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01 August 2023, Volume 40 Issue 8
    

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  • Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 0-0.
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  • River-Lake Protection and Regulation
  • CHEN Dong, LI Ling-yun, GUO Xiao-hu
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 1-9. https://doi.org/10.11988/ckyyb.20220680
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    Sediment carrying capacity (SCC) is a crucial factor in the study of suspended sediment transport and channel evolution in the downstream of reservoirs. This study focuses on the river reach from Shashi to Hankou in the midstream of Yangtze River. By introducing two concepts in the non-equilibrium suspended sediment transport theory proposed by Han Qiwei, namely, the percentage of flow discharge which changes bed load into suspended load, and the particle gradations of sediments carried in flows, we examined the changes, and factors affecting the changes in the non-uniform suspended sediment carrying capacity after the construction of the Three Gorges Dam (TGD). Following the completion of TGD, Shashi and Jianli stations witnessed a significant increase in the percentage of flow discharge under various discharge levels. Specifically, when the discharge exceeded 30 000 m3/s at Luoshan station and 35 000 m3/s at Hankou station, the percentage of flow discharge increased. Shashi-Chenglingji reach experienced a more pronounced decrease in sediment carrying capacity than Chenglingji-Hankou reach. Moreover, the carrying capacity for sediment particles smaller than 0.125 mm declined significantly in Shashi-Chenglingji reach, while particles smaller than 0.25 mm reduced in Chenglingji-Hankou reach. The reduction of sediment carrying capacity in Shashi-Chenglingji reach is primarily attributed to the influence of ω* (which is the average settling velocity of sediments), while in Chenglingji-Hankou reach, it is jointly affected by U3/h (a factor of SCC) and ω*. Notably, U3/h plays a more prominent role when the critical discharge at Luoshan and Hankou does not exceed 30 000 m3/s and 35 000 m3/s, respectively.
  • FENG Xian-dao, HAN Peng-peng, QIU Zheng-zhong, WANG Cong
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 10-15. https://doi.org/10.11988/ckyyb.20220383
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    Following the construction of immersed tube base groove in inland river, the flow of water through the groove leads to the deposition of silt within it. To obtain the distribution of silting thickness in tube base groove, this paper focuses on the Xiangyang immersed tube tunnel project. By combining observation with numerical simulation, we obtain the silting thickness of the base groove at different positions, and examine the influence of sediment concentration in the river on the silting thickness in tube base groove. Results demonstrate that sediment concentration in the direction vertical to the groove increases as the water depth increases. As water flows through the groove, the reduced flow velocity results in a decreased sediment carrying capacity. Consequently, the silting is mainly concentrated in the front slope and the base groove, whereas the thickness of silting is minimal in the back slope of the groove. After the installation of immersed tube, the flow area of the groove decreases, leading to a larger silting thickness at the bottom of the immersed tube compared to the top.
  • ZHANG Xiao-ya, REN Chun-ping, YANG Fan
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 16-23. https://doi.org/10.11988/ckyyb.20220501
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    Building continuous hydraulic lifting dams in small and medium-sized rivers will affect the hydrodynamics and sediment erosion and deposition process of the river. The variation characteristics of river erosion and deposition resulting from different combined operation schemes of hydraulic lifting dams also differ. To address this issue, four typical flood processes were selected for a 2D numerical simulation of water and sediment dynamics in Fenhe River (Erba-Yitang segment) using Delft3D FM model. Under the four operation schemes of hydraulic lifting dam group, the influence of hydraulic lifting dam group on the variation characteristics of erosion and deposition of river channel was analyzed. The findings provide valuable insights for the scheduling of hydraulic lifting dam groups in the midstream of Fenhe River. Results reveal that, under the schemes 1-4 in four flood scenarios, the water depth in front of dam 14# ranges from approximately 0.5 to 1.4 m, 1.3 to 2.8 m, 0.6 to 1.8 m, and 0.5 to 1.6 m, respectively, at the end of the simulation period. The maximum local velocity behind the dam is approximately 1.5-2.5 m/s, 2.0-6.0 m/s, 2.0-3.0 m/s, and 2.0-2.5 m/s, respectively. The range of erosion and deposition is approximately -0.5 to 1.4 m, -0.3 to 1.9 m, -0.5 to 1.6 m, and -0.5 to 1.5 m, respectively. The total amount of sediment deposition in the river reaches approximately 4.9×104 to 242.3×104 m3, 5.3×104 to 323.5×104 m3, 5.0×104 to 252.5×104 m3, and 4.95×104 to 245.1×104 m3, respectively. The conclusions are as follows: hydraulic lifting dams exhibit the greatest influence on the hydrodynamic field and the change in bed elevation when operating at full capacity. Moreover, the sediment deposition volumes of hydraulic lifting dams are approximately 1.08 to 1.36 times that of non-dam operation under the four flood scenarios.
