatra, V. Claremboux, S. Valluri

Carbon dioxide capture from coal-fired power plant flue gas and subsequent sequestration is expected to play a vital role in mitigating global climate change. To meet the growing need for CO2 capture Technology, Michigan Technological University is researching CO2 capture and Utilization. We have successfully converted CO2 into oxalic acid using an electrochemical approach. If oxalic acid can be produced in bulk from CO2, it can be used to leach rare earth minerals at low cost. Electrochemical reduction of CO2 to hydrocarbons and other chemicals is a complex multistep reaction with adsorbed intermediates. The exact reaction mechanisms leading to various products are not clear from the literature to date and will likely change over the range of conditions like pH, electrode potential, electrolyte medium, catalyst, etc. In this paper, we will present an idea of how the factors mentioned above will effect the electrochemical reduction of CO2 to Oxalic acid. INTRODUCTION. CO2 is thermodynamically quite stable, as shown by its highly negative heat of formation. Thus, it is expected that the formation of any useful chemical from CO2 will require the input of at least as much energy as geological sequestration. However, to be more effective the resulting economic value of the chemical need only pass the cost of the additional energy required beyond geological sequestration. This lends itself to two extremes: one where the quantity of energy required is low and one where the economic value of the additional energy is low. It is expected that CO2 can be reduced via electrolysis to several compounds. Of particular interest are formic acid, oxalic acid, methanol, ethanol, formaldehyde, and carbon monoxide (as a component to syn-gas). These chemicals have been reported as electrolytic products previously in literature and have considerable potential for application. EXPERIMENTAL Electrocatalytic Production of Oxalate from CO2 We are using membrane electrolysis cell to produce oxalate from CO2. A membrane electrolysis cell is a 2-chamber electrolysis cell where the chambers are separated by a selectively permeable membrane. To produce oxalate, a cation exchange membrane (which selectively exchanges cations) was used. Previous literature suggests that in the cathode chamber an organic electrolyte, such as tetraethylammonium perchlorate or tetraethylammonium bromide in dimethylformamide, are preferred3. In the anode chamber, a sodium hydroxide solution water is used. Carbon dioxide is then bubbled into the cathode chamber as a current is applied.

Jan 1, 2019

By Joseph Fernandez, Luminita Calin

INTRODUCTION The Tunnel and Reservoir Plan (TARP), commonly known as the Deep Tunnel Project, is the daring and unique concept developed by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) as a two-phase solution to the problem of waterway pollution and basement flooding due to sewer system backups created by the combined sewer over-flows (CSOs). Phase I, primarily for pollution control, includes the tunnels, shafts, connecting sewers and structures. These Phase I facilities intercept, during wet weather events, the CSOs within the MWRDGC TARP service area. The tunnels and shafts provide temporary storage of the CSOs for subsequent treatment at Water Reclamation Plants (WRP) before discharging into waterways. Ultimately, upon completion of Phase II, the tunnels, located from 45 m(150 ft) to 100 m (330 ft) below ground, will convey the CSOs to reservoirs for storage until WRP capacity is available. Phase II, which includes the reservoirs, pumping facilities, additional tunnels and shafts, has been planned to serve a dual purpose. The reservoirs provide storage of excess flows during wet weather events, those beyond the WRP capacity. Following the wet weather events, the stored flows can be conveyed, at controlled rates, to the WRPs for full treatment. These excess flows previously would have resulted in both overflows into the waterways and eventually backups in the local sewer systems. The storage capacity of the reservoirs also will promote the full utilization of the conveyance capacity of the tunnels and shafts, which in turn results in optimizing the conveyance capacity of the existing sewer systems. Therefore pollution control is further enhanced by allowing for capture of a greater volume of CSOs and greatly minimizing backups in the local sewer systems. The TARP project consists of four systems: O’Hare, Mainstream, Des Plaines, and Calumet, covering a total area of 971 km2 (375 mi2) and serving the City of Chicago and 51neighboring communities as shown in Figure1. With only two contracts left before completion of the Phase I tunnels, the 12.7km (7.9mi) Torrence Avenue leg, to be awarded in 1997, and the 12.4km (7.7mi) Little Calumet leg unfunded as of yet, both part of the Calumet System, the pollution control phase of the project is now 86% complete (Table 1).

