25 September 2016, Volume 33 Issue 9

    

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RIVER LAKE SEDIMENTATION AND REGULATION
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  A Calculation Method for Cumulative Frequency Below Low Tidal Level of Navigation Based on Real Water Depth: Taking Qibao Section of Qiantang Estuary as Example

  WANG Wei-biao,ZENG Jian,XIE Dong-feng

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 1-4. https://doi.org/10.11988/ckyyb.20160366

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  The cumulative frequency of low tidal level of navigation is an important index for navigation channel design, improvement and benefit evaluation. Normally, the cumulative frequency could be calculated by the number of days that the water level is higher than the designed lowest navigable water level. In the Qiantang river estuary of Zhejiang Province, the bed erosion and deposition is drastic, and the low tidal level is closely related to the bed elevation changes. Hence the aforementioned method could not count definitely the cumulative frequency in Qiantang estuary. In this study, the historical bathymetries since 1980 were used to analyze the bed evolution patterns in the annual years at Qibao section in Qiantang estuary, and the relationships between the variations of low tidal level and the bed erosion/deposition were discussed. On this basis, a new method based on the actual water depth under daily low tidal level was proposed for the calculation of cumulative frequency. According to the hydrological characteristics of Qiantang estuary, three typical hydrological years representing high flow year, normal flow year and low flow year were chosen to analyze the cumulative frequency of water depth for navigation in Qibao section. The results show that in the three years, the cumulative frequencies at Qibao section could reach 100%, 100% and 87%, respectively, which agrees with the reality. This method could be also applicable to other tidal estuaries where changes of bed elevation and low tidal level are remarkable.
WATER RESOURCES AND ENVIRONMENT
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  Spatio-temporal Variations of Extreme Precipitation in the Yangtze River Delta during 1960-2012

  ZHOU Bei-ping, SHI Jian-qiao, LI Shao-kui, CHEN Ting, MA Li

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 5-9. https://doi.org/10.11988/ckyyb.20150639

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  In recent years, the trend of global warming has been more and more serious, and extreme precipitation contributed to the risk of drought and flood disaster in the Yangtze River basin. Daily precipitation data of 34 automatic meteorological stations in the Yangtze River delta region from 1960-2012 were used to investigate the features of spatial and temporal variations of extreme precipitation using methods of the trend analysis, Mann-Kendall test and GIS spatial analysis. The main conclusions are as follows: 1) the extreme precipitation threshold limit value was in the range between 30.7mm and 46.7mm, all are heavy rainfall, and some close to rainstorm. The extreme precipitation threshold value presents zonal distribution features, large in north Jiangsu, southwest and southeast Zhejiang, and small in south Jiangsu, north Zhejiang, and Shanghai; 2) the frequency and intensity of extreme precipitation has obvious interdecadal differences, characterized by trends of decreasing obviously in early stage and slowly rising in late stage. The precipitation in the Yangtze River delta was more abnormal, and the extreme precipitation mutations mainly occurred in 1987; 3) the frequency and total amount of extreme precipitation were high in the southwest and southeast coastal islands of Zhejiang, and the value of R_95T was large mainly in north Jiangsu and Zhejiang's southeast coastal areas; 4) the seasonal change of extreme precipitation frequency reflected the north-south movement of the rain belt in a year, and also reflected the precipitation differences between the coast and the inland. The study also found that the precipitation events in Ganyu station of north Jiangsu, and stations on eastern Zhejiang's coast and island had become extreme, with rainstorm and flooding likely to happen in the future. The probability of drought in Sheyang and its surrounding areas will increase.
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  Assessing the Vulnerability of Basin Water Resources Based on Entropy Weight Method: A Case Study of Huaihe River Basin

  LIU Qian-qian, CHEN Yan

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 10-17. https://doi.org/10.11988/ckyyb.20150591

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  Assessment of basin water resources vulnerability reflects the water security conditions of the research area in an objective way by quantifying the degree of water resources vulnerability. According to the manifestation and causes of water resources' vulnerability, we built an evaluation indices system which consists of four primary indicators including water yield, water quality, flood disaster and drought and three secondary indicators of natural factor, human factor and carrying factor. On this basis, we constructed an assessment model for water resource vulnerability by using the entropy weight method in association with the linear weighting method. In this research we took Huaihe River basin as an example and assessed the water resources vulnerability of four provinces in 2003-2012 from two dimensions of time and space. The results showed that in terms of the time dimension, the value of water resources vulnerability in Huaihe River basin decreased in the decade, indicating that the vulnerability of water resources in the four provinces was improving; while in terms of the space dimension, water resources in Huaihe River basin was becoming more and more fragile from the west to the east. Research shows that the water resources vulnerability in Huaihe River basin presents a trend of improvement, but there are still some problems that need further management and regulation.
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  Improved RAGA-PPC Model and Its Application to River Health Assessment

