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2020 Vol. 7, No. 2

Cover & Contents
2020, 7(2)
Feature Articles
Economic Analysis of China's Large-scale Hydrogen Energy Supply Chain
Xuanxu HUANG, Jijian LIAN, Wei SHEN, Chao MA
2020, 7(2): 1-13. doi: 10.16516/j.gedi.issn2095-8676.2020.02.001
Introduction The paper aims to calculate the Hydrogen energy economy efficiency. In next decade, Hydrogen will reconstruct the energy structure of China, as a strategic energy. The total cost of Hydrogen gas supplying chain will impact on the society energy cost in future. Therefore, it is of great significance to study the economy of large-scale hydrogen energy supply chain and analyze the supply chain mode of hydrogen energy in the future energy structure to predict the cost of hydrogen production, hydrogen storage, hydrogen transmission, distribution and application in the era of large-scale hydrogen energy, and the trend of future hydrogen energy marketization. Hydrogen has a layered structure in the hydrogen market due to the high storage and transportation cost, versatility and different quality. In this paper, the concept of crude oil equivalent price (POE) will be put forward to analyzes the comparable price of hydrogen energy and normal energy, to find the reasonable range of hydrogen energy price in the future. To solve the supply chain problem is the key issued to obtain low-cost hydrogen energy, the "mainline gate station model" is proposed to distribution of green hydrogen and the long-distance transmission.    Method   Using the Equalization Cost of Hydrogen analysis model (LCOH), the large scale green hydrogen production project including Solar Power Plant, hydrogen generation and pipeline was measured to calculate the hydrogen transmission cost. The economy of hydrogen transmission from large-scale renewable energy was analyzed with the LCOH. Based on different storage and transportation technologies such as gas hydrogen, liquid hydrogen, solid hydrogen, organic hydrogen, pipe hydrogen. The Six-Quadrants Cost Formula was calculated for cost of storage, transportation and unloading of hydrogen supply chain.    Result   The results show that China has a wealth of green hydrogen resources in west forest, with the decline in investment, it is expected that large-scale green hydrogen pipeline transport of the city gate station, the Hydrogen LCOH will be less than 2.0 RMB / Nm³. Due to the low cost, the west green hydrogen will become the main source in the future. At present, hydrogen storage and transportation technologies are including high press gas hydrogen (>20 MPa), liquid hydrogen, methanol, ammonia, organic hydrogen, hydrogen solid hydrogen, pipeline hydrogen. With the increase in scale, the long-distance transportation of hydrogen will be achieved. Under the existed Hydrogen Transportation technologies, the city gate station to the terminal transport, short-distance transmission mode forecast cost will be below 1.2 RMB / Nm³. Assessing the total cost of the hydrogen energy supply chain, the hydrogen energy finally reaches the terminal in the mainline gate station mode is about 3.2 RMB/Nm³. the equivalent price POE is close to the gasoline price. Considering the energy efficiency factor of the fuel cell, hydrogen energy car at 4.0 RMB /Nm³ hydrogen price, has a lower fuel cost than gasoline car.    Conclusion   Therefore, as a strategic energy source, it is feasible to realize the green hydrogen replacement of hydrogen energy in China without subsidies in next decade.
Hydrogen Energy
Technology and Industrialization Progress on Methanol Synthesis from Carbon Dioxide and Hydrogen
Haizhou LIN, Zhibin LUO, Aiguo PEI, Hui YANG, Xiaobo WANG
2020, 7(2): 14-19. doi: 10.16516/j.gedi.issn2095-8676.2020.02.002
Introduction Carbon dioxide hydrogenation to methanol is one of the important pathways to realize the large-scale utilization of carbon dioxide and it will favor the development of CCUS industrial chain.  Method  Thermodynamic characteristics, catalyst development, industrialization progress and technical economics of carbon dioxide hydrogenation to methanol were reviewed.  Result  Cu-based catalysts, precious metal catalysts and In2O3 catalyst shows good catalytic performance in carbon dioxide hydrogenation to methanol, but they still need to be further improved to increase the carbon dioxide conversion rate and methanol selectivity. Despite the rapid progress in technology of carbon dioxide hydrogenation to methanol, which is currently in the pilot stage, it is presently difficult to apply on a large scale due to high cost of hydrogen and low price of methanol.  Conclusion  Fortunately, the price of hydrogen will drop with the booming of the hydrogen industry, and the national carbon trading market will also start, which are beneficial to the blossom of carbon dioxide hydrogenation to methanol.