Jan 1, 1997

By William J. McCloy, Robert L. Gamble

A coal-fired fluidized bed steam generator rated at 12.6 kg/s has demonstrated the industrial and institutional application of fluidized bed combustion by burning high sulfur coal in an environmentally acceptable manner within a populated area. Designed to provide steam for heating and cooling, the unit was placed into service at Georgetown University in Washington, DC, and has already logged 5275 hours.* The unit has consistently operated well within Washington's strict regulations governing emissions of sulfur dioxide (SO2), nitrogen oxides (NOx), and particulates. The Georgetown program, cofunded by the university and the US Department of Energy, has shown that fluidized bed combustion is a promising way to realize the full potential of coal, the nation's most abundant energy resource. In a fluidized bed steam generator, a layer of granular limestone is placed on top of a grid designed to prevent particles from falling through. Air is passed upward through the bed with sufficient force to lift and float the particles. At this point the bed material resembles a boiling liquid. Crushed coal is then introduced into the bed and ignited. When high sulfur coal is burned, limestone absorbs the SO2 produced. The operating temperature of a fluidized bed steam generator is relatively low (approximately 871°C). As a result, NO, formation is minimal. Another potential problem encountered in burning coal is fly ash, a form of particulate. A feature of the fluidized bed design, developed by Foster Wheeler Energy Corp., is a fly ash reinjection system. Fly ash is reintroduced into the bed where it is burned again, thereby enhancing fuel efficiency. Nearly all remaining fly ash is captured by a baghouse dust collector. At Georgetown, the fluidized bed steam generator and all auxiliary equipment are enclosed in a structure aesthetically compatible with the surrounding university complex. The steam generator has two separate beds that can be fired independently, and operation to date has been with one and two beds in service, based on steam load demand. During several operating periods, when the fluidized bed unit was the only boiler in service, it supplied all the steam required by the 18.5 hm2 of buildings on campus. Initially fired with low sulfur coal, the unit was quickly switched over to higher sulfur fuel which will be used most of the time.

Jan 3, 1981

By Eric Leung, Stephen G. Hardcastle, Andrew Dasys

In today's economic environment, Canadian mines can ill afford to neglect their ventilation systems as they can consume 30- 40% of the electricity used in underground mines. In addition, Canadian mines can incur significant heating costs. For mines to be their most cost efficient they must embrace existing and emerging technology to optimize the use of their air; namely, maximizing its work in diluting and removing pollutants, limiting leakage, and avoiding the unnecessary consumption of costly fan pressure all the while ensuring the health of their workforce. Furthermore, in Canadian mines which are heavily dieselized there is great interest within the industry to convert from a rigid quantitative approach to ventilation, based upon engine size, towards a more flexible qualitative approach that provides credit for Clean engine technology" and permits ventilation supply to be driven and based upon pollutant demands. In the future, there is even the possibility that ventilation will only be required to supply oxygen to diesel equipment as the underground hands-on workforce is replaced by surface workers and tele-operation. Such changes will allow mine operators to minimize their electrical usage and operating costs, for in its simplest form the cost of running a fan is proportional to the quantity3; therefore, reducing current ventilation demands or limiting increases brought on by more stringent legislation, can produce very significant cost savings. CANMET, through ventilation surveys and use of its modern 3D-CANVENT ventilation simulator, have been demonstrating to the mining industry how ventilation can be optimally delivered at reduced costs. El-Equip with their leaky-feeder communications and MultiVENT monitoring and control system have facilitated mines to control fans and hence costs, and also monitor such ventilation parameters as pollutant concentrations. These two parties are now combining their efforts to develop an integrated air management system which will be demonstrated at CANMET's Experimental Mine Val D'Or, Quebec. With such an air management system, the ventilation engineer will have: 1) a simple to use simulator to design and test ventilation scenarios; 2) remote controls of fans, doors and regulators to implement changes; and 3) real-time monitoring of airflow, pollutant concentrations, and both vehicle identity and location to show whether changes are necessary. It is only when all three are available, that a mine's ventilation system can be operated at minimum cost.

