Home Table of Contents

01 December 2020, Volume 37 Issue 12
    

  • Select all
    |
    SPECIAL CONTRIBUTION
  • YU Wen-chou, LUAN Hua-long
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 1-7. https://doi.org/10.11988/ckyyb.20200579
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Tongzhou shoal channel in Chengtong Reach of the lower Yangtze River is a typical bifurcation channel with multiple shoals as well as complex and variable river regime and waterway condition under combined riverine and tidal forcing. After river and waterway regulation projects in recent years, the flooding and ebb currents converged along the main west channel of the Tongzhou Shoal, alleviating the channel’s silting and shrinking. However, the west channel was unable to maintain its water depth after dredging and will adjust and approach to equilibrium, whereas the local river regime of the east channel tended to be unfavorable. The mainstream of upstream segment of the Longzhuayan node moved rightward and the shoals and channels intertwined. The right side of the Tongzhou shoal was scoured, with a trend of further scour along the connecting channels on the Tongzhou shoal. The marginal shoal near the Yingchuan port in the segment downstream the Longzhuayan node was scoured to the left, and the submerged shoals -10 m under the tail of Xinkai shoal was scoured, which is unfavorable to navigation. Measures should be taken to protect the right side of the east channel in time, to renovate the Xinkai shoal, and to consider reclamation of the Tongzhou shoal. Such measures are conducive to maintain the long-term stability of the shoals and the flow diversion pattern of the bifurcation channel.
  • WATER RESOURCES AND ENVIRONMENT
  • LI Wei, ZHAO Liang-yuan, ZHAO Wei-hua, GUO Wei-jie, QIAO Qiang-long, LIU Min
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 8-13. https://doi.org/10.11988/ckyyb.20200725
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Herzensteinia microcephalus (Herzenstein, 1891) is endemic to China and only lives in the Qinghai-Tibetan Plateau. It is a key species in the aquatic ecosystem. However, artificial propagation technology has not yet been developed until June 2020 when sixteen parent fish (2 females and 14 males) with gonads in matured V stage were selected at 4 800 m a.s.l in the Dangqu River, the southern headwaters of the Yangtze River. Eleven thousand fertilized eggs were incubated at 4 767 m in-situ in daily rhythm with water temperature range of 8.3-16.0 ℃, dissolved oxygen greater than 5 mg/L, pH (7.7±0.2), salinity (0.13±0.1) psu, ammonia nitrogen less than 0.1 mg/L, and total suspended solids (TSS) concentration (3±0.5) mg/L. Results showed that the parent fish matured well, the oocyte diameter at stage V was (2.4±0.2) mm, the total length of the male fish was about 1/2 of the female (40.3±3.5) cm, and the weight was about 1/10 of the female (435.2±67.5) g. The fertilization rate reached 99% when the water temperature for fertilization was 16.3 ℃. On the 10th day of incubation (238-240 h), when the accumulated temperature was 3 057 h·℃, large-scale egg envelope-breakdown occurred. The total length of the newly hatched larvae was 0.9-1.0 cm, and the hatching rate reached 80% after the implementation of the critical water temperature 19 ℃ as egg envelope breakdown triggering. The breakthrough of artificial propagation technology is conducive to the natural population restoration, conservation of the Herzensteinia microcephalus and to reveal embryonic response of Herzensteinia microcephalus to the climate warming in the Qinghai-Tibetan Plateau.
  • ZHOU Ting, QI Wang-yue, JIN Ju-liang
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 14-21. https://doi.org/10.11988/ckyyb.20191117
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    With the expansion of scale and the complication of structural functions of reservoir groups, structural analysis has been playing an increasingly important role in the optimizing dispatching of reservoirs. The aim of this study is to identify the applicability, advantages and disadvantages of different structural analysis methods and to provide an efficient structural analysis method for reservoir groups with complicated structure. On the basis of research achievements in the past six decades, we reviewed the advances in five structure analysis methods, namely, sequential simulation method, water supply discriminant method, equilibrium with utility theory, aggregation-decomposition method, and hydraulic connection method. Sequential simulation method is logical, intuitive and universal, while water supply discriminant method could quickly sort the order of reservoirs storage and supply in power generation operation. Both are suitable for cascaded reservoirs. Equilibrium with utility theory, which is based on firm equilibrium theory in microeconomics, has a solid theoretical foundation and is suitable for parallel reservoirs with relatively independent hydraulic relations. Aggregation-decomposition method involves two forms: reservoirs’ joint operation chart and large-scale system decomposition and coordination, which can be used in combination with cascaded and parallel structural analysis methods and is suitable for large-scale hybrid structural reservoir group. Hydraulic connection method describes the relationship pairwise in reservoir group by adopting matrix and is not limited by the structure of reservoir group, thus is applicable to any structural reservoir group. Structural analysis method is critical to optimize and efficiently solve reservoirs optimal operation problem, but it also needs to cooperate with other links.We suggested that further research should be carried out on the utilization of runoff forecast information, the coupling of statistical model with physical background and the refined operation of reservoir group of hybrid structures.
