01 August 2018, Volume 35 Issue 8

    

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SPECIAL CONTRIBUTION
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  Investigation of Runoff Evolution at the Headwaters of Yangtze River and Its Driving Forces

  LI Qi-jiang

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 1-5. https://doi.org/10.11988/ckyyb.20180009

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  Evolution of hydrological cycle and water resources has been a hot topic for scholars and researchers around the world. This holds even more true in water source areas under changing environments. In this paper, the evolution characteristics of runoff in source regions of Yangtze River were investigated using statistical methods. On this basis, the impacts of both surface meteorological factors and upper atmospheric circulation factors on runoff were evaluated. Results show that runoff at Zhimenda station in the headwaters of Yangtze River distributed unevenly during a year, and a significant increasing trend is observed with regard to annual runoff. An obvious abrupt change in the year of 2004 was observed for runoff time series from 1956 to 2016. Wavelet analysis indicated that there were two significant periods of these time series, which were 7-8 years and 20-21 years, respectively. The biggest power of the spectrum was observed in the 42-43 year period. As for the impacts of different meteorological and atmospheric factors on runoff, our study indicated that precipitation was the leading driving force for runoff variation, and the role of water surface evaporation was also important.The variation of runoff was also influence by air temperature, but the effect was not significant enough. There was good agreement between monthly runoff observations of Zhimenda station and the Tibetan Plateau Index_B (TPI_B). Both the spatial distribution and magnitude of precipitation agreed well with the Tibetan Plateau vortex.
RIVER-LAKE SEDIMENTATION AND REGULATION
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  Preliminary Study on Joint Desilting Dispatching Mode of Xiluodu, Xiangjiaba and Three Gorges Cascade Reservoirs in Flood Season

  HUANG Ren-yong, WANG Min, ZHANG Xi-bing,LIU Liang,REN Shi,ZHOU Man

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 6-10. https://doi.org/10.11988/ckyyb.20170109

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  According to typical water and sediment processes, we calculated the joint desilting scheduling of Xiluodu, Xiangjiaba and Three Gorges cascade reservoirs in two modes, respectively: sediment peak regulation mode, and dynamic mode of “storing clear water and releasing muddy water” in flood season. Results revealed that the scheduling of cascade reservoirs in sediment peak regulation mode could improve, to a limited extent, the outbound sediment discharge of cascade reservoirs in qualitative sense; the dynamic mode of “storing clear water and releasing muddy water” in flood season is conducive to improving the outbound sediment discharge to a large extent. Furthermore, we proposed corresponding joint desilting schemes in sediment peak regulation mode and dynamic mode of “storing clear water and releasing muddy water” in flood season for Xiluodu, Xiangjiaba and Three Gorges cascade reservoirs.
WATER RESOURCES AND ENVIRONMENT
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  Assessment of Eco-environmental Impact of Small Dam-type Hydropower by Integrating Ecological Footprint and Analytical Hierarchy Process

  HUANG Zhuo,LIU Yue-xiao, WANG Zhen-hua,LI Qing-yun

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 11-16. https://doi.org/10.11988/ckyyb.20170192

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  Small dam-type hydropower project has negative impact on water resources and water eco-environment despite of electricity generation in substitution of firewood. Assessing the eco-environmental impact of dam-type hydropower is of crucial significance for a rational development of water resources and a coordinative relationship between hydropower construction and nature, economy and society of the drainage basin.In the present research, a comprehensive assessment model for small dam-type hydropower is established. An index scoring system is built by analytical hierarchy process and the weights of indexes are given according to ecological footprint. The applicability of the assessment model is examined by case study on a small dam-type hydropower station in northwest China.Results suggest that the model enhances the practicability and objectivity of assessment results, and also improves the comparability among different stations. It also provides a novel scientific approach for the objective assessment of eco-environmental impact of small dam-type hydropower.
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  Mid-term and Long-term Hydrological Forecasting of Snowmelt Runoff in Western Tianshan Mountains Based on Mutual Information and Neural Network

  ZHOU Yu-lin, MU Zhen-xia, PENG Liang,GAO Rui ,YIN Zi-yuan, TANG Rui

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 17-21. https://doi.org/10.11988/ckyyb.20170046

