01 May 2022, Volume 39 Issue 5

    

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  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 0-0.

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SPECIAL CONTRIBUTION
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  Review on Research Progress of Hydraulic Concrete Materials

  LI Jia-zheng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 1-9. https://doi.org/10.11988/ckyyb.20210637

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  The research achievements and innovations in concrete materials for water conservancy and hydropower projects in the past seven decades made by the Material and Structure Department of Changjiang (Yangtze) River Scientific Research Institute (CRSRI) were summarized in this paper. The department has been promoting hydraulic concrete raw materials towards a diversified, functionalized, and geo-oriented development with low carbon, and has been leading the transformation of dam concrete performance design from being strength-dominated to durability-oriented. The team of hydraulic construction materials in CRSRI has provided advanced design of mix ratio of hydraulic concrete for many large and medium-sized water conservancy and hydropower projects in China and abroad, solved many engineering problems in crack control, durability improvement and high performance of hydraulic concrete, and accumulated rich achievements and experiences to enhance hydraulic concrete technology. In future, we will continue to focus on the demand for new materials, new technologies, and new techniques in the development of new energy, and help achieve the national strategy of carbon peaking and carbon neutrality.
COMPREHENSIVE MANAGEMENT OF RIVER BASIN
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  Measures of Joint Management and Protection for Boundary-sharing Rivers and Lakes under the River and Lake Chief System: A Case Study on Taihu Lake Basin

  LUO Ping-an, LUO Bu, SHA Zhi-gui, TANG Jian

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 10-14. https://doi.org/10.11988/ckyyb.20210121

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  By means of literature review, field investigation, discussion and communication, we made a review on the eco-environment status and management situation of Taihu Lake Basin and summarized the experiences and deficiencies in the joint management and protection of the Taihu Lake Basin. On this basis, we put forward some policy measures to strengthen the joint management and protection in the following aspects: promoting the legislation of basin management, issuing guidance on joint management and protection, unifying plans and standards, strengthening cooperative work, adapting to the carrying capacity of water resources, green development, etc. We hope it will be helpful to improve the integrated management of boundary-sharing basin and the implementation of river and lake chief system for Taihu Lake Basin.
RIVER LAKE PROTECTION AND REGULATION
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  Numerical Study on the Influence of Riverbed Median Particle Size on Scour Pit Evolution Process around Bridge Pier

  GAO Hu, WANG Qiu-sheng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 15-21. https://doi.org/10.11988/ckyyb.20210131

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  The change in riverbed morphology and the reduction of bridge pier foundation's buried depth resulted from local scour around the pier are major causes of bridge failure. An all-time and all-round 3D numerical simulation on the flow scour around the foundation of bridge pier is carried out by using LES (Large Eddy Simulation) in association with the equation of flow motion and the theory of sediment dynamics. The streamlines of eddy flow around the bridge pier foundation and the contours of riverbed elevation were acquired. The effects of flow velocity and median particle size on local scour around bridge pier were examined. The numerical simulation results suggest that the depth of the scour pit increases with the increase of the initial flow velocity and the formation of scour pit accelerates in the meantime. Scour pit depth also extends with the reduction of riverbed's median particle size; but when the median particle size is small to a certain extent, the depth of scour pit shrinks because of the increasing of cohesion between sediment particles.
WATER RESOURCES
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  Factors Affecting the Benefit of Danjiangkou Reservoir Utilization

  ZUO Jian, LIN Yun-fa, DENG Shan, LIAN Lei-lei, WANG Xian-zheng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 22-27. https://doi.org/10.11988/ckyyb.20210065

