01 October 2022, Volume 39 Issue 10

    

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  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 0-0.

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SPECIAL CONTRIBUTION
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  Relationship of Fracture and Strength with Stability of Expansive Soils

  GONG Bi-wei

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 1-7. https://doi.org/10.11988/ckyyb.20220271

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  Stability factors, failure mechanism and strength characteristics of expansive soil slope are expounded in this paper from aspects of fractures, strength characteristics and failure mode with the middle route project of South-to-North Water Diversion, North Hubei water transfer project, water diversion from Yangtze River to Huaihe River and other large-scale water diversion projects as research background.Fractures in expansive soils can be classified as swelling and shrinking type and non-swelling and shrinking type, of which the latter is protogenesis, and the former belongs to secondary fractures generated by dry-wet cycles.Rainfall and strength reduction are major factors of shallow slide of most expansive soil slopes, while the dip direction, dip angle and strength of non-swelling nor shrinking cracks dominate the overall stability of expansive soil slopes.The instability of expansive soil slope can be summarized as shallow slide induced by expansive deformation and global slide controlled by fracture strength.Therefore, the expansive deformation and fracture distribution should be taken into account in stability analysis, and the strength parameters of expansive soil cannot be regarded simply as the comprehensive strength, but need to be depicted using soil mass strength parameters and fracture strength parameters according to actual geological conditions.On this basis, expansive slopes should be treated in accordance with its specific failure mechanism.
WATER RESOURCES
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  Calculating Submarine Groundwater Discharge in the East Coast of Liaodong Bay Based on the Improved Radium Mass Balance Model

  GUO Qiao-na, LI Meng-jun, ZHAO Yue, DOU Zhi, ZHOU Zhi-fang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 8-15. https://doi.org/10.11988/ckyyb.20210629

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  Submarine groundwater discharge (SGD) represents an essential part of the global water cycle and one of the vital ways to transport various chemical substances such as nutrients to the ocean.The influences of recirculated seawater (RSGD) on water body refresh time, SGD, and the flux of nitrogen and phosphorus nutrients in Yingkou sea area in the eastern part of Liaodong Bay were investigated by establishing and improving the radium mass balance model with natural radium isotopes (²²⁴Ra and ²²⁸Ra) as tracers.The water refresh time calculated by the radium mass balance model is 9 days while by the improved radium mass balance model 14.35-18.11 days.The SGD flux in the traditional model is (3.01-3.51)×10⁸ m³/d while in the improved model (3.55-4.39)×10⁸ m³/d.The water refresh time and SGD calculated by the improved model increased by 59.44%-101.22% and 17.94%-25.07%, respectively, compared with those by the traditional model.Moreover, the nitrogen and phosphorus nutrient fluxes from groundwater to the sea are 1.73×10⁸ mol/d and 1.52×10⁹ mol/d, respectively, in consideration of RSGD.In conclusion, RSGD has a remarkable impact on SGD and nutrient fluxes.
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  Impact of Climate Change on the Change of Lake Water Volume in the Hoh Xil Salt Lake Basin

  LI Lin, TAN De-bao, WEN Xiong-fei, WANG Ying, LIU Xi-sheng, WANG Gang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 16-23. https://doi.org/10.11988/ckyyb.20210731

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  Lakes are sensitive indicators of climate change.In the aim of studying the impact of climate change on lake water volume,statistical methods were applied to examine the linear trend and abrupt changes of rainfall,temperature,and evaporation from 1989 to 2018 in the Hoh Xil Salt Lake Basin.Hydrological elements such as lake area were monitored by using multi-source satellite remote sensing technology,and the correlation between lake area and meteorological elements,lake area and lake water volume changes were analyzed.Moreover,the impact of meteorological elements on the changes in lake water volume was quantified by obtaining the composition of the Salt Lake runoff in association with VIC model-simulated runoff and calculated glacier water volume.The differences in the impact of meteorological elements on lake water volume in the basin before and after 2011 were also comprehensively scrutinized.The statistical analysis and quantitative calculation of hydrological models manifest that the annual rainfall and annual average temperature in the Hoh Xil Salt Lake Basin have increased significantly,while annual evaporation has presented a downward trend,all in good correlation with lake area.Lake area is highly correlated with lake water volume,which indirectly reflects the impact of meteorological elements on lake water volume changes.Before 2011,the changes in the water volume of Zhuonai Lake and Salt Lake were mainly affected by rainfall,and the water volume changes in Kusai Lake and Hading Knoll were mainly affected by temperature;from 2011 to 2014,changes in the water volume of the four lakes were mainly affected by rainfall;from 2015 to 2018,the increase in rainfall,the release of water from frozen soil and the increase in groundwater recharge,and the amount of glacial melting water contributed about 34.48%,57.66%,and 7.86%,respevtively,to the expansion of the four lakes.Temperature changes have become the major factor,followed by rainfall,affecting the changes in lake water volume.
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  Runoff Reconstruction in the Source Region of Yangtze River Based on Ice Core Records on the Tibetan Plateau