  • Water Resources
  • LI Hong-gang, ZHANG Pan-quan, GUAN Zhen
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 24-29. https://doi.org/10.11988/ckyyb.20220548
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    As the most important transnational water system in Asia, the Lancang River plays a crucial role as part of the “Asian Water Tower”. Analyzing the evolutionary patterns and trends of upstream river runoff in the Lancang River has significant strategic implications for water resource utilization and regional green energy development. The present study focuses on the runoff characteristics and their evolution in the upstream of Lancang River over the past 30 years based on data from the Wunonglong section, as well as air temperature and precipitation records. Methodologies including linear regression analysis, the Mann-Kendall trend test, and Pearson correlation coefficient were employed for data analysis. The findings reveal that, over the decades since the availability of discharge data, the upstream runoff in the Lancang River has exhibited little change at the decadal scale. However, on a seasonal basis, there is a tendency of increased runoff in winter and decreased runoff in summer. Notably, a distinct shift occurred in August in the early 1970s, with a prominent decreasing trend of 4.8% per decade, approximately equivalent to a total volume reduction of 200 million cubic meters per decade. Moreover, this decreasing trend has been further accelerating in the past 30 years, consistent with the decreasing trend of precipitation in the middle region of the upstream area. The study also reveals that, over the past three decades, as spring temperatures have risen, the response of upstream runoff to temperature in May has weakened, while the relationship between temperature in April and runoff has become more pronounced. Given the background of global warming, the advancing snowmelt period in the upstream area of the Lancang River requires high attention and proactive measures.
  • WANG Dong, XIE Shuai, XU Ji-jun, WANG Yong-qiang
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 30-38. https://doi.org/10.11988/ckyyb.20221509
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    The construction and operation of the Three Gorges Project (TGP) have significantly altered the hydrological regime of the middle and lower reaches of the Yangtze River, thereby impacting irrigation water supply. This study focuses on analyzing the effects of TGP operation on the safety of irrigation water supply in the Poyang Lake areas, specifically considering water quantity and fulfillment of water supply. To achieve this, the evolution of water resources and the situation of water supply before and after TGP operation were investigated. Following the operation of TGP, the Poyang Lake witnessed a decreasing trend in available water supply, with the most significant reductions occurring in September and October during impoundment periods. Moreover, the overall water level in the lake area has dropped by 1.1-2.5 meters. Although the total water quantity can still meet irrigation and water supply demands, there is a noticeable decline in the fulfillment of both irrigation and water supply requirements in urban and rural regions, leading to a significant increase in total water shortage. The fulfillment of secured rural and urban water supply and irrigation water supply requirements has dropped from 99.1% and 83.6% before TGP operation to 87.5% and 42.7% after operation, respectively. Simultaneously, water shortage for rural and urban water supply and irrigation water supply has increased from 0.78 and 70.32 to 93.85 and 186.11 million cubic meters, respectively. However, it is worth mentioning that early or delayed impoundment of TGP can slightly mitigate the project’s influence on water supply and irrigation during impoundment, thereby increasing the water supply capacity by 0.2% and 0.3% respectively.
  • WANG Jia-hong, WANG Zi-wei, QIN Xin, LAI Hong, LUO Han-min, LU Ying
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 39-43. https://doi.org/10.11988/ckyyb.20220294
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    The water temperature of rivers, lakes, reservoirs, and other inland water bodies plays a crucial role in the growth of aquatic organisms and the surrounding ecological environment. The development of a water temperature observation system serves as the basis for theoretical research and engineering applications. Current surface water temperature measurement in inland waters mainly relies on manual visual observation using thermometers or automatic observation with hydrological station instruments. However, these methods have limitations such as equipment operation and maintenance difficulties, as well as discontinuous monitoring data when applied in high-frequency or non-fixed hydrological observations. To improve the stability and reliability of water temperature measurement and reduce the adverse effect of water level fluctuation on automatic observation, this paper presents the design and implementation of a novel infrared water temperature observation system. A comprehensive series of comparison tests and numerical corrections were conducted to validate the performance of the proposed method. The results of prototype observation demonstrate that over 85% of the relative errors of the corrected infrared water temperature are below 5%, and more than 80% of the absolute temperature differences are less than 1 ℃. In conclusion, the infrared water temperature measurement system demonstrates stable performance and high reliability. It proves to be an effective method for observing the surface water temperature of inland water bodies.