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  As the water source of the middle route of South-to-North Water Transfer Project, Danjiangkou Reservoir boasts an ever-increasingly prominent function of water supply and other benefits after the dam was heightened. Nevertheless, the decline in rainfall and the regulation and storage of cascade reservoirs in the upper reaches of Hanjiang River have greatly reduced the transferable water resources of Danjiangkou Reservoir. In order to give full play to the benefit of the reservoir, we calculated and analyzed the influences of the starting and regulating water level, the uncertainty of incoming water and the limited water level of flood season on the benefit of Danjiangkou Reservoir from three aspects: water supply satisfaction rate, average annual electricity generation and average annual waste water level. Results manifested that 1) water level at the incipience of regulation has a great influence on the water supply benefit in dry year when the frequency of incoming water is more than 90%. When water level is raised from 150 m to 160 m, the rate of meeting water supply demand can be increased from 44.38% to 93.42%. When the frequency of incoming water is less than 75.7%, water level mainly affects power generation. The higher the water level at the incipience of regulation is, the higher the annual power generation is, and the smaller the annual waste water is. When water level is raised from 150 m to 170 m, power generation could increase by at least 1 billion kW·h. 2) The higher the frequency of incoming water, the smaller the rate of meeting water supply demand, and the lower the average annual power generation. When incoming water is abundant, water abandon and water supply shortage both exist in the mean time. 3) The influence of flood limit water level in summer on the benefit of Danjiangkou Reservoir is more significant than that of flood limit water level in autumn; in a three-year regulation period with at least two years of low water, flood limited water level exerts a most obvious influence on abandoned water quantity. 4) Water level at the incipience of regulation is the major factor that affects the operation benefit of the reservoir. Except from continuous dry years, the water supply demand of different level years can be met if the water level at the incipience of regulation is 162 m.
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  Temporal and Spatial Evolution of Precipitation in the Headwaters of the Yangtze River

  CAI Yi-qing, LI Wen-hui, Yu Ze-xing, LI Qi-jiang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 28-35. https://doi.org/10.11988/ckyyb.20210013

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  Based on the daily statistical data of eight stations in the source area of the Yangtze River from 1956 to 2016, we examined the spatial distribution, intra-annual and inter-annual trends, abrupt change and periods of precipitation in the headwaters of the Yangtze River in the last six decades by using precipitation concentration degree, precipitation concentration period, Mann-Kendall trend test and moving-T test. Results revealed that: 1) the precipitation in the headwaters of the Yangtze River presented an evident increasing trend, passing the significance test with the growth rate amounting to 10.2 mm/10 a and the multi-year average precipitation reaching 344.8 mm. 2) Precipitation in the headwaters of the Yangtze River was significantly uneven in time dimension, most concentrated between June and September, accounting for 81.1% of the whole year. 3) Precipitation changed abruptly in 1997, with the first principal period of 25 years, the second and the third principal period of 3 years and 10 years, respectively. 4) The annual precipitation growth varied largely in spatial scale among different stations, i.e., the growth rate of precipitation in the upstream of Tongtian River was larger than that in the downstream. The research findings offer support for sustainable water resources utilization and ecological security in the Yangtze River basin.
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  Temporal and Spatial Variation of Water Vapor Transport over the Main Water-receiving Area of Water Diversion Project in Central Yunnan Province

  HE Shi-hua, LAI Yi-zhou, YE Feng-yan, SHEN Chun-ying, PAN Feng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 36-44. https://doi.org/10.11988/ckyyb.20210098

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  According to the ERA-Interim data, the 21-year water vapor transport flux and divergence over the main water-receiving area of the water diversion project in central Yunnan Province were calculated. The spatial-temporal characteristics of water vapor transport, convergence and divergence in the studied area were also analyzed. Results demonstrate that the annual average water vapor transport in the studied area gradually increases from the northwest to the southeast, and is dominated by latitudinal transport. The source of water vapor moves with the seasons and is controlled by southwest wind in summer. The intensity of water vapor transport in the studied area in summer is significantly lower than that in the other three seasons. From May to July, the intensity of water vapor transport shows a gradual decline. In July, a water vapor convergence center emerges in the south of the studied area on the 850 hPa barosphere and a water vapor divergent zone in the southwest on the 450 hPa barosphere, beneficial for the formation of precipitation in the southwest.
SOIL AND WATER CONSERVATION AND ECOLOGICAL RESTORATION
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  Evolution and Driving Forces Analysis of Wetland Landscape Pattern around Chaohu Lake from 1975 to 2020

  ZHAO Qiu-yu, JIANG Peng, ZHU Zhi-qiang, WU Yan-lan

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 45-53. https://doi.org/10.11988/ckyyb.20210199

