01 June 2023, Volume 40 Issue 6

    

• Select all
  |

• Select
  Cover and Table of Contents

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 0-0.

  Abstract ( ) Download PDF ( )   Knowledge map   Save
Special Contribution
• Select
  The Core of Water Quality Problem of Honghu Lake and Comprehensive Improvement Approaches

  LIN Li, PAN Xiong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 1-6. https://doi.org/10.11988/ckyyb.20221630

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  As a critical ecologically sensitive area and a key node in the middle reaches of the Yangtze River, Honghu Lake has long served as a hub for water storage and irrigation in the Jianghan Plain. However, intense human activities have exacerbated water pollution and ecosystem degradation in the lake, making the improvement of Honghu Lake’s water quality a central objective of the ongoing Yangtze River conservation and restoration efforts. A comprehensive analysis reveals that the key challenges to enhancing the lake’s water quality lie in three main areas: inadequate inflow water quality, severe internal pollution, and degraded aquatic ecosystems. To tackle the water pollution of Honghu Lake, a systematic and basin-wide mindset must be adopted, encompassing effective measures such as controlling and intercepting external sources of pollution, sediment dredging, ecological restoration of the lake area and lakeshore, as well as scientifically allocating and utilizing water resources. In addition, comprehensive management strategies, including the establishment of an integrated water quality improvement framework, should be implemented. This framework would include a collaborative mechanism for joint prevention, control, and governance of Honghu Lake and its tributaries, as well as an ecological compensation mechanism.
Comprehensive Management of River Basin
• Select
  Practices of Cross-provincial Transverse Ecological Compensation Mechanism in the Yangtze River Basin: Refelctions and Improvement Suggestions

  ZHUANG Chao, YIN Zheng-jie

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 7-13. https://doi.org/10.11988/ckyyb.20220433

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Establishing a cross-provincial ecological compensation mechanism for river basins is an important approach to coordinating basin governance and protection. Since the pilot implementation of the first cross-provincial ecological compensation in the Xin’an River basin in 2012, thirteen cross-provincial river basins in China have established ecological compensation mechanisms. Since the implementation of the cross-provincial transverse ecological compensation mechanism in the Yangtze River basin, the level of cross-provincial basin governance has significantly improved. However, the establishment and implementation of cross-provincial transverse ecological compensation mechanisms still face challenges such as limited incentive effects, insufficient basin coordination, and restricted water quality compensation standards. From a management perspective, we analyze the scientific issues related to cross-provincial transverse ecological compensation and clarify the core principles of cross-provincial transverse ecological compensation mechanism. To strengthen incentive effects and promote coordination, we put forward suggestions to promote the necessary incentive functions for cross-provincial transverse ecological compensation, to leverage the coordinating mechanisms in the Yangtze River basin, and to establish a compensation benchmark system that fits the characteristics of the resources in the Yangtze River basin. These recommendations provide a reference for the improvement of a comprehensive cross-provincial ecological compensation mechanism in the Yangtze River basin.
• Select
  Discussions on Water Security Governance in China’s Greater Bay Area

  JI Hong-xiang, HUANG Ben-sheng, QIU Jing, ZHANG Zhi-lin, ZHENG Yong, QIN Yan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 14-20. https://doi.org/10.11988/ckyyb.20220336

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The New York Bay Area, San Francisco Bay Area, and Tokyo Bay Area have experienced rapid development and are recognized as first-class bay areas due to their robust economic and social growth. These regions have enacted a number of laws and regulations and implemented effective engineering measures to address water resources, water supply, flood control, and water ecological conservation. These measures aim to meet the increasing demands of water security while sustaining the rapid growth of bay area economies. In this article we analyze the current water security status of first-class bay areas, focusing on aspects such as water resources allocation, water conservation, flood control, and watershed management. We introduce the methods and successful experiences employed by these bay areas in overcoming resource constraints, coping with extreme weather events, and protecting ecological environment. Drawing on the characteristics of water resources in the Guangdong-Hong Kong-Macao Greater Bay Area, as well as the challenges faced in terms of water resource constraints, extreme weather, and ecological environment protection, we propose several recommendations to enhance water management in the bay area. These include promoting coordinated governance and management of water resources, strengthening the water resources allocation network, advancing research and application of new products and technologies for water-saving in agriculture and households, improving water transmission pipelines, implementing flood insurance systems, and enhancing water ecological environment management systems. These suggestions aim to provide valuable insights for ensuring water security and facilitating high-quality development in the Guangdong-Hong Kong-Macao Greater Bay Area.
River-Lake Protection and Regulation
• Select
  Health Assessment of Longgan Lake Using Benthic Index of Biotic Integrity

  ZHANG Yun-chao, ZHU Kong-xian, CHAI Zhao-hui, GE Li-can, MIN Feng-yang, PENG Zeng-hui

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 21-28. https://doi.org/10.11988/ckyyb.20220439

