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01 March 2016, Volume 33 Issue 3
    

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    RIVER-LAKE SEDIMENTATION AND REGULATION
  • YAN Xia, CHEN Li, YAO Shi-ming, JIN Zhong-wu, DENG Cai-yun
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 1-4. https://doi.org/10.11988/ckyyb.20141008
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    Luxikou reach is a typical goose-head braided channel in the middle and lower reaches of Changjiang River. Before the impoundment of the Three Gorges Project, channel evolution shows periodic tendency due to flow deflecting caused by single-side node in inlet of channel and bend circulation effect. After the impoundment, the evolution regularity of scouring and silting changes under the influences of water and sediment in upper reach and human activities. According to theoretic analysis and measured data, we carry out research the periodic evolution of Luxikou goose-head braided reach. The results show that periodic evolution still exists, and adjustment of scouring and silting even speeds up due to the decrease of incoming sediment from upstream. Furthermore, the head of Xinzhou sandbar suffers severe erosion, and erosion ditch occurs. Meanwhile, sediment deposition is serious in the inlet of Zhigang, which leads to adjustment of flow distribution pattern and bad channel condition. After the implementation of artificial waterway engineering, the river regime gradually tends to be stable , but the inherent effect on cyclical evolution of river reach still exists, bringing out a negative effect on navigation conditions and regulation projects.
  • WU Zhang-song , ZHANG Gen-guang , LIANG Zong-xiang, XING Ru
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 5-8. https://doi.org/10.11988/ckyyb.20140868
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    Pycnometer method has been widely used in sediment concentration measurements such as river hydrological measurement, model test of river engineering, evaluation of water quality and water intake in industry and agriculture. However, when sediment concentration is low, the sediment concentration measured by pycnometer method is usually greater than the actual value because the content of dissolved matter is big. In face of such phenomenon, test engineers often doubt error of test instruments or test process, but can’t find the real reasons. Through the sediment concentration measurement of desilting basin test of water supply in a city, we found that the content of dissolved matter in the water is crucial to the measurement error of low sediment concentration; nevertheless, temperature greatly affects sediment concentration, and the smaller the sediment concentration is, the bigger the effect of temperature error is. On this basis, we put forward the improved pycnometer method to measure low sediment concentration, and test results by the method is basically consistent with those by drying method. Finally, it can provide reference for test with low sediment concentration.
  • ZHAO Yan-bo, YOU Yong, LIU Jin-feng, LIN Xue-ping, LIU Shu-liang
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 9-13. https://doi.org/10.11988/ckyyb.20140919
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    Window-frame dam is a common measure in debris flow prevention engineering. The function of changing sediment size distribution is one of the main factors in the design of window-frame dam, and is also an urgent issue to be solved. In order to improve the design methods, we conduct a series of experiments to research the function of changing sediment size distribution of window-frame dam. Results show that 1) window-frame dam has a function of trapping coarse sand and discharging fine sand, and this function has a worst performance for viscous debris flow compared with trapping sub-viscous and intermediate debris flow; 2) we put forward the concept of critical particle size for the first time and give a variation range of critical particle; 3) the critical particle size and its variation range were affected by the density of debris flow and the type of window-frame dam (totally blocked, partially blocked, and open dams); 4) the critical particle size increases with the increase of density of debris flow for the same window-frame dam.
  • WATER RESOURCES AND ENVIRONMENT
  • ZHOU Yan-lai, CHEN Jin, XU Ji-jun
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 14-18. https://doi.org/10.11988/ckyyb.20140910
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    In order to explore the influence of uncertainty of flood on design of characteristic flood level for dam, we derive probability distribution of characteristic flood level (CFL) for dam by using stochastic differential equation for calculation of flood regulation. Three Gorges reservoir is selected as a case study. The uncertainty of flood is transformed into that of CFL so as to analyze probability distribution of CFL through calculation of flood regulation. On this basis, we recheck the CFL of Three Gorges reservoir. The results show that, 1) reliabilities of design flood data and original exceptional flood level (180.4 m) increase with the increase of sample size; 2) under sample size of 120a, reliability of design flood data and reliability of CFL are 93.19% and 99.17%, respectively. Finally, the research results provide theoretical basis for improvement in safety design of dam reservoir.
