The application of high pressure favors many chemical processes, providing higher yields or improved rates in chemical reactions and improved solvent power in separation processes, and allowing activation barriers to be overcome through the increase in molecular energy and molecular collision rates. High pressures—up to millions of bars using diamond anvil cells—can be achieved in the laboratory, and lead to many new routes for chemical synthesis and the synthesis of new materials with desirable thermodynamic, transport, and electronic properties. On the industrial scale, however, high-pressure processing is currently limited by the cost of compression and by materials limitations, so that few industrial processes are carried out at pressures above 25 MPa. An alternative approach to high-pressure processing is proposed here, in which very high local pressures are generated using the surface-driven interactions from a solid substrate. Recent experiments and molecular simulations show that such interactions can lead to local pressures as high as tens of thousands of bars (1 bar= 1 _ 105 Pa), and even millions of bars in some cases. Since the active high-pressure processing zone is inhomogeneous, the pressure is different in different directions. In many cases, it is the pressure in the direction parallel to the surface of the substrate (the tangential pressure) that is most greatly enhanced. This pressure is exerted on the molecules to be processed, but not on the solid substrate or the containing vessel. Current knowledge of such pressure enhancement is reviewed, and the possibility of an alternative route to high-pressure processing based on surface-driven forces is discussed. Such surface-driven high-pressure processing would have the advantage of achieving much higher pressures than are possible with traditional bulk-phase processing, since it eliminates the need for mechanical compression. Moreover, no increased pressure is exerted on the containing vessel for the process, thus eliminating concerns about materials failure.
Gas hydrates are solid inclusion compounds that are composed of a three-dimensional hydrogen-bonded network of water cages that can trap small gas molecules, such as methane and carbon dioxide. Understanding the rheological properties of gas hydrate crystals in solution can be critical in a number of energy applications, including the transportation of natural gas in subsea and onshore operations, as well as technological applications for gas separation, desalination, or sequestration. A number of experimental and modeling studies have been done on hydrate slurry rheology; however, the link between theory and experiment is not well-defined. This article provides a review on the current state of the art of hydrate slurry viscosity measurements from high- and low-pressure rheometer studies and high-pressure flowloops over a range of different sub-cooling (ΔTsub=Tequil−Texp) and fluid conditions, including for water and oil continuous systems. The theoretical models that have been developed to describe the gas hydrate slurry relative viscosity are also reviewed. Perspectives’ linkage between the experiments and theory is also discussed.
We have adapted and characterized electrolysis reactors to complement the conversion of regional- and community-scale quantities of waste into fuel or chemicals. The overall process must be able to contend with a wide range of feedstocks, must be inherently safe, and should not rely on external facilities for co-reactants or heat rejection and supply. Our current approach is based on the upgrading of bio-oil produced by the hydrothermal liquefaction (HTL) of carbon-containing waste feedstocks. HTL can convert a variety of feedstocks into a bio-oil that requires much less upgrading than the products of other ways of deconstructing biomass. We are now investigating the use of electrochemical processes for the further conversions needed to transform the bio-oil from HTL into fuel or higher value chemicals. We, and others, have shown that electrochemical reduction can offer adequate reaction rates and at least some of the necessary generality. In addition, an electrochemical reactor necessarily both oxidizes (removes electrons) on one side of the reactor and reduces (adds electrons) on the other side. Therefore, the two types of reactions could, in principle, be coupled to upgrade the bio-oil and simultaneously polish the water that is employed as a reactant and a carrier in the upstream HTL. Here, we overview a notional process, the possible conversion chemistry, and the economics of an HTL-electrochemical process.
Enhanced oil recovery (EOR) via carbon dioxide (CO2) flooding has received a considerable amount of attention as an economically feasible method for carbon sequestration, with many recent studies focusing on developing enhanced CO2 foaming additives. However, the potential long-term environmental effects of these additives in the event of leakage are poorly understood and, given the amount of additives injected in a typical CO2 EOR operation, could be far-reaching. This paper presents a summary of recent developments in surfactant and surfactant/nanoparticle-based CO2 foaming systems, with an emphasis on the possible environmental impacts of CO2 foam leakage. Most of the surfactants studied are unlikely to degrade under reservoir conditions, and their release can cause major negative impacts on wildlife. With recent advances in the use of additives (e.g., nonionic surfactants, nanoparticles, and other chemicals) the use of harsh anionic surfactants may no longer be warranted. This paper discusses recent advances in producing foaming systems, and highlights possible strategies to develop environmentally friendly CO2 EOR methods.