Plasmonic Effect Promoted Solar Water Splitting for Hydrogen Production
Zhibin LUO, Xiaobo WANG, Aiguo PEI
2020, 7(2): 20-27. doi: 10.16516/j.gedi.issn2095-8676.2020.02.003
Introduction One of the most appealing way to develop clean energy and promote a low-carbon economy is by directly converting sunlight into storable chemcial energy as hydrogen via solar water splitting. This paper summarizes the mechanistic understanding of plasmonic enhancement for photocatalytic water splitting to promote its practical application.  Method  A great deal of attention has been focused on the specific mechanism about the plasmonic effect during the photocatalytic water splitting reaction process, demonstrating the significant roles of plasmonic particles in enhancing sunlight absorption, exploiting entire solar spectrum, promoting photogenerated charge separation, increasing thermodynamic energy of charge carriers, as well as providing active sites for water splitting.  Result  The recent advances and prospects for future developments regarding the promotion of plasmonic effect on solar water splitting for hydrogen production has been presented.  Conclusion  Based on the plasmonic solar water splitting, great efforts on increasing the efficiency and stability of the photocatalysts are needed from researchers with different disciplines to make breakthroughs.
High-efficiency Clean Power Generation System Based on Solid Oxide Fuel Cell
Jing CAO, Xiaobo WANG, Xiang SUN, Zhibin LUO
2020, 7(2): 28-34. doi: 10.16516/j.gedi.issn2095-8676.2020.02.004
Introduction Solid oxide fuel cell (SOFC) is a high-tech product that can convert chemical energy in hydrocarbon fuel into electrical and heat through electrochemical reaction. The advantages of fuel flexibility, high efficiency, high quality heat, silent operation, low emission and modular installation make SOFC one of the effective ways to achieve efficient and clean utilization of fossil energy.  Method  The article explained the principle of SOFC power generation, introduced the domestic and foreign SOFC technology and industrialization status, and analyzed the application scenarios of SOFC-based distributed combined heat and power, combined cycle power generation, and new generation integrated gasification fuel cell cycle (IGFC) power generation system.  Result  Through the SOFC power generation technology route and industrialization research, the existing problems are analyzed, considering China's resource endowment and demand for efficient and clean power generation devices, the future development trends in this field are prospected.  Conclusion  Compared with the domestic and foreign SOFC technology gap, based on the domestic advantage in the core materials of SOFC stacks, the SOFC system integration technology should be strengthened to lay a foundation for the new generation of clean and efficient power generation industry centered on SOFC.
Design of Integrated Offshore Wind Power-hydrogen Energy Monitoring System
Yuan YANG, Liang CHEN, Xiaohu WANG, Wen TAN
2020, 7(2): 35-40. doi: 10.16516/j.gedi.issn2095-8676.2020.02.005
Introduction In order to solve the problem of large-scale offshore wind power consumption after commissioning, the integrated offshore wind power-hydrogen energy monitoring system is proposed.  Method  This article analyzed the system architecture, the requirements of each monitoring subsystem of the onshore hydrogen refueling station, offshore hydrogen production station and offshore wind turbine. In this way, the energy management requirements was stratified.  Result  It can realize the requirements of real-time data collection, sequence control, power generation prediction and planning, distributed power management, and hydrogen production load management.  Conclusion  Therefore, it can meet the control requirements of spontaneous self-use, short-term power storage, long-term hydrogen storage, and controllable load. The scheme is practical and feasible, and is expected to be popularized in engineering applications.