Jan 1, 1997

By G. L. Myers

The Fortitude skarn near Battle Mountain, NV is currently one of the largest producing gold skarns in the world. It contains about 11 Mt (12 million st) of minable ore grading 5.14 g/t (0.149 oz per st) and is the distal portion of a continuous skarn system in the Copper Canyon area centered on the Eocene Copper Canyon granodiorite porphyry. Calcsilicate compositions, opaque mineralogy, and the high gold grades are atypical of other base metal skarns (iron, Fe; copper, Cu; lead-zinc, Pb-Zn; or tungsten, W). The Copper Canyon skarn is systematically zoned from a garnet (AD 70-100) dominant, pyroxene (HD 20-45) subordinate zone, with major Cu mineralization, adjacent to the intrusive (West ore body), to a pyroxene (HD20-100) dominant, garnet (AD90-100 cores. AD 30-60 rims)subordinate assemblage, with major Au, near the distal marble front (Fortitude ore body). An extensive biotite ± diopsidic pyroxene ± kspar alteration halo surrounds the pyroxene > garnet gold-bearing skarn and represents the early stages of metasomatic alteration. Retrograde alteration is limited in areal extent and intensity, and consists of actinolite, chlorite, quartz, and prehnite. Economic gold mineralization begins in the pyroxene > garnet zone and continues to the marble front, a distance of 1 to 1.5 km (0.6 to 0.9 miles), respectively, from the plutonic contact. The opaque mineralogy in this gold zone includes pyrrhotite, arsenopyrite, marcasite, minor chalcopyrite, galena, sphalerite, argentite, hessite, hedleyite, volnyskite, and native bismuth and gold. The pyrite-pyrrhotite geothermometer yields temperatures that range from 450° C to 300°C (842° F to 582° F) and the electrum-argentite-sphalerite geothermometer yields temperatures which range from 290°C (554° F) at the marble front to about 420°C (788° F) more proximal to the intrusive. Log fS2 calculations from the sulfide assemblages yield values near - 10 with log fO2 values of about -30, in a solution of near neutral pH (5-6). Calculations of metal solubility suggest that the metals were transported as chloride complexes in the proximal skarn but that bisulfide complexes were predominant within the distal gold skarn. Relatively low oxidation states buffered by the carbonaceous to argilliceous, calcareous protolith and subsequent ferrous iron-rich skarn assemblages appear to have increased the gold carrying capacity of this large hydrothermal system.

Jan 1, 1991

New South Wales (NSW) and Queensland dominate Australian black coal production and exports. NSW produced 86 Mt (95 million st) of saleable coal in 1994, a doubling of output since 1980. Asian demand for thermal and coking coal has driven this growth. This high Asian demand is expected to continue and NSW will seek to secure its share. History The history of the New South Wales (NSW) coal industry can be traced to 1797 when coal was first taken from Newcastle to Sydney (Ellis, 1969). At that time, NSW was a British colony, independent from the other colonies, such as Victoria and Queensland. Australia, as a federation of colonies, did not exist until 1901. The Newcastle coal industry grew through the 1800s in line with the growth of the colonies. Several events spurred demand for Newcastle coal. These included: ? The NSW and Victorian gold rushes of the 1850s and associated population growth. ? The development of steamship traffic at the expense of sail. ? The development of railways and town gas supplies. By 1900, Australia was producing 6.4 Mt (7 million st) of coal, most of it from NSW. By then, NSW had established strong export markets in Indonesia, China, Japan and New Zealand. The history of energy consumption is marked by continual competition, changing intensity of use and substitution. From 1900 to 1940, the Queensland, Victorian and Indonesian coal industries developed at the expense of NSW exports. Similarly, New Zealand developed its hydroelectric industry and thus declined as the largest customer for NSW coal. Oil replaced steam in the shipping and railway markets and electricity replaced gas for lighting. Industrial efficiencies also affected coal. Between 1928 and 1938, coal consumed in generating power fell from by 17% on a kilowatt hour basis and, during the same period, the amount of gas produced per ton of coal rose by 18% (Shaw and Bruno). Faced with these pressures, production and exports stagnated. By 1941, Australian black coal production was 14.2 Mt (15.6 million st). NSW's production was 11.7 Mt (12 million st), up only 19% from 1912. Exports had virtually ceased (Fig. 1). In such circumstances, the industry had lost focus. Unions resisted the need for mechanization, for security of employment reasons, and owners were loath to invest. This reluctance to mechanize and the associated in-

