01 September 2023, Volume 40 Issue 9

    

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  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 0-0.

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Special Contribution
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  Historical Channel Evolution of Zhenjiang-Yangzhou Reach in Lower Yangtze River

  QU Geng, HAO Jie-yu

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 1-7. https://doi.org/10.11988/ckyyb.20230546

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  As a typical bifurcating channel in the tidal reach of the lower Yangtze River(also known as the Changjiang River), the Zhenjiang-Yangzhou Reach has experienced long-term complicated evolution. By examining historical documents, ancient maps, modern topographic mapping, and hydrological data, we analyzed the long-term evolution of the Zhenjiang-Yangzhou Reach. According to our findings, prior to the Western Han Dynasty, the Zhenjiang-Yangzhou Reach served as the mouth of the Changjiang River. Sediment gradually accumulated in the ancient estuary, giving rise to the development of a sandbar along the north bank. The river channel generally shifted in a southerly direction, resulting in decreased river width. The sediment deposition eventually stabilized, forming the Shiye sandbar branching channel and the Hechang sandbar branching channel. Throughout history, hydraulic power and sediment transport characteristics played a key role in shaping and transforming the river. River nodes located on both the north and south banks played an essential role in controlling the river’s flow regime. Since the 1950s, the channel morphology of Zhenjiang-Yangzhou Reach has been in a relatively stable state. However, recent developments have shown adjustments in the flow regime within the branching channel. Human activities, such as the construction of various projects in the river, have become important external factors influencing the evolution of the riverbed.
Water Resources
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  Measurement and Influencing Factors of Green Efficiency of Water Resources in Urban Agglomerations in Middle Yangtze River

  XIAO Yi, CI Xiao-hu, YANG Bing, ZHANG Li-ping, XIA Jun

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 8-16. https://doi.org/10.11988/ckyyb.20230206

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  The high-quality development of the Yangtze River Economic Belt constitutes a crucial strategy tied to overall national growth. Ensuring ecological priority and green development necessitates addressing the fundamental issue of improving the green efficiency of water resources in urban agglomerations. This study introduces the concept of “green development” into traditional research on water resources utilization efficiency. A comprehensive indicator system for evaluating the green efficiency of water resources is constructed. The super-efficiency EBM-DEA (Epsilon-Based Measure - Data Envelopment Analysis) model and panel Tobit model were employed to calculate and analyze the green efficiency of water resources in urban agglomerations in the middle Yangtze River. The findings reveal: 1) Changes in GDP have a significant impact on the economic efficiency of water resources, and the measurement results for the environmental efficiency and green efficiency of water resources are more reflective of actual conditions. From 2009 to 2020, comparisons among various city clusters reveal that the green efficiency of water resources in the Wuhan city cluster consistently outperformed that of the Poyang Lake urban agglomeration and Changsha-Zhuzhou-Xiangtan urban agglomeration. 2) Cities with thriving economies also exhibit high values of water resource utilization efficiency. Areas with abundant water resources in urban agglomerations in the middle Yangtze River demonstrate slightly lower water use efficiency than areas with scarce water resources. Rapid urbanization exerts a restraining effect on green efficiency of water resource, underscoring the need for urban agglomerations in the middle Yangtze River to adhere to a green and new type of urbanization development path.
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  Application of Bankruptcy Theory to Basin Water Resources Allocation under the Scenario of Supply and Demand Change

  SUN Dong-ying, YU Meng-ling, MA Jian-feng, WANG Hui-min

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 17-23. https://doi.org/10.11988/ckyyb.20220642

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  Amidst population growth and rapid economic development, the demand for water resources is continuously increasing. However, the uncertain water demand and total supply caused by environmental changes have led to an intensified mismatch between water supply and demand. In view of this, the bankruptcy theory was applied to water resources allocation at basin scale. Four bankruptcy theory rules - the proportional rule (PRO), constrained equal awards rule (CEA), constrained equal losses (CEL), and adjusted proportional rule (AP) - are employed to address water allocation problems in the basin under various supply and demand scenarios. The stability of the bankruptcy criteria was evaluated. Additionally, the Fallback bargaining method was utilized to select consistent and satisfactory results. The findings indicate that the AP rule exhibits the best stability in all scenarios, followed by the PRO rule. The application of Fallback bargaining demonstrates that the results obtained by the PRO rule achieve unanimous satisfaction. In view of the disparity between the two rules, the PRO rule is considered to yield satisfactory result. Based on these findings, an analytical framework that combines the bankruptcy criterion and Fallback bargaining was established to offer a scientific decision-making basis for water resources management in changing basin environments.
Water Environment and Water Ecology
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  Inhibiting the Growth of Microcystis aeruginosa by H₂O₂ Generated in the Electrolysis Process by Low-Amperage Electric Current

  ZHANG Yu-ting, LIN Li, JIA Di, DONG Lei, PAN Xiong, LIU Min, ZHAO Liang-yuan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 24-31. https://doi.org/10.11988/ckyyb.20220306