Chemical looping combustion (CLC) and chemical looping reforming (CLR) are innovative technologies for clean and efficient hydrocarbon conversion into power, fuels, and chemicals through cyclic redox reactions. Metal oxide materials play an essential role in the chemical looping redox processes. During reduction, the oxygen carriers donate the required amount of oxygen ions for hydrocarbon conversion and product synthesis. In the oxidation step, the depleted metal oxide oxygen carriers are replenished with molecular oxygen from the air while heat is released. In recent years, there have been significant advances in oxygen carrier materials for various chemical looping applications. Among these metal oxide materials, iron-based oxygen carriers are attractive due to their high oxygen-carrying capacity, cost benefits, and versatility in applications for chemical looping reactions. Their reactivity can also be enhanced via structural design and modification. This review discusses recent advances in the development of oxygen carrier materials and the mechanisms of hydrocarbon conversion over these materials. These advances will facilitate the development of oxygen carrier materials for more efficient chemical looping technology applications.
As resource scarcity, extreme climate change, and pollution levels increase, economic growth must rely on more environmentally friendly and efficient production processes. Fuel cells are an ideal alternative to internal combustion (IC) engines and boilers on the path to greener industries because of their high efficiency and environmentally friendly operation. However, as a new energy technology, significant market penetration of fuel cells has not yet been achieved. In this paper, we perform a techno-economic and environmental analysis of fuel cell systems using life cycle and value chain activities. First, we investigate the procedure of fuel cell development and identify what activities should be undertaken according to fuel cell life cycle activities, value chain activities, and end-user acceptance criteria. Next, we present a unified learning of the institutional barriers in fuel cell commercialization. The primary end-user acceptance criteria are function, cost, and reliability; a fuel cell should outperform these criteria compared with its competitors, such as IC engines and batteries, to achieve a competitive advantage. The repair and maintenance costs of fuel cells (due to low reliability) can lead to a substantial cost increase and decrease in availability, which are the major factors for end-user acceptance. The fuel cell industry must face the challenge of how to overcome this reliability barrier. This paper provides a deeper insight into our work over the years on the main barriers to fuel cell commercialization, and discusses the potential pivotal role of fuel cells in a future low-carbon green economy. It also identifies the needs and points out some directions for this future low-carbon economy. Green energy, supplied with fuel cells, is truly the business mode of the future. Striving for a more sustainable development of economic growth by adopting green public investments and implementing policy initiatives encourages environmentally responsible industrial investments.
The rapid growth of lithium ion batteries (LIBs) for portable electronic devices and electric vehicles has resulted in an increased number of spent LIBs. Spent LIBs contain not only dangerous heavy metals but also toxic chemicals that pose a serious threat to ecosystems and human health. Therefore, a great deal of attention has been paid to the development of an efficient process to recycle spent LIBs for both economic aspects and environmental protection. In this paper, we review the state-of-the-art processes for metal recycling from spent LIBs, introduce the structure of a LIB, and summarize all available technologies that are used in different recovery processes. It is notable that metal extraction and pretreatment play important roles in the whole recovery process, based on one or more of the principles of pyrometallurgy, hydrometallurgy, biometallurgy, and so forth. By further comparing different recycling methods, existing challenges are identified and suggestions for improving the recycling effectiveness can be proposed.