  • ZHENG Rong-wei, ZHANG Yue, WANG Qing-ming, GUI Yun-peng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 44-50. https://doi.org/10.11988/ckyyb.20220174
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    Potential evapotranspiration (ET0 ) is a critical element that impacts the water cycle of a river basin. Understanding the characteristics of future changes in ET0 and the quantitative impact of its driving factors is of great significance for coping with the variation of water cycle under future climate changes. Using the Peman-Monteith formula and ensemble data from five climate models, we estimated the temporal and spatial trends of China’s potential evapotranspiration from 2030 to 2060, and applied partial differential methods to quantify the contributions of various factors driving ET0 changes. The findings reveal that under the RCP4.5 and RCP8.5 scenarios, the ET0 of five major climate zones in China will exhibit an increasing trend in the future, with rates of increase reaching 1.32 mm/a and 1.96 mm/a, respectively. The fastest growth rate of ET0 is observed in the subtropical climate zone, while in the plateau mountain climate zone, the growth rate is the smallest. The growth rate of ET0 in the five climate zones under the RCP8.5 scenario is greater than that under the RCP4.5 scenario. Overall, ET0 exhibits an increasing trend in all four seasons of the year. Under the RCP4.5 scenario, the ET0 growth rate is the greatest in autumn (0.56 mm/a), while under the RCP8.5 scenario, the largest growth rate is observed in summer (0.63 mm/a). Future changes in ET0 are primarily affected by daily maximum and minimum temperatures, as well as actual water vapor pressure. Daily maximum temperature is the dominant meteorological element governing the magnitude of ET0 changes, followed by actual water vapor pressure. Similar patterns were found in the analysis of the driving factors of ET0 changes in all four seasons. The research findiugs provide reference for optimal allocation of water resources and agricultural irragation management in future.
  • Water Environment and Water Ecology
  • WANG Zhen-hua, LI Qing-yun, LONG Meng, HU Yan-ping, HAO Yue
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 51-56. https://doi.org/10.11988/ckyyb.20220278
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    Based on extensive field investigations and a comprehensive analysis of existing literature, we aim to elucidate the distinctive characteristics and identify the primary sources of pollution in small reservoirs across China. Moreover, we examine the factors contributing to the deterioration of water quality and proposes an integrated approach to pollution control and ecosystem restoration, encompassing a framework of “comprehensive pollution control - systematic restoration - integrated management and protection”. To tackle the diverse pollution sources, including fertilizer aquaculture, non-point source runoff, sediment, and water pollution stock, a principle of classified and targeted application is advocated. Furthermore, considering the unique pollution patterns observed in the riparian zones, front dam areas, tributaries, and bay areas, we discuss precise pollution control measures aimed at specific partitions. We also recommend to implement aquatic bioremediation regulations and comprehensive management strategies based upon pollution source interception and load reduction. The findings of this study establish a solid theoretical foundation to maintain the long-term water quality of small reservoirs and support the sustainable water supply management in rural regions.
  • GUO Li-jin, XU Rui-wei
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 57-63. https://doi.org/10.11988/ckyyb.20220242
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    Real-time variations in water quality environment and the internal coupling pose challenges to predicting water quality efficiently and accurately. To extract further information from the time series data and enhance the accuracy of prediction models, we propose a novel combined prediction model for Dissolved Oxygen (DO). To begin with, the water quality data is decomposed using the Seasonal and Trend decomposition using LOESS (STL) technique. Subsequently, the obtained seasonal component, trend component, and residual component are fed into the Long Short-Term Memory network model (LSTM) for prediction. In order to address the impact of LSTM network initialization parameters on prediction performance, we introduce an optimization approach based on the Fruit fly algorithm utilizing Gaussian function. Finally, the predicted values of each component are reconstructed to the DO prediction values. To validate the effectiveness of the proposed model, we conduct simulation tests utilizing water quality data from three sections of Haihe River. Results demonstrate that the combined model exhibits a favorable prediction effect on the DO concentration of the three stations, characterized by minimal errors and strong generalizability.
  • Soil and Water Conservation and Ecological Restoration
  • ZHANG Zhi-hua, YANG Jing, WANG Qian, HUANG Jin-quan, DENG Ling-min, XU Wen-sheng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 64-69. https://doi.org/10.11988/ckyyb.20220878
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    Ecological sandless concrete has been widely used in artificial ecological river bank protection project due to its exceptional properties, such as robust water and air permeability, as well as its ability to connect the water and land ecosystems. Ecological sandless concrete should not only meet the stability requirements of river bank slope, but also have the capacity to withstand erosion for vegetation growth. This study aims to elucidate the mechanism and effectiveness of backwater and flow velocity reduction offered by plants on ecological sandless concrete banks. To achieve this objective, a series of indoor scouring experiments were conducted under controlled varying flow velocities. The impact of different plant species growing on the ecological sandless concrete bank on water levels and flow velocities was examined. The findings demonstrate that cynodon dactylon exhibits superior backwater effects compared to manila grass, primarily due to its greater height and reduced susceptibility to falling. Conversely, manila grass demonstrates better performance in mitigating water velocity than cynodon dactylon, owing to the influence of plant density on the intensity of flow turbulence. Moreover, the reduction in velocity was more evident in sections closer to the plant layer, with a maximum reduction rate of 75.24%. Notably, both manila grass and cynodon dactylon were capable of withstanding water flow velocity of 5 m/s. This study provides valuable insights for enhancing construction techniques and selecting suitable plant species when utilizing ecological sandless concrete for riverbank slope stabilization.
