01 February 2016, Volume 33 Issue 2

    

• Select all
  |

RIVER-LAKE SEDIENTATION AND REGULATION
• Select
  Advances in Research of Cohesive Sediment Flocculation

  CHAI Zhao-hui, LI Hao-jie, WANG Qian, YANG Guo-lu, LIU Tong-huan

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 1-9. https://doi.org/10.11988/ckyyb.20140855

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Because of flocculation character of cohesive sediment particle, the particle is different from coarse sediment particle in physical and transport properties. Therefore, the flocculation of cohesive sediment is a hotspot in the theoretical research of river and ocean sediment. In this paper, we summarize research results of cohesive sediment flocculation according to experiments and mathematical models, and introduce advances in the research up to date, as well as existing problems in these studies. There are 3 problems should be paid attention to: 1) experimental studies are mainly focused on single influencing factor, lack of multi-factor research; 2) pattern researches on 3-D structure of sediment flocs are not enough; 3) relevant mathematical models can only describe qualitative laws, rather than quantitative laws. Finally, we should strengthen some aspects in future study on the flocculation of cohesive sediment, such as similarity criteria, multi-factor experiment research, and 3D simulation on large scale.

• Select
  Analysis on Multiple Temporal Scales of Runoff and Sediment and Simulation of Annual Sediment Discharge at Zhangjiashan Hydrological Station of Jinghe River

  TAO Wang-xiong, ZHANG Jie, WANG Qing, LIU Zhao

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 10-13. https://doi.org/10.11988/ckyyb.20140839

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to obtain the basic law of water and sediment variation in Jinghe River, we decompose series of annual runoff and sediment discharge into multiple temporal scales by EMD method, with Zhangjiashan station from 1956 to 2011 as an example. Firstly, we establish a simulation model of annual sediment discharge according to measured data and time series analysis. Then, the results show that both of the annual runoff and sediment series can be decomposed into 3 fluctuation components with different periods and a degressive tendency residual component. Furthermore, the model is of good suitability and high accuracy, and it can be used to predict annual sediment discharge. Finally, we can carry out characteristic analysis on multiple temporal scales of runoff and sediment and prediction of annual sediment discharge to provide a scientific basis for water resources planning in Jinghe River.
WATER RESOURCES AND ENVIRONMENT
• Select
  Negative Effects of Diversion Tunnel Construction on Groundwater Environment near the East of Erhai Lake in Yunnan

  WANG Ya-li, XU Mo, ZHANG Qiang, ZHOU Zhong-hai

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 14-18. https://doi.org/10.11988/ckyyb.20140811

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to prevent negative effects of tunnel construction on groundwater environment, we applied an evaluation system to a diversion tunnel project located near the east of Erhai Lake in Yunnan. On the basis of analysing the geological and hydrogeological conditions, we employed analytic hierarchy process (AHP) and fuzzy comprehensive evaluation method to select appropriate index weight and evaluate negative effects on groundwater environment. Results show that when the tunnel goes through Hecun segment of Dali, negative effects of level IV within 5 000 m on both sides of the tunnel and decline of groundwater are caused by tunnel construction. Ground subsidence, karst collapse, obvious surface flow reduction, and wellspring depletion will also take place. The research results offer reference for the construction and design of the diversion tunnel.
• Select
  Application of δ¹⁵N and δ¹⁸O in Identification of Pollution Sources in Taihu Lake

  ZHU Peng, ZHU Fei

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 19-23. https://doi.org/10.11988/ckyyb.20140857

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Through summarization and comparison of the pollution sources of Taihu Lake, we determined four sources: industry, agriculture, sewage, and rain. Sixteen samples from both lake area and tributary area were collected, and δ¹⁵N and 和δ¹⁸O in these samples were measured. The contribution ratio of pollution sources was analyzed based on the stable isotope technique in association with the model of isotope conservation of mass. Results show that pollutions from industry and agriculture are more serious than those from sewage and rain. As for the samples into the lake from tributary area, the proportion of industrial pollution is basically higher than that of agricultural pollution, and the result of samples from relatively closed lake area is similar, whereas for samples from relatively broad lake area, the result is reverse. On the basis of rationally classifying water pollution resources, quantitative study using isotope technique and numerical model could provide reference for the harnessing of pollution sources of lake. It is also an important approach of determining pollution sources for lake water and pollution conditions.
WATER-SOIL CONSERVATION AND ECO-CONSTRUCTION
• Select
  Research Advances in Mapping of Soil Erodibility Factor and Its Uncertainty