Approximately one quarter of the global edible food supply is wasted. The drivers of food waste can occur at any level between production, harvest, distribution, processing, and the consumer. While the drivers vary globally, the industrialized regions of North America, Europe, and Asia share similar situations; in each of these regions the largest loss of food waste occurs with the consumer, at approximately 51% of total waste generated. As a consequence, handling waste falls on municipal solid waste operations. In the United States, food waste constitutes 15% of the solid waste stream by weight, contributes 3.4 × 107t of carbon dioxide (CO2) equivalent emissions, and costs 1.9 billion USD in disposal fees. The levels of carbon, nutrients, and moisture in food waste make bioprocessing into higher value products an attractive method for mitigation. Opportunities include extraction of nutraceuticals and bioactive compounds, or conversion to a variety of volatile acids—including lactic, acetic, and propionic acids—that can be recovered and sold at a profit. The conversion of waste into volatile acids can be paired with bioenergy production, including hydrogen or biogas. This present review compares the potential for upgrading industrial food waste to either specialty products or methane. Higher value uses of industrial food waste could alleviate approximately 1.9 × 108 t of CO2equivalent emissions. As an example, potato peel could be upgraded to lactic acid via fermentation to recover 5600 million USD per year, or could be converted to methane via anaerobic digestion, resulting in a revenue of 900 million USD per year. The potential value to be recovered is significant, and food-waste valorization will help to close the loop for various food industries.
This article analyzes the current research status and development trend of intelligent technologies for underground metal mines in China, where such technologies are under development for use to develop mineral resources in a safe, efficient, and environmentally friendly manner. We analyze and summarize the research status of underground metal mining technology at home and abroad, including some specific examples of equipment, technology, and applications. We introduce the latest equipment and technologies with independent intellectual property rights for unmanned mining, including intelligent and unmanned control technologies for rock-drilling jumbos, down-the-hole (DTH) drills, underground scrapers, underground mining trucks, and underground charging vehicles. Three basic platforms are used for intelligent and unmanned mining: the positioning and navigation platform, information-acquisition and communication platform, and scheduling and control platform. Unmanned equipment was tested in the Fankou Lead-Zinc Mine in China, and industrial tests on the basic platforms of intelligent and unmanned mining were carried out in the mine. The experiment focused on the intelligent scraper, which can achieve autonomous intelligent driving by relying on a wireless communication system, location and navigation system, and data-acquisition system. These industrial experiments indicate that the technology is feasible. The results show that unmanned mining can promote mining technology in China to an intelligent level and can enhance the core competitive ability of China’s mining industry.
Failures are very common during the online real-time monitoring of large quantities of complex liquids in industrial processes, and can result in excessive resource consumption and pollution. In this study, we introduce a monitoring method capable of non-contact original-state online real-time monitoring for strongly coated, high-salinity, and multi-component liquids. The principle of the method is to establish the relationship among the concentration of the target substance in the liquid (C), the color space coordinates of the target substance at different concentrations (L*, a*, b*), and the maximum absorption wavelength (λmax); subsequently, the optimum wavelength λT of the liquid is determined by a high-precision scanning-type monitoring system that is used to detect the instantaneous concentration of the target substance in the flowing liquid. Unlike traditional monitoring methods and existing online monitoring methods, the proposed method does not require any pretreatment of the samples (i.e., filtration, dilution, oxidation/reduction, addition of chromogenic agent, constant volume, etc.), and it is capable of originalstate online real-time monitoring. This method is employed at a large electrolytic manganese plant to monitor the Fe3+ concentration in the colloidal process of the plant’s aging liquid (where the concentrations of Fe3+, Mn2+, and (NH4)2SO4are 0.5–18 mg·L1, 35–39 g·L1, and 90–110 g·L1, respectively). The relative error of this monitoring method compared with an off-line laboratory monitoring is less than 2%.
Rare-earth elements (REEs) are essential metals for the design and development of sustainable energy applications. Recycling these elements from waste streams enriched in them is crucial for securing an independent future supply for sustainable applications. This study compares the mechanisms of mechanical activation prior to a hydrometallurgical acid-leaching process and a solvometallurgical mechanochemical leaching process for the recovery of REEs from green lamp phosphor, LaPO4:Ce3+, Tb3+. After 60 min of processing time, the REE leaching rates showed a significant enhancement of 60% after cycled mechanical activation, and 98% after the combined mechanochemical leaching process. High-resolution transmission electron microscopy (HR-TEM) imaging disclosed the cause for the improved REE leaching rates: The improved leaching and leaching patterns could be attributed to changes in the crystal morphology from monocrystalline to polycrystalline. Reduction of the crystallite size to the nanoscale in a polycrystalline material creates irregular packing of chemical units, resulting in an increase in defect-rich grain boundaries in the crystals, which enhances the leaching process. A solvometallurgical method was developed to combine the mechanical activation and leaching process into a single step, which is beneficial for operational cost. This results in an efficient and simple process that provides an alternative and greener recycling route for lamp phosphor waste.