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  The aim of this research is to improve the accuracy of forecasting snowmelt runoff in the mountainous areas of western Tianshan Mountains, and to better support the development of industrial and agricultural production in the study area. The predictor, which is a key issue affecting forecast accuracy, are optimized and selected by using mutual information, correlation coefficient method, and principal component analysis method. The selected predictors are taken as input factors in RBF neural network model and combinatorial wavelet BP neural network model for comparison. Results suggest that: 1) optimized predictors selected by the mutual information method could improve forecast accuracy; 2) according to forecast results under different scenarios, the results of RBF neural network model is superior to those of combinatorial wavelet BP neural network model; 3) with relative error as the standard of accuracy evaluation, RBF neural network model with input factors selected by mutual information method could produce the optimum forecast result.
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  Index System of Water Ecological Civilization City: Perspectives and Suggestions

  HU Qing-fang, HUO Jun-jun, LI Ling-jie, WANG Yin-tang, CUI Ting-ting, LIU Yong

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 22-26. https://doi.org/10.11988/ckyyb.20170076

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  As a strategic issue in resources and environmental problems in the progress of rapid urbanization of China, water eco-civilization has received extensive concerns across all fields of the society. The index system for a water eco-civilization city is of guiding importance to construction, and is also an indispensable basis for evaluation. In this paper, the index systems for water eco-civilization city proposed by some pilot cities inclusive of Jinan and Suzhou, and two provinces including Shandong and Jiangsu, as well as the Ministry of Water Resources, are analyzed and compared. The main problems in these index systems are expounded. Finally, specific suggestions to improving the index system of water eco-civilization city are presented from aspects of effectiveness, completeness, normalization and evaluation methodology.
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  Detectability of Hydrological Response to Land Use Change

  ZHANG Tao, LIU Yu-ting, YANG Xin-yue

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 27-33. https://doi.org/10.11988/ckyyb.20170199

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  The hydrological response to land use change and the detectability of such response are researched in thispaper by SWAT model. The hydrological processes in Fujiangqiao catchment under two land use scenarios (1985and 1995) are simulated, and diagrams of land use conversion are obtained for analysis. Identical climate drivers are used in both scenarios to eliminate the effect of climate difference. Results reveal that no apparent hydrological responses are detected in spite of dramatic land use changes in Fujiangqiao catchment from 1985 to 1995. The similarity of hydrological effect of different land use types, the variation of hydrological effect of different land use types, the statistical compensation effect, and the statistical average effect are main reasons of the difficulty in detecting the hydrological responses. In view of this, a hydrological dynamic response degree is proposed to eliminate the statistical compensation effect, which helps researchers understand the degree of hydrological responses.
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  Engineering Design of Underground Reservoir Based on Sponge City Theory

  WANG Xing-chao

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 34-39. https://doi.org/10.11988/ckyyb.20170103

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  On the basis of summing up problems in current construction of sponge city, an idea of sponge city construction with underground reservoir system as city sponge is put forward. In line with the theory of sponge city, the holistic structure of underground reservoir system is described with seven systems as supporting project involving seepage, stagnation, storage, net, use, and discharge. The water circulation path of sponge city is dominated by such underground reservoir system. The sponge city project with urban water system as its core is of evident benefit for improvement of flood and water-logging control capacity, efficient utilization of water resources, and restoration of urban water ecological environment. The research provides a feasible technical support and effective guarantee of sound water circulation for sponge city construction.
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  Water Quality Assessment of Caohai Lake in Guizhou Based on Trophic State Index and Principal Component Analysis

  CHEN Li-hua, YU Ji-xin, LI Li, L Wen-qiang, ZHANG Jian-li

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 40-45. https://doi.org/10.11988/ckyyb.20170236