Design and Application of Hydrogen Production by Electrolysising Water in Power Plants and Hydrogen Energy Projects
Peng LI, Jianqun XIAO
2020, 7(2): 41-45. doi: 10.16516/j.gedi.issn2095-8676.2020.02.006
Introduction Hydrogen production by electrolysising water has been widely used in coal-fired, gas and nuclear power plants, and will also be more widely used in hydrogen energy projects supporting renewable energy power plants. It is necessary to discuss the design scheme of hydrogen production system.  Method  In this paper, a coal-fired power plant, wind power generation plant and solar photovoltaic power plant supporting hydrogen energy project were taken as examples. According to the design regulation of relevant standards and codes, the design scheme of the hydrogen production system was elaborated.  Result  The technology of hydrogen production by alkaline electrolysising water is mature, safe and reliable, which can continuously provide hydrogen to meet the requirements of purity and humidity for hydrogen-cooled generators, hydrogen-filling stations and hydrogen users.  Conclusion  This paper aims to provide a reference system design scheme of hydrogen production by electrolysising water for more power plants and hydrogen energy projects.
Solar Power
Key Generic Technologies on National Standard of "Standard for Design of Solar Power Tower Plant"
Jigang XU, Xin LI, Tao QIU, Yi WANG, Xiaohui ZHAO
2020, 7(2): 46-50. doi: 10.16516/j.gedi.issn2095-8676.2020.02.007
Introduction   Solar power tower generation is the mainstream of the first solar thermal power generation demonstration projects in China. In order to promote the progress of science and technology, promote the development of industry, it is necessary to standardize the design of solar power tower plant.      Method     On the basis of summarizing and analyzing the design experience of solar power tower plant, the common principles and key technologies of power plant design were studied, common principles such as scope of application, scale division and design life were given, and the key technical schemes such as solar resource assessment, collector system and equipment, thermal storage system and equipment, automation system, etc. were mainly studied.      Result     The main design scheme of the solar power tower plant is determined, the method of power generation estimation is given, and the "standard for design of solar power tower plant", the first solar thermal power generation design standard in the world, is formulated. The standard provides technical support for the development, construction and operation of domestic solar power tower generation projects, and its main content has risen to the international standard IEC62862-4-1 "General requirements for the design of solar power tower plant".      Conclusion     The standard can provide guidance for the design of solar power tower plant.
Review and Economic Research on Solar Field Design of Solar Tower Plants
Xin LI, Canling XU, Peidong JI, Gang XIAO, Han ZHANG, JIanxiang JIN
2020, 7(2): 51-59. doi: 10.16516/j.gedi.issn2095-8676.2020.02.008
Introduction The paper aims to sort out the contents of the design of solar field of the solar tower plant systematically and to evaluate the impact of solar field design on the economy of the plant. The solar field design is summarized and introduced. The factors affecting solar field efficiency is analyzed and the economic research is conducted.  Method  The design of the collector field was divided into three parts: design of the position and height of the receiver, design of the heliostat layout and design of the road in solar field. The method of decomposing the sub efficiencies of solar field efficiency was adopted and the research was focused on the two main design factors that affect the economy of the solar field.  Result  In this paper, several factors that need to be considered in the design of solar field are summarized and the design conclusions of various factors to improve the efficiency of solar field are listed. Under the current engineering conditions, the larger solar field results in a better the economy of the plant. The influence of the density of the heliostat layout on the economy is obtained.  Conclusion  The conclusions are of great guiding significance and can be used for reference in the design of solar tower plant.
Research on Control System of Tower Concentrated Solar Power Plant
Tao QIU, Canling XU, Wei WANG
2020, 7(2): 60-64. doi: 10.16516/j.gedi.issn2095-8676.2020.02.009
Introduction In order to solve the control problem of Tower Concentrated Solar Power.  Method  Firstly based on the astronomical algorithms for calculating the position of the sun. Secondly, this article studied the main control technology of solar field control system, including system architecture, hardware and software design, feedback measurement program based on image processing. At last, it made an overall design and planning for the whole plant control system, and proposed a signal interface between solar field control system and DCS.  Result  This article invented a high-precision and easy engineering implementation algorithm for heliostats tracking and controlling, which will reduce engineering cost and shorten the construction period.  Conclusion  The research is structural integrity and easy to be realized, it improves accuracy of heliostats tracking and controlling with a lower cost.