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Longgan Lake, located in the Huayang River and Lake Group Nature Reserve in Anhui Province, boasts significant ecological value. Scientific assessment of the lake’s water ecology using the Benthic Index of Biotic Integrity (B-IBI) provides a foundation for lake conservation and management. On the basis of benthic animal data collected from ten monitoring sites in Longgan Lake in April 2021, a comprehensive integrity index evaluation system was developed. The system comprises five core parameters: total species count, percentage of dominant group, percentage of mollusks, number of sensitive species, and number of adhesive species. Through analysis of the distribution range, discriminatory ability, and correlation of twenty candidate biological indicators, the most relevant parameters were identified. The dimensions of the biological parameters were standardized using the ratio method, and the scores for each parameter were aggregated to derive the B-IBI value. Lake health classification standards were established using the quartering process. The results revealed that among the ten monitoring sites in the lake area, three were classified as healthy, four as sub-healthy, two as fair, and one as poor. The overall water ecosystem health condition is not promising. The southeastern part of Longgan Lake was classified as healthy, while the water area at the border between Hubei and Anhui Provinces was categorized as sub-healthy, and the northeastern part as fair. The relatively poor health condition in the northeastern part of Longgan Lake may be attributed to its proximity to the entrance of the Erlang River, where the accumulation of domestic sewage and phosphate mining pollutants in the sediment has consequently impacted the integrity of benthic organisms.
• Select
  Variation of Residual Water Level in Wet Season and Dry Season under River-Tide Interaction in the Yangtze River Estuary

  ZHAI Wei, ZHANG Wei, JI Xiao-mei, CHEN Ting

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 29-34. https://doi.org/10.11988/ckyyb.20220717

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The average water level during tidal cycle, also known as the residual water level, is a typical outcome resulting from the nonlinear interaction between tides and river flow. To quantify the contributions of runoff, tides, and their interactions to the change of residual water level, the friction term is decomposed, and the components of mean tidal friction are examined to study the variations in residual water level. A two-dimensional numerical model is employed to simulate the hydrodynamic conditions and spatiotemporal characteristics of the residual water level in the Yangtze River Estuary. The continuous wavelet transform method togerther with the friction calculation formula is used to examine the primary sources of tidally averaged friction. Furthermore, a linear regression model equation is established to explain the variations in the residual water level. The results indicate that the residual water level in the Yangtze River Estuary exhibits distinct characteristics between wet and dry seasons and throughout the spring-neap cycle. Wet season experiences a more pronounced increase in the residual water level, particularly during spring tides. Tidally averaged friction is predominantly influenced by the river flow term and river-tide interaction term, with the contribution from river discharge consistently being greater due to its substantial volume. Tidally averaged friction governs the behavior of the residual water level. The variation in residual water level in the Yangtze River Estuary is primarily controlled by river flow; however, the influence of river-tide interactions cannot be ignored at downstream stations.
Water Resources
• Select
  Effect of Typhoons on Island Rainfall Based on Long-series Hydrological Monitoring Data: Case Study on Zhoushan Island in Zhejiang

  YE Zhou, GENG Cheng, XU Bei, CHEN Fang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 35-42. https://doi.org/10.11988/ckyyb.20221401

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The study aimed to investigate the influence of typhoons occurring in the northwest Pacific on rainfall at the Changchunling Rainfall Station in Zhoushan. By analyzing a long-term monitoring dataset spanning from 1980 to 2019, we explored the impact of typhoons on rainfall patterns. The findings revealed that, on average, typhoon rainfall at the Changchunling Station accounted for 72.55% of the total precipitation during the typhoon season. Specifically, typhoons making landfall in Zhoushan, and those in Zhejiang, as well as typhoons making landfall in other areas and non-landfall typhoons, contributed an annual average rainfall of 29.45 mm, 126.23 mm, and 364.68 mm to the Changchunling station, respectively. Furthermore, individual typhoons of the three types brought rainfall of 300.65 mm, 157.78 mm, and 71.28 mm to the Station. The study highlights that the overall precipitation at the Station is significantly influenced by typhoons generating rainfall exceeding 50 mm. Among these, the typhoons making landfall in Zhejiang, particularly those producing rainfall amounts above 50 mm, exert the greatest impact. In addition to the landfall location, the path direction of the typhoon emerges as the primary factor influencing rainfall patterns at the Changchunling Station, followed by its intensity and moving speed. These findings provide valuable insights into comprehending the formation of water resources on Zhoushan Island, offering significant implications for further research in this area.
• Select
  Application of Tracer Test in Hydrogeological Survey of Yibasan Reservoir

  LUO Rui-heng, LIU Tian-yun, HU Shun-qiang, ZHAO Yong-bin, PAN Xiao-dong, PENG Cong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 43-48. https://doi.org/10.11988/ckyyb.20220321

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The Yibasan Reservoir, located in Maguan County, Wenshan City, is a natural seasonal reservoir consisting of 11 karst depression reservoirs. Transforming these reservoirs into functional water storage facilities not only enhances the local ecological environment but also addresses the water supply challenges faced by the local community.The study area exhibits significant karst development, with an intricate network of underground river channels connecting the karst depressions. To investigate the patterns and distribution of underground river channels within the reservoir area, tracer tests were conducted with sodium fluorescein and rhodamine as tracers. The hydrogeological parameters and underground river network scale were estimated with Qtracer2. The results reveal abundant water storage in the major underground channel YBS01 -YBS05 and the southern branch YBS03-YBS05, reaching 79 060 m³and 72 546 m³, respectively. YBS01 and YBS02 in the northern part of the Damagu Reservoir are hydraulically connected. On the other hand, the southern branch is obstructed by the northeast-oriented compression torsion fault F3, leading to no hydraulic connection with the main channel. These findings provide crucial support for the reservoir formation process, and also offer fundamental data for calculating the capacity of the Yibasan Reservoir.
• Select
  A Monthly Runoff Forecast Model Combining Time Series Decomposition and CNN-LSTM

  LEI Qing-wen, GAO Pei-qiang, LI Jian-lin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 49-54. https://doi.org/10.11988/ckyyb.20220004