  • WANG Yu, YE Chang-qing, ZHU Li-rong, LI Ang, LIANG Xu, ZOU Yi
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 70-76. https://doi.org/10.11988/ckyyb.20220950
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    Quantitative assessment of the impact of land use change on ecosystem services is currently a challenging and highly debated research topic. In this study, an InVEST model was developed to examine the spatial-temporal characteristics of land use change and its effects on ecosystem services in the Dongzhai Bay Area from 1990 to 2018. The findings revealed the following trends: 1) Significant changes occurred in land use within the bay area from 1990 to 2018. Specifically, the area occupied by grassland, cropland, and woodland decreased by 17%, 5%, and 9%, respectively, while construction land and water area increased by 179% and 59%, respectively. 2) Over the same period, the annual water service function exhibited enhancement, with total water yield of 14.01×108, 22.17×108, 27.01×108, and 16.42×108 m3 in 1990, 2000, 2010, and 2018 respectively. Moreover, the water yield service function showed an intensifying pattern in the north region but a weakening pattern in the east-central region. The water purification function demonstrated a decrease in total nitrogen levels and an increase in total phosphorus levels. Specifically, the total nitrogen output was 587.8, 589.3, 590.2, and 591.9 t, while the total phosphorus output was 51.78, 51.54, 50.32, and 50.04 t. A clear spatial attenuation of water purification function was observed in the north region. The overall habitat quality function experienced a decline, particularly in the north, with slight declines observed in the west and northwest. 3) The expansion of construction land and decrease of forest land in the north and west regions will enhance the water yield function, but weaken the water purification and habitat quality service function. To maintain the terrestrial ecosystem services in the bay area, attentions should be given to optimizing the land use pattern and controlling the expansion of construction land in the northern coastal areas, with a focus on forest protection.
  • WANG Xiao-feng, YANG Guang-bin
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 77-83. https://doi.org/10.11988/ckyyb.20220173
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    By quantifying the effectiveness of the comprehensive rock desertification control project in karst areas since its initiation in 2008, we aim to provide insights for future control efforts. Based on data of rocky desertification in the Beipanjiang River Basin in Guizhou Province in 2010 and 2019, we employ methods of transition matrix and overlay analysis to examine the characteristics of rocky desertification changes and the effectiveness of governance in the basin. Results indicate that 1) rocky desertification in the basin is mainly mild to moderate, and exhibits a spatial pattern characterized by heavy distribution in the north, middle, and east, light in the west, and less in the southeast. 2) From 2010 to 2019, the area of rocky desertification decreased by 1 071.89 km2, and the proportion of karst area decreased from 41.14% to 33.20%. Moreover, the moderate and severe rocky desertification areas significantly reduced, with conspicuous reductions observed in the north and east parts of the region. The stable type was predominantly featured in chemical change, followed by the improvement type, while the degradation type’s area was smaller, with scattered distribution. 3) With respect to slope, rocky desertification is most concentrated in the range of 5°-25°, and the reduction is the most significant in the 25°-45° range. With respect to elevation, the area of moderate, severe, and extremely severe rocky desertification decreased for all elevation gradients. During the study period, vegetation restoration was the principal method used to control rocky desertification, with multiple control modes coexisting.
  • Hydraulics
  • PAN Yun-wen, LIU Xin, YANG Ke-jun
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 84-91. https://doi.org/10.11988/ckyyb.20220353
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    To investigate the flow characteristics in meandering channels under backwater conditions caused by overflow dams, a meandering channel model with an overflow dam at its outlet is designed and constructed. Velocity and water level data in thirteen cross sections are measured using an Acoustic Doppler Velocimeter (ADV) and a digital water level altimeter. The experimental results demonstrate that the absolute transverse water surface gradients in curved segments decrease as the relative dam height increases. The longitudinal water surface gradients between a bending apex and the inlet of the downstream adjacent crossover area exhibit positive values, while the longitudinal water surface gradients between the inlet of a crossover area and the downstream adjacent bending apex display negative values. Nevertheless, the magnitudes of these gradients diminish with the increasing relative dam height. Moreover, secondary flow vortex blobs are observed in the crossover areas of the meandering channel, rotating in the same direction as those in the upstream adjacent curved segment. With an increase in relative dam height, the depth-averaged longitudinal velocities along the meandering channel decrease to varying extents. Likewise, the maximum turbulent kinetic energy in any cross section decreases as the relative dam height increases. Regarding the distribution of turbulent kinetic energy, the longitudinal velocity fluctuation contributes the most, followed by the transverse velocity fluctuation, while the vertical velocity fluctuation contributes the least. The Reynolds stress (Ruv) can be used as an approximate indicator of the directions of cross-sectional transverse flow movements at the inlets and outlets of the crossover areas. If the Reynolds stress value is positive in a specific region, the fluid will flow from left to right; otherwise, the fluid will flow from right to left.
