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01 May 2021, Volume 38 Issue 5
    

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    SPECIAL CONTRIBUTION
  • CHENG Zhan-lin, PAN Jia-jun
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 1-10. https://doi.org/10.11988/ckyyb.20201226
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    China ranks top in the world in the amount of high earth-rock dam. To ensure the construction and long-term operation safety of high earth and rockfill dams is a major demand posed by national economic and public security. We summarize the major research progresses in the field of earth-rock dam engineering made by the Yangtze River Scientific Research Institute in recent years. Such progresses include: the test method of gradation similarity theory of coarse-grained material based on equalling density with pressuremeter modulus, the series CT triaxial apparatus for quantitatively measuring fabric of coarse-grained material, a novel friction reduction method in which the contact between soil and loading plate is changed from holistic contact to distributed contact and sliding friction to rolling friction, as well as its corresponding friction reduction devices. Moreover, true triaxial apparatus with large scale, high pressure, micro-friction and rigid-flexible composite loading has been developed. The variation law of strength and deformation and the wetting and creep deformation mechanism of coarse-grained materials under real three-dimensional stress have been revealed. The K-K-G nonlinear dilatancy model with three parameters, the wetting model with six parameters, the creep model with nine parameters and the corresponding parameter determination method have been established. In addition, in line with the original idea of equivalent density method, a test method for indirectly determining the field density of deep overburden with over 100 meters by pressuremeter test has been proposed. The above research findings offer crucial scientific and technological supports for the construction of high earth-rock dams.
  • RIVER-LAKE SEDIMENTATION AND REGULATION
  • LÜ Qing-biao, YUE Hong-yan, ZHU Yong-hui, LI Ling-yun
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 11-16. https://doi.org/10.11988/ckyyb.20200252
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    The influence of water level change rate on riverbank collapse was examined via generalized model test and numerical simulation. Results demonstrated that water level fluctuation had significant impact on bank collapse. Particularly, in the stage of water level drawdown, the larger the dropping rate, the more evident the bank collapse. Stability calculation of bank slope revealed that the factor of stability augmented in the stage of water level rising, but once the water level reached a high value, the factor of stability declined at first and then maintained stable; in the stage of water level drawdown, the factor of stability reduced and was closely related to the dropping rate. The research finding offers theoretical basis for analyzing the evolution of bank slope stability under varying water level fluctuation rate and also for taking corresponding treatment measures.
  • WATER RESOURCES AND ENVIRONMENT
  • LIANG Xu, ZHU Li-rong, YE Chang-qing
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 17-24. https://doi.org/10.11988/ckyyb.20200246
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    Water security affects the healthy and sustainable development of regional social economy. Global climate change and human activities have put great pressure on water resources security. A system dynamics (SD) model involving water resources, water environment, and socio-economic systems was built to assess and predict the water resources vulnerability of Nandu River basin in 2010-2035, and the causes and mechanism of water resources vulnerability were expounded. The assessment index system and evaluation standard were constructed by using the analytic hierarchy process. Four scenarios, namely, conventional, technological innovation, economic priority, and comprehensive development scenarios were set in the model. Results unveiled that industrial water consumption, urban/rural water consumption, and GDP growth rate were positively related to water resources vulnerability, while sewage treatment rate and the tertiary industry/industrial ratio were negatively related to water resources vulnerability. The water resources in all the four scenarios went through three stages: moderately vulnerable, slightly vulnerable, and not vulnerable, displaying a downward trend in vulnerability. Such downward amplitude in scenario 4 was the largest, followed by scenarios 2, 1 and 3 in sequence. The overall vulnerability was the largest in scenario 3, with an average of 43.81, and the smallest in scenario 4, averaging 33.48. In conclusion, scenario 4, namely, the comprehensive development mode is the most suitable for the healthy development of Nandu River Basin.