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  The changes of wetland landscape pattern around Chaohu Lake was examined to reveal the evolution characteristics and driving factors of the study area based on the remote sensing data during 1975-2020. The object-oriented classification method based on sample is adopted in association with high-resolution image to correct the wrong classification. The characteristics and dynamic changes of landscape pattern were analyzed by calculating land use transition matrix, dynamic degree and landscape pattern index; the driving forces of the changes were discussed through principal component analysis. Results unveiled that: 1) the area of wetland around Chaohu Lake presented a declining trend in general, from 971.77 km² to 905.29 km² in 1975-2020, most of which is converted into construction land, agricultural land and vegetation land; the area of constructed wetland expanded to 39.58 km² during 2013-2020, mainly converted from agricultural land; among non-wetland landscapes, the area of construction land expanded the most rapidly, from 13.85 km² to 566.56 km². 2) In the analysis of landscape index, the number of patches increased, and the fluctuation of different types of patch index varied; on the whole, the landscape fragmentation index climbed from 0.49 to 1.26, indicating a more heterogeneous and complex landscape; the diversity index displayed a slow growth trend and tended towards a balanced distribution. 3) According to driving force analysis, natural factors played a significant role in the early stage of landscape evolution; with the development of social economy, the effect of natural factors is gradually weakened and social economy became an important driving factor; policy factor played a guiding role in regional landscape evolution by changing the distribution of landscape types via policy regulation.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  Calibration and Statistics of Characteristic Parameters of Water Level Process lines in Front of Three Gorges Dam

  HE Jin-wen, SUN Jun-jian, CHENG Jun

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 54-62. https://doi.org/10.11988/ckyyb.20210129

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  Periodic change of water level in Three Gorges Reservoir is a crucial random variable that affects the deformation and stability of bank slope in the reservoir area. The marginal distribution type, distribution parameters and correlation coefficient of characteristic parameters are obtained by calibrating the water level process lines(WPL) of Three Gorges ranged from 2010 to 2020. Firstly, WPL is fitted with nine straight lines and fourteen parameters inclusive of the duration and rising or falling speed in rising and falling period, the duration of two platforms before and after the main flood period, the climbing and falling durations of flood peak, and the peak water level. AIC (Akaike Information Criterion, AIC) method is used to identify the optimum distribution of characteristic parameters, and statistical uncertainty is simulated by using Bootstrap method. Results show that the WPL formed by average characteristic parameters calibrated from 11-year WPL can effectively avoid the peak elimination and valley filling, and can be taken as typical WPL for deformation and stability prediction of landslides in the reservoir area. The durations of the slow-descent stage and steep-descent stage of decline period and the steep-rising stage and slow-rising stage of the rising period obey Weibull distribution, the extreme value I-type distribution, the lognormal distribution, and the Weibull distribution, respectively, with the mean values being respectively 87.00, 47.45, 22.18, and 32.27 days. The falling or rising speeds of reservoir water in the four stages obey extreme value I-type distribution, Weibull distribution, extreme value I-type distribution, and extreme value I-type distribution, respectively, with the mean values being 14.53 cm/d, 36.75 cm/d, 74.33 cm/d, and 37.88 cm/d, respectively. The Pearson coefficient of correlation between duration and reservoir water level change rate in the four stages are -0.67, -0.78, -0.85, and -0.67. The flood peak level in flood season obeys the extreme value I-type distribution and the mean coefficient of correlation between slow-descent duration and the speed varies largely. The research findings offer random statistical parameters of WPL for risk analysis of landslides in the Three Gorges reservoir area.
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  Mapping the Susceptibility of Lushan Seismic Landslide Based on Multimodal Classification Model

  LI Qi-rong, MIAO Ze-lang, CHEN Shuai, LI Ke, PU Ming-hui

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 63-70. https://doi.org/10.11988/ckyyb.20210074