  LI Peng-cheng, HAN Chun, WANG Yue-min, WANG Jia-rong

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 18-22. https://doi.org/10.11988/ckyyb.20150792

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  A RAGA-PPC (Real coding based Accelerating Genetic Algorithm-Projection Pursuit Classification) model was employed to convert high dimensional data to low dimensional data and assess the health of a river in Haihe river basin. Majia River, a key river of Haihe river basin in Shandong Province, was taken as case study. Data obtained from water quality monitoring and pollution investigation in 2009-2011 were utilized, and 12 sections were selected for the investigation. The assessment results show that the overall trend of total nitrogen and ammonia nitrogen in the whole river is growing, and also biochemical oxygen demand in the downstream area from Dadaowang gate to Dengji goes almost straight up. Chemical oxygen demand and biochemical oxygen demand of the river change in flood season and non-flood season, both increasing in flood season. According to comparison between the weighted value and the standard value of 5 sections, the chemical oxygen demand and biochemical oxygen demand are both between 0.22-0.15, indicating that Majia River is basically in a sub-healthy state. Furthermore, the human factors and natural factors of Majia River's sub-healthy state are analyzed in the purpose of providing effective scientific basis for river health assessment and river pollution control in the Haihe River Basin.
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  Wet-Dry Classification of Annual Runoff Based on LBA-PP Model

  MAO Zong-bo,DAO Hai-ya

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 23-27. https://doi.org/10.11988/ckyyb.20150635

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  The wet-dry features of annual runoff depend on the size and time-history distribution characteristics of runoff itself.In view of this,we put forward a LBA-PP model of wet-dry classification of annual runoff by searching the optimum projection direction using bat algorithm (LBA) improved with a Lévy flight strategy in association with projection pursuit (PP) model.We also construct a particle swarm optimization (PSO) algorithm PP model for comparison,with the annual runoff at Xiyang station in Yunnan Province as a case study.Results show that the LBA algorithm is superior to PSO algorithm,and is of good convergence accuracy,robust performance and global optimization ability.Using LBA algorithm to find the best projection direction of PP model not only improves the classification accuracy of the PP model,but also provides a new way and method for the selection of the PP model. In the LBA-PP model,the annual runoff is considered,and the time history information is distributed.The classification results are more scientific and objective than those of conventional method.
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  A Case Study on Water Quality of Suzi River

  JIA Lei

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 28-32. https://doi.org/10.11988/ckyyb.20160073

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  To maintain the health of river's eco-system has become an inevitable tendency of basin management. In this research, an assessment system for the sustainable development of basin water quality was established according to hydrologic, hydraulic, sediment geomorphology, and aquatic ecological factors. Typical indexes of basin water quality were selected and analyzed using multiple environmental factors analysis. Suzi river watershed was taken as a case study. Environmental factors which reflect the river health state were selected. This research could be a reference for the sustainable management and eco-environmental construction of the river.
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  Application of Fuzzy Connection Degree Model Based on Combined Weights to Evaluate Water Quality

  YE Zhang-rui,LU Yi-min

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 33-39. https://doi.org/10.11988/ckyyb.20150615

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  In view of the uncertainty of evaluation indexes of water quality and the fuzziness of water quality standard, a fuzzy connection degree model of water quality evaluation was constructed based on set pair analysis and fuzzy analytical hierarchy process. First of all, the index values of water samples were preliminarily classified by calculating the hierarchical connection degree of each evaluation index value. Then the comprehensive degree of connection between samples and water quality standard was calculated. Finally, water quality grade was judged by confidence criterion. To highlight the contribution of different evaluation indexes, entropy method and super weighting method were introduced. Then the weights were combined based on ideal point method, by which the index weights were more reasonable. This model was applied to the evaluation of the fishery waters of Minjiang River, and the result was compared with those from gray classification method, synthesis index method and single factor evaluation method. The results obtained by the proposed model were closer to the real situation, and hence are reliable.
WATER SOIL CONSERVATION AND ECOCONSTRUCTION
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  Quantitative Assessment of Soil Erosion of Chengdu City