Jan 1, 1997

By Ronald C. W. Webber‑Youngman, Philani Larrance Ngwenyama

Entrapments are a huge risk in underground mines. This happens when miners (or any other persons who have entered underground) survive the initial event of an accident, become trapped or lost in unknown and life-threatening locations after evacuation, and remain unaccounted for. At this point, every second counts, and emergency response is highly desired for any chances of saving survivors. The survival chances of the missing persons depend on how quickly they can be located. Rescue teams are often deployed to search for the missing persons underground. However, the rescue teams are forced to search in random and presumed areas of the mine. This is due to the unavailability of information pertaining to the whereabouts of the missing persons. Not only the provision of accurate locations, but various other types of information such as post-accident two-way communication can enhance the survival chances of the missing persons. This information can be provided by a fit-for-purpose missing person locator system. A wide variety of missing person locator systems are already commercially available, some are in testing phases and others in prototype and development phases. This includes tracking, tracing, location detectors and post-accident two-way communication systems. These systems have unique functionalities, capabilities and limitations; making it difficult for mines to select the most effective, applicable and suitable system specific to their mine. In this study, the user requirements for a fit-for-purpose missing person locator system were developed. The purpose of the user requirements was to provide a guideline to facilitate the system selection process. The user requirements can also be used as a tool to measure and evaluate the performance of the selected missing person locator system. The user requirements were also used to predict the success of the selected system under different missing person incident scenarios. The development of the user requirements showed a potential for many other benefits for missing person locator systems.

Nov 2, 2023

By C. Konya, A. Konya

"INTRODUCTION Over the past twenty years this Linear-Regression Modeling has become widely accepted for ensuring limits are not exceeded at a site, using the Scaled-Distance variable. In today’s industry, numerous equations are present for different scenarios, geologic environments, hole sizes, and numerous other factors with an emphasis on site-specific equations developed for all major projects; however, underground blasting applications have not been analyzed to a great degree of detail. Without previous knowledge this puts underground blasting operations into a guessing-game to ensure that vibration levels are not exceeded. This paper will review two recent projects that have been worked on by the authors and linear-regression models that were used with both burn cuts and stope blasts. BLAST VIBRATIONS MODELING The first major research project conducted in the United States on blasting vibration was Bulletin 442 (Thoenen & Windes, 1942) which looked at the relationship between blasting and blast vibrations in the fall of 1940. This study examined numerous blasts and began the investigation into topics such as damping, structural damage from vibrations, frequency dependency on vibration, resonance vibration, delayed blasting, and numerous other factors. Bulletin 442 had two major conclusions which are: 1. The vibration from a blast can be predicted with a relationship of size of the shot and distance to the structure (now known as scaled distance) 2. “The vibration of a structure at resonance does not in itself cause damage because of the restraining effect of damping inherent in the building” (Thoenen & Windes, 1942) Due to the increase of blasting near homes and busier areas the USBM commissioned an additional study to further develop a few of the topics covered in Bulletin 442; this study would go on to be published as RI 6561 (Duvall, Johnson, Meyer, & Devine, 1963) with the study looking into delayed blasting and the relationship between charge weight, distance, and peak particle velocity of the blast. This relationship would be termed as the ‘scaled-distance’ and take the form of:"