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  Platinum titanium served as the anode, while a carbon black polytetrafluoroethylene (C/PTFE) gas diffusion electrode was utilized as the cathode in order to facilitate the production of H₂O₂ through low-amperage electrolysis, with the aim of inhibiting the growth of Microcystis aeruginosa. Through a series of experimental investigations involving varying electrolysis time, current density, and gas flow, the optimal conditions for inhibiting Microcystis aeruginosa were determined. Specifically, the optimal configuration involved the electrolysis of 100 mL of 5×10⁵ cells/mL algae solution at a current density of 10 mA/cm² and a gas flow rate of 0.4 L/min for a duration of 60 minutes. Following electrolysis, the optical density (OD₆₈₀) of the algae cells decreased from 0.035 to 0.003, indicating the complete inhibition of algae cell growth. Additionally, the measurement of chlorophyll fluorescence parameters, such as F_v/F_m, Y(Ⅱ), and Y(NO), demonstrated the substantial disruption to the photosynthetic mechanism of the algae, further indicating the complete decay of the algae population. The concentration of H₂O₂ generated during electrolysis was determined to be 79 mg/L. Furthermore, even after six cycles of reuse, the C/PTFE cathode maintained 66% (52 mg/L) of the initial H₂O₂ concentration, highlighting the excellent stability and promising application potential of the C/PTFE electrode. This study presents a novel approach to effectively inhibit cyanobacterial blooms through low-amperage electrolysis, offering a new avenue for remediation.
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  Evaluation of Aquatic Ecological Health of Rivers in the Lower Reaches of Dongjiang River Based on Benthic-Index of Biotic Integrity

  MA Zhuo-luo, HU He-ping, WANG Sai

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 32-38. https://doi.org/10.11988/ckyyb.20220331

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  Changes in zoobenthos can effectively indicate the damage to river ecosystems and are commonly used in aquatic ecological health assessments. We investigated the zoobenthos in the lower reaches of the Dongjiang River. For the first time, we establish a benthic-index of biotic integrity (B-IBI) evaluation system for assessing damaged rivers in this region, and explore the main factors influencing aquatic ecological health. The results demonstrate that the B-IBI values of reference sites range from 2.23 to 3.53, indicating excellent or good conditions. In contrast, the B-IBI values of damaged rivers range from 0.04 to 2.61, with most of them being in poor health, including both poor and very poor states accounting for 45%. Dissolved oxygen, COD_Cr, BOD₅, ammonia nitrogen, total phosphorus, and anionic surfactants exhibit significant correlations with B-IBI values. Water pollution emerges as the primary cause for the deterioration of river ecosystems. Additionally, the high-intensity development and construction activities around rivers negatively impact zoobenthos, particularly aquatic insect communities. For tidal reaches, we recommend selecting targeted parameters to construct an evaluation system and establish evaluation standards when conducting B-IBI assessments.
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  Impacts of Cascade Development of Xiangjiang River on Waters with Suitable Flow Velocity for Reproduction of Four Major Chinese Fishes

  CAO Yan-min, QIAN Dong-yue, WANG Chong-yu

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 39-46. https://doi.org/10.11988/ckyyb.20221308

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  Appropriate flow rate is an important factor affecting the reproduction of domestic fish. This study focuses on determining the suitable flow velocity and acceleration for spawning in domestic fish spawning grounds, as well as the area of water with the appropriate velocity for fertilization. To achieve this, simulations and comparisons were conducted on typical non-constant high and low flow processes before and after cascade development. Results indicate a significant change in the water area suitable for the reproduction of four major Chinese carps. The optimum flow rate for spawning, the flow rate triggering spawning, the suitable flow rate for spawning, the maximum flow rate for fertilization, and the water area for maximum fertilization rate all declined drastically after the cascade development. Cascade development is unfavorable for domestic fish reproduction. However, concerning the suitable acceleration for domestic fish spawning, the regulation effect of cascade development on low flow tends to be advantageous. These findings pose further scientific requirements for the ecological joint operation and scheduling of cascades in the mainstream of the Xiangjiang River based on flow regulation.
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  Spatio-temporal Changes of Ecological Service Value Based on Improved Equivalent Factor Method: Case Study on Yangtze River Basin

  SHEN Meng-shu, ZHENG Hang, LIU Yue-yi, CHEN Jin, YIN Zheng-jie

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 47-54. https://doi.org/10.11988/ckyyb.20220264

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  The evaluation of ecological service value serves as a foundation for ecological protection and management by assessing the value of regional ecosystems. However, evaluating the ecological service value of the Yangtze River Basin (YRB) is challenging due to its vast spatial scale and complex ecological and socio-economic systems. Current methods are limited in their ability to effectively provide a comprehensive overview of the ecological service value in the YRB. To address this limitation, we have developed an advanced method based on equivalent weight factors for the evaluation of ecological service value in the YRB for the years 2010, 2015, and 2018. Results manifest that: (1) the equivalent factor method is applicable to large river basins as it offers relatively lower calculation costs compared to other methods; (2) the total ecological service value of the YRB in 2010, 2015, and 2018 were 5 889.347 billion yuan, 5 886.502 billion yuan, and 5 950.627 billion yuan, respectively; (3) the ecological service value in most of the upper reaches exhibited an increase, while in the Sichuan Basin and the plains in the middle and lower reaches generally decreased; (4) due to recent protection efforts for the Yangtze River, the ecological assets along the river and lakes in the middle and lower reaches have significantly increased. These findings provide reference information for exploring the applicability of the equivalent factor method in evaluating the ecological service value of the YRB. Moreover, they offer valuable data for understanding the changing trends of ecological assets in the basin.
Soil and Water Conservation and Ecological Restoration
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  Regionalization of Urban Soil and Water Conservation and Strategies of Controlling Soil Erosion: Case Study on the City of Shenzhen

