01 November 2019, Volume 36 Issue 11

    

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SPECIAL CONTRIBUTION
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  Properties of Soil Reinforced by Waste Tire

  LI Li-hua, YU Chang-dao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 1-6. https://doi.org/10.11988/ckyyb.20190233

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  In this paper, the effect of waste tire reinforcement on soil strength and slope stability is studied by laboratory tests. First of all, the stress-strain relationship and shear strength index of plain sand reinforced by waste tire were studied by consolidation drainage shear triaxial test. Furthermore, the effects of single reinforcement of geocell and composite reinforcement of waste tire and geocell on the stability of embankment slope are compared and analyzed via embankment model test. Results demonstrate that waste tire reinforcement improves the shear resistance of soil obviously, and the more layers of tire reinforcement, the better the deformation resistance and the greater the strength of specimens; the embankment model test shows that composite reinforcement of waste tire and geocell is prior to single reinforcement of geocell as the former significantly reduces the settlement, lateral displacement and additional peak stress of embankment and effectively improves the stability of embankment slope. In addition, the similarities and differences between the mechanism of tire reinforcement and geocell reinforcement are discussed.
WATER RESOURCES AND ENVIRONMEN
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  Spatiotemporal Variations of NDVI in Terrestrial Ecosystem in Yangtze River Basin and Response to Hydrothermal Condition

  YUAN Zhe, YU Zhi-qiang, FENG Zhao-yang, XU Ji-jun, YIN Jun, YAN Bo, LEI Heng

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 7-15. https://doi.org/10.11988/ckyyb.20180149

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  In order to identify the spatiotemporal variations of NDVI in terrestrial ecosystem in Yangtze River Basin and its response to hydrothermal condition, we analyzed the interannual changes of NDVI, accumulated temperature, precipitation and their correlations in the Yangtze River Basin based on the MODIS NDVI, temperature and precipitation data in 2000-2015 using time series analysis techniques. Results revealed that: (1) The NDVI displayed a significant increasing trend in the Yangtze River Basin in recent 16 years. The growth rates of NDVI in farmland, forest, water and wetland ecosystem were larger than those of others. (2) Precipitation increased slightly in the whole basin with evident spatial heterogeneity. Accumulated temperature above 10 ℃significantly increased and generally presented increasing trend in spatial scale. (3) Due to differences in climate and ecosystem patterns, the correlation between NDVI and precipitation and accumulated temperature above 10 ℃varied in different zones. In general,precipitation is not a restrictive factor for vegetation growth in the Yangtze River Basin. The correlation between NDVI and precipitation is not significant. But for forest, grassland and desert ecosystems, NDVI and accumulated temperature present a more significant positive correlation, indicating that heat condition is a restrictive factor of vegetation growth in the Yangtze River Basin.
FLOOD PREVENTION AND DISASTER REDUCTION
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  Simulation of Rainstorm Waterlogging Process in Urban Areas Based on Soil Conservation Service Model and Geographic Information System

  CHEN Si, YANG Sheng-mei, MA Kun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 16-20. https://doi.org/10.11988/ckyyb.20180340

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  A method of simulating the urban waterlogging process caused by rainstorm is presented. The method integrates the urban storm intensity formula in Chinese standard, the Chicago rainfall process model, the SCS (soil conservation service) runoff model by US Secretary of Agriculture, and the local isometric method based on ArcGIS. With Tangxun Lake catchment in Wuhan as a research object, the waterlogging elevation and submergence area in the presence of rainstorm of varied reoccurrence periods are obtained through simulation using the proposed method. Results reveal severe waterlogging in the Tangxun Lake catchment. Rainstorm of ten-year reoccurrence period would give rise to slight waterlogging; but the area of waterlogging does not change with the reoccurrence period of rainstorm. Rainstorm with longer reoccurrence period would cause larger submergence depth, wider submergence range, and severer impact on surrounding areas.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  Quantitative and Reliability Analysis of Measured Steel Bar Stress in Large Aqueduct

  WANG Yu, HUANG Yao-ying, LIU Yu, XIAO Lei, YUAN Bin

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 21-26. https://doi.org/10.11988/ckyyb.20180387