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  To improve the accuracy of assessing seismic landslide susceptibility, we proposed a landslide susceptibility assessment model from the perspective of multimodal data fusion. With the Lushan earthquake as a case study, we extracted fifteen causative factors of landslide from multi-source data and divided them into four modalities. With the slope unit being the assessment unit, we compared and evaluated the present method and the logistic regression model by using receiver operating characteristic (ROC) curve and zonal landslide hazard point density. Results demonstrate that the area under the ROC curve is 0.86, and the hazard point density of high and very high susceptibility zones is 2.24 points/km², indicating that the present model is well applicable to the study region. Also, the present model has higher accuracy and better performance than the logistic regression model, suggesting that the presented model has a better applicability in the region.
AGRICULTURAL WATER CONSERVANCY
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  Optimizing Design of Pipe Network in Micro-irrigation System Using SVMs-GA

  LIU Ying, ZHENG Rong-wei, QI Yan-fang, CHEN Hong-cai

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 71-75. https://doi.org/10.11988/ckyyb.20210137

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  The aim of this research is to optimize the combination mode of pipe network in agricultural pipeline irrigation, improve irrigation efficiency and cut irrigation costs. Support vector machine (SVM) coupled with genetic algorithm (GA) was employed to optimize the model, and the optimal combination of the number of standard sections of branch pipes with different diameters that met the constraints and the objective function was obtained. The objective function was to minimize the cost per unit area of pipeline under the assumption of unlimited irrigation area; the decision variables were the number of standard sections of branch and capillary; the constraint conditions were the maximum allowable pressure difference of the system and the minimum number of pipes constituting the pipe network. Results showed that when capillary pipes were laid in both directions, the cost of pipes per unit area was the lowest, 8 755.7 yuan/hm², the irrigation area was 24.15 hm², and the water head difference of the pipe network reached 97.6%-99.7% allowed by the system. Compared with one-way laying, the cost of pipe per hectare of two-way laying was reduced by about 6.5%, and the irrigation area was increased by about 103%. Compared with the results in existing literature, the cost per hectare of pipeline decreased by 5%, and the irrigation area increased by 23%. In conclusion, support vector machine coupled with genetic algorithm can better optimize the design of pipe network, and provides a reference for agricultural water-saving irrigation.
HYDRAULICS
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  Near and Far Field Division of Landslide Surge and Analysis of Water Wave Characteristics

  ZHANG Shao-qiang, HUANG Xiao-yun, CHENG Yong-zhou, SHEN Bao-xing

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 76-82. https://doi.org/10.11988/ckyyb.20201283

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  As a secondary disaster with great harm, landslide surge poses great threats to people's life and property safety. In the aim of discovering hazards and taking preventive measures, the whole process of landslide surge wave was simulated numerically to explore the characteristics of surge waves in different fields. A numerical model of landslide surge wave was established by CFD Flow-3D. The accuracy and effectiveness of the model were verified by classical landslide surge wave test. The height of the first wave simulated by the numerical simulation was in good agreement with the result of physical model test, implying that the numerical simulation could reflect the whole process of landslide surge wave propagation. Based on the numerical model, 27 groups of numerical simulation tests on landslide density, landslide volume and initial water entry characteristics were developed. Results revealed a negative correlation between the rebound of the near field surge wave and the occurrence time of the first wave trough and the density of the landslide. The first potential energy of the near field surge wave accounts for about 70% of the whole surge potential energy. The period of the far field surge wave is about two times of the underwater movement time of the landslide body. According to the surge potential energy, the initial position of the far field surge wave is 22 meters away from the water entry point of the landslide under certain conditions. The research findings are of referential value for the early warning and prevention of landslide surge disaster in practice.
ROCK SOIL ENGINEERING
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  Effect of Herb Plant Root System on the Reinforcement of Opencast Mine Dump

  LIU Xiang-feng, HAO Guo-liang, YU Bing

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 83-88. https://doi.org/10.11988/ckyyb.20210095

