01 May 2023, Volume 40 Issue 5

    

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  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 0-0.

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Special Contribution
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  Embankment Breach Due to Overflowing: Mechanism, Models, Flood Simulation Technologies, and Their Applications

  Yong-hui ZHU, Jian-yin ZHOU

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 1-8. https://doi.org/10.11988/ckyyb.20220979

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  Over the years, researchers in the River Research Department of the Changjiang River Scientific Research Institute has conducted extensive studies on the mechanism, models, and simulation technologies of embankment breaches due to overflowing. These efforts were aimed at enhancing the ability to respond to embankment breach emergencies and to defend associated disasters. Through the use of physical model tests, flume tests, theoretical analysis, numerical simulation, and other methods, the department has made significant contributions to the field. Specifically, we have uncovered the mechanism of embankment breaches due to overflowing, analyzed the role of “headcut erosion” in the breaching process, and introduced patterns of headcut erosion and phases of embankment breaching due to overflowing. Additionally, we have developed a two-dimensional mathematical model of headcut erosion and a mathematical model of embankment breaching based on the physical mechanism. Furthermore, we have created one-, two-, and three-dimensional flood simulation technologies that are adapted to the characteristics of dam-breaking flow, along with a terrain processing method, and have preliminarily explored the three-dimensional flow field and hydrodynamic pressure characteristics of dam-breaking flow. Last, we made a review on the research progress in related fields and the achievements published in scientific journals. The accomplishments of the department have already proven to be highly effective in emergency response and decision-making, specifically during the Tangjiashan and Baige barrier lake breach emergencies. These achievements provide technical reference and experience for addressing embankment breach (including barrier lake burst) dangers in the future.

Comprehensive Management of River Basin
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  Progresses, Predicaments and Optimization Paths of Transverse Watershed Ecological Compensation in the Yangtze River Economic Belt

  REN Jun-lin, KUANG Yang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 9-14. https://doi.org/10.11988/ckyyb.20220325

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  Transverse ecological compensation in river basin is an important means to promote high-quality and green development in the Yangtze River Economic Belt. While transverse compensation within provinces of the Yangtze River Economic Belt has made rapid progress, compensation between provinces in the main stream and tributaries of the Yangtze River has lagged behind. In an attempt to promote the construction of transverse ecological compensation and optimize the paths of transverse ecological compensation among provinces in the Yangtze River Economic Belt, we systematically examine the progress, theoretical and practical challenges facing the ecological compensation system in the Yangtze River Economic Belt. Problems include low awareness among residents, limited scope, single compensation methods, ambiguous standards, and an inadequate supervision and evaluation system system. To address these challenges, we propose that measures should be taken to strengthen institutional support, promote policy, deepen interdepartmental collaboration, establish comprehensive compensation frameworks with multi-party participation, explore market-oriented and diversified compensation methods, and improve the monitoring and post-assessment system.
River-Lake Protection and Regulation
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  Hydrological Regime Effect of Qigongling Bend Cut-off in the Lower Jingjiang River

  YI Fang-hui, PENG Chi-bin, LI Mi, LU Xiang, GUO Xiao-hu, LUAN Zhen-yu, LI Hong-xiang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 15-21. https://doi.org/10.11988/ckyyb.20220844

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  Since the Three Gorges Reservoir began impounding water, the Qigongling bend in lower Jingjiang River has experienced convex bank erosion and concave bank deposition. The narrowing of the Baxingzhou section due to bank collapses has created a risk of river channel cut-off. Drawing on observation data, we analyzed the precise location of the cut-off in the Qigongling bend, designed a new cut-off channel, and established a 1D-2D coupled, non-steady flow model covering the Dongting Lake and the middle reaches of the Yangtze River to assess the hydraulic effects of the cut-off under typical operating conditions. Results reveal that the cut-off at Qigongling bend will have a considerable impact on the water levels in upstream and downstream river sections and Chenglingji, the flow diversion and zero-flow days at the three outlets of Jingjiang River, as well as the confluence relationship between Jingjiang River and Dongting Lake. Our study provides technical support for assessing flood prevention measures near Chenglingji and for proposing relevant emergency plans. It is of reference value for safeguarding flood control safety in the region and managing and protecting the confluence area of the Jingjiang River and the Dongting Lake.
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  Preliminary Research on the Causes and Control Measures of Elodea nuttallii Disaster in Dajiangkou-Wangfuzhou Riverway

  GUO Chao, ZHOU Yin-jun, YAO Shi-ming, SHAN Min-er, YAN Jian, CHEN Hua

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 22-28. https://doi.org/10.11988/ckyyb.20220403

