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By D. Q. Li

"This paper briefly introduces problems that can occur in the design of rare earth separation processes and that require close attention during engineering design. Important factors must be considered include the following. 1) The separation process is primarily based on two points. One is the raw material composition and the other is the product purity requirements. 2) Optimization of the rare earth separation process requires optimization of the flowsheet configuration and each process parameter. 3) The separation of heavy rare earths is performed under non-equilibrium conditions. 4) The radioactive elements uranium and thorium must be removed from the feed to separation. 5) Process economy and environmental protection must be considered together in the evaluation of any separation technology options. INTRODUCTIONThe importance of rare earth (RE) is well recognized in high-tech applications and sophisticated national defense technologies. RE is the treasure house of the 21st Century new materials. The RE separation processes developed using HEHEHP (P507), P507-alcohol (ROH) and naphthenic acid (NA) have been widely applied in China. These processes have led to industrial production of all of the individual RE with up to 4N (99.99%) or higher purity (Li, Wan, Lin, Xie, Lin, & Wang, 1980; Li, Wang, & Xie, 1985; Li, 1995; Li, Wang, Meng, & Li, 2005). In order to achieve the best economic and environmental benefits, this paper discusses several problems to which attention must be paid in the design of rare earth separation process."

Jan 1, 2016

By V. Estrada, G. Aguilera

"Since the most of mineral processing are wet, and for more specific applications where it is necessary to increase the purity through leaching and / or concentration, the proper dispersion is the first, and perhaps more crucial stage in the whole chain of processing. This specific process is based on the formation of a dispersion or suspension of mineral, trying to make the mixture as homogeneous as possible, and with specific rheological conditions. Sometimes it is not enough agitation to make it happen, so that chemical additives are used as an aid. However, the addition of chemicals strongly alters the viscosity and other rheological properties of the suspension factor to consider for subsequent steps to ore beneficiation. In other hand, in a process where no chemicals used often employ large quantities of water to achieve dispersion. But if an efficient chemical agent, which optimizes said dispersion through a specific physicochemical effect on the particle surface is used, also it can generate rheological advantages, besides achieving rational use of water and increase the recoveries of the product main about also optimal costs. The aim of this work is to find the optimal rheological conditions for a dispersion of kaolin as study case, looking for stability, best disaggregation, viscosity and pseudoplasticity.To find the optimal additive, the evaluation parameters were: 1) Best degree of dispersion of the suspensions according to the analysis of the flow curve; 2) Best level of disaggregation of particle chemical analysis delaminated by Particle Size Distribution; and 3) Best thixotropic rheological parameters and pseudoplasticity. Finally the optimum additive as one that meets the best combination of parameters is proposed.INTRODUCTIONKaolin is a clay material formed by altering of feldspar composed mainly for kaolinite. Depending on the application, the kaolin as raw material must be refined and processed because the ores of clays contain usually a lot of impurities derived of its sedimentary source, such as feldspar, mica and quartz (Torres, et. al., 2011). According to the experience on the plant floor and the publication of several scientific papers, it is known that the dispersion is a crucial stage in mineral processing (Greene, Duke, & Hunter, 1965) (Raghavan, et. al., 2004), not only because of the disaggregation of particles, besides because of the humectation of them. Is clear that disaggregation of particles give to the suspensions rheological stability, and the humectation improves the effect of further processes like grinding or chemical treatment. The dispersion process involves making a suspension of the mineral with a solvent which is usually water, to obtain a homogeneous dispersion, with the aid of energy of stirring. Sometimes is not enough the agitation (even with high energy) for this to occur, so is necessary the use of dispersing substances which introduce ions and molecules as modifiers of chemical potential, forcing the molecules of the material to disperse. Sometimes their use even could affect the pH of the suspension in a non-desirable condition. (Flores, 2013)."

