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01 July 2019, Volume 36 Issue 7
    

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    SPECIAL CONTRIBUTION
  • YANG Xiao-liu, FAN Jia-hui
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 1-6. https://doi.org/10.11988/ckyyb.20190241
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    Data mining technology is employed for the feature extraction and pattern identification of about 260 thousand water use data collected in the Monitoring and Control Program of Water Use Units by the Ministry of Water Resources. Using the k-means clustering algorithm based on the Davies-Bouldin index, the dataset is categorized into three features, i.e., feature of water saving status quo as reflected by WSE, feature of expected water saving willingness as reflected by EW, and feature of monthly water saving volatility as reflected by Cv. The WSE value of most water use units concentrates in [0.7, 0.9], EW in [0.8, 1.0], and Cv in [0.1, 0.5]. Furthermore, on the basis of the features extracted above, water use pattern is classified as five groups, namely, balanced expansion pattern, balanced contraction pattern, centralized stable pattern, fluctuated contraction pattern, and fluctuated expansion pattern. Compared with inland areas, the southeast coastal areas produce less volatile monthly water consumption. Among the five water use patterns, fluctuated contraction is the dominant pattern covering most high consumption industries with excessive productivity; fluctuated expansion and balanced expansion mainly distributes in high-tech manufacturing industry and service industry; and centralized stable pattern in agricultural industry. In addition, management suggestions are put forward respecting laws and regulations and monitoring work to offer reference for a more precise and targeted water saving management.
  • RIVER-LAKE SEDIMENTATION AND REGULATION
  • XU Xin-fa, HUANG Zhi-wen, ZHOU Su-fen, WU Nian-hua, TANG Li-mo
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 7-13. https://doi.org/10.11988/ckyyb.20171431
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    As alluvial bifurcate channels, the tail channels of Ganjiang River are divided into West River and East River, of which the former evolved into west branch and north branch and the latter developed into middle branch and south branch. In recent years, human activities has fundamentally changed the hydrologic regime of the tail reaches of Ganjiang River, hence affecting the water resources utilization and water eco-environment in the downstream. In the purpose of investigating the effects of regulating projects, we examine the influences of flood level, water diversion ratio, and flow velocity distribution on the river regime in the presence of different regulating projects via physical model test. Test results verify that controlled blocking project in the north branch has apparent effect on the flood level, water diversion ratio, and flow velocity distribution in each branch, whereas dredging in the south branch and building sluices in the four branches have slight impact. Dredging in the south ranch mainly results in the shift of major streamline towards the left bank, while has little impact on sectional maximum flow velocity. The test results offer reference for the optimization of the regulation projects.
  • WATER RESOURCES AND ENVIRONMENT
  • YAN Bo, ZHANG Xiao, XIA Zi-qiang, GUO Mian-chen, LIU Chen-xi, LUO Yun-ying
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 14-17. https://doi.org/10.11988/ckyyb.20171298
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    In a purpose of comprehensively researching the changes in precipitation in the Heilongjiang River Basin, we collected the precipitation data of 25 stations in the basin and examined the features of precipitation trend by linear trend method, accumulative anomaly method and variable scale trend analysis method; moreover, we also looked into the abrupt changes of precipitation by Mann-Kendall method, and the periodic characteristics by wavelet analysis. Results manifested that the linear trend change rate is only -0.74%/(10 a) during 1954-2012. We found no significant trend change in 97.7% of the effective time period. The accumulative anomaly method and Mann-Kendall method revealed that the precipitation changed in apparent stages, while wavelet analysis confirmed the significant periodicity of precipitation in dominant periods of 28, 12 and 4 years. In summary, the periodicity of precipitation changes in the Heilongjiang River Basin is significantly stronger than the trend. Study on the change of precipitation in Heilongjiang River Basin could provide realistic basis for Sino-Russian cross-border river management.