Jan 1, 2018

By Achille Balossi Restelli, Elena Rovetto, Andrea Pettinaroli

"The Station “C13” of Warsaw Underground Line II, with tunnel crown 10m below the water table, required the excavation of three connection tunnels, underpassing a six-lane in service road tunnel, working from two lateral shafts. After the collapse occurred while digging the first tunnel, the use of artificial ground freezing was chosen to ensure the excavation under safe conditions. A complex freezing pipe geometry and excavation sequencing was necessary because of the interferences of the overlying road tunnel diaphragm wall foundations, shaft internal structures and previous grouting activities. A combined freezing method was used: nitrogen for freezing the tunnel arches, brine for freezing the intermediate wall and for maintenance stages. Sandy and silty sandy layers were frozen around the crowns and sides. No treatment was necessary for the inverts, lying in clay. A monitoring system of ground temperatures and structure movements allowed for successful completion of work in 8 months. INTRODUCTION The C13 Station of the Warsaw Underground-Line II is located on the West bank of the Vistula River. It consists of two shafts and three connecting tunnels, passing under the Wislostrada (WS) Road tunnel. According to the initial geotechnical investigation, tunnels should have been excavated in high-plasticity clay, but during the first borings non cohesive soil was encountered. Additional investigations were performed on both shafts and a more detailed stratigraphy was reconstructed (Lombardi et al. 2015). Layers of fine sand, sandy silt and sandy silty clay were present along the tunnels crown arches and in the North East tunnel they extended down to the centre line (-13.735m above the Vistula River medium level). Based on the new stratigraphy, it was decided to stabilize the crown and control the groundwater inflow from the face with jet-grouting columns extending the treatment down to the clayey soil, but a collapse occurred in the North West tunnel with soil and water inflow inside the shaft."

Jan 1, 2016

By M. Soya, M. Imazu, Ö. Aydan

"SUMMARY Taru-Toge tunnel is being constructed using drilling-blasting technique as a part of expressway project connecting Shin-Tomei Expressway and Chuo Expressway at the boundary of Shizuoka and Yamanashi Prefectures in the Central Japan. The maximum overburden is about 400 m. The authors have been carrying out a monitoring program to measure dynamic and multi-parameter responses of tunnel during and soon after the blasting operations using a multi-parameter monitoring system (Acoustic Emissions (AE), Electric Potential (EP), Temperature (T), Humidity (H) and Air Pressure (P)) and stand-alone type compact accelerometers developed by the first author. The measured response involves dynamic vibrations and other measurable parameters caused by blasting as well as by stress-redistribution around the tunnel face. This is one of the first attempts in the world to measure the response of rock mass caused by blasting at a very close vicinity of the tunnel face. In this paper, the authors present the outcomes of this unique monitoring study on the dynamic responses of the Taru-Toge tunnel during excavation and discuss their implications in actual applications. INTRODUCTION The real time monitoring of the stability of tunnels are of great importance when tunnels are prone to failure during excavation such as rockbursting or squeezing (i.e. Aydan et al. 1993, 2001). Experimental studies by the authors showed that rock indicates distinct variations of multi-parameters during deformation and fracturing processes (i.e. Mizutani et al. 1976; Aydan and Daido 2002; Aydan et al. 2003, 2011). These may be used for the real-time assessment of the stability of rock structures. An application of this approach was done to the Taru-toge tunnel a part of expressway project connecting Shin-Tomei Expressway and Chuo Expressway at the boundary of Shizuoka and Yamanashi Prefectures in the Central Japan (Imazu et al. 2015). The parameters measured involve electric potential variations, acoustic emissions, rock temperature, temperature and humidity of the tunnel in addition to the measurements of convergence and loads on support members during the face advance."

Jan 1, 2016

By K. A. Natarajan, K. Karthiga Devi

"A biodegradable flocculant was produced during growth of Bacillus megaterium. The major component of the bioflocculant was found to be a polysaccharide composed of some proteins. Fourier transform infrared (FTIR) spectra analysis revealed the presence of carboxyl and hydroxyl groups in the bioflocculant, and thermal characterization by differential scanning calorimetry (DSC) showed the transition and crystalline melting point at 90-105°C. The effects of bioflocculant dosage and pH on the flocculation of mineral suspensions were evaluated. The bioflocculant exhibited good flocculating capability on mineral suspensions and achieved flocculating efficiencies of 90 percent for kaolinite and 85 percent for hematite suspensions at a dosage of only 5 mL/L. The maximum arsenite removal was found to be 90 percent at a bioflocculant dosage of 2 g/L, which is better than traditional chemical flocculants. This study demonstrates that microbial bioflocculants have potential for application in environmental cleanup, such as in the flocculation of mineral fines and in the remediation of solutions that contain toxic heavy metals.IntroductionBioflocculants are biopolymers produced by microorganisms during their growths. The predominant components of a bioflocculant are extracellular polymeric substances such as glycoprotein, protein, cellulose and nucleic acid (Salehizadeh and Shojaosadati, 2001). Bioflocculants have gained much wider attention due to their biodegradability and safety. In recent years, the study of bioflocculants has attracted wide attention. Bioflocculants can be nontoxic, harmless and eco-friendly. Normally, they exhibit different functional properties, serving as stabilizer, dispersant or thickener. Among these properties, flocculation is of major interest. For example, Phormidium sp. strain J-1, isolated from a drainage channel, exhibited excellent flocculation activity for bentonite particles in liquid suspension (Fattom and Shilo, 1984). A protein bioflocculant produced by Rhodococcus erythropolis could efficiently flocculate suspended solids while losing their flocculating activity by enzymatic digestion (Kurane et al., 1994, Takeda et al., 1991). Klebsiella sp. strain S11 screened from activated sludge was unable to flocculate without the addition of calcium chloride (Dermlim et al., 1999)."