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  The massive growth of submerged plants can cause serious harm to the water conservancy functions of rivers, lakes, and reservoirs. One such plant is Elodea nuttallii, which is widely spread around the world and has adverse economic and ecological effects on many countries. In 2017 and 2019, Elodea nuttallii caused a disaster in the Danjiangkou-Wangfuzhou riverway in the middle and lower Hanjiang River, severely affecting the power generation, shipping, and water supply of the Wangfuzhou hydropower station. It also posed a threat to flood discharge, regional water quality, and water ecological security. We investigated the spatiotemporal characteristics of Elodea nuttallii growth and analyzed the cause of the disaster and its impact. In line with the requirements of water eco-environmental protection and the growth characteristics of Elodea nuttallii in the Danjiangkou-Wangfuzhou reach, we proposed two physical control methods based on control measures for submerged plants worldwide. The proposed methods involve ecological scheduling and local terrain modification to create an unsuitable terrain and hydrodynamic environment for Elodea nuttallii, thereby fundamentally inhibiting its growth and reproduction.
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  Morphological Adjustment and Spatio-temporal Evolution Characteristics of Typical Central Bars in the Reach of the Three Gorges Reservoir after Impoundment

  TANG Qing-qing, JI Yong-yue, YAN Ling-yun, ZENG Si-dong, TANG Xiao-ya, LI Jin-lin, YU Yong, CHEN Ji-long

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 29-37. https://doi.org/10.11988/ckyyb.20220239

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  The operation of the Three Gorges Reservoir has significantly altered the original hydrodynamic conditions of the river and led to adjustments in the morphology of central bars. To further investigate the effects of Three Gorges Reservoir impoundment on the morphological adjustments of central bars, we selected five typical central bars in the reservoir area as study objects. Using Landsat remote sensing images and terrain and water-sediment data from 2003 to 2017, we quantitatively analyzed the spatial and temporal evolution characteristics of the morphological adjustments of the central bars at different stages. Results showed that with the fluctuation of the water level in the Three Gorges Reservoir, the exposed area of central bars gradually decreased, and the riverbed showed an accumulated siltation trend, which accelerated the morphological changes of central bars. The strongest siltation occurred at a water storage elevation of 156 m (October, 2006 to 2008), while siltation significantly attenuated after 2012. At spatial scale, the further away from the dam, the smaller the siltation intensity of central bars. Due to sand mining, central bars in the area affected by the backflow of the reservoir were subjected to irregular changes in local riverbed topography. Meanwhile, the backflow of the Three Gorges Reservoir changed the development mode of central bars. Specifically, the downstream end of the bars developed and was silted towards the downstream, while the upstream end was eroded by clear water flow.
Water Resources
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  Variation and Correlation Analysis of Lakewater Storage and Terrestrial Water Storage Anomaly in Poyang Lake

  LI Xiao-ying, TONG Ze-chun, WANG Bi-lei, LEI Sheng

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 38-43. https://doi.org/10.11988/ckyyb.20220914

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  Due to human activities and climate change, the hydrological regime of Poyang Lake has undergone significant changes. Understanding the variation in its water storage is of great significance for the comprehensive utilization of water resources in the basin. In this study, we used the Google Earth Engine (GEE) platform to analyze the long-term monthly trends of lake area changes from 2003 to 2020 and combined them with measured water levels to estimate the variation in water storage of Poyang Lake. We also calculated the variation in terrestrial water storage in the lake area using the GRACE Mascon product data and analyzed the relationship between the variation in lake water storage and terrestrial water storage. The results showed that the long-term trends in the extracted lake area based on the GEE platform and the variation in terrestrial water storage retrieved from GRACE data were consistent with the measured water level changes at the Xingzi station. Remote sensing images indicated that the water body area in the southern part of the lake changed slightly, and the area with perennial water expanded. The GRACE data also manifested that the average terrestrial water storage in the south part was slightly higher than that in the north. The consistency between the abrupt change points in the variation of terrestrial water storage and the water level at Xingzi station was confirmed by a change point analysis. Wavelet analysis revealed a significant correlation between the variation in lake water storage calculated using the volume method and the variation in terrestrial water storage. Moreover, the variation in lake water storage had a significant impact on the variation in terrestrial water storage of Poyang Lake.
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  Effects of Land Use and Climate Change on Spatial Distribution of Hydrological Factors in Tongzi River Basin

  ZHENG Ting-ting, CAI Hong, LIU Jia-wei

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 44-50. https://doi.org/10.11988/ckyyb.20211405

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  The Soil and Water Assessment Tool (SWAT) hydrological distribution model of Tongzi River Basin was established with four scenarios to quantify the effects of land use and climate change on the spatial distribution of hydrological factors in the basin. Results demonstrate that: 1) The SWAT model is well applicable to the Tongzi River Basin as the R² and NS coefficient of monthly runoff simulation reach over 0.83 in both calibration period and validation period.2) The sub-basins with the largest annual average runoff depth, large underground runoff and large water yield all distribute in the south part of the Tongzi River Basin where surface slope gradient is large and precipitation is concentrated. However, runoff depth cannot be used to replace hydrological factors because the distribution of runoff depth does not conform with those of surface runoff, soil moisture content and other hydrological factors.3) The spatial distribution trend of hydrological factors under both land use and climate changes is generally consistent with that under the climate change scenario.The research findings offer scientific basis for the rational development and utilization of water resources in Tongzi River Basin.
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  Method of Water Conflict Coordination Based on Stakeholder Preference