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To address the limitations of conventional models in fully capturing the complex nonlinear characteristics of runoff sequences, a monthly runoff prediction model is proposed by integrating the Seasonal-Trend decomposition procedure based on Loess (STL) with convolutional neural networks (CNN) and long short-term memory neural networks (LSTM). In this model, the runoff sequence is first decomposed into trend components, seasonal components, and residual terms of random fluctuations using STL. The decomposed component sequences are then input to the CNN for convolutional operations and subsampling, and the CNN outputs feature sequences that capture temporal relationships. These sequences are further processed by LSTM and the predicted runoff values are obtained through fully connected layers. With the monthly runoff data from the Taolai River gauge station in the Heihe River Basin as an example, the prediction performance of three models, LSTM, STL-CNN, and STL-CNN-LSTM, is compared and analyzed. The validation results demonstrate that the model integrating STL and CNN-LSTM achieves the lowest prediction error and the highest accuracy. Compared to conventional models that directly analyze the original runoff sequence, this model significantly improves the ability to predict monthly runoff.
Water Environment and Water Ecology
• Select
  Effect of Gradient Inlet Water on Aerobic Granular Sludge Characteristics and Removal Performance of Tomato Sauce Wastewater

  XIAO Fei, WANG Wei-hong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 55-63. https://doi.org/10.11988/ckyyb.20220125

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The wastewater generated from tomato sauce processing in Xinjiang exhibits high concentration, challenging treatment, and potential for surface water pollution. Therefore, studying the degradation technology for tomato sauce wastewater treatment is of significant importance. In this study, floc sludge was inoculated into two sequencing batch reactors (SBR), R1 and R2, at room temperature. Artificially prepared tomato sauce wastewater was used as the influent substrate to cultivate aerobic granular sludge (AGS) under varying influent chemical oxygen demand (COD) concentrations. The aim was to investigate the effects of influent COD concentration on AGS morphology, physicochemical characteristics of the sludge, and pollutant removal efficiency. The results demonstrate that with a fixed COD concentration of 350 mg/L in the gradient influent, the particle diameters of the sludge in R1 and R2 after complete granulation were measured as 780 μm and 1 060 μm, respectively. The average removal rates of COD, NH₃-N, TN, and PO^3-₄-P in the tomato sauce wastewater were as follows: R1 (95.2%, 96.03%, 85%, 92.07%) and R2 (93%, 89.54%, 78%, 89%). For influent COD concentrations ranging from 346 to 750 mg/L, 750 to 900 mg/L, and 900 to 1 200 mg/L, the granular morphology consisted of filamentous bacterial skeletons, porous structures, and agglomerates. Ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) predominantly existed in the outer and subouter layers of small-sized AGS particles, while polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) were mainly found in larger particles at the bottom of the reactor.Under constant gradient influent COD concentration, a high influent COD concentration contributed to the rapid formation of AGS and the enrichment of microbial communities responsible for nitrogen and phosphorus removal, consequently enhancing the system’s nitrogen and phosphorus removal performance.
• Select
  Water Quality Prediction for Xili Reservoir Based on Long-Short Term Memory

  WANG Bo-quan, JIN Chuan-xin, ZHOU Lun, SHEN Di, JIANG Zhi-qiang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 64-70. https://doi.org/10.11988/ckyyb.20220925

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Xili reservoir is one of the most important drinking water sources in Shenzhen. The water quality of the reservoir affects the water supply safety of the whole city. We aim to get timely and accurate water quality prediction results for formulating a scientific and reasonable water supply plan for the reservoir and water plant. Based on data decomposition using the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN), we established a long- and short-term memory network model of water quality prediction for Xili Reservoir. Through extensive simulation and calculation, the model demonstrates excellent performance. The prediction results of total nitrogen, ammonia nitrogen and total phosphorus in the water quality prediction model are in good agreement with measured results. For total nitrogen and ammonia nitrogen, the relative prediction error of the model can be controlled below 10%. This highlights the model’s ability to effectively simulate the changing water quality in the reservoir and underscores the model’s rationality. The research findings serve as vital model and technical support for water quality prediction and the development of water supply plans for the Xili Reservoir.
• Select
  EPS and Nitrogen and Carbon Removal Performance During Aerobic Granular Sludge Granulation

  ZENG Tian-xu, MA Jiao, DANG Hong-zhong, YAN Yuan, WU Xin-bo, LI Wei-wei, CHEN Yong-zhi

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 71-76. https://doi.org/10.11988/ckyyb.20220102

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To address the issue of prolonged granulation time and poor stability of aerobic granular sludge (AGS) in domestic wastewater treatment, a gradual transition approach is proposed by gradually introducing domestic wastewater into artificial water, aiming to investigate the granulation process of AGS and its denitrification and decarbonization efficiency. AGS was cultivated in four sequencing batch reactors (SBRs), and the inoculum used was the settled sludge from the secondary sedimentation tank of the A²/O process in a wastewater treatment plant. At a temperature of 25 ℃, R1 received artificial water for the first 17 days, followed by a switch to domestic wastewater on the 18th day. In R2, the artificial water proportion was gradually reduced over stages until domestic wastewater reaches 100%. R3 only received artificial water throughout the experiment, while R4 operated at a lower temperature of 15 ℃ and received artificial water. The results revealed that water quality and temperature variations caused increased fluctuations in protein (PN) and polysaccharide (PS) content in the extracellular polymeric substances (EPS) of R1 and R4. R2 and R3 exhibited an upward trend in PN and PS content, and the settling velocity of AGS increased with higher PN content. At 25 ℃, the sludge volume index (SVI) showed a negative correlation with EPS. Successful cultivation of AGS was achieved at both temperatures. Specifically, at 25 ℃, the gradual transition approach by introducing domestic wastewater into artificial water resulted in a shorter granulation time of AGS in real domestic wastewater, along with enhanced settling performance. These research findings provide valuable insights for AGS-based treatment of domestic wastewater.
Soil and Water Conservation and Ecological Restoration
• Select
  Research Progress on Spatial-Temporal Variation of and Measurement Technologies for Soil and Water Loss on Whole Hillslope