  SHAO Jun, OUYANG Shuo, GUO Wei, BU Hui, HAN Yong

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 24-30. https://doi.org/10.11988/ckyyb.20220354

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  Runoff in the source region of the Yangtze River has undergone great changes in recent decades.It is of great practical significance to study the characteristics of runoff variation under the background of global warming for understanding the hydrological effects caused by climate change.The evolution of runoff and its relationship with meteorological factors such as precipitation, temperature, and evaporation were analyzed based on measured hydro-meteorological data from 1960 to 2019 at Tuotuo River.The relationship between δ¹⁸O records and ice core accumulations among different ice cores, and the correlation between ice core records and runoff in Tuotuo River were examined.The 10-year moving average runoff series of the Tuotuo River from 1900 to 1960 was reconstructed, and the runoff variation of Tuotuo River over the past century was analyzed.Results revealed a siginificant increase trend of annual runoff of Tuotuo River around 2002.The increase in glaciers and snow melt induced by the sharp rise in temperature is an important cause for the sharp increase in flow rate in the source region of the Yangtze River.The reconstruction of the runoff series of Tuotuo River since 1900 demonstrated that the source area of the Yangtze River had experienced many alternating dry-wet changes, and the runoff variation rules are in general consistent with the three abrupt climate changes in the Tibetan Plateau.The research findings provided a basis for revealing the evolution law and hydrological response of river runoff in the source region of the Yangtze River under climate change.
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  Impacts of Cascade Hydropower Stations on Runoff and Flood Process at Mountain Exit of Heihe River

  REN Xiao-hu, ZHU Yong, ZHENG Yang, WANG Qi-you

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 31-37. https://doi.org/10.11988/ckyyb.20220113

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  The influence of cascade hydropower stations on the runoff and flood process of Yingluoxia hydrological station at the outlet of Heihe River is analyzed by using the double cumulative curve method, MK test method and Gini coefficient method based on the monthly annual runoff, annual maximum peak discharge, flood process of Yingluoxia hydrological station and precipitation in the upper reaches of the Heihe River.Results demonstrate that the construction and operation of cascade hydropower stations in the upper reaches of Heihe River has no large impact on the change of annual runoff, but has a certain impact on the annual distribution of runoff and flood process.After the joint dispatching and operation of the power stations, the regulation and storage of the reservoir in front of the dam has changed the natural runoff process and has a significant impact on the annual distribution of runoff.The annual distribution uniformity showed a transition in 2001 and a significant increasing trend from 2017 to 2020.The artificial rising and lowering of the gate resulted in the straight rising and falling of water level, the elongation of flood process, the expansion of peak flood in the form of steep rise and fall, and the increment of the rise and fall rate and change frequency.The research findings offer theoretical basis for strengthening the scientific operation of hydropower stations, the construction of water ecological civilization and the sustainable development and utilization of hydropower and water resources.
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  Spatial and Temporal Variation Characteristics of Blue and Green Water Resources in the Yangtze River Basin Based on GLDAS-NOAH

  SHI Meng-qi, YUAN Zhe, SHI Xiao-liang, LI Yi, CHEN Fei

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 38-44. https://doi.org/10.11988/ckyyb.20210526