  SUN Jia-jia, WANG Zhi-gang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 24-27. https://doi.org/10.11988/ckyyb.20140824

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Soil erodibility is an important indicator of assessing impact of erosion on soil, and also an important parameter for predicting soil erosion. In order to promote relevant research of soil erodibility factor in the future, we present state of the art in China and abroad in terms of its spatial prediction and error and uncertainty of mapping. Analysis shows that accurately acquiring spatial distribution of soil erodibility factor is of practical significance, but it is a difficult task due to complex factors which affect soil erodibility factor. In the future, we should lay emphasis on reducing mapping error, improving accuracy and controlling risk, and quantitatively analyzing the uncertainty of spatial prediction, in association with auxiliary information such as soil types, elevation, and remote sensing images.
• Select
  Rainfall Infiltration and Characteristics of Runoff and Sediment Yield in Small Watershed of Three Gorges Reservoir Area

  LIANG Yong-zhe , XIA Zhen-yao, NIU Peng-hui, XU Wen-nian, CHEN Yi

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 28-32. https://doi.org/10.11988/ckyyb.20140682

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In Three Gorges reservoir area, concentrated rainstorm with short duration and high intensity is an important factor causing soil erosion. In the aim of investigating rainfall infiltration and characteristics of runoff and sediment yield in small watershed of Three Gorges reservoir area, we establish a miniature model for the area and simulate rainfall in the presence of different rainfall intensities(60, 90, 120 mm/h) to analyze rainfall infiltration of small watershed erosion and runoff process characteristics. Research results show that : 1) runoff yield increases with rainfall intensity, and the impact of rainfall intensity on increase of infiltration is effective only within a certain range; 2) infiltration rate and runoff yield intensity gradually tend to be stable, infiltration rate is in agreement with law of logarithmic function, whereas runoff yield intensity varies according to power function; 3) relationship between cumulative sediment yield and cumulative runoff in the three rainfalls can be fitted by power function, and there is a good linear relationship between sediment concentration and erosion yield. The results provide important scientific basis for the prevention and control of soil and water loss in the area.
FLOOD PREVENTION AND DISASTER REDUCTION
• Select
  Simulation on the Formation of Gully Network Due to Overtopping

  ZHANG Qiang, ZHOU Yang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 33-37. https://doi.org/10.11988/ckyyb.20140828

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  According to characteristics of the formation of gully network due to overtopping, we establish a cellular automata model to simulate the gully network formation. In the model of cellular automata, the water movement is sloping, and the rules of runoff and erosion of slope surface are determined by simulating slope surface erosion in association with the scour rate formula. Random topographic fluctuation and differences in anti-scouring performance of slope surface are taken into account in the calculation. Results indicate that the gully network is straight if only the random topographic fluctuation is considered, whereas the calculation result by considering the two factors is superior to that by considering single factor.
• Select
  Impact of Overtopping Breach Mode on Dam-break Parameters of Homogeneous Earth-rock Dams

  LUO You, CHEN Li, PING Yan-rong, ZHOU Min

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 38-41. https://doi.org/10.11988/ckyyb.20140806

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to simulate overtopping breach of homogeneous earth-rock dams, we carried out experiment in water tank using sand and clay to make mixed materials for dam, and discussed the impact of overtopping breach mode on dam-break parameters. We divided the overtopping breach modes into three kinds: erosion and scour of scarp(M1), erosion and collapse of shear (M2) and erosion and collapse of soak (M3). In the presence of given capacity of reservoir and dam height, maximum breach discharges (Q_p) of different modes are obviously unequal, and Q_p of M2 is the biggest. Breach Critical time(T_C) is referred to as the time from the beginning of overtopping to the developing of breach, and T_C of M2 is the smallest, followed by that of M1 and M3. Breach mode depicts the effects of overtopping flow, initial breach, dam height and dam materials on dam-break process. Besides dam height and capacity of reservoir, breach mode is another important factor for dam-break prediction and disaster assessment.
ENGINEERING SAFETY AND DISASTER PREVENTION
• Select
  Determination of Prewarning Index for Spatial Deformation of High Arch Dam in Jinping I Hydropower Station Based on Entropy Theory