  WANG Fa-qiang, FU Xiang, JIN Wei-rong, XIE Heng-wang, LIU Shuang-jun

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 51-57. https://doi.org/10.11988/ckyyb.20220045

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  A water conflict coordination method based on stakeholder preference is presented to address the contradiction between supply and demand of water resources and the deterioration of water environment. The conflict between the objectives of stakeholders is analyzed to obtain the non-inferior solution set. On this basis, the concepts of equal preference, non-cooperative preference and cooperative preference of stakeholders are introduced to establish the model of water conflict coordination. The coordination solution is obtained, and finally the impact of stakeholder preferences on different water users is analyzed. The model is applied to the Ganjiang-Fuhe River Plain Irrigation Area, and the results show that the model solution based on the non-inferior solution set improves the environmental utility at the cost of economic utility. The coordination solution obtained by the equal preference model and the non-cooperative preference model is similar to that of the cooperative preference model. This suggests that when it is difficult for stakeholders to cooperate, the solution of the equal preference model and the solution of the non-cooperative preference model based on the non-inferior solution set can replace the solution of the cooperative preference model. Compared with traditional decision-making method with the maximum total utility, the presented three preference models pay more attention to environmental utility. The water shortage in Ganjiang-Fuhe River Plain Irrigation Area is mainly shared by agricultural sector because the water consumption of agricultural sector accounts for about 40%, and the sewage discharge accounts for about 30%. To reduce the total sewage discharge, it is necessary to reduce the water consumption of sectors with large sewage discharge, which also indicates the required water-saving amount. The research provides a practical analysis method for water-saving priority and environmental protection.
Water Environment and Water Ecology
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  Variation Characteristics and Flux of TN and TP in Water Level Fluctuation Zone of Danjiangkou Reservoir

  JIN Hai-yang, WANG Li, ZHAO Liang-yuan, QIN He, TAO Jing-xiang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 58-62. https://doi.org/10.11988/ckyyb.20220031

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  Study on the variation characteristics and flux of total nitrogen(TN) and total phosphorous (TP) in soil in the water-level-fluctuation zone of Danjiangkou reservoir is of practical significance for clarifying the pollution output characteristics and protecting the water quality of the reservoir. In this paper, Danjiangkou reservoir was divided into Hanku reservoir and Danku reservoir. The variation characteristics of TN and TP in soil in the typical water-level fluctuation zone of Danjiangkou reservoir in different periods from September 2020 to September 2021 were monitored and analyzed. In addition, the TN and TP fluxes were estimated by using the break-even model. Results reveal that during the flooding period from September 2020 to December 2020, the content of TN and TP in different water-level-fluctuating areas of Danjiangkou reservoir changed significantly. To be specific, the content of TN and TP in the farmland and garden fields of Hanku reservoir increased notably, while TN and TP were lost in other areas. During the water-level-falling dry period from March 2021 to June 2021, the content of TN and TP in different water-level-fluctuation zones of Danjiangkou reservoir showed an increasing trend on the whole. From September 2020 to September 2021, the content of TN and TP in different water-level-fluctuation zones of Danjiangkou reservoir displayed a decreasing trend. During flooding period, the water-level-fluctuation zone of Danjiangkou reservoir acted as the release source of nitrogen and phosphorus, with TN flux reaching 834.66 t and TP flux 10 422.12 t. During water-level falling dry period, the water-level-fluctuation zone of Danjiangkou reservoir acted as the sink of nitrogen and phosphorus, with TN flux of -8 623.69 t and TP flux -10 032.94 t. From September 2020 to September 2021, the water-level-fluctuation zone of Danjiangkou reservoir acted as the release source of nitrogen and phosphorus on the whole, with TN flux amounting to 20 122.22 t and TP flux 1 509.52 t. The pollutant release risk of water-level-fluctuation zone of Danjiangkou reservoir should not be ignored as it poses a threat to the water quality of the reservoir.
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  Water Quality Analysis and Pollution Evaluation of Drainage Ditches into Wuliangsuhai Lake

  WEI Xue-min, WEN Ya-qin, WANG Zhi-jun, GOU Mang-mang

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 63-69. https://doi.org/10.11988/ckyyb.20211400

