01 April 2024, Volume 41 Issue 4

    

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  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 0-0.

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Original article
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  Reflections on Planning and Management of Water Resources Protection in the Yangtze River Basin in the New Era

  LIU Zhao-xiao

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 1-7. https://doi.org/10.11988/ckyyb.20231244

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  Compiling and implementing water resources protection plan is a legal obligation entrusted by the state to the water administration department, and is also a pivotal endeavor in fulfilling the responsibilities of water resources management and ecological preservation. The evolution of water resources protection planning in the Yangtze River Basin, encompassing inception, exploration, practice, and system refinement, has propelled the scientific and systematic advancement of water resources preservation and management within the basin. Against the backdrop of national institutional reforms and the enactment of the Yangtze River Protection Law, this study systematically examines the developmental trajectory and efficacy of water resources protection planning in the Yangtze River basin. It scrutinizes the current challenges and nuances confronting basin-wide water resources preservation while delineating the strategic direction and principles for future endeavors. Drawing from these insights, the paper proposes actionable recommendations and strategic measures for enhancing the planning and management of river basin water resources in the new era. The research findings hold paramount importance in consolidating consensus on basin water resources protection planning, instituting a robust planning framework for the new era, fostering the high-quality development of water resources protection, and advancing the modernization of river governance.

Comprehensive Management Of River Basin
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  Mechanism of Paid Utilization of Shoreline in Jiangsu Segment of Mainstream Yangtze River

  DA Bo, LI Yi-peng, HUANG Cheng-geng, LIAO Ying-di, HOU Li-jun, CHEN Da

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 8-13. https://doi.org/10.11988/ckyyb.20221501

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  To enhance the rational and efficient utilization of Yangtze River shoreline resources, we examine the current management status of the Jiangsu segment and propose comprehensive management measures tailored to its protection and utilization. Despite notable achievements in the Yangtze River protection strategy in Jiangsu, shortcomings persist, notably insufficient comprehensive management and unified planning along the shoreline. Recommendations include enhancing the joint conference system for comprehensive shoreline management, establishing a provincial-level task force for Yangtze River shoreline protection, and implementing unified management strategies. Considering water area and land area factors along the shoreline, we introduce the shoreline grade coefficient and utilization efficiency coefficient to optimize the paid use method for shoreline resources, exploring a paid-use mechanism for the Jiangsu segment of the Yangtze River's mainstream. This approach aims to effectively promote the rational development and utilization of Yangtze River shoreline resources.
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  Evaluation of Water Source Conservation Service Value and Its Spatial Transfer in Yangtze River Basin

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

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 14-22. https://doi.org/10.11988/ckyyb.20221559

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  The transfer of water source conservation service value between different regions is the key content to be considered in the horizontal ecological compensation between the upstream and downstream of river basin. This transfer is dependent upon the basin's hydrological cycle path and river water transport. However, the current method for evaluating the transfer of water source conservation service value lacks an account of hydrological characteristics, thus requiring an enhancement of the rationality of evaluation results. Addressing this issue, the present study enhances the fracture point-field intensity model from two perspectives: transfer direction and transfer path. Firstly, the introduction of the river direction coefficient aids in assessing the hydraulic connection between the basin's upstream and downstream, as well as its main and tributary regions. Secondly, the assessment of water source conservation service transfer takes into account the hydrological characteristics of rivers, with particular application to the Yangtze River Basin (YRB), thereby improving the rationality and applicability of assessment outcomes. The findings reveal that the water source conservation capacity of the YRB in 2020 reached 1 153.85 billion m³, with the associated value of water source conservation service amounting to 1 195.38 billion yuan. In contrast to the evaluation results obtained from existing models, the present enhanced fracture point-field intensity model underscores the transfer of water source conservation service value from upstream to downstream, and amplifies the transfer intensity and range. Within the YRB, the water source conservation service value transferred from Sichuan ranks the top, followed by Jiangxi, Hunan, Guizhou, Hubei, Anhui, Chongqing, Yunnan, Zhejiang, Qinghai, Shaanxi, Guangxi, Xizang, and Henan in descending order; the service value received by Yunnan is the largest, followed by Anhui, Hubei, Chongqing, Jiangsu, Hunan, Sichuan, Shanghai,and Xizang in descending order.
River-Lake Protection And Regulation
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  Physical Model Test on the Scale of Drainage Pump Station on Tidal River

  LIU Zhong-feng, HUANG Ben-sheng, LIU Da, LI Ming

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 23-28. https://doi.org/10.11988/ckyyb.20221583