  • YAN Peng-peng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 92-96. https://doi.org/10.11988/ckyyb.20220224
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    This study proposes an adjustment to the design of spillway control section of a water supply dam project in Kenya which is constrained by flood discharge requirements, geological conditions, land use scale, power supply capacity, and dam operation and control. The proposed design scheme changes from a gated wide-crested weir to a labyrinth weir to ensure the flood discharge capacity meets the original design requirements and reduce project costs while minimizing impacts on the dam works. Design parameters such as the height, width, and extended length of labyrinth weir are preliminarily proposed based on engineering experience. Flow-3D software is used to simulate and analyze the spillway discharge conditions, and physical model tests are conducted to verify the design parameters determined from the numerical simulation results. The numerical simulation and physical model test demonstrate that when the water head above the weir is less than the weir height, the comprehensive flow coefficient of the labyrinth weir initially increases and then decreases with increasing water head above the weir. Moreover, no distinct unfavorable flow regime was observed during labyrinth weir discharge, reflecting sound discharge capacity that meets the special requirements of the engineering application.
  • Rock-Soil Engineering
  • LI Yong-jing, WANG Song, YIN Jian-wen, WEN Cheng-zhang, CHENG Yao-hui
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 97-104. https://doi.org/10.11988/ckyyb.20220326
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    The instability and failure of reserved safety rock pillars in tunnels crossing through outburst coal seam faces often lead to coal and gas outbursts. Based on catastrophe theory, we propose an analytical method for assessing the stability of reserved safety rock pillars in such tunnels by using Polynomial distribution functions and dichotomy in a comprehensive manner. By applying the principle of total potential energy, we establish a cusp catastrophe model to represent rock pillar instability, from which a mechanical criterion for rock pillar instability is derived. To further account for the volume catastrophe criterion of the plastic yield zone of surrounding rock, we establish a predictive model for rock pillar stability and obtain a discriminant for assessing rock pillar stability. Engineering examples are employed to verify and analyze the proposed method. Results demonstrate that the stability of reserved safety rock pillars in gas tunnels crossing coal seam is closely correlated with elastic modulus E, thickness L, vertical in-situ stress N, and equivalent height H of tunnel excavation face. The predictive model based on the yield volume catastrophe criterion, as well as the mechanics criterion for stability and instability, exhibits reasonable and feasible outcomes. The discriminant results for rock pillar stability align with the actual on-site conditions, thereby validating the rationality and accuracy of our proposed prediction method and criteria.
  • TONG Li-hong , WU Bing-ni, WU Lin-lin, XU Chang-jie
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 105-111. https://doi.org/10.11988/ckyyb.20220207
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    Defining the damage evolution characteristics of rocks under load is the key to analyze the damage mechanism of rocks. In this paper, a strain-related deformation intrinsic model of sandstone was developed by introducing a strain-related macro-modulus mathematical model. On the basis of the damage mechanics theory, the sandstone damage evolution law was analyzed by using the established intrinsic structure model. Moreover, uniaxial/triaxial compression tests were performed on rocks under different loading rates and surrounding pressure conditions using a rock triaxial loading system to systematically verify the rationality of the sandstone damage evolution model. The initial damage ω0, loading damage ωf and total damage ωt of sandstone were obtained. Results demonstrate that loading rate has a small effect on the evolution of the three types of damage when loading rate is varied in the range of 0.0-0.5 mm/min. When surrounding pressure changes in the range of 0-10 MPa, the initial damage and total damage of the sandstone keep decreasing with the increase of surrounding pressure, while loading damage remains almost constant. The loading damage, as the rock damage threshold, is less influenced by loading rate and surrounding pressure and fluctuates within a certain range, which indicates that the crack expansion within the rock is the causative factor of damage. Finally, a method for estimating the in-situ modulus of rocks is proposed by combining the intrinsic model and damage theory presented in this paper, providing theoretical references for related projects.