  YIN Xiang-xiang, ZHOU Zhong, ZHAO Er-feng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 42-47. https://doi.org/10.11988/ckyyb.20140833

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Jinping I high arch dam has been constructed and is in the first impoundment period. But the persistent slope deformation at the left bank is affecting the chord length of the dam. In order to guarantee safe operation of the project, we determine space deformation about chord length as prewarning index. First of all, we calculate the entropy weight of each measured point by modified entropy method. Then we give the expression of deformation entropy of single measured point based on information entropy. On the basis of this, we establish the entropy of space deformation of each measured point. At last, we use the maximum entropy theory to generate the probability density function of space deformation entropy of chord length , and determine the prewarning index of the entropy. The results indicate that this method is highly effective and practicable, and provides reference for the safe operation of dam.
• Select
  Prewarning Model for Dam Safety Based on IPSO-RVM

  FAN Zhen-dong, CUI Wei-jie, CHEN Min, DU Chuan-yang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 48-51. https://doi.org/10.11988/ckyyb.20140801

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In view of the disadvantages of SVM (support vector machine) such as a large number of support vectors and strict demand for kernel function, we introduce RVM (relevance vector machine) to establish dam safety model which has better performance. Kernel function and its parameters have important effects on the performance of the RVM model. Mixed kernel function in association with local and global kernels can improve the fitting accuracy and generalization ability of the model. The optimized parameters of the kernel function can be effectively found by using PSO (particle swarm optimization) algorithm. However, the defect of local optimal point easily occurs in normal PSO algorithm. In light of this, we apply an algorithm of improved particle swarm optimization (IPSO). On the basis of combined algorithms above, we establish a model for dam safety, and the results indicate that the performance of RVM model with hybrid kernel is superior to that of conventional model.
HYDRAULICS
• Select
  Three-dimensional Numerical Simulation on Seawater Intrusion into Freshwater Canal Through Ship Lock

  JIANG Zhi-bing, LU Hong, YANG Qing-yuan

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 52-56. https://doi.org/10.11988/ckyyb.20150847

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to study the law of salt transportation in the operation of ship lock and its influence on salinity in freshwater area, we set up a three-dimensional numerical model for k-ε two-phase mixed flow. In the model, control equation groups are dispersed by finite volume method, velocity-pressure coupling by SIMPLEC algorithm, time term by single-order implicit expression, and convection term by second-order upwind scheme, with computing area divided by hexahedral mesh. This model is verified by comparison with prototype experimental results of sea water intrusion into a ship lock, and simulated data are well in agreement with measured data of salinity in lock chamber. The simulation results about the process of seawater intrusion into freshwater zone show that 1) distribution of salinity in upstream waterway can be divided to 3 sections: density current section, transition section and diffusion section, whose salt transporting speed reduces in order; 2) salinity periodically changes at each section and it gradually tends to be at a dynamic balance after ship lock operates for a period; 3) as for a given cycle, saline intrusion quantity is big at early stage of ship lock operation, then, it gradually reduces and tends to be stable. The research results offer scientific reference for the design and operation of ship lock.
ROCK-SOIL ENGINEERING
• Select
  Diffusion Range of Grout in Consideration of Dynamic Change and Correlation of Parameters

  LEI Jin-sheng, LIU Fei, PENG Gang, WANG Qian-feng, XIA Lei

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 57-61. https://doi.org/10.11988/ckyyb.20140719