  XU Wen-sheng, GU Jin-yu, SUN Bao-yang, ZHANG Zhi-hua, ZHANG Wen-jie, LI Li

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 77-85. https://doi.org/10.11988/ckyyb.20221131

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Whole hillslope is a basic unit for multi-scale measurement and conversion of water and soil loss, which lies between traditional slope and watershed scales. Based on the analysis of the basic unit of water and soil loss, we define the scope of whole hillslope surface as a complete geomorphic unit located between the watershed and from the top to the foot of the slope. Spatial heterogeneity, such as slope length, slope gradient, slope position, and land use distribution pattern, is a crucial factor that differentiates the whole slope from traditional slope research and affects the spatial differentiation of water and soil loss. Runoff, sediment, carbon, nitrogen, phosphorus, and other flux materials of water and soil loss are key elements for studying the erosion law of the whole hillslope. The migration and transformation of key elements of the whole hillslope is a complex physical and chemical process, while current measurement techniques are insufficiently efficient to identify, extract, and quantitatively analyze each element, thus requiring the establishment of a measurement technology system for the whole hillslope. The study of spatio-temporal variation of and measurement techniques for soil and water loss on the whole hillslope can provide an essential reference and basis for constructing multi-scale nested measurement system and simulating and predicting erosion, runoff, and sediment processes at different scales.
• Select
  Multi-scenario Simulation of Land Use in Nanchuan District of Chongqing Based on PLUS Model

  XIE Xiang-dong, LIN Xiao-song, WANG Ying, TU Rong-yu, ZHANG Ji-xiang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 86-92. https://doi.org/10.11988/ckyyb.20221227

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Multi-scenario simulation of land use change is the basic basis for future land use planning, and is of great significance to the realization of regional social-economic-ecological harmony and stability.Based on land use data from 2000, 2010, and 2020, we analyzed the temporal and spatial characteristics of land use in the study area over the past two decades using dynamic degree and transition matrix analysis. Fifteen driving factors are selected from domains of social economy, geographical environment, and transportation network. Three scenarios—economic development, ecological protection, and cultivated land protection—are designed, and the PLUS model is employed to simulate the distribution of land use in the study area for 2030. The differences among the simulated scenarios are compared and analyzed.The findings reveal the following: 1) Over the past 20 years, the area of cultivated land reduced notably to 63.56 km². Conversely, the area of construction land surged from 0.3% to 2.8% of the total area, primarily concentrated in the central and southwestern parts of the study area. 2) The Kappa coefficient and overall accuracy of the simulation results for 2020 reached 0.938 and 0.957, respectively, surpassing standard values, implying that the PLUS model is suitable for land use simulation in the study area. 3) Comparison of the simulation results among different scenarios indicates that under the cultivated land protection scenario, the total cultivated land area can be preserved, and in the meantime ecological land is safeguarded, while the extensive expansion of construction land is reasonably constrained. The simulation result aligns more closely with the future sustainable development of the study area and can serve as a reference for the rational planning of land resources and the development of high-quality new urban areas in Nanchuan District.
• Select
  Spatial-Temporal Evolution of Vegetation Cover in Santun River Basin from 2000 to 2020 Based on Remote Sensing Monitoring

  ZHANG Yan-jiao, LI Qiao, SU Yan-peng, TAO Hong-fei, JIANG You-wei, AIHEMAITI·Mahemujiang, WEI Jian-qun, YANG Wen-xin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 93-99. https://doi.org/10.11988/ckyyb.20220308

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To analyze the spatiotemporal characteristics of vegetation cover in the Santun River Basin, a comprehensive study was conducted using a combination of Landsat satellite remote sensing data, pixel-based binary models, image differencing methods, and coefficient of variation. The period from 2000 to 2020, spanning 20 years, was examined to assess the distribution patterns, trends, and stability of vegetation cover. The results reveal a consistent annual increase in vegetation cover within the Santun River Basin, with a notable average growth rate of 4.93% per decade from 2012 to 2015. Spatially, the distribution of vegetation cover follows a distinctive pattern, with higher values observed at the two ends and lower values in the central regions. Additionally, approximately 39.58% of the Santun River Basin exhibits improved vegetation cover, indicating an overall positive trend. Notably, the majority of the basin displays relatively stable vegetation cover, characterized by minor to moderate variations.The evolution of vegetation cover in the Santun River Basin is influenced by a combination of natural and human factors. Changes in temperature and precipitation patterns constitute the primary natural influences, while alterations in land use types serve as the main drivers of change induced by human activities. These findings provide scientific foundation for promoting ecological restoration and facilitating sustainable economic development within the Santun River Basin.
Hydraulics
• Select
  Preliminary Study on Calculation Method of Incipient Velocity of Non-cohesive Sediment in Open Channel Flow and Ice Sheet Flow