The environmentally friendly and resourceful utilization of organic waste liquid is one of the frontiers of environmental engineering. With the increasing demand for chemicals, the problem of organic waste liquid with a high concentration of inorganic pollutants in the processing of petroleum, coal, and natural gas is becoming more serious. In this study, the high-speed self-rotation and flipping of particles in a threedimensional cyclonic turbulent field was examined using a synchronous high-speed camera technique; the self-rotation speed was found to reach 2000–6000 rad·s−1. Based on these findings, a cyclonic gasstripping method for the removal of organic matter from the pores of particles was invented. A technological process was developed to recover organic matter from waste liquid by cyclonic gas stripping and classifying inorganic particles by means of airflow acceleration classification. A demonstration device was built in Sinopec’s first ebullated-bed hydro-treatment unit for residual oil. Compared with the T-STAR fixed-bed gas-stripping technology designed in the United States, the maximum liquid-removal efficiency of the catalyst particles in this new process is 44.9% greater at the same temperature, and the time required to realize 95% liquid-removal efficiency is decreased from 1956.5 to 8.4 s. In addition, we achieved the classification and reuse of the catalyst particles contained in waste liquid according to their activity. A proposal to use this new technology was put forward regarding the control of organic waste liquid and the classification recovery of inorganic particles in an ebullated-bed hydro-treatment process for residual oil with a processing capacity of 2 × 106 t·a−1. It is estimated that the use of this new technology will lead to the recovery of 3100 ta−1 of diesel fuel and 647 t·a−1 of high-activity catalyst; in addition, it will reduce the consumption of fresh catalyst by 518 t·a−1. The direct economic benefits of this process will be as high as 37.28 million CNY per year.
A moist plume forms when the flue gas emitted from wet desulfurization equipment exits into the ambient air, resulting in a waste of water resources and visual pollution. In addition, sulfur trioxide (SO3), water with dissolved salts, and particles in the wet flue gas form secondary pollution in the surrounding atmosphere. In this study, a deep purification technology for flue gas involving phase-transition agglomeration and dehumidification (PAD) is proposed. This deep purification technology includes two technical routes: the integrated technology of phase-transition agglomeration and a wet electrostatic precipitator (PAW); and the integrated technology of phase-transition agglomeration and a mist eliminator (PAM). Industrial applications of PAW and PAM were carried out on 630 and 1000 MW coal-fired units, respectively. The results show that the average amount of recycled water obtained from wet flue gas by means of PAD is more than 4 g·(kg·°C)–1. Decreasing the wet flue gas temperature by 1.5–5.3 °C allows 5%–20% of the moisture in the flue gas to be recycled; therefore, this process could effectively save water resources and significantly reduce water vapor emissions. In addition, the moist plume is effectively eliminated. With the use of this process, the ion concentration in droplets of flue gas is decreased by more than 65%, the SO3removal efficiency from flue gas is greater than 75%, and the removal efficiency of particulate matter is 92.53%.
Goethite is a metals-rich residue that occurs during zinc production. The feasibility of metal recovery from goethite has been demonstrated, but is not economically viable on an industrial scale. Therefore, goethite is landfilled with considerable economic costs and environmental risks. The goal of this study is to evaluate the environmental performance of a new valorization strategy for goethite residues from zinc production, with the aims of: ① recovering the valuable zinc contained in the goethite and ② avoiding the landfilling of goethite by producing a clean byproduct. The presented goethite valorization strategy consists of a sequence of two processes: ① plasma fuming and ② inorganic polymerization of the fumed slag. Plasma fuming recovers the valuable metals by fuming the goethite. The metals-free fumed slag undergoes a process of inorganic polymerization to form inorganic polymers, that can be used as a novel building material, as an alternative to ordinary Portland cement (OPC)-based concrete. Lifecycle assessment (LCA) is used to compare the environmental performance of the inorganic polymer with the environmental performances of equivalent OPC-based concrete. The LCA results show the tradeoff between the environmental burdens of the fuming process and inorganic polymerization versus the environmental benefits of metal recovery, OPC concrete substitution, and the avoidance of goethite landfilling. The goethite-based inorganic polymers production shows better performances in several environmental impact categories, thanks to the avoided landfilling of goethite. However, in other environmental impact categories, such as global warming, the goethite valorization is strongly affected by the high-energy requirements of the plasma-fuming process, which represent the environmental hotspots of the proposed goethite recycling scheme. The key elements toward the sustainability of goethite valorization have been identified, and include the use of a clean electric mix, more effective control of the fumed gas emissions, and a reduced use of fumed slag through increased efficiency of the inorganic polymerization process.