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In grouting treatment and seepage prevention, diffusion of grouts plays an important role, involving solid skeleton’s stress-strain relation, seepage field distribution and grout concentration’s distribution gradient perpendicular to the diffusing direction. According to coupling of seepage field and stress field in porous media, we take into consideration the time-varying viscous characteristics of grouting parameters, and dynamic variation of physical parameters of grouting in porous media, namely density, porosity, and permeability. On the basis of this, we analyze the correlation and dynamic change of physical parameters and present a simulation method for grouting diffusion. In the simulation of homogeneous soil under fluid-solid coupling, we use finite element method to obtain spherical diffusion radius and cylindrical diffusion radius under the conditions of time-varying viscosity and unchanged viscosity. Compared with conventional theory of grouting diffusion, fluid-solid coupling simulation taking soil parameters and dynamic characteristics of slurry into account is very suitable for analyzing diffusion range of slurry in soil.
• Select
  In-situ Test on the Composite Foundation of Ram-compaction Gravel Pile with End Expansion

  YE Chao-liang, LIU Yao-jun, FENG Huai-ping

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 62-66. https://doi.org/10.11988/ckyyb.20140812

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  According to measured results of in-situ static load test, static cone penetration test(CPT), heavy dynamic penetration test(DPT), and indoor soil test, we analyze three mechanical parameters of composite foundation of ram-compaction gravel pile, namely pile-soil stress ratio, bearing capacity, and soil’s compacted effect with piles. We take the construction of ram-compaction gravel pile in the 14th bid of South-to-North Water Transfer Project, located in Handan, Hebei province, as an example. Results show that, pile-soil stress ratio of composite foundation of ram-compaction gravel pile with expanding head is bigger than that of normal gravel pile, which is from 4.2 to 7.4; pile-soil stress ratio first increases and then decreases with the increase of load, and gradually tends to be stable, and the ratio increases with the pile length; then, the gravel pile’s curve of load vs. settlement (P-S curve) exhibits gradual change, without obvious inflection point or abrupt change point; furthermore, bearing capacity of composite foundation of ram-compaction gravel pile increases with pile length. According to the results of CPT and DPT, we find that the rammed gravel pile can effectively improve the strength of soil among piles, and decrease uneven settlement of the foundation.
• Select
  Stress-relaxation Depth and Microscopic Failure Mode of Marble Tunnel by Using Different Construction Methods at JinpingⅡ Hydropower Station

  JI Feng, CHEN Zhong-hua

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 67-70. https://doi.org/10.11988/ckyyb.20140819

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  TBM (Tunnel Boring Machine) method and drilling and blasting method are two main methods in the excavation of underground projects. As for the two methods, disturbance range of surrounding rock, deformation and destruction characteristics, self-stability, and treatment measures are different. In order to accurately understand macroscopic mechanical characteristics of surrounding rock, we should analyze it at microscopic level. Diversion tunnel in JinpingⅡhydropower station ,with maximum embedded depth of 2 525 m, is taken as an example. We carry out tests of scanning electron microscope (SEM) and detect the depth of stress relaxation for marble tunnel under different excavation methods. The test results show that, 1) fracture surfaces of rock by scanning electron microscope in TBM method show pattern of wiping along crystal face and pattern of cutting crystal face, with shear failure as the main failure mechanism, whereas tensile failure for drilling and blasting method; 2) in the aspect of relaxation depth, stress-relaxation depths of surrounding rock excavated by drilling and blasting method are larger than those by TBM method, which vary from 40 cm to 100 cm. The research findings provide reference for failure mechanism of rock and reinforcement measures in projects with similar geological conditions.
• Select
  Mechanical Properties of Polypropylene Fibre-reinforced Soil

  SUN Shu, YUAN Xue-feng, LI Fu-lin, WANG Yue-hua

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 71-73. https://doi.org/10.11988/ckyyb.20140843

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to solve the problem of excessive deformation of sandy soil at road foundation caused by mining and automobile with heavy duty, we study the strength and deformation resistance of sandy soil under four different fiber lengths and blending amounts through triaxial compression test.Results show that the stress-strain relation of fiber-reinforced soil is approximately a hyperbolic function, in which the main failure form is swollen failure. With the increase of blending proportion and length of fibre, the mechanical properties of fibre-reinforced soil strengthen, but the angle of internal friction is barely affected. Finally, a fitting formula of cohesion vs. fiber length and mixing amount is obtained by multivariate regression analysis based on the 1stOpt experiment and the results meet the requirement of actual projects by comparison with measured data.
• Select
  Numerical Validation of Structural Constitutive Relationship of Loess with Moisture and Loading