  • XU You, YANG Zheng-jian, XU Ya-qian, CHENG Bao, LIU De-fu, MA Jun
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 18-22. https://doi.org/10.11988/ckyyb.20171271
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    The construction of hydropower stations in the Lancang River basin since the 21st century will bring about far-reaching influence on the ecological environment in the basin. In this paper the impact of cascade reservoirs on water temperature along the Lancang River was examined via interpolation method, data homogenization and significant difference analysis according to the results of three observations on water temperature and historical hydrological data in the Yunnan segment of the Lancang River. Research results imply that: (1) the water temperature along the Lancang River before and after the construction rises linearly with the decline of latitude and altitude; (2) in a holistic sense of the entire basin, the construction of cascade reservoirs has no significant impact on the water temperature change along the river. The research findings offer reference for the joint dispatching of cascade reservoir groups by providing holistic understanding of water temperature change in the whole basin.
  • WU Guang-dong, XU Ji-jun, Hoshin Gupta, ZHANG Xiao
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 23-27. https://doi.org/10.11988/ckyyb.20171318
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    Despite wide application abroad, the “abcd” water balance model is barely used in China. In order to explore the applicability and effectiveness of the “abcd” model in small and medium-sized watersheds in China, we first of all expound the principle and structure of the “abcd” model, and applied the model to the runoff forecasting simulation for Xin’an River Basin. Moreover, we examined the sensitivity of four parameters of the “abcd” model for the first time in China by comparing the simulated values with measured values, and further discussed the responses of performance indicators to parameter changes using univariate and multivariate methods. Results manifested that Nash-Sutcliffe efficiency (NSE)in verification is 0.929 in flood season and 0.863 in non-flood season, indicating a high fitting degree. Meanwhile, sensitivity analysis could evidently improve the efficiency and accuracy of calibration. Result of the univariate method is similar to that of the multivariate method, and NSE is the most sensitive to parameter c. In conclusion, the “abcd” model can be widely applied to small and medium-sized watersheds in China with high accuracy and adaptability.
  • WANG Yu-shan, CHENG Xu-xue, LIAN Sheng, ZHANG Meng-nan
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 28-32. https://doi.org/10.11988/ckyyb.20171348
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    Radon isotope was utilized as a tracer to determine the river-groundwater interaction and explore the spatial variation and controlling factors of 222Rn activity in river water and groundwater in the lower reach of the Malian River. Isotope gradient was proposed as an indicator of the magnitude of river water and groundwater interaction. The results implied that 222Rn activity was considerably lower in river water than that in groundwater. The highest 222Rn activity in groundwater was found in the Cretaceous aquifer, followed by the loess aquifer, the quaternary aquifer, and river water in sequence. Moreover, 222Rn activity in groundwater was controlled by lithology, geological formation and redox conditions and lithology was the most important factor, whereas 222Rn activity in river water was influenced by groundwater discharge. The distribution of 222Rn isotopic gradient provided a detailed profile of river water and groundwater interaction. A positive index indicated that groundwater had entered surface water between those sites of R02-R03, R03-R04 and R13-R14, while a weaker interaction in other sites.
  • CHEN Ang, WU Miao, WANG Peng-yuan, WEN Jing-ya, LI Hui, WU Sai-nan
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 33-40. https://doi.org/10.11988/ckyyb.20171412
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    The ecological flow database of hydropower projects in China is built by analyzing the environmental impact assessment reports of 96 hydropower projects from 2001 to 2015 in aspects of project status, hydrological characteristics, fish status and ecological base flow using statistical method in association with ArcGIS platform. The differences in calculation method, spatial-temporal distribution, release type, guarantee measures and monitoring measures of ecological flow before and after the implementation of Environmental Impact Assessment Guideline 2006 were examined, and the ecological benefits of such differences for endangered fish protection in the downstream of dam were analyzed. Moreover, the effectiveness of guaranteeing the ecological flow after the implementation of Guideline 2006 is presented, and meanwhile, shortcomings and countermeasures are expounded as well. In conclusion, the major limits of ecological flow practice of hydropower project in China are summarized, and future development trend is put forward respecting the calculation principle, flow process demand, joint dispatching of cascade reservoirs, and research on ecological restoration.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • XIAO Lei, HUANG Yao-ying, WAN Zhi-yong
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 41-47. https://doi.org/10.11988/ckyyb.20171497
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    As the mechanical parameters of concrete dam obtained by indoor test deviates largely from measured values, back analysis of parameters using optimization or bionic algorithm based on measured deformation is adopted in practical engineering. To address the nonuniqueness of parameter inversion, we propose to obtain the probability distribution function of multiple back analysis results based on measured deformation via probability statistical approach, and then determine the inversion parameters according to 80% guarantee rate. The proposed method is verified by the measured deformation values of a roller compacted concrete (RCC) dam in high and cold region. The method provides stable mechanical parameters of dam body and dam foundation, and offers a reference for the safety assessment of RCC dam in high and cold region.