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  The working condition of aqueduct can be analyzed effectively by mathematical monitoring model based on measured data. The reliability of measured steel bar stress, however, is difficult to be confirmed as the mathematical model is prone to be affected by the experience and multicolinearity due to the complex working conditions of aqueduct. In this research, the statistical model and mixed model of measured steel bar stress of a large aqueduct were established based on measured data; subsequently, the parameters of the established models were estimated using stepwise regression and compound model method to compare the water pressure components separated by different models. The analysis result showed that although the measured stress of steel bar No. 2 in the aqueduct is somewhat regular, the variation law of the water pressure component separated by different analysis methods does not conform to the general laws of mechanics. Therefore, the measured value of the steel bar is considered abnormal and unreliable, hence cannot be employed to analyze the actual status of aqueduct.
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  Simulation on the Deformation and Failure Mechanism of Yunpantou Landslide, Guizhou

  ZHANG Ling-xi, CHEN Jun, LIU Lian-jia, WANG Qi, CHI Chang-feng

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 27-33. https://doi.org/10.11988/ckyyb.20171097

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  The instability of gently inclined bedding rock slope is difficult to be recognized and detected because of its gentle dip angle. The Yunpantou landslide in Guizhou, China, is a typical gentle dip bedding rock slope with four sets of weak intercalated layers in the slope. Probing into its deformation and failure mechanism is of practical significance for the research of gently inclined bedding rock slope failure. In this paper, the deformation and failure mechanism of Yunpantou landslide is examined by establishing a geological structural model based on engineering geological survey in association with various approaches such as bottom friction test, two-dimensional discrete and finite element simulations. Results reveal that the deformation and failure process of landslide can be divided into four stages, namely, microcrack growth stage, crack propagation stage, landslide deformation stage, and complete destruction stage. Key blocks exist in slope toe. The main causes of the landslide can be depicted as the exposure of weak intercalated layers resulted from excavation, and tension cracks perpendicular to the weak layers developed and divided the sliding body into blocks; with the sliding of key blocks in slope toe towards the free face, secondary blocks moves correspondingly and generates a Domino effect leading to the integral sliding of slope, which, therefore, is a typical sliding tension landslide.
HYDRAULICS
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  Combinatorial Calculation Method for Sill Height and Depth of Comprehensive Stilling Pool

  HUANG Chao-xuan, DING Xi-nan

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 34-39. https://doi.org/10.11988/ckyyb.20180140

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  Traditional trial calculation method for the sill height and depth of stilling pool for energy dissipation is burdensome, and in particular, the calculation of submergence coefficient requires repeated check. In view of this, in the light of dimensionless principle, a simple analytical solution to submergence coefficient is given through mathematical deduction and numerical analysis in MatLab. The solution is of high precision with the maximum relative error only 0.405%, favorable for engineering application. Moreover, the analytical formula of conjugate water depth after jump with dimensionless unit width discharge parameter λ is given, and a concise analytical formula of dimensionless sill height is also presented. In addition, the two-dimensional surface diagram of dimensionless sill height with dimensionless unit width discharge, downstream water depth, and stilling pool’s depth are obtained. The calculation formula for the extreme value of sill height under the most unfavorable energy dissipation condition is also given. The depth of stilling pool and sill height displays an approximate negative linear relation, which is affected by submergence coefficient and dimensionless parameter K. Two engineering calculation examples verify that the formulas proposed in this paper are highly precise and convenient.
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  Application of Large Sample Data Analysis Method to Flow Calculation of Medium and Small Rivers

  CAO Hao, WANG Cheng-gang, LI Ji-tao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 40-44. https://doi.org/10.11988/ckyyb.20190303

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  Traditional flow measurement methods (e.g. flow meter method, buoy flow measurement method, index flow rate method, specific drop area method, etc.) for most small and medium-sized rivers at present are featured with large investment and large time consumption. In association with traditional sectional flow calculation theory and the latest surface velocity measurement technology, we propose a method of determining the stage-discharge relation of river section via inputting large sample data of surface velocity and sectional water level. This method needs only a small amount of observed flow data at medium and high water levels to calculate flow rate and fit the stage-discharge curve. Compared with traditional methods, the proposed method reduces the workload of flow rate measurement required for fitting the stage-discharge curve, and cuts down the errors brought about by measurement, hence enhancing precision. It is also convenient for operation with low cost.
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  Mechanism of Hydraulic Characteristics of Submerged Jet in Dissipation Well with Inclined Inlet