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  The blue and green water resources in the Yangtze River basin (YRB) were simulated by using the GLDAS (Global Land Data Assignment System) Noah hydrological model,and then the distribution of blue and green water resources and their temporal and spatial changes were revealed. Results demonstrate that from 2000 to 2019,the multi-year average blue water resource and green water resource in YRB was 420.24 mm and 686.95 mm,respectively,and the latter was about 1.62 times of the former. Over the past two decades,the blue water resource,green water resource and green water coefficient in the YRB showed insignificant increasing trends,and in particular,the change rate of blue water resource and green water resource was 3.26 mm/a and 2.27 mm/a during 2000-2019,respectively. On monthly scale,the blue and green water resources expanded in July and August,accounting for 29%-32% of the whole year,while shrank in January and February,accounting for 5%-6% of the whole year. On spatial scale,blue water resource distributed in a pattern of higher in the southeast and lower in the northwest,while green water resource higher in the east and lower in the west,and green water coefficient higher in the northwest and lower in the southeast. Scientific and comprehensive evaluation of blue and green water resources can provide scientific basis for optimizing water resources utilization mode and improving water resources utilization efficiency.
WATER ENVIRONMENT AND WATER ECOLOGY
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  Distribution Characteristics of Phosphorus Forms in Water and Sediment of Shengzhong Lake in Summer

  SONG Lin, CHEN Chao, FENG Xiao-yu, YANG Zuan-yun, ZHANG Tuo, XU Fei, ZHANG Fu-bin

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 45-53. https://doi.org/10.11988/ckyyb.20210659

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  The aim of this research is to investigate the phosphorus pollution in the water and sediment of the Shengzhong Lake. We collected water and sediment samples from fifteen sampling sites in the summer (August) of 2019,measured the forms of phosphorus in surface water,interstitial water and sediment,and further analyzed the correlation among various forms of phosphorus. Results revealed that the total phosphorus content in the surface water of Shengzhong Lake ranged from 0.033 mg/L to 0.085 mg/L,and the content of phosphorus in different forms were DTP (61.93%),DOP (40.00%),PP (38.07%),and DIP (21.93%),respectively. The total phosphorus content of interstitial water ranged from 3.49 mg/L to 7.57 mg/L,which is the source of phosphorus in water;however,the orthophosphate accounted for only 1.9%. Total phosphorus content of sediment ranged from 299.04 mg/kg to 1138.69 mg/kg. Five forms of phosphorus in surface sediments were extracted by continuous classification of Psenner,of which Res-P accounted for 44.78% of the total phosphorus content of the surface sediment,followed by NaOH-P occupying 22.92%,and then HCl-P 14.82%,BD-P 13.39%,and NH₄Cl-P 4.09% in sequence. The content of different forms of phosphorus varied in spatial scale. Generally,the total phosphorus content in the northwest of Shengzhong Lake was higher than that in the southeast. The results of correlation analysis showed that the release of phosphorus in sediments was mainly through BD-P,NaOH-P and NH₄Cl-P. No significant correlation was found between orthophosphate in interstitial water and various forms of phosphorus in water body (P > 0.05),and the release potential of phosphorus in sediments was not large in summer.
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  Water Quality Characteristics and Treatment Strategies of Rural Domestic Sewage:Case Study on the Rural Area of Xiamen

  XU Pei-lin, ZHU Mu-lan, ZHANG Zhi-qian

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 54-60. https://doi.org/10.11988/ckyyb.20210696

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  The city of Xiamen and other parts of China are actively promoting the treatment of rural domestic sewage since 2017.It is not only urgent but also important to explore the treatment strategies of rural domestic sewage,while investigating clearly the characteristics of rural sewage quality is a prerequisite.The quality characteristics of rural domestic sewage in the rural area of Xiamen are investigated with 12 sampling sites in the rural areas of four administrative districts outside Xiamen Island.Water quality indicators inclusive of COD,BOD₅,TN,NH₃-N,TP,and pH value varied in the range of 46-408 mg/L,4.9-188 mg/L,7.30-66.7 mg/L,1.50-49.1 mg/L,0.44-3.56 mg/L,and 6.82-8.51, respectively.BOD₅/COD,BOD₅/TN,and BOD₅/TP ranged between 0.22-0.68,0.7-12.1,and 14.7-86.4,of which BOD₅/COD ratios are all larger than 0.2,BOD₅/TN ratios of half of the sampling sites less than 4,and BOD₅/TP ratios of some sampling sites below 20.On such basis,the agricultural irrigation standard is recommended to be taken as the treatment target for the second type of rural areas around Xiamen.Ecological measures such as LID (Low Impact Development) drainage ditch are recommended for ecological treatment and then the treated sewage can be recharged to farmland.The research findings offer strategic reference for domestic sewage treatment in Xiamen and the whole country.
WATER-RELATED DISASTERS
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  Risk Assessment and Rating of Dam-break Flood in Consideration of Disaster Consequences