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  Determining the optimal scale of pump station is a crucial aspect of designing drainage systems in tidal rivers.We constructed a physical model of a tidal river system and conducted experimental investigations on the scales of two pump stations situated at the outlets under selected hydrological boundary conditions and project operational requirements.Our study reveals that:(a) constrained by the river's discharge capacity, a critical scale exists for the pump station, beyond which the water level remains unaffected by further scale increments;(b) the extent of water level reduction due to drainage pumping correlates closely with the proximity of the pump station, with greater proximity resulting in more pronounced water level drops. Building upon these insights and conducting multiple trials, we propose an optimal scale combination for the two pump stations to meet design specifications:80 m³/s for the Wenchong Pump Station situated farther away, and 130 m³/s for the closer Jinzichong Pump Station. This research offers valuable data for optimizing design processes and serves as a reference for similar projects.
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  Influence Mechanism of Composite Conditioning of Sludge on Dehydration Performance of Mechanical Pressure Filtration

  LI Shi-mi, ZHANG Yang, XIA Xin-xing, CHEN Wen-feng, XU Yang-fan

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 29-36. https://doi.org/10.11988/ckyyb.20221576

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  Dehydration through mechanical pressure filtration is widely used for dehydrating river and lake sludge. The conditioning of the sludge significantly impacts the efficiency of mechanical filtration dehydration. Two common conditioning measures include utilizing flocculant with polyacrylamide (PAM) and employing a compound conditioning approach that combines flocculant with an inorganic conditioner. In recent years, compound conditioning methods have seen rapid development. Studying the impact of single and compound conditioning of flocculants on the efficiency and mechanism of mechanical filtration dehydration is crucial. Focusing on the sludge sourced from Guantian Lake, this study compares the conditioning performance of PAM and LAC and their dehydration performance, and analyzes the dehydration technical parameters in PAM and PAM+LAC conditioning cases. The effect of composite conditioning on the structure of dehydrated sludge cake is also revealed via mercury intrusion test and SEM scanning. Findings indicate that the conditioning agent primarily enhances the filtration and dehydration stages, as evidenced by water loss meter tests aligning well with the plate and frame mechanical filtration press results. The use of LAC as a supplement to PAM can improve the unloading performance of the sludge cake by enhancing conditioning effects. Microscopic analysis revealed that LAC enlarged the pore size of the sludge cake and increased the proportion of open pores.
Water Resources
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  Effects of Irrigation Change on Sustainable Utilization of Groundwater in North China Plain

  QIN Huan-huan, HUANG Li-xiang, WANG Jian-quan

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 37-45. https://doi.org/10.11988/ckyyb.20221475

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  In addressing groundwater utilization challenges in the North China Plain (NCP), we predicted the groundwater utilization trends over the next two decades considering the impact of altered irrigation practices by using the calibrated distributed hydrological MIKE SHE model. In the prediction we employed three distinct scenarios: the current situation maintenance scenario (MS1), an irrigation water volume change scenario (MS2), and an irrigation frequency change scenario (MS3). Our findings indicate that: 1) Groundwater levels present a consistent downward trajectory across all scenarios. The annual decline ranges from 0.335 to 1.648 m/a under MS1, 0.298 to 1.588 m/a under MS2, and 0.303 to 1.607 m/a under MS3. Particularly concerning is the emergence of groundwater depression cones in the eastern coastal and Beijing-Tianjin areas, with minimal mitigation observed from changes in irrigation practices. 2) Although modifying the irrigation facilitates some recovery in groundwater levels and aquifer storage, the impact varies. Decreasing irrigation frequency yields greater benefits compared to reducing irrigation water volume. Relative to MS1, MS2 and MS3 demonstrate potential to restore aquifer storage by 0.06 and 0.12 meters respectively over a 20-year period. 3) However, reliance solely on altering irrigation practices falls short in halting the ongoing depletion of groundwater resources in the NCP. A comprehensive, long-term approach integrating additional measures is imperative to ensure sustainable groundwater management in the region.
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  Joint Probability Analysis of Extreme Flood Events in the Source Flow Area of Yarkant River

  SI Han, HE Ying, XU Hui-min, LU Xiao-yue

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 46-54. https://doi.org/10.11988/ckyyb.20221523

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  Based on temperature data from Tashkurgan meteorological station and flood data from Kulukelangan station, we investigated the probability distribution characteristics of flood peak discharge and 1 d, 3 d, and 7 d total flood volume of Yarkant River by using Copula functions. Additionally, we explored the relationship between climate factor variations and extreme flood events through wavelet coherence analysis. Our findings indicate that the co-occurrence return period of two variables surpasses the single variable return period, which, in turn, exceeds the joint return period of two variables. Both the joint return period and the co-occurrence return period increase with the continuous rises in peak flow and flood volume, leading to a decreasing likelihood of corresponding extreme flood events. We also found a high coherence between summer daily average temperature and flood peak discharge series on an interdecadal scale. The summer daily average temperature tends to change 0.13-0.31 cycles prior to the occurrence of flood peak flow. By using Copula functions, we established a two-dimensional statistical model between summer daily average temperature and flood peak spanning from 1957 to 2010. Notably, as the return period of a single variable increases, the disparity between joint return period and co-occurrence return period of the corresponding two variables widens. As summer daily average temperature rises, the likelihood of floods in different return periods also increases. These research outcomes carry significant scientific value and offer technical support for the flood risk management and adaptive measures in the Yarkant River Basin.
Water Environment And Water Ecology
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  Refined Estimation and Empirical Study of Non-point Source Pollution Load in Small Watershed:A Case Study of Yanghua River Basin, Chengdu