Jan 1, 2016

By Scott G. Giltner, Terry Millar, Ben Bringhurst

"Kennecott Utah Copper (KUC) Smelter scheduled a rebuild of their flash smelting furnace forSeptember, 2014. KUC’s goal in this project was to reduce the rebuild time from 65 to 55 days by using explosives to break the matte and brick layers of the uptake shaft and hearth sections of the furnace. Previous rebuilds had employed the slower technique of mechanical breakers to remove the matte and brick layers which took 22 days. KUC has many years of experience in removing slag from the uptake shaft, but they had never used explosives to remove the hearth. As far as KUC was aware, no other smelter operation had attempted a hearth removal in this way."

Jan 1, 2016

By Majid Sadeghi, Ali Naghi Dehghan, Kaveh Ahangari, Seyed Mahdi Pourhashemi

"Instrumentation and monitoring of ground deformations in tunneling is a principal means for selecting and controlling the excavation and support methods among those foreseen in the design, for ensuring safety during tunnel construction (including personnel safety inside the tunnel and safety of structures located at ground surface) and, finally, for ensuring construction quality management. In this paper, the effect of Hakim Tunnel excavation on the behavior of the surrounding ground was investigated based on the geotechnical instrumentation. This tunnel with 1080 m length, 18 m width and 12.6 m height is being constructed using the SEM/NATM along the Hakim Highway in Tehran. The results which are obtained from recorded displacements by geodetic pins (on the tunnel wall and roof), extensometers and settlements pins (at the ground surface) demonstrate the tunnel stability during the various stages of excavation. However, it is concluded that the rate of excavation in different sequences could have a major role on stability of tunnel. In this case the surface and underground openings were monitored as well as needed for controlling the face probably collapse. INTRODUCTION Tunneling is increasingly being used world-wide to provide the infrastructure required for sustainable urban areas. The high demand for space and the disturbance of existing infrastructures by construction measures increasingly forces future infrastructure projects to be conducted underground. One of the important purposes of tunneling projects in urban area is not only to minimize displacements but also to control them during the construction (Pourhashemi et al., 2015). Normal method of tunnel stability analysis is not able to evaluate the real rock and soil mass behavior. Hence, instrumentation is a practical method to monitor displacements, to evaluate the stability of underground openings, and also to determine the rock and soil mass properties (Dehghan et al., 2012. Dehghan, 2013). Rocks and soils are materials with properties that can change instantly and significantly from one point to the next. Some complications may often happen due to uncertainties in the loads that the new facility must withstand during construction and operation. Instrumentation and monitoring provide quantitative information on actual behavior of ground and adjacent structures. A lot of deformation monitoring studies for determining and analyzing different kinds of engineering structures such as tunnels, bridges, high-rise buildings and dams are implemented. Considering the type of the structure, its environmental"

Jan 1, 2016

By Bryce Sullivan, Cliff Baratta, Ehsan Alavi, Timothy Dobbs, Lisa Mori

"Soil conditioning is one of the main factors in successful application of EPB machines in tunneling projects, which involves changing the characteristics of the ground in order to make it suitable for the tunneling process. Selection of the type of conditioner mainly depends on soil type, properties of the tunnel boring machine, and most importantly geological condition. Proper EPB tunneling and soil conditioning in ground above water table is challenging. This was encountered in Northgate Link Extension Tunneling Project in Seattle, WA. In order to improve the tunneling operation, a novel algae-based encapsulated oil was used as a conditioner and as a result the operation of the TBM was improved significantly. This paper reviews the traditional soil conditioning measures that were adopted in University Link and Northgate Link projects in Seattle, WA and compares the results with results when using the encapsulated oil additive. INTRODUCTION Soil conditioning agents are used in EPB tunneling to transform the excavated soil into a workable paste with the desired hydrological and mechanical properties. Reducing wear, power consumption, friction, adhesion, and improving the face stability and material flow are some of the benefits of using soil conditioners in EPB tunneling. Soil conditioning is performed by injecting foam, polymer, water, and bentonite to the tunnel face, excavation chamber and screw conveyor. Selection of conditioning agent mainly depends on soil type, geological condition (groundwater and soil permeability) and TBM features (injection points, open or closed cutterhead, type of foam generator, etc). The most widely used soil conditioners are foam and polymer and in some cases due to existing conditions, clay dispersion or anti-wear additives are also used (Milligan 2000, Langmaack 2000). Foam. Foam is created by dispersing air in a surfactant solution. A different combination of surfactant type and foam parameters should be used for different soil types. Laboratory tests on virgin soil should be performed to identify the best surfactant and foam parameters for the specific soil type (Langmaack 2000). The foam parameters can be described as follows:"