  LIU Xiao-min, YANG Yao-tian, ZHANG Hong-wu, WANG Wen-juan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 100-106. https://doi.org/10.11988/ckyyb.20211404

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Ice cover is a natural phenomenon commonly observed in winter rivers of northern regions. Its presence alters the river’s motion from turbulent to laminar flow, affecting the vertical velocity distribution due to the roughness of the ice cover and further influencing the sediment transport on riverbed. To investigate the evolution of sediment transport in glacial rivers, a formula for incipient velocity of coarse and fine sediment particles is deduced theoretically suitable for ice-covered flow based on the Einstein assumption by using a rolling starting model. The effects of roughness change under the ice cover, the dry density of viscous sediment, and the relative exposure degree on sediment incipient motion are considered. Comparison with existing experimental data manifests that the relative error of the proposed formula ranges from 1% to 10%. Additionally, the applicability of the incipient motion formula to open channel flow is discussed. The formula can be considered suitable for calculating sediment starting velocity in open channel flow when the roughness of the ice cover is 0. The relative error validated by measured data is between 0% and 0.86%, meeting the precision requirement.
• Select
  Calculations and Experiments on Free-Surface-Pressurized Flow in Rectangular Water Conveyance Tunnel with Arch Crown

  ZHANG Jing-mei, XIANG Sheng, TANG Rong-cai, WANG Qun, JU Xiao-ming

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 107-113. https://doi.org/10.11988/ckyyb.20220154

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The operation of gates in non-pressure water conveyance tunnels often induces hydraulic transients in the form of free-surface-pressurized flow (mixed flow), which can lead to pressure surges that pose a threat to the project’s safe operation. An experimental investigation was conducted to study the hydraulic transition process of mixed flow and pressureless flow in a rectangular tunnel with an arched crown. Water depth or pressure measurements were taken along the length of the model tunnel under different flow conditions, and the results were compared with calculated values obtained using the diffusion method based on the narrow slot assumption. The experiments revealed a complete free-surface-pressurized flow regime, where the closure of the downstream gate caused a sharp increase in pipeline pressure when the initial downstream water depth approached the height of the vertical wall in the arched tunnel under high flow conditions. This process is accompanied by intense air entrainment and upstream flow propagation. Under low flow conditions, a critical mixed flow regime was observed, characterized by a sudden pressure rise without aeration. The water echo resulted in a secondary pressure spike, reaching its peak value. The research findings demonstrate that the narrow slot diffusion method could accurately simulate the complete free-surface-pressurized flow regime, but generates a larger error when simulating the critical regime. The calculated results and experimental data are in good agreement for the hydraulic transition process of pressureless flow, validating the rationality of the mathematical model.
Rock-Soil Engineering
• Select
  Impact Zoning and Effect of Reinforcement Measures for Ultra-close Construction Overcrossing Existing Tunnel

  CUI Guang-yao, SONG Bo-han, HE Ji-hua, TIAN Yu-hang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 114-118. https://doi.org/10.11988/ckyyb.20220121

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The purpose of this study is to guarantee the safe operation of tunnels by identifying the disturbance of new tunnel construction to existing tunnels. The construction of Beijing Metro New Airport Line overcrossing the existing Metro Line 10 tunnel was taken as a case study. The disturbance was simulated using FLAC^3D with varying burial depth and clearance of the existing tunnel. According to the control value (2 mm) and warning value (1.4 mm) of vault displacement control standard for the existing tunnel, the disturbance impact zone was divided into strong impact zone, weak impact zone and non-impact zone. Furthermore, according to the construction impact zoning and engineering characteristics, two reinforcement measures were proposed and numerically simulated. The two measures are: advance pipe curtain, and advance pipe curtain plus soil grouting. Results demonstrate that the control effect (vault displacement reduction rate) of advance pipe curtain is 64.05%, while the advance pipe curtain plus soil grouting 70.23%. Considering on-site control standards, we recommend that the advance pipe curtain plus soil grouting could ensure the construction safety of the new tunnel and the operation safety of the existing tunnel as well.
• Select
  Consolidation of Vertical Drain Foundation in Consideration of Temperature Effect and Well Resistance Change

  ZHANG Yu-guo, WANG Chuang, YANG Wen-bing, ZHAO Ya-min

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 119-125. https://doi.org/10.11988/ckyyb.20211378

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  A calculation model for the consolidation of vertical drain foundation that considers temperature effects and well resistance change is established in this study. The general solution of consolidation for vertical drain foundations in consideration of temperature effects and well resistance change is obtained through analytical methods. The correctness and rationality of this solution are verified by degradation studies and comparisons with existing solutions. An example is used to draw the consolidation curve of a vertical drain foundation considering temperature effects and well resistance change. The results show that both temperature effects and changes in well resistance have a significant influence on the consolidation of vertical drain foundations. The higher the temperature, the larger the consolidation rate, but the influence of temperature on consolidation gradually weakens. Well resistance has a more significant effect on consolidation rate than temperature does. When the drain spacing ratio and temperature remain unchanged, and the well resistance reaches a certain value, the consolidation rate tends to be zero, and the consolidation degree tends to be a certain value. With an increase in well resistance, the dissipation of excess pore pressure slows down significantly. The higher the temperature, the faster the excess pore pressure dissipates.
• Select
  A Prediction Model for Advance Rate of Double Shield Tunnel Boring Machine Based on HC Value of Surrounding Rock Classification

  YANG Ji-hua, YAN Chang-bin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 126-132. https://doi.org/10.11988/ckyyb.20220059