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  Ulansuhai Nur (Wuliangsuhai Lake) is one of the eight freshwater lakes in China and is also the “natural kidney” of the Hetao irrigation area. Receiving 90% of the farmland drainage in the area, Wuliangsuhai inevitably suffers from surface water pollution problems. To understand the water quality of drainage ditches into the Wuliangsuhai, water samples were collected from the tail sections of drainage ditches including the major drainage canal, the eighth, ninth, and tenth drainage canals in the Hetao irrigation area. Laboratory tests were then conducted to investigate the water quality of drainage ditches into the lake on a short-term time scale (2018-2020) from spatial and seasonal perspectives with pH value, chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total phosphorus (TP), and total nitrogen (TN) as assessment indicators. Pollution was evaluated by using single-factor index method and Nemerow pollution index method combined with cluster analysis. Results demonstrate that: (1) COD and TN were major pollutants in the drainage ditches into the Wuliangsuhai Lake, followed by NH₃-N and TP. (2) The major drainage canal and the eighth drainage canal mainly suffered from severe TN pollution, and the ninth and tenth drainage canal COD pollution followed by TN pollution. (3) From a seasonal perspective, pollution was severe in winter and spring, and moderate in summer and autumn. Throughout the year, the major drainage canal and the tenth drainage canal were in a state of slight pollution, while the eighth and ninth drainage canals were clean. (4) According to the pollution load and cluster analysis, the major drainage canal had the highest annual pollution load, accounting for 81.82%. COD and TN were major factors affecting the pollution load. Therefore, management to the agriculture process in the Hetao irrigation area shall be strengthened. In the meantime, the drainage in winter and spring, in particular, COD and TN concentration in the drainage, should be monitored and treated.
Soil and Water Conservation and Ecological Restoration
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  Enrichment Characteristics and Potential Ecological Risks of Heavy Metalsin Alpine Swamp Meadows Soils in the Southern Piedmont of Qilian Mountains

  XU Tai, E Chong-yi

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 70-76. https://doi.org/10.11988/ckyyb.20211229

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  The purpose of this research is to understand the pollution degree, ecological risk and spatial distribution characteristics of heavy metals in the soil of Qilian Mountain National Park. The content of V, Cr, Mn, Ni, Cu, Zn, Cd, Pb, As, and Hg in 0-10 cm and 10-20 cm of swamp meadow soils in the southern piedmont of Qilian Mountains were tested. The pollution coefficient and enrichment coefficient were used to study the enrichment rules and pollution characteristics of heavy metals in different parts. The human contribution rate was used to supplement and verify the results. Finally, the risk status was quantitatively assessed through the potential ecological risk index. Results showed that: 1) The average content of Cr, Zn, and Hg in the 0-10 cm and 10-20 cm swamp meadow soils are higher than the background value of Qinghai Lake soil. Cr and Zn are slightly enriched while Hg is the most obviously enriched with the human contribution rate reaching 30%. 2) The average content of V, Mn, Ni, Cu, Cd, Pb, and As shows no difference with the natural values. The human contribution rate is negative and shows an increasing trend as depth increases. It is worthy of attention that point source pollution exists at some sampling points. 3) The potential ecological risk value of heavy metals in descending order is Hg>Cd>As>Ni>Cu>Pb>Cr>V>Zn>Mn. Except for Hg, the other nine heavy metals are all at a status of level-I ecological pollution risk, which means slightly polluted. 4) The comprehensive potential ecological risk index (RI) of heavy metals in swamp meadow soil reached level-II medium ecological pollution in both 0-10 cm and 10-20 cm. The contribution rate of Hg to RI reached more than 50%. In general, heavy metal pollution in swamp meadow soil poses potential risk. Sufficient attention should be paid to the pollution control of swamp wetland. This research can provide basic data for the governance and improvement of ecosystem in the hinterland of the southern foothills of the Qilian Mountains.
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  Phenology of Vegetation and Its Response to Climate Change in the Western Sichuan Plateau

  WANG Ye-lan, YANG Xin, HAO Li-na

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 77-84. https://doi.org/10.11988/ckyyb.20220041

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  The aim of this research is to investigate the spatiotemporal changes in vegetation phenology and their response to climate change in the Western Sichuan Plateau from 2001 to 2020 and provide insights for the study of vegetation phenology changes in the plateau. Based on MODIS NDVI data, vegetation zoning data, digital elevation data, and meteorological data, we extracted the SOS (start of the growing season), EOS (end of the growing season), and LOS (length of growing season) of vegetation by using the Savitzky-Golay filter and dynamic threshold method. We then explored the relationship between vegetation phenology and climatic factors, such as monthly mean temperature and precipitation. Results indicate that 1) the SOS, EOS, and LOS of vegetation in the Western Sichuan Plateau were mainly concentrated in the 90^th to 130^th days, 260^th to 290^th days, and 130-190 d, respectively. As altitude increased, the SOS trended towards an advance, while EOS trended towards a delay, and LOS trended towards an extension. 2) Specifically, 60.56% of the vegetation area exhibited an advanced SOS trend, 51.21% a delayed EOS, and 60.75% a prolonged LOS, of which 7.19% showing a significant prolonged LOS trend. 3) The SOS of vegetation was negatively correlated with mean temperature from February to April, displaying significant spatio-temporal differences. Additionally, a significant positive correlation was found between EOS and average temperature in October, and precipitation in November. Moreover, average temperature in June and precipitation in August had a significant positive effect on LOS. Overall, the phenology of vegetation in the Western Sichuan Plateau displayed distinct distribution rules in different vegetation divisions.
Rock-Soil Engineering
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  Dynamic Mechanical Properties and Damage Characteristics of Coral Reef Limestone under Impact Loading