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  The aim of this study is to investigate the reinforcement effect of herbaceous plants in opencast mine dump area. Three locally grown herbaceous plants, Poa annua L., Suaeda glauca Gunge, and Digitaria sanguinalis Scop. are selected as research objects. Through tensile strength test and in-situ shear test on plant roots as well as Wu-Waldron model (WWM) calculations, the correction factor of WWM model is determined, and then the corrected WWM model is used to quantify the root cohesion of herb plants in the dump site in association with the geometric distribution characteristics of roots on soil profiles at different depths. Results demonstrate that the tensile strength of the three herbaceous plants has a power-law function relationship with root diameter, decreasing nonlinearly with the increase of diameter. Significant (p<0.05) differences are found in the tensile strength of the three herbaceous plants. In comparison, the root-soil composite reinforced by Digitaria sanguinalis Scop. provides larger shear resistance, and also greater stability after peak shear force. WWM model overestimates the reinforcement effect of plant roots, and the degree of overestimation varies with species. Moreover, the WWM model for the three herbaceous plants are modified, and the correction factors are 0.58, 0.27 and 0.88, respectively. Both the root area ratio and root cohesion of the three herbaceous plants decrease with the increase of soil depth. Digitaria sanguinalis Scop. has the best reinforcement effect in the local area.
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  Mechanical Response and Energy Evolution Law of Coal-Rock Combined Specimen under Cyclic Loading and Unloading Conditions

  XU Jin-hai, ZHANG Xiao-wu, LIU Zhi-bing, SUN Lei, HOU Sheng-jun

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 89-94. https://doi.org/10.11988/ckyyb.20210110

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  Uniaxial cyclic loading and unloading experiments on pure coal, coal-rock assembly and pure rock specimens were designed and conducted to study the mechanical response and energy evolution law of coal-rock assembly under external load. The mechanical response characteristics such as uniaxial compressive strength and elastic modulus of test specimens were analyzed, and the evolution law of input energy density, elastic energy density and dissipated energy density of coal-rock assembly were examined in detail. The characteristics of elastic energy storage rate and energy storage capacity of different specimens were obtained, and the energy failure mechanism of coal-rock assembly were discussed. Results demonstrate that: 1) The mechanical parameters of coal-rock combined specimens are closer to those of pure coal specimens, mainly affected by the coal. 2) With the rise of external load, the input energy, elastic energy and dissipated energy of coal-rock combined specimen present obvious non-linear increase trends, in which the proportion of elastic energy is much higher than that of dissipated energy. 3) Under external load, elastic energy is stored in coal and rock masses synchronously; but as elastic energy reaches the storage limit in coal earlier than that in rock, the coal mass breaks and releases elastic energy to the rock mass. When the storage limit in rock mass is reached, failure of rock mass occurs.
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  Experimental Study on Strength Deterioration Law of Cement Soil Mixed with Iron Ore Tailings under Wetting-Drying Cycles

  HU Jian-lin, GAO Peng-fei, CUI Hong-huan, ZHANG Yu-long

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 95-98. https://doi.org/10.11988/ckyyb.20210294

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  In order to explore the mechanical properties and anti-deterioration ability of iron tailings cement soil, we conducted unconfined compressive strength test and wetting-drying cycle test to examine the influences of cement content, iron tailing sand content and number of drying and wetting cycles on the strength of iron tailings cement soil. Results demonstrated that a dosage of 20% iron tailing sand had a largest improvement effect on the strength of cement soil, improving by about 70%; a dosage of 40% iron tailing sand had a least enhancement effect. Dry-wet cycles had deterioration effects of varied levels on the strengths of plain cement soil and iron tailings cement soil: the strength loss of plain soil-cement was greater at the initial stage of cycle than that in the later stage and tended to be gentle gradually, while the strength loss of iron tailings cement-soil was small at the initial stage of cycle, and the strength deteriorated obviously after a certain number of cycles. The main reason for the deterioration of cement-soil strength is the stress concentration caused by the drying shrinkage and wetting swelling of pores.
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  Mechanism of Using Electroosmosis and Different Chemical Solutions to Reinforce Mucky Clay

  ZHAO Hong-xing

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 99-105. https://doi.org/10.11988/ckyyb.20210567