The grand challenges of climate change demand a new paradigm of urban design that takes the performance of urban systems into account, such as energy and water efficiency. Traditional urban design methods focus on the form-making process and lack performance dimensions. Geodesign is an emerging approach that emphasizes the links between systems thinking, digital technology, and geographic context. This paper presents the research results of the first phase of a larger research collaboration and proposes an extended geodesign method for a district-scale urban design to integrate systems of renewable energy production, energy consumption, and storm water management, as well as a measurement of human experiences in cities. The method incorporates geographic information system (GIS), parametric modeling techniques, and multidisciplinary design optimization (MDO) tools that enable collaborative design decision-making. The method is tested and refined in a test case with the objective of designing a near-zero-energy urban district. Our final method has three characteristics.①Integrated geodesign and parametric design: It uses a parametric design approach to generate focal-scale district prototypes by means of a custom procedural algorithm, and applies geodesign to evaluate the performances of design proposals. ② A focus on design flow: It elaborates how to define problems, what information is selected, and what criteria are used in making design decisions.③Multi-objective optimization: The test case produces indicators from performance modeling and derives principles through a multi-objective computational experiment to inform how the design can be improved. This paper concludes with issues and next steps in modeling urban design and infrastructure systems based on MDO tools.
Urbanization is a potential factor in economic development, which is a main route to social development. As the scale of urbanization expands, the quality of the urban water environment may deteriorate, which can have a negative impact on sustainable urbanization. Therefore, a comprehensive understanding of the functions of the urban water environment is necessary, including its security, resources, ecology, landscape, culture, and economy. Furthermore, a deep analysis is required of the theoretical basis of the urban water environment, which is associated with geographical location, landscape ecology, and a low-carbon economy. In this paper, we expound the main principles for constructing a system for the urban water environment (including sustainable development, ecological priority, and regional differences), and suggest the content of an urban water environmental system. Such a system contains a natural water environment, an economic water environment, and a social water environment. The natural water environment is the base, an effective economic water environment is the focus, and a healthy social water environment is the essence of such a system. The construction of an urban water environment should rely on a comprehensive security system, complete scientific theory, and advanced technology.
Low-impact development (LID) technologies have a great potential to reduce water usage and stormwater runoff and are therefore seen as sustainable improvements that can be made to traditional water infrastructure. These technologies include bioretention areas, rainwater capturing, and xeriscaping, all of which can be used in residential zones. Within the City of Atlanta, residential water usage accounts for 53% of the total water consumption; therefore, residential zones offer significant impact potential for the implementation of LID. This study analyzes the use of LID strategies within the different residential zones of the City of Atlanta from an ecological perspective by drawing analogies to natural ecosystems. The analysis shows that these technologies, especially with the addition of a graywater system, work to improve the conventional residential water network based upon these ecological metrics. The higher metric values suggest greater parity with healthy, natural ecosystems.
Pavements require maintenance to prevent undue distress or to restore performance; however, pavement maintenance and its impacts do not receive enough attention in many cases, and are either ignored or treated as a low priority. Most current maintenance activities have budget issues and only focus on removing deteriorated pavement sections. Deferred pavement maintenance has impacts on the environment and on society, and may thus affect the costs associated with maintenance. A sustainability rating tool is a good way to list, explain, and evaluate such impacts. Various sustainability rating tools have been developed for pavement; however, pavement maintenance has its own features that are different from those of the new construction, expansion, or reconstruction of pavements. This research project reviews nine sustainability rating tools for pavement, although none of these tools fully describe maintenance features or can be directly applied to evaluate maintenance projects. A new sustainability rating tool is then developed for pavement maintenance; this new tool can be used to evaluate individual projects and raise public awareness about the importance of pavement maintenance. Its details are described, and its use is demonstrated through an example to show the evaluation process and results.