  • DONG Dan-dan, ZU An-jun, SUN Xue-lian
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 48-54. https://doi.org/10.11988/ckyyb.20171438
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    Back Propagation (BP) neural network has been widely used to establish monitoring models in analyzing dam deformation data. Nevertheless, when optimizing the BP neural network parameters, Ant Colony Optimization (ACO) algorithm converges slowly in the beginning due to completely random search. In the present study, a dam deformation monitoring model combining genetic ACO, BP, and Markov Chain (MC) is built to tackle this problem. First of all, Genetic Algorithm (GA) which has remarkable ability of global search is introduced to help guide the initial distribution of pheromone, and the optimal solution is obtained by the positive feedback of ACO to train BP neural network to get the predicted values of dam deformation. Since the advantages of the two algorithms are complementary, this improvement greatly reduces the time taken in the initial stage of optimization and avoids falling into the local optimum. Furthermore, to improve the prediction accuracy, MC is employed to correct residual errors of the prediction results. Engineering application case manifests that the model is of good ability of fitting and prediction with fast searching speed in parameter optimization.
  • XU Zhen-kai, XU Xing-zhong, WEI Bo-wen, YANG Bin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 55-60. https://doi.org/10.11988/ckyyb.20171397
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    A cloud model for safety evaluation of concrete dam performance based on unit constraint combinatorial weighting is proposed in this paper to tackle the uncertainties of ladder-level index weight, the reasonable weighting of subjective and objective combinatorial weights, and the fuzziness of membership interval in the evaluation. First of all, the system of evaluation indicators is built, and the weights of such indicators are given by optimum weighting under unit constraint condition combining G1 method for subjective weights and entropy method for objective weights. Furthermore, the concept of cloud model was introduced to quantify the randomness of the evaluation indicators and the fuzziness of the membership intervals. The model is applied to evaluate the safety of a practical concrete dam, and the evaluation result is consistent with the actual situation of the dam and the results evaluated by other models, which verifies the effectiveness and feasibility of the model.
  • HYDRAULICS
  • YANG Sheng, LI Xiao-qing, GAO Qiang, DENG Ming-song
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 61-63. https://doi.org/10.11988/ckyyb.20171247
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    Type Ⅱ broken-line practical weir has been widely used in small and medium-sized water conservancy projects. Nevertheless, a comprehensive and correct solution to the flow coefficient of broken-line weir with varied water head and ratio of weir height is still in lack. In view of this, we determined the flow coefficient of type-II broken-line practical weir based on indoor measurements of hydraulic model test, and further deduced a simple and practical calculation formula for type II broken-line weir in association with correlation analysis and linear regression. In the laboratory hydraulic model test, the slope gradient in the upstream and downstream of weir ranges between 0.5 to 3.0, which is commonly adopted in engineering, and the relative weir height is limited between 2.0 and 0.5, and relative weir crest’s thickness between 1 and 2.5. The proposed method provides basis and reference for engineering design.
  • ROCK-SOILENGINEERING
  • HE Gui-cheng, WANG Zhao, LI Feng-xiong, ZHU Ze-yong, ZHANG Qiu-cai, ZHANG Zhi-jun
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 64-69. https://doi.org/10.11988/ckyyb.20171352
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    The effect of temperature on the mechanical behaviors of slope interlayer was investigated on direct shear test device with temperature control heating system. Seven interlayer specimens with different mix proportions of bentonite and river sand at varied moisture content (10%, 13%, 15%) were prepared for the test. The shear strength indexes of slope interlayer specimens at different temperatures were measured to further examine the failure mechanism. Results demonstrated that at a given temperature, cohesion and shear strength of interlayer specimens decreased with the shrinking of bentonite content; while with the climbing of temperature, specimens of high bentonite content experienced dramatic decline, gentle decline, and then finally dramatic decline again in terms of cohesion and shear strength. Moreover, such relation curve tended to be gentle and finally displayed a linear decline with the rising of moisture content. As temperature decreased, the resultant force of water in slope interlayer decreased correspondingly, which weakened the microstructural force among soil particles, resulting in a sharp reduction of cohesion; when temperature exceeded 50 ℃, cohesion decreased dramatically again because of slip of soil particles, giving rise to a critical failure state. Therefore, cohesion is a key factor inducing the failure of interlayer specimen, and the critical point of cohesion reducing dramatically again could be regarded as the indicator of the failure of slope interlayer.