  • LUO Hui-ping, CAO Hui-qun, LUO Ping-an
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 22-27. https://doi.org/10.11988/ckyyb.20191173
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The aim of this study is to evaluate the eco-hydrological effect of water diversion and dispatching with Dongsha Lake of the Donghu Lakes Network as a typical research object. We selected five key eco-hydrological elements, namely, maximum flow velocity, average flow velocity, water surface ratio of flow velocity exceeding 0.01 m/s, water age, and water exchange rate from the perspective of controlling water eutrophication. By constructing the Dongsha Lake hydrodynamic model, we simulated the spatial distribution of flow velocity and water age under six conditions before and after the diversion and dispatching, and obtained the values of key eco-hydrological elements. Results unveiled that the maximum flow velocity, average flow velocity, water surface ratio of flow velocity exceeding 0.01 m/s and water exchange rate increased remarkably, while water age reduced markedly. Diversion and dispatching effectively affected the eco-hydrological conditions of the Dongsha Lake. The research finding offers a reference for ecological dispatching.
  • MIN Min, CHAI Yuan-bing, CHEN Xin-fo, XI Wen-bin, LU Dan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 28-33. https://doi.org/10.11988/ckyyb.20191167
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to study the relationship between phytoplankton community structure and water environment factors in the source region of the Yangtze River, we carried out surveys in the source region of the Yangtze River in May, August, September in the year 2017 and May, July and September in the year 2018. Besides, we conducted Pearson correlation analysis and Canonical ranking analysis between phytoplankton and water environmental factors. Results unveiled a total of 6 phyla 79 species of phytoplankton, mainly belongs to Bacillariophyta and Cyanophyta. The average density of phytoplankton at each sampling point was 71.66×104 ind./L. Canonical analysis indicated that temperature, chemical oxygen demand, permanganate index, ammonia nitrogen, total nitrogen and dissolved oxygen were major factors affecting the phytoplankton community structure in the source region of the Yangtze River.
  • WANG Yan, WANG Yi-min, ZHOU Shuai
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 34-39. https://doi.org/10.11988/ckyyb.20191129
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In the process of hydrological model calibration, different objective functions focus on different aspects of runoff simulation. In this paper, the HyMod model is applied to the source region of the Yellow River to explore the uncertainty of choosing objective functions and the influence of such uncertainty on runoff simulation. The Nash efficiency function fNS, the total error of water balance function ft, the low water error function fd and high error function fg are selected as objective functions. The optimal parameter sets corresponding to different objective functions are calibrated by using the genetic algorithm (GA), and are put into hydrological model in turn to simulate the hydrological processes. By comparing the yearly scale and monthly scale measured and simulated runoff processes as well as evaluation indicators such as Nash-Sutcliffe efficiency coefficient(NSE), cofficient of determination(R2) and Root Mean Square Error(RMSE), the impact of uncertainty of objective function on water resource evolution in yearly scale can be obtained. Results demonstrate that the impact of uncertainty on evaluation indicators differs remarkably when HyMod model is applied to the hydrological simulation in the source area of Yellow River in calibration and validation periods. For example, under fNS objective function, the value of NSE is the largest, followed by fg and fd in sequence. In addition, the accuracy of calibration period is superior to that of verification period. Similarly, the impact of uncertainty differs in various characteristic periods. For example, under fNS and ft objective functions, the simulated flow values in non-flood season are respectively overestimated and underestimated. The research findings offer theoretical reference for the selection of objective functions in calibrating hydrological model parameters.
  • ZENG Ke, TAN Xue-zhi, LIANG Liao-feng, LIU Ru, LIU Zu-fa, GAO Yi-jie
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 40-46. https://doi.org/10.11988/ckyyb.20191119
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the impacts of climate change on the occurrence frequency of flood characteristics in Bejiang River basin, the outputs of two scenarios (RCP4.5 and RCP8.5) based on BCC_CSM1.1 are statistically downscaled by Quantile mapping (QM) and used as input of SWAT model to simulate streamflow during historical (1965-2010) and future (2030-2064, 2065-2099) periods. Univariate analysis and bivariate joint analysis based on Copula are used to analyze annual maximum flood peak flow (Q) and annual maximum seven-day flood volume (W). The results show that climate change has heavier impacts on Q and W with larger return period exceeding 50 years, except from the W of 2065—2099 under RCP8.5. Climate change under RCP4.5 has heavier impacts on Q and W than that under RCP8.5. The impact of climate change on the Q is greater than that on the W under two scenarios. The design floods of the bivariate joint analysis is safer than that of the univariate analysis. The study incorporates climate change and bivariate joint analysis, and of referential value for flood risk assessment and management under varying circumstances.