  ZHANG Wen-jie, HUANG Jin-quan, XU Wen-sheng, WEN Xia-wei, ZHANG Zhi-hua, NIE Wen-ting, GAO Yang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 55-60. https://doi.org/10.11988/ckyyb.20220283

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  New urbanization is a crucial strategy for China’s economic and social development in the new era. The increasing demands for environments and resources resulting from urbanization necessitate a focus on high-quality development in the field of soil and water conservation. Shenzhen, as a highly urbanized area, has been at the forefront of urban water and soil conservation efforts. However, there is a lack of suitable regionalization that accounts for its high-density economic units, high-tech industries, and high-quality environment. An index system is established for soil and water conservation regionalization using mathematical statistical methods. By employing hierarchical cluster analysis and GIS spatial superposition analysis, a regionalization scheme based on street level, which represents the lowest administrative level, is delineated. Additionally, major measures and strategies for preventing and controlling soil and water loss in each region are proposed in consideration of the characteristics of soil and water loss as well as the orientation of economic and social development. Importantly, the regionalization scheme aligns with the prevailing pattern of urban space expansion and internal function adjustment. These results can serve as guidance for regionalization approval, classified management, and hierarchical prevention and control of soil and water conservation in Shenzhen.
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  Characteristics of Rill Erosion of Deposit Slope Formed by Power Transmission Project in a Typical Red Soil Region in China

  LI Xi, LIU Qiang, JIANG Shi-xiong, SUN Bao-yang, QIAN Feng, CHEN Yao

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 61-67. https://doi.org/10.11988/ckyyb.20220399

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  Indoor artificial rainfall experiment was conducted to address the soil and water loss of deposit slopes caused by the construction of power transmission projects in typical red soil region. Three rainfall intensities (2, 2.5 and 3 mm/min) and two slope gradients (10°and 15°) were designed in the experiment. The relationships between rainfall intensity, slope gradient, sediment yield characteristics and rill erosion features (density, fragmentation, tortuosity complexity, and width-depth ratio) were analyzed. Results manifest that under different rainfall intensities, both sediment yield and infiltration rate on the red soil deposit slope decreased with the increasing of rainfall duration, while runoff yield increased with the elongation of rainfall. The density, fragmentation, tortuosity complexity, and width-depth ratio were 0.77-1.35 m/m², 0.04-0.08, 0.91-1.40, and 1.01-2.39, respectively, among which the width-depth ratio reduced with the increase of rainfall intensity and slope gradient, whereas the former three parameters exhibited the opposite trend. The erosion rate was mostly correlated with the tortuosity complexity of rill, and less correlated with the fragmentation, density, and width-depth ratio of rill in sequence. The research findings provide technical parameters and a basis for preventing soil erosion in red soil areas induced by the construction of power transmission projects.
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  Constructing a Compensation and Balancing Mechanism for Natural Ecological Space Occupation in Hubei Province

  JIA Bao-jie, ZENG Wen-hao, ZHANG Ya-quan, MENG Han-long, HUANG Zhuo, CHEN Jin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 68-72. https://doi.org/10.11988/ckyyb.20220582

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  Constructing a compensation system for the occupation of natural ecological space is an important approach to address the imbalance between economic and social development and environmental protection. First, the current status and issues related to natural ecological occupation compensation, the characteristics of natural ecological space, and the classification of occupation behavior were analyzed. Subsequently, three modes of compensating natural ecological space occupation were proposed: in-situ compensation, off-site compensation, and financial compensation. Furthermore, the paths and procedures for the compensation were outlined within the policy system of Hubei Province. Differentiated compensation schemes should be selected based on different occupation behaviors. Control measures should be applied at four levels: avoidance, minimization, restoration, and compensation. Additionally, ecological expropriation and replenishment repository, monitoring and information sharing system, and public participation mechanism are recommended to ensure a smooth compensation.
Water-Related Disasters
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  Quantitative Analysis of Flood Peak Attenuation Capacity of the Three Gorges Reservoir Facing Historical Floods

  WANG Suo-ping, MA Yi-yang, ZHU Di, YAO Hua-ming, WANG Xian-xun

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 73-77. https://doi.org/10.11988/ckyyb.20220545