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  Eleven indicators of water quality in two areas of the Caohai Lake (Yangguanshan and the middle part) in Guizhou Province were measured seasonally in 2016. Trophic state index (TLI) and Surface Water Quality Standard (GB 3838—2002) were used to evaluate the trophic status of water quality, and principal component analysis (PCA) was conducted to assess the pollution level and main influential factors. Results demonstrated that: (1) The eleven indicators in both areas displayed significant seasonal variations, among which transparency and dissolved oxygen (DO) were highest in winter; while suspended solids (SPM) was highest in autumn. Except that in autumn, pH remained at about 8. TN, TP, NH₄⁺-N and COD_Mn were in 0.58-2.27, 0.032-0.072, 0.059-0.364 and 4.28-6.79 mg/L, respectively and Chl.a ranged from 5.62 to 9.95 mg/m³, with the highest TN in autumn, the highest TP in autumn and winter, and highest COD_Mn and Chl.a in summer and autumn. (2) The TLI of both areas were slightly higher than 50 in autumn, indicating slight pollution, while in other seasons, the TLI ranged between 30 and 50, implying medium trophic state. Evaluation results from GB 3838—2002 show that the water quality in Yangguanshan belonged to class Ⅱ and Ⅲ, except for a few occasions; whereas in the middle part, the water quality was mainly class Ⅱ and Ⅳ. TN and COD_Mn were major influential factors, while TP and NH₄⁺-N were at level Ⅱ throughout the year. (3) Principle component analysis revealed that the most important influencing factors of water quality in Yangguanshan were ions, nitrogen, organic matter, DO and Chl.a, while in the middle part were Chl.a, NH₄⁺-N, SD, EC, TP, DO, WT and SPM. In conclusion, nitrogen and organic matters are the most important influencing factors and the fundamental causes of water quality in Yangguanshan and the middle part of Caohu Lake. Controlling the inputs of external nitrogen and organic matters would be the key to improving the water quality in Caohai Lake.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  Case Analysis of the Prediction Ability of SVM-based Monitoring Model for Concrete Dam Deformation

  QIAN Qiu-pei, CUI Wei-jie, BAO Teng-fei, LI Hui

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 46-50. https://doi.org/10.11988/ckyyb.20170062

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  Dam deformation is nonlinearly correlated with water level, temperature, aging and many other factors. Support vector machine (SVM) is of great superiority in dam safety monitoring as it accommodates small sample, nonlinear and high dimensional learning problems. In this article, the principle of SVM is expounded, the procedures of building an SVM-based deformation monitoring model are summarized, and parameter optimization method is introduced as well. The prediction ability of the SVM-based monitoring model for concrete dam deformation is analyzed through a case study. Results demonstrate that the short term prediction ability of the model is better than its long term prediction ability; the prediction ability is affected by the number of prediction sets rather than by algorithm optimization. The results indicate that selecting an appropriate number of prediction sets is important to the validity of the model.
HYDRAULICS
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  Pressure Characteristics of Dual Jets under Wave Action

  SHEN Xiao-xiong, SONG Jing-xian, LI Jia

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 51-55. https://doi.org/10.11988/ckyyb.20161218

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  Disposal of sewage into the oceans is a typical jet movement. As jet flows, the reciprocal motion of water generated by waves obviously restricts the formation and development of jet. However, less research has been done to study the interaction between jet and waves. In this article, physical model test of dual jets under wave action is conducted by using digital pressure sensor to analyze the pressure distribution and axial attenuation law of dual jet cross-section under wave action. The experimental results show that the pressure distribution of dual jets cross-section under wave condition is similar to that in hydrostatic condition, but the jet pressure under wave condition is larger than that under hydrostatic condition; the larger the wave period is, the greater the pressure peak value increases. The development of the dual jets has undergone single-hole-dominated, double-hole jet adsorption and blending, as well as merging processes. In the single-hole-dominated zone, the distribution of jet pressure is similar to that in hydrostatic condition; in the adsorption and blending zone, pressure attenuation in the holes varies, namely, pressure attenuation in the first hole is similar to that of single-hole jet, and the second hole smaller than that of the first hole; in the merging zone, the dual jets merge into one, with the hydrodynamic characteristics similar to that of a single-hole jet. Moreover, wave has a positive effect on the blending of dual jets, and the effect intensifies with the elongation of wave period, which also makes the jet merge section appear earlier, indicating that wave period has a significant influence on jet pressure.
ROCK-SOIL ENGINEERING
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  Statistical Analysis of Dynamic Shear Modulus Ratio and Damping Ratio of Soils in Jinan City