  • ZHOU Hua-min, WU Ai-qing, XIAO Guo-qiang, SONG Jun-lei, ZHOU Li-ming, TANG Xin-da
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 112-119. https://doi.org/10.11988/ckyyb.20220375
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    Piping is a most common failure mode in binary structure dikes. Accurate detection of dike piping channels during high water levels is of great significance to the study of piping evolution and risk prevention and reinforcement project. This paper presents a technique for detecting weak magnetic field signals in embankment seepage channels. In the light of the conductivity of seepage water, an artificial electric current is supplied to the outlet of piping channel. By detecting the weak magnetic field signal generated by the conduction loop in the dike surface, the distribution of piping channel can be rapidly identified. The distribution characteristics of weak magnetic field in piping channel are analyzed by numerical calculations. To address the challenge of weak magnetic field signal detection, a method of extracting weak magnetic signal based on phase-locked amplification method and conductor source interference of the same frequency is proposed to reduce the influence of dike undulating terrain and enhance the energy of weak magnetic signal. Field tests of piping detection were carried out on a dike in Poyang Lake basin to find out the distribution of potential piping paths effectively. This study will contribute to improving the accuracy of detecting piping channel in dike, enabling early detection and mitigation of piping hazards, and providing technical support for emergency response of piping incidents.
  • ZHAO Wen-fang, TANG Xiao-wu, GUO Wen-qi, LI Ke-yi, CHEN Shi-hua, LIN Wei-kang
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 120-126. https://doi.org/10.11988/ckyyb.20220232
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    Nonwoven geotextiles used as filters are commonly subjected to laterally constrained tensile loads in practice. A theoretical solution is developed to study the pore size distribution of nonwoven geotextiles under laterally constrained uniaxial tension. The theoretical solution is based on a fiber network model, whereby the probabilistic sieving problem is equivalent to a mass-based probability of retention which is modified from a number-based probability density. Three different needle-punched nonwoven geotextiles are subjected to the uniaxial tensile strains with lateral confinement. The pore sizes of unstrained geotextiles and geotextiles under strains 3%, 5% and 10%, respectively, are obtained from dry sieving test after eliminating electrostatic effects. The experimental results present an accurate prediction of theoretical equations in pore size distribution with laterally constrained uniaxial tensile strain. The pore size distribution curves move towards right with the increase of tensile strain under lateral confinement, which results in the increase in characteristic pore diameters.
  • HU Kun, GAO Zhao-guo, WANG Shao-wei, YANG Zhao, WU Yan
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 127-132. https://doi.org/10.11988/ckyyb.20220313
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    To address the issue of foundation stability in construction engineering in cold regions, an experimental study was conducted to investigate the physical and mechanical properties of a frost susceptible silty clay in freezing process. Parameters such as the critical water content for frost heaving, frost heave forces, and shear strength of warm frozen soils were determined. The results indicate that frost shrinkage occurs when the water content of soil samples is below the critical water content for frost heaving. This phenomenon is attributed to the combined effect of frost shrinkage of the soil skeleton and phase transformation of pore water. The vertical displacement curves of soil samples exhibit three types with varying water content: frost shrinkage, frost shrinkage followed by rebound, and frost shrinkage followed by frost heave. The curve of frost heave forces can be divided into two stages, namely rapid growth and stable growth, due to the development of the temperature field. The frost heave force increases as the freezing temperature decreases. The increase in temperature gradient within the active zone of freezing soils, based on the theory of segregation potential, is the cause of higher frost heave forces. When compared to soil samples at normal temperature, the cohesion of frozen silty clay at -3℃ increased from 7.34 kPa to 29.56 kPa, and the internal friction angle increased from 6.40° to 9.18°. However, the shear stress curves did not exhibit brittle failure of frozen soils, but rather displayed characteristics of strain hardening.
  • SUN Xiang-jun, PAN Jia-jun, LU Yi-wei, ZUO Yong-zhen, ZHOU Yue-feng, WANG Jun-peng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 133-138. https://doi.org/10.11988/ckyyb.20220312
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    Particle gradation and initial dry density are two crucial factors that influence the strength characteristics of coarse-grained soils. In this paper we aim to quantify the relationship between gradation and initial dry density index of coarse-grained soil and its strength index. Based on the formula process of multiple fractal stages, we derived a quantitative expression, termed as the “skeleton particle density index”, which relates the relationship between the number of particles larger than a certain size per unit volume and the multiple fractal dimensions and dry density. Subsequently, we carried out four triaxial consolidation drainage shear tests on coarse-grained soils with various combinations of gradation and density. The destructive shear stress of continuously graded coarse-grained soil exhibited a linear increase with the skeleton particle density index of the skeleton particle density index. Finally, we conducted extensive literature data verification studies to validate our findings. The obtained results not only provide reference for comparing and selecting optimal schemes for coarse-grained material filling but also offer significant insights into the study of the scale effect on the strength of coarse-grained soils.