  LUO Ai-zhong , SHAO Sheng-jun , CHEN Chang-lu , FANG Juan

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 74-79. https://doi.org/10.11988/ckyyb.20140501

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In this paper we propose a structural constitutive model of loess with moisture and loading. On this basis, we analyse the stress-strain relationship of structural loess by comparing the numerical simulation result with measured result of natural loess. Results show that the model has the same features with Modified Cambridge model in describing saturated remodeled loess. The model could also simulate the macro-mechanics properties of remodeling loess with different water contents. Moreover, it is obviously superior to Cambridge model or Modified Cambridge model in describing the macro-mechanical properties of natural structural loess in laboratory. Finally we validate the rationality and accuracy of the model by comparing model results with conventional triaxial test results.
• Select
  Classification of Swelling-shrinkage Grade of Expansive Soils Based on Cloud Model

  ZENG Zhi-xiong, TIAN Hai, HUANG Jue-hao

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 80-85. https://doi.org/10.11988/ckyyb.20140787

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Due to comprehensive effects of many factors on the swelling-shrinkage of expansive soils, it is difficult to determine the classification of the swelling-shrinkage grade in the process of expansive soil treatment. In this paper, five key factors were chosen as the assessment indexes to construct a cloud model and carry out the uncertain reasoning on the basis of the classification standards, and the qualitative comment of each assessment index was translated into quantitative value to achieve the transition from a qualitative concept to a quantitative data. Furthermore, according to the optimization theory, the objective weights were obtained by using twenty standard samples produced through stochastic interpolation in each grade interval. In association with the subjective weights, the combined weights were calculated. Finally, the new model was applied to practical projects in consideration of the combined weights and the uncertain reasoning, and the total scores and the swelling-shrinkage grades were acquired. Results show that the classification results fit well with the actual situation. The feasibility and applicability of the proposed model are verified. It offers reference to the classification of swelling-shrinkage grade of expansive soils in similar projects.
• Select
  Model Test Study on Landslide with Weak Layers under Uprise of Reservoir Water

  ZHAN Qing-hua, WANG Shi-mei, ZHAO Dai-peng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 86-90. https://doi.org/10.11988/ckyyb.20140884

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to study the impact of reservoir water level fluctuation on stability of landslide with weak layers, we carry out model test and measure the variations of soil pressure and pore water pressure as well as displacements of certain parts of the landslide body during reservoir water level fluctuation. Results show that as reservoir water level rises, slip resistance decreases due to immersion of reservoir water, stability of the landslide reduces, and displacement occurs in landslide. Impacts of reservoir water rising on landslide stability can be divided into three stages: stability phase, slow deformation phase and global glide phase. The three stages exhibits different characteristics, reflecting that the landslide stability decreases with reservoir water rising. Meanwhile, weak interlayer in the landslide is not only the weak part of the landslide, but also the crucial part for landslide stability.
HYDRAULIC STRUCTURE AND MATERIAL
• Select
  Slurry Diffusion in Grout-enriched Roller Compacted Concrete

  YAN Qiao, XU Feng, MO Shi-yuan, LI Liang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 91-93. https://doi.org/10.11988/ckyyb.20140854

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Grout-enriched roller compacted concrete (GERCC) is a kind of RCC for resisting dam seepage, by applying cement grout to normal RCC and vibrating compaction. To research the slurry diffusion in GERCC, we establish a grouting model and analyze main factors influencing the effect of grouting. According to test results of grouting diffusion and by using multiple regression analysis, we obtain the influence of each factor on the test results and the quantitative relationship among various parameters. Through correlation coefficient analysis of independent and dependent variables in the formula, we find that the grouting diffusion is closely correlated with the grouting pressure of material subjected to injection and the single-hole grouting volume as well as water-cement ratio of slurry. Finally, the research results can be referenced for construction and technique improvement of GERCC grouting.
• Select
  Mechanism of Waste Glass Powder in Concrete and Its ASR Risk