  SHANG Jin-hua, XU Xi-yong, WANG Guo-fu, MA Xian-feng, YANG Lin-de

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 56-60. https://doi.org/10.11988/ckyyb.20170098

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  With seismic evaluation in the construction of Ji'nan subway as research background, dynamic triaxial tests of typical soils are carried out and the test results are statistically analyzed. Results imply that, in the same soil layer, with the increase of shear strain, dynamic shear modulus ratio decreases, whereas damping ratio increases. However, the test data is discrete. Dynamic constitutive model of soil is of good effect in fitting the test results. Compared with research results in other areas, the dynamic shear modulus ratio of soils in Ji'nan City is large, while damping ratio is small, indicating that the dynamic properties of soils in Ji'nan is favorable for earthquake resistance. This study not only helps to understand the dynamic properties of soils in Ji'nan, and also provides reference for engineering seismic design.
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  Impact of Freezing Temperature on Mechanical Properties of Loess under Cyclic Freezing and Thawing

  WEI Yao, YANG Geng-she, YE Wan-jun

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 61-66. https://doi.org/10.11988/ckyyb.20170188

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  Researching the freeze-thaw cycle, freezing temperature and freezing rate is of vital significance for engineering prevention of freezing-thawing hazard of loess. In this paper, the changes in unconfined compressive strength, shear strength, and compressibility of loess samples after a single freezing-thawing cycle at different freezing temperatures were studied. Samples of different moisture contents were frozen at 0, -5, -10, -15, -20 ℃ in a closed environment, respectively, and then heated at 15 ℃. Results showed that after freezing and thawing at different freezing temperatures, the unconfined compressive strength of loess with different water content decreased; and the lower the freezing temperature, the faster the unconfined compressive strength decreased. The cohesion of soil samples with different moisture contents also exhibited a tendency of decreasing with the drawdown of freezing temperature. The friction angle of loess decreased firstly and then increased within a range between 0° and 2°. For loess with 14% and 26% moisture content, the increment in compression coefficient was larger than 0.1 MPa^-1 under -20 ℃ freezing temperature, while under other low temperature conditions, the changes in compression coefficient were slight; whereas loess of 18% and 22% moisture content showed a more uniform fluctuation with the decrease of freezing temperature, with the fluctuation value in the case of adjacent negative temperature did not exceeding ±0.1 MPa^-1.
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  Model of Multicomponent Contaminants Diffusion in Consideration of Components' Activity

  JU Zhan-ying, ZHANG Zhi-hong

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 67-71. https://doi.org/10.11988/ckyyb.20170111

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  Compacted clay liner system with isolation and barrier function used in solid waste disposal is of low permeability. Diffusion, as a consequence, is the dominant pattern of leachate solute migration in the clay liner. In engineering practice, multicomponent contaminants coexist in the leachate of storage yards. In view of this, the diffusion law of multicomponent solute in the impervious clay liner is researched. An equation of multicomponent contaminants diffusion in clay liner is built by introducing the coefficient of activity which reflects the effective concentration of components based on the principle of linear momentum balance. Numerical solution is calculated by finite element software COMSOL Multiphysics. Results show that the introduction of coefficient of activity has hindered the transport progress of individual component. The results could be regarded as theoretical basis when designing economic and reasonable impervious barrier for storage yards.
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  New Grouting Slurry for Filling Goaf: Solidification Mechanism and Influential Factors

  ZHAO Xian-hui, LIU Chun-yuan, ZUO Li-ming, LIU Yu-fei, PANG Yun-ze

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 72-77. https://doi.org/10.11988/ckyyb.20170197

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  Soda residue, fly ash and sodium silicate solution have been synthesized as a new grouting material for filling goafs. In the present research, the solidification mechanism is explored by methods of scanning electron microscope and mutual blending. Moreover, the impacts of mix ratio, sieving particle size of soda residue, and curing condition on engineering indicators (compressive strength, setting time, and stone rate, among others) are examined by tests. Results demonstrate that the early solidification of slurry is determined by the calcium silicate hydrate gel (C-S-H) generated by calcium components of soda residue reacting with sodium silicate solution; and the later strength increment is determined by aluminosilicate polymer gel (N-A-S-H) formed by alkali-activated class F fly ash. The mix ratio of raw materials significantly affects the engineering properties of the slurry. With the shrinkage of sieving particle size of soda residue, the fluidity, setting time, and stone rate decrease, whereas compressive strength increases. Particle size 0.5 mm is the threshold for the increment of strength cured for 28 days. High temperature and humidity is favorable for the solidification process of slurry.
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  Reliability Analysis of Slopes Based on Extreme Learning Machine