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  To quantify the peak-cutting of flood control storage capacity of the Three Gorges Reservoir (TGR), an optimization-fitting framework was employed to calculate the historical storage flood data. Various maximum water level schemes during scheduling were set at first, and a dynamic planning algorithm within the framework was utilized to optimize and solve different incoming floods. By doing so, the flood peak reduction curves under different flood control storage capacities were obtained. Furthermore, regression analysis was employed to quantify the peak-cutting of flood control storage capacity of TGR. Results demonstrate that the correlation between the utilization of the flood control storage capacity in TGR and the reduction of flood peak flow can be classified into three types: “flat curve following an increment”, “segmented increment”, and “linear increment”. The first two types exhibit inflection points, suggesting that the flood control storage capacity should be maintained below a specific threshold to fully maximize its efficient peak-cutting capacity. As for the third type, the flood control storage capacity can be planned rationally for dispatching in line with the flood peak reduction target. The findings provide valuable insights for the scientific and rational allocation of flood control storage capacity in the Three Gorges Reservoir.
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  Evaluation of Urban Waterlogging Control Based on Cloud Model

  HU Can-can, ZHOU Lan-ting, DENG Si-yuan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 78-84. https://doi.org/10.11988/ckyyb.20221162

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  To assess the overall status of waterlogging control in cities, we developed an evaluation index system consisting of 17 indices spanning four key aspects: construction of waterlogging prevention project, management of waterlogging prevention, intelligent waterlogging prevention, and ecological space management. By using cloud model, we evaluated the overall effectiveness of urban waterlogging control in Yandu District of Yancheng City, a low-lying area in Jiangsu Province. Results reveal a comprehensive score of 85.11 for urban waterlogging control in the study area, reflecting a good level of waterlogging control. The proposed method proves effective in assessing urban waterlogging control as it identifies areas in need of improvement, thus providing valuable insights for addressing any existing weaknesses.
Hydraulics
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  Numerical Calculation of Flow Field at Blind Tee-junction and Influencing Factors of Local Resistance Coefficient

  WU Sen-lin, WANG Qiu-liang, GAN Du-fen, LI En, WANG Yi-fan, LIU Yun

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 85-92. https://doi.org/10.11988/ckyyb.20220526

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  Blind tee, as an essential component in pipeline networks for transmission and distribution systems, plays a crucial role in ensuring stable pipeline operation. In this study, a model was established using Solidworks 2019 and Fluent to perform three-dimensional flow field calculations. The local resistance coefficient of the blind tee was analyzed by combining orthogonal analysis tests and SPSS software analysis. Empirical formulas were derived to explain the influence of each factor on local resistance coefficient. An optimal runner structure model was developed. The results indicate that the local resistance loss coefficient (ζ) decreases quadratically with increasing Reynolds number (Re) and branch pipe diameter (d), and increases quadratically with increasing included angle (θ) of the branch pipe. Furthermore, ζ decreases linearly with increasing blind end length (L₃). Through multivariate nonlinear regression, a correlation formula for the local resistance coefficient of the blind tee was derived. The fluid velocity near the right wall of branch pipe increases, and the distribution of turbulent kinetic energy at the bifurcation and branch pipe becomes more pronounced. Within the simulated range, the influence of each factor on ζ can be ranked as follows: Reynolds number > included angle > branch pipe diameter > blind end length. The smallest combination of local resistance loss coefficient was observed when the Reynolds number was 6.4×10⁵, the included angle was π/6, the branch pipe diameter was 0.9D, and the blind end length was 4.0D. The research findings provide a theoretical basis for blind tee structure design and engineering applications.
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  Experimental Study on Jet Trajectories and Scour Regularities of Narrow Slit-bucket in Asymmetrical River

  XU Li-zhe, YUAN Hao, HE Xiao-long

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 93-97. https://doi.org/10.11988/ckyyb.20220488

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  The jet trajectory and scour characteristics of a narrow slit-bucket with different shrinkage ratios in an asymmetric river channel were examined via model test of a hydropower station. The findings demonstrate that the shrinkage ratio of the narrow slit-bucket significantly influences the morphology of the scour pit. As the shrinkage ratio decreases, the sidewalls of the bucket constrict the water flow, while the jet disperses more effectively in the air, thus increasing energy dissipation, and consequently resulting in a decrease in scour pit depth and an increase in scour extent. For asymmetric riverbeds, the scour depth amplifies with an increasing β value at a given flow rate. However, the lateral spread of scour notably reduces. Furthermore, a comparative analysis was conducted to calculate the jet trajectory. The results reveal that the calculation result of Chen Zhongru’s formula agrees well with test values when shrinkage ratio (β) is greater than 0.2. When β=0.2, the modified formula from the hydraulic calculation manual proves to be a better choice for calculating the jet trajectory.
Rock-Soil Engineering
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  Application of Partially-closed Impervious Curtain to Foundation Pit Dewatering

  YAN Bo, TAI Jun, HU Ke, XU Wei, HAN Shuai

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 98-105. https://doi.org/10.11988/ckyyb.20220477