  LIU Bin-tao, SONG Chun-feng, TAO He-ping

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 40-47. https://doi.org/10.11988/ckyyb.20150600

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  Chengdu city is the political, economic, cultural, and population centre in southwest China. The water and soil conservation works are very important to the urban ecological environment of Chengdu city, which is regarded as a pilot example in southwest China. Based on the Sichuan soil loss equation, the soil erosion of Chengdu city was quantitatively assessed and analysed. Results show that the soil erosion situation of Chengdu city is not serious, and the soil erosion modulus and soil erosion ratio are lower than the average level in Sichuan province. The soil erosion of Chengdu city mainly distributes in the Longquan Mountains, Longmen Mountains and Qionglai Mountains, and the soil erosion situation of Longquan Mountains is more serious than that of Longmen Mountains and Qionglai Mountains. As the Longmen Mountains were affected by the “5.12” Wenchuan earthquake which occurred in 2008, the soil erosion intensity is very high in some areas of Longmen Mountains, and it is prone to suffer from sudden water and soil loss disasters such as debris flow and landsides. These areas should focus on the earthquake-induced soil erosion, and strengthen the monitoring and early warning.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  ) Deformation Monitoring of Pile and Anchor Supporting Structure of Deep Foundation Pit Using BOTDA

  LI Li-gong,DING Yong,MA Bin-bin,ZHOU Ke-ming

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 48-51. https://doi.org/10.11988/ckyyb.20150654

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  BOTDA distributed optic fiber monitoring technology was used to monitor the deformation of pile and anchor supporting structure of deep foundation pit.Through long-term strain monitoring of H-steel and pre-stressed anchor of the supporting structure during the excavation process,the deflection distribution of H-steel and stress distribution of pre-stressed anchor were obtained.On this basis,the stress and deformation state of H-steel and pre-stressed anchor was analyzed,providing reliable reference for pit construction.Engineering practice shows that deformation monitoring for foundation pit's supporting structure using distributed optical fiber sensing technology based on BOTDA is feasible and has the advantage of continuous monitoring.
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  New Idea of Shallow Landslide Treatment: Taking the Derleck Landslide as an Example

  HUANG Xi-chao, REN Guang-ming, YAO Chen-hui, LI Yuan-liang, YANG Lei, LIU Bin

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 52-56. https://doi.org/10.11988/ckyyb.20151082

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  Shallow landslide is mainly induced by heavy rainfall and human engineering activities, and generally its treatment is simple, mostly in forms of cutting slope, gravity retaining wall, anchor and so on. These methods are costly and also have impacts on ecological environment. From the perspective of people's livelihood, we put forward a measure of shallow landslide treatment suitable for local conditions. We combine the reinforced retaining wall with the “Golden Land Project”, a land reform project beneficial to the people, and apply it to the shallow landslide treatment in mountain areas. On the one hand, the lands of the local residents can be rectified and reformed, and on the other hand, the goal of treating shallow landslide can be achieved. The treatment idea offers a reference for shallow landslide treatment in the future.
HYDRAULICS
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  Airfoil Flip Bucket for Aeration Devices with High Flow and Small Slope

  ZHOU Chi,JIANG Bo-le,XING Yan

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 57-59. https://doi.org/10.11988/ckyyb.20150625

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  Problems such as cavity backwater and short dimension are usually found in the aeration devices of spillway tunnel with high flow and small slope gradient.In this paper,an airfoil flip bucket was put forward according to existing research result and practical application aiming to solve the above problems.With the physical model test on spillway tunnel 1^# in the expansion project of Centianhe reservoir as a case study,the effects of different configurations of airfoil flip bucket on the hydraulic characteristics of aeration devices were compared,and the effectiveness of airfoil flip bucket in relieving cavity backwater of aeration devices was also demonstrated,and the basic layout pattern was eventually determined by the physical model test.This study lays a foundation for further research and popularization.
ROCK SOIL ENGINEERING
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  PFC Simulation of Uniaxial Compression and Brazilian Splitting Test of Rock Based on Flat-jointed Bonded-particle Material

  LIU Fu-you,CHEN Peng-yu,YU Hong-ming

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 60-65. https://doi.org/10.11988/ckyyb.20150566