Jan 1, 2015

By Anita Wu

"GENERAL BACKGROUND/CONTEXT The £300 million Bond Street Station Upgrade project will provide essential congestion relief and step-free access to an important interchange and destination station in the heart of the London Underground network. In 2010 London Underground (LU) let a design & build contract to Costain Laing O’Rourke (CoLOR), with the works to be completed in early 2017. CoLOR’s lead designer is Halcrow-Atkins JV (HAT). The station upgrade works comprise the following principal elements: •,A new satellite ticket hall on the North side of Oxford Street •,Two additional escalators and stairs providing congestion relief to the Jubilee line platforms •,Four lift shafts to provide step-free access between the different levels of the station •,Additional stairs to Central line platform level •,Tunnelled connection to the Crossrail station immediately to the south •,Connecting passageways, including ten connections to existing station tunnels. To achieve this, an existing property at 354-358 Oxford Street has been purchased and demolished, and the basement deepened to make provision for the new ticket hall. From this basement two circular shafts have been sunk, providing construction access for the tunnelled passages and lift and escalator shafts. The tunneling is principally in the London Clay stratum, which is widely recognized as a favorable tunneling medium, although the deepest parts of the works extend into the Lambeth Group strata which consist principally of stiff clays at this level but also contain water-bearing sands. The majority of tunneling has been carried out using mechanical excavation and sprayed concrete linings but other techniques have been used in areas where SCL is not practicable.A key challenge for design and construction of the works has been spatial constraint, in particular due to: •,The existing underground station layout •,The Limits of Deviation for the works •,The small construction site at 354-358 Oxford Street •,Overlaying Third Party assets including Listed buildings, sewers and water mains."

Jan 1, 2016

By W. L. Freyberger

In many papers concerned with fundamentals of the froth flotation process, authors have considered the contents of a flotation cell to be comprised of two immiscible phases, the froth and the pulp. I (Of course, each of these phases is in turn made up of several solid phases plus air and water.) This generalized concept of the flotation system can be extended by considering the cell contents to include two phases: an extracting phase, the air bubbles plus the collector, which removes a selected mineral component from the second phase, the ore pulp. Thus, there is an analogy between a flotation system on the one hand, and chemical extracting systems, such a solvent extraction system or a leaching system, on the other hand. Such extracting systems may be operated in cocurrent or countercurrent fashion. This paper includes first a brief discussion on the general nature of cocurrent and countercurrent operation as applied to froth flotation, and then presents the experimental results of flotation of a specular hematite ore by each method, using a tall oil fatty acid as collector. Cocurrent Flotation A conventional flotation circuit involving roughing, scavenging, and cleaning flotation is illustrated schematically in Figure 1. In such a circuit the col¬lector, or extractant, and new feed ore enter together at the head of the rougher circuit, and flow cocurrently to the scavenger circuit where more collector is added. According to this practice, sufficient collector is added to the head of the rougher (and scavenger) so that the final tailings are of low enough grade to be discarded. Since the flow of collector and ore is cocurrent, the process consists of single stage contact between the extracting phase and the ore pulp. If the scavenger concentrate is recycled to the head of rougher, the overall circuit has some of the characteristics of countercurrent flow. In such a case part of the extractant (collector) is added at the discharge end of the circuit, and may