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  Numerical simulation is employed to analyze the groundwater control effect of super-large deep foundation pit dewatering using partially suspended impervious curtains and partially closed impervious curtains. The influence of different rates of closed impervious curtain (R_c) on the dewatering process and its impact on adjacent subway tunnels are investigated. The findings reveal a gradual decrease in the influence of dewatering on the surroundings at a given R_c as the insertion ratio (L/M) of the suspended impervious curtain increases, with a distinct turning point. Therefore, an economical and reasonable insertion ratio can be determined based on the descending depth variations of the pressure water head. L/M exhibits minimal influence on the water pumping capacity (q) per unit area. In contrast, R_c significantly affects q, showing a good linear correlation when R_c ranges from 0% to 80%. A comparison between calculated results and field monitoring data indicates a notable difference in water head between the inside and outside of a foundation pit, favoring the closed impervious curtain side over the suspended impervious curtain side. Consequently, partially closed impervious curtains prove effective in controlling groundwater seepage in sensitive surrounding areas. Furthermore, deformation calculation results of subway tunnels under different values of R_c could help determine the minimum R_c required to meet deformation requirements. Therefore, partially closed impervious curtains can be employed flexibly in the impervious curtain design for large foundation pits depending on the sensitivity of the surroundings.
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  Effects of Herb Root Type and Distribution on Unconfined Compressive Strength of Root-Soil Composites

  LIU Xiang-feng, ZHANG Qiang, HAO Guo-liang, WANG Yi-teng, SUN Ying-cong, WANG Lai-gui

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 106-111. https://doi.org/10.11988/ckyyb.20220407

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  To investigate the impact of herb root type and distribution on the unconfined compressive strength of root-soil composites, the root distribution characteristics of cluster-root Viola philippica, tiller-root Ixeris polycephala, and rhizome-root Triglochin Palustre within different soil depths were determined using an image pixel conversion algorithm. Stress-strain curves of the three herb-root-soil composites were obtained through unconfined compressive tests. The relationship between root parameters and cohesion increment of the failure surface of the root-soil composites was examined by quantifying the compressive strength. Results indicated that within the 0-8 cm soil depth range, the root length density (RLD), root surface area density (RASD), and root area ratio (RAR) of Viola philippica and Triglochin Palustre gradually decreased with increasing soil depth, while Ixeris polycephala displayed an increasing trend followed by a subsequent decrease. Quantitative root distribution parameters of Viola philippica ranks first, followed by Triglochin palustre and Ixeris polycephala in sequence. Rhizome-root Triglochin palustre exhibited the highest ability to improve soil compressive strength, with the cohesion increment of its root-soil composite being 1.42 and 2.6 times those of Viola philippica and Ixeris polycephala, respectively. Triglochin palustre has the largest RLD, RASD and RAR of the failure surface, followed by Viola philippica and Ixeris polycephala in sequence. No correlation was observed between root parameters and cohesion increment of the failure surface of Ixeris polycephala. For cluster-root and rhizome-root herbs, RAR has larger correlation with cohesion increment than RLD and RASD do. Therefore, RAR can serve as an important predictor of soil compressive strength improvement for cluster and rhizome root types.
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  Influence of Fracture and Heavy Rainfall Infiltration on Seepage Field and Stability of Accumulation Landslide

  FU Jing, AI Kai, SHI Hua-tang, GAO Yang-yang, TAN Hai, WU Yong-jin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 112-117. https://doi.org/10.11988/ckyyb.20220564

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  Rainfall infiltration temporarily increases water pressure in the unsaturated area above the groundwater level of a landslide, reduces matrix suction, and weakens the shear strength of the slope. Meanwhile, cracks in the landslide facilitate rapid rainwater infiltration. During rainy season, intense rainfall accumulates and forms a transient water source in areas with more developed cracks in the slope. Continuous recharge results in high pore dynamic water pressure, leading to a rise in the groundwater level of deep landslide. This transient movement of groundwater and the associated additional water load become controlling factors for slope instability during rainy season. In this study we focus on large-scale accumulation landslides. Based on the saturated-unsaturated seepage theory of soil mass, we examined the influence of transient water sources formed by heavy rainfall at the end of cracks in the slope on the seepage field and groundwater level of landslide using finite difference method. We evaluated the adverse effect of transient water supply on the stability of the landslide by using the strength reduction method. The research findings provide a scientific basis for landslide prevention and the design of drainage treatment.
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  Model Test on Bearing Behaviors of Battered Piles under Horizontal Eccentric Loads

  CAO Wei-ping, LI Qing-yuan, TAO Peng, ZHAO Min

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 118-125. https://doi.org/10.11988/ckyyb.20220430