Materials and energy are transferred between natural and industrial systems, providing a standard that can be used to deduce the interactions between these systems. An examination of these flows is an essential part of the conversation on how industry impacts the environment. We propose that biological systems, which embody sustainability, provide methods and principles that can lead to more useful ways to organize industrial activity. Transposing these biological methods to steel manufacturing is manifested through an efficient use of available materials, waste reduction, and decreased energy demand with currently available technology. In this paper, we use ecological metrics to examine the change in structure and flows of materials in the Chinese steel industry over time by means of a systems-based mass flow analysis. Utilizing available data, the results of our analysis indicate that the Chinese steel manufacturing industry has increased its efficiency and sustainable use of resources over time at the unit process level. However, the appropriate organization of the steel production ecosystem remains a work in progress. Our results suggest that through the intelligent placement of cooperative industries, which can utilize the waste generated from steel manufacturing, the future of the Chinese steel industry can better reflect ecosystem maturity and health while minimizing waste.
Geotagging is the process of labeling data and information with geographical identification metadata, and text mining refers to the process of deriving information from text through data analytics. Geotagging and text mining are used to mine rich sources of social media data, such as video, website, text, and Quick Response (QR) code. They have been frequently used to model consumer behaviors and market trends. This study uses both techniques to understand the resilience of infrastructure in Chennai, India using data mined from the 2015 flood. This paper presents a conceptual study on the potential use of social media (Twitter in this case) to better understand infrastructure resiliency. Using featureextraction techniques, the research team extracted Twitter data from tweets generated by the Chennai population during the flood. First, this study shows that these techniques are useful in identifying locations, defects, and failure intensities of infrastructure using the location metadata from geotags, words containing the locations, and the frequencies of tweets from each location. However, more efforts are needed to better utilize the texts generated from the tweets, including a better understanding of the cultural contexts of the words used in the tweets, the contexts of the words used to describe the incidents, and the least frequently used words.
With the rapid growth of vehicle population and vehicle miles traveled, automobile emission has become a severe issue in the metropolitan cities of China. There are policies that concentrate on the management of emission sources. However, improving the operation of the transportation system through apps on mobile devices, especially navigation apps, may have a unique role in promoting urban air quality. Real-time traveler information can not only help travelers avoid traffic congestion, but also advise them to adjust their departure time, mode, or route, or even to cancel trips. Will such changes in personal travel patterns have a significant impact in decreasing emissions? If so, to what extent will they impact urban air quality? The aim of this study is to determine how urban traffic emission is affected by the use of navigation apps. With this work, we attempt to answer the question of whether the real-time traffic information provided by navigation apps can help to improve urban air quality. Some of these findings may provide references for the formulation of urban traffic and environmental policies.
Urban eco-environmental degradation is becoming inevitable due to the extensive urbanization, population growth, and socioeconomic development in China. One of the traffic arteries in Shenzhen is an urban expressway that is under construction and that runs across environmentally sensitive areas (ESAs). The environmental pollution from urban expressways is critical, due to the characteristics of expressways such as high runoff coefficients, considerable contaminant accumulation, and complex pollutant ingredients. ESAs are vulnerable to anthropogenic disturbances and hence should be given special attention. In order to evaluate the environmental sensitivity along this urban expressway and minimize the influences of the ongoing road construction and future operation on the surrounding ecosystem, the environmental sensitivity of the relevant area was evaluated based on the application of a geographic information system (GIS). A final ESA map was classified into four environmental sensitivity levels; this classification indicates that a large proportion of the expressway passes through areas of high sensitivity, representing 11.93 km or 52.3% of the total expressway, and more than 90% of the total expressway passes through ESAs. This study provides beneficial information for optimal layout schemes of initial rainfall runoff treatment facilities developed from low-impact development (LID) techniques in order to minimize the impact of polluted road runoff on the surrounding ecological environment.