  MENG Ying, TANG Ling-ling

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 61-65. https://doi.org/10.11988/ckyyb.20210631

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  The risk of dam-break flood is uncertain as affected by environment,load and people.The risk of flood disaster is assessed in consideration of the depth and velocity of flood.The propagation of dam-break flood is simulated by using two-dimensional hydrodynamic model with HEC-RAS software and GIS spatial analysis technology,and the exposure of disaster-bearing bodies are analyzed from flood arrival time and inundation range.The vulnerability of disaster-bearing body is analyzed according to the experimental data of human instability and building stability criteria.Finally,the risk analysis method for dam-break flood and the risk rating standard based on the disaster system theory are proposed to assess the risk of dam failure,classify the risk level of population in dam-break flood inundated area,and to provide technical support for planning and preparing the rescue and migration in dam emergency.
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  Propagation of Landslide Surge in Curved River Channel and Its Interaction with Dam

  PENG Hui, HUANG Ya-jie

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 66-71. https://doi.org/10.11988/ckyyb.20210638

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  As a common geological hazard,reservoir bank landslide would most probably induce surge waves in river if not prewarned in time,endangering river traffic or the safety of nearby water conservancy facilities.The propagation of surge wave induced by the landslide of curved river bank in reservoir and its interaction with downstream dam were simulated by using Flow-3D.A three-dimensional landslide surge model was constructed to verify the validity and accuracy of hydraulic physical model test.The result of the three-dimensional numerical simulation was in good agreement with that of hydraulic physical model test in terms of the water surface height change and the propagation process of the surge.In the mean time,the most dangerous water depth and incident angle conditions were obtained by analyzing the interaction between the dam and the landslide surge under different conditions.Engineering examples demonstrated that the maximum dynamic water head was smaller than the water head of surge height,and reduced along the water depth direction.In such cases,the stress of the dam calculated according to the static maximum water head of the surge is safe.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  XGBoost-LSTM Combinatorial Model with Variable Weight for Dam Deformation Prediction and Its Application

  DENG Si-yuan, ZHOU Lan-ting, WANG Fei, LIU Zhi-kun

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 72-79. https://doi.org/10.11988/ckyyb.20210641

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  A XGBoost-LSTM combinatorial model with variable weight is proposed to more accurately predict dam deformation. First,the XGBoost (eXtreme Gradient Boosting) model and LSTM (Long Short-Term Memory) model are introduced to analyze and predict the dam deformation respectively,and then the results of the two models are combined by using variable weight combination method to obtain the final prediction result. With a concrete gravity dam as a case study,the advantages of XGBoost and LSTM models in dam deformation prediction are demonstrated respectively through comparison with those of random forest,ELMAN and stepwise regression analysis models;furthermore,the prediction effect of the combinatorial model is verified to have enhanced remarkably compared with each of the single model and the equivalent-weighted XGBoost-LSTM combinatarial model. The deformation prediction results are more consistent with the actual engineering situation,thus is well applicable and popularizable.
ROCK-SOIL ENGINEERING
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  Reasonable Offset of Asymmetric Tunnel with Small Clear Distance in Loess Area

  SHAO Zhu-shan, WANG Meng-hui

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 80-87. https://doi.org/10.11988/ckyyb.20210521