  • CHEN Liang, YANG Yin-ke, LIU Yu, WANG Tian-yao, JIAO Yi-wen
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 25-33. https://doi.org/10.11988/ckyyb.20200843
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    Distinguishing the characteristics of regional water utilization structure is of great importance for optimizing the allocation of regional water resources and the coordinated development of social economy and ecological environment. The Lorentz curve, Gini coefficient, Lorentz asymmetry coefficient and other methods are used to quantitatively analyze the temporal and spatial distribution characteristics, equilibrium differences, and major water consumption indicators. The major water consumption indicators include 10 000 Yuan GDP water consumption, 10 000 Yuan industrial value-added water consumption, per capita comprehensive water consumption and net irrigation water consumption. Results unveil significant differences in the structure of water utilization in Gansu Province. The Gini coefficient of industrial water use, urban public water use, and domestic water consumption are all greater than 40%, exceeding the “warning line”. The ecological environmental water use and agricultural water use are relatively reasonably distributed; but have not yet reached the goal of “spatial balance” for water control. Industrial water use, urban public water use, and domestic water use are evidently unevenly distributed in spatial scale, and generally presents asymmetric characteristics dominated by areas with larger types of water consumption. The research results are basically consistent with the actual situation, which indicates that the research ideas and methods can be taken as reference for the optimization of regional water resources allocation and the analysis of water utilization.
  • SUN Zheng-lan, SI Cun-you, HUA Jun, WANG Jiang
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 34-39. https://doi.org/10.11988/ckyyb.20200156
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    According to measured daily data of Sanjiangying station which is located at the outlet of Jiangdu water conservancy project, we analyzed the long-range change rules of typical elements such as characteristic tide level, tidal range, tide duration, and period in 1957-2019 as well as their impacts on the project operation by means of Mann-Kendall trend test, cumulative anomaly and Morlet wavelet analysis. Results demonstrated that: 1) Tide level had been increasing significantly over years, maximum tidal range did not increase significantly, and the maximum duration of rising and falling tide did not reduce significantly, but the maximum tidal range and tide duration showed opposite trend to annual trend in summer and the same trend with annual trend in dry season. 2) The characteristic tide level, tidal range and tide duration all exhibited periodic changes, with the main cycles of characteristic tide level and maximum tidal range reaching about 28 years and the main cycles of maximum rising and falling tide about 22 years. 3) According to the characteristic time length of the main cycles, the characteristic tide level, tidal range and tide duration are currently in an increasing stage and will in 2020-2021 enter a decreasing period of about 7-9 years. This study is of practical significance for the sourcing of the East Route of the South-to-North Water Diversion and the safe discharge of the Huaihe River flood. It also provides a reference for better mastering the law of tidal current movement at the end of the tidal boundary of the Yangtze River Estuary.
  • WATER-SOIL CONSERVATION AND ECOLOGICAL RESTORATION
  • SONG Li-wang, DENG Jian, WANG Wei-min, QI De-hui
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 40-46. https://doi.org/10.11988/ckyyb.20200285
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    In the purpose of providing theoretical support for the eco-environment construction and soil-water loss prevention in Zhejiang Province, we estimated the vegetation coverage of Zhejiang Province in 2009-2018 using an improved dimidiate pixel model based on monthly NDVI values obtained from using MVC maximum synthesis method according to MODIS_NDVI data in 2009-2018. Moreover, in line with DEM data and the division of forest land in the Plan for the Protection and Utilization of Forest Land in Zhejiang Province (2010-2020), we probed into the spatial-temporal changes in the vegetation coverage of Zhejiang Province. Results unveiled that: 1) From 2009 to 2018, Zhejiang Province featured an overall high vegetation coverage, with a slow downward trend. 2) The spatial pattern of vegetation coverage in 2018 differed little with that in 2009. Vegetation coverage in south and west mountainous and hilly area was the highest, followed by that in central Zhejiang hilly basin area, east Zhejiang coastal hilly island area, and northern Zhejiang plain area in sequence. Areas with stable vegetation coverage accounted for 62.79% of the total area; the area of vegetation degradation was larger than the area of improvement. Vegetation degradation was most serious in the northern Zhejiang plain area, accounting for 6.73% of the total area. In particular, the south Zhejiang mountain area witnessed the most notable improvement of vegetation coverage, occupying 4.87% of the total area. 3) The change of vegetation coverage with geographical factors was relatively stable; within different elevation ranges, areas with obvious degradation were below 100 m, and obvious improvement above 200 m; within different slope ranges, areas with evident degradation were between 0° and 5°, and apparent improvement above 15°; vegetation coverage changed slightly with slope gradient.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • MA Jia-jia, SU Huai-zhi, WANG Ying-hui
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 47-54. https://doi.org/10.11988/ckyyb.20200705
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    Under the combined action of water pressure, temperature and aging, dam deformation monitoring data series is non-stationary and nonlinear. We introduced the method of Ensemble Empirical Mode Decomposition (EEMD) to process deformation data and obtained the multi-scale dam deformation components. For the complex high frequency components, we employed the Long and Short Term Memory network (LSTM) to achieve better prediction results; for low frequency components with periodic changes, we adopted Multiple Linear Regression (MLR) for rapid and effective prediction. Through the refactoring of components we can acquire the predicted result of dam deformation. Analysis of engineering examples demonstrated that the EEMD method avoided modal aliasing and attained more reasonable multi-scale deformation components. LSTM and MLR have good predictive ability for high and low frequency components respectively. By comparing the result of components superposition separately with those of a variety of single prediction algorithms, EMD decomposition algorithm, and traditional models, we found that the Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE) and the Root Mean Square Error (RMSE) of the EEMD-LSTM-MLR combinatorial model were lower than the comparative models above, indicating higher prediction precision.