  XIA Yu-chao, YUAN Yi-bin, ZHAN Lin, HE Chu, XIA Jian-xin

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 55-61. https://doi.org/10.11988/ckyyb.20221462

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  Accurately estimating non-point source pollution load is crucial for developing a standard-meeting water quality plan for the Yanghua River. By employing an improved output coefficient method, we estimated the total non-point source pollution load of Yanghua River small watershed, which is a tributary of the Tuojiang River. In consideration of the proportion of monthly rainfall in annual rainfall, we can obtain the refined estimation data of monthly distribution of non-point source pollution load. Our findings indicate that COD pollution in the watershed was most severe in 2020, with a total pollution load of 6 042.61 t, primarily concentrated in Zhuanlong Town, Zhugao Town, Hefeng Town, Yunlong Town, and Shijia Town. Non-point sources such as rural dispersed areas and large-scale livestock and poultry farming contributed significantly to pollutants such as COD, ammonia nitrogen, and total phosphorus. Additionally, we successfully obtained the preliminary monthly distribution of non-point source pollution load within the year. These results demonstrated good agreement with measured data, with an average error less than 10%. Overall, our research outcomes provide essential data support for the refined management of water environment in the basin.
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  Regularities and Modes ofHydrogeochemical Evolution of Groundwater in the North Piedmont of Qinling Mountains

  YUAN Lei, MA Tao, HAN Shuang-bao, LI Fu-cheng, WU Xi, LI Hai-xue

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 62-69. https://doi.org/10.11988/ckyyb.20221476

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  The northern foothills of the Qinling Mountains constitute a vital water source conservation area for the Yellow River. Examining the hydrogeochemical evolution patterns and models in this region holds paramount importance for the development and preservation of groundwater resources in the Qinling Mountains, and also helps advancing ecological protection and facilitating the high-quality development of the Guanzhong Plain and the broader Yellow River Basin. Utilizing data collected during the hydrogeological survey in the Weihe River Basin spanning 2019 to 2021, this study delves into the hydrogeochemical evolution patterns and models of groundwater from the Qinling to the Weihe River Valley. Employing multivariate statistics, and hydrogeochemical reverse simulation methods, the analysis reveals a shift from HCO₃-Ca to HCO₃·SO₄-Ca·Na in the hydrochemical composition of groundwater from the rocky substrate to the fine soil plain, with subtle zoning observed, accompanied by a rise in Total Dissolved Solids (TDS) concentration from 254 mg/L to 889 mg/L. The flow of groundwater indicates a shift in water-rock interaction dominance, transitioning from the weathering and leaching of carbonate rock to that of silicate rock and rock salt. Concurrently, cation exchange intensifies. Despite the rapid circulation and replenishment of groundwater, evaporation and concentration remain relatively insignificant. Groundwater age, as measured by ¹⁴C, predominantly falls within the range of 2 450 years. As a critical groundwater conservation area and runoff channel, the Qinling piedmont proluvial fan stays as a pivotal player in safeguarding the quality of both unconfined and confined water in the Guanzhong Plain. Due to the proluvial fan's limited resistance to pollution, it is imperative to bolster the protection of groundwater resources amidst ongoing groundwater development, industrial activities, and agricultural practices.
Soil And Water Conservation And Ecological Restoration
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  Characteristics of Runoff and Sediment Yield on Loose Red Soil Accumulation Slope under Gravel Action

  RUI Mao-gang, ZHOU Yan-chen, TAO Yu-quan, XIE Shu-yan, XUE Yang

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 70-77. https://doi.org/10.11988/ckyyb.20230683