  LEI Xue-wen, LI Hao-ming, MENG Qing-shan, HONG Sheng-nan, ZHOU Hao-ran, JIANG Xue

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 85-93. https://doi.org/10.11988/ckyyb.20211402

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  To investigate the dynamic mechanical properties and damage characteristics of two types of coral reef limestones under impact loading, split Hopkinson pressure bar (SHPB) test apparatus was used to conduct impact compression tests on coral lattice limestone and coral clastic limestone in the strain rate range of 10~190 s^-1. The stress-strain curves of reef limestone under different strain rates were analyzed to obtain the strain rate effect and energy dissipation of dynamic peak stress and elastic modulus. In addition, the damage and failure characteristics of samples were revealed using high-resolution CT scanning and image processing technology. Results show that the dynamic stress-strain curves of lattice limestone exhibit an obvious elastic deformation stage, while the compaction stage of clastic limestone is more apparent. Furthermore, the dynamic peak stress increases as a power function with the increase of strain rate, and the strain rate effect of lattice limestone is stronger. The relationship between dynamic elastic modulus and strain rate is negatively exponential. Moreover, the energy absorption capacity of lattice limestone is stronger than that of clastic limestone. The damage cracks of reef limestone are mostly found along sites with poor cementation of biological components or many penetrative pores. Under medium and high strain rates, the damage cracks of lattice limestone mainly undergo matrix propagation and transfixion, presenting brittle fracture failure, and clastic limestone perforation propagation, presenting crushing failure mode. The research findings are of guiding significance for preventing dynamic disasters in island and reef engineering construction.
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  Experimental Study on Pore Size Characteristics of Woven Geotextiles under Different Illuminance

  TANG Xiao-wu, LI Ke-yi, ZHAO Wen-fang, CHEN Shi-hua, LIN Wei-kang, LIANG Jia-xin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 94-99. https://doi.org/10.11988/ckyyb.20211327

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  Pore size of woven geotextile is a crucial parameter in filter design. The digital image method is a precise and repeatable technique. In this study, we used illuminance to examine the impact of light source distance and brightness on textile image quality. Images were collected under different illuminance levels, and the changes in pore shape, pore size distribution curve, and characteristic pore size of two different textile specifications were analyzed. The actual average pore size of the geotextiles was compared with the fitted straight line of the average pore size under different illuminance levels. Experimental results show that with the increase of illuminance, the measured hole area increases, and the hole shape changes. The pore size distribution curve moves towards the direction of the increase of pore size, and the measured values of characteristic pore size (d₉₅,d₅₀,d₃₀) increase. The average measured pore size presents an increasing trend, which can be expressed as a linear regression equation. The pore size obtained by the digital image method differs from the actual pore size. The optimal illuminance for the two textiles falls near 9 lx. Therefore, the best illuminance should be determined through experiments to reduce error.
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  Route Selection for Water Diversion Project from Three Gorges Reservoir to Hanjiang River Based on Engineering Geology

  WANG Ji-liang, XIANG Jia-bo, YAN Hui-ming, DENG Zheng-rong, JIA Jian-hong, XU Qi

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 100-105. https://doi.org/10.11988/ckyyb.20221280

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  The Water Diversion Project from the Three Gorges Reservoir to the Hanjiang River (WDTGH) is a follow-up project to the Middle Route Project (MRP) of the South-to-North Water Diversion (SNWD). During the feasibility study stage, four routes of water conveyance tunnel under the Danjiangkou dam were proposed for comparison based on their topographical and geological conditions and engineering geological problems. The geological conditions of the proposed routes are complex, with long routes, large burial depths, varied formation lithology, abundant dissolvable rocks and soft rocks, complex geological structure background, and high overall geostress levels. Therefore, it is necessary to select a route with relatively good geological conditions to avoid engineering geological problems that may occur in the deep-buried long tunnel project. Through analysis, the geological factors considered in the comparison and selection of the routes were classified into three levels as key geological factors, important geological factors, and general geological factors. A comparison model under the condition of multiple factors was established for comprehensive analysis and comparison on engineering geology. The study reveal that the water tunnel scheme of Long'an Line 1 has overall advantages. Thus, the results of geological route selection provide foundation for comprehensive route selection in engineering design. Additionally, the research ideas and methods of geological comparison and selection can serve as a reference for similar projects.
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  Dynamic Cluster Grouping Analysis of Occurrence of Structural Plane in Natural Rock Mass

  AI Chun-ming, LU Yun, SUN Ping-ping

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 106-110. https://doi.org/10.11988/ckyyb.20211311

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  The grouping of natural structural planes is critical in rock mass engineering. Traditional grouping methods are inaccurate in grouping structural planes with near-vertical or near-horizontal occurrence. In view of this, a dynamic clustering analysis method for structural planes is proposed. The clustering center is determined based on the dip angle and inclination of structural planes, and the grouping result is obtained by iterative calculation based on the angle between structural planes. The method was applied to group 303 structural planes in Bayan Obo East mine and compared with the fast clustering method. Three dominant groups of structural planes were identified after the grouping of 303 structural planes, which agree well with the isodensity map of structural plane occurrence. The dynamic clustering analysis method is not only simple and easy to calculate but also overcomes the limitations of traditional methods in quantification, making the grouping of structural planes more accurate and practically significant.
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  Identification of Stratum Reinforced by Vibro-replacement Stone Column Based on Fuzzy C-means Clustering Algorithm