  • LI Jin-qiu, WANG Xiu-yan, LIU Chang-li, SUN Lin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 70-76. https://doi.org/10.11988/ckyyb.20171196
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    The deformation characteristics of typical saturated silty clay under long-term traffic load in Jiaozuo area were investigated through dynamic triaxial tests on single undisturbed specimen under multistage loading and parallel specimens under constant amplitude of loading. By analyzing the strain-vibration curve and dynamic stress-strain hysteretic curves, the influences of dynamic stress, confining pressure, consolidation mode, and vibration frequency on soil deformation were examined. The following conclusions were obtained: the development mode of dynamic strain of typical silty clay in Jiaozuo can be mostly summarized as steady mode and destructive mode—dynamic strain grew steadily at a certain stress level and developed to failure when that stress level was exceeded—rather than critical mode. The strength of single soil specimen intensified under step-by-step loading, and the dynamic stress level required to result in failure increased correspondingly. As for multiple specimens under constant amplitude of loading, the deformation surged until failure happened even in the presence of low vibration frequency when dynamic stress exceeded a critical value. In addition, the increment of confining pressure and consolidation ratio could also raise the soil strength, with less recoverable elastic deformation. When vibration frequency was smaller or larger than a critical value, the deformation of soil both increased.
  • WANG Jang-feng, DU Chun-xue, LI Nan, GUO Lin-fang
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 77-82. https://doi.org/10.11988/ckyyb.20171360
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    The Enziping 2# landslide is a typical bedrock bedding landslide located at about 8.6 km downstream of Baihetan Hydropower Station. We analyzed the stability of the landslide qualitatively by means of physical simulation tests, and meanwhile discussed the laws of displacement, stress, and deformation changes under different working conditions via numerical simulation based on engineering investigation data. Results suggest that the combination of physical simulation and numerical simulation is an effective approach to analyzing the causes of landslide formation. The displacement of landslide increased gradually from bedrock to sliding body, with the maximum displacement reaching 185 cm under flood level condition, and the deformation mainly occurring in sliding body. The maximum tensile stress was found at the underwater accumulation of the landslide. It natural state, the landslide was stable, and the safety coefficient was 1.065 6; under flood level condition, the safety factor of landslide reduced to 0.76 when the landslide tended to be unstable and the front edge of the slide was likely to suffer from local buckling down.
  • CHANG Jun-bin, KE Xian-min, WANG Wei, SUN Qi-ming, TIAN Guo-lin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 83-88. https://doi.org/10.11988/ckyyb.20171468
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    A 3D hydrological and stratigraphic structure model was built based on strata revealed by geological radar and drilling data to probe into the efficiency of water yield of seepage wells in Mazhen county. The model was identified and verified by pumping test of seepage well and the hydrogeological parameters were determined. Sensitivity analysis of the model parameters unveiled that the horizontal permeability coefficient of the quaternary strata had the greatest influence on the water intake effect of seepage well, while the value of recharge C1 of river had the least influence on the water intake of seepage well. Moreover, optimization design of the seepage well structure evinced that the angle of altitude of radiant tubes between 20° and 30° and spacing of chambers between 75 m and 100 m will result in a good efficiency of water intake by seepage well.