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In the light of the HC evaluation system in the Code for Geologic Investigation of Water Resources and Hydropower Engineering, a model of predicting the advance rate of double shield Tunnel Boring Machine (TBM) is established based on analysing the correlations between the net penetration rate and utilization rate of TBM and the HC score through statistical analysis of field measured data. The double shield TBM construction of water conveyance tunnel of Lanzhou water source project is taken as a case study. Results reveal 1) a quadratic function relationship between net penetration rate and HC score with the correlation coefficient reaching 0.84. With the decrease of HC score, the net penetration rate shows an increasing trend. 2) There is also a quadratic function relationship between TBM utilization rate and HC score, with the correlation coefficient being 0.82. With the increase of HC score, the utilization rate increases first and then decreases. 3) When HC score ranges between 41 and 46, the advance rate of TBM peaks with the daily tunneling distance reaching 45 m. When HC score is smaller than 41, advance rate decreases along with the decline of HC score. When HC score is greater than 46, advance rate reduces with the increase of HC score. 4) The predicted advance rate is in good agreement with the actual construction speed, with an average error of 5.2% and a maximum error less than 10%, indicating that the prediction model is reliable and can be used to predict the advance rate of double shield TBM.
• Select
  Application of Depressurization Technology by Blind Trench Drainage in Anti-floating of Underground Structures

  TAO Wen-tao, ZHAN Hai-qun, SUN Yi, XIE Jun, LUO Hui-ping, DONG Jun, AN Xu-wen

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 133-138. https://doi.org/10.11988/ckyyb.20220390

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Based on geological characteristics of the three-level terraces in the Yangtze River at Wuhan, we analyze the feasibility of depressurization by blind trench drainage. We introduce the practical application of drainage depressurization in engineering projects, present the theoretical analysis and experimental results of blind trench drainage test models, and evaluates the reliability and durability of blind trenches. The findings demonstrate a close agreement between the calculated seepage flow of the test models and the actual experimental results. When the foundation of underground structures is situated in less permeable clay layers,the blind trench drainage technique proves effective in reducing the buoyant water level of these structures. Additionally, blind trenches exhibit minimal seepage flow, resulting in negligible long-term impact on the surrounding environment. Consequently, in areas where the foundations of underground structures lie within the clay layers of the three-level terraces in the Yangtze River at Wuhan, the blind trench drainage technique proves highly efficient in significantly reducing or even completely eliminating the buoyant water level of underground structures. This approach holds substantial potential for application, particularly in the anti-floating of underground stations of subway systems with relatively low self-weight.
• Select
  Analysis Model of Surface Water Infiltration Process Considering Layered Soil Water Resistance and Seepage Reduction Effect

  ZHANG Xing-yi, CAO Wen-gui, CUI Peng-lu, LI Hui-xin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 139-146. https://doi.org/10.11988/ckyyb.20220092

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In this paper we aim to enhance the theoretical methods for analyzing surface water infiltration processes by focusing on the distinct characteristics of stagnated and reduced infiltration during the infiltration from high-suction soil to low-suction soil. By considering the unsaturated properties of soil near the wetting front, we divided the water infiltration process into three stages: upper soil infiltration, stagnant water infiltration, and subsoil infiltration. We further derived the surface water infiltration model to refelct the water blocking and infiltration reduction effect in layered soil infiltration, and analyzed the sensitivity of model parameters via comparison with existing experimental results and models. Results demonstrate that the model proposed in this paper provides a more accurate description of water retention and infiltration reduction in layered soil infiltration. It offers a better understanding of the infiltration mechanism. Assuming a linear decrease in infiltration rate during the stagnation of wetting fronts aligns with real-world observations. Different soil properties have varying effects on infiltration: the type, burial depth, and ponding depth of the lower layer of low-suction soil significantly influence the infiltration characteristics. The initial water content of the soil primarily affects the infiltration time. Moreover, the proportion of the wetting front transition zone plays a significant role in water retention.
• Select
  Experimental Study on the Strength of Cemented Soil in Baishan Navigation Lock of Yangtze-Huaihe Water Diversion Project

  WANG Zhi-yong, DU Guang-yin, ZHANG Ding-wen, SONG Tao, YANG Yong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 147-153. https://doi.org/10.11988/ckyyb.20211403

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Intelligent bidirectional cement-soil mixing technology has been applied in the Baishan navigation lock of the Yangtze-Huaihe water diversion project. To investigate the strength variation of the cemented soil in the Baishan navigation lock and assess the effectiveness of the new technology, we prepared cemented soil specimens with varying shapes, cement ratios, and curing ages. These specimens underwent unconfined compressive strength tests and triaxial unconsolidated and undrained tests, allowing us to obtain the stress-strain relationship, compressive strength, and shear strength parameters. The results of the laboratory tests indicate that the stress-strain relationship of the cemented soil exhibits strain softening behavior. The unconfined compressive strength increases with the growth of cement ratio and curing age, showing an approximate linear correlation with the logarithm of curing age. Under the same conditions, 90-d age cylindrical specimens display a strength approximately 13% higher than cubic specimens. The ratio of deformation modulus to unconfined compressive strength ranges from 55.6 to 96.2 and is significantly influenced by the age of the specimens. Cohesion and unconfined compressive strength can be described as approximate linear growth relationship, and the internal friction angle ranges from 22° to 33°. The in-situ core samples exhibit a strength exceeding 70% of that of laboratory cemented soil, demonstrating that the strength ratio expression helps compensate for the strength discrepancy between laboratory and in-situ cemented soil. Scanning electron microscope (SEM) results also unveil the mechanism behind the strength growth of cemented soil from a micro perspective.
• Select
  Macro-and-microscopic Responses of Strength Deterioration of Sulphate Saline Soils under Freeze-Thaw and Dry-Wet Cycles