  WEI Yong-xin, ZHAO Gu-yao, TUO Xiao-jun, ZHAO Yu-fei, LIU Biao

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 111-117. https://doi.org/10.11988/ckyyb.20211361

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  Accurately obtaining the geological information of soft foundation is an essential basis for determining the construction technique and controlling the pile quality of vibro-replacement stone columns. The existing geological exploration technology used to determine stratum information is considerably random and discrete, which makes it impossible to comprehensively understand the geological conditions of the reinforced areas. To overcome these limitations, this study relies on a large amount of data related to stratum classification attributes collected by the real-time monitoring system during the construction process of vibro-replacement stone columns at Lawa Hydropower Station. By cleaning big data, features such as penetration depth, speed, and current related to stratum classification attributes were selected for fuzzy C-means clustering algorithm-based study of stratum identification of the soft foundation. The results indicate that compared to the traditional K-means algorithm, the method proposed in this paper exhibits higher accuracy and superiority in identifying strata and enables real-time research and judgment of geological conditions. The research findings presented in this paper are of great significance in the rational evaluation of vibro-replacement stone column construction quality and the intelligent construction of the pile formation process.
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  Effect of Coarse-grain Content on Shear Properties of Coral Reef-Sand Mixtures

  PAN Jian-feng, LEI Xue-wen, MENG Qing-shan, QIN Dong-lai, FU Jin-xin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 118-124. https://doi.org/10.11988/ckyyb.20211280

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  Coral reef-sand mixture is an important supporting layer of infrastructure. To investigate the effect of particle gradation composition on shear strength and dilatation of coral reef-sand mixtures, simple shear tests were performed using fully automatic medium-sized stacked ring direct shear instrument. The tests were conducted on samples with varied P₅ content and water content under four different normal stresses of 50, 100, 200, and 400 kPa. The experimental results show that the shear strength of coral reef-sand mixtures first increases and then decreases with the increase of P₅ content. The shear strength reaches its maximum when P₅ content is 25%-50%. In the shearing process, coral reef-sand mixtures contracted first and then dilated. P₅ content has a significant effect on dilatation, internal friction angle, and apparent cohesion. Water content weakens the shear strength of coral reef sand mixture.
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  Horizontal Displacement of Adjacent Pipeline Induced by Excavation in Consideration of Spatial Effect

  LI Yong-huan, LIU Zhi-he, RAO Qin-bo, GUO Jin, HU Hai-bo, LIU Qiu-yuan, YANG Ying

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 125-130. https://doi.org/10.11988/ckyyb.20220423

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  Excavation of foundation pits can cause adverse effects on adjacent pipelines due to the displacement of the surrounding soil. An analytical method for predicting the additional horizontal deformation of adjacent pipelines caused by excavation is proposed using a three-dimensional image source method. Nearby pipelines are treated as Euler-Bernoulli beams on a Pasternak foundation in consideration of the spatial effect of excavation and the spatial distribution of pipelines. The validity of the proposed method is demonstrated through existing cases. Results indicate that the total horizontal deformation of pipelines is primarily induced by the deformation of retaining walls that are adjacent and parallel to the pipelines. The deformation of retaining walls on both sides also significantly impacts the horizontal deformation of pipelines outside the excavation area. The adverse effects of excavation on pipeline's horizontal deformation can be predicted through defining a safety factor and considering different spatial distributions of pipeline. The influence zone of excavation on pipeline deformation can be obtained through plotting contours of the safety factor. When the distance between the pipeline and the retaining wall is within 0.75H (where H is the depth of foundation pit excavation), the safety factor first decreases and then increases with the increase of pipeline's burial depth. The safety factor reaches its minimum when the pipeline is buried at a depth of approximately 1.0H. When the distance between the pipeline and the retaining wall exceeds 0.75H, the safety factor increases with the increase of pipeline's burial depth.
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  A Foundation Treatment Scheme of a Large Bulk Cargo Wharf Storage Yard

  XU Yan-yan, LIU Jun-wei, CHEN Na, WEI Lai

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 131-138. https://doi.org/10.11988/ckyyb.20221536