  • LI Dong-ming, DU Wei-qiong, WU Xin-fang
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 55-60. https://doi.org/10.11988/ckyyb.20200204
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    To assess the safety of penstock in a small power station where some segments of penstock are defective with incomplete longitudinal weld, we built the finite element model of the penstock segment which contains such defects using ANSYS Workbench to solve the circumferential stress of penstock wall, and to determine the critical stress intensity factor of 16Mn steel. Furthermore, we built the finite element meshes of fractures in accordance with the weld’s defect characteristics and calculated the type I stress intensity factor at the tip of defect. Finally, according to the criterion of critical stress intensity factor, we concluded that the weld defects had no impact on the penstock safety, and did not expand in subsequent inspections.
  • HYDRAULICS
  • GU Jin-de, XU Jian-rong, PENG Yu, XUE Yang, ZHAO Jian-jun, YAN Zhi-qing
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 61-65. https://doi.org/10.11988/ckyyb.20200220
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    Featured with narrow river valley and large discharge, Baihetan hydropower project is faced with prominent problem of flood discharge energy dissipation. Three groups of asymmetrical surface spillway were adopted to prevent from the overlapping of discharge flow in the limited space. Model tests have shown that in original design scheme, even though the discharge flow disperse effectively with surface or deep hole discharge, the dynamic impact pressure in plunge pool with surface and deep hole combined discharge still exceeds conventional standard, which may affect the safe operation of the plunge pool. In view of this, according to the characteristics of collision of flows from surface spillway and deep orifice, we adjusted the depression angle of the surface spillway to improve the collision effect of water tongues, and meanwhile adjusted the plane deflection angle of the deep orifice to improve the dynamic impact pressure distribution in the plunge pool with high power discharge. The optimized asymmetric arrangement is effective in energy dissipation while ensuring the safe operation of the plunge pool.
  • YU Si-han, HUANG Wei, HAN Ji-bin, HUANG Ming-hai
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 66-74. https://doi.org/10.11988/ckyyb.20200193
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    Selective withdrawal is widely implemented to moderate the effect of thermal stratification in large reservoirs and to solve the problem caused by the changes of hydrodynamic and thermal characteristics after the construction of dam. An experimental study was conducted to investigate the temperature and flow fields in front of the temperature-control curtain (TCC) set in thermal structure for selective withdrawal. Impacts of hot-cold water flow ratio, distance from the curtain to water intake, water intake position and water retaining proportion were systematically investigated in the experiments. Outflow temperature was also measured. The results indicated that thermocline thickness upstream side of TCC decreased while thermocline intensified, thus inhibiting water mixing. The thermocline thickness increased obviously, and the vertical diffusion of water was promoted downstream of TCC. When hot-cold water flow ratio, height of water intake and water retaining proportion reduced, the thickness of thermocline increased while the intensity of thermocline attenuated. In addition, the outflow temperature climbed with the augments of hot-cold water flow ratio, position of water intake and water retaining proportion.
  • ROCK-SOIL ENGINEERING
  • SHI Ming-sheng, LI Lu-lu, XIA Yang-yang, CHEN Yong-li
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 75-81. https://doi.org/10.11988/ckyyb.20200077
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    The polymer grouting bag pile is a new type of foundation reinforcement technology developed for the foundation reinforcement of existing buildings. In order to explore the applicability of polymer grouting bag pile to the foundation reinforcement of existing buildings, we investigated into the construction technology, law of pile formation and reinforcement effect of polymer grouting bag pile through the experiment of grouting pile in soil with different densities and layering conditions. The experimental results demonstrated that polymer bag pile has obvious effect on compacting soil mass. After piling, the pile diameter can reach 2D-3D (D represents the diameter of drilling hole). In the presence of the same grouting quantity, the pile diameter shrinked with the increase of soil density, while the pile density expanded with the increase of soil density. Meanwhile, polymer grouting bag pile can also pass through the hard interlayer to form a gourd-shaped body and plays a better role in strengthening the soft soil foundation. The results of field light dynamic penetration test showed that the hammer stroke of light dynamic penetration test increased by 2-3 times in the soil reinforced by polymer grouting pile, an improvement of 30%-50%. Therefore, polymer grouting bag pile has good reinforcement effect and is feasible for strengthening weak foundation.