  LEI Guo, ZHANG Wei-bing, LI Xiao, LIU Zhen-xiang, ZHOU Xin-lei

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 154-159. https://doi.org/10.11988/ckyyb.20211396

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Under freeze-thaw-dry-wet cycles, the main cause of strength deterioration in sulphate saline soils is the microscopic pore structure of the soil. In this study, we investigated the macro and micro response relationships of strength deterioration using unconfined compressive strength tests, mercury compression tests, electron microscopy scanning tests, universal global optimization (UGO) analysis of data, and ImageJ2X processing of SEM images. The results demonstrate that: (1) The unconfined compressive strength tends to increase and then decrease with the salt content under freeze-thaw-dry-wet cycles, and the peak strength corresponds to a low salt content when the compaction is low. Additionally, the percentage of pores between 1-10 μm is the threshold for strength deterioration, which is irreversible, occurs when the percentage is higher than 50%. (2) Under freeze-thaw-dry-wet cycles, the unconfined compressive strength is correlated with the skewness and structural merit of the microscopic parameters. Unconfined compressive strength shows a positive correlation with skewness and a negative correlation with structural merit, with structural merit having a more significant effect on strength than skewness does. (3) Structural merit, skewness, sorting factor, and mean pore throat radius, in descending order, are the microscopic parameters that affect the deterioration degree of macroscopic indicators of unconfined compressive strength. This study provides a reference for further research on the engineering properties of saline soils by exploring the macro-and-micro-response relationships of sulphate saline soils at the quantitative level.
Engineering Safety and Disaster Prevention
• Select
  Auxiliary Water Level Measurement During Automatic Dam Safety Monitoring with Robotic Total Station

  ZHOU Jian-guo, PENG Duo, JIANG Wei-guo, LI Jian-zhou

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 160-165. https://doi.org/10.11988/ckyyb.20220110

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The water level of reservoir is a crucial element of dam safety monitoring. This paper presents a method to assist in water level measurement using a robotic total station during its displacement monitoring tasks. Initially, the telescope of the robotic total station is precisely aimed at the water level line, and the elevation of water level is calculated using trigonometric leveling principles. Simultaneously, the initial equation for the water level line is manually obtained by capturing a picture with the coaxial camera. During the periodic monitoring stage, the vertical angle of the telescope is adjusted to capture images of the water level line based on the predicted results from the Kalman filter. Subsequently, a series of image processing techniques are employed to extract the water level line from the picture considering the initial slope of the water level line. Adjustments are made to ensure that the captured image is centered on the water level line, and the elevation of the water level line is calculated. The test results demonstrate that this method has a certain engineering application prospect, and is helpful to expand the use of robotic total station in dam safety monitoring.
• Select
  Centrifugal Model Test on Deformation Mechanism of Reservoir Bank Landslide under Reservoir Water Level Fluctuation

  GU Jian-yong, ZHANG Qiang, LU Xiao-chun, HU Jing, ZHU Jun-wei

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 166-172. https://doi.org/10.11988/ckyyb.20220009

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To investigate the deformation and evolution mechanism of landslides under changing reservoir water levels, a 1∶70 scale model of the Cheyiping landslide was established, and a reservoir water level rising and falling system was designed. Centrifugal model tests were conducted with one water level rise and two consecutive water level plummets at different rates. The findings reveal that during the water level rising stage, the landslide deformation is not significant. However, during the initial water level drop, tension cracks in the front edge of the landslide develop rapidly and form a fracture zone. Subsequently, the fault zone collapses and tension cracks appear in the middle and rear part of the landslide. During the second water level drop, the landslide continues to slide along the original fracture zone, but the sliding noticeably attenuates. The vertical compaction in the middle and rear parts of the landslide leads to the stabilization of fracture propagation. During the water level rising stage, the pore pressure exhibits noticeable lag and gradually diminishes in subsequent stages. The soil pressure in the leading edge of the sliding mass varies significantly in each stage, while in the middle and rear changes most severely during the first rapid water level drop. Overall, the water level drop rates that lead to landslide instability range from 0.7 to 1.5 m/day. The dynamic water pressure effect is stronger in the deeper parts of the landslide compared to that in the shallower layers. The deformation of the landslide is more influenced by the initial water level plummet than the second. The deformation and failure gradually decrease from the front to the rear, resembling traction characteristics.The water level rising, the first plummeting and the second plummeting stages demonstrate initial deformation, accelerated deformation, and decelerated deformation characteristics, respectively.
Hydraulic Structure and Material
• Select
  Influence of Dry-Wet Cycle and Continuous Axial Load on Sulfate Resistance of Cement Mortar

  WANG Shuai, HU Shao-wei, LI Wen-hao, LI Jing-hao

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 173-179. https://doi.org/10.11988/ckyyb.20220032

