15 July 2020, Volume 60 Issue 7

    

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SPECIAL SECTION: ROCK MECHANICS AND ENGINEERING PRATICE FOR LARGE HYDROPOWER STATIONS
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  Review on the rock mechanics and engineering practice for large hydropower stations along the downstream section of the Jinsha River

  FAN Qixiang, LIN Peng, JIANG Shu, WEI Pengcheng, LI Guo

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 537-556. https://doi.org/10.16511/j.cnki.qhdxxb.2020.26.011

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  Four large cascade hydropower stations have been constructed or are under construction along the downstream section of the Jinsha River in southwest China. The complex geological conditions and intensive tectonic activity in this region have created a number of challenging rock mechanics problems for these dams. This study used the experience accumulated during the construction of these four hydropower stations, the general layouts of the hydro-power projects, and analyses of the dam foundations to review key problems related to the rock mechanics, the excavation and prevention of large underground caverns, the steep slope stability and precision blasting methods used in these projects. This study also summarizes the problems and key methods used to solve those problems. The successes of these four hydropower stations benefited from a guiding ideology of understanding, utilization, protective monitoring and feedback on the surrounding rock masses during construction period, and an engineering procedure of the excavation, analysis, inspection, and prediction of each rock layer. These successful experiences can guide similar large rock engineering projects.
  
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  Foundation grouting times and uplift control of the Baihetan super-high arch dam

  WEI Pengcheng, LIN Peng, WANG Zhilin, WANG Kexiang, HUANG Jicun

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 557-565. https://doi.org/10.16511/j.cnki.qhdxxb.2019.26.046

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  The grouting time and uplift control of the dam foundation need to be studied to prevent cracking and to ensure the long-term stability of high dams. A theoretical analysis, numerical simulations and an on-site monitoring feedback analysis were used to develop a partitioned equivalent grouting pressure vector and model for complex geological conditions. The model allows better control of the uplift and tensile stresses in the arch dam for better control of the grouting pressure and better chooses of the appropriate grouting times. The equivalent grouting pressure model was developed from construction monitoring data which was used to develop a feedback analysis for optimizing the grouting pressure with the optimal partitioned equivalent grouting pressure vector. The method was applied to the Baihetan dam foundation to verify that the method can accurately judge the uplift condition of the dam foundation and predict the optimal grouting timing. The study provides a valuable tool for selecting grouting times and for controlling the uplift deformation of similar projects.
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  Information model for slope construction in hydropower projects

  TAN Yaosheng, CHEN Wenfu, GUO Zengguang, LIN Ende, LIN Peng, ZHOU Mengxia, LI Junping

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 566-574. https://doi.org/10.16511/j.cnki.qhdxxb.2020.26.004

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  Big data and artificial intelligence methods are combined with information technology methods for engineering construction to develop an information model for slope design during construction of hydropower stations using the BIM technique and an information model. An information model management platform for slope construction was developed for hydropower projects based on intelligent construction theory for sense, analysis, and control with integrated scheduling, quality control and safety management. Results for the construction of the Baihetan Hydropower Project as an example show that the platform provides comprehensive digital management for design results, construction processes and slope construction for large hydropower projects. The system more effectively controls the construction progress, reduces safety risks and provides a comprehensive data archive for the entire slope construction process to improve the construction efficiency and economics.
  
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  Consolidation grouting methods for riverbed rock mass coverings of complex dam foundations

  LUO Guanjun, WANG Kexiang, GUO Zengguang, TAN Yaosheng, AWANG Jiacuo

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 575-581. https://doi.org/10.16511/j.cnki.qhdxxb.2020.26.010

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  Effective surface rock grouting and effective coupling between the concrete-cover grouting and concrete construction are difficult problems, especially with complex geological conditions. This study analyzed the complex geological conditions of the Baihetan dam foundation to develop a consolidation grouting method using the reserved rock mass cover weight, a low pressure thick slurry seal and consolidation grouting by the cover weight by controlling various parameters including the reserved rock mass cover weight, the grouting pressure and concentration, and the grouting method and materials. This method not only avoids the problems of conventional consolidation grouting methods, but also protects the crane beach dam foundation thin layer breccia lava and stabilizes the basalt columnar joints by consolidation grouting bare unloading relaxation. The practice of the riverbed dam section of the Baihetan dam engineering showed that the pass rate of the permeability rate of inspection holes is 99.3%, the high wave velocity of all kinds of lithology measuring point was 91.8%-93.3%, and the low wave velocity measuring point accounted for 2.0%-2.9%, which met the overall design requirements. The results can be applied to the design of consolidation grouting methods in similar projects.
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  Key methods for non-cover-weight consolidation grouting of super high dam foundations