  • ZHOU Wen-hai, YU Jian-ping, LIANG Rui, L Ya-ru, WANG Dun-fan, CHEN Zong-jie
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 89-95. https://doi.org/10.11988/ckyyb.20171331
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    In order to study the variations of physical variables affecting the blasting effect in the process of slope throw blasting, we functionized all variables in the Sadaovsk formula considering the influence of elevation and modified the factor function by multivariate regression fitting to determine the functional relationship. Subsequently we conducted stepwise regression analysis of Sadaovsk formula and gave the value of correlation coefficient. Results evinced that unit volume of single-hole blasting is the dominant factor of the explosive charge function. When the line of least resistance is over 2.0 m, the influence of other factors is below 10%. The critical elevation difference for elevation amplification effect is about 38 m. In addition, the main vibration frequency exhibited a decreasing trend with the increase of the horizontal distance R when the specific charge ρ is a fixed value; so did it when the explosive charge Q is a fixed value, and the deceleration rate reduced gradually. When R is a fixed value, the main vibration frequency declined also with the rising of Q, and such deceleration attenuated gradually. The research findings could be utilized to mitigating the vibration of surrounding buildings generated by slope blasting and to ensuring the final stability of slope.
  • XUN Xiao-hui, WEI Yu-feng, FU Wen-xi, ZHANG Bin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 96-99. https://doi.org/10.11988/ckyyb.20171284
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    A simple and rapid method of triaxial test on non-filled rock specimens containing irregular discontinuities by using rock mechanics test system (MTS) is presented in this paper. Multiple shear strength data can be obtained by using this method in the presence of only one single specimen. The difficulty of preparing test specimen is overcome and the highly discrete test results can be avoided. In addition, approaches to determine the parameters of linear Mohr-Coulomb criterion fitting, power function fitting and nonlinear Barton equation fitting according to test results are examined and the results of different approaches are compared to verify the rationality of the method. The application scope of the test method is also put forward. Results suggest that power function fitting and nonlinear Barton equation fitting are superior to Mohr-Coulomb criterion in reflecting the nonlinearity of shear strength of jointed rock. When 0.01<σnj/JCS<0.3, the result of shear strength of jointed rock obtained by the two fitting methods are reliable; when σnj/JCS>0.3, the result is larger.
  • PENG Ci-de, CHANG Liu-cheng
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 100-105. https://doi.org/10.11988/ckyyb.20171311
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    In this paper, the swelling and shrinkage properties of red clay under different temperatures were studied via swelling deformation and shrinkage deformation test with initial moisture content and initial dry density as contrast variables. The influence of temperature on volumetric shrinkage rate, final linear shrinkage rate, and shrinkage coefficient was analyzed. The experimental results revealed that expansion rate increased correspondingly with the rising of initial moisture content; the expansion rate of sample with the highest dry density increased most obviously, while the expansion rate of sample with the lowest dry density decreased with the rising of moisture content.With the climbing of temperature, shrinkage rate presented an overall increasing trend, and in particular, expansion rate surged when temperature exceeded 80 ℃; but volumetric shrinkage rate, linear shrinkage rate and shrinkage coefficient displayed a holistic declining trend. As moisture content declined, the shrinkage curve of red clay can be divided into three stages at different temperatures: oblique straight line, convex, and straight lines, each with different shrinkage velocities and amplitudes.
  • CHANG Yu-lin, WEN Sen, ZHANG Jian-wei
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 106-111. https://doi.org/10.11988/ckyyb.20171484
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    As the dynamic destruction of mixed rock strata are increasingly observed in engineering, it is indispensible to study the mechanism of dynamic destruction. A numerical model of split Hopkinson pressure bar (SHPB) was established by PFC2D to simulate the dynamic failure process of mixed rock strata specimens with different dip angles of rock strata at varied strain rates. The conclusions are drawn from numerical simulation as follows: 1) as the dip angle of mixed rock strata increased, the dynamic compressive strength and dynamic elastic modulus reduced at first and then surged, displaying a “V”-shaped curve; 2) dynamic compressive strength increased correspondingly with the climbing of strain rate, while dynamic elastic modulus is less affected by strain rate; 3) the cracks of mixed rock strata were dominantly tensile cracks, and dynamic fragmentation exacerbated with the increasing of strain rate; 4) the macroscopic failure mode of specimen was affected by the number and coalescence of cracks. The research findings are conducive to understanding the dynamic failure mechanism in mixed rock strata.