Analysis of Structural Design of “Standard for Design of Solar Power Tower Plant”
Hongxing LI, Shaohua HE, Jike DU, Ziyan YI
2020, 7(2): 65-69. doi: 10.16516/j.gedi.issn2095-8676.2020.02.010
Introduction “Standard for Design of Solar Power Tower Plant” (GB 51307) is a comprehensive standard for solar power tower plant. The standard provides a principle for the design of related special structures. In order to understand the standard provisions and commentary completely when using “Standard for Design of Solar Power Tower Plant”, the paper aims to explain and parse the relative regulations of the structure parts of the standard.  Method  Combining with the standard stipulation, the background of standard formulation was elaborated from the aspects of general requirements, seismic design, ground and foundation, receiver tower structure and support structure of molten salt pump. The common structural types of receiver tower, foundation type of molten salt pump and foundation type of heliostat at home and abroad were introduced. The special problems such as structural control index and damping ratio of receiver tower were analyzed and discussed for engineering application.  Result  Through the introduction of the standard background and special structural types, as well as the analysis and discussion of special problems, the design and principle requirements of special structures in tower solar power plant are further understood.  Conclusion  It provides a basis for engineering application of “Standard for Design of Solar Power Tower Plant” and gives some suggestions for further research.
Road Design for Heliostat Field in Solar Power Tower Plant
Jing PENG, Tao SHI
2020, 7(2): 70-74. doi: 10.16516/j.gedi.issn2095-8676.2020.02.011
[Introduction]Road design for heliostat field is the important part in the design of solar power tower plant. To reduce power plant investment and improve the efficiency of heliostat field, road design shall be scientific, effective and reasonable.  Method  In this paper, the roads of heliostat field were divided into four categories: main road, radiation road, peripheral ring road and inter-heliostat road. The factors to be considered in the design were analyzed in detail, and the road layout, structural design and ancillary facilities were studied respectively.  Result  The principles and requirements of the road layout are summarized. It is proposed that the pavement structure design should be based on the functional requirements, economic rationality, construction, local material and maintenance conditions. The pavement structure of inter-heliostat road and the road sign system in heliostat field is suggested.  Conclusion  The paper is used for reference in the road design for heliostat field in the future.
Design Discussion on the Fire Fighting for Solar Power Plant
Kaijun ZHANG
2020, 7(2): 75-80. doi: 10.16516/j.gedi.issn2095-8676.2020.02.012
Introduction For solar thermal power stations, which are different from conventional power plants, develop safe, reliable, economical and reasonable design standards for fire protection facilities to ensure the construction and safe operation of power stations.  Method  Utilize the current national codes and standards to analyze and judge the characteristics of molten salt and heat-conducting oil used in solar thermal power stations, their system equipment and the fire resistance rating of buildings (structures); Analysis and discussion on special fire protection design issues.  Result  Analysis and judgment: the fire hazard of solid monomer molten salt is Class A, the fire hazard of molten salt is E, the fire hazard of heat transfer oil is C, and the fire danger of molten salt and heat transfer oil system building is second-level, and specific fire prevention measures are proposed according to the fire danger level.  Conclusion  The analysis of the fire danger category of the power station using molten salt and heat-conducting oil is in accordance with the current national norms and standards, which provides a reference for the fire protection design of solar thermal power station projects.
Offshore Wind Power
Review of Air-floating Towing Characteristics of Bucket Foundation
Bo LIU, Aiguo PEI
2020, 7(2): 81-90. doi: 10.16516/j.gedi.issn2095-8676.2020.02.013
Introduction The bucket foundation is a kind of emerging environment-friendly offshore wind turbine foundation, with the characteristic of simple construction, high construction efficiency and low comprehensive cost. It has been gradually received attention and recognition from the offshore wind power engineering community. The bottom is an open structure, which can displace an amount of water by the air pressure generated by the compression of the internal air cushion, and form a buoyancy force by forming a water pressure difference between the inside and the outside of the bucket. This self-floating property is a prerequisite for the bucket foundation to perform air-floating towing.  Method  This paper summarized the floating characteristics of air cushion structures at home and abroad, and discussed the related theories, test methods and research results of air flotation structures applied in different fields.  Result  The influence law of air cushion, subdivision form and resonance sloshing on structural dynamic response is analyzed in depth.  Conclusion  The summary analysis of the air-floating towing characteristics of this paper has important practical and theoretical significance for the promotion and application of the bucket foundation.