  LI Li-hua, REN Zeng-le, YANG Jun-chao, LIU Shu-hua

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 94-99. https://doi.org/10.11988/ckyyb.20140871

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Waste materials are widely used in civil engineering, and waste glass powder can be used as a supplementary cementitious material, which accords with the requirement of sustainable development of building materials. On the basis of a large number of literatures, the feasibility of adding waste glass in concrete is researched. Results show that, as a new potential auxiliary cementitious material, glass powder not only has some special effect on the hydration and hardening of composite cementitious material, but aslo has risk of alkali-silica reaction (ASR). As there is plenty of amorphous silicon dioxide in glass, alkali-aggregate reaction easily takes place, but glass powder can be used as active supplementary cementitious material. Furthermore, we present that waste glass which is grinded into powder can be used as auxiliary cementitious material and discuss the effect of glass powder on the hydration and hardening of composite cementitious material and its ASR risk. Grinding waste glass into powder not only reduces risk of alkali-aggregate reaction, but also promotes fly ash action of glass and improves performances of concrete.
• Select
  Prediction of Elastic Modulus of Concrete Based on Random Aggregate Model

  YANG Hua, LI Zong-li, HUI Hong-yi

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 100-105. https://doi.org/10.11988/ckyyb.20140583

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In the assumption at mesoscopic level, concrete materials are assumed as three-phase composites consisting of aggregate, mortar and the bonding interface between mortar and aggregate. In order to determine elastic modulus of concrete (EMC), on the basis of the assumption, we establish a random aggregate model in the two-dimensional plane with Monte Carlo method and Walraven formula. Meanwhile, we predict EMC by using finite element method and compare the numerical calculated results with test results to verify the effectiveness of this mesoscopic finite element model. Furthermore, we discussthe impacts of several parameters (elastic modulus, aggregate’s volume content , aggregate’s maximum size, aggregate’s gradation , interface thickness and pores) of mesoscopic component on EMC. Test results show that 1) as for mesoscopic components of concrete, impact of elastic modulus of mortar on EMC is the biggest; 2) under given conditions, EMC with continuous gradation is bigger than that with uncontinuous gradation; 3) EMC decreases with the increasing of interface thickness and the existence of pores. The research results offer reference for the design of concrete’s mix proportion and optimization of its mechanical properties.
• Select
  Cryogenic Performance of PTN Bitumen Polyurethane Joint Materials

  WU Meng-na , ZHANG Hui-li

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 106-110. https://doi.org/10.11988/ckyyb.20140797

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Through testing the hardness, tensile property and adhesive tensile property of PTN bitumen polyurethane joint materials with three different mix ratios at temperature from 20℃ to -100℃, we studied cryogenic performance of PTN material (consisting of component A and component B) under ultra-low temperature. Images magnified 5000 times were observed and analyzed by using scanning electron microscope (SEM). On the basis of this, the relationship between hardness and tensile performance was established to predict tensile performance of PTN material by non-destructive inspection method. Test results show that: 1) as component B increases, the hardness and the tensile strength decreases, whereas the elongation at break increases; 2)under given mix proportion, hardness and tensile strength increase with the decrease of temperature, but the elongation at break decreases; 3)at temperature below -60 ℃, hardness, tensile strength and elongation at break no longer vary with temperature, in other words, stagnation appears; 4)tensile bonding strength increases first and then decreases when temperature reduces, whereas adhesive tensile elongation at break decreases with the decrease of temperature until zero value occurrs at ultra-low temperature.
• Select
  Rate-dependent Constitutive Model of Concrete Based on the Statistical Theory of Weibull

  LIANG Hui, ZOU Rong-hua, PENG Gang, TIAN Wei, CHEN Xue-qiang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 111-114. https://doi.org/10.11988/ckyyb.20140695