  • PENG Wei, HUO Jun-jun, XU Ji-jun
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 19-22. https://doi.org/10.11988/ckyyb.20141052
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    According to runoff data at main hydrological stations in Poyang Lake watershed from 1957 to 2012, we analyze the trend and periodic variation of incoming runoff in dry season by using Mann-Kendall test and wavelet analysis. The variation law is important for us to utilize water resources and protect water ecological environment. Test results show that from 1957 to 2012, runoff of each station shows an increasing trend in dry season, with mean increased margin of 0.199 per year, especially for runoffs in Wanjiabu station, Meigang station and Hushan station under significance level of 0.1; furthermore, runoff at each station in Poyang Lake watershed has obvious periodic features, with main period of 21a, as well as other notable periods such as 5a, 12a, and 28a. This research offers reference for hydraulic construction, ecological environment protection, and rational utilization of water resources in the watershed.
  • FIELD INVESTIGATION AND OBSERVATION
  • CHEN Jin, XU Zhen
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 23-28. https://doi.org/10.11988/ckyyb.20160021
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    The determining of river’s headstream has always been controversial. According to the findings of several important recent scientific investigations, we analyse the causes of controversy in determining the river sources of Yangtze River, Yellow River and Lantsang River. Moreover in line with the methods of determining the river sources of international famous rivers, we explore the principles and methods of determining river source. We conclude that river length, direction, flow, watershed area and river regime are natural factors to determine the river source. At present the focus of controversy lies in the main factor. We suggest river length and direction as the main factors, flow and river regime as secondary factors, and conventional custom and cultural factors also have important influence on the determination.
  • ZHOU Yin-jun, YAN Xia, JIN Zhong-wu, LI Zhi-jing
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 29-34. https://doi.org/10.11988/ckyyb.20150835
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    Lantsang river source is located in the north Tanggula Mountain of Qinghai-Tibet Plateau, nearby the south source of the Yangtze River, with hardly any human activities. In order to gradually recognize Lantsang river geomorphology and obtain basic data of geomorphology evolution of river, as well as scouring and silting process of riverbed, we carry out in-situ investigation and collect data and images to judge the river pattern of Moyun reach in Zhanaqu river, west source of Lantsang river. The results show that, boundary constraints of Moyun reach are weak with poor stability of riverbed; furthermore, in the classification system of river pattern which consists of 4 kinds, namely straight, meandering, anabranching, and wandering, we uniformly determine the reach is wandering type by using different discriminants; meanwhile, in the classification system of river pattern with 3 kinds, including straight, meandering and braided, we regard the reach as braided type; finally, according to domestic river characteristics and current classification system, we conclude that Moyun reach is wandering type. Field observation data and river pattern discrimination offer reference for further research on the river geomorphology of Lantsang river source.
  • LI Zhi-jing, JIN Zhong-wu, ZHOU Yin-jun, YAN Xia, XU Ping
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 35-37. https://doi.org/10.11988/ckyyb.20150854
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    Dangqu River, the south source of Yangtze River, is less studied by researchers due to plateau swamp and poor transportation. The basic characteristics of flow and sediment and its impact on water system of river source are little known to the outside world, with few research results of river evolution and transportation characteristics of flow and sediment. In order to obtain fundamental behaviors such as waterways, flow and sediment of Dangqu, as well as typical landform, researchers in Yangtze River Scientific Research Institute organized scientific investigation for Dangqu River again in 2015. The previous scientific investigation was done in 2014. The investigation results can be used as basic data for river evolution and ecosystem at river bank in plateau, and can be referenced for the harnessing, ecological protection and restoration of other rivers.
