As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake ...As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake （Intake No. 3） located in Lake Mead. The project included a 185 m deep shaft, 4.7 km tunnel under very difficult geological conditions, and marine works for a submerged intake. This paper presents the experience that was gained during the design and construction and the innovative solutions that were developed to handle the difficult conditions that were encountered during tunneling with a dual- mode slurry tunnel-boring machine （TBM） in up to 15 bar （l bar = l0s Pa） pressure. Specific attention is given to the main challenges that were overcome during the TBM excavation, which included the mode of operation, face support pressures, pre-excavation grouting, and maintenance; to the construction of the intake, which involved deep underwater shaft excavation with blasting using shaped charges; to the construction of the innovative over 1200 t concrete-and-steel intake structure; to the placement of the intake structure in the underwater shaft; and to the docking and connection to an intake tunnel excavated by hybrid TBM.展开更多
In this Opening Session of the 2nd Global Grand Challenges Summit, the distinguished speakers before me have already done a great deal to set the scene and lay out some of the big issues and possible ways forward. No ...In this Opening Session of the 2nd Global Grand Challenges Summit, the distinguished speakers before me have already done a great deal to set the scene and lay out some of the big issues and possible ways forward. No doubt we will hear more about the astounding developments we are seeing in information commu- nications technology （ICT） and other technologies in many sectors and of the opportunities they bring to help tackle our grand chal- lenges. And if I look through the prism of my own sector-design engineering in the built environment-I see exactly the same thing： Rapid advances in our thinking are taking place at dizzying speeds. Much of that is being driven by interdisciplinary collab- orations ranging well beyond the orbit of traditional engineering and construction.展开更多
This paper presents a new perspective for engineers when planning, designing, and managing transportation systems-as well as for those restoring and replacing ageing infrastructure. It provides evidence on how taking...This paper presents a new perspective for engineers when planning, designing, and managing transportation systems-as well as for those restoring and replacing ageing infrastructure. It provides evidence on how taking a ＂human＂ approach to trans- port will enable engineers to find smarter ways to move people and goods across cities, countries, and continents. Human-cen- tered mobility puts the user directly at the heart of design and decision making. By adopting this approach, we can create effi- cient and resilient transport solutions that are mutually beneficial for both passengers and operators and which shape better cities and communities.展开更多
After several instances of sub-synchronous oscillation(SSO)events occurred at wind farms(WFs)with Type-4 wind turbine generators(Type-4 WTGs),the phenomenon has attracted wide attention.The emerging SSO events observe...After several instances of sub-synchronous oscillation(SSO)events occurred at wind farms(WFs)with Type-4 wind turbine generators(Type-4 WTGs),the phenomenon has attracted wide attention.The emerging SSO events observed in Type-4 WTG-based WFs are more complex than those previously observed in thermal power plants or Type-3 WTG-based WFs.The SSO(for example,occurred in Hami Type-4 WTG-based WF,China),could be triggered without the involvement of series compensation in the transmission system.Firstly,this paper discusses and summarizes the previous definitions and classifications,and an improved SSO classification is proposed by supplementing the conventional IEEE classification in the view of Type-4 WTG-related SSO.Secondly,an overview of identification methods for SSO sources and the applicable scope of these methods is evaluated.Then,mitigation and protection measures available for addressing the Type-4 WTG-related SSO are comprehensively reviewed.In addition,lessons learned from real-world SSO events,stakeholders’perspectives,as well as challenges and potential further study of the Type-4 WTGrelated SSO are discussed.This review aims to enhance the understanding of the SSO associated with Type-4 WTGs and contribute to the development of effective solutions to mitigate the phenomenon in power systems.展开更多
文摘As a result of a sustained drought in the Southwestern United States, and in order to maintain existing water capacity in the Las Vegas Valley, the Southern Nevada Water Authority constructed a new deep- water intake （Intake No. 3） located in Lake Mead. The project included a 185 m deep shaft, 4.7 km tunnel under very difficult geological conditions, and marine works for a submerged intake. This paper presents the experience that was gained during the design and construction and the innovative solutions that were developed to handle the difficult conditions that were encountered during tunneling with a dual- mode slurry tunnel-boring machine （TBM） in up to 15 bar （l bar = l0s Pa） pressure. Specific attention is given to the main challenges that were overcome during the TBM excavation, which included the mode of operation, face support pressures, pre-excavation grouting, and maintenance; to the construction of the intake, which involved deep underwater shaft excavation with blasting using shaped charges; to the construction of the innovative over 1200 t concrete-and-steel intake structure; to the placement of the intake structure in the underwater shaft; and to the docking and connection to an intake tunnel excavated by hybrid TBM.
文摘In this Opening Session of the 2nd Global Grand Challenges Summit, the distinguished speakers before me have already done a great deal to set the scene and lay out some of the big issues and possible ways forward. No doubt we will hear more about the astounding developments we are seeing in information commu- nications technology （ICT） and other technologies in many sectors and of the opportunities they bring to help tackle our grand chal- lenges. And if I look through the prism of my own sector-design engineering in the built environment-I see exactly the same thing： Rapid advances in our thinking are taking place at dizzying speeds. Much of that is being driven by interdisciplinary collab- orations ranging well beyond the orbit of traditional engineering and construction.
文摘This paper presents a new perspective for engineers when planning, designing, and managing transportation systems-as well as for those restoring and replacing ageing infrastructure. It provides evidence on how taking a ＂human＂ approach to trans- port will enable engineers to find smarter ways to move people and goods across cities, countries, and continents. Human-cen- tered mobility puts the user directly at the heart of design and decision making. By adopting this approach, we can create effi- cient and resilient transport solutions that are mutually beneficial for both passengers and operators and which shape better cities and communities.
文摘After several instances of sub-synchronous oscillation(SSO)events occurred at wind farms(WFs)with Type-4 wind turbine generators(Type-4 WTGs),the phenomenon has attracted wide attention.The emerging SSO events observed in Type-4 WTG-based WFs are more complex than those previously observed in thermal power plants or Type-3 WTG-based WFs.The SSO(for example,occurred in Hami Type-4 WTG-based WF,China),could be triggered without the involvement of series compensation in the transmission system.Firstly,this paper discusses and summarizes the previous definitions and classifications,and an improved SSO classification is proposed by supplementing the conventional IEEE classification in the view of Type-4 WTG-related SSO.Secondly,an overview of identification methods for SSO sources and the applicable scope of these methods is evaluated.Then,mitigation and protection measures available for addressing the Type-4 WTG-related SSO are comprehensively reviewed.In addition,lessons learned from real-world SSO events,stakeholders’perspectives,as well as challenges and potential further study of the Type-4 WTGrelated SSO are discussed.This review aims to enhance the understanding of the SSO associated with Type-4 WTGs and contribute to the development of effective solutions to mitigate the phenomenon in power systems.