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Through uniaxial compression tests under different strain rates(10^-5,10^-4,10^-3 and 10^-2/s), the mechanical properties of concrete are analyzed to obtain the material properties of concrete during operation. Results show that as strain rates increase, the peak stress and initial elastic modulus tend to increase, but the regularity of peak strain’s variation is not obvious. With strain rate sensitivity into consideration, a rate-dependent segmented constitutive model of concrete is established based on Lemaitre’s strain equivalent principle and the statistical distribution theories of Weibull and Lognormal. On the basis of test data, the model parameter is determined under different strain rates, and the curve of uniaxial compression stress-strain and the curve of damage variation are obtained. The results indicate that the rate-dependent constitutive model could reflect the whole process of the concrete’s damage of uniaxial compression under different strain rates.
INFORMATION TECHNOLOGY APPLICATION
• Select
  A Model for Error Distribution of Atmospheric Disturbance in Ground-based SAR on Account of Quadric Surface Fitting

  WANG Xue-qin, YUE Jian-pin, QIU Zhi-wei, SANG Jie

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 115-117. https://doi.org/10.11988/ckyyb.20140767

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Atmospheric disturbance effect is one of the major factors which affect the measurement precision of system of ground-based synthetic aperture radar (GBSAR). It is closely relevant to the changes of atmospheric environment, and it varies with time and space. By analyzing spatial-temporal variation characteristics of error of atmospheric disturbance, we introduce function of quadric surface to establish a distribution model for atmospheric disturbance. Moreover,we use ground control points to obtain parameters of the model and to estimate the error at any position of overall testing area. Results suggest that the error of atmospheric disturbance is reduced and the accuracy of GBSAR measured data is improved by using this model.
• Select
  Spatio-temporal Analysis of Vegetation Cover Change Based on MODIS data in Horqin District

  LI Sheng-yong , WANG Xiao-qing , LI Biao

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 118-122. https://doi.org/10.11988/ckyyb.20141015

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  China is a big country with broad vegetation cover and superior natural environment. As time changes, however, ecological system of part areas is seriously destructed, so it is very important to research on the change of spatial pattern of vegetation. Horqin district of Tongliao, located in Inner Mongolia, is taken as an example in this paper. By employing theories of time series, average method and interpolation method, and according to MODIS remote sensing data from 2004 to 2013 in the area, we analyze the spatial and temporal variations of NDVI in Horqin district, and conclude the vegetation cover in the district in the recent decade: 1) vegetation cover of the district shows tendency of increasing, with the increasing rate of 0.033/a, and good vegetation cover is in the following years: 2005, 2010, 2011, 2012 and 2013; 2) vegetation cover of west Liaohe river watershed is the highest among the whole Horqin district; 3) summer is the largest contributor to vegetation cover, with the increasing rate of 0.002 8/a. The results offer reference for theoretical study and decision making of ground ecological environment in Horqin district.
• Select
  Typical Faults in the Technical Reform of Monitoring and Control System for Ertan Hydropower Plant

  XI Guang-qing, ZHOU Yu, LI Yang-yang, WU Fa-lei, ZHOU Qi, ZHOU Sheng-wei, JIAN Zhen-yuan, SONG Yong-heng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 123-127. https://doi.org/10.11988/ckyyb.20140867

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In the process of technical renovation for the monitoring and control system, there are four typical faults: false alarm signals, abnormal data communication in dispatch communication system, slow data refreshing of the 101 communication protocol and AGC/AVC workstation crash. Through analysis, we found that these faults are caused by circuit electromagnetic interference, software bugs, ill-considered procedures, outdated firmware version and unreasonable allocation in calculation procedures, respectively. We can solve all the faults by strengthening circuit anti-interference ability and filtering signals in the program, removing program bugs , reasonably arranging the start-stop time and orders in processing sequence, optimizing process and strategies to reduce the amount of data sent and shorten the queues length, upgrading the firmware version, and optimizing the load distribution of calculation program to avoid halt of AGC/AVC workstation system. Results show that the measures are effective.
INSTRUMENTATION DEVELOPMENT AND TESTING TECHNIQUE
• Select
  Application of Constant α Control Method of Excitation Regulator in Shenwo Power Plant