  • FAN Lei, ZHANG Qi
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 38-41. https://doi.org/10.11988/ckyyb.20150398
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    Jinsha River, upper reach of Changjiang River, is located in the transition zone of the southeast Qinghai-Tibet Plateau, Yunnan-Guizhou Plateau and Sichuan Basin. In this area, geological environment is variable with intense neotectonics movement, fragile ecosystem and frequent landslides. In order to study the occurrence and distribution characteristics and its influencing factors, we take Suwalong-Benzilan reach of the Jinsha River as a case study. Through field geological investigations and existing data, we analyze 32 landslides in the reach. The research results are shown as follows: 1) the spatial distribution of landslide is uneven, mainly in four regions, namely Wangdalong, Maoding, and Simuda in the mainstream of Jinsha River, and Guxue township in the branch of Jinsha River; 2) landslides are mainly huge and large-scale types whose attitudes are in agreement with deep bedrock, but few landslides exist in quaternary deposits;3) landslides at Suwalong-Benzilan reach of the Jinsha River formed in earlier geological ages, and elevation of shear outlet of the landslides is higher than that of water level of the river due to intensive neotectonic movement and rapid river incision rate; 4) landslide is relevant to geological environment conditions such as landform, lithologic character, geologic structure and river bank structure, in particular, landslide disasters easily occur in conditions of mountain bodies with 30° to 35°slope gradient, greenschist and ophiolite rock mass, fault areas within 1 kilometer and normal river bank slopes.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • ZHANG Yuan-sheng, LI Zhen-hua, WU Qing-liang, BAO De-rong, CHAI Jin-fei
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 42-47. https://doi.org/10.11988/ckyyb.20141021
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    Baiyun obo iron mine is the main raw material site of Baogang group, and is famous for rare earth in the world. Slope monitoring is crucial to the production and safety of the mine. In this paper we present the microseismic monitoring system in the east mine of Baiyun Obo. Through laying out detectors and installing main and branch stations as well as wireless devices, we carry out slope microseismic monitoring in regions of A, B and D on different platforms. Furthermore,we collect and analyze the monitoring data by using the system, accurately locating within the interior slope. In association with 3D displaying software, we directly obtain the locations and released energies of fracturing points of rock mass, realizing real-time monitoring in quarry slope. The results show that at present, region B and adjacent areas between region D and region C are dangerous areas, for microseismic events of these areas are more than those of other areas. We should take special measures to prevent accidents in these areas. Finally, the system can be taken as reference for safety operation and slope treatment.
  • ROCK-SOIL ENGINEERING
  • ZHOU Yong-qiang, SHENG Qian, LENG Xian-lun, FU Xiao-dong, LI Long-fei
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 48-53. https://doi.org/10.11988/ckyyb.20140851
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    Based on the statistical theory and damage theory, we establish a statistical damage model under triaxial compression in consideration of residual strength and damage threshold of rock. On the basis of the damage model presented, as well as extreme characteristics of stress-strain relationship at low confining pressure, we derive a unified solution of mechanical parameters of the model. In comparison with the experimental data, we discover that micro-unit strength of rock based on Drucker-Prager criterion or Mohr-Coulomb criterion is better than axial strain in reflecting rock mechanical properties, which shows that the failure and extension of rock is closely relevant with stress state. Then, in light of residual strength of rock, we introduce correction factor of damage variable and propose a new method for solving the factor. The results show that, data from theoretical curve in the damage model is in correspondence with experimental data; by using stress yield point as damage threshold point, we can avoid the situation that value of damage factor is not in the interval from 0 to 1 at low loading. Finally, through analyzing the changing process of rock damage variable, we conclude that the damage model can well reflect the stress-strain relationship of rock under triaxial compression.
  • ZHANG Hai-long, WANG Jin-ming, JIN Xin, CHEN Hong-jie
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 54-58. https://doi.org/10.11988/ckyyb.20140975
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    Drilling and acoustic wave observation is often used to determine the disturbance of excavation on rock quality. However, it is difficult to determine the boundary of rock quality partition by using conventional methods because there are more than one intersection between the curve of acoustic velocity changing rate and the threshold line. In this research, we optimize the conventional method by considering the detail features of acoustic velocity changing rate curve, and redefine the criteria of rock quality partition, which is made unique. Furthermore we apply the optimized method to the 4# diversion tunnel project of Baihetan hydropower station, and divide the rock quality of 4# diversion tunnel into 3 zones: the first disturbed zone, the second disturbed zone, and non-disturbed zone. Along with the increase of the depth from the excavation face, the disturbance of excavation on surrounding rock gets weaker and the rock quality becomes better. Subsequent excavation steps could worsen the rock quality, and the disturbed area will increase.
  • TANG Rui, WANG Qiang, GONG Bao-ju, GUO Ling
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 59-64. https://doi.org/10.11988/ckyyb.20140936
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    In order to study the influence of excavation on the internal force and deformation of retaining structures and the surrounding environment under different construction procedures, we employed Midas GTS to simulate the excavation process of deep foundation pit with different construction procedures. A deep foundation pit supported by pile-anchor was taken as case study. We also simulated the influence of unbalanced heaped load on the foundation pit during the construction of base plate, and obtained the internal force and deformation of retaining structure and the ground subsidence. Results show that the horizontal displacement of retaining structure and the ground subsidence in particular were largely affected by unreasonable construction procedure, which is unfavorable for the stability of foundation pit. With timely anchor support, the maximum bending moment of pile decreased at least 41.77% compared with that in the absence of anchor support, ground subsidence reduced by 32.75% at least; unbalanced heaped load on the foundation pit led to more than 5% difference in the maximum moment and over 10% in the horizontal displacement of left and right piles. The research result will be helpful to the design of deep foundation pit, and offers reference for the design, construction and research of similar engineering.