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  This study aims to explore the runoff and sediment yield characteristics on loose engineering accumulations under different rainfall conditions. Based on field investigations, we developed models of accumulation test tanks for simulated rainfall experiments to examine the runoff and sediment yield disparities between pure accumulation and accumulation with 20% gravel content under varied rainfall conditions. The findings revealed the following: 1) Gravel effectively delayed runoff initiation on accumulation slopes, exhibiting an average delay benefit of 299.56%. Throughout the rainfall process, both pure and mixed soil and gravel accumulations demonstrated a similar increasing trend in runoff rate with prolonged runoff generation duration. The average runoff rate escalated by 34.48%-244.83% with rising rainfall intensity. In comparison to pure accumulation, mixed soil and gravel accumulation displayed a decrease in average runoff rate by 6.54%-45.83%, along with a reduction in average flow velocity by 13.76%-30.54%. 2) The erosion rate of both pure and mixed soil and gravel accumulations generally exhibited a gradual increase or tended to stabilize with runoff generation duration under rainfall intensities below 1.5 mm/min. The average erosion rate of mixed soil and gravel accumulation was 80.39%-84.95% lower than that of pure accumulation. However, under heavy rainfall conditions (2.0 mm/min), the erosion rate of pure soil accumulation experienced rapid escalation followed by a decline, while that of mixed soil and gravel accumulation increased in a fluctuating manner, with the average erosion rate 20.04% higher than the former. 3) Both rainfall intensity and gravel content significantly influenced runoff, sediment yield, and flow velocity on accumulation slopes, indicating notable differences overall (P<0.05). The overall trend displayed an increase in both water and sediment. These results offer scientific guidance for implementing measures against soil erosion in production and construction projects involving accumulations, and provide fundamental data for establishing soil erosion prediction models for accumulation engineering.
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  Simulation of Landscape Ecological Risk Change in Hanjiang River Basin under SSP-RCP Scenarios

  WU Qi-liang, ZHENG Hang , LIU Yue-yi, CHEN Jin

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 78-88. https://doi.org/10.11988/ckyyb.20221560

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  Landscape ecological risk assessment plays a vital role in identifying vulnerable ecosystem areas for targeted management. While current methods primarily rely on land-use change data for ecological risk analysis, they often lack a comprehensive evaluation of multiple factors, especially the prediction of landscape ecological risk dynamics under climate change scenarios integrating climate variations and socio-economic trends. To tackle this issue, we constructed a predictive model for ecological landscape risk influenced by diverse factors by integrating traditional landscape ecological risk assessment models with deep learning technique, and further applied this model to simulating the change in landscape ecological risks of Hanjiang River Basin. Findings reveal that: 1) during the baseline period (2000-2015), higher ecological risk levels predominantly clustered in the downstream of Danjiangkou reservoir; 2) both SSP370 and SSP585 scenarios exhibited elevated ecological risk levels, particularly concentrated in the downstream of Danjiangkou; 3) the high ecological risk area in Hanjiang River basin significantly expanded under the 2042 scenario for SSP370 and SSP585, with an average increase of 14.58% per decade under the SSP370 scenario. The proposed landscape ecological risk prediction approach in consideration of multiple factors serves as a valuable reference for ecological risk assessment in the basin under changing climatic conditions and the formulation of ecological compensation policies.
Hydraulics
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  Wave Prevention and Energy Dissipation Effect of a New Type of Seawall Revetment Structure with Hyperbolic Arc Surface

  ZHOU Ye-kai, QIN Peng, LI Jie-cheng, KUANG Yi, TIAN Lei, WU Shi-qi, XU Xin-yue

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 89-94. https://doi.org/10.11988/ckyyb.20221444

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  Developing new types of seawall revetment holds significant importance in safeguarding lives and enhancing the stability of seawall projects. To address the challenge of ineffective buffering of strong shock waves caused by the swift current in the Qiantang River estuary and the smooth surface of traditional seawalls, we have devised a seawall revetment structure with hyperbolic arc surface. Through indoor hydraulic testing and numerical simulation, we examined the wave dissipation effect and pressure distribution characteristics of the structure. Findings demonstrate that the new seawall revetment structure not only improves energy dissipation by guiding and altering the pattern and direction of impact wave flow, but also enhances the aesthetic appeal of the Qiantang River tide. This approach presents a novel engineering concept for designing seawall revetment structures in complex water flow conditions.
Rock-Soil Engineering
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  Dynamic Response Mechanism of Uniaxial Transient Unloading in Jointed Rock Mass

  LI Xin-ping, WANG Liang-jun, SONG Kai-wen, WANG Shen, HUANG Jun-hong, LIU Ting-ting

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 95-103. https://doi.org/10.11988/ckyyb.20230793

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  This study aims to examine the mechanical responses and deformation damage mechanisms of deep jointed rock masses during transient unloading. We investigated the mechanical behavior and dynamic responses of these rock masses during transient unloading through theoretical analyses, laboratory experiments, numerical simulations, and other methods. Our research identifies several key factors influencing the dynamic response to transient unloading in jointed rock formations. We develop a numerical model that describes in-situ field conditions closely. Initial findings reveal that in the first stage of uniaxial transient unloading, the rock mass experiences no tensile stress. However, in the subsequent second stage, the reflection of tensile stress waves transforms all kinetic energy into elastic potential, creating tensile stresses within the rock mass. Additionally, the unloading process generates transreflectance at rock joints, leading to an inverse relationship between joint opening and stiffness in the presence of joints. In the second stage of uniaxial transient unloading, significant joint opening occurs, causing a sudden displacement in the rock mass as the reflected tensile stress wave reaches the joint. This research enhances our understanding of the mechanical behavior of rock masses under uniaxial transient unloading, providing valuable insights for addressing transient unloading challenges in deep rock mass excavations.
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  Unconfined Compression Strength and Constitutive Model of Palm Fiber Reinforced Clay