Jan 1, 1971

By Cheng Ang, Yun Bai, Zhi Liu

"This paper presents a conceptual design of an innovative tunnelling method named the Ring Pipe Jacking Method (RPJ) which is conducted by the Ring Pipe Jacking Machine (RPJM). The RPJM consists of a double ring shell which forms a ring section where small interlaced cutter heads or several micro tunnelling machines are assembled to cut soil. Similar to the conventional pipe jacking method, the RPJM also needs a thrust system, a slurry transport system, and a control system. To satisfy the need for large/super large or special section tunnels in future, the RPJM is designed to reduce sharply the excavation face to the annular section, thus enhancing the face stability. Part of the innovation is that the RPJM uses modular cutter heads or micro-TBMs which can be reused. The typical double shield shape can be easily changed by reinstalling the modular cutter heads. Modularity allows the tunnel to be cut in any cross-section shapes, ranging from a circular tunnel to a rectangular one. INTRODUCTION The demand and requirement to utilize urban underground space is rising with the rapid social development in recent years. It is necessary to reduce excavations of the urban ground surface to ensure smooth traffic in cities. Therefore the conventional open cut construction method for underground tunnels can no longer satisfy the need of practical engineering, and it is taken over by trenchless technologies .The Pipe jacking method is an important trenchless technology and is used more and more frequently to install underground pipelines, but the present pipe jacking method still has many problems. For example, it is not suitable for installing large-diameter tunnels and it also has difficulty in construction of short radius curved tunnels. This paper presents a conceptual design of an innovative pipe jacking machine named the Ring Pipe Jacking machine (RPJM) and introduces the correspondent Ring Pipe Jacking Method (RPJ) which can be applied to construct large-diameter tunnels. Furthermore, technical characteristics and superiority of the ring pipe jacking method are analyzed in this paper."

Jan 1, 2016

By Stephen Liu

Tunnel excavation while mining is not often performed in North America primarily due to access constraints in both operations. Referencing European approaches for long distance tunneling, the Devil?s Slide Tunnel project has applied innovation and technology to provide the ability to overcome this unique challenge. The Devil?s Slide Tunnel requires the construction of twin bore tunnels excavated based on sequential excavation method (SEM) construction methods using New Austrian Tunneling Methods (NATM) principles. The twin tunnels are approximately 9 m (30 ft) in diameter and 1,250 m (4,100 linear ft) in length. The purpose of this project is to reroute Route 1 from around the Devil?s Slide through the San Pedro Mountains crossing from Montara, CA along the south and into Pacifica, CA in the north. The Caltrans project was awarded in December 2006 for a total of $272,366,000. The job is an A+B job, thus the estimate scheme of final lining while tunnel excavation is important to save time. A+B is a method of rewarding a contractor for completing a project as quickly as possible. By providing a cost each working day, the contract combines the cost to perform the work (A) with the cost of impact to the public (B) to provide the lowest cost to the public. Concurrent mining while lining is achieved through a series of gantries and a set of tunnel forms allowing the pass-through of the excavation equipment. The tunnel lining operation passes through several phases of work that are dependent upon the progress of the tunnel excavation process. This involves unique milestones, such as the evolution of the ventilation system, development of an enlarged cross passage to allow equipment to access each tunnel from within the tunnel and, finally, the installation of an invert prior to arch lining that limits the continuity of the final lining operation.