  JIAO Xuan, QIU Yong, RUAN He-chun, YU Yuan-hao, WANG Shang-jin

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 45-49. https://doi.org/10.11988/ckyyb.20180801

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  Yunnan is located in the plateau mountainous area with varying hydrological meteorological condition, steep topography and complex engineering geology condition. When conventional energy dissipation work does not adapt, dissipation well is a feasible alteration. However, the hydraulic characteristic of dissipation well with inclined inlet is rarely studied. In this paper, the mechanism of water force in the presence of submerged jets in dissipation wells with inclined inlet and outlet under a certain longitudinal slope condition is examined based on turbulence jet division in the well. And furthermore the expressions of the maximum velocity of jet along the flow and the time-averaged impact force on the shaft wall in impact zone under the oblique inlet condition are deduced. The parameters of the semi-empirical formula under longitudinal slope condition are determined in association with hydraulic test. The research results offer reference for the design of similar projects.
ROCK-SOIL ENGINEERING
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  Cataclastic Loose Rock Mass on the Abutment Slope of a Hydropower Station: Development Characteristics and Excavation Deformation Response

  ZHENG Da, WANG Yu, YAO Qing, LI Wen-long

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 50-56. https://doi.org/10.11988/ckyyb.20180336

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  Field survey on the left abutment slope of a hydropower station on the Lancang River reveals a type of special rock mass with fragmented structure and significant loosening deformation synchronously. On this basis, we put forward the concept of cataclastic loose rock mass. Study on its development characteristics unveils that the cataclastic loose rock mass features with granular structure, cataclastic structure, and block structure from the slope surface to the interior, and its development depth corresponds well to the extremely-strong unloading zone. In view of this, we put forward the division standard: the depth of the rock mass with granular structure, cataclastic structure and block structure is regarded as the development depth of cataclastic rock mass, while the depth of the extremely-strong unloading zone is the depth of its unloading zone; and the average value of the two is determined as the ultimate development depth. In order to prove that the result acquired by this standard can be used to guide the excavation of the slope, we performed simulations using UDEC. Results demonstrated that after the excavation of the slope, besides the dangerous rock in a small scale near the excavation face, the overall deformation is small, and the stability is good. Therefore, we recommend to excavating the slope along the division depth of the cataclastic rock mass, and the excavation slope ratio above and below 2 880 m height is 1∶1.5 and 1∶1, respectively.The results prove that the division of cataclastic loose rock mass provides reasonable reference for the excavation depth in such special slope rock mass.
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  Experimental Study on Triaxial Creep Mechanical Behavior of Water-bearing Sandstone

  ZHANG Chun-mei, CUI Guang-qin, BAO Xian-kai

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 57-61. https://doi.org/10.11988/ckyyb.20180504

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  The roof of roadway in mine has strong creep characteristics under the action of water, posing great threat to mine excavation and production. In this research we investigated the creep mechanical behavior of sandstone in different water-bearing conditions through triaxial rheological compression test. Test results showed that: (1) with the increase of water-saturation time and the climbing of stress level, instantaneous strain and creep both increased. (2) With the enhancement of water-bearing state, the initial creep rate and steady-state creep rate gradually increased, and the steady-state creep rate was in a power function relationship with the stress level.(3) By comparing two different long-term strength methods, we found that the long-term strength of sandstone under conditions of natural state, water-saturated for 1 day, and water-saturated for 5 days was only 64.12%, 62.08% and 59.34% of its instantaneous strength, respectively,and the long-term strength attenuation aggravated under the action of water.
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  A Statistical Method for Shear Strength Parameters of Rock Foundations Based on Field Test Data Fragments

  LAI Guo-wei, ZHOU Wei, LI Jia-nan, XU Jian-qiang

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 62-68. https://doi.org/10.11988/ckyyb.20190140