  • LIANG Rui, BAO Juan, ZHOU Wen-hai
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 82-87. https://doi.org/10.11988/ckyyb.20200335
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    To study the damage characteristics of blast hole and the adjacent area of potential sliding surface of slope under blasting load, we determined the reduction sliding surfaces of slope under static load by FEM strength reduction method and thus established an elastoplastic constitutive model of slope for numerical simulation. By comparing the numerical simulation results with classical criteria, we determined the blast center distance and rock fragmentation status corresponding to different damage velocity thresholds, and further investigated the relations between damage, blast center distance, peak particle velocity (vPP), and dynamic tensile strength of rock during the blasting of rock mass on the potential sliding surface. In line with the classical vPP criterion, the vPP criterion of maximum tensile stress, and the statistical relation between peak tensile stress and vPP, we acquired three vPP thresholds and found that the error obtained by the criterion of maximum tensile stress was the largest. The research findings can be used to modify existing vPP criteria based on the maximum tensile stress criterion in actual engineering.
  • WANG Jia-hui, JIANG Ji-wei, RAO Xi-bao, HUANG Shuai, ZHOU Xin-hua
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 88-93. https://doi.org/10.11988/ckyyb.20200279
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    Four groups of large-scale triaxial consolidated-drained shear test were carried out on two types of incompact coarse-grained soil samples taken from the top and bottom of slope at a slag field. The relations of stress and strain, volumetric strain and axial strain, measured Poisson’s ratio against stress level, as well as the applicability of Duncan-Chang E-ν and E-B models were examined. Research results demonstrated that: 1) the stress-strain curve of the incompact coarse-grained soil displayed hardening features with no significant peak. Strength parameter φ was closely related to and augmented along with the increase of reference strain. 2) The incompact coarse-grained soil showed monotonous shear shrinkage in the whole process of shearing, which indicated that the structural compression caused by translational motion of particles dominated the whole process, while the particle rotation and force chain adjustment were negligible. 3) The measured Poisson’s ratio was in a linear relation with stress level, yet with an evident difference between top and bottom materials of slope. In addition, the Duncan-Chang E-B model had a good fitting result for the Poisson’s ratio of slope top materials, while the Duncan-Chang E-ν model was more applicable for slope bottom materials.
  • JIANG Jing-shan, ZUO Yong-zhen, CHENG Zhan-lin, PAN Jia-jun, ZHANG Chao, WEI You-xin
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 94-102. https://doi.org/10.11988/ckyyb.20200194
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    The mechanical properties of coarse granular material are not only depending on effective confining pressure, but also closely related to compaction degree. The effects of confining pressure and density on mechanical properties of coarse granular material under critical state were investigated using large-scale triaxial consolidation and drainage shear tests on specimens with four different initial dry densities. The deviatoric stress at failure state for softening stress-strain curve is larger than that at phase transformation state which is closer to the deviatoric stress at critical state. The stress ratio of deviatoric stress to mean normal stress gradually approaches the stress ratio at critical state. The curve of stress ratio for softening stress-strain test displays a single hump shape, while the curve of stress ratio for hardening stress-strain test shows a climbing shape. The critical void ratio decreases with the increase of mean normal stress under critical state, and basically increases linearly with the increase of initial void ratio.
  • YU Meng, ZHANG Jia-ming, ZHOU Yang, SUN Kuang-biao
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 103-108. https://doi.org/10.11988/ckyyb.20200096
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    Microbial induced calcium carbonate precipitation is a new kind of environmental-friendly soil reinforcement technology. Through laboratory MICP grouting test of expansive soil modification using Sporosarcina pasteurii, we investigated into the influences of cementing fluid concentration on the mechanical properties, microstructure and hydraulic characteristics of expansive soil. Moreover, we also revealed the mechanism and effect of modifying expansive soil by MICP technology. Test results demonstrate that MICP is effective in modifying expansive soil. After grouting, the unconfined compressive strength of soil samples increased by 379.4% at most, and the stiffness of soil was also improved. The expansibility and permeability of the samples reduced by up to 25.3 kPa and by three orders of magnitude, respectively. The modification effect ameliorated with the increase of cement concentration; but when the cement concentration reached a certain extent, the modification effect was no longer significant. The research findings verified the effectiveness and feasibility of MICP technology in modifying expansive soil.