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  Xi'an rail transit project is built in the loess area of China. The subway parking line interval is featured with shallow buried depth,small clear distance and asymmetric distribution of sections. To avoid excessive disturbance between the left and right lines during excavation,we need to determine a reasonable stagger distance of the working face. We took the parking line interval of Xi'an Metro Line 8 project as the research background,and dynamically simulated the excavation under different schemes by using FLAC^3D finite difference software. By comparing the simulation results with the actual monitoring data,we verified the correctness of the simulation. We found that the final deformation and stress of surrounding rock was hardly affected by different schemes,but the deformation rate and the extreme value in the process need to be controlled. The longitudinal influence range of tunnel face on excavated soil reached about 3 times the span. When the offset of tunnel face is 2-3 times the span,the deformation rate of surrounding rock can be effectively controlled. When the offset of tunnel is large,the maximum shear stress of surrounding rock increased significantly during excavation,and meanwhile leading to large relative displacement difference between the middle soil column,unfavorable to the stability of surrounding rock. In conclusion,we suggest to reduce the offset of the working face to 30 m to ensure construction safety and improve construction efficiency.
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  Causes and Countermeasures of Large Deformation in a Tunnel with Tertiary Mudstone

  CHI Jian-jun, LIU Deng-xue , DING Xiu-li, HUANG Shu-ling

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 88-96. https://doi.org/10.11988/ckyyb.20211286

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  Large deformation of surrounding rock is one of the major engineering disasters endangering tunnel construction and long-term safety in soft rock tunnel construction.In association with engineering field investigation of significant large deformation and support structure damage,we obtained the main causes and occurrence mechanism of large deformation in the Tertiary mudstone tunnel via deformation monitoring,indoor test and numerical simulation.Results revealed that the plastic deformation caused by tunnel excavation under the condition of low rock strength and the softening effect of groundwater on surrounding rock were major factors triggering the large deformation in the tunnel.The squeezing and expansive deformation of surrounding rock and the inconsistent deformation between different rock strata jointly dominated the failure of the support structure.The Tertiary mudstone tunnel crosses a gully with perennial water flow,coupled with the sand gravel layer with good water permeability in the middle of the tunnel,which significantly increased the water content of surrounding rock after tunnel excavation.The argillization and softening of the Tertiary mudstone led to strength reduction and expansion,which finally resulted in the large deformation of surrounding rock.On this basis,we put forward such countermeasures as improving the steel arch frame,strengthening the longitudinal connection between steel arch frames,adding foot lock anchor pipe of bottom arch,and applying polyethylene slow-release energy dissipation layer between primary support and secondary lining.Field monitoring results demonstrated that the proposed control measures effectively solved the problem of large deformation during the excavation of the Tertiary mudstone tunnel.
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  Dynamic Performance of Construction Waste Soil under Cyclic Loading

  LI Li-hua, HAN Qi-pei, LI Wen-tao, ZHOU Xin-long, TIAN Mi, QIN Lang-ling, SHENG Hong-zhi

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 97-102. https://doi.org/10.11988/ckyyb.20210523

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  The continuous development of national infrastructure gave rise to a large amount of construction and demolition waste.The utilization of construction and demolition waste as a resource is not only economical and environmental friendly,but also relieves environmental pressure.The dynamic properties of construction and demolition waste soil and sand were examined by large-scale indoor dynamic triaxial test.The stress-strain,time history curve,dynamic elastic modulus,and damping ratio were analyzed,and liquefaction was evaluated.Test results demonstrate that the damage dynamic stress of construction and demolition waste is about 1.3 times that of sand.In other words,the bearing capacity of construction waste soil is obviously higher than that of sand.Under cyclic loading,the excess pore water pressure of sand is about 2.5 times that of construction and demolition waste soil;therefore the liquefaction of construction and demolition waste soil is less possible.The dynamic elastic modulus of construction and demolition waste soil is much higher than that of sand,reaching 1.3 times that of sand.In conclusion,construction waste soil has better performance than sand,hence has the potential to replace sand as filling material for road engineering.
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  Silt Characteristics of Immersed Tube Tunnel Foundation Trench at Inland River Intersection

  FU He-lin, DONG Zi-long, HONG Kai-rong, AN Peng-tao, LIN Rui

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 103-108. https://doi.org/10.11988/ckyyb.20220596