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  According to experimental data fragments by the principle of close precision, namely, close number of test blocks, and based on mathematical statistics theory, we derived formulas for calculating the statistical parameters of the frictional coefficient and cohesion of rock foundations directly from the normal stress and shear stress on the shear plane of each block in the in-situ shear test. The method takes into consideration the correlation between frictional coefficient and cohesion. In subsequence, in line with the random simulation method of probability theory and the orthogonal transformation theory of linear algebra, we proposed a computational random simulation evaluation method for verifying test block methods according to the characteristics of shear test. The method can also be applied to the verification of other probability statistical methods of frictional coefficient and cohesion considering the discretization of shear strength of test blocks. By applying the computational random simulation method, we evaluated some test block methods and verified the validity of the proposed formulas. We also discussed the total number of minimum test blocks for the test block method. Finally, shear strength parameters of some engineering examples are analyzed statistically, and some statistical characteristics of friction coefficient and cohesion are given.
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  Failure Modes and Early Identification of Typical Loess Collapse in Shanxi

  LIU Xiang-yu

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 69-75. https://doi.org/10.11988/ckyyb.20181280

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  In view of the concealment and abruptness of loess collapse, the early identification and prediction of loess collapse were investigated, and corresponding emergency prevention measures were proposed. The characteristic factors for early identification of loess collapse were first of all extracted based upon summary on the inducing factors of loess instability via classifying the failure modes of loess in Shanxi Province. Subsequently, the risk of loess collapse was analyzed semi-quantitatively by using comprehensive index method, and on the basis of the quantitative result, the criterion for rating the risk of loess collapse was proposed, and emergency prevention measures were presented corresponding to different risk levels. Research result showed that: (1)the deformation and destruction of loess collapse mainly happened in four kinds of rock and soil structure combination and five typical damage contact surfaces;(2)the risk of loess collapse can be divided into four levels, namely, high level, medium level, relatively low level, and low level, each should be followed with corresponding emergency response measures such as emergency avoidance, disaster monitoring, emergency investigation, exploration and treatment;(3)early warning and forecasting measures for geological hazards can be directly taken when the deformation indication score reaches “high risk” of the judgment level.
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  Particle Flow Simulation of Macroscopic and Mesoscopic Bearing Capacity of Multistage Rotated-expanded Pile

  HUANG Sheng-gen, FU Ming, HU Ran, LI Zhong-shuang, SHEN Jia-hong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 76-82. https://doi.org/10.11988/ckyyb.20160988

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  Multistage rotated-expanded pile carrying vertical load are simulated using DEM software PFC^2D to reveal the bearing behaviors and the interaction between pile and soil. Test results show that: (1) With the increase of load in the process of loading, the side friction of the upper part of pile, the friction of diameter-expanding segment of pile, and the pile tip resistance plays the role of bearing in turn. (2) When the load is small, load is mainly composed of side friction of pile; with the increasing of load, the diameter-expanding segment of pile undertakes a rapidly increasing rate of the load; and when the load continues to increase, the increment is mainly and increasingly undertaken by pile tip resistance. (3) With the increase of load in the process of loading, the porosity of surrounding soil, the coordination number between the levels of soil, the horizontal and vertical stresses of pile, and the soil particle displacement surrounding pile are in regular changes.
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  Bearing Capacity of Foundation Affected by Buried Depth of Culvert

  FENG Zhong-ju, LI Shao-jie, HAO Yu-meng, DONG Yun-xiu, FANG Yuan-wei, HU Hai-bo, PAN Fang, LI Jun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 83-90. https://doi.org/10.11988/ckyyb.20180316

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  In an attempt to identifying the influence of buried depth of culvert on the bearing capacity of foundation, a formula for the bearing capacity of buried culvert is deduced based on Terzaghi’s theory and Gu Anquan’s formula. Moreover, the allowable value of foundation’s bearing capacity is determined by analyzing the change of load-settlement curve against soil fill height using finite element approach. The allowable bearing capacity of foundation obtained by finite element method is compared with those by different calculation methods. In addition, the influence of shear strength of foundation soil on bearing capacity of foundation in different calculation methods is discussed. Finally, the rationality of the formula is verified by an engineering example. The research findings are as follows: (1) The side soil fill reinforces the shear strength of foundation soil and improves the bearing capacity of the culvert foundation. Such improvement is influenced by the additional soil pressure on the soil fill. (2)With the increase of internal friction angle, the bearing capacity of foundation increases nonlinearly, while with the increase of cohesion,bearing capacity increases in an approximately linear trend, and the impact of internal friction angle is much larger than that of cohesion. The influence of the internal friction angle on the bearing capacity of the foundation is significantly greater than that of the cohesive force.(3)The bearing capacity calculated by the formula proposed in this paper is in good agreement with the calculated value by finite element method, and also is much larger than the earth pressure at culvert base, which accords with the actual situation of the culvert foundationin a safe state.
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  Crack Propagation Law of Compacted Expansive Soil with Various Original Compactness and Water Content