  • LÜ Jie, FAN Xiu-feng, WU Zhen-xiang
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 109-114. https://doi.org/10.11988/ckyyb.20200147
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    Preferential channels such as large pores exist in actual slope soil where the water movement exhibits preferential flow characteristics. In this paper, we conducted a rain staining tracer test on undisturbed soil columns to investigate the development characteristics of large pores in natural slope soils and the spatial response rule of preferential flow under the action of rainfall. By calibrating the water infiltration area using staining information, we evaluated the influence of the development characteristics of different large pores inside the soil column on the development of preferential flow and water infiltration flux according to the parameter “water infiltration area ratio”. The research results revealed strong development and spatial variability of preferential channels in the undisturbed soil column. The preferential channel types are mainly large pores. To be specific, in large pores with good connectivity and opening degree, the preferential flow passes quickly, with weak exchanges with the surrounding matrix, hence replenishing groundwater quickly in large quantities; in large pores with irregular distribution and different directions, the preferential flow is weakened with strong exchange with matrix which yet gradually weakens with depth; in some dead-end large pores which retain more water, the water exchange with the surrounding matrix is enhanced, which is of little help to the migration of preferential flow. The results of the dyeing tracing evaluation are completely consistent with the laws obtained from the measured soil water fluxes of the soil column, which accurately reveals the typical spatial distribution characteristics of large pore flow in undisturbed soil.
  • FU Jia-jia, WANG Lian, YOU Su-nan, WANG Xu-dong
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 115-122. https://doi.org/10.11988/ckyyb.20200390
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    Clay-sand mixture is widely used in dredger fill. The deformation of mixed soil foundation is closely related to its microstructure. To explore the microscopic mechanism of compression deformation of mixed soils, we analyzed in qualitative and quantitative scales the particle arrangement and pore distribution of clay-sand mixture samples before and after consolidation via compression tests, scanning electron microscopy (SEM) tests and Image-Pro Plus (IPP) image processing. Results revealed that with the increase of sand content, the void ratio of mixed soil reduced at first and then grew, and the compressibility decreased gradually. The sensitivity of each pore group to consolidation pressure is closely related to sand content. With the increase of sand content, the number of large and medium pores increased, and the contact mode between particles transferred from edge-face and face-face contact to point-point and point-face contact. Compression enhanced the compactness and orderliness of particle arrangement. Pore size tended to be smaller. The percentage of large pore area dropped up to 31.39%, which resulted in the expansion of middle pores; however, the impact on micro-and-small pores is not obvious. The directional probability entropy of soil particle is linearly correlated with sand content, while negatively linearly correlated with compressibility coefficient a1-2. Lager sand content led to the more chaotic arrangement of mixed soil particles, larger directional probability entropy, and smaller compressibility. In conclusion, the change of microstructure parameters of particles and pores caused by different consolidation pressure and sand content ratio is the internal reason for the difference in the compression characteristics of mixed soil.
  • ZHANG Jie, ZHANG Chang-liang, LI Ping, LI Tong-lu, QIAO Zhi-tian, LI Qiang
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 123-130. https://doi.org/10.11988/ckyyb.20200506
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    The structure of loess is closely related to its formation process and has an important impact on its physical and mechanical properties. In view of the large pores and cementation features of structured loess, we embedded the clay cementation which plays a major role in structured loess into the existing DDA. By using Monte Carlo method and DDA, we simulated the deposition process of loess, in particular, the collision and friction of particles in the falling process and analyzed the translational and rotational movements of particles in the consolidation process. On this basis, we constructed a microstructural loess model which is close to undisturbed loess in terms of void ratio. Furthermore, we simulated one-dimensional compression test on the structured loess model under different pressures with the extended DDA, and compared with indoor compression test to demonstrate the reliability of the numerical simulation. We found that, despite similar overall trends, the particle displacement of cemented sample was smaller than that of non-cemented sample. Vertical displacement of particles dominated regardless of some differences in the degree and direction of displacements. Major differences existed in different parts, i.e., upper particles underwent larger displacement, while lower particles witnessed smaller displacement.