Jan 1, 2011

By D. S. Bird

The Kennecott Utah Copper Modernization Project, initiated in 1986, was directed to provide an expansion and modernization of mining and process facilities at the property's Bingham Canyon Mine and ore concentrators. Major components in the project included installation of an in-pit ore crusher, transfer conveying system, and construction of a new copper ore concentrator with a design capacity basis of 70,000 tonnes/day. The Copperton Concentrator was commissioned in February 1988. A principal feature of the plant is the grinding circuit, comprised of three identical lines, each consisting of a 10.37 m (diameter) by 4.57 m (length) Semi-Autogenous Grinding (SAG) mill and two 5.54 m (diameter) by 8.62 m (length) ball mills. The SAG mills are driven by two variable-speed 9,000 kW DC motors coupled through a clutch-pinion gear-ring gear assembly. The ball mills are driven by 4,125 kW synchronous motors coupled through a typical clutch-pinion gear-ring gear system. The expansion and particularly the Copperton Concentrator performance was so successful that by early 1989, management began examining options to further expand production capacity. With regards to the concentrator, numerous alternatives were considered, ranging from installation of a grinding line similar to one of the existing lines, to a "super" line consisting of a 12.8 meter (diameter) SAG mill and a 20,000 kW motor with a capacity of 50,000 tonnes per day. The technical and economic analysis of the various scenarios indicated that one "large" 11.0 meter (diameter) by 4.88 meter (length) SAG mill with a production capacity of 32,000 tonnes per day and a 12,000 kW drive would be optimum. The key question to be answered in the project was whether to continue with the pinion-ring gear combination, or install a gearless drive. The following paper outlines many of the items that were evaluated in the mill selection process followed by actual plant performance, and a discussion of ongoing plant continuous improvement projects.

Jan 1, 1995

By Clarence O. Babcock

Model pillars of limestone, marble, sandstone, and granite, with length-to-diameter ratios of 3, 2, 1, 0.5, and 0.25 (0.286 for granite), were broken in axial compression to determine to what extent an increase in end constraint increased compressive strength. Radial end constraints of 13 to 23 percent of the average axial stress in the pillar, produced by solid steel rings bonded with epoxy to the ends of dogbone-shaped specimens, increased compressive strength somewhat above that of cylindrical pillars without ring constraint. However, when the results were compared with those obtained by other investigators for straight specimens of several rock types taken collectively, with L/D ratios greater than 0.5, the resulting strengths were not significantly different. Thus, the amount of end constraint produced by the solid steel rings was about the same as that produced by the friction from the steel end plates. In other tests a radial prestress of 3,000 psi or 5,000 psi was applied prior to axial loading by adjustable hardened steel rings to increase the constraint above that obtained for the solid rings. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 3,000 psi prestress, was 54.3 percent for limestone, 40.3 percent for marble, 44.7 percent for sandstone, and 23.4 percent for granite. The average radial constraint stress, expressed as a percentage of the average axial pillar stress at failure for the 5,000 psi prestress, was 74.2 percent for limestone, 51.2 percent for marble, 61.6 percent for sandstone, and 29.7 percent for granite. These constraints increased the compressive strength significantly above the strength of straight specimens and solid-ring constrained specimens. These results suggest that large horizontal stresses in orebodies mined by the room and pillar method should increase the strength of the pillars and allow an increase in ore recovery by a reduction of pillar size when major structural defects are absent.

Jan 1, 1969

By Subhash Bhagwat

The definition of high sulfur coal varies from plant to plant and is subject to changes over time as the environmental regulations change. In plants constructed after September 1978 hardly any domestic coal can currently be burned without the use of Flue Gas Desulfurization (FGD) because a 70 percent reduction in potential S02 emission is mandatory even when the potential emission is less than 0.6 lbs. S02/106 Btu heat input. On the other hand older power plants may in many cases be legally emitting up to 6 lbs. S02/106 Btu or more under some State Implementation Plans (SIP). The Clean Air Act requires, however, that in the long run all stationary sources of S02 pollution must abide by the ceiling of 1.2 lbs S02/10 Btu heat input.. Coals with a potential to exceed this limit must, therefore, be considered as high sulfur coals. Such a definition would be unrealistic because many SIP's aim at an emission level of 1.8 to 2.0 lbs. SO2/106 Btu for existing plants and a stricter limit does not appear to be enforceable in the next 5 to 10 years. As a result, coals with an emission potential of greater than 2.0 lbs of S02 per 10 Btu heat input are considered high sulfur coals for the purpose of this investigation. Based on this definition and the 1984 actual consumption of coals by U.S. electric utilities (table 1) only 7 out of the 24 coal producing states could be categorized as low sulfur states. The actual S02 pollution, however, depends on total tonnage of a type of coal as well as the sulfur content of the coal. Table 1 also indicates that only 6 states--Kentucky, Illinois, West Virginia, Ohio, Pennsylvania and Indiana-account for nearly 77 percent of S02 pollution potential in the United States. These 6 states have therefore been chosen for this investigation.

Jan 1, 1986