  • JIA Qin-ji, WU Li, PENG Ya-xiong, ZHU Bin-bin, LI Chun-jun
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 112-117. https://doi.org/10.11988/ckyyb.20180789
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    Due to complicated and diverse circumstances and the difficulty in observing blasting process, underwater blasting project is prone to cause landslides and cracks in buildings and roads as quantitative assessment of regional risk in advance is thus challenging. With the underwater reef demolishing project in the Jiulongpo-Chaotianmen segment of upstream Changjiang River as a research background, we assessed the risk levels of blasting-affected regions using a comprehensive method integrating analytic hierarchy process (AHP) and fuzzy mathematics. In line with the three stages of blasting, namely, blasting stage, propagation stage, and vibration resonance stage, we established an assessment model with geological features, blasting parameters, propagation features, and safety control as four assessment indicators. Comparison between the results of model application and on-site monitoring verified that the assessment method is strongly practical with good effect in the assessment of risk level of underwater blasting.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • SHAN Liang, CUI Jian-hua, SU Hai-dong
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 118-124. https://doi.org/10.11988/ckyyb.20181135
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    By numerically simulating the whole process of construction using 3D finite element method, we analyzed some key technical issues of the ship lift tower structure of Three Gorges Project (TGP) in construction period. Such issues include the influences of construction schedule, wind load, embedded position of prestressed sleeves, and creep. According to simulation result, 1) the maximum tensile stress and deformation of tower structure poured in October were smaller than those in April, while the maximum vertical displacement in both cases occurred in the position where concrete was poured in high-temperature season. 2) Wind load had an evident influence on tower structure in the presence of a large height difference between the backfill elevation of wide groove and the casting elevation of inner wall, and before the top sealing of tower body. 3) The vertical displacement of rack and nut column, directly related to the embedded position of prestressed sleeves, was affected by the self-weight of the upper concrete, and such effect changed periodically with atmospheric temperature. 4) Creep had little effect on the rack and the nut column, and stayed within the range of installation accuracy requirements. The research findings offer reference for the construction schedule and accuracy control for the TGP ship lift tower.
  • GONG Ya-qi, SU Hai-dong, CHEN Qin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 125-130. https://doi.org/10.11988/ckyyb.20171466
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    The deep anti-sliding stability of concrete gravity dam under seismic action is an issue receiving much concerns in hydro-structure design. In this paper, an analysis method for the deep anti-sliding dynamic stability based on rigid body limit equilibrium method and finite element method is proposed and corresponding numerical process is formulated. Firstly, the radiation damping effect is considered by setting a viscous-spring artificial boundary condition in the foundation model; the seismic wave velocity and the arrival time of incident wave are set different by partitions to reflect the non-uniformity of rock strata. Furthermore, the factor of safety is calculated by decomposing external load into sliding force and drag force in the rigid finite element result by directly calculating the internal force of cross-section in the model with double sliding surfaces recommended in specification. Subsequently, the two key parameters of the model with double sliding surfaces are determined through sensitivity analysis, and the effects of foundation’s uniformity on deformation and stability of the structure are compared. The proposed method is verified to be effective by a calculation case study of Xiaonanhai gravity dam.
  • TAN Cai, WAN Li, YUAN Ming-dao, LU Bo, LIN Yue-qi
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 131-136. https://doi.org/10.11988/ckyyb.20171467
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    Dynamic triaxial tests were carried out on three groups of desulphurized gypsum samples with compactness of 0.85, 0.90, and 0.95 to examine the dynamic modulus and damping ratio of desulphurized gypsum with varied compactness. The test was divided into two parts: isotropic consolidation test and anisotropic consolidation test, of which the former was conducted at consolidation stress ratio 1 under confining pressure as of 100 kPa, 200 kPa, and 400 kPa, respectively, and the latter at consolidation stress ratio 1, 1.5, and 2 under confining pressure as of 100 kPa. Test results evinced that with the increase of degree of compaction, the dynamic modulus of desulphurized gypsum augmented gradually; damping ratio changed inapparently when dynamic strain was less than 10-5, and gradually reduced when dynamic strain exceeded 10-5.The initial dynamic modulus displayed a good power correlation with compaction degree. The formula of initial dynamic modulus in consideration of the influence of compaction degree was established, and the holistic process curve of dynamic modulus attenuating with the change of compaction degree was also obtained. In addition, the normalized dynamic modulus and damping ratio of desulphurized gypsum showed little difference. The range of reference dynamic strain of desulphurized gypsum was given as 1×10-4~4×10-4.