  • XU Gen-hong
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 65-69. https://doi.org/10.11988/ckyyb.20140971
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    Reliability analysis on highly weathered rock slope stability is carried out by means of a combination of first order two moment, Monte-Carlo simulation and finite difference numerical analysis. Firstly, the rock slope is treated as a continuous medium, and the characteristic parameters of the highly weathered rock slope are obtained by using equivalent continuum model. Subsequently, the material parameters of rock slope are defined as two-dimensional variable parameters, and the uncertainty model of the variable parameters is established by employing the first order two moments method. Then the spatial variability of geotechnical parameters is simulated by Monte-Carlo method. Finally, the influence of covariance and autocorrelation distance on safety factor and reliability index is researched by using finite difference method. Results show that the spatial variability of the geotechnical parameters has great influence on the evaluation of specific rock slope stability. The safety assessment for highly weathered rock slope could not be determined by single parameter. As covariance of rock slope parameter increases, the reliability index and safety factor reduce gradually; and with the increase of autocorrelation distance, reliability index increases gradually. Therefore, the effects of spatial variability of geotechnical parameters of rock slope should be considered in conventional slope analysis and design process.
  • WEN Ming-xing, LUO Ya-sheng, LIU Zi-wei, CHEN Ke-jun
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 70-74. https://doi.org/10.11988/ckyyb.20141039
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    In order to explore the residual strength characteristics of compacted loess blended with fly ash, and provide reference for engineering practice, we carry out experimental research on loess by using HJ-1 ring shear apparatus in the presence of different moisture contents and blending ratios of fly ash. The results showed that 1) with the increase of blending ratio of fly ash, the maximum dry density linearly decreases, whereas the optimum moisture content linearly increases; 2) if moisture content is below equilibrium moisture content, the relation between residual strength and blending ratio of fly ash shows tendency of negative correlation, otherwise, the relation shows tendency of positive correlation. In actual projects, we can treat wet soil with suitable proportions of fly ash to reduce the self weight of soil and to improve residual strength.
  • GUO Shao-wen, ZHAO Qi-hua, ZHANG Bing, MEI Zhu-yin
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 75-79. https://doi.org/10.11988/ckyyb.20141013
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    In southeast of China, conventional geological investigations are hard to carry out due to special terrain of high and steep rock slope. In view of this, we introduce 3D laser scanning technique to collect geometric parameters(occurrence, spacing and depth) of structural planes in the surface of slope. On the basis of geological data, we establish network graphs with different strikes in association with network simulation technique of structural plane. Meanwhile, we layout artificially virtual drills on the network graph to calculate rock quality of designation (RQD). Test results show that the proposed method is of strong applicability, convenience and high reliability. It doesn’t have shortages of traditional methods by drilling core, including few data and big error of RQD. Furthermore, the method can be used in high and steep slope which is difficult for geology investigation by traditional methods. Finally, revised RQD parameters of rock mass obtained by the method meet the requirement of actual projects.
  • ZHAO Jian-ping, SONG Xiao-dong, LIN Xiang
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 80-83. https://doi.org/10.11988/ckyyb.20141064
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    In order to discuss the characteristics of blasting vibration response of tunnel structure near ground surface under open-pit mine blasting, we collected a large amount of blasting vibration response signals of the tunnel structure by arranging measuring points on the underground tunnel vault and the ground along the orbit direction. Furthermore, we discuss the distribution characteristics of frequency spectrum and energy of tunnel based on wavelet analysis and fast fourier transform (FFT) algorithm. The results indicate that, 1)frequencies in tunnel the vault and the bottom of tunnel are larger than those in other positions, mainly in the range of 10-312 Hz; 2) the band of the main frequency accounted for large proportion of total energy; 3) the frequencies in vertical direction are lower than those in horizontal direction, and main frequency in vertical direction doesn’t change much with distance, but variation of main frequency in horizontal direction is obvious; 4) as for velocity response of tunnel structure in vertical direction, signal frequency at tunnel vault is lower than that at bottom of the tunnel, which should be paid more attention to.