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  The siltation of foundation trench has severe impact on the smoothness of immersed tube tunnel and threatens its waterproof performance.The silt characteristics of immersed tunnel foundation trench at the intersection of two rivers are researched by establishing a numerical calculation model.The simulation result is compared with actual monitoring value to verify the applicability of the model,and furthermore to reveal the siltation characteristics of immersed tunnel foundation trench at inland river intersection.Results display small error between the simulated flow velocity and the actual monitored value,verifying that the model is applicable.The silt depth is large in the middle and small in two ends,and large in the upstream while small in the downstream.The siltation varies largely in space,distributing apparently at the trench foot and remarkably on slope crest than at slope toe.The sensitivity of siltation attenuates gradually over time.After the excavation of foundation trench,the silt depth reached 10 cm,which would affect the application of the immersed tunnel.Dredging measures on site are required.
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  Experimental Study on Mechanical Properties of Composite Reinforced Soil with Root System and Grid

  HU Qi-zhi, ZHOU Yong, MA Qiang, TAO Gao-liang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 109-115. https://doi.org/10.11988/ckyyb.20210643

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  Effective ecological slope protection can be achieved by planting ecological plants on slope reinforced by geogrid.The mechanical mechanism of composite reinforced soil consisting plant root system and geogrid is investigated via triaxial consolidation undrained tests on plain soil,root-reinforced soil,grid-reinforced soil,and root-grid composite reinforced soil with the ecological slope protection project of Guangxi Guilong Expressway as the research background.The mechanical properties of the three reinforced soils are also compared.Results demonstrate that both plant roots and geogrids can increase the strength of reinforced soil,while the composite reinforcement combining roots and geogrids has the best effect.Root-geogrid reinforced soil sees an increase by 265.0%,101.0%,and 33.2% in its cohesion,respectively,compared with plain soil,root-reinforced soil,and geogrid-reinforced soil.Under the optimum geogrid layout,the cohesion of root-geogrid reinforced soil first increases and then reduces with the rising of root content,and reaches its maximum when root content is 0.5%.Analysis on the triaxial test curves of the reinforced soils reveal that the stress-strain relationship of the three reinforced soils is in accordance with the Duncan-Chang model,and the Duncan-Chang model parameters of the reinforced soils are obtained and verified through test data.
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  Experimental Investigation on Treatment of Soft Soil Foundation by Prebored Dynamic Replacement

  ZHAO Yong-xiang, LIU Bo, GAO Yu-jie, WANG Zhi

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 116-120. https://doi.org/10.11988/ckyyb.20210665

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  Dynamic replacement,as a treatment method for soft soil foundation,has some shortcomings such as the gap between the replacement columns and the basement,large post-construction settlement,and low construction efficiency. In view of this,a dynamic replacement method with prebored filling is proposed to enhance the bearing capacity of foundation and reduce the post-construction settlement by tamping the prebored columns filled with materials under high energy level. The method is verified feasible through plate loading test,heavy dynamic penetration test and water filling and preloading test after tamping,and finally successfully applied to the whole soft soil foundation site. The number of dynamic sounding blows after tamping increased by over 260%,the bearing capacity of composite foundation reached 280 kPa,and the maximum settlement of tank foundation and the settlement difference of adjacent measuring points are far less than the requirements of specification. The successful application of this method serves as reference for the treatment of similar foundation.
HYDRAULIC STRUCTURE AND MATERIAL
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  Effects of Steel-PVA Hybrid Fiber on Shear Performance of Self-compacting Concrete Beams

  LI Qing-wen, CAO Hang, YANG Lu, WANG Xue-zhi, LIU Hua-xin

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 121-127. https://doi.org/10.11988/ckyyb.20210726

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  The shear behavior of self-compacting concrete beams with hybrid steel fiber (SF)-polyvinyl alcohol (PVA) fiber was studied through tests with different volumetric dosages of the SF-PVA hybrid fiber,different hybrid ratios of the two fibers,and varied spacing of stirrups.Test results manifested that adding SF or PVA fiber into concrete beams could effectively restrain the generation and propagation of cracks and improve the shear capacity of beams.The specimen with stirrup spacing of 150 mm,volumetric dosage of 1% and hybrid ratio of 1∶1 has the maximum cracking load and shear capacity.Under the same volumetric content and hybrid ratio,reducing the stirrup spacing could remarkably reduce the ultimate load value of the beam,but has little effect on the crack load value of the beam.In addition,a BP neural network model for strength prediction was established with SF's volumetric content,PVA fiber's volumetric content,and stirrup spacing as input layer and ultimate shear as output layer.Ultimate shear force was fitted and the prediction result was accurate.
INFORMATION TECHNOLOGY APPLICATION
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  Remotely Sensed Monitoring of Sand Mining in Reservoir by Using Dominant Wavelength of Water Color