This paper summarizes the experience that was gained during the construction of the 15.4 km long Ceneri Base Tunnel (CBT), which is the southern part of the flat railway line crossing the Swiss Alps from north to south. The project consisted of a twin tube with a diameter of 9 m interconnected by crosspassages, each 325 m long. In the middle of the alignment and at its southern end, large caverns were excavated for logistical and operational requirements. The total excavation length amounted to approximately 40 km. The tunnel crossed Alpine rock formations comprising a variety of rock typologies and several fault zones. The maximum overburden amounted to 850 m. The excavation of the main tunnels and of the cross-passages was executed by means of drill-and-blast (D&B) excavation. The support consisted of bolts, meshes, fiber-reinforced shotcrete and, when required, steel ribs. A gripper tunnel boring machine (TBM) was used in order to excavate the access tunnel. The high overburden caused squeezing rock conditions, which are characterized by large anisotropic convergences when crossing weaker rock formations. The latter required the installation of a deformable support. At the north portal, the tunnel (with an enlarged cross-section) passed underneath the A2 Swiss highway (the major road axis connecting the north and south of Switzerland) at a small overburden and through soft ground. Vertical and subhorizontal jet grouting in combination with partial-face excavation was successfully implemented in order to limit the surface settlements. The south portal was located in a dense urban area. The excavation from the south portal included an approximately 220 m long cut-and-cover tunnel, followed by about 300 m of D&B excavation in a bad rock formation. The very low overburden, poor rock quality, and demanding crossing with an existing road tunnel (at a vertical distance of only 4 m) required special excavation methods through reduced sectors and special blasting techniques in order to limit the blast-induced vibrations. The application of a comprehensive risk management procedure, the execution of an intensive surface survey, and the adaptability of the tunnel design to the encountered geological conditions allowed the successful completion of the excavation works.
Long undersea tunnels, and particularly those that are built for transportation purposes, are not commonplace infrastructure. Although their planning and construction take a considerable amount of time, they form important fixed links once in operation. The fact that these tunnels are located under the sea generally involves unique challenges including complex issues with construction and operations, which relate to the lack of intermediate access points along the final route of the tunnel. Similar issues are associated with long under-land tunnels, such as those under mountain ranges such as the Alps. This paper identifies the key issues related to the design and construction of such tunnels, and suggests a potential solution using proven technology from another engineering discipline.
The successful completion of the Zhengzhou–Xi’an high-speed railway project has greatly improved the construction level of China’s large-section loess tunnels, and has resulted in significant progress being made in both design theory and construction technology. This paper systematically summarizes the technical characteristics and main problems of the large-section loess tunnels on China’s high-speed railway, including classification of the surrounding rock, design of the supporting structure, surface settlement and cracking control, and safe and rapid construction methods. On this basis, the key construction techniques of loess tunnels with large sections for high-speed railway are expounded from the aspects of design and construction. The research results show that the classification of loess strata surrounding large tunnels should be based on the geological age of the loess, and be determined by combining the plastic index and the water content. In addition, the influence of the buried depth should be considered. During tunnel excavation disturbance, if the tensile stress exceeds the soil tensile or shear strength, the surface part of the sliding trend plane can be damaged, and visible cracks can form. The pressure of the surrounding rock of a large-section loess tunnel should be calculated according to the buried depth, using the corresponding formula. A three-bench seven-step excavation method of construction was used as the core technology system to ensure the safe and rapid construction of a large-section loess tunnel, following a field test to optimize the construction parameters and determine the engineering measures to stabilize the tunnel face. The conclusions and methods presented here are of great significance in revealing the strata and supporting mechanics of large-section loess tunnels, and in optimizing the supporting structure design and the technical parameters for construction.