  • ZUO Yong-zhen, ZHANG Wei, ZHANG Xiao-chuan, DANG Chen
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 84-88. https://doi.org/10.11988/ckyyb.20140937
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    The western region of Panzhihua city has abundant resources and will be the focus of development. Xigeda strata, which is distributed in this region, is a special soft rock with poor engineering properties. Research on Xigeda strata is of importance to the infrastructure construction and geologic disaster prevention in this region. Xigeda strata siltstone is planned to be used in the expansion project of Meizijing reservoir. In this paper we discuss the suitability of Xigeda strata siltstone as the filling material of earth-rock dam through a number of physical and mechanical tests by using large size test equipment. Test result reveals that Xigeda strata siltstone has good shear strength, good resistance to penetration deformation, with medium compressibility and permeability. It can be used as the filling material of earth-rock dam. The nature of Xigeda strata siltstone is close to that of silty soil in mechanical properties.
  • LUO Li, LIU Wen-bai, WANG Xiao-lin, ZHANG En-huai
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 89-92. https://doi.org/10.11988/ckyyb.20141005
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    In order to study the permeability characteristics of solidified dredged mud, we carry out indoor experiment with variable water head. During the experiment, the effects of curing condition, blending ratio of curing agent and curing age are taken into consideration. The results show that under given curing condition, permeability coefficient decreases with the increase of blending ratio of curing agent and curing age. Furthermore, the range of appropriate blending ratio of curing agent for permeability prevention in actual projects varies from 6% to 8%, and appropriate blending ratio of curing agent with 10% of fly ash is 5%. The test results offer reference for engineering design and construction in similar projects.
  • WANG Shuo-nan , YU Hong-ming , SHI Hua-peng
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 93-97. https://doi.org/10.11988/ckyyb.20150090
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    Debris flows of Shishu gully are induced by rainstorm, and it is important to study the impacts of moisture content and compaction rate of source-region soil on the formation of debris flow at early stage. During rainfall, source-region soil is gradually saturated and fine grain moves, which leads to the changes of soil mechanical properties such as density and strength. In this paper, we carry out direct shear test on source-region soil of debris flow in Shishu gully by using large-scale apparatus to explore strength behavior in the presence of different degrees of saturation and dry densities. We obtain the relationships of saturation and dry density vs. shear strength index c (cohesion) and φ (inner friction angle), as well as relationships of saturation and dry density vs. strength envelope, shear stress, and horizontal displacement, respectively. The results show that: 1) relationship between c and saturation shows tendency of inverse proportion, whereas c is in proportion with dry density , especially at early stage of saturation; 2) shear stress vs. horizontal displacement curve’s peak becomes obvious as the degree of saturation increases; 3) in the presence of adequate rainfall at early stage, source-region soil gradually becomes saturated and sudden drop of shear strength occurs; then, loose deposits at the surface layer are easy to be taken away by water flow, which causes the formation of debris flow. Through the experiment, we obtain the variation behavior of strength index for source-region soil of such grain size distribution.The results offer reference for the research of formation mechanism and the forecast of such debris flow.
  • DING Shao-lin, ZUO Chang-qun, LIU Dai-guo, LI Lin-sen, CHEN Jian-ping
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 98-103. https://doi.org/10.11988/ckyyb.20140932
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    Residual soil which widely distributes in south China is one of the major soils encountered in engineering construction and geological disasters evaluation. The engineering properties of residual soil are dependent on the composition, structure, and stress of soil, and also on the matric suction. Soil-water characteristic curve expressing the relationship between soil water content and matric suction is an important part of research on non-saturated soil. In this research we select granite porphyry residual soil, tuff residual soil and conglomerate residual soil, which are typically representative in Fujian province, as test sample soils to determine the soil-water characteristic curve in the process of Dehumidification and moisture absorption. Then we explain lag effects of soil water characteristic curve from the microscopic point of view. Based on Barden’s unsaturated soil classification, we put forward a simple method to predict the matric suction with saturation by analyzing the practical engineering significant moisture (saturation between 50%-90%) in view of the difficulties in measuring matric suction.