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To analyze the influence of sustained axial compression loads and wet-dry cycles on the sulfate erosion resistance of cement mortar, a combination of macroscopic and microscopic experiments was conducted. We compared the appearance phenomena, appearance quality, expansion rate, and strength degradation characteristics of the cement mortar under different conditions aiming to explore the erosion mechanisms involved. The results revealed that both sustained axial compression loads and wet-dry cycles significantly exacerbated the deterioration of mortar, with a more notable effect observed at higher stress levels. The mortar subjected to a stress ratio of 0.4 exhibited the highest increase in linear expansion rate, reaching 0.67%, and experienced the greatest loss in compressive strength, with a reduction of 40.72%. Under dry-wet cycles, the mortar displayed a maximum increase in linear expansion rate of 0.43% and a significant loss in compressive strength of 29.63%. Lower sustained axial compression loads initially mitigated sulfate erosion in the early stages but aggravated it later on. Conversely, higher sustained axial compression loads directly increased internal defects within the mortar, intensifying chemical erosion and leading to a substantial decline in macroscopic performance. The combined effect of wet-dry cycles and sulfate crystallization, calcium aluminate, gypsum, and other corrosion products contributed to the deterioration of the mortar's microstructure and the expansion of defects. Although the erosion mechanism of sulfates remained unaffected by sustained axial compression loads, these loads significantly influenced the erosion process. The degradation pattern of sulfate-resistant compressive strength in mortar can be effectively described by a binomial function. The research findings provide valuable guidance and support for the durability evaluation and the design of protective layers in hydraulic structures.
• Select
  Pore Characteristics and Dynamic Mechanical Properties of Polyoxymethylene Fiber-reinforced High-strength Concrete

  QIN Nan, LI Qiong, XU Bo

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 180-186. https://doi.org/10.11988/ckyyb.20220087

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In this study, we aimed to investigate the pore characteristics and safety of high-strength concrete reinforced with polyoxymethylene (POM) fibers under impact loads. We prepared high-strength concrete samples with a design strength grade of C60, incorporating POM fibers with a length of 6 mm. The volume fractions of POM fibers used were 0%, 0.15%, 0.3%, 0.45%, and 0.6%. We further analyzed the distribution patterns of the T₂ relaxation time spectrum for specimens with different fiber contents by using nuclear magnetic resonance (NMR) technology. Additionally, we conducted quasi-static compression tests on the specimens with various fiber contents using a rock mechanics testing machine, and carried out dynamic uniaxial compression tests on the specimens at different strain rates (64.8 s^-1, 87.0 s^-1, 116.4 s^-1, and 149.1 s^-1) using a split Hopkinson pressure bar (SHPB) apparatus. Through these experiments, we analyzed the internal pore structure of POM fiber-reinforced high-strength concrete, as well as the changes in stress-strain curves, peak stress, toughness, and energy dissipation under different strain rates and fiber contents.The results reveal several key findings. The inclusion of POM fibers leads to a reduction in the peak value of the T₂ relaxation time spectrum, accompanied by a leftward shift in the spectrum curve. This indicates a decrease in the number of internal pores, a reduction in pore diameter, and a lower porosity within the specimens. The results also unveil a significant strain rate effect in the specimens, with the addition of POM fibers enhancing the overall performance.The peak stress of the specimens exhibited an initial increase followed by a decrease as the fiber content increased. Notably, when the fiber content reached 0.45%, the dynamic compressive strength of the specimens reached its peak, while excessive fiber content resulted in a decrease in strength. Moreover, the inclusion of fibers improved the toughness of the specimens in resisting external loads. The dissipated energy of the specimens increased proportionally with the incident energy, displaying a positive linear relationship. The fracture energy density of the specimens initially increased and then decreased with the increase of fiber content, with the optimal effect observed at a content of 0.45%. Furthermore, increasing strain rate amplified the variation amplitude of the energy dissipation density in the specimens.
• Select
  Comprehensively Assessing the Appearance Quality of Concrete Based on Fuzzy Mathematics

  YANK Ke, TAO Tie-jun, HUANG Ke-yu, XU Yue-sheng, YOU Ju-gang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(6): 187-194. https://doi.org/10.11988/ckyyb.20220029

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Detecting and quantifying surface bugholes on concrete is a crucial aspect of evaluating the appearance quality of concrete. Relying solely on the size of bughole is insufficient to comprehensively assess the appearance quality of concrete. In this study we consider the influence of bughole quantity on the evaluation of concrete’s appearance quality. Based on fuzzy mathematical methods, we employed a grey relational analysis approach to establish an evaluation model with the maximum diameter, area ratio, and number of bugholes as the factor set. This model comprehensively evaluates the appearance quality of concrete and explores the impact of different proportions of defoamers and air-entraining agents on the appearance quality of concrete based on the evaluation results. Results demonstrate that 1) the coefficient of correlation between the CIB grade and the number of bugholes is 0.929 74. Through regression analysis, we propose a grading index for the number of bugholes. Factors in the factor set have different degrees of influence on the appearance quality of the formed concrete, with the maximum diameter of bugholes having the greatest impact, followed by the number of bugholes, and finally, the area ratio. Therefore, the number of bugholes should be considered as an important factor affecting the appearance quality of formed concrete. 2) When the dosage of defoamer is less than 0.3‰, the size and number of bugholes decrease with an increase in the defoamer dosage and increase with an increase in the air-entraining agent dosage. When the dosage of defoamer exceeds 0.5‰, the corresponding values increase with an increase in the defoamer dosage while decrease with an increase in the air-entraining agent dosage. An appropriate proportion of additives can effectively improve the appearance quality of the formed concrete. 3) The grading method based on fuzzy mathematics can accomplish the evaluation of concrete’s appearance quality. According to the comprehensive evaluation results, the best appearance quality of concrete is achieved when the dosages of defoamer and air-entraining agent are 0.5‰ and 0.15‰, respectively.