  TIAN Bo, YANG Fa-hong

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 128-130. https://doi.org/10.11988/ckyyb.20140834

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In this paper, we introduce the control mode of excitation regulator with constant α. WL-06B double-microcomputer excitation regulator in Shenwo power plant of Liaoning province is taken as an example. By changing the induction generator from self-shunted type into separately-excited type, we carry out three-phase short-circuit test for steady-state characteristics of generator, and obtain characteristic curve of the test. Moreover, we obtain the three-phase current of stator winding by altering the control angle and excitation current of rotor winding. We can also determine the symmetry of three-phase current and identify short-circuit failures among windings of rotor by using the characteristic curve. The research results offer reference for similar tests in the future.
NUMERICAL MANIFOLD METHOD BASED ON INDEPENDENT COVERS
• Select
  Characteristics of Convergence and Cover Mesh in Numerical Manifold Method Based on Independent Covers

  SU Hai-dong, XIE Zhi-qiang, GONG Ya-qi, QI Yong-feng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 131-136. https://doi.org/10.11988/ckyyb.20150399

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The scope of a numerical manifold method (NMM) based on partially overlapping covers is narrowed to a special case based on independent covers. Convergence of the new method is discussed from two aspects: completeness and coordination. The convergence of the method is due to the convergence of each independent cover. Results show that the size of the strips between independent covers should be small. Moreover, the cover meshes have three excellent features: arbitrary shape, arbitrary connection, and arbitrary refinement. Finally, some illustrations are given to verify these “arbitrary” features, and the method can be used to greatly simplify the pre-processing of numerical analysis.
• Select
  Preliminary Study of Numerical Manifold Method Based on CAD Geometry

  CHEN Ji-zhan, SU Hai-dong, QI Yong-feng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 137-143. https://doi.org/10.11988/ckyyb.20150599

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The iterative process of design-analysis-redesign implies urgent requests of the integration of computer aided design (CAD) and computer aided engineering (CAE). In this paper, we present a numerical manifold method (NMM) based on CAD geometry: we can arrange mathematical meshes and set order of approximation functions according to the complexity degree of physical field distribution in CAE, which is more reasonable than isogeometric analysis (IGA) method. Through introducing automatic and fast cutting operations, we can realize direct modeling from CAD model to CAE model without modifications. Moreover, to solve the problem that curves on geometric boundaries are required to be discretized into line segments in present NMM, we put forward algorithms to cut the curves of geometric boundary with the lines of mesh boundary, hence preserving the shape of the geometric model in the procedures of CAE modeling and mesh refinement. Furthermore, as for the polynomial approximation functions usually used in NMM, we deduce analytical integral formula of “approximate” simplex with a curved edge and use it to obtain precise integral calculations of manifold elements with curved boundaries. Finally, we verify the feasibility of the method through an example of a circular hole in a plate. The research offers new thinking for the integration of CAD and CAE, and lays foundation for the automatic analysis from CAD models to CAE.
• Select
  Preliminary Implementation of Automatic Computation for Static Analysis of Structures Using NMM Based on Independent Rectangular Covers

  SU Hai-dong, GONG Ya-qi, XIE Zhi-qiang, QI Yong-feng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(2): 144-150. https://doi.org/10.11988/ckyyb.20150919

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  By means of numerical manifold method (NMM) based on independent rectangular covers proposed in previous study, we present an automatic computation method for static analysis of linear-elastic structures, including automatic pre-processing, self-adaptive analyses and so on. According to the characteristics of independent covers, we give 3 indexes for posterior error such as index of strain continuity in strip area between two covers, stress index on boundary surfaces and high-order error in an independent cover. By using convenient h-version mesh refinement and p-version order increasing in the new method, we implement h-p version self-adaptivity in a selected way to realize h-version refinement of rectangular covers by using simple bisection method. Some 2D numerical examples are given to illustrate the feasibility of automatic computation, in which all the procedures are automatically accomplished by the computer, except for necessary manual input of structural outlines, material parameters, and boundary conditions. Finally, we obtain calculated data with certain precision.