  • ZHOU Qing-hui, CHEN Gang, XU Quan-biao, GONG Shun-feng, XIAO Zhi-bin, LIU Cheng-bin
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 137-142. https://doi.org/10.11988/ckyyb.20171396
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    Ordinary ultra-high strength concrete pipe pile with prestressed steel bar is of low deformation ductility and horizontal load-bearing capacity. To tackle this problem, we replaced the prestressed bar with prestressed steel strand and compared the performances (including shearing capacity, deformation ductility, damage characteristics and cracking pattern) between prestressed steel strand ultra-high strength concrete pipe piles and ordinary prestressed ultra-high strength concrete pipe piles via shearing performance tests on six full-scale pipe pile specimens of three commonly-used pile types. Results evinced that replacing steel bars with steel strands as main reinforcement could effectively improve the deformation ductility and the ultimate load-carrying capacity of pipe piles under shearing condition. The cracks of ultra-high strength concrete pipe pile with prestressed steel strand develop more densely and uniformly, shorter in vertical direction yet with more lateral bifurcations than those of ordinary prestressed ultra-high strength concrete pipe piles. Ordinary prestressed ultra-high strength concrete pipe pile specimens are destructed following the tensile failure of steel bars; the failure of ultra-high strength concrete pipe pile specimens with prestressed steel strand are generated by the crushing failure of compressed concrete zone with shearing failure lagging behind flexural failure.
  • GUO Hai-peng, LI Gang, LIU Jie, TAN Hang
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 143-148. https://doi.org/10.11988/ckyyb.20171439
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    The effects of WG-Ⅰ warm mix additive (WMA) on the performance of hydraulic asphalt and asphalt concrete are investigated. First of all, the effects of adding different dosages of WMA on three indicators(needle penetration, softening temperature, and ductility) and viscosity as well as density of No. 90 hydraulic asphalt are inspected, and the influence of WMA as of 4% dosage at different aging times on the performance of asphalt is also examined. Furthermore, Marshall specimens of asphalt concrete mixed with different dosages of WMA are prepared for splitting test to obtain a proper WMA content as 2%. Subsequently, the asphalt concrete specimens with 2% WMA are used for bending test, tensile test, and compression test. Ordinary asphalt concrete specimens are also tested for comparison. Research findings demonstrate that WG-1 WMA is conducive to reducing the viscosity of asphalt, and in the meantime enhancing the aforementioned three indicators. Asphalt concrete mixed with WMA is of good performances with strain capacity improving remarkably, favorable for asphalt’s ability of self-healing and adapting to deformation of asphalt. In conclusion, WG-1 WMA can be used as a warm mix material for hydraulic asphalt concrete in the purpose of saving cost, shortening construction period, and protecting environment.
  • CHEN Jia-jian, NG Pui-Lam, GUAN Xian-zhang Garfield
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 149-152. https://doi.org/10.11988/ckyyb.20171297
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    Microsilica is able to improve the strength and durability of concrete, but the effect of microsilica on adiabatic temperature rise of concrete is unclear. Researchers had even obtained contradictory findings. In this study, 15 concrete samples mixed with microsilica of varied content at different water-binder ratios were produced for semi-adiabatic temperature rise experimental measurement, and then the adiabatic temperature rise of each concrete sample was calculated with the heat loss compensation technique. Results demonstrated that the addition of microsilica could suppress the adiabatic temperature rise at the same water-binder ratio and the same strength. The adiabatic temperature rise amounted to 1.8~7.3 ℃ in the presence of 5% microsilica, and 3.3~10.2 ℃ in the presence of 10% microsilica. The suppression of adiabatic temperature rise was affected by water-binder ratio. On the basis of the result of adiabatic temperature rise, the predication formula and design chart for predicting adiabatic temperature rise of microsilica concrete were presented.