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  A one-dimensional laboratory test program is performed to investigate the strengthening effect of electroosmosis incorporated anolyte on mucky clay. By comparing the differences in electroosmotic current, drainage, shear strength and microstructure of soil, the mechanism of various anolyte accelerating the electroosmotic dewatering is further revealed. The testing results show that the injection of chemical solution facilitates the electrochemical drainage. Cations with lower atomic weight and valence have more significant effect: Na⁺>Ca²⁺>Al³⁺. The Ca²⁺ and Al³⁺ cations migrated to cathodic region react with hydroxyl ion to produce cementing agent, which enhances the cohesion between soil particles and improves soil's shear strength. Ca²⁺ has the strongest improvement effect by enhancing the shear strength of the cathodic soil by as much as 350%. Moreover, the injection of chemical solutions will also accelerate electrode corrosion and induce larger variation of pH value.
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  Experimental Study on Expansive Soil Improvement by Calcium Bicarbonate from Pseudo-Karstification

  QIU Wei-zhao, YANG Xiu-juan, TAO Ran, FAN Heng-hui, ZHAO Wen-he, LIU Hao, LIU Yi-fei

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 106-111. https://doi.org/10.11988/ckyyb.20210089

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  Lime and cement are widely used in engineering projects to modify the special engineering properties of expansive soil such as water swelling and dehydration shrinkage; but such traditional soil solidification materials are difficult to be well mixed, and also pollute the environment. The physical, mechanical, chemical and micro-structural properties of the typical strong expansive soil of Hanzhong stabilized by calcium bicarbonate from pseudo-karstification are studied by means of free swelling rate test, unloaded expansion rate test, shrinkage test, direct shear test, pH test, carbonic acid content determination test, particle size analysis test and scanning electron microscope test. Test results show that calcium bicarbonate from pseudo-karstification could reduce the swell-shrinking property of expensive soil and improve the soil's shear strength. The optimal mass ratio of calcium bicarbonate solution from pseudo-karstification to expansive soil is 6∶1. The content of exchangeable calcium ions, fine particles and interior pore decreased, while the content of calcium carbonate and coarse particles increased. The mechanism of solidifying expansive soil by calcium bicarbonate from pseudo-karstification can be explained as follows: given a large number of H⁺, Ca^{2 +}, HCO₃^-, CO₃² and excess carbon dioxide dissolved in solution, the Ca²⁺ adsorbed by soil particle are replaced by H⁺ through ion exchange reaction, hence reducing the thickness of electronic double layer. The newly formed calcium carbonate from karstification has effects of filling and reinforcing so that the connection between soil particles is enhanced and the swell-shrinking potential is reduced. In conclusion, calcium bicarbonate from pseudo-karstification has a good effect on reducing the swell-shrinking potential of expansive soil.
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  Compound Improvement of Replacement Fill for Cement-modified Expansive Soil Based on Vegetation Restoration

  CHEN Pin-zhang, YANG Hai-lang, HU Bo, LIU Jun, GONG Bi-wei

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 112-118. https://doi.org/10.11988/ckyyb.20210063

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  A multi-index and multi-factor orthogonal experiment was carried out to explore the influence of various factors and levels on the germination, growth and root distribution of bermudagrass planted in the surface cement-modified soil of expansive soil slope of the water diversion project from Yangtze River to Huaihe River. The orthogonal experiment was designed with five factors (peat content, water retention agent content, organic fertilizer content, PAM content, and degree of compaction) and four levels. The vegetation restoration effect was comprehensively evaluated by five indexes, namely, plant germination rate, growth height, coverage, root penetration depth, and root content. Results showed that the importance of the factors affecting plant growth was organic fertilizer content, degree of compaction, water retention agent, peat content, and PAM content in descending order. Content of fertilizer and peat has a good promoting effect on plant growth and soil improvement. The higher the soil compaction degree, the worse the plant growth; to ensure better plant growth, the compaction should not exceed 86%. For the expansive soil slopes of the Y003 segment of the water diversion project from Yangtze River to the Huaihe River, the optimal improvement plan for the growth of plant (bermudagrass) is: replacing the original surface expansive soil with cement-modified soil with 9% peat, 0.05% water retention agent, 1.5% organic fertilizer, 0.05%PAM, and compaction degree at 66%. The research finding is of guiding significance for the ecological restoration of cement-modified soil in the area of diversion project from the Yangtze River-to-Huaihe River. The analysis and evaluation methods can also be used as references for the ecological restoration of cement-modified soil in other regions.
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  Theoretical Analysis of Shear Strength of Deep-sea Energy Soil