  SONG Yong-dong, SU Li-jun, ZHANG Chong-lei,SUN Chang-ning, QU Xin

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 78-83. https://doi.org/10.11988/ckyyb.20170132

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  As the limit state function of slope can't be explicitly expressed,conventional methods for slope reliability analysis are disadvantageous for difficulties and cumbersome calculation. A method for slope reliability analysis is proposed by combing the finite difference method of FLAC^3D and the extreme learning machine (ELM). Samples of random variables are generated through uniform experimental design, and the safety factors of these random variables are calculated through the strength reduction method of FLAC^3D. The mapping relationship between safety factors and random variables are obtained to construct the response surface function through the powerful fitting ability of ELM. Furthermore, a large number of random numbers generated by Monte-Carlo method are introduced into the function fitted by ELM to calculate the failure probability and reliability index of slope. Comparison with other methods through case study manifests that the proposed method is easy to be realized with reliable result.The research result provides a new approach for reliability analysis of slope, which is of broad application prospect.
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  Creep Behavior and Constitutive Model of Mudstone under Different Temperature and Stress Fields

  YUAN Qian-sheng

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 84-89. https://doi.org/10.11988/ckyyb.20170013

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  To explore the creep mechanical behavior of mudstone under different temperature and stress fields, we carried out triaxial step-loading creep test on mudstone at room temperature (25 ℃), 60 ℃ and 120 ℃, and built a constitutive creep model in consideration of damage and temperature effect according to the obtained creep curves and creep parameters under different temperature and stress fields. Results show that high temperature promoted the internal molecular motion of mudstone, weakened the mutual cementitious force between particles, and made the creep characteristic more obvious; confining pressure inhibited the internal damage development of mudstone to some extent. Steady creep rate increased in an exponential function with the rising of deviatoric stress and temperature; but reduced linearly with the increase of confining pressure. Under each temperature field, the long-term strength and the long-term shear strength parameters of mudstone increased in a good linear relationship with the increase of confining pressure; under the same confining pressure, however, the long-term strength weakened with the rising of temperature. The constitutive creep model coupling heat-mechanical effect on the basis of classic Nishihara model could well simulate the creep behaviors of mudstone under temperature and stress fields. Fitting results suggest that the elastic modulus and viscosity of mudstone reduced linearly with the rising of temperature, while α increased with the rising of temperature.
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  Anti-erodibility of Loess Subgrade Slope Reinforced with SH-Polymer and Inorganic Material

  LI Chong-qing, LIU Qing-bing, XIANG Wei, WANG Jing-e, QIAO Yu

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 90-94. https://doi.org/10.11988/ckyyb.20170221

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  Loess subgrade slope is subjected to erosion under heavy rain,which is detrimental to highway mainte-nance and driving safety.The anti-erodibility of loess slope reinforced by SH-polymer,cement,and lime,respectively, are examined comparatively through artificial rainfall test. Indicators inclusive of runoff start time, total sediment yield, and total runoff volume are quantitatively evaluated, and the effect of different soil stabilizers on anti-erodibility is analyzed. Results reveal that a 8% concentration of SH-polymer could reduce sediment yield and sediment yield rate to the optimum; yet increasing the concentration over 8% makes no further obvious contribution. Cement and lime are superior than SH-polymer in reducing sediment yield rate and sediment yield volume, but would also reduce the permeability of slope remarkably, bring about runoff in advance and larger runoff volume. By combining the three stabilizers, the shortcomings of each single stabilizer can be compensated, and the anti-erodibility of loess subgrade slope can be improved comprehensively.
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  Effect of Calcium Hydroxide and Anionic Polyacrylamide on Consolidation of Slurry of High Water Content

  HU Ting, WU Ya-jun, XU Fang

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 95-101. https://doi.org/10.11988/ckyyb.20170213