  • ZHANG Yan, MA Sheng-min, ZHANG Jian-qing, LIU Lin-li
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 139-144. https://doi.org/10.11988/ckyyb.20220398
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    The additive mass method is a crucial detection technique for assessing the rolling quality of rock-fill of dams. The quality of additive mass method’s detection data is directly dependent on the reasonableness of its field test parameters. To determine the optimal test parameters, field tests were conducted in the rock-fill area of the dam of Shuangjiangkou hydropower station. Test parameters, including mass block diameter, offset, and source height, were selected for the field test. Through the analysis and evaluation of the additive mass method data and intermediate results in the data acquisition process, the field optimal test parameters were determined to be a mass block diameter of 50 cm, a source height of 35 cm, and an offset of 25 cm. Consequently, a comprehensive set of field determination method for the test parameters was established.
  • Engineering Safety and Disaster Prevention
  • SONG Bao-gang, BAO Teng-fei, XIANG Zhen-yang, WANG Rui-jie
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 145-151. https://doi.org/10.11988/ckyyb.20220379
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    A spatio-temporal prediction model for dam deformation is proposed, which incorporates the wavelet theory and the Sparrow Search Algorithm (SSA) to optimize the extreme learning machine (ELM). This model addresses the challenge of accurately describing the overall response characteristics of dam deformation using single measurement point prediction models which fail to account for the spatial relations among measure points. Additionally, it overcomes the limitations of statistical models based on regression analysis, which struggle to uncover the complex nonlinear mapping relationship between environmental variables and the magnitude of deformation, often resulting in poor prediction accuracy. To validate the feasibility of the proposed approach, an actual dam project is taken as an illustrative example. The approach begins with wavelet analysis to eliminate noise from the original displacement measurements of the dam. Subsequently, the influence of coordinate changes in the measurement points on displacement is considered. SSA-ELM is employed to establish non-linear models for independent and dependent variables, constructing a spatio-temporal prediction model for dam deformation based on wavelet analysis. Application of the proposed model to a real-world example demonstrates its ability to accurately predict deformation across non-arranged measuring points. The model exhibits impressive performance indicators, including a highly significant complex correlation coefficient of 0.996 8, a root mean square error of 0.340 4, and an average absolute error of 0.275 4, which exceed those achieved by both the ELM model and statistical model. By integrating both temporal and spatial dimensions, the proposed model achieves high prediction accuracy and holds significant value as a reference for the analysis and evaluation of dam safety.
  • LI Jian-zhou, HAN Xian-quan, WAN Peng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 152-156. https://doi.org/10.11988/ckyyb.20221719
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    The quality of line and surface fitting results has a direct impact on the accuracy of subsequent data processing, making it a crucial step in point cloud data processing. To address the limitations of traditional RANSAC (Random Sample Consensus) algorithms in the effectiveness and accuracy of plane fitting for buildings, we introduce a sequential normal vector detection mechanism and propose an improved algorithm called M-RANSAC. The M-RANSAC algorithm enhances plane and edge detection by introducing increased angle constraints to the fitting model. To validate the feasibility and effectiveness of this method, a comparison was made with the conventional total station measurement method and the traditional RANSAC algorithm. The results confirmed the superiority of the proposed approach. Furthermore, the method was successfully applied in the current situation survey of buildings along the Pearl River Delta water resources allocation project. In conclusion, the M-RANSAC algorithm offers improved accuracy and efficiency in line and surface fitting.
  • Hydraulic Structure and Material
  • WANG Hou-mi, LIU Chao, MING Feng
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 157-162. https://doi.org/10.11988/ckyyb.20220259
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    Laying insulation materials is an effective measure to mitigate the freezing damage to channels. However, the absorption of moisture by insulation materials can lead to a deterioration in their thermal insulation performance. To investigate the impact of moisture content on thermal conductivity of insulation materials, a model predicting thermal conductivity taking moisture content into account was established using the homogenization method based on the minimum thermal resistance law. Furthermore, the influence of porosity and moisture content on thermal conductivity was examined. The proposed model was then validated against experimental results and an existing model. The findings reveal that thermal conductivity decreases with the increase of porosity, but increases with the increase of moisture content. The error between the predicted and measured results is less than 5%, thereby confirming the feasibility of the proposed model in calculating the thermal conductivity of insulation materials. Additionally, moisture is identified as a significant factor in diminishing the thermal insulation performance of polyurethane rigid foam. Consequently, enhancing the hydrophobic properties of insulation materials holds great practical significance in improving its thermal insulation performance. Several suggestions are put forward to enhance the hydrophobicity of polyurethane insulation materials.