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  The Flat-joint bonded-particle material was selected as the basic model for rock simulation.The macro-parameters of rock were calculated through numerical uniaxial compression test and Brazilian splitting test in PFC.Orthogonal design was adopted to conduct numerical tests and multi-factor analysis of variance and regression analysis were utilized to analyze the relationship between macro-parameters and meso-parameters.On this basis,method of matching the meso-parameters for numerical uniaxial compression test and Brazilian splitting test was proposed.According to laboratory tests of limestone,the meso-parameters of limestone were obtained and the PFC simulation of uniaxial compression and Brazilian splitting tests of limestone were conducted.The simulation results are close to the laboratory test results,which validated the effectiveness of the proposed method.
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  Seismic Response of a Slope with Complex Shape

  LIU Yong,WANG Yun-sheng,TANG Qi,CHEN Yi-xi

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 66-71. https://doi.org/10.11988/ckyyb.20150542

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  Unloading fractures developed well in the superficial part of deep valley slope and was strongly weathered, which made subcutaneous layer a non-continuum and led to dielectric property difference. Seismic response in this area is complicated. Taking Dongshan slope in Qingchuan city as an example, we firstly analyzed the seismic monitoring data, and then simulated the dynamic response characteristics of the slope by using discontinuous deformation analysis method which is suitable for the analysis of rock slope motion process. We revealed the influences of epicentral distance, elevation, magnitude , terrain and T-shaped mountains and other factors on seismic peak ground acceleration (PGA). The results indicate that the seismic peak acceleration amplification factor at vertical ridge direction and higher elevation is larger, reaching 6.12 times; on the protrusion part of the terrain, seismic wave can also get a certain degree of amplification, reach 3.3 times; in the T- shaped ridge binding site, the PGA amplification ratio will be reduced to a certain degree.which greatly deteriorate its engineering properties. Latest research indicates that the increase of suction and inhomogeneous distribution mainly lead to the shrinking and cracking of expansive soil. However, few experiments about the expansive soil shrinking consider the effect of boundary condition on the shrinking process. In this research, pure montmorillonite is taken as test material,and its shrinking process in the presence of glass and vaseline friction boundaries are tested at different temperatures. The computer image processing technique is employed to quantify the geometric structure and morphologic characteristics of cracks. A conceptual model of shrinking and cracking of clay is established. Test results indicate that during the process of saturation-dehydration, cracks of specimens with vaseline-surface occur late and the critical water content of cracking is obviously lower than that of glass-surface specimens. At temperatures of 20℃, 30℃ and 40℃, the final amount of cracks of vaseline-surface specimen is smaller than that of glass-surface specimen by 70.3%, 79.6% and 77.6%, respectively. Additionally, in the presence of the same boundary friction, the pore water evaporation accelerates and the final amount of cracks increases with the increasing of temperature.
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  Effects of Boundary Friction and Temperature on the Process
  of Shrinkingand Cracking of Pure Montmorillonite During Pore Water Evaporation

  DU Wen-feng^1,2,WANG Jing-e²,LIU Qing-bing²,XIANG Wei^1,2,HUANG Wei¹
  

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 72-77. https://doi.org/10.11988/ckyyb.20150992

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  The shrinking and cracking of expansive soil during pore water evaporation is one of the main causes which greatly deteriorate its engineering properties. Latest research indicates that the increase of suction and inhomogeneous distribution mainly lead to the shrinking and cracking of expansive soil. However, few experiments about the expansive soil shrinking consider the effect of boundary condition on the shrinking process. In this research, pure montmorillonite is taken as test material，and its shrinking process in the presence of glass and vaseline friction boundaries are tested at different temperatures. The computer image processing technique is employed to quantify the geometric structure and morphologic characteristics of cracks. A conceptual model of shrinking and cracking of clay is established. Test results indicate that during the process of saturation dehydration, cracks of specimens with vaseline surface occur late and the critical water content of cracking is obviously lower than that of glasssurface specimens. At temperatures of 20℃, 30℃ and 40℃, the final amount of cracks of vaseline surface specimen is smaller than that of glass surface specimen by 70.3%, 79.6% and 77.6%, respectively. Additionally, in the presence of the same boundary friction, the pore water evaporation accelerates and the final amount of cracks increases with the increasing of temperature.
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  Size Effect on Uniaxial Compressive Strength of Red Bed Soft Rock

  LV Long-long,SONG Li,LIAO Hong-jian, LI Hang-zhou

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 78-82. https://doi.org/10.11988/ckyyb.20150567