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  The aim of this research is to optimize the foundation reinforcement of a large bulk cargo wharf storage yard on the right bank of the middle and lower reaches of the Yangtze River. With reference to the Code for Design of Water Transport Engineering Foundation (JTS 147—2017), the treatment scheme comprehensively considers the geological conditions of the project area, the foundation load of the belt conveyor corridor, the bearing capacity of the bulk cargo stockpiling area and the requirements of settlement and displacement of foundation treatment. PHC(Prestressed High-intensity Concrete) pipe method and CFG(Cement Fly-ash Gravel) pile method were adopted for comparison for the foundation treatment between two pit belt conveyor corridors (area A), and cement soil mixing pile method and gravel pile method for other areas (area B). Geotechnical software GEO5 was used to calculate the foundation deformation (settlement and horizontal displacement) in different operating conditions (full load and partial load) under different combinations of the above four treatment methods. With the engineering economy and construction period taken into consideration, an optimal scheme with CFG pile for area A and gravel pile method for area B was determined. After the optimal scheme was adopted for foundation treatment, the foundation settlement in area A is less than 100 mm, and the horizontal displacement smaller than 10 mm,which meets the requirements of Code for Design of Building Foundation(GB 50007—2011); the maximum foundation settlement of area B is 458.6 mm, and the maximum horizontal displacement 102.6 mm, which fulfills the requirements of Design Code of Road and Storage Yard for Port Area (JTS 168—2017). The research result provides a reliable basis for optimizing the design scheme of foundation treatment of storage yard in large bulk cargo wharf.
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  Effect of Colloidal Oxides on Microstructure and Swelling-Shrinkage Property of Red Clay

  ZHANG Xue-lian, WU Dao-yong, YE Lei, YUAN Bin-lin

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 139-144. https://doi.org/10.11988/ckyyb.20211298

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  The interaction between colloidal oxides and clay minerals is the major factor affecting the microstructure, swelling, and shrinkage of red clay. In this paper, the colloidal oxides are removed by the selective chemical dissolution method. The effects of colloidal oxides on the microstructure and swelling shrinkage of red clay are explored via swelling shrinkage test, particle size analysis, mercury injection, and SEM. Results illustrate that the colloidal oxides adhere to the clay mineral surface in the form of an envelope. The removal of colloidal oxides significantly changes the microstructure of soil. Moreover, the disappearance of the coating leads to the deterioration of soil structure bonding, weakening of agglomeration, increase of particle dispersion, decrease of micropores, and increase of pores. In addition, physical parameters of soil (specific gravity, optimal water content, maximum dry density, liquid plasticity, free expansion rate, and linear shrinkage rate) decrease since the removal of colloidal oxide. The research findings offer scientific basis for correctly understanding the special physical characteristics and enriching related basic theories of red clay.
Engineering Safety and Disaster Prevention
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  A Method of Identifying Surface Crack of Subway Tunnel in Consideration of Occlusions

  HUANG Yuan-yuan, PENG Qian, XU Bing

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 145-152. https://doi.org/10.11988/ckyyb.20211276

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  To enhance the accuracy of identifying surface cracks in subway tunnels, we propose an algorithm for recognizing and extracting crack features in subway shield tunnels taking into account the presence of obstructions based on deep learning and machine vision technology. We employed the convolution neural network to extract the features of cracks using image restoration technology, thereby obtaining accurate information on the cracks. First, we proposed a U-net-based method of segmenting the occlusions on the subway tunnel segment surface, marking the position information by a mask map. Then, we built a Faster R-CNN network model using VGG-16 as the feature extraction network to locate and mark the cracks in the tunnel segment image. By combining the results of the two, we can determine the relationship between the cracks and occlusions. Finally, we proposed the deep learning convolution neural network model in which the occluded crack information can be restored. The trained network model can predict the cracks in the occluded area. The experimental results demonstrate that the accuracy rate of the proposed method reaches 90% in repairing the occluded crack information, indicating its application value in actual tunnel disaster detection and comprehensive evaluation.
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  An OWOA-RFWSVR-DLM-based Model for Predicting Dam Deformation in the Alpine Region

  GE Pan-meng, CHEN Bo, CHEN Wei-nan, ZHU Ming-yuan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 153-159. https://doi.org/10.11988/ckyyb.20211348

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  Due to the protection of surface thermal insulation layer, the internal temperature of concrete dam in cold region lags behind the air temperature. When internal thermometers are lacking, HST (hydrostatic-seasonal-time) model generates large error in predictions; even when internal thermometers are present, MR (multiple regression) model can not refelct the nonlinear relation between temperature and deformation. To address the problem of inaccurate deformation prediction in alpine regions, we propose to use a support vector regression (SVR) weighted by the RReliefF algorithm and DLM(Distribution Lag Model) temperature factors to predict dam displacement. The necessary hyperparameters are optimized using an improved whale swarm approach with OBL (Opposition-based Learning). By comparing the performance of the proposed model with MR and other machine learning algorithms, we found that the proposed model has higher prediction accuracy and better reflects the working characteristics of an insulated concrete dam.
Hydraulic Structure and Material
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  Effect of Stone Powder Content in Tuff Manufactured Sand on Properties of Hydraulic Pumped Concrete

  YOU Qiu-sen, ZHANG Xian-yu, LI Xin-yu, XIE Guo-shuai

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 160-165. https://doi.org/10.11988/ckyyb.20211248