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  In an attempt to accelerate the drainage consolidation of soft soil of high water content, calcium hydroxide and anionic polyacrylamide (APAM) were mixed into the slurry of high water content in the borehole at a construction site in Shanghai. The optimum dosages of calcium hydroxide and APAM were determined according to the laws of slurry porosity, consolidation coefficient, and permeability coefficient varying with load obtained by one-dimensional oedometer test. Furthermore, vacuum preloading model test was conducted on the slurry modified with calcium hydroxide and APAM of optimum dosages. Results show that: (1) In one-dimensional oedometer test, the consolidation coefficient and permeability coefficient of modified waste slurry both increased, which accelerated the drainage consolidation. (2) In the meantime, the optimal dosage of calcium hydroxide and APAM solution with 0.2% mass fraction is about 0.8% and 11.2% mass fraction of the waste slurry, respectively. Beyond that optimum dosage, the consolidation coefficient and permeability coefficient both declined. (3) During vacuum preloading, the consolidation coefficient of waste slurry modified by calcium hydroxide increased evidently, with its average radial coefficient of consolidation 5.1 and 7.2 times of that modified by APAM and original slurry, respectively; the average radial coefficient of consolidation of the waste slurry conditioned with APAM is 1.4 times of that of the original waste slurry. In conclusion, the drainage consolidation of slurry can be effectively accelerated by adding calcium hydroxide combined with vacuum preloading.
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  Stability Analysis of Seasonal Frozen Soil Slope under Cyclic Freezing and Thawing Test

  CUI Guang-qin, SHANG Zhi-cheng, QIN Di

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 102-105. https://doi.org/10.11988/ckyyb.20170176

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  Baotou city of Inner Mongolia is a typical region with seasonal frozen soil where frost heaving and thawing is the main cause of frozen soil damage. The influence of cyclic freezing and thawing on the shear strength of silty soil was investigated by establishing the quantitative relationship of cohesion and internal friction angle against freeze-thaw cycle parameters. Moisture content, dry density, and number of freeze-thaw cycle were controlled in the test. Results showed that cohesion decreased steadily as cyclic freezing and thawing proceeds regardless of dry density and moisture content of soil specimen; internal friction angle stabilized with the proceeding of cyclic freezing and thawing, fluctuating within a range of 5°; shear strength of silty soil was mostly affected by cohesion. In addition, finite element analysis was carried out with geotechnical software, and the safety factor of slope was calculated by the reduction coefficient method. The research is expected to offer better theoretical basis for researching the seasonal frozen soil in Baotou.
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  Safe Distance Between Subway Tunnel and Peripheral Karst Caves in Wuhan

  GAO Tan, ZHOU Chuan-bo, QU Ruo-feng, WU Hong-bo

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 106-111. https://doi.org/10.11988/ckyyb.20170578

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  Karst caves in Wuhan are featured with shallow buried depth, small height, and high-head groundwater. Through numerical orthogonal test by MIDAS GTS, the significance of five major factors affecting the safe distance between the tunnel of Wuhan metro line 27 and the hidden karst caves is examined. The five major factors involve surrounding rock level, lateral pressure coefficient, span of cave, ratio of height to span of cave, and permeability coefficient. Results suggest that surrounding rock level and span of cave have significant impact on the safe distance between tunnel and cave whether the peripheral cave is located below, lateral to or above the tunnel, while permeability coefficient has no significant effect. Lateral pressure coefficient has a significant effect only when the peripheral cave is located beneath the tunnel. The ratio of height to span of cave has a significant influence only when the peripheral cave is located lateral to the tunnel. In association with nonlinear multiple regression analysis on the results, formulas for estimating the safe distance between tunnel and cave when caves are located below, lateral to and above tunnel are obtained. Case study proves that the proposed formulas are reliable.
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  Long-term Stability of Open-pit High Slopes with Gently-inclined Soft Interlayers

  YAO Yuan, JIAN Wen-xing, LI Li-chen, WANG Lu, MA Chong

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 112-116. https://doi.org/10.11988/ckyyb.20170728