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  The size effect of red bed soft rock's uniaxial compressive strength was researched in this paper.The testing samples are taken from Humaling Tunnel of the Xiaguan-Guangyuan Section of Lanzhou-Chongqing Railway,Dingxi city,Gansu Province,China.The samples are of cylindrical shape with different ratios of height to diameter(diameter 50mm,height 20-100 mm).Results show that the red bed soft rock has obvious size effect.The dimensionless size effect coefficient is defined as the ratio of uniaxial compressive strength of nonstandard sample to that of standard sample.Fitting of test data shows that size effect coefficient is linearly related with height to diameter ratio and average elastic modulus.A mathematical model is established to illustrate this linear function.When the height to diameter ratio is smaller than 2.0,the size effect coefficient decreases and then increases with the increase of the ratio.The height to diameter ratio corresponding to minimum coefficient is obtained.Moreover,stress analysis is conducted to research the destruction patterns of red bed soft rock,and the causes of size effect coefficient variation are given.
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  Impact of Montmorillonite Content on Desiccation Cracks on Clay Surface

  XIA Dong-sheng, LIU Qing-bing, XIANG Wei, WANG Jing-e, AI Mi

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 83-86. https://doi.org/10.11988/ckyyb.20150607

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  As a major clay mineral in swelling soil, montmorillonite has important influence on swelling-shrinkage properties and developing fissures of swelling soil. Desiccation tests were conducted under 40 ℃ on initially saturated montmorillonite-silica sand mixture slurry to investigate the effects of montmorillonite content on shrinkage and cracking characteristics. Water loss and surface crack evolution were monitored during the whole drying period while the critical moisture content and surface crack ratio δ_S were obtained with computer software. The results showed that during drying period, the process of water loss showed three obvious phases: the evaporation phase at constant speed, the decline phase and the residual phase. And cracks on the surface of samples mostly developed in the first phase. The final surface crack ratio δ_SF and the initial moisture content w_I at which the cracks start were significantly influenced by the content of montmorillonite showing trend of increasing with the growth of the content of montmorillonite. But the final moisture content w_F at which the cracks end were different, yet, the difference Δw between w_I and w_F is positively related to the content of montmorillonite.
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  Deformation Properties of Saturated Dispersive Clay

  SHI Xiang,FAN Heng-hui,LIU Gang,LI Pu

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 87-92. https://doi.org/10.11988/ckyyb.20150630

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  Dispersive clay is of low erosion resistance and impermeability,and severely endangers the safety of water conservancy construction as it has high dispersion in low salinity water.At present,research of dispersive clay mainly focuses on the identification,impermeability and modification;however,studies on the deformation properties are rare.In this paper,the deformation behavior of saturated dispersive clay under different degrees of compaction was studied through uniaxial compression tests.The test results show that the deformation of dispersive clay depends not only on the stresses exerted on them but also the time elapsed,and has obvious nonlinear characteristics.The results also indicate that the degree of compaction has significant effect on the deformation of saturated dispersive clay.According to the test results,the stress-strain and strain-time curves of saturated dispersive clay can be expressed with the power function.The loading constitutive model and creep constitutive model were established,and the comparison between model predicted result and measured result indicates that the predicted result using the model are in reasonable agreement with the test data.
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  Changes of Expansive Soil's Meso-structure and Its Relation with Acoustic Velocity

  WEI Bing-xu,GONG Shu,LIU Bin,LIU Xiong,OUYANG Yun-qing

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 93-97. https://doi.org/10.11988/ckyyb.20150616

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  The variation law of meso-structure and average P-wave velocity of expansive soil under the condition of drying-wetting cycles was studied through CT technology and TH204 nonmetallic acoustic test.Through defining CT-damage variable by research methods of damage mechanics,the relationship between the changes of meso-structure and the average P-wave velocity resulted from drying-wetting cycles was established.Results show that the first to the fourth drying-wetting cycles have big influence on the meso-structure of expansive soil,and the development of internal micro-crack was obvious; whereas the seventh and the eighth drying-wetting cycles have little influence on the meso-structure.The average P-wave velocity of expansive soil attenuates non-linearly with the increase of cycle times,and finally tends to be stable.With the increase of drying-wetting cycle times, the damage variable of expansive soil increases gradually,and the evolution of meso-structure damage is a non-linear accumulating process.CT damage variable is in a good exponential attenuation relationship with average P-wave velocity.
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  Experimental Study on CBR Value of Cement-treated Weathered Sand of the Three Gorges Reservoir