  • JIANG Chun-meng, LI Shuang-xi, JIANG Lin-hua, TANG Xin-jun
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 163-169. https://doi.org/10.11988/ckyyb.20220223
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    Freeze-thaw damage and abrasive wear are common types of deterioration in hydraulic concrete in cold regions. To scientifically evaluate the abrasive performance of low heat cement concrete under freezing and thawing, abrasive tests were conducted on low heat cement concrete samples using underwater steel ball method under different degrees of freeze-thaw damage achieved through rapid freezing. The interactive relationships between Vickers hardness, damage layer thickness, abrasive depth, abrasive morphology, and fractal dimension with respect to abrasion age were investigated. Results indicate that freeze-thaw damage in concrete is a continuous and non-synchronous process influenced by surface-to-interior deterioration and overall degradation. Abrasion is a physical destruction occurring layer by layer from the surface to the interior. With an increasing number of freeze-thaw cycles, the overall Vickers hardness of the concrete decreases, and the damage layer thickness increases. Additionally, at the same abrasion age, the abrasive depth and surface fractal dimension increase. Within a 72-hour abrasive cycle, the average abrasive depth for concrete subjected to 50, 100, and 200 freeze-thaw cycles is less than the corresponding damage layer thickness. The obtained evolution patterns of concrete properties under the combined effect of freeze-thaw and abrasion provide references for the evaluation of multifactor-induced damage in concrete materials.
  • JIA Wen-zhen, LI Lei
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 170-176. https://doi.org/10.11988/ckyyb.20220137
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    To investigate the combined effects of loading rate and water saturation on the mechanical properties and failure mechanisms of basalt fiber reinforced concrete, non-metallic ultrasonic detectors and other devices were used to measure porosity, water saturation, and longitudinal wave velocity of the specimens. Compression tests were performed on saturated and dry specimens under different strain rates, using a universal testing machine and a split Hopkinson pressure bar with a diameter of 74 mm. The impacts of strain rate and water saturation on peak stress, elastic modulus, longitudinal wave velocity, and stress-strain relationships were also analyzed. Results showed that the porosity of basalt fiber reinforced concrete ranged from 1.89% to 3.05%, and a positive linear correlation was observed between the porosity of the specimens and their saturation levels. Water saturation accelerated the propagation of longitudinal waves inside the specimens. Under static loading conditions, the peak stress of saturated specimens was 8.6% lower than that of dry specimens, while the peak stress and elastic modulus of both types of specimens increased with increasing strain rates. Results also revealed a significant strain rate effect on specimens, with stress increase more pronounced in saturated specimens compared to dry ones. When the strain rate reached 130 s-1, the stress levels in dry and saturated specimens were largely consistent. However, at a strain rate of 160 s-1, the peak stress of saturated specimens was 11.4% higher than that of dry specimens. The elastic modulus showed a similar behavior to the strength. Water saturation led to erosion and degradation of the concrete as well as dynamic coupling strengthening effects between the water and fiber. Under static loading, softening effects of water and crack extension due to hydrostatic pressure at the crack tip reduced the ability of specimens to resist external loads. Under dynamic loading, negative pressure within pores and the Stefan effect hindered crack extension and the failure of the specimens. The critical strain rate corresponding to the same stress levels for both dry and saturated specimens was found to be 130 s-1.
  • Water Conservancy Informatization
  • YANG Han, XIONG Li-hua
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 177-183. https://doi.org/10.11988/ckyyb.20220307
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    To acquire accurate soil moisture information in time and space, soil moisture information (surface soil moisture SSM and profile soil moisture PSM) from multiple satellites (SMOS, ASCAT, ESA CCI and SMAP) is compared with PSM simulations from a distributed hydrological model. The comparison is developed at daily scale and catchment/grid scale in a humid catchment (Qujiang catchment) and a semiarid catchment (Yiluohe catchment) in China. Results indicate that SMAP PSM show higher consistency with simulated PSM when the performance of simulated PSM is high in a catchment, with the correlation coefficient reaching 0.8. Thus, the accuracy of SMAP is regarded to be relatively higher compared to other satellite products. The research offers guidance and practical values for acquiring accurate soil moisture information in time and space.
  • ZHAO Su-ting, YUAN Jie, LIU Jia-cheng, LI Fu-shan, TANG Hong-bo, LÜ Xin-hua
    Journal of Changjiang River Scientific Research Institute. 2023, 40(8): 184-190. https://doi.org/10.11988/ckyyb.20220329
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    The protection of ecological environment in the Yangtze River has been receiving close attention from central government, local governments at various levels, as well as numerous departments. Substantial achievements have been made in this field. Employing qualitative analysis and quantitative evaluation through information science research methods, we comprehensively examine the development process and important measures related to ecological environmental protection in the Yangtze River based on an extensive review of relevant literature. Additionally, subject research papers were retrieved, and statistical analysis was conducted by utilizing VOSviewer visualization software based on the CNKI literature database to analyze the time distribution, spatial distribution, subject distribution, source distribution, and author distribution. Research hotspots were identified based on high-frequency keywords and highly cited papers. The outcomes of this study offer valuable reference information for government departments, scientific research personnel, and research management institutions. Moreover, it will facilitate innovative research in the realm of ecological and environmental protection in the Yangtze River.