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  The stability of a high slope containing gently-inclined soft interlayers in Esheng open-pit limestone mine was analyzed by using Burgers rheological model based on conventional mechanical test parameters and rheological parameters obtained by inversion of cyclic shear rheological test. Results demonstrate that Burgers rheological model is able to describe the rheological property of the argillaceous soft interlayers in Permian formation. Simulation results based on the Burgers rheological model revealed the failure of high slope and a high fitting degree between simulated displacement and field-monitored displacement, indicating that the rheological property of soft interlayers plays a dominant role in the failure of high slopes. In conclusion, compared with traditional limit equilibrium method and strength reduction method, Burgers rheological model is more appropriate in researching the long-term stability of high slopes containing gently-inclined soft interlayers.
HYDRAULIC STRUCTURE AND MATERIAL
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  Effects of Curing Materials on Strength,Crack Resistance and Mesostructure of Concrete

  LI Qiang,WANG Qi-cai,ZHANG Rong-ling,DAI Jin-peng,XIE Song-lin

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 117-121. https://doi.org/10.11988/ckyyb.20170241

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  In an attempt to explore the most suitable curing material for the development of concrete in cold and dry environment with large temperature difference, we analyzed the compressive strength, crack resistance and microstructure of concrete cured by curing agent, rubber sheet and geotextile, respectively, and compared the properties with those under natural condition. Results revealed that in comparison with concrete cured under natural condition, (1) concrete cured with curing agent has inferior compressive strength but superior crack resistance, and in a mesoscopic sense, larger porosity and average chord length but smaller void spacing factor which are used to characterize the pore structure of concrete; (2) concrete cured with rubber sheet has better compressive strength but lower crack resistance, and in a mesoscopic sense, smaller porosity and average chord length but larger void spacing factor; (3) concrete cured with geotextile is endowed with the advantages of the abovementioned two curing methods, with enhanced crack resistance, porosity, average chord length as well as void spacing factor despite no big change in compressive strength, indicating that concrete cured with geotextile is of sound durability. In conclusion, among the four curing methods, geotextile is the most favorable for concrete development in cold and dry environment with large temperature difference.
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  Experimental Study on Cracking Resistance of Concrete in Dry and Cold Regions with Strong Wind

  KANG Jian, LIU Jian-xun,ZHANG Rong-ling, ZHAO Wen-bin, ZHAO Yong-peng

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 122-127. https://doi.org/10.11988/ckyyb.20170032

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  To investigate the anti-cracking performance of concrete in dry and cold region with strong wind, we performed in-situ tests on C35 and C50 concrete anti-cracking rings and concrete bridge piers by changing environmental and external curing conditions. By comparing the cracking age and cracking width of the two strength-levels of concrete, we found that 1) concrete of larger strength level is more susceptible to cracking; 2) among different curing methods, maintaining heat and humidity has the optimum effect in preventing cracking for concretes of the same strength level; 3) while for concretes of different strength levels cured by the same measure, high-strength concrete is prone to cracking. Therefore, curing methods for low-strength grade concrete may not be suitable for high grade concrete which requires optimized measures.
INFORMATION TECHNOLOGY APPLICATION
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  Information Extraction for River System Based on Characteristics and Rules:A Case Study on Information Verification of River Chief System in Yichang

  ZHOU Xiao-ming

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 128-131. https://doi.org/10.11988/ckyyb.20180441

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  With the assistance of high resolution remote sensing image data, an object-oriented recognition model for river system information is proposed. This model summarizes the characteristics of water information in image, and defines the rules and its sub-characteristics in detail. Moreover, an experiment for water system information extraction is conducted for Yuan'an County, Yichang City as a case study. Result demonstrates that the proposed model could extract the river system features on remote sensing images effectively, and therefore is more accurate in identifying water system in comparison with conventional classification methods. The present research is helpful in improving the automation and accuracy of river information extraction and verification for the promotion of river chief system.
INSTRUMENTATION DEVELOPMENT AND TESTING TECHNIQUES
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  Modeling the Dynamic Performance of Hydraulic-Mechanical-Electrical System in Hydropower Station

  CAO Chun-jian, FANG Jie, HUANG Jing-qian, WANG De-lou

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 132-138. https://doi.org/10.11988/ckyyb.20170140