Research on Several Subsea Cable Protection Systems Based on Different Foundations
Junru DENG, Qingyun ZHANG
2020, 7(2): 91-97. doi: 10.16516/j.gedi.issn2095-8676.2020.02.014
Introduction In order to provide some feasible references for the designs and properties of subsea cable protection systems.  Method  This paper analyzed the mechanical properties, corrosion resistance and structural design of various components of subsea cable protection systems, and proposed the appropriate range of these values by calculations and models. Three mainstream forms of subsea cable protection systems and their components like centralizer, bending restrictor, bending stiffener and fixing device were analyzed from the perspectives of offshore foundations, material compositions, microstructures, cost control, and failure reasons, which also combined with American API standards and global researches.  Result  The results of the study show that the pulling resistance of the centralizer should be greater than 35 kN, and the tensile strength of the material for bend restrictors should be greater than 45 MPa.  Conclusion  If the material properties and structural designs of the components meet these references, the failure frequency of these components can be reduced during installation and service. This paper suggests that the references for designs and properties are feasible, which can provide reasonable suggestions for research and production of submarine cable protection manufacturers.
Research on Array Submarine Cables in Large Offshore Windfarm
Dongling CUI, Chun JIANG, Zhongqiu SHI, Bin LIU, Hongda SUN
2020, 7(2): 98-102. doi: 10.16516/j.gedi.issn2095-8676.2020.02.015
[Introduction]Since 2017, offshore wind power in Guangdong province has entered a period of rapid development. As the development of shallow water windfarms tends to be saturated, the construction of large-scale offshore windfarms in deep water areas is about to start. The array submarine cable is an important link in the whole design process of offshore wind power. The array cable connecting the WTG with the offshore substation can effectively reduce the power loss, the initial investment of the project and improve the reliability of operation through reasonable design. In view of the transformation from conventional offshore windfarm to large-scale offshore windfarm, the design of Array submarine cable also needs to be adjusted simultaneously.    Method   Based on this, this paper discussed the possibility of using 66 kV submarine cable in large offshore windfarms with technological and economic analysis.    Result   After comparative analysis, when the WTG capacity reaches 10 MW or more and the wind farm's overall installed capacity reaches 1 000 MW, the technical and economic effects of 66 kV array system is obviously better than that of the current 35 kV system.    Conclusion   Although there is no real 66 kV submarine cable case in the current domestic offshore windfarm, with the increasing of offshore windfarm capacity, China's offshore wind array system is bound to move like the UK, Germany, toward a higher voltage class direction.
Experimental Study on Scour Characteristics and Protection Measures for Monopile on Sandy Coast
Mingjun BI, Jinchao LIU, Rong SU, Hongqing WANG, Sha LIU
2020, 7(2): 103-111. doi: 10.16516/j.gedi.issn2095-8676.2020.02.016
Introduction Constructing the proper wind turbine foundation is important during the construction of offshore wind farm, and the monopile has been one of the main structures for the wind turbine foundation in recent years. However, the local scour problem for the monopile under marine environment has significant influence on the stability of the wind turbine structure.    Method   In this paper, for one actual wind farm project on sandy coast, the physical model tests were conducted for the local scour of the monopile for different water levels and pile diameters to analyze the effect of wave and current on the scour depth, to study the scour area and depth under the action of combined wave and current, and the protection effect of the sand blanket and sandbag.    Result   The result showed that, for the two monopiles (diameters of 7.0 m and 6.5 m), the locations of maximum scour depth are both at the upstream face, and the maximum scour depth is about 0.8~0.9 times of the pile diameter.    Conclusion   The measure of laying sand blankets without overlapping and filling scour pits with sandbags can protect the bottom around the pile foundation very well, which can provide references for similar engineering scour test and engineering design.
A New Technology Research for Scour Protection of Offshore Wind Turbine Foundation
Qingdong HE, Jiangong QI
2020, 7(2): 112-121. doi: 10.16516/j.gedi.issn2095-8676.2020.02.017
Introduction With the rapid development of offshore wind power in China, large diameter monopile foundation is be widely used. At the same time, the scour of foundation is becoming more and more serious. Therefore, to select a reasonable and suitable scour prevention scheme is of great significance for offshore wind farms' economic benefits and stable operation in the a long-term.  Method  Various scour protection methods for offshore wind farms have been presented in this paper. Scour development and various protection measures have been examined. The principles, parameters, design and construction plans of using chemically solidified sediment on an offshore wind project have been analyzed in this work.  Result  It has been shown that chemically solidified sediment improved the scour protection around tested monopile foundations at the wind farm site after two-year vessel based scanning and diver investigation.  Conclusion  Chemically solidified sediment shows great potential for scour protection at offshore wind farm sites with similar conditions.