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  The bearing deformations of battered piles are intricate due to the asymmetrical stress field exerted by the self-weight of the surrounding soil. Model tests were conducted on battered piles embedded in sandy soils to investigate their bearing deformation behavior under horizontal eccentric loads perpendicular to their inclination direction. The study also revealed the effects of pile surface roughness and pile shaft inclination angle on the bearing deformation characteristics of battered piles, as well as the internal forces acting on the pile shaft. Test results manifest that under horizontal eccentric loads perpendicular to the inclined direction of battered piles, the horizontal displacement of the pile head is minimal, while torsional deformation is significant. The bearing capacity of battered piles primarily relies on their torsional bearing capacity. When a horizontally applied eccentric load is perpendicular to the pile’s inclination, the battered pile not only undergoes bending but also experiences tension along its longitudinal axis. The maximum bending moment induced in the battered pile shaft by the horizontal load exceeds the torque moment applied at the pile top by approximately 10% to 30%. The entire battered pile shaft is subjected to tension, although the tension is relatively small, with a maximum tensile force equal to around 5% of the horizontal load applied at the pile head. The pile shaft is also subjected to longitudinal and circumferential skin frictions. The upper shaft exhibits positive longitudinal skin friction, while the lower shaft exhibits negative friction, with the neutral point located at a depth of Z/L=0.3. The average longitudinal skin friction is considerably smaller than the average circumferential skin friction at the same depth.
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  Experimental Study on Self-healing Effect of Slip Zone Soil in Red-bed Translational Landslide

  ZHOU Hang, ZHENG Da, ZHANG Wen

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 126-132. https://doi.org/10.11988/ckyyb.20220450

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  The mechanical properties of slip zone soil play a crucial role in determining whether a reactivated landslide will slide again. In previous studies, the residual strength of slip zone soil has been regarded as a static parameter. However, recent research has revealed a self-healing effect in which the strength of slip zone soil increases in stable period. This self-healing effect needs to be considered in the stability analysis of reactivated translational landslides. In this study, a shear-consolidation-shear test was conducted on the slip zone soil of a red-bed translational landslide. The aim was to investigate the self-healing of residual strength of slip zone soil under different normal stresses and consolidation durations. The findings demonstrate the presence of a self-healing effect in slip zone soil. The initiation strength of reactivated landslide falls between its peak strength and residual strength. Moreover, the strength recovery ratio of slip zone soil is directly proportional to consolidation duration and inversely proportional to normal stress. The thixotropy of slip zone soil in translational landslides is the main factor underlying the strength healing mechanism, with the mineral characteristics contributing to some extent. In conclusion, the strength healing mechanism of slip zone soil significantly influences the reactivation and initiation sliding of translational landslides.
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  Regularities of Particle Gradation Change Before and After Soft Rock Fill Tests

  SUN Xiang-jun, PAN Jia-jun, DING Li-hong, ZHOU Yue-feng, LU Yi-wei, ZUO Yong-zhen

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 133-138. https://doi.org/10.11988/ckyyb.20220355

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  To investigate the variation law of particle grading in soft rock fill before and after testing, a series of large-scale experiments were conducted on soft rock fill in the construction of two reservoir dams. Quantitative analysis was performed using the Marsal particle crushing rate and grading equation parameters. Results are as follows: 1) In the compaction tests, the Marsal particle crushing rate reaches its maximum value near the optimum moisture content. 2) With increasing confining pressure, the Marsal particle crushing rate increases in the triaxial tests. However, such rate increase becomes less significant when a specific confining pressure is reached. 3) The Marsal particle crushing rate in super-large-scale compaction tests is higher than that in large-scale compaction tests. The rate of Marsal particle crushing after wetting and creep tests is lower than that in saturated triaxial tests. The Marsal particle crushing rate in large-scale lateral compression tests is also lower than that in triaxial tests. 4) Parameters of the grading equation show a monotonic change before and after the tests, tending to converge to a specific value. These research findings provide a scientific basis for optimizing the grading design.
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  Influence of Dynamic Load on Stability of Deep Foundation Pit Excavation with Micro-piles

  WANG Chun-jing, BU Yi-ming, WANG Jin-xing, LIANG Bin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 139-146. https://doi.org/10.11988/ckyyb.20220334

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  To investigate the impact of dynamic loading on the stability of adjacent bridges with micro-pile deep foundation pits, this study focuses primarily on the Ubisa-Shorapani (F3) section of Georgia E60 Expressway, which is a significant project contributing to China’s “Belt and Road” initiative. Numerical simulation is employed to analyze the effects of train loads on the foundation pit soil as well as the internal forces and deformation of the supporting structure. The results obtained from the numerical calculations are then compared with the data collected from on-site monitoring. The findings reveal that under the influence of train loads, the maximum displacement of pile near the train side and the maximum settlement of the soil increase by approximately 14.5% and 20%, respectively. Moreover, the overall safety factor of the foundation pit decreases by 0.1. Therefore, it is crucial to fully consider the impact of train loads on the stability of the foundation pit during the excavation process. The initial support is particularly affected by different loading modes, and the range of change in axial force for each support gradually decreases as the excavation progresses from top to bottom. When the train load is positioned 5 m away from the boundary of the foundation pit, the settlement of the soil near the train side is 3.61 mm greater compared to a load distance of 20 m. At a load distance of 20 m, soil settlement experiences minimal influence from the train load, resulting in improved stability of the foundation pit. The dynamic load exerted by the train greatly affects the internal forces of the neighboring pile. The magnitude of bending moment and the depth at which the maximum bending moment occurs increase gradually as the load distance decreases. Specifically, when the dynamic load speed is set at 120 km/h and the distance is 5 m, the pile experiences significant load-induced effects. The bending moment increases by 210 kN·m, and the depth at which the maximum bending moment occurs rises compared to the scenario without train load.
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  A Small Shake Table Model Test on Soilbag Cushion with Different Structural Forms