  QIN Yan, JI Hong-xiang, HUANG Ben-sheng, CHEN Liang-xiong, ZHOU Yu, YANG Jing-xue

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 128-133. https://doi.org/10.11988/ckyyb.20210545

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  In remotely sensed monitoring of sand mining in river channel,the area with high concentration of suspended solids in water body is usually classified as suspected area according to empirical threshold. The segmentation threshold is difficult to be automatically and objectively determined due to the accuracy limitation of atmospheric correction and suspended solids concentration inversion mode. A method of automatically recognizing abnormal turbid water body based on dominant wavelength of water color is proposed. The dominant wavelengths of water color information of remote sensing images of red,green and blue bands are extracted using Sentinel-2 and Landsat8 satellite image data based on CIE-XYZ color system. Furthermore,the dominant wavelengths of water color parameters indicating the concentration of suspended solids are automatically classified into high,medium,and low levels by using the natural breaks method,and the high value area is extracted as the suspected area of sand mining. The method was applied to reflect the temporal and spatial distribution of turbid water bodies,and had successfully identified the sand mining in the Jiuzhou River and Huazhou Bay waters of the Hedi Reservoir in Guangdong in 2016-2017 and in the Xunwushui River of the Fengshuba Reservoir in Guangdong from November 2019 to April 2020. Experiments have proved that the method is of strong resistance to atmospheric interference,high automation,stability and reliability,and is suitable for multi-source remote sensing images. The method also offers timely and effective tool for the temporal and spatial distribution of sand mining suspected areas for traditional manual inspections and supervision,and improves the capacity of normalized sand mining supervision.
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  Water Body Extraction of Ebinur Lake Based on Four Water Indexes and Analysis of Spatial-temporal Changes

  DUOLAITI Xilinayi, KASIM Alim, REHEMAN Rukeya, LIANG Hong-wu

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 134-140. https://doi.org/10.11988/ckyyb.20210634

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  The water body of Ebinur Lake is extracted by using normalized difference water index (NDWI),modified normalized difference water index (MNDWI),automatic water extraction index (AWEI) and modified automated water extraction index (MAWEI) with Landsat 5/7/8 series remote sensing images as the data source.The extraction results of the four indexes are compared and analyzed by establishing confusion matrix.MAWEI index is proved to be of the highest precision (over 95%) with the Kappa coefficient greater than 0.94.Furthermore,the area of Ebinur Lake is extracted by using the MAWEI index,and the change of lake area is analyzed through the dynamic degree.From 2000 to 2003,the area of Ebinur Lake increased from 768.93 km² to 982.27 km²,up by 27.74%,and the dynamic degree was 9.24%;from 2003 to 2014,the lake area shrank to 447.08 km²,down by 54.48% with the dynamic degree of -4.95%;from 2014 to 2018,the lake expanded again to 852.77 km²,rising by 90.74% with the dynamic degree reaching 22.68%;and from 2018 to 2020,the lake area reduced again to 593.79 km²,falling by 30.36% with the dynamic degree of -15.18%.In the past two decades,the area of Ebinur Lake displayed a trend of expansion first and then retreat in general.The change of lake area is positively correlated with annual precipitation and the runoff of Bortala River and Jinghe River,while negatively with evaporation.The reduction of water resources as well as the surge of socio-economic water use caused by the steady growth of population,irrigation area,and GDP also have impacts on the change of lake area.
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  Bibliometric Analysis of Research Trend of Hanjiang River Basin

  YUAN Jie, LI Qian-xi, ZHAO Yan-qiang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 141-146. https://doi.org/10.11988/ckyyb.20210501