  LIU Guan-shi, CHEN Yong-gui, ZHANG Gui-bao, ZENG Xian-yun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 91-97. https://doi.org/10.11988/ckyyb.20180284

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  Crack is a crucial factor that affects the mechanical properties of expansive soil. Expansive soils taken from Nanyang Expressway (Henan Province, China) were compacted to big-size samples with various original water content and compactness, and then the samples were desiccated gradually in a closed greenhouse where a camera was used to record the propagation of cracks on the surfaces of samples. The captured images were analyzed quantitatively using self-compiled program of MatLab to obtain the characteristics of surface cracks which were further used to explore the laws of crack propagation. The results suggest that the course of crack propagation in compacted expansive soil samples can be divided into three stages: in the first stage minor cracks aroused and developed quickly; then main cracks emerged and cracks reached peak in the second stage; at last the cracks withdrew and remained stable in the third stage. The higher the original water content was, the faster the cracks on the surfaces of expansive soil samples developed, the higher the extent of crack development was, and the longer the crack development lasted; the higher the original compactness, the smaller the surface crack ratio and total length of expansive soil samples were, but the larger the crack width was. The above results can be explained by the mechanism of superficial evaporation and water transformation in the soil.
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  Influence of Topographic and Geomorphic Conditions on the Dynamic Response of Slope Acceleration

  TANG Wei-min, MA Shu-zhi, LIU Xiao-lang, ZHAO Xuan

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 98-103. https://doi.org/10.11988/ckyyb.20180443

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  In this paper, we designed and conducted a set of shaking table model tests of soil slope according to the topographic and geomorphologic conditions of the slope. Based on the results, we examined the influence of the topographic and geomorphologic conditions on the dynamic response of the soil slope and studied the reaction mechanism of slope under earthquakes. Results demonstrated that the dynamic response of soil slope was closely related to the elevation of the slope. The amplification coefficient of peak ground acceleration (PGA) along the slope surface and in the vertical direction of the slope increased with the elevation increasing, and the amplification effect of soil inside the slope to earthquake waves was more significant than that of slope surface in the horizontal direction. The topographic and geomorphologic conditions of the soil slope had great influence on the amplification effect of earthquake waves. Generally, if the slope is steeper and more complex in shape, the amplification coefficient of PGA and the deformation of the slope will be greater.
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  Reinforcement Mechanism and Effectiveness of Anti-shear Galleries in the Right Bank of Dagangshan Hydropower Station in the Process of Reservoir Impoundment

  LIU Xing-zong, TANG Chun-an, SUN Run

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 104-109. https://doi.org/10.11988/ckyyb.20180288

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  The mechanism and effectiveness of reinforcing the right bank slope of Dagangshan hydropower station by replacing weak zones with anti-shear galleries during water storage are investigated. According to microseismic monitoring, the major damage regions in the right bank slope are identified; microseismic activities concentrates in the vicinity of anti-shear galleries at 1 240 m, 1 210 m, 1 180 m, and 1 150 m, mainly induced by tention fractures. Moreover, the stress field and displacement field during impounding are obtained by numerical simulation in RFPA (realistic failure process analysis) code to explain the microseismic activities of anti-shear galleries: stress concentration and failure are prone to occur around the anti-shear galleries which is in tension state. In association with the numerical results together with the microseismic-monitoring data, macro-shear and micro-tension are found to be the failure mode of anti-shear galleries. In the early stage of impounding, anti-shear gallery affects the stress distribution in the bank slope, and refrains from penetrative plane of fracture. Meanwhile, anti-shear gallery could enhance the anti-shear ability of bank slope; however such effect attenuates with the decline of elevation. In general, anti-shear galleries are conducive to the stability of bank slope during impoundment.
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  Factors Influencing Deformation of Subway’s Deep Foundation Pit Based on Quantification Theory III