  CHEN Shuang, FANG Bin-xin, LIU Si-hong, LU Yang, LI Bo-wen, ZHAO Tong-le, GU Yi-ming

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 147-154. https://doi.org/10.11988/ckyyb.20220397

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  To investigate the influence of structural form on the vibration reduction and isolation effect of soilbag foundations, a series of small shake table model tests were conducted. The influential factors primarily consisted of the peak ground acceleration (PGA) of the input motion, the arrangement form of the soilbag foundation, the retaining structure, and the interspace between adjacent soilbags. Test results demonstrate that a higher PGA yields a greater impact on the vibration reduction and isolation of soilbag foundations, irrespective of the arrangement form. By comparing the acceleration response within model foundations featuring different soilbag arrangement forms, we found that the interlaced soilbag foundation exhibited a significant effect on the attenuation of vibration waves. Furthermore, the presence of a retaining structure within the foundation trench effectively enhances the vibration reduction and isolation effect of soilbag foundations, and also prevents the surrounding soil from falling into the interspace between soilbags. Additionally, maintaining an appropriate interspace between soilbags proved to be advantageous in maximizing the benefits of vibration reduction and isolation in soilbag foundations.
Engineering Safety and Disaster Prevention
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  Image Generation for Surface Defects of Underwater Structures Based on Deep Convolutional Generative Adversarial Networks

  CHENG Feng-wen, GAN Jin, LI Xing, WU Wei-guo

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 155-161. https://doi.org/10.11988/ckyyb.20220421

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  The aim of this study is to improve the quality and quantity of the dataset for surface defect images of underwater structures and facilitate the application of deep learning methods in underwater detection. A method for generating surface defect images of underwater structures is proposed based on the deep convolutional generative adversarial networks (DCGAN). First, the image quality is guaranteed by designing an underwater image acquisition device through the adjustment of shooting distance and the supplement of light intensity. Second, by improving the loss function and optimizing DCGAN, the image generation model for surface defect of underwater structures is established. Finally, the effectiveness of the generated images is assessed using the YOLOv5 detection network. The results demonstrate an average peak signal-to-noise ratio of 21.142 6 dB and an average structural similarity of 0.716 8 for the generated crack images of underwater structures. Integrating the generated and real images into the detection model effectively improves the accuracy of detection. The study provides technical support for the health detection of hydraulic structures such as dams and headrace tunnels.
Hydraulic Structure and Material
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  Inverse Analysis of Arch Dam Thermal Parameters Based on Cross-Global Artificial Bee Colony Algorithm

  MAO Da-wei, ZHANG Ao, WANG Feng, ZHOU Yi-hong, TAN Tian-long

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 162-169. https://doi.org/10.11988/ckyyb.20220456

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  Affected by factors such as ambient temperature, cooling water, and surface insulation, the actual thermal parameters of arch dam during construction differ remarkably from laboratory test results. Based on temperature data obtained by using distributed optical fiber sensor, we employed the cross-global artificial bee colony (CGABC) algorithm determine the concrete thermal parameters of Baihetan double-curvature arch dam and capture their real-time variations. To address the slow convergence and susceptibility to local optimals encountered by traditional artificial bee colony (ABC) algorithm in obtaining the optimal function value, we developed the CGABC which integrates the concept of global optimal solutions from particle swarm optimization (PSO) and the cross-operation strategy of genetic algorithm (GA). By considering the influence of multi-stage cooling water and environmental temperature, we employed CGABC for the inversion of concrete thermal parameters of Baihetan arch dam. The inversion results demonstrate a favorable agreement between CGABC-calculated values and measured temperatures. In conclusion, CGABC exhibits excellent adaptability in the thermal parameter inversion of arch dams.
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  Effect of PVA Fiber Mixed with Nano-SiO₂ on Fatigue Resistance of Concrete and Its Microscopic Mechanism

  KONG Zheng-yu, LU Jing-zhou, WANG Jian-wei, WANG Wei-liang, HAN Wen-yu, XIAO Ying

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 170-175. https://doi.org/10.11988/ckyyb.20220356

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  This paper presents an experiment aimed at investigating the influence of blending PVA fiber and nano-SiO₂ on the fatigue resistance of concrete.The experimental specimens are divided into three groups: blending PVA fiber only (Group P),nano-SiO₂ only (Group S),and PVA fiber mixed with nano-SiO₂ (Group SP).Uniaxial compression tests were performed on the specimens subjected to multiple-cycle fatigue loading, and the resulting data were used to assess their fatigue resistance.The relative dymanic elastic modulus and compressive strength of specimens after the tests were taken as the assessment indices.Additionally,SEM was employed to observe and analyze the microscopic action mechanism.The findings reveal that all three concrete groups exhibit a notable improvement in fatigue resistance compared to ordinary concrete,although the manner of improvement differs.Group S demonstrates the most notable enhancement in concrete strength, while group SP effectively suppresses the development of internal degradation in concrete. In terms of the underlying mechanisms,PVA fibers enhance the tensile capacity between concrete elements,effectively reducing damage and failure under fatigue loads, thereby prolonging the concrete’s failure process.Nano SiO₂ participates in the reaction to generate C-S-H (calcium silicate hydrate) gel,filling the weak areas of the concrete and improving its compressive strength,thus raising the starting point of failure under fatigue loads.These findings provide valuable insights for the design of fatigue-resistant concrete structures.
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  Effect of α-Hemihydrate Gypsum on Comprehensive Performance of Cement Mortar Doped with Iron Tailings