  • WATERSOIL CONSERVATION AND ECOCONSTRUCTION
  • CHEN Qi-wei, XIONG Kang-ning, LAN An-jun
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 47-52. https://doi.org/10.11988/ckyyb.20191065
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Research on the potential danger of soil erosion in karst area is weak at present. We interpreted the soil erosion intensity in Guizhou Province, a typical karst region, with land use, lithology, and base rock coverage as semantic factors by Geological Information System(GIS) according to Standards for classification and gradation of soil erosion and Techniques standard for comprehensive control of soil erosion and water loss in karst region. Furthermore, we assessed the potential danger of soil erosion in Guizhou by using the soil erosion potential danger index (SEPDI) based on the allowable soil loss value and the soil anti-erosion life. Results suggest that the area of soil and water loss in Guizhou has amounted to 47 831.73 km2, dominated by light erosion, with an erosion modulus of 341 t / (km2·a) and a SEPDI of 2.52, indicating high level of potential danger. The SEPDI of 25.3% of villages in Guizhou ranges between 2 and 3, among which Liupanshui, Qianxinan, and Bijie feature the highest risk.We recommend that prevention work should be incorporated into SEPDI rather than merely soil erosion degree, and special attention needs to be given to areas with high SEPDI but weak soil erosion levels.
  • ZHANG Qiao-yan, TANG Li-xia, PAN Lu, HUANG Tong-li, CHEN Long
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 53-58. https://doi.org/10.11988/ckyyb.20190480
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The mechanical properties(tensile and shear properties) of roots are pivotal factors affecting the soil and water conservation. The roots of Indigofera amblyantha Craib and Cassia bicapsularis Linn were selected to research the mechanics of slope protection in Karst area. The relationship between the roots’ tensile strength and the shear characteristics of soil-root composite was investigated through indoor tensile test on single root and direct shear test on soil-root composite. The applicability of model WU in Karst area was also analyzed. Results indicated that tensile strength declined overall with the increasing of root diameter; however, such trend differs corresponding to different plant types. The shear characteristic of soil-root composite was jointly affected by tensile strength and friction between soil and roots, of which the former had larger influence; the shear characteristic with thin root and thick root together was better. Modified model WU is applicable to Karst area; but the modification coefficient varies corresponding to different plants. The research findings would lay a good foundation for the ecological restoration and selection and allocation of tree species in Karst area.
  • FLOOD PREVENTION AND DISASTER REDUCTION
  • LIU Bang-xiao, ZHU Xing-hua, GUO Jian, JIANG Cheng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 59-66. https://doi.org/10.11988/ckyyb.20190999
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Flume experiment with varied bed slope gradients (7°, 8°, 9°, 10°, 11°, 12°, 13°) was conducted to explore the downcutting erosion of landslide dam breach. Test results demonstrated that despite different slope gradients, the downcutting erosion of landslide dam breach under overtopping failure mode can be divided into three stages: breach penetration stage, accelerated erosion stage, and decelerated erosion stage. The slope gradient of trench bed affects the accelerated erosion stage. When the bed slope gradient is greater than or equal to 9°, the dominance of downcutting erosion supplemented by retrogressive erosion is weakened. Moreover, the duration of breaching is in a non-monotonic relation with slope gradient, shortens at first but then elongates along with the expansion of slope gradient. Average downcutting erosion rate and retrogressive erosion rate are also in non-monotonic relation with slope gradient, rises at first but then declines with the increase of slope gradient. When the slope gradient is smaller than 11°, the sensitivity of duration to slope gradient is higher than that to reservoir capacity in front of the dam; and vice versa.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • HU Xiao-hong, DENG Yue-sheng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 67-71. https://doi.org/10.11988/ckyyb.20201037
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    As a combination of levee and road, levee roads are featured with such special geographical location and changeable environmental factors as adjacent to the river on one side, and municipal buildings, flood control facilities, farmland, woodland and natural resource land on the other side. Research on levee road reconstruction technology, despite of its complexity, is of great practical significance for solving people’s livelihood issues such as flood protection and traffic. As road and levee belong to different disciplines, levee road are interdisciplinary, and there is currently little research on the technical requirements for levee road reconstruction. In line with the principle of strictly implementing flood protection standard, ensuring the safety of flooding, and exerting no effect on the original functions of levee, we designed four schemes of road reconstruction technology involving two working conditions (road at the top of the levee and at the foot), and two road-widening directions (toward the back of the river and toward the riverside). We examined the roadbed height, the reconstruction technology to control uneven settlement, and the structure combined with pressure immersion platform. We also proposed the concept of all-element design. Having been successfully applied to the Jiangbei expressway and the right bank avenue along the Yangtze River, the research achievements could be taken as reference for the design and reconstruction of similar levee roads.