  HUANG Wei, WEI Pengcheng

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 582-588. https://doi.org/10.16511/j.cnki.qhdxxb.2020.26.014

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  This study analyzed the interactions between dam foundation reinforcement and concrete pouring for the foundations of high arch dams without a heavy cover to consolidate the grouting. This study used the Wudongde dam foundation grouting as an example without a heavy cover for the consolidation grouting using the "table closed, shallow encryption, booster, strict monitoring, and little tube" method. This method not only eliminates the interference between the dam foundation consolidation grouting and the concrete pouring, but also guarantees the quality of the non-capped consolidation grouting. The results from the Wudongde Hydropower Station show that the first pass rate of the acoustic wave test was 100% and the water permeability after irrigation met the standard.
AUTOMATION
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  Architecture of a microservice-based flight management system simulation

  LI Qing, FAN Yiping, LI Dachuan, JIANG Xin, LIU Enyu, CHEN Jia

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 589-596. https://doi.org/10.16511/j.cnki.qhdxxb.2019.26.043

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  Modern flight management systems (FMS) are large multi-profession products that are the core of trajectory-based operations (TBO) and the next generation air traffic management systems that have cost and complexity barriers. This study presents a flexible, scalable distributed simulation system for product design, testing, verification, and evaluation. The distributed simulation architecture is based on a service-oriented architecture (SOA), cloud computing and microservice with simulation unit service, simulation orchestration, simulation process monitoring and control. A prototype was implemented with simulation results for an FMS system. The simulation components are encapsulated as microservices or accessed through agents and brokers, and the various FMS system frameworks and simulation tasks can be configured through the simulation orchestration. The FMS product simulation illustrates the system effectiveness and flexibility.
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  Dynamic daylighting simulation facility based on image-data

  BIAN Yu, MA Yuan

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 597-602. https://doi.org/10.16511/j.cnki.qhdxxb.2019.26.038

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  This study presents an artificial sky model to improve simulation accuracies with the ability to include light color information and dynamic daylighting simulations in existing daylight simulation facilities. The image-based lighting simulation method uses sky luminance distribution data to determine the lighting levels. Theoretical analyses and measurements were used to develop a model for the size of the solar disk and its luminance for even the most complex cloudy sky conditions. The model accurately predicts the direct sunlight insolation. Analyses verify the effectiveness of the daylight simulation facility, the design of the luminous part of the hemisphere dome and the control scheme. This facility provides accurate simulations including daylight color information and variable daylight conditions.
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  Thermal-fluid-solid coupled analyses of upstream mechanical seals in pumps

  HUANG Weifeng, PAN Xiaobo, WANG Zixi, GUO Fei, LIU Ying, LI Yongjian, LIU Xiangfeng

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 603-610. https://doi.org/10.16511/j.cnki.qhdxxb.2019.26.039

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  Upstream mechanical seals in pumps have low leakage, low friction and longer service lives. The thermal-fluid-solid coupling in upstream mechanical seals was modeled by solving the flow and energy equations in the fluid domain and the elastic and heat conduction equations in the solid domain to analyze the performance with figure eight shaped grooves. The results show the negative effect of temperature and seal deformation on the sealing at high speeds. The leakage is evaluated for various temperatures, seal deformations, and geometric and working parameters. These results can be applied to optimize the design of upstream mechanical seals in pumps.
CHEMISRY AND CHEMICAL ENGINEERING
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  Measurement and analyses of regional differences in material consumption in China

  FU Yike, CHEN Dingjiang, ZHU Bing, HU Shanying

  Journal of Tsinghua University(Science and Technology). 2020, 60(7): 611-616. https://doi.org/10.16511/j.cnki.qhdxxb.2019.22.031

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  The inequality of regional resources and environments is one of the most pressing problems for China's development. The adjusted raw material consumption method and the Gini coefficient were used to measure and spatially decompose the inequality in per capita material consumption, greenhouse gas emissions and GDP at the regional scale in China during 2010 to 2015. The paper also compared the material consumption with the greenhouse gas emissions and GDP at the regional level to identify inequality patterns. The results show that the inequality pattern of the per capita material consumption in China's provinces is similar to the per capita greenhouse gas emissions in China, where inter-regional and intra-regional components both contribute 25%-30% to the Gini coefficient. The results also show significant differences between China's GDP and global greenhouse gas emissions.