  HUANGFU Jing-qi, HE Qiang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 176-180. https://doi.org/10.11988/ckyyb.20220322

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  To enhance the performance of cement mortar modified with iron tailings, a specific proportion of α-hemihydrate gypsum was incorporated into the mortar to prepare test specimens. The effects of α-hemihydrate gypsum content and iron tailings content on the fluidity, drying shrinkage, mechanical properties, and durability of cement mortar were investigated. The hydration mechanism was examined through mineral composition and microscopic image analysis. The findings indicate that the addition of α-hemihydrate gypsum significantly increases the slump index and reduces drying shrinkage rate in the mortar. When the replacement ratio reaches 15%, the compressive strength, flexural strength, and durability of the mortar doped with α-hemihydrate gypsum achieve optimal conditions. The chemical activity of α-hemihydrate gypsum promotes secondary hydration, subsequently enhancing the density and various indicators of the mortar. The test results serve as a valuable reference for modifying environmentally friendly, low-carbon, and high-performance cement mortar.
Water Conservancy Informatization
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  Inversion of Water Quality Parameters in Jianghan Plain Based on Sentinel2-L1C Image

  ZOU Zhi-ke, YU Lei, ZHANG Yu, WANG Wen-juan, ZHAO Yong-li, SUN Jian-dong, CHENG Qing-lei

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 181-187. https://doi.org/10.11988/ckyyb.20220515

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  Remote sensing technology has emerged as a powerful tool for monitoring inland water quality. To investigate changes in concentrations of total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD) in the aquaculture area of Jianghan Plain, we developed inversion models utilizing Sentinel2-L1C remote sensing data. These models are based on three optical active substances: water transparency, suspended matter concentration, and Chl-a concentration. By correlating the calculated water transparency, suspended solids concentration, and Chl-a concentration with TP, TN, and COD concentrations at regional water fitting points, we established indirect inversion models to estimate the concentrations of these substances and validated the models using fitting points data. Our results demonstrate a strong correlation between water transparency and TP concentration. Higher water transparency indicates better water quality and lower TP concentration. The concentration of suspended matter in water is highly correlated with the TN concentration. Increased suspended matter concentration indicates inferior water quality and higher TN concentration. Additionally, higher water Chl-a concentration corresponds to higher COD. The deterministic coefficients of the indirect fitting models for TP concentration, TN concentration, and COD were all greater than 0.6. Furthermore, the TP concentration, TN concentration, and COD concentration in water bodies of monitoring points in Jianghan Plain were simulated. The results align with the expected patterns in feeding period and reflect the spatio-temporal evolution of water quality parameters in the aquaculture areas of Jianghan Plain. This research contributes practical insights into understanding the dynamics of large-scale water quality parameters in aquaculture areas.
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  Investigation and Cause Analysis of Dangerous Rock Masses on High and Steep Slope Based on Airborne LiDAR and UAV Imagery

  XIA Xiong-bin, QIAO Li-jia, XU Wan-zhong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(9): 188-194. https://doi.org/10.11988/ckyyb.20220394

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  In water conservancy and hydropower projects, dangerous rock masses often develop in hidden areas of high and steep slopes, posing challenges for accurate surveying and measurement using conventional methods. Swiftly and conveniently identifying dangerous rock masses on such slopes is of significant engineering importance. To address this issue, we take the investigation findings of dangerous rock masses outside the opening line of slope for critical building at Huangdeng Power Station as the research basis. We constructed a 1∶500 scale 3D model of the actual scene using UAV (unmanned aerial vehicle) oblique photography. By using airborne LiDAR remote sensing measurement technology, we acquired high-precision LiDAR point cloud data and optical image data in the research area. By incorporating a 3D visual remote sensing interpretation platform, we established the interpretation marks for dangerous rock mass, allowing for the extraction of structural plane characteristics of these rock masses. Furthermore, we conducted in-depth field investigations and review of the interpretation results. Our review work confirms the robust accuracy of remote sensing measurement technology in the initial stage, with highly credible interpretation results. Furthermore, by employing a geospatial data analysis method, we explored the development distribution patterns and genesis mechanisms of dangerous rock masses. The findings demonstrate that dangerous rock masses in the study area predominantly develop in the elevation range from 1 609 m to 1 963 m and the slope gradient range from 40° to 70°, primarily facing the south direction. Additionally, dangerous rock disasters is also affected to some extent by river systems and human engineering activities. The research findings hold significant reference value for the identification and causal analysis of high-risk rock masses in hydropower reservoir areas.