  HU Qi-zhi, HU Jian-wen, MA Qiang, TAO Gao-liang

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 104-110. https://doi.org/10.11988/ckyyb.20221572

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  Palm trees are extensively cultivated in southern China, and the palm fibers extracted from the tree bark boast notable tensile strength and durability. Consequently, palm fibers have gradually found application in geotechnical engineering in recent years to reinforce clay. To investigate its mechanical properties, damage patterns, and underlying constitutive relationships under stress, fibers measuring 6 mm, 12 mm, and 18 mm in length were chosen and incorporated into clay at mass ratios of 0.2%, 0.4%, 0.6%, and 0.8%,respectively.Unconfined compressive strength tests on the palm fiber-reinforced clay revealed a significant increase in clay strength following the addition of palm fibers.Optimal reinforcement was achieved by mixing 12 mm palm fibers into the clay at a 0.8% ratio, resulting in a 27% increase in strength compared to regular clay. Furthermore, the reinforced clay demonstrated exceptional damage tolerance and residual strength, prolonging the damage process. This was attributed to the formation of a three-dimensional soil network within the clay, which restricted soil particle slippage and enhanced clay integrity, ultimately leading to improved ductility. Furthermore, the uniaxial compressive stress-strain model for concrete was introduced to analyze the unconfined compressive strength test data. The results revealed a high degree of consistency between model results and test data. These research outcomes offer valuable insights for the utilization of palm fiber-reinforced clay in geotechnical engineering.
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  Experimental Study on Combined Xanthan Gum and Fly Ash Treatment on Acid-contaminated Soils

  NI Jing, HAN Xiao-ting, HE Qing-qing, GENG Xue-yu

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 111-118. https://doi.org/10.11988/ckyyb.20221529

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  Applying eco-friendly xanthan gum biopolymer (XG) in geotechnical engineering significantly enhances soil strength and boosts resistance against erosion from wind and water. The presence of pyruvate groups and glycosidic bonds in XG molecules leads to hydrolysis under acidic conditions, reducing the viscosity of XG hydrogels that bind soil particles. This study explores the effectiveness of using a combination of alkaline fly ash (FA) and XG to treat acid-contaminated soils through Atterberg limits, compaction, and unconfined compressive strength tests. The results demonstrate that FA contributes to increased plasticity limit, optimum moisture content, and maximum dry density, significantly enhancing the soil reinforcement capability of XG in acidic environments. The strength of acid-contaminated soils treated with this combined approach surpasses that of uncontaminated soils treated with the same approach. Moreover, FA mitigates the acidic soil conditions, preventing XG hydrolysis and enhancing soil treatment efficiency. Our findings recommend using a mixture of FA (9%) and XG (3%) for treating acid-contaminated soils, achieving a 310% strength increase compared to untreated soils. For uncontaminated soils, using XG alone (4%) results in a 90% strength improvement over untreated soils.
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  Wetting Deformation Characteristics of Rockfill under High Stress State

  ZUO Yong-zhen, ZHANG Gui-ke, SUN Xiang-jun, PAN Jia-jun, ZHOU Yue-feng

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 119-123. https://doi.org/10.11988/ckyyb.20221568

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  Rockfill serves as the primary filling material in earth rock dams. Its wetting deformation characteristics have a significant influence on dam deformation during impoundment. Employing the single line method, we conducted extensive indoor triaxial wetting deformation tests under confining pressures of 0.5, 1.0, 2.0, and 3.0 MPa on two types of rockfill materials sourced from Lianghekou Hydropower Station. Results indicate a substantial increase in both axial and volumetric wetting deformations as stress levels and confining pressures escalate. This behavior aligns with wetting deformation patterns observed under medium and low confining pressures. Notably, under high isotropic confining pressure, volumetric wetting strain correlates linearly with confining pressure in double logarithmic coordinates, whereas axial wetting strain and confining pressure no longer meet a linear relationship. Moreover, at high unsymmetrical confining pressures, the ratio of volumetric wetting strain to axial wetting strain typically ranges from 0 to 2, exhibiting a nearly horizontal trend with increasing confining pressure. The six-parameter wetting model remains adept at accurately characterizing the axial and volumetric wetting deformation behaviors under varying stress levels and confining pressures.
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  Microscopic Pore Structure Characteristics and Hydraulic Tortuosity of Unsaturated Remodeled Weakly Expansive Soil