  YANG Jun,LIU Shi-yi,ZHANG Guo-dong

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 98-101. https://doi.org/10.11988/ckyyb.20150552

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  The weathered sand from the Three Gorges Reservoir in Yichang city was stabilized by cement and was used for highway pavement base. Weathered sand was mixed with 3%, 5%, 7%, 9% cement, respectively, and maintained for 7 days, 14 days, 21 days,and 28 days under standard curing condition, and then test on the California bearing ratio(CBR) value of the treated weathered sand was carried out. Experimental result shows that cement can effectively improve the CBR value of weathered sand, and cement content and curing age both have great influence on the CBR values of weathered sand. Under the same curing age, the CBR value of cement-treated weathered sand increases with the growth of cement dosage gradually. CBR value and cement dosage shows good logarithmic relation. Under the same dosage of cement, the CBR value of cement-treated weathered sand increases with the growth of curing age steadily, and the relationship between CBR value and curing age is linear. In comprehensive consideration of economy and mechanical properties of weathered sand, adding 7% cement could maximize the CBR value.
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  Numerical Analysis of Failure Modes and Stability of Soft and Hard Rock Interbedded Slope

  ZHENG Zhi-yong, YU Hai-bing, XU Hai-qing

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 102-106. https://doi.org/10.11988/ckyyb.20150661

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  The failure modes of soft and hard rock inter-bedded slope were simulated by FLAC^3D, and the stability coefficient k in the presence of different dip angles θ and rock thicknesses h was analyzed by using strength reduction method. Results show that h has small influence on slope failure mode, while θ has obvious effect on the failure mode. For horizontally layered slope, the failure mode is slipping-ripping; whereas for consequent slope, with the increase of θ, the failure mode experiences a progress of sliding-ripping, sliding, sliding-buckling, and bending-buckling; while for vertically layered slope, the failure mode is bending-slump; and for anti-dip rock slope, the failure modes are sliding-buckling and bending-toppling. Moreover, for gentle bedding rock slope, the thickness of the rock has little impact on the stability coefficient k, which is determined by the soft rock near the slope toe. As for the other types of layered slope, when the thickness of soft rock is constant, the stability coefficient increases with the increase of hard rock thickness, while when hard rock thickness is constant, the stability coefficient decreases with the increase of soft rock thickness. With the increase of θ, the k value of consequent slope first decreases and then increases, while the k value of anti-dip rock slope increases and then decreases and finally increases. The overall stability of soft and hard rock slope follows the order of vertical layered slope>steep bedding rock slope>anti-dip slope> horizontal layered slope> gentle bedding rock slope.
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  Swelling Deformation Characteristic and Calculation Model of Compacted Weak Swelling Soil

  BIAN Jia-min

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 107-110. https://doi.org/10.11988/ckyyb.20150613

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  Swelling is the typical characteristic of weak swelling soil,and is the most important cause of the damage of swelling soil structures.It is of great importance to estimate the deformation of swelling soil in some specific conditions,and it is not only important but also necessary to establish the calculation model for weak swelling soil. In view of this, on the basis of analyzing the influence factors of linear swelling ratio,we carried out swelling deformation tests on weak swelling soil of the slope of Xuhe river in different initial status.We also studied the influences of humidification ratio,degree of compaction and overburden pressure on the linear swelling ratio,and established the calculation model for linear swelling ratio in consideration of humidification ratio,degree of compaction and overburden pressure.Finally we used the test data of other scholars to verify the calculation model,and the verification results showed that the calculation model could well fit the swelling deformation of compacted weak swelling soil.
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  Model Test on Rainfall Warning Criteria of Retrogressive Landslide

  PAN Yi-heng, LI Xue-ping, WU Li-qing, WANG Wei, TAN Fu-lin

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 111-115. https://doi.org/10.11988/ckyyb.20150576

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  Indoor artificial rainfall simulation test was conducted to investigate the mechanism of retrogressive landslide, and the criteria of rainfall warning for the study were proposed. The Maijianwo landslide in Lingbao City of Henan Province was taken as a case study. In the model test, moisture sensors, tracking points and digital cameras were adopted to record variations in the moisture of crucial parts, the surface deformation and crack propagation. Research results showed that the rainstorm led to destruction from the bottom of slope to the top gradually as a retrogressive mode. The slope failure process was divided into three stages as deformation activation, deformation acceleration and integral destruction in accordance with the critical time points by analyzing the deformation characteristics and moisture monitoring data of crucial parts. According to the above failure mode, the cumulative rainfalls E₁ (75mm) and E₂ (180mm) were respectively set as the orange and red warning criteria for the Maijianwo landslide when there were penetrating cracks on the slope toe and shoulder.
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  Internal Factors of the Failure of Granular Mixtures Slope