Jan 1, 2016

By C. McAllister, D. Preece, J. Berendzen

The Multiple Blasthole Fragmentation (MBF) model was developed recently and has been reported in previous papers. The MBF model accepts inputs from the blast design, such as: location and orientation of each blast hole, stemming length, blast hole diameter, multiple decking, bench height, initiation sequence, etc. It models the effect on fragmentation of delay timing with its associated scatter for each blast hole. MBF has a statistical modeling capability for geological random variation of the attenuation of particle velocities. Also simulated is wave reinforcement due to the interaction of simultaneously arriving waves or diminishing cooperative contribution from long delay intervals between charges.

Jan 1, 2016

By Lena Paar

"Underground construction poses certain challenges for all parties involved because the actual ground conditions are often unpredictable. Highly complex projects like tunnel construction are affected by various uncertainties. To address this complexity, the construction contract has to be flexible enough to be adapted to the actual conditions (e.g. divergent ground conditions, work delays). However, the adaptation of a tunnel construction contract does not guarantee the absence of a margin of interpretation. The perfect construction contract is an illusion because ex ante statements of the actual ground conditions are not feasible. This paper will discuss contractual parameters that must be considered in order to enable an effective adaptation of the contract during excavation. It is therefore necessary to discuss the following topics: decision-making competence, variable remuneration, fair-risk allocation, value engineering and partnering between client and contractor. INTRODUCTION Thinking of tunnel construction processes, engineers’ first (or at least second) association is about ground conditions. When constructing under the surface, the project is directly related to the ground conditions; however, ground conditions are known fairly well in advance. The estimated conditions can be the same or can also differ from the existing ones. A clear view of the conditions is possible only by driving through the section. What Hoek calls “Geological unpredictability which is guaranteed to provide some surprises in even the simplest tunnelling job” is, in addition to contractual issues, one of two critical aspects of modern tunneling (Hoek 1982). Almost no research tries to figure out, what flexibility in this context means and how to approach it in the contracts. Papers dealing with the New Austrian Tunnel Method (NATM) pose some principles to meet the requests for flexibility (cf. Austrian Society for Geomechanics 2011). However, it remains unclear how to create contracts in order to make them “flexible” enough to react to divergent ground conditions."

Jan 1, 2016

By Jon Errey, Aleksandar Petrovic, Karl Haase

"Developing a gold deposit of this magnitude in the Amazonian jungle of Guyana posed many challenges. This paper describes not only the process & logistical challenges arising from the remote mine site location in a tropical environment with a local industry unaccustomed to recent large scale gold mining operations, but also the innovative technical solutions employed to address the unique ore body characteristics. The best examples of this approach were dealing with the initial high clay content saprolite ore from the development phase and primary mining pits whilst ensuring that the design also implemented the right method to deal with the future fresh rock in an environmentally sensitive habitat. In order to do this separate individual crushing flowsheets were generated, focusing on the specific material handling equipment that would be suitable to handle these various types of material and ensure high recoveries were maintained.INTRODUCTIONAurora gold mine is located in forested region of Guyana, 170 km west of capital Georgetown, and 130 km West North-West of Bartica, a settlement at the junction of the Essequibo and Cuyuni Rivers.The Aurora gold project (Aurora) is a 5,000 tonne per day open-pit/underground operation, which will produce a total of 3.29 million oz. gold – averaging 194,000 oz. per year – over an initial 17 year mine life. At the final investment decision in 2014 Aurora had a total resource of 6.54 million ounces in the measured and indicated categories (62.83 million tonnes at 3.24 g/t Au) as well as additional 1.82 million ounces in the inferred category (16.93 million tonnes at 3.34 g/t Au)."