  LIN Wen-bo, NING Gui-xia, MA Li-na, DING Xiao-gang, ZHANG Yang, LUO Wei

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 124-130. https://doi.org/10.11988/ckyyb.20221440

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  To investigate the variation in pore distribution of remodeled weakly expansive soil at different dry densities, specimens with dry densities of 1.40, 1.50, 1.60, 1.70, 1.80 g/cm³ were prepared using a press sample machine. The pore structure and distribution characteristics of these specimens were analyzed through mercury-injection and saturation-permeability tests. The hydraulic tortuosity of the specimens were calculated based on mercury piezometric and saturation permeability tests. The results indicate a consistent pattern in the process of mercury entering and exiting specimens of varying dry densities. Due to distinct entry and exit paths and the presence of bottleneck pores, the mercury retains within the specimens. Furthermore, an increase in dry density results in a reduction in both pore volume and the quantity of large pores. The soil's pore structure becomes more intricate with higher dry densities, exhibiting a negative correlation between average pore diameter, porosity, total pore volume, and fractal dimension. Based on the experimental outcomes, saturated permeability coefficients and hydraulic tortuosity at varied dry densities were computed, revealing that the increase in hydraulic tortuosity with higher dry density lies in the changes in pore size and structure, consequently affecting the fluid's permeation ability within the soil.
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  A GeoPIV-RG-Based Method for Fine Measurement of Soil Deformation during Triaxial Test

  LI Lin, CHEN Zhen-wang, CAI Yang, HU Xiao-die

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 131-139. https://doi.org/10.11988/ckyyb.20221456

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  Triaxial test is widely utilized for characterizing soil mechanical behavior, during which soil volume and deformation is required to be measured. This paper introduces a real-time and precise measurement method for soil volume and deformation during triaxial testing, achieved through a GeoPIV-RG based approach using multi-media photogrammetry. This measurement process encompasses system setup, image capturing, multi-camera photogrammetric analysis, GeoPIV-RG-based 2D point cloud generation, 3D point cloud generation, point cloud stitching, end cut, mesh generation, and interpolation, followed by displacement and strain field calculation. To validate the accuracy and feasibility of this method, triaxial tests were conducted on steel cylinder and silt specimens. Test on steel cylinder confirmed that the proposed method accomplished soil volume measurement with an error of only 0.36%, while triaxial test on silt specimen demonstrated the method's capability in real-time and high-resolution full-field measurement of soil deformation. GeoPIV-RG enables the efficient extraction of point clouds on specimen surfaces and overcomes the limitations of the multi-media photogrammetric method. Moreover, the multi-media photogrammetric method broadens the application of GeoPIV-RG from two-dimensional and single-medium conditions to three-dimensional and multi-media settings. Overall, the proposed method presents an efficient and reliable solution for measuring soil deformation during triaxial testing.
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  Preliminary Determination of HDPE Geomembrane Thickness Using Simplified Curve Intersection Method

  XUE Xia, WANG Wan-sheng, LI Wang-lin, WANG Bo-lei, LU Yue

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 140-148. https://doi.org/10.11988/ckyyb.20221361

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  Some inconveniences arise in determining the thickness of geomembrane in plain reservoir basins using the curve intersection method. Such inconveniences include the difficulty in obtaining material's characteristic curves, the need for multiple readings of figures and curves, repeated tension tests, and limited selectivity. To address these challenges, we present a simplified curve intersection method (comprising a simplified linear elastic method and a simplified hyperbolic method) for determining the thickness of HDPE geomembrane based on the fundamental principle of the curve intersection method and the linear elastic and hyperbolic stress-strain constitutive relationships observed during the elastic stage of materials. As a case study, we calculated the thickness of HDPE geomembrane in a plain reservoir in Xinjiang using the proposed method. The results indicated the following: 1) compared to the curve intersection method, the proposed simplified curve intersection method demonstrated a slight calculation error. The average error of the safety factor of tensile stress was approximately 2.22%, while that of strain safety factor was around -4.24%. These findings suggest that the proposed method is reasonably accurate. 2) In identical conditions, square pores exhibited the lowest safety factor of tensile stress, which can be taken as the criterion for determining the safe operation of projects. 3) Under the same pore conditions, the safety factor increased approximately linearly with the thickness of geomembrane. 4) The calculated thickness range of HDPE geomembrane satisfying the safety factor requirements was not less than 0.5 mm. The simplified curve intersection method enables convenient calculation of geomembrane thickness, meeting the demands of determining HDPE geomembrane thickness during the engineering design phase.
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  Stability of Tunnel Anchorage of Long-span Suspension Bridge in Fractured Rock Interlayer

  ZHANG Jian, MA Jian-lin, WANG Qin-ke, SU Wei

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 149-156. https://doi.org/10.11988/ckyyb.20221391