  WANG Fei

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 110-114. https://doi.org/10.11988/ckyyb.20180405

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  In the purpose of assessing objectively the influencing factors of subway foundation pit’s deformation and improving the targeted controlling of pit deformation, we examined the influence degree of various factors using quantification theory III with 30 pit examples as engineering background. We identified the coupling strength among the factors according to sample scores under different conditions and evaluated the accuracy of selecting factors by constructing BP neural network with different input layer conditions. Results revealed leading factors inclusive of permeability coefficient, foundation pit depth, support spacing and embedded depth; important factors, namely, internal friction angle, cohesive force, length of foundation pit, width of foundation pit and groundwater level; and general factors including natural unit weight and stiffness of support structure. The coupling degrees among the influencing factors are mainly at medium and low level. The optimized BP neural network has a higher prediction accuracy than traditional BP neural network, which verifies the accuracy of the quantitative theory III in screening the influence factors of foundation pit deformation. Through this study, the applicability and effectiveness of the quantitative theory III in the analysis of the influence factors of foundation pit deformation are proved, which provides some reference for the deformation control of foundation pit.
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  A Quick Determination Method for Side Resistance of Pile

  MU Rui, GUO Jian-qiang, HUANG Zhi-hong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 115-119. https://doi.org/10.11988/ckyyb.20180199

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  The stress and deformation of pile-earth/rock coupling system is a complex mechanics issue. In this paper, a model for the quick determination of pile’s side resistance is established based on continuous medium theory according to the deformation coordination condition (the deformations of soil/rock and pile differ by n times at the moment of separation between soil/rock and pile). The pile-soil/rock complex is considered as a layered material composing geologic materials with different stiffness. The research findings are as follows: (1) The side resistance of pile is manly affected by E_s/E_p the ratio of soil/rock’s elastic modulus to pile’s elastic modulus; the greater E_s/E_p is, the more remarkable side resistance changes. (2) Side resistance of pile declines when the soil squeezing effect gets more evident. (3) The test dafa of the engineering test piles are verified by the rapid determination model for pile foundation’s side resistance. The results show that it is feasible and effective to use the model to predict the lateral resistance of similar pile foundations.
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  Influence of Granite Residual Soil Softening in Passive Zone of Deep Excavation

  SU Hua, HAO Yong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 120-124. https://doi.org/10.11988/ckyyb.20180180

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  The softening and then disintegration of granite residual soil encountering water often pose great difficulties to construction and security threats to foundation pit and surrounding environment. With the deep excavation of a metro station in granite residual soil zone as case study, we probed into the influence of granite residual soil softening at the bottom of excavation encountering water through PLAXIS finite element simulation. Results illustrated that the maximum horizontal displacement of support structure, the deformation of skirting, and the maximum ground settlement all raised with the deepening of softened soil. When the depth of softened soil was small, the above deformations were small too; when the depth of softened soil was large, the above values surged correspondingly. Moreover, the location of maximum horizontal displacement and the maximum bending moment also increased with the deepening of softened soil. The inner bracing around excavation face undertook more shift pressure as the depth of softened soil increased. Therefore, the depth of softened soil in passive zone should be reduced in the deep excavation in granite residual soil zone. The research finding serves as an experience for similar construction.
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  Stability Analysis of Geogrid Reinforced High Earth-rockfill Dam under Seismic Action

  MA Chi, ZHU Ya-lin, PENG Xue-feng

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 125-131. https://doi.org/10.11988/ckyyb.20180466