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 A. Noble

"A supply of sustainably sourced rare earth elements (REEs) is critical for several high-tech industries, renewable energy technologies, and defense applications. Recent studies have shown that REEs exist in coal and coal combustion byproducts at elevated concentrations and in quantities that could meet domestic demand. Despite these promising findings, declines in rare earth prices, volatile commodity markets, and challenging geo-metallurgical conditions have jeopardized this potentially valuable REE resource. While the dilute REE concentrations inherently necessitate low-cost separation technologies, the ultimately operating cost threshold for economic extraction must be based on commodity price projections and market demand. In this paper, the micro-pricing principle is used to develop a rigorous economic model assessing the inherent value of REEs in coal materials. This model is based upon basket pricing of individual elemental oxides, and elemental distributions of coal samples from various basins. These results may be used to assess the economic viability of potential REE concentration and refining technologies INTRODUCTION Recent efforts by US Department of Energy (DOE) and the National Energy Technology Laboratory (NETL) have suggested that rare earth elements (REEs) may exist in coal and coal byproducts at concentrations suitable for economic extraction and processing. While the knowledge of REE occurrence in coal material dates back over 50 years, recent supply restrictions and material criticality considerations have prompted a national interest to establish a sustainable domestic supply of REEs. REEs are not “rare” in the sense of crustal abundance; however, few natural processes lead to concentrated ore deposits. As a result, the elevated concentrations found in coal material may provide a potentially promising resource for these materials. While the term “rare earths” is often used to describe a singular concept, the 15 rare earth elements actually have varying and sometimes contrasting scarcity and cost profiles. Various authors have proposed classification systems to provide information on REE criticality (e.g. Seredin and Dai, 2012, Zhang et al., 2015). The most straightforward classification is provided on the basis of geochemistry with designations for “light”, “medium” and “heavy” rare earths. Light rare earths (those to the left of the periodic table: Ce, Pr, Nd, and Sm) tend to be more common and less valuable when compared to their medium (Eu, Gd, Tb, Dy, and Y) and heavy (Ho, Er, Tm, Yb, and Lu) counterparts. While light rare earths are often found in traditional ore deposits at economic concentrations, the heavier rare earths are almost exclusively found as ion-absorbed clays (Seredin and Dai, 2012)."

Jan 1, 2016

By S. Komar Kawatra, Youlian Zhou, Joseph A. Halt

"Bentonite clay has been the most common binder for iron ore pellets. Although bentonite increases pellet strength and durability, it has several disadvantages. For example, its use increases the cost of pellets and decreases pellet purity due to its composition and the higher levels of flux required to meet basicity limits. Several new types of binders have been proposed to replace clay. The binders include starch, modified humic acid (MHA), and dispersants. These binders were used to pelletize a magnetite concentrate from the United States. Typical doses of each binder type were 0.05-0.1 % starch, 0.5-0.75 % MHA, and 0.05 % dispersant. At these doses, the pellets exceeded the minimum recommended values for wet drop, dry compression strength, and fired compression strength. Pellets made with the MHA and dispersants had the lowest abrasion rates of the new binders, and were comparable to pellets made with bentonite clay. In this paper, we compare the new binders, considering pellet quality and the advantages and disadvantages of each binder type.INTRODUCTIONIron ore pelletizers need binders in order to make good quality iron ore pellets. The typical binder is bentonite clay, an alumino-silicate material. Bentonite increases the ballability and strength of iron ore concentrates, but reduces pellet iron grade and reducibility. As high quality bentonites can be expensive to ship, low quality bentonites are often used at significantly higher doses – this reduces iron grade and reducibility even further. Thus, several new types of binders have been proposed to replace bentonite clay.In this paper, we present several new binders for iron ore pellets: starch and modified humic acid (MHA). These have been tested alone and in mixtures with dispersants, or else with bentonite clay. Starch, MHA and their mixtures are briefly described below."