  YU Hang, QI Cheng-zhi, ZHU Shou-dong, ZHAO Fa, WANG Xiao-jiao

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 119-124. https://doi.org/10.11988/ckyyb.20210037

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  The existence and decomposition of hydrates have two-sided effects on the shear strength of marine energy soil. To investigate the effect of hydrate on the strength of marine energy soil, an expression of the cohesion of marine energy soil is proposed in consideration of the type and occurrence mode of hydrate. As the presence of hydrates increases the contact area between soil particles, the concept of cemented area ratio is introduced to revise the expression of effective stress on account of the influence of hydrate via theoretical derivation. Based on the Mohr-Coulomb criterion, the relation of shear strength varying with hydrate saturation is obtained. In addition, the expression of pore pressure after hydrate decomposition is deduced considering the dissolution of methane gas. The rationality of the proposed expression is verified through triaxial shear test of sediments and numerical simulation of hydrate decomposition. The results conclude that the present expression well reflects the impacts of hydrate content, hydrate occurrence state, and high water-pressure on the strength of marine energy soil; meanwhile, the corrected pore pressure model is helpful to better analyze the stability of submarine slope.
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  Effectiveness and Mechanism of Improving Strength of Red Clay by Microorganism

  WANG Lian-rui, CHEN Jun, YANG Heng, HUANG Yang, HUANG Yang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 125-131. https://doi.org/10.11988/ckyyb.20210142

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  Strengthening red clay with microorganisms is an innovative, environmental friendly and economical method. We prepared two kinds of microorganism-strengthened soil samples according to the optimum curing condition by selecting bacillus pasteurii and iron bacteria to strengthen soil with activated carbon as carrier. Tests on the basic physical and mechanical properties of microbe soil samples unveiled that the density, shear strength and unconfined compressive strength of microbe soil samples increased whilst porosity decreased, indicating that microorganisms remarkably promoted the physical and mechanical properties of red clay. In order to further study the solidification mechanism, we examined the microstructure and material composition of the samples via scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). We found that bacillus pasteurii induced the formation of calcium carbonate to fill the pores of soil and form the cemented and solidified soil. Calcium carbonate is mostly concentrated in the vicinity of activated carbon and presents a massive structure; iron bacteria produce iron-based compound to fill the soil pores, and the iron-based compound is mostly lamellar or layered structure. In short, the curing effect of bacillus pasteurii for red clay is better than that of iron bacteria. The research finding is of vital reference value for understanding the mechanism of microbial reinforcement of red clay and the selection of bacterial species.
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  Experimental Study on Soil Reinforcement by Native Microbial Induced Calcite Precipitation

  ZHOU Yang, ZHANG Jia-ming, ZHU Ji-kang, YU Meng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 132-139. https://doi.org/10.11988/ckyyb.20210039

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  Laboratory consolidation test was carried out to study the influence factors of sand reinforcement by native microorganism. The native urease organisms in the soil were activated by using different injection methods with different concentrations of organic matters. After the urea hydrolysis ability reached the threshold value by the urease bacteria proliferated in the soil samples, the microbial species in the samples were identified and phylogenetic analysis was carried out, and then MICP cementaion treatment was performed. Biochemical changes in soil samples were monitored by cells density of urease bacteria and urea concentration. The reinforcement effects of soil samples were evaluated via unconfined compressive strength (UCS) and scanning electron microscope imaging (SEM). Results demonstrate that the reinforcement effect is strongly related to the way of injection and the concentrations of organic matter and urea. Bidirectional alternative grouting is beneficial to enhancing the uniformity of cementation. Biochemical analysis indicates that high concentration of organic matter (yeast extract) has adverse impact on the microbial diversity in soil, the activation of native urease bacteria in soil and the cementation effect. The residual concentration of urea in the sample with 0.35 mol/L urea was higher than that in the samples with 0.20 mol/L urea. In the present study, the soil column treated by 1.0 g/L yeast extract, 0.20 mol/L urea/calcium chloride solution and bidirectional injection achieved sound uniformity of cementation, with its carbonate crystals tightly connected and the UCS value reaching 1.55 MPa. The results conclude that the native microorganism in the soil can be activated effectively by a proper proportion of solution, hence strengthening the soil.
HYDRAULIC STRUCTURE AND MATERIAL
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  Long-term Effectiveness of Preventive Measures against Alkali- Aggregate Reaction of Jinping-I Dam Concrete