  • INFORMATION TECHNOLOGY APPLICATION
  • WAN Hong-xiu, WU Hao, GUO Ya
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 153-158. https://doi.org/10.11988/ckyyb.20181204
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    Bibliometric approach was employed in this paper to reveal the status and development trends of research on Changjiang (Yangtze) River flood based on SCIE and CSCD. The publication age, cooperative nations, core authors, author’s affiliations, and hot keywords were analyzed in detail. Results unveiled that: (1) the number of papers, in particular, SCIE papers, has surged after 1998, and the United States and Germany are top two countries which cooperate with China the most in the research. (2) The Chinese Academy of Sciences has been taking a leading role in contributing papers in English and Chinese languages, accounting for 31% and 23% of the total number of papers in SCIE and CSCD, respectively. Core authors of SCIE and the CSCD take up 27% and 21% of the total number of authors respectively. In SCIE, Journal of Hydrology was the top journal publishing research papers on Changjiang River flood, covering a proportion of 4%; in CSCD, Resources and Environment in the Yangtze Basin and Journal of Yangtze River Scientific Research Institute are top two periodicals publishing research papers on Changjiang River flood, each occupying a proportion of 7.28%. (3) Key words with a frequency over 20% included Three Gorges Reservoir, precipitation, climate change, sediment, and flood disaster. These key words had reflected the development of flood research in mechanism of disaster occurrence and disaster mitigation. Bibliometric information could provide reference for future flood related research in the Yangtze River Basin.
  • INSTRUMENTATION DEVELOPMENT AND TESTING TECHNIQUES
  • WANG Cong, WANG De-kuan, ZHANG Jian-min, LIU Tong-an, ZHANG Zhi-yu, ZHAO Long
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 159-163. https://doi.org/10.11988/ckyyb.20171427
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    In engineering practice, bulb tubular turbine units in hydropower station is prone to overspeed and low-frequency magnetic field suppression during load shedding due to small head, large flow, and small rotational inertia. Taking the hydropower units of Vitebsk hydropower station in Belarus as a case study, we expound the structure and basic principle of the speed governing system containing digital cartridge valve. On the basis of on-site test data of the speed governing system, we analyzed the strategies and advantages of digital cartridge valve in speed governing system. By improving the collaborative relationship between guide vane and blade, and adjusting the real-time regulating control of unit, the abovementioned problems are solved. The result manifests that digital cartridge valve is highly reliable for the speed regulating system of hydropower turbine, with the control accuracy and stability meeting standard requirements, hence is of good engineering application value.
  • ZHENG Long-jin, YANG Xiao-long, ZOU Lei, LUO Hai-quan
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 164-169. https://doi.org/10.11988/ckyyb.20171429
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    The detection of anomalies in the secondary lining of tunnel using ground penetrating radar (GPR) is affected by many factors, such as the difference of linear polarization mode caused by varying angle between the antenna connection and the detection direction. Analyzing the modes of linear polarization would offer guidance for construction and signal interpreting in detecting the defects of tunnel’s secondary lining using GPR. In this paper, the detection effects corresponding to horizontal polarization and vertical polarization are examined by establishing numerical models via GprMax3D. Numerical simulation and engineering example analysis reveal that with the angle varying from 0° to 90°, 1) the effectiveness of detecting steel bars in different depths in horizontal polarization mode attenuates gradually, while the effectiveness with vertical polarization remains unchanged; 2) the effect of detecting cavities of the secondary lining in horizontal polarization mode also diminishes gradually, whereas the effect with vertical polarization stays stable; 3) on the contrary, the detection of thickness-insufficient zone in horizontal polarization mode strengthens, but in vertical polarization mode the detection effect weakens; 4) the detection of crushed zone is barely affected by polarization mode but by the value of dielectric constant of surrounding rock. The above research findings can be used to guide the quality inspection for the secondary lining of tunnels.
  • SCIENCE AND TECHNOLOGY NEWSLETTER
  • HUANG Ze-xiao, SUN Hong-liang
    Journal of Changjiang River Scientific Research Institute. 2019, 36(7): 170-174. https://doi.org/10.11988/ckyyb.20171495
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    Remotely operated underwater vehicle (ROV) is employed in the nondestructive inspection of erosion damage of a deep-buried long tunnel after long-term operation to offer data basis for safety evaluation and maintenance. The defectives and deposits on concrete surface, the abrasion of tailrace floor, and the integrity of contact locations are inspected via full-coverage scanning using sonar in the ROV system; important parts and sonar-inspected abnormal areas are verified through videos obtained by autonomous underwater vehicle. This engineering practice provides engineers with the operation status of deep-buried long tunnel subjected to long-term scouring. In addition, the advantages and shortcomings of the application of ROV are also presented.