Jan 1, 2016

By Boris CARO VARGAS, Bernard Theron

"In early 2014, Nicholson Construction Company was awarded, together with its tunneling sister company Bessac, the Norris Cut Miami Tunnel Project. The 2.5-meters diameter segmental lined tunnel, 1600-meters long, is aimed to replace the existing 54” force main connecting the Waste Water Treatment Plant (WTP) on Virginia Key to Fisher Island. To overcome project challenges such as the highly permeable limestone of the Fort Thomson Karstic Formation (one of the most permeable formation in the World), the project team has developed State of the Art solutions: The TBM was launched with pipe-jacking technique for the first 70-meters and then converted to segment erection mode. It allows substantial schedule savings and drastically reduces the size of the circular launching shaft. The TBM, jointly designed and manufactured by Bessac and Herrenknecht, can convert from slurry to EPB mode within a few minutes. The cutters can be replaced by wet divers thanks to an innovative application in the TBM industry. PRESENTATION OF THE PROJECT The aim of this project is to replace the existing 54-inch force main pipeline which transmitted all sewage collected from Miami Beach, Surfside, Bal Harbour, Bay Harbor, North Bay Village and Fisher Island to the Central District Wastewater Treatment Plant (CDWWTP) to Fisher Island. The existing pipeline consisted of pre-stressed concrete cylinder pipe which is in poor condition in a number of locations and could be subject to sudden failure. An adjacent portion of this existing force main under the Government Cut (North Fisher Island) has already been replaced as part of a previous design-build contract and involved the installation of a 60-inch diameter fiberglass-reinforced mortar pipe installed inside a micro-tunneled casing."

Jan 1, 2016

By V. Bazhko, V. Yahorava

The calcium sulphate waste stream of the wet phosphoric acid process, commonly called phosphogypsum (PG), contains the majority of rare earth elements (REE) initially present in the apatite feedstock. Mainly light and middle REE are present in PG and their total concentration ranges from 0.27% to 0.35% by mass. Worldwide, around 7 billion tonnes of PG have been produced to date at a current growth rate of 150-200 million tonnes per annum. In total, an estimated 21 million tonnes of REE are locked in PG waste dumps around the world. Due to the value of the REE contained in PG dumps a number of processes have been devised for their recovery. The majority of these processes applied complete or partial gypsum dissolution, but were deemed not viable due to high capital and operating costs. Mintek developed an alternative method for the recovery of REE from PG by applying Resin-in-Leach (RIL) technology. This technology was tested on PG sampled from dumps and current arisings from South African phosphoric acid production plants. The extensive testwork program included evaluation of various lixiviants and optimisation of lixiviant additions, optimisation of REE leach and adsorption conditions, batch equilibrium and kinetic adsorption tests, continuous RIL testwork and numerous variability tests. It was found that PG from different sources was highly variable, both in terms of REE recovery as well as physical properties of the material such as viscosity and filterability of the slurry. The recovery of REE varied from 15% to 80% depending on the origin of the samples. A high-level economic study indicated that at a price of >21 $/kg for mixed REE oxide product in conjunction with an overall REE recovery as low as 15% the economics of REE recovery from PG via RIL technology may already be favourable.

Jan 1, 2016

By Ivano Andreis, Georgios Kalamaras, Mario Liti, Sebastiano Pelizza, Filippo Avesani

"THE SS640 AGRIGENTO-CALTANISSETTA PROJECT The Caltanissetta tunnel is part of the works for the construction of the second 28km-long maxi section of the SS 640 motorway of Porto Empedocle, from km 44 to the junction of Imera in Sicilian hinterland. Amongst other major infrastructure works, the €740 million ANAS (Italian national roads and highway administration agency) project consists of four twin tube tunnels three of which are being excavated by conventional means. The longest tunnel, underpasses the Caltanissetta city and has a length of 3.9km under a maximum overburden of 120m. The JV consisting of CMC of Ravenna and TECNIS SpA won the design & built tender in 2010. Construction started in early spring 2012 following the approval of detailed design and later on the approval of design for construction. THE CALTANISSETTA TUNNEL The Design Phase Tender design and detailed design foresaw the construction of 13.4m excavation diameter tunnels that were to be enlarged in a second phase to create, every 600m, 50m-long tunnel sections for emergency parking. During the design for construction project phase the JV proposed to replace the 13.4m tunnel with a 15.08 excavation diameter that incorporated apart from the two 3.75m wide lanes a 3.25m wide continuous emergency lane. This significant tunnel section modification was associated with better road safety conditions, simpler and safer construction procedures, better statics for the tunnel section while in terms of overall cost the solutions were equivalent.Geologic context The tunnel is located in the middle of the geologically known Caltanissetta basin that is intersected by various tectonic structures. The geologic context for the tunnel scale, was defined in collaboration with the University of Catania in early project phases. For almost its entire length the tunnel is excavated in the Terravecchia formation that represents the lower part of the stratigraphic sequence that was formed in the Tortoniano period of Miocene. The quite complex geological model is also characterized by the presence of the so-called Trubi formation that consists of clay and marl clay. Almost 90% of the tunnel traverses formations that are quite similar in terms of excavation behavior. Exception to this are thrust zones and a calcareous stretch of the alignment. This last segment has a length of 200m and was identified since the very beginning as a tunneling challenge due to the combination of very poor geotechnical properties and an important water load."