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  The stability of tunnel anchorage is a crucial factor in ensuring the safe operation of suspension bridges, as it forms an integral component of the structure. To investigate the load response behavior of tunnel anchorage in fractured rock interlayers of long-span suspension bridges, we have developed a three-dimensional numerical model. This model allows for a comprehensive evaluation of the stability of the tunnel anchorage, demonstrating its suitability and safety within fractured rock interlayers. Our findings highlight the significant impact of fractured rock interlayers on the deformation of tunnel anchorage. Specifically, the displacement distribution curve of the rear anchor face and surrounding rock exhibits a distinct hump shape, with greater displacement on the left while smaller displacement on the right. Additionally, the interface friction resistance of the anchorage experiences abrupt changes within the fractured rock interlayer region. The failure of the anchorage-rock system commences from the vault area within the fractured rock interlayer, gradually propagating towards the arch waist and bottom until the plastic zone of the anchorage-rock interface is connected. Shear failure in the contact zone between anchorage and rock characterizes the failure mode. The bearing capacity of the tunnel anchorage is governed by the tensile failure of the steel bundles, with the comprehensive ultimate bearing capacity reaching 2.3 times the designed main cable force. Overall, the tunnel anchorage demonstrates favorable stability and applicability within fractured rock interlayers.
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  Impact of Deep Foundation Pit Excavation for Luoyang Longmen Comprehensive Transportation Hub on Adjacent Pipelines

  GAO Lin-jing, DAI Jun-de, XU Ze-yong, ZHANG Jie, LIANG Bin

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 157-165. https://doi.org/10.11988/ckyyb.20221382

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  Taking the Longmen Comprehensive Transportation Hub Project in Luoyang as an engineering background,we employed the Midas-GTS/NX finite element software in association with on-site monitoring data to investigate the impact of foundation pit construction on pipeline deformation. We considered various factors of pipeline such as buried depth,buried distance,pipe diameter,pipe material,and the position of internal support. By normalizing variables, we evaluated the influence of these factors on pipeline behavior during foundation pit construction and assessed the safety performance of thermal pipelines. The outcomes reveal that,under the pit angle effect,the deformations at both pit corners are essentially consistent,with vertical displacement,horizontal displacement and bending moment in the middle of the pipeline reaching 1.36 times,1.14 times,and 1.19 times that of the pit corners respectively. Furthermore,the maximum displacement of the pipeline occurs in its middle part under diverse influencing factors. Through variable normalization,we identified that vertical displacement and horizontal displacement of pipeline exhibits the highest sensitivity to buried distance,with relative sensitivities of 0.78 and 0.60,respectively,and conversely,the lowest sensitivity to pipe diameter,with sensitivity values of only 0.12 and 0.08. Evaluation of the safety performance of thermal pipeline reveal that the maximum relative rotation angle remains below 0.1° and the stress safety coefficient reaches 10.52, indicating a satisfactory level of safety.
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  Acoustic Emission Evolution Law and Failure Precursory Characteristics of Oil Shale under Uniaxial Compression

  GUO Peng-fei, QIU Yang, DENG Shi-wei, ZHU Xing-yu, WANG Yuan-yuan

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 166-173. https://doi.org/10.11988/ckyyb.20221457

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  To obtain effective precursory characteristics of the failure of oil shale under load, we conducted uniaxial compression acoustic emission (AE) tests on oil shale using a TP coupled gas escape test system. We collected AE signals throughout the entire failure process of rock samples and analyzed the evolution of AE during deformation and failure. Employing the critical slowing down principle, we conducted an in-depth analysis of AE characteristics' variance and autocorrelation coefficient during the loading failure process of rock samples. Test results revealed significant AE phenomena throughout the testing process, with the changes in AE characteristic parameters (energy count, ring count, radiation value) correlating well with rock deformation and failure. Analysis of acoustic emission characteristics RA (rise time/peak amplitude) and AF (average frequency) indicated that the early stages of the test primarily exhibited tensile fracture, transitioning to increased shear fracture in later stages. Near peak intensity, AE characteristic parameters exhibited rapid increases, manifesting a clear critical slowing phenomenon. The sudden rise in variance and autocorrelation coefficient serves as a precursor to rock failure, with variance providing more accessible and reliable precursor information compared to the autocorrelation coefficient. By combining the b value of acoustic emission with variance of AE characteristic parameters, we effectively eliminated false signals generated during testing. The drop point of the b value in the rapid rise stage of variance slope was identified as the precursor feature point of rock failure.
Engineering Safety And Disaster Prevention
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  Discussion on Key Technologies for Grouting Design and Construction of Earth-Rock Dams

  SHI Hua-tang, JI Yang, XIAO Bi, ZHONG Kun

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 174-180. https://doi.org/10.11988/ckyyb.20230883