  BU Xiang-hang,FU Rong-hua,LI Jin-de,HUANG You

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 116-120. https://doi.org/10.11988/ckyyb.20150606

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  Among factors which affect the stability of granular mixtures slope, external factors play an inducing role while internal factors dominate, but the natural angle of repose of the slope plays a controlling role. In view of this, granular mixture materials of four different compositions (1＜C_u≤7) were prepared and model test was conducted to simulate the instability of granular mixtures slope caused by heap. Results indicate that 1) the angle of repose increased with the increase of non-uniform degree of particle; 2) with the increase of round degree, the angle of repose also tended to increase, but the growth rate was low when round degree was between 1.14-1.40, and higher when greater than 1.40; 3) along with the increase of m, the angle of repose increased at first and then reduced, and finally gradually stabilized; 4) the angle of repose increased with the increase of c and φ in general, but the change was slow in the initial stage. Finally, formula of estimating the natural angle of repose of granular mixture slope was established by fitting the five factors using linear regression theory, and was verified to be correct.
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  Orthogonal Analysis of Factors Affecting the Anti-floating Effect of Draining Decompression

  YANG Bo-jin,LI Yin-ping,GAN Quan,LIU Wei,KONG Qing-cong,HUANG Jue-hao

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 121-127. https://doi.org/10.11988/ckyyb.20150629

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  In view of the shortcomings of traditional basement anti-floating methods,we discussed the basic principle and the corresponding construction measures of draining decompression.We also analyzed the factors affecting the anti-floating effect with orthogonal experiments compared with numerical simulation.The factors include the width of backfill,the spacing of drainage holes,the compaction degree of backfill,and the disturbance degree of the underlying at the bottom of the basement.Finally,we calculated the influence order and weights of various factors using residual analysis method and analytic hierarchy process.Results show that compared with conventional methods,draining decompression has obvious anti-floating effect by changing passive anti-floating to active anti-floating.Moreover,it is convenient to construct,and the cost is low.The order of factors according to the influence is as follows:compaction degree of backfill>width of backfill>spacing of drainage holes>disturbance degree at the bottom of basement,and the corresponding weights are 0.55,0.27,0.15,0.03,respectively.The sum of the first three factors is up to 0.97.As a result,we should try to reduce the spacing of holes,the width and the water permeability of the backfill to achieve good anti-floating effect in engineering practice.Besides,we should also limit the parameters of these three factors reasonably in order to achieve the best effect of lowering water level according to specific engineering conditions.The research method provides an important reference for the design and construction of the anti-floating method by draining decompression.
HYDRAULIC STRUCTURE AND MATERIAL
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  Finite Element Stress Analysis and Structural Damage Research of Pile Foundation of High-piled Wharf

  ZHAO An-ping, LI Hao-jie, YU Hong-sheng,XIAO Wei-ming

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 128-132. https://doi.org/10.11988/ckyyb.20150550

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  In order to study the stress and structural damage of high-piled wharf, we simulated three kinds of typical sections of a high-piled wharf by using finite element method, and analyzed the pile bearing capacity. Then, we compared the simulated result with the damage detection result of pile foundation structure, and the results coincide with each other, verifying the correctness of theoretical analysis. Finally, we gave the reinforcement measures for the damaged parts. According to the finite element analysis of pile bearing capacity and measured results, we concluded that pile top (1-2 m from beneath the pile cap) is the most vulnerable part. For the three typical types of cross sections, we should try to avoid using the forms of section one and section two. Because the horizontal bearing capacity of the two types of cross section is too small so that the piles are likely to be damaged by horizontal force in the process of use. Besides, we put forward two measures of reinforcing the damage locations of piles by enlarging pile cap section and by steel hoop. But in concrete repair, under the premise of considering time factor and economic benefits,we should flexibly choose repair measures based on summarizing and comparing the advantages and disadvantages of various measures to treat the damaged positions of the piles properly.
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  Analysis of Anti-sliding Stability of Gravity Dam Using Numerical Manifold Method

  CHEN Yuan-qiang, ZHENG Hong, CHEN Tao

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 133-137. https://doi.org/10.11988/ckyyb.20150655