The Upper Lillooet River Hydroelectric Project (ULHP) is a run-of-river power generation scheme located near Pemberton, British Columbia, Canada, consisting of two separate hydroelectric facilities (HEFs) with a combined capacity of 106.7 MW. These HEFs are owned by the Upper Lillooet River Power Limited Partnership and the Boulder Creek Power Limited Partnership, and civil and tunnel construction was completed by CRT-ebc. The Upper Lillooet River HEF includes the excavation of a 6 m wide by 5.5 m high and approximately 2500 m long tunnel along the Upper Lillooet River Valley. The project is in a mountainous area; severe restrictions imposed by weather conditions and the presence of sensitive wildlife species constrained the site operations in order to limit environmental impacts. The site is adjacent to the Mount Meager Volcanic Complex, the most recently active volcano in Western Canada. Tunneling conditions were very challenging, including a section through deposits associated with the most recent eruption from Mount Meager Volcanic Complex (~2360 years before the present). This tunnel section included welded breccia and unconsolidated deposits composed of loose pumice, organics (that represent an old forest floor), and till, before entering the underlying tonalite bedrock. The construction of this section of the tunnel required cover grouting, umbrella support, and excavation with a combination of roadheader, hydraulic hammer, and drilling-and-blasting method. This paper provides an overview of the project, a summary of the key design and construction schedule challenges, and a description of the successful excavation of the tunnel through deposits associated with the recent volcanic activity.
The objective of a bridge design is to produce a safe bridge that is elegant and satisfies all functionality requirements, at a cost that is acceptable to the owner. A successful bridge design must be natural, simple, original, and harmonious with its surroundings. Aesthetics is not an additional consideration in the design of a bridge, but is rather an integral part of bridge design. Both the structural configuration and the aesthetics of a bridge must be considered together during the conceptual design stage. To achieve such a task, the bridge design engineer must have a good understanding of structural theory and bridge aesthetics.
Topology optimization is a powerful design approach that is used to determine the optimal topology in order to obtain the desired functional performance. It has been widely used to improve structural performance in engineering fields such as in the aerospace and automobile industries. However, some gaps still exist between topology optimization and engineering application, which significantly hinder the application of topology optimization. One of these gaps is how to interpret topology results, especially those obtained using the density framework, into parametric computer-aided design (CAD) models that are ready for subsequent shape optimization and manufacturing. In this paper, a new method for interpreting topology optimization results into stereolithography (STL) models and parametric CAD models is proposed. First, we extract the skeleton of the topology optimization result in order to ensure shape preservation and use a filtering method to ensure characteristics preservation. After this process, the distribution of the nodes in the boundary of the topology optimization result is denser, which will benefit the subsequent curve fitting. Using the curvature and the derivative of curvature of the uniform B-spline curve, an adaptive B-spline fitting method is proposed in order to obtain a parametric CAD model with the fewest control points meeting the requirement of the fitting error. A case study is presented to provide a detailed description of the proposed method, and two more examples are shown to demonstrate the validity and versatility of the proposed method.
Tissue engineering, which involves the creation of new tissue by the deliberate and controlled stimulation of selected target cells through a systematic combination of molecular and mechanical signals, usually involves the assistance of biomaterials-based structures to deliver these signals and to give shape to the resulting tissue mass. The specifications for these structures, which used to be described as scaffolds but are now more correctly termed templates, have rarely been defined, mainly because this is difficult to do. Primarily, however, these specifications must relate to the need to develop the right microenvironment for the cells to create new tissue and to the need for the interactions between the cells and the template material to be consistent with the demands of the new viable tissues. These features are encompassed by the phenomena that are collectively called biocompatibility. However, the theories and putative mechanisms of conventional biocompatibility (mostly conceived through experiences with implantable medical devices) are inadequate to describe phenomena in tissue-engineering processes. The present author has recently redefined biocompatibility in terms of specific materials- and biology-based pathways; this opinion paper places tissue-engineering biocompatibility mechanisms in the context of these pathways.
An airbag is an effective protective device for vehicle occupant safety, but may cause unexpected injury from the excessive energy of ignition when it is deployed. This paper focuses on the design of a new tubular driver airbag from the perspective of reducing the dosage of gas generant. Three different dummies were selected for computer simulation to investigate the stiffness and protection performance of the new airbag. Next, a multi-objective optimization of the 50th percentile dummy was conducted. The results show that the static volume of the new airbag is only about 1/3 of the volume of an ordinary one, and the injury value of each type of dummy can meet legal requirements while reducing the gas dosage by at least 30%. The combined injury index (Pcomb) decreases by 22% and the gas dosage is reduced by 32% after optimization. This study demonstrates that the new tubular driver airbag has great potential for protection in terms of reducing the gas dosage.