Jan 1, 2016

"Sink-float analysis is often used to obtain yield-ash and density partition curves in the coal industry. These provide a valuable tool for evaluating the performance of a separation process. However, for dense minerals, obtaining complete grade-recovery and density partition curves is more difficult due to the lack of heavy liquids available with the required densities. This paper examines a potential solution to this problem which is to perform batch fractionation of mineral samples in a laboratory-scale REFLUX™ Classifier using high viscosity fluidising liquids. The REFLUX™ Classifier is a gravity separation unit consisting of a system of parallel inclined channels positioned above a vertical fluidised bed. Operated in semi-batch mode, a charge of particles is fluidised from below and particles up to a certain density are elutriated from the top of the system. The fluidisation rate is then increased incrementally to fractionate the sample at progressively increasing densities. Previous work by Hunter et al. (2014) and Iveson et al. (2015) has shown that this method provides excellent agreement with yield-ash and partition curves for coal, especially when glycerol solutions are used as the fluidising liquid. This approach has now been extended to obtain the grade-recovery and density partition curves of high density mineral samples. This method has the potential to provide the minerals industry with an effective tool to evaluate the performance of unit operations separating at cut points higher than the available heavy liquids.INTRODUCTIONMeasuring efficiency and effectiveness is of key importance in the continuous improvement of mineral processing plants. For density based separation, one way the performance of a process can be evaluated is the measurement of density-based partition curves. Currently, this is done in the coal industry using the sink-float method, where heavy liquids are used to fractionate particles into discrete density intervals. However, with high density minerals such as iron ore, liquids of sufficient density are rare, and in most cases also pose serious health and safety concerns to laboratory operators. Most commercial laboratories do not perform sink-float separations above a density of about 4400 kg/m3, the maximum density of Clerici solution without operating at excessive temperatures (Koroznikova, Klutke, McKnight & Hall, 2007; Rosenblum, 1974)."

Jan 1, 2016

By Stefano Ceccotto, Eugenio Trussoni

"INTRODUCTION Contemporary city is made of layers. Physical structures layers (built fabric, residential, commercial industrial etc. ), infrastructural layers (below and above ground), “green” layers (parks and open spaces), and also informational layers, i.e. connections, links, between sectors of the city and other territories. The “city of layers” concept represents the exercise of “rebuilding the city” per each layer, highlighting those physical built structures that are functional to define a relation. For example, if consider the “connection” relation, the city is re-designed by considering only transportation built structures. The layer obtained in such fashion is hence the “transportation” layer, including below grade infrastructures (subways) and above grade lines (rail, bus, tramways etc.), as below shown in Figure 1.In this sense, the contemporary city is represented by separate constructs assembled together according to a specific functionality (e.g. “connection”). As a consequence, the relation between what is built underground, and the related above-ground development, can be perceived in his most evident appearance. What could happen within the contemporary city if the planning process would begin from below to above and not vice-versa?INTERACTION The question risen in the introduction is strategic when approaching the difficult task of designing (or re-designing) a multi-level organism like the contemporary city. Nowadays, the theme of integration between underground and at-grade master planning has become the subject of many urban renovation projects, where the design process has begun within the transportation layer, underground, and further developed by interacting with at-grade structures already existing or in phase of design.A series of case studies where below/above interaction plays a key role in the project will be further analyzed. Moreover, it is relevant to understand the mechanics of an urban transformation process that originates within the transportation layer and ends up with the design of entire sectors of the city. The Transit Oriented Development approach is a useful tool to clearly understand such transformation process. TOD has become, in particular in the last decade, one of the most effective tools for urban design, in order to solve simultaneously the many different instances related to transit planning, urban design and real estate market."