  • YAO Chen-hui, XIA Yu-yun, WU Xue-lin, LIU Yi, CHEN Tie-fei, MEN Qing-bo
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 131-136. https://doi.org/10.11988/ckyyb.20200202
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    The collapsibility characteristics of wind-blown sand in Thar Desert of Pakistan are investigated based on preliminary survey findings and collapsibility test results. The correlation between basic physical indexes of wind-blown sand and collapsibility are also examined. Results demonstrate that the collapsibility of wind-blown sand is mainly distributed in layer ① and layer ②, and the average collapsibility coefficient is 0.039, indicating slightly to moderately collapsible. The grain composition and soluble salt characteristics of wind-blown sand are the main internal basis of collapsible deformation. In addition, strong dispersion is found between collapsibility coefficient and water content of the wind-blown sand. Collapsibility coefficient is also positively correlated with porosity and linearly negatively with dry density. When porosity is smaller than 0.65 or dry density exceeds 1.60 g/cm3, wind-blown sand is not collapsible.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • LI Zong-kun, WANG Te, GE Wei, ZHENG Yan
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 137-143. https://doi.org/10.11988/ckyyb.20200137
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    There are many dynamic risk factors and uncertainties in the operation period of concrete dam. In this paper, a dynamic Bayesian network model is constructed to study the dynamic characteristics of dam breach probability by introducing time factors. In association with the Leaky Noisy-or gate extended model, the method of determining conditional probability is described. The time series curves of occurrence probability of dam breach against each risk factor are obtained for a practical project as a case study. The present model is proved to be prior to the static Bayesian network as the result is more rational. The research finding offers reference for the dynamic risk analysis and evaluation system construction of similar projects.
  • SHEN Heng-xiang, KONG Yun, PANG Jian-yong
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 144-148. https://doi.org/10.11988/ckyyb.20200071
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    In view of the insufficient mechanical properties of lightweight concrete, various fibers are added to lightweight concrete to improve its mechanical properties. The influences of adding ceramsite, basalt fiber, and polypropylene fiber on the compressive strength and maximum shear strength of concrete were investigated by using orthogonal test. Results reveal that replacing part of coarse aggregate with ceramsite could effectively reduce the dead weight of concrete, but also greatly reduce the compressive strength; ceramsite could improve the maximum shear strength of concrete, with a maximum rising rate of 13.7%. Both basalt fiber and polypropylene fiber could enhance the compressive strength and maximum shear strength of concrete, boosting the compressive strength by up to 9.7% and 5.7% respectively and maximum shear strength by 36.2% and 13.1% respectively. In addition, a prediction model for the compressive strength and maximum shear strength of hybrid fiber concrete is established.
  • INFORMATION TECHNOLOGY APPLICATION
  • LOU Lian-hui, LIU Qiang, TAN Yu-min
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 149-152. https://doi.org/10.11988/ckyyb.20201088
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    Assessing land surface deformation in the Three Gorges Reservoir area is of vital importance to the monitoring and prevention of geological disasters, the engineering construction and the safe operation of the reservoir. The map of annual average deformation rate in Badong was obtained based on 53 Sentinel-1A data from 2017 to 2019 using SBAS method. Results uncovered that the land surface deformation rate along Yangtze River in Badong ranged between -5 mm per year and 5 mm per year, which was relatively stable. With the spatial and temporal influences of water level fluctuation into consideration, the time series deformation map was further analyzed by classifying into different buffers according to the distance from river. The deformation of the area is little affected by the change of water level.
  • CONSTRUCTION AND MANAGEMENT OF WATER CONSERVANCY PROJECTS
  • GUO Hui , LI Lin, LAN Dao-yin, SHI Zheng-guo, GUO Wen-kang
    Journal of Changjiang River Scientific Research Institute. 2021, 38(5): 153-158. https://doi.org/10.11988/ckyyb.20200235
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    Huangdeng dam is the world’s tallest RCC (roller-compacted concrete) gravity dam under construction with a maximum height of 202 m. Affected by geological conditions and other factors, some engineering problems emerged in the construction process. Such problems include the quality fluctuation of raw materials, the contradiction between new test standard and original design indexes, as well as the coated-powder of aggregate. In this paper, the whole process of solving the above engineering problems by the third party inspection is introduced; the advantage of the third party inspection in additional quality control service is expounded, and the key role of the third party inspection in the quality control of RCC in Huangdeng Dam is revealed so as to offer reference for similar engineering construction.