  DONG Yun, ZHOU Ze-cong, LI Peng-xiang, LIU Chang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 140-144. https://doi.org/10.11988/ckyyb.20210091

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  To address the problem of selecting aggregate sources for Jinping-I dam restricted by environmental and economic factors, alkali-active aggregate had been used in the dam concrete by restraining the alkali-aggregate reaction of sandstone through measures of combined aggregate, high dosage of fly ash, and strict control of alkali content. This was the first time that alkali-active aggregate was adopted to an ultra-high concrete arch dam. Now that the dam has been in operation for about 10 years, it is necessary to scientifically evaluate the effectiveness of the long-term prevention of alkali-aggregate reaction of dam concrete. Researches on the preventive measures against alkali-aggregate activity during dam construction were briefly reviewed and summarized, and then the long-term effectiveness of such preventive measures was examined via petrographic analysis, microscopic morphology and product analysis, accelerated curing length measurement and elastic wave test on dam concrete core samples that have been in operation for 10 years. Test results revealed no harmful alkali-aggregate reaction inside with sound quality of the concrete core sample, which verifies the long-term safety and effectiveness of the alkali-aggregate preventive measures adopted in the dam concrete of Jinping-I Hydropower Station.
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  Stability Analysis of Offshore Spar Floating Foundation Platform under Wind Wave Current Load Based on AQWA

  XU Xu, DING Gang, YAO Wen-juan

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 145-152. https://doi.org/10.11988/ckyyb.20210080

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  In view of the currently low utilization rate of renewable energy and to effectively use deep-sea wind energy, we probed into the stability of the foundation part of the designed OC3-Hywind 5MW Spar floating platform under wind, wave, and current loads. By simulating the coupled motion response of the structure in the frequency domain and time domain respectively using hydrodynamic module AQWA in ANSYS, we compared and analyzed the motion response extreme values of the floating foundation under various degrees of freedom in different working conditions, as well as the influence of counterweights at different positions of the mooring on the response value of structure motion and mooring tension. Results revealed that the extreme value of the motion response of the floating foundation platform in the direction of the pitch degree of freedom in different cases was mainly affected by wind load; as wind speed increased, the extreme value of the response also increased. The extreme value of response in other degrees of freedom was less affected by wind and wave loads. Changing the position of counterweights on the mooring line had a significant impact on the movement of the floating foundation platform in the pitch and yaw degrees of freedom; the closer the counterweight was to the anchoring point, the greater the response value was, which is not conducive to the stability of the foundation platform. The tension of the mooring system in the absence of counterweight was higher than that in the presence of counterweight; as the counterweight was farther from the anchoring point, the mooring force reduced, which ensured the survivability of the floating foundation platform under severe sea conditions.
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  Method of Comprehensive Supervision System for River and Lake Shoreline

  LAI Hang, ZOU Xian-yong, FAN Guang-wei, YANG Yue, TIAN Mao-chun

  Journal of Changjiang River Scientific Research Institute. 2022, 39(5): 153-158. https://doi.org/10.11988/ckyyb.20210210

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  The supervision of river and lake shorelines is important and complicated. At present, river and lake shoreline supervision is still mainly based on the use of one or two supervision methods in air, space and ground, resulting in inadequate efficiency of daily supervision and low level of overall supervision. A comprehensive supervision model that integrates remote sensing supervision, on-site supervision, and station supervision is proposed, and the key technologies to realize the comprehensive supervision are studied. On this basis, a smart supervision platform for river and lake shorelines is built. The application of the platform verifies that the platform can comprehensively incorporate air, space, and other supervision methods to improve daily supervision efficiency and supervision level for river and lake shoreline. The present research offers a feasible reference plan for the supervision of river and lake shorelines, and is of promotion and application value.