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  To determine the appropriate stone powder content in tuff manufactured sand, we prepared concrete specimens mixed with tuff manufactured sand which contains three levels of stone powder content at Xiamen pumped storage power station, and investigated the effects of stone powder content on the rheological properties, mechanical properties, early cracking resistance, and drying shrinkage of hydraulic pumped concrete. Results showed that an increase in tuff stone powder content from 8% to 18% caused an increase in unit water consumption, yield stress, and plastic viscosity of hydraulic pump concrete, as well as a decrease in early-age cracking resistance and an increased dry shrinkage, while the compressive strength and splitting tensile strength were only slightly affected. When the content of tuff stone powder was reduced to 8%, the hydraulic pumped concrete exhibited inferior cohesion and water retention. The optimal tuff stone powder content was found to be around 13% to improve the overall properties of the hydraulic pumped concrete.
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  Field Corrosion Test of Concrete in Salt Swamp Environment in Qinghai

  FENG Zhong-ju, CHEN Lu, KONG Yuan-yuan, WANG Fu-chun, CHEN Hui-yun, ZHANG Cong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 166-172. https://doi.org/10.11988/ckyyb.20211258

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  Field corrosion tests were conducted in salt swamp environments in Qinghai Province to investigate the corrosion of concrete in the region. The microstructure of concrete was observed under different burial conditions, and the durability of concrete was evaluated by assessing the mass loss, changes in anti-corrosion coefficient, and changes in corrosion rate of steel bars. Results indicate that changes in the mass of concrete can not be used as an evaluation index to describe concrete damage. Embedded in the ground or water, concrete mixed with cement-based materials exhibits the highest corrosion resistance coefficient, while concrete mixed with fly ash-silica fume has the highest corrosion resistance when buried at a depth of 1.25 m. Concrete deterioration results from multiple factors such as expansion force, freezing stress, and crystallization stress. The corrosion rate of concrete embedded in the ground, particularly reinforced concrete mixed merely with cement base, is the highest. The corrosion rate of concrete with fly ash-cement base is the lowest.
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  Influences of Physical Activation on Properties of Pozzolanic Tuff

  LI Yang, LI Ming-xia, LI Jia-zheng, SHI Yan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 173-177. https://doi.org/10.11988/ckyyb.20211202

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  Pozzolanic tuff powder has a prospect to be used as a new mineral admixture in hydraulic concrete preparation in China's western areas. By using scanning electron microscopic (SEM), X-ray diffraction (XRD) analysis and X-ray fluorometric (XRF) analysis, the influences of grinding process on physical properties, chemical composition and mineral phase components of tuff powder were examined. The relations of activation index of tuff against grinding time and curing age were also investigated. Results manifest that the fineness of tuff powder reduces with the prolongation of grinding period, while density, loss of ignition (LOI) and the ratio of water demand all increase slightly. The grinding process is accompanied by mechanochemical action, which could exert physical activation effect on tuff powder, but has no effect on chemical composition, element distribution and mineral phase component. The activation index of tuff powder is in a notable logarithm relationship with grinding period and curing age. We recommend that tuff powder should be incorporated in concrete accompanied by some other mineral admixtures such as fly ash and slag.
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  Influences of Length and Content of Slag Fiber on Strength Characteristics of Cement Mortar

  CHAI Lin-jie, GAO Fan, WANG Yan

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 178-182. https://doi.org/10.11988/ckyyb.20211267

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  Cement mortar was reinforced by mixing with blast furnace slag fiber to enhance the mechanical properties of cement mortar materials and improve the utilization rate of mineral resources. The effects of the content and length of furnace slag fibers on the strength characteristics of reinforced mortar specimens were studied via unconfined compression tests. The results manifest that with the increase of slag fiber content, the unconfined strength of cemental mortar improves; but such improvement attenuates notably when the slag fiber content exceeds 0.3%. Furthermore, slag fibers with lengths of 5 mm and 10 mm were mixed for comparison. Given the same fiber content, long fiber generates a strengthening effect 1.3-1.5 times that of short fiber. Microscopic morphology observation demonstrates that the addition of furnace slag fibers to cement mortar can improve the adhesion between particles, forming a “bridging effect”, thus finally enhancing the strength and toughness of cement mortar.
Informatization of Water Conservancy
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  Design and Development of Biaxial Inclinometer System Based on CAN Bus

  ZHANG Feng, PENG Si-wei, DU Ze-dong

  Journal of Changjiang River Scientific Research Institute. 2023, 40(5): 183-190. https://doi.org/10.11988/ckyyb.20211206

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  Traditional RS-485 bus inclinometers have reached their limits in handling modern displacement monitoring issues which require faster communication speed and longer communication distance. To improve the communication performance of traditional inclinometers, a fully functional biaxial inclinometer system based on the CAN (Controller Area Network) bus has been developed in this study. The whole system has functions of data measurement, data collection, communication, data processing, man-machine interaction, and early warning. This study has managed to fix the mounting error problem that many other studies ignored as well by applying bivariate quadratic regression. The final experimental results indicate a total error less than 0.2%F.S.