Preliminary Discussion on the Ecological Development Feasibility of "Offshore Wind Power + Ocean Ranch" in Yangjiang, Guangdong
Jueting MO, Guowei SONG, Lang SONG
2020, 7(2): 122-126. doi: 10.16516/j.gedi.issn2095-8676.2020.02.018
Introduction The combination of ocean ranch and offshore wind power is a typical case of the efficient integrated development of modern agriculture and new energy industry. This paper makes a preliminary discussion on the feasibility of the ecological development of "offshore wind power + ocean ranch" in Yangjiang, Guangdong, which responding to the national policy of "three-dimensional use of sea space and maximum utilization of resources" and relieving the supply pressure of aquatic resources in port waters.    Method   According to the methods of monitoring and analysis of water and waste water and the specifications for marine monitoring, the chlorophyll α and primary productivity as well as the species of marine organisms in offshore wind power area of China Three Gorges Corporation in Yangjiang were counted and analyzed by means of ultraviolet visible spectrophotometer, stereomicroscope, biomicroscope, etc.    Result   It showed that the average value of chlorophyll α content was 1.79 mg / m3 in the surveyed sea area, the average value of primary productivity was 353.05 mg·C/(m2·d). Besides, There are 4 phyla and 77 species of phytoplankton, 11 phyla and 76 species of zooplankton, 5 phyla and 31 species of macrobenthos, 5 phyla and 43 species of intertidal organisms, and 3 phyla and 37 species of nekton.    Conclusion   The sea area of the offshore wind power has high primary productivity, which is also rich in phytoplankton and zooplankton, large benthic organisms, intertidal organisms, nekton, etc. Thus, it has ecological foundation and advantages of the integrated development of "offshore wind power + ocean ranch", and also has great potential for fishery resources and the feasibility of ocean ranch construction.
Nuclear Power Technology
Control Strategy of Start/Stop and Feed Water System of New Type Nuclear Power Plant
Yusui LIU
2020, 7(2): 127-131. doi: 10.16516/j.gedi.issn2095-8676.2020.02.019
Introduction By means of research,analysis and induction,the control strategies of unit start/stop,feed water and bypass are obtained .  Method  Referring to the experience of the project, referring to the advanced design concept of conventional island of nuclear power plant and thermal power unit,the equipment of thermal systems of the plant would be optimized, and the control strategy of them would be optimized accordingly. It is mainly considered to the optimization of the control strategy of "startup, shutdown and bypass system" and "feed water and high-pressure heater system" in this paper.  Result  Having 2 schemes in the control strategy of unit start-up and shutdown , having 5 schemes in the control strategy of feed water and having 3 schemes in the control strategy of bypass.  Conclusion  Scheme I of 2 schemes of "unit start stop control strategy" has been adopted,which is simpler, less coupling than scheme II, and more reasonable in economy. Scheme II (header control) scheme of 5 schemes of "feed water system control strategy" has be adopted, which is reasonable, economical and safe for system operation; Scheme I of 3 schemes of "bypass control strategy" has be adopted, which is economical and has perfect protection control logic.