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  Pseudo-static method has some limitations in obtaining the minimum safety factor to evaluate the stability of slope. In view of this, we developed a method for calculating the time-history of safety factor using FISH language through the secondary development platform of the finite-difference software FLAC^3D. Via the modified Mohr-Coulomb constitutive model we simulated the slope stability of geogrid-reinforced high earth-rock dams, and analyzed the slope stability of geogrid-reinforced high earth-rock dams according to the time-history of safety factors. According to the simulation, we obtained the changes of safety factor in the presence of varying geogrid parameters (including material strength, geogrid length, and geogrid spacing), and determined the optimum layout of geogrids. Results demonstrated that we could analyze the time-history of safety factor by the time-history graph of dynamic safety factor, and also analyze the start time of the failure of dam slope. Moreover, the reinforcement effect reaches the optimum when the elastic modulus of geogrid is 2.5 GPa and the spacing of geogrids is 4 m. The simulation results of Shuangjiangkou Rockfill Dam are basically consistent with the results in the feasibility research results. The geogrid layout is proved rational, and the simulation method in the present paper is effective.
HYDRAULIC STRUCTURE AND MATERIAL
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  Three-dimensional Finite Element Modeling of Contact Dissolution of Cement-based Materials

  JIA Pan, SHE Cheng-xue

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 132-139. https://doi.org/10.11988/ckyyb.20180448

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  Numerical simulation is an effective means to study the contact dissolution of cement-based materials; but the problem regarding its 3D finite element modeling has not been effectively solved. In view of this, attempts were made to build a 3D calcium dissolution model. First of all, the governing equation of calcium ion transmission was deduced in line with the mass conservation law, and on this basis a 3D mathematical model of calcium ion transportation was built based on the solid-liquid equilibrium curve, the porosity evolvement model and the effective diffusion coefficient evolvement model. The ion exchange boundary condition is incorporated to reflect the change of calcium ion concentration at the contact boundary, which provides the basis for calculating the quantity of calcium dissolution. Furthermore, according to the Galerkin finite element method, the finite element computing scheme is derived for numerical solution of the proposed model. The proposed model and FEM program is validated with two examples. Result demonstrates that the proposed model is applicable to simulating the multidimensional contact dissolution of cement-based materials. The spatial distribution and temporal distribution of characteristic variables are obtained by the numerical test of three-dimensional contact dissolution of a cylinder specimen. In 3D state, the contact dissolution develops from the surface to the inside, the dissolution rate varies from fast to slow in the same position, and the radial dissolution rate is larger than axial dissolution rate. The research achievements offer theoretical basis and approach for analyzing the impact of dissolution of cement-based material.
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  Stress and Deformation of Asphalt Concrete Core Wall Dam in Consideration of Spatial Difference: Stochastic Finite Element Analysis

  GUO Qing, LIU Dong-hai, CHEN Hui

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 140-146. https://doi.org/10.11988/ckyyb.20180488

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  Previous finite element calculation of asphalt concrete core wall dam is usually performed according to the designed parameters of dam material. However, due to the uncertainty of actual construction quality, the parameters of dam material differ in space. In consideration of such spatial difference, a stochastic finite element analysis method based on Monte-Carlo method is proposed for the stress and deformation of asphalt concrete core wall dam. The distributions of stress and deformation of asphalt concrete core wall dam are obtained and compared with those in designed condition. The impact of spatial difference on stress and deformation is examined, and the probabilities of stress and deformation exceeding those in designed condition are determined as well. Results reveal that deterministic analysis method underestimates the stress and deformation of dam with a 50% probability and the maximum principal stress with a 43% probability; while the result of the present method has a 50% probability of exceeding the designed value in terms of settlement at different positions, and even larger probability in principal stress. The research achievements offer reference for dam safety analysis and design optimization, and can be regarded as a new approach for fine finite element analysis of dam.
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  Influence of Straw Form on Physico-mechanical Properties of Cotton Straw-Expanded Polystyrene Composite Block

  WU Gang, AN Qiao-xia, XUE Yan, YU Jie, BAI Zhi-hao, CHENG Xue-jun, ZHANG Ren-hai

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 147-151. https://doi.org/10.11988/ckyyb.20180346

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  In the aim of preparing cotton straw-expanded polystyrene (EPS) composite block with good mechanical properties, we probed into the influence of straw form on the physico-mechanical properties of the block. The form of straw was classified as particle, chip, and fiber according to length and particle size of straw. Result showed no significant effect on the early mechanical properties of block by straw form. However, when the mix proportion was fixed and the length and size was small (particles), the block of 28-day age or above had the largest compression strength, anti-splitting strength and axial compressive strength, reaching 6.95 MPa, 0.93 MPa and 6.88 MPa, respectively; when the particle size of straw increased (chips), the compression strength, anti-splitting strength and axial compressive strength of the block declined; when the length of straw increased (fiber), the flexural strength and elastic modulus of the block were the largest, amounting to 1.44 MPa and 80.42 MPa, respectively; but the elongation of straw fiber also instigated the water absorption of blocks. In conclusion, the form of straw has remarkable influence on the physico-mechanical properties of cotton straw-EPS block. We should select proper straw form according to specific engineering requirement.
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  Mechanical Properties and Frost Resistance of Cement-stabilized Clastic Rock Material with Time-varying Paste Viscosity