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  In order to investigate into the dynamic response of hydraulic-mechanical-electrical system (HMES) in hydropower station under disturbance, we established the Simulink models of main parts of HMES by the user-defined modeling function of MatLab/Simulink software, and further built a complete dynamic simulation model of the HMES in line with its basic structure and operating characteristics. By using the model, we simulated the dynamic response of HMES in isolated and grid-connected operation modes under various disturbances including load disturbance, power regulation disturbance, and short-circuit fault disturbance. The simulation results show that the proposed model could describe the dynamic responses of HMES under disturbances accurately. The model can be taken as a reliable simulation platform for studying the coupling mechanism of HMES and tuning of controller parameters.
CONSTRUCTION AND MANAGEMENT OF WATER CONSERVANCY PROJECTS
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  Evaluation Criteria and System of Green Small Hydropower

  PENG Yu-zhi, ZHOU Xin-rui,YU Jiang,ZHU Xin

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 139-144. https://doi.org/10.11988/ckyyb.20170233

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  Compared with large hydropower station, small hydropower station costs less, brings about less environmental damage, and plays an important role in the power consumption, river harnessing and the local social and economic development of remote areas in Southwest China and the minority areas. However, excessive and disorderly development of small hydropower also has impact on the river ecosystem. At present, a large number of small hydropower stations in operation are being inspected by the national sustainable green development program. China has put forward the Green Small Hydropower Evaluation Criteria (Draft) (hereinafter referred to as the “standard”), as a reference for the evaluation and certification of green small hydropower stations. By analyzing the “standard” and the favorable experiences of representative green hydropower standards abroad, we elaborated on improving the evaluation criteria of green small hydropower from aspects of evaluation content, index system and evaluation period. In view of the lack of strict certification body and powerful supervision approach, we discussed about the establishment of reward and punishment system in terms of policy promotion, incentive mechanism, restraint and punitive measures.
TECHNOLOGY FOR UNDERGROUND WATER-SEALED CAVERN OFZHANJIANG NATIONAL CRUDE OIL STORAGE PROJECT
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  Influence of the Distance Between Fault Fracture Zone and Cavern on the Stability of Underground Water-sealed Oil Storage Cavern

  LIU Peng,ZHAO Qing,CHEN Yi-lei,JIN Wu

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 151-153. https://doi.org/10.11988/ckyyb.20180470

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  Underground water-sealed caverns are usually excavated in granite and other hard rock masses where defective geological structures such as faults and joints develop well. In an attempt to investigate into the influence of fault fracture zone on the stability of underground cavern, we examined the displacements of surrounding rock and typical sections in FLAC^3D with varying distance between fault fracture zone and cavern. The conclusions are as follows: (1) The location of fault fracture zone has great influence on the stability of surrounding rock of adjacent side wall, but has little influence on the stability of surrounding rock of distant side wall; (2) When the distance between fault fracture zone and cavern exceeds half of the cavern span, the influence of fault fracture zone on the stability of surrounding rock can be neglected. The conclusions are of guiding importance for determining the safe distance and selecting the location of such caverns.
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  Experimental Study on Durability of Grouting Material Composed of Cement and Water Glass for Underground Water-sealed Cavern

  SHAO Xiao-mei, LU Qi-bo, LI Fa-quan

  Journal of Changjiang River Scientific Research Institute. 2018, 35(8): 154-158. https://doi.org/10.11988/ckyyb.20180570

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  In the aim of supporting the engineering application of grouting material in underground water-sealed cavern at Zhanjiang national petroleum storage project, we conducted tests on the sulfate corrosion resistance, freezing thawing resistance and drying shrinkage of grouting material composed of cement and water glass(sodium silicate)in line with current test standards. The cement-sodium silicate grouting material used in the tests were designed at different mix proportions. A large number of sample results showed that after corrosion resistance test, the loss rate of cement-sodium silicate grouting material's rupture strength was higher than -50%; after freezing thawing test, the loss rate of compressive strength at optimum mix ratio was less than 25%, and the mass loss rate was less than 3%; the drying shrinkage rate of grouting material with optimized mix ratio at the 56^th day was less than 7%. In addition, the quality control requirements for cement-sodium silicate grouting material were discussed by analyzing the fluctuation of durability under different parameters.