Jan 1, 2016

By Peter Broad

"Extracting any metal, especially specialty metals and rare earth elements, requires an in-depth analysis of the costs and potential revenue as well as a due diligence study of other stakeholder interests. Rare earth projects are generally in the billion dollar US range or above, and thus failure to accurately predict any loss of revenue caused by impurities within the product or additional effluent treatment costs can destroy an otherwise viable study. Two prime sources of input impurity are considered: impurities in the material feed and from reagents. The effect of these impurities factor on both the product (in reduced revenue) and on residual “tailings” that may incur additional unforeseen costs.INTRODUCTION“Truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident” – Arthur SchopenhauerThe era of unscoped, unbudgeted construction ended about 150 years ago. Today’s engineer must design with confidence; but do so amidst proprietary secrets and unfamiliar pollutants, which present a myriad of interesting challenges. Is it possible to build a viable rare earth plant to a realistic budget, without destroying that which we cherish? Some see this as contradictory but in reality it is the only viable option.WHEN GOOD PROJECTS FAILWithout rare earths the Copenhagen agreement might be null and void. Running a wind turbine with a 30 tonne conventional magnet requires some hefty engineering and prohibitive investment. Despite their ‘Green metal’ applications, production of rare earths have created environmental nightmares, as Folger stated in 2011 when visiting Baotou, or has Jaing Mainheng who has been quoted by Ambrose Evans-Pritchard 6 Jan 2013. This comment is not a criticism of China; the details are from a 2012 white paper published by the Chinese Government that initiated a $6 billion environmental clean-up. Nor is China unique; other plants have had problems as well. There were toxic leaks in the 1990s from Mountain Pass, and the Mitsubishi Bukit Merah Plant (built in Malaysia in 1958) required a $100 million clean-up."

Jan 1, 2016

By Verya Nasri, James Sullivan, Alex Varas

"INTRODUCTION Many major cities in the United States have a combined storm water and sanitary sewer network. Regular rainfall overwhelms the system capacity and results in millions of cubic meters of untreated sewage being dumped into local waterways. One legally mandated solution includes several kilometers of large diameter shallow or deep rock or soil tunnels, a pump station as well as associated collection sewers, diversion structures and drop shafts. In this paper, the basis for design of different system elements including the drop shafts and pump station is explained in detail. Common construction methods used for different type of shafts including tangential vortex and baffle plunge, and also pump station alternatives comprising cavern or various shaft configurations are discussed. DIFFERENT TYPES OF PUMP STATIONS The dewatering pump station serves as the heart of any deep CSO tunnel system and is critical to the goal of reducing CSOs by providing a controlled release of the stored tunnel volume to the wastewater treatment plant. As the major mechanical component of the project, the station will require the greatest attention by operations and maintenance staff. Designing a durable and easily operated pump station requires addressing some major challenges, including the following: • Longevity – equipment, materials of construction, and station environment • Controlling odors • Safety for operators and maintenance personnel • Easy access to equipment • Protection from hydraulic surges Location. Owners face a fundamental decision relative to the location of the pump station, which will affect how these challenges are addressed. The pump station can be built within the tunnel launch shaft or within its own dedicated shaft. This decision is driven by cost and schedule. Use of the tunnel launch shaft may provide owners cost saving opportunities by not having to construct a separate pump station shaft. However, this will likely extend the pump station construction as much as two years until the tunneling has been completed. Furthermore, delays to the tunneling operation would delay the pump station construction work, potentially leading to delay claims. For this reason, it has been more common to utilize a separate pump station shaft on recent CSO tunnel projects (Nasri et al. 2015)."