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  The Numerical Manifold Method (NMM), as a new numerical method, has seldom been utilized in the anti'sliding stability analysis of gravity dam. In this study, the load matrix of water pressure and uplift pressure, as well as the solution of safety factor were given. Furthermore, NMM was adopted to analyze the anti'sliding stability of the foundation planes of gravity dam and the deeply laid double inclined planes, the safety factor was thus calculated, and was further compared with the corre sponding results obtained by the contact analysis in finite element method (FEM). The results demonstrated that the safety factors calculated by the above two methods, namely the NMM and FEM, were fundamentally consistent, which verified the feasibility of applying NMM to the anti sliding stability analysis of gravity dam.
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  Calculation of Creep Stress of Early-age Concrete Based on Further Development of ANSYS

  GUO Hao-yang, QI Lan,LI Shao-ming,LIU Yong,ZHAO Fang-xing

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 138-142. https://doi.org/10.11988/ckyyb.20150622

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  As a time-dependent property of concrete material, creep imposes significant influence on the stress of early age concrete. However, it is difficult in engineering to calculate the creep stress by using common available finite element programs. In view of this, through further development of the ANSYS user subroutine usermat, a userdefined material model was developed to introduce the implicit solution to the concrete creep equation. With the largest error lower than 0.3 MPa, the user subroutine usermat was verified through calculation examples and was applied to engineering. The results of the implicit concrete creep equation are in good agreement with measured values, and their variation trends are the same. The user subroutine usermat can be applied to engineering to predict and calculate the thermal creep stress of early age concrete.
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  Effects of Water-cement Ratio and Metakaolin Blending Ratio on the Performance of Sulphoaluminate Cement-based Material

  HE Kai,YAN Shao-jun,ZHAO Mang,DOU Yan,ZHAI Guo-lin

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 143-148. https://doi.org/10.11988/ckyyb.20150501

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  To study the influences of water-cement ratio and metakaolin blending ratio on the fluidity, shrinkage and mechanical properties of sulphoaluminate cement, we take Longmen Grottoes as an example, and carry out tests on fluidity, mechanical properties and dry shrinkage property. The results show that, firstly, the initial fluidity of sulphoaluminate cement is proportional to water-cement ratio and metakaolin blending ratio; secondly, the higher water-cement ratio is, the lower microexpansion rate is, even with a little contraction. In general , expansion rate increases with metakaolin blending ratio; compressive strength is inversely proportional to water-cement ratio and metakaolin blending ratio; the flexural strength of specimens cured for 7 days decreases with the increasing metakaolin blending ratio, while the flexural strength of specimens cured for 28 days is on the contrary; flexural strength decreases with the increasing water-cement ratio, and the decline rate is relatively large; bonding strength increases first and then decreases with the increasing water-cement ratio; while with increasing metakaolin blending ratio, bonding strength increases overall, and in particular, peak value occurs under water-cement ratio of 0.5. The experimental results provide theoretical basis for the field grouting test in Longmen Grottoes, and also provide reference for grouting repair in similar stone cultural relics.
INFORMATION TECHNOLOGY APPLICATION
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  Decision Support Platform of Temperature Control for RCC High Arch Dam in Construction Stage

  PEI Liang, XU Jian, HE Kun, WU Zhen yu, CHEN Jian kang

  Journal of Changjiang River Scientific Research Institute. 2016, 33(9): 149-153. https://doi.org/10.11988/ckyyb.20150582

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  Cracking in high concrete dam is a common problem. Many concrete dams in China and abroad are forced to shut down due to cracks in construction. The process of pouring high concrete dam is affected by natural environment, structure, temperature control, resources and other factors. It is necessary to develop a practical plan of dam construction by considering these factors. Real time monitoring and scientific management of concrete temperature and stress during construction are also requisite. Research and development of decision support system for concrete dam construction can provide advanced management approach for the construction and safety of hydroelectric dams, and potential benefits will be huge. With the project of Lizhou hydropower station as research background, a temperature control decision support platform for high RCC arch dam is developed. Through this platform, data information such as rolling parameters, temperature control information, monitoring data and simulation results are efficiently managed. Moreover, the effect and trend of temperature control are realtime monitored and predicted, earlywarning is accomplished and decisionsupport from experts remote consultation is provided. These results are of important significance for promoting the scientific level of construction temperature control decision support for high RCC arch dam and ensuring the construction quality.