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  The grouting process for the foundation of earth-rock dams, including core wall rockfill dams and panel rockfill dams, is influenced by various factors such as limited cover depth, blasting operations, unloading processes, and the presence of weak rock formations. These factors often lead to challenges such as significant uplift, fracturing, and seepage during grouting operations, posing difficulties in achieving effective injection and ensuring quality, consequently jeopardizing the reservoir's normal water storage. We analyzed the key design issues such as the selection of foundation rock mass, layout of grouting corridors, arrangement of grouting holes, determination of grouting and inspection pressures. Furthermore, on the basis of specifications and engineering practice, we discussed the grouting methodologies, methods for managing external seepage, selection of blocking devices, control of uplift, and pressure augmentation strategies. Finally, we propose the method of determining curtain grouting pressure and inspection pressure, the systematic sealing and ramdom sealing for leakage, the criteria for selecting blocking devices, and the grouting control based on P-Q relation to offer reference for similar dam foundation grouting.
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  Causes of Accumulated Air and Tailwater Malfunctions in Rubber Dam and Design of a Pumping and Drainage System

  WANG Xing-chao

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 181-186. https://doi.org/10.11988/ckyyb.20230124

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  In water-filled rubber dams, air often accumulates at the top of the dam bag following water filling, which is challenging to completely remove. Similarly, when the rubber dam collapses and discharges water, residual tailwater frequently remains at the bottom of the dam bag, resisting complete discharge. To tackle these common problems, a system for efficiently pumping and discharging accumulated air and tailwater in rubber dams has been developed. Based on an analysis of the underlying causes and potential consequences of these problems, this paper introduces conceptual design principles and methodologies for the pumping and discharging pipeline, power device, and control system. Through verification via typical application examples, it has been demonstrated that this system effectively mitigates faults caused by accumulated air and tailwater along with associated challenges, and also ensures the rubber dam impounds at maximum water level and discharges at maximum discharge section. This innovation offers valuable insights for the meticulous design of rubber dam projects and the enhancement of traditional design approaches.
Hydraulic Structure And Material
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  Influence of Basalt-Polyvinyl Alcohol Fiber on Frost Resistance of Recycled Concrete

  SI Zheng, TIAN Shuang, HUANGFU Bing-hui, HUANG Ling-zhi, DU Xiao-qi, ZHANG Fei-yue

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 187-193. https://doi.org/10.11988/ckyyb.20221566

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  To enhance the utilization of recycled aggregate concrete (RAC) in high-altitude and cold regions of northern China, we investigated three anti-freezing performance indicators, namely, mass loss rate (MLR), relative dynamic elastic modulus (RDEM), and compressive strength loss rate (CSLR) of RAC reinforced with single and combined basalt fiber (BF) and polyvinyl alcohol fiber (PVAF). Scanning electron microscopy (SEM) was employed to analyze the meso-mechanical behavior of the mixed-fiber recycled concrete following 200 freeze-thaw cycles. Subsequently, the optimal mixed fiber content was determined using the response surface method. Findings indicate that fiber additives enhance the frost resistance of recycled concrete, with the combined fiber exhibiting superior performance compared to single fiber. Both BF and PVAF are intricately interwoven within the specimen's network, synergistically reinforcing the structure while mitigating crack formation. Optimization analysis reveals that the optimal volume content of PVAF and BF is 0.170% and 0.246%, respectively, yielding the highest frost resistance in recycled concrete. These results offer valuable insights for the design of basalt-polyvinyl alcohol fiber content in recycled concrete applications.
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  Modeling the Relationship between Compressive Strength and Pore Distribution Characteristics of Medium-to-High Strength Concrete

  YANG Shuai, MAO Hai-tao, LIU Chang, WANG Xiao-ju

  Journal of Changjiang River Scientific Research Institute. 2024, 41(4): 194-202. https://doi.org/10.11988/ckyyb.20221442

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  To investigate the quantitative relationship between pore distribution characteristics and the compressive strength of medium-to-high strength concrete, we conducted comprehensive compressive strength tests by using a low-field nuclear magnetic resonance (NMR) imaging analysis system in conjunction with a fully automatic pressure testing machine. By validating and modifying the Ryshkewitch semi-empirical equation model, we established the quantitative relationship model between pore distribution characteristics and compressive strength. Test results demonstrate several key findings. First, an increase in sand rate and initial entrapped air content of concrete leads to a gradual increase in porosity. Increasing the initial air content proves to be more effective in generating a more variable porosity compared to increasing the sand rate. Specifically, by increasing the sand rate, the percentage of non-capillary pores increases by 17.2% while the percentage of capillary pores decreases by 13.0%. On the other hand, increasing the initial air content results in a 12.7% increase in capillary pores and a 12.6% decrease in gel pores. By employing the model based on modified Ryshkewitch semi-empirical equation, we achieved accurate results with an R² value close to 1 and a P-value less than 0.05, effectively describing the quantitative relationship between pore distribution characteristics and compressive strength.