Jan 1, 2016

By Dan Martz, Stuart Lipofsky, Dean Workman

"The Indianapolis Deep Rock Tunnel Connector (DRTC)—first in a vast network of storm water storage tunnels below Indiana, USA—was a wildly successful endeavor. Crews for the Shea/Kiewit JV drove a 6.2 m Robbins Main Beam TBM to world record rates. The machine achieved 124.9 m/day, 515.1 m/week, and 1,754 m/month in limestone and dolomite rock. The advance rates can be attributed to many factors including ground conditions and knowledgeable crew, but continuous conveyors are also of key importance. The novel conveyor system, manufactured by The Robbins Company, enabled continuous tunneling in a difficult layout that included two 90-degree curves and two S-curves. Spanning 11,777 m in its longest iteration, the system included nine booster drives plus a main drive. A vertical belt moved muck up the 76 m deep shaft to a radial stacker for temporary storage. The system, one of the most complex in North America and the first to operate in 90-degree curves, made swift tunneling possible. This paper will examine the world-class tunneling done at the Indianapolis DRTC and the role of continuous conveyance in reaching high advance rates. The logistics of the system will also be examined as it could apply to future tunneling projects with similarly complex layouts. INTRODUCTION The Indianapolis Deep Rock Tunnel Connector (DRTC) is the first phase of a nearly 28-mile long network of deep rock tunnels being built 76 m beneath the City of Indianapolis, Indiana by Citizens Energy Group. The Deep Rock Tunnel Connector (DRTC) Project is a 12.2 km, 5.5 m diameter tunnel constructed by S-K JV, a joint venture between J.F. Shea Construction and Kiewit Infrastructure Co. The tunnel is a $179 million project and is the first segment and southernmost portion of a deep, large diameter conveyance and storage tunnel system to provide overflow relief during wet weather events. The project is estimated to be completed in 2017 and will initially deliver 204,000 cubic meters of the planned 1 million cubic meters of CSO storage for treatment, as well as provide future connections to other tunnels in the overall system (see Figure 1)."

Jan 1, 2016

By Keh-Jian Shou

"This study adopts and analyzed a shield tunneling case in Taiwan, with a diameter from 5.25m to 6.70m and the smallest radius of curvature 100m, which was constructed in gravel formations as well as a vibration sensitive area. In this case study, a vibration monitoring plan, comprising the sensors inside the shield machine and on the surface, was proposed and performed to provide the vibration data during the construction. In this project, the major vibration reduction considerations were increasing the open ratio of the cutter head (to reduce the cutting function) and reducing the rotational speed of the cutter head. The results of the construction suggest the appropriateness of the above considerations. The findings could provide suggestions to the other similar shield tunneling cases. INTRODUCTION Underground vibrations during shield tunneling are typically isolated and absorbed by the soil. However, a portion of these vibrations may disseminate to the surface. These vibrations are considered micro-vibrations, which generally do not pose a threat to surface structures, and are thus seldom the focus of research. The present project was located in the Hsinchu Science Park where shield excavation bypassed numerous high technology manufacturing plants (e.g., wafer manufacturing plants). The vibrations generated by shield tunneling may affect the vibration-sensitive manufacturing equipment and instruments in these plants, and induce problems in manufacturing processes. Therefore, research to comprehensively understand the characteristics and potential influence of such vibrations is essential. To clarify the characteristics and potential influences of vibrations generated during shield tunneling, the vibration level in the excavation of the Taoyuan International Airport Access (TIAA) Metropolitan Rapid Transit (MRT) Project was examined, as it possesses similar excavation conditions to the present project. The parameters collected from relevant tests were provided as a reference to the firms along the excavation route of the present project to explain the effects of vibrations, and to relevant units for shield machine selection and project execution. No yield problems resulting from shield machine induced vibrations were reported by the firms, and the vibration levels measured in the present project were comparatively lower than those in the TIAA MRT Project. Because the related literature is scarce, this study aims to analyze the collected measurement data and provide suggestions on shield machine selection or designs. Such that we can more properly evaluate and control the impact of shield tunneling induced vibrations in similar projects."

Jan 1, 2016