  ZHANG Qi, PEI Xiang-jun, ZHANG Xiao-chao, GAO Hui-hui, RAN Yao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 152-156. https://doi.org/10.11988/ckyyb.20180491

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  The aim of this study is to investigate the performance of cement-stabilized clastic rock material used for road in high and cold mountainous region. Self-developed slurry with time-varying viscosity (SJP) was selected as the cementitious material for the cement-stabilized clastic rock material. Unconfined compression test and cyclic freezing-thawing test were performed to examine the mechanical properties of the SJP-stabilized material, and SEM scanning for the frost resistance. Results demonstrate that the SJP-stabilized material has faster early strength growth and higher later strength than ordinary material. SJP reduces the mass loss rate of material after cyclic freezing and thawing, and improves the frost resistance coefficient. With the aid of SJP, the combination between C-S-H and fibrous hydration products strengthens, hence enhancing the bonding force and making the aggregates bond more closely, effectively decelerating the accumulation of damage of water-stable materials under freezing-thawing conditions and improving the durability of road base.
INFORMATION TECHNOLOGY APPLICATION
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  Design and Implementation of Integrated Management Information System Based on MiniUI

  SONG Pu-bin, YANG Jun, LIU Pei

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 157-161. https://doi.org/10.11988/ckyyb.20180776

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  In order to cope with the complex and changeful office environment and business demands, and to solve the problems encountered in the existing Office Automation system, such as heavy development tasks, tedious front-end scripts, and poor system compatibility, we propose a system design idea using MiniUI as the front frame. Based on the rich control library provided by MiniUI, we design the front-end script via configuration instead of coding, which greatly reduces the amount of code and shortens the development cycle. In practical application, the integrated management information system not only realizes rapid development, but also has good compatibility.
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  Real-time Integration of Massive Video Stream and 3D Scene

  YE Song, CHEN Zhe, KAN Hong-tao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 162-166. https://doi.org/10.11988/ckyyb.20180217

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  Video surveillance system is one of the most important tools for security protection. In this article, the multi-channel video sequence is obtained by decoding the video stream, and then the video texture mapping is completed by estimating the pose of video camera through the registration of the 3D model and the video texture. Moreover, texture fusion technology is used to eliminate the color difference seams between each channel and finally the real-time projection is achieved. The experiment result illuminates the advantage of this arithmetic and the idea of rendering the live video on 3D model. The idea of rendering the multi-channel video on three-dimensional scene can make it convenient to record the real images and grasp the real-time monitoring of the scene information for monitoring site security, which provides the basis for safety protection and emergency disaster warning and rescue.
INSTRUMENTATION DEVELPMENT AND TESTING TECHNIQUES
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  Retrieving Suspended Sediment Concentration by Using Water Surface Points of Infrared Laser and Green Laser in Airborne LiDAR Bathymetry

  ZHOU Feng-nian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(11): 167-170. https://doi.org/10.11988/ckyyb.20190455

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  High-precision estimation of sediment concentration in water can be achieved by using the waveform data of airborne LiDAR bathymetry (ALB). However, waveform data is difficult to be obtained and utilized. In view of this, a simple method to retrieve the sediment concentration using ALB 3D point cloud data is proposed. Firstly, the green laser water surface penetration is calculated based on the green laser water surface point and the infrared laser water surface point. Secondly, the empirical model of Suspended Sediment Concentration (SSC) is constructed by using the measured SSC and the corresponding green laser water surface penetration. Finally, the sediment content of the lower water body is obtained conveniently by the constructed SSC empirical model. Experimental results validate that the method is effective and has the inversion accuracy of SSC better than 20 mg/L. The proposed method provides a simple and fast approach to estimate SSC.