  • LIU Ming, CHENG Yong-hui, TONG Jun
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 104-110. https://doi.org/10.11988/ckyyb.20140985
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    According to the failure mode of expansive soil slope induced by expansion effect and the monitoring result of on-site simulation test, we summarize the techniques of expansive soil slope treatment. Furthermore, we compare and analyse the effectiveness of four treatment measures (cement soil modification, geogrid reinforcement, geomembrane, and geotextile bags filling) by evaluating the slope deformation and the variation of moisture content. Results reveal that cement soil (replacement of non-expansive clayey soil) has the best performance, whereas geogrid reinforcement is featured with complex techniques, and the compaction degree of geotextile bags filling is hard to control. Finally, we put forward the principles of expansive soil slope treatment.
  • ZENG Chui-chang, WU Yue-dong, LUO Ru-ping, WU Hong-sheng
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 111-114. https://doi.org/10.11988/ckyyb.20140918
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    Strength of undisturbed soil has gained significant interest among researchers in the field of geotechnical engineering. However, there are difficulties for us to obtain the strength of undisturbed soil due to soil disturbance.Based on the physical concept of interpolation function on disturbance, we propose a new method to predict the strength of undisturbed soil according to the strength of disturbed soil. According to the definition of soil disturbance degree(Dd) by Z.Hong and K.Onitsuka, in association with elastoplastic damage mechanics model of clay, we assume that the relationship between disturbance function and Dd shows tendency of exponential function. Furthermore, we deduce the strength of undisturbed soil by using interpolation function and the results of compression test and strength of disturbed soil. Typical undisturbed soft clay in Lianyungang district of Jiangsu province is taken as an example. We carry out vibration test of the clay to verify the model, and the test results show that the prediction method in this paper could well reflect the undisturbed soil strength of typical soft clay in Lianyungang.
  • RAN Tao, ZHAO An-ping, YIN Jian-hui
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 115-121. https://doi.org/10.11988/ckyyb.20140802
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    In this research, we simulate the dynamic response characters and failure mechanism of landslide by using the universal distinct element code(UDEC). Enziping landslide No. 2 in the Xiluodu reservoir area of Jinsha river is taken as example, and Ninghe-Tianjin earthquake record as the dynamic parameter. Simulated results show that: 1) under earthquake action, slope shows obvious amplification effect, and amplification effect of acceleration is the biggest, followed by displacement, velocity; 2) area of shear stress concentration and the shear strain of the slip zone dramatically increase after the peak value of the seismic wave, and the deformation and failure extended from the front to the rear of the slip zone due to the accumulation effect of shear strain; 3) safety factor of landslide stability is less than 1.0 and the maximum accumulated displacement is up to 1.58 m when the earthquake stops. Through analyzing calculated data, we conclude that failure mechanism of the landslide results from the combination effect of motion amplification and shear stress concentration and the accumulation of shear strain, and the failure mode remains bedding slide. In light of failure state of the landslide, we give suitable anchoring treatment suggestions for reducing the risk of river closure by earthquake-induced landslide so as to ensure the operation of Xiluodu hydropower project.
  • CHEN Xing, LIU Fa-qing, ZHU Yuan-le
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 122-126. https://doi.org/10.11988/ckyyb.20140979
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    For upstream tailings pond with permeable rock-fill starter dam, slope swamping of tailings-fill dam is often found in later stage due to high water level, short dry beach, inadequate tailings permeability, steep slope, or absence of seepage facilities. We have rich experiences in the treatment of such slope swamping, but researches and treatment measures on the swamping of earth-rock starter dam are rare. Through analyzing the causes of starter dam swamping and comparing the treatment measures, we applied horizontal seepage draining pipes to the treatment. By observation and on-site investigation, we found that the depth of saturation line of earth-rock starter dam gradually declined, slope swamping diminished, and the dam’s stability improved. Through the experience we conclude that horizontal seepage draining pipes could eliminate the swamping of earth-rock starter dam.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • ZHANG Xue-cai , WANG Zheng-zhong , MENG Ming , LI Lu-ming
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 127-131. https://doi.org/10.11988/ckyyb.20140826
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    At present, there are several problems in determining the height of main beam in hydraulic steel gate, including a large number of empirical formulas, imperfect theories, and ignorance of influences of section form and support position. According to design code of steel gate, with requirements of strength, stiffness, stability and geometric structure as constraint conditions, we take minimum steel amount of main beams and vertical baffles as objective function, and establish optimization models for beam height of simple support and double cantilever’s girder under conditions of uniaxial and biaxial symmetrical sections. Theoretical formulas of optimal girder height are derived by semi-analytical methods. Through comparing with built projects, we find that girder heights calculated by the theoretical formulas in this paper are close to those in practical projects, which still can be optimized. Furthermore, we can decrease beam height through reducing height-thickness ratios of partition and web of main beam. The theoretical formulas can be applied to engineering practice, and also provide a theoretical basis for improving specification.