Study on Probabilistic Safety Analysis for Service Water System of Nuclear Power Plant
Linggang ZENG, Bo LI, Jun ZHAO,
2020, 7(2): 132-140. doi: 10.16516/j.gedi.issn2095-8676.2020.02.020
Introduction The service water system as the ultimate heat sink is of great significance for the operation and accident mitigation of nuclear power plants.    Method   In this paper, the fault tree was built to model the full power and shutdown modes of the investigated plant under cold and non-cold weather conditions respectively, and then to assess the reliability of service water system as an accident mitigation measure. The Monte Carlo method was used to analyse the operability of the system as an initiating event. Relationships between equipment failure rate, maintenance cycle and the annual average unavailability were also attained via sensitivity analysis.    Result   Quantitative results show the failure rates of service water system for different mission time, particularly under the conditions of non-cold weather at full power the failure rates are 1.47E-01 per year and 4.10E-04 per 72 hours (mission time in accident mitigation process), and at shutdown mode the corresponding failure rate is 6.45E-03 per 96 hours. The frequency of the loss of service water is about 2.0E-03 per year and the annual average unavailability time of the system is about 3.4 hours.    Conclusion   The results suggest that seawater pretreatment system has more significant influence on the unreliability of service water system, of which the operation failure of electric isolation valve at the main pipeline is the dominant contributor due to having no redundant design. In addition, shortening regular maintenance cycle will be a more effective and operable way to reduce the annual average unavailability time compared with reducing the failure rates of components.
Municipal Transportation
Numerical Simulation and Construction Control of Deep Foundation Pit Support Adjacent to Urban Rail Station
Zhanzi GAN, Yuming ZHANG
2020, 7(2): 141-147. doi: 10.16516/j.gedi.issn2095-8676.2020.02.021
Introduction Urban rail is the most important part of the integrated transportation system, which requires an extremely high degree of deformation control. For a long time, it is a key and difficult work that the adverse effects of bearing platform pile are avoided or reduced because of external operations adjacent to the deep foundation pit and the normal use and operation of the track structure is ensured.    Method   A deep foundation pit adjacent to Qianshan station of Guangzhou Zhuhai intercity rail transit was taken as an example, the difficulties, deformation requirements and many engineering problems encountered in the process of deep foundation pit excavation were analyzed by means of geotechnical test, numerical simulation, empirical analysis and field monitoring, the influence of deep foundation pit excavation on bearing platform pile and the deformation characteristics of deep foundation pit were studied.    Result   The research results show that: the deformation indexes of bearing platform pile of the urban rail station calculated and monitored actual are less than the allowable values, which meet the deformation requirements and construction control requirements of the bearing platform pile of the urban rail station; it is proved to be safe, reliable, scientific, reasonable and practical that the supporting scheme of the underground continuous wall + three internal supports and the other sections adopt the row pile + three internal supports; the construction control measures proposed effectively solve many engineering problems such as difficult construction control, strict deformation requirements and complex site conditions.    Conclusion   The reasonable support scheme, reliable numerical analysis, effective construction control measures and research methods and ideas in this paper can provide reference for similar engineering problems.
Effect of Soft Foundation Embankment Widening on Mechanical Characteristics of Piles in the Original Embankment
Xixian CHEN, Jia NI, Linwei WANG, Luanluan XUE
2020, 7(2): 148-156. doi: 10.16516/j.gedi.issn2095-8676.2020.02.022
Introduction   The increasing traffic and the increasingly tight construction cause the roads to be widened and rebuilt. In order to further study the stability of the embankment, the change of the mechanical characteristics of the pile under the original embankment is analyzed when the soft foundation embankment is widened.      Method     After verifying the centrifuge model,a three-dimensional numerical model of the widened embankment and the original embankment was established using Abaqus. Based on the comparative analysis, the influence of gravity, deformation modulus, strength parameters of widened embankment on the mechanical characteristics, deformation behavior and failure mode were carried out.      Result     The numerical simulation results show that the piles under the embankment had different contributions to anti-sliding. The piles close to the slope are mainly subjected to bending and shearing, and the piles far away from the slope are mainly affected by the axial force. The weight of the widened embankment affects the mechanical characteristics of the pile in the original embankment: the main performance is that the bending moment and shearing for piles in the original embankment reduced, and the axial force increased; the displacement of piles in the original embankment increased, in which the vertical displacement increment near the original slope foot is the largest and the largest lateral one is located in the middle of the original embankment. The soil weight of the widened embankment significantly affects the vertical displacement of the original embankment, but its deformation modulus and strength parameters almost have no obvious effect. After the embankment is widened, the mechanical characteristics of the pile in the original embankment change under the load. The potential failure mode is changed from bending-shear zone, bending zone and compression zone to bending zone and compression zone.      Conclusion     The model can verify the centrifuge test results, and the results can provide guidance for the stability analysis of embankment widening.