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  The number of research papers,cooperative nations,core authors,major institutions,source publications and key words of Hanjiang River research from 2000 to 2020 are analyzed by using bibliometric approach based on WOS and CNKI databases.Results demonstrate that: the WOS and CNKI databases collected 560 and 533 research papers regarding Hanjiang River Basin from 2000 to 2020,respectively,and this number maintained a steady growth.Authors from 46 countries involved in papers indexed by WOS,of which 86% are from China,mainly in cooperation with the United States and Australia.Chinese researcher Zhang Quan-fa from Wuhan Botanical Garden of Chinese Academy of Sciences has published 43 papers in total,ranking first in the world,staying in the center of the author's cooperation network in the WOS database.The Journal of Hydrology published the largest number of papers in the WOS database,accounting for more than 4%,while the Yangtze River Basin,Resources and Environment ranks top in the CNKI database,covering a proportion of 7.7%.Climate Change and Dangjiangkou Reservoir are common high-frequency keywords in the two databases,indicating that the Hanjiang River Basin is mainly concerned with the Danjiangkou Reservoir area and the impact of climate change on the river basin.The research findings offer scientific support for future research on the Hanjiang River Basin.
RIVER DIVERSION HYDRAULICS
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  Factors Affecting the Prediction Deviation of Diversion Tunnel's Discharge Capacity

  GONG Ke, LI Xue-hai, WANG Shi-kui, ZHENG Nan, REN Kun-jie

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 147-150. https://doi.org/10.11988/ckyyb.20220549

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  In order to solve the problems of large prediction deviation caused by multiple factors affecting the discharge capacity of the diversion tunnel and the complex action mechanism,we identified and classified the influencing factors of the discharge capacity of diversion tunnel by integrating theoretical analysis,numerical simulation and model test.By analyzing the mechanism and degree of influence of each factor,we proposed the method of reducing the prediction deviation of discharge capacity.Roughness simulation deviation and scale effect of the modeled water-air two-phase flow are key factors that lead to the large deviation of the predicted discharge capacity,resulting in deviations of the open and full flow in cavern and the flow rate interval,which makes the open and full flow transforms to full flow in advance.To reduce the deviation,the range of the open and full flow obtained by test needs to be corrected.Under the condition of pressure flow,the roughness simulation deviation can be calculated by using the roughness deviation value of the original model according to the steps introduced in this paper.
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  Influence of Sidewall Angle on Discharge Capacity of Trapezoidal Key Weir

  YUAN Liu, JI Qing-feng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 151-157. https://doi.org/10.11988/ckyyb.20210685

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  As the further development of piano key weir,trapezoidal piano key (TPK) weir is of strong discharge capacity and is slightly influenced by terrain.To study the effect of different sidewall angles on the discharge capacity of trapezoidal key weir,RNG k-ε turbulence model and VOF method was used to simulate the free surface of weirs with five different sidewall angles.Results show that α< 0° has a negative effect on the discharge capacity of TPK weir.The increase of sidewall angle enhances the discharge capacity.When α=9°,the discharge capacity is no longer improved.In addition,the discharge capacity of different overflow fronts was analyzed via numerical simulation,and the internal influence mechanism of sidewall angle on the discharge capacity was revealed.
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  Similarity of Resistance in Model Test of River Diversion and Closure in Construction of Water Conservancy and Hydropower Projects

  ZI Jin-jia, LI Xue-hai, CHEN Liang, DONG Bao-shun, REN Kun-jie

  Journal of Changjiang River Scientific Research Institute. 2022, 39(10): 158-162. https://doi.org/10.11988/ckyyb.20220553

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  The dissimilar resistance of river diversion and closure models will lead to a large deviation between test results and actual situation. Factors affecting the similar resistance along the wall of long diversion tunnel are analyzed by using theoretical analysis and hydraulic calculation methods. The resistance crisis in the closure model test is revealed,and the approaches of solving the problem of resistance dissimilarity is proposed. In the case of tunnel diversion model,the modeling discharge capacity can be corrected by increasing the flow rate or fitting the relationship between the resistance coefficient and the model Reynolds number through system test because the water flow in tunnel diversion model is often in turbulence transition zone as restricted by the model scale,and the resistance coefficient of tunnel wall is a function of the model Reynolds number. In the case of closure model,the model water flow can be adjusted entering the self-simulation area by reasonably selecting the model scale to avoid resistance crisis because the similarity of thrust resistance coefficient must be satisfied when the blocks are similar in anti-shock stability,and the surrounding flow resistance coefficient is constant only when the model Reynolds number is 3×10⁴～2×10⁵.