  • LI Jun, FANG Chao-yang
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 132-136. https://doi.org/10.11988/ckyyb.20141027
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    In order to reduce cracks in the lining concrete of spillway tunnel of Baihetan power station, we discuss the impacts of surrounding rock behavior and lining thickness on thermal stress of lining concrete. On this basis, we make reasonable criteria of temperature control and put forward economical and feasible measures. According to the structure and material properties of lining concrete of the spillway tunnel as well as boundary conditions, we carry out three-dimensional simulation on temperature field and stress field during the construction of lining by using ANSYS. Results show that the larger the thickness of lining concrete is, the higher the concrete temperature is, and the later the maximum temperature comes; moreover, the higher the strength of surrounding rock is, and the larger the thickness of lining concrete is, the higher induced tensile stress is, and the reverse is true. Both surrounding rock behavior and lining thickness have effects on the temperature and thermal stress of lining concrete, so it is necessary to determine lining thickness according to surrounding rock behavior to ensure lining concrete safety on resisting cracks.
  • LIU Dan, SUN Xi-huan, LI Yong-ye, SHI Ji-zhong
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 137-140. https://doi.org/10.11988/ckyyb.20140988
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    Optimizing the mix ratio of RCC (rolled compacted concrete) is an important technical measure to protect dam safety. With RCC dam project in cold area as an example, we discuss the dosage of admixture and quality of fly ash affecting the mix proportion design, and obtain the fitted relationship curves between RCC binder-water ratio and compressive strength under different working conditions. Results show that increasing the dosage of admixture could effectively reduce the plastic material dosage without affecting the quality of roller compacted concrete; fly ash of different grades has great effect on the water use of concrete; the water-binder ratio has good linear correlation with compressive strength. The variation of compressive strength development coefficient leveled off after the first increase.
  • ZOU San-bing, YANG Nai-xin, LUO Xi, PENG Gang
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 141-146. https://doi.org/10.11988/ckyyb.20140706
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    Radial splitting tensile tests for natural and water saturated concrete specimens with size of Φ150×150mm was carried out under different strain rates(10-5,10-4,10-3 and 10-2s-1). Splitting tensile strength of concrete was analyzed in detail, and energy release characteristics and damage law of natural and water saturated concretes were researched in the whole process of splitting tensile damage by real-time acoustic emission data. The results show that: 1) with the increase of loading rate ,splitting tensile strength of natural and water saturated concretes increases; 2) at low strain rates (10-5,10-4 and 10-3/s), the splitting tensile strength of water saturated concrete is smaller than that of natural concrete due to the wedging action of free water, whereas at the strain rate of 10-2/s, the splitting tensile strength of water saturated concrete is larger than that of natural concrete due to Stefan effect; 3) dynamic enhancement factor of water saturated concrete is larger than that of natural concrete, and strain rate sensitivity of water saturated concrete is more obvious; 4) acoustic emission signal characteristics is in accordance with concrete failure characteristics, and acoustic emission data can be used to accurately monitor the process of concrete splitting tensile failure.
  • SONG Li, LIU Lu-lu, GAO Yu-qin
    Journal of Changjiang River Scientific Research Institute. 2016, 33(3): 147-150. https://doi.org/10.11988/ckyyb.20141060
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    In order to determine two endpoints (P1 and P2) in the straight-line segment of stress-strain curve of plastic concrete, and to obtain the elastic modulus, we carried out uniaxial compression test on 48 concrete specimens of four different mix proportions. Through analyzing typical stress-strain curve, we selected approximated straight-line in the curve, and compared the secant modulus with mean value of tangent modulus. On this basis, we studied how to determine P1 and P2. The results show that 1) the approximated straight-line segment appears at the ascent stage in the stress-strain curve of plastic concrete; 2) with given strength of plastic concrete less than 5 MPa, it is suitable to choose 60% and 80% of peak stress as the elastic modulus of P1 and P2, respectively, otherwise, further study is required. Finally, the research offers a method for determining the values of material performance of plastic concrete with low strength.