  • HYDRAULICS
  • YANG Qing-hua, YAO Yuan, YANG Qian, ZHAO Zi-cheng, LIN Hong, MOU Yi, YAO Jin-tao
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 72-80. https://doi.org/10.11988/ckyyb.20191127
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Baffle-drop shaft is an effective energy dissipation structure in urban deep tunnel drainage system. Different structural parameters of the shaft result in large differences in flow capacity and energy dissipation rate. Through experimental study and numerical simulation (using realizable k-ε turbulence model and volume of fluid(VOF) method), the flow pattern, the maximum flow capacity, the outlet flow velocity and the energy dissipation rate of the shaft with different baffle spacings and baffle angles are analyzed. Results demonstrate that the basic flow patterns in the baffle-drop shaft can be summarized into three categories: wall-limited flow, critical flow, and free-fall flow. Increasing the baffle angle is conducive to the transition of flow pattern from wall-limited flow to free-fall flow. Therefore, a proper baffle angle is critical to the design of the shaft. The maximum discharge of the shaft increases as the baffle spacing and baffle angle increase. The energy dissipation rate of the shaft declines with the increase of inflow. Considering both maximum flow capacity and energy dissipation, the shaft performs the best when shaft diameter is 10 m with a baffle spacing of 4.85 m and baffle angles from 9° to 11°. The research finding offers technical support for the design of deep tunnel drainage systems.
  • ROCKSOIL ENGINEERING
  • YAO Zhao-ming, ZHANG Wen, GUO Meng-yuan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 81-85. https://doi.org/10.11988/ckyyb.20190988
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Safety evaluation of artificial freezing method depends on the creep characteristics of frozen soil. Uniaxial compression test and staged loading creep test were conducted at temperatures below 0 ℃ on undisturbed clay collected from a deep mine in Shanxi Province to study the failure mode and mechanism of the frozen soil as well as the form of uniaxial compressive strength and creep curves at different temperatures. The uniaxial compressive strength varied linearly with the declining of temperature, and the creep value under the same loading stress also decreased with the drop of temperature. In line with the internal variable theory, strain was considered as the internal state variable to describe the creep characteristics of frozen soil. The fitting curve of logarithm of creep and creep rate suggested a linear relationship between them. On such basis, an internal variable creep model that was only related to temperature and loading coefficient was established. Parameters of the model could be determined by fitting curves. The fitting of test data into the model showed that the model could better reflect the creep of frozen clay with less model parameters, and is convenient for engineering application.
  • KONG Xiang-hui, YAN Zhen-qiang, RONG Shu, ZHANG Jin-gang
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 86-91. https://doi.org/10.11988/ckyyb.20191046
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A new type of backfill material with self-leveling and self-compacting properties was prepared with excavated silt, cement and water as raw materials to effectively solve the problem of insufficient compaction of traditional fillers in backfilling projects. The red mud produced by the alumina industry was incorporated into the backfill material to replace part of the cement, with the purpose of improving the utilization of industrial waste and further reducing construction cost. With flowability as the control index in mix proportion design, the mixture with a water-solid ratio of 0.43 could meet the flowability requirement (200-300 mm). Furthermore, the flowability, bleeding and compressive strength of the mixture were examined respectively via indoor test. Results demonstrated that the increase of red mud could reduce the flowability and bleeding rate of the mixture, and meanwhile accelerate the bleeding. The partial replacement of cement by red mud does not affect the growth rate of the mixture’s strength. The strength of the mixture increases when red mud content is in the range of 10%-15%, while declines when red mud content is smaller than 10% or greater than 15%. Red mud has a good application prospect in terms of bleeding stability and strength for flowable silt backfill materials.
  • CHEN Ling-wei, LI Cong-an, LIU Wei, PENG Wei-ping, ZHANG Qing-hua
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 92-97. https://doi.org/10.11988/ckyyb.20190937
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Three groups of centrifugal model tests were carried out on a high and steep reinforced slope formed by cutting mountain and filling valley. Numerical models which simulate the loading process of centrifugal tests were established based on the centrifugal model tests. The deformation, stress-strain distribution of reinforcement and failure modes of reinforced slope were studied under different foundation strengths. The results of numerical simulation and centrifugal test were compared and analyzed for further research on the distribution of reinforcement. Results revealed that lateral extrusion of the lower slope was observed in the presence of increasing overlying load, which led to the yield of the bottom reinforcement beneath the upper part of slope when the strength of the lower filler was insufficient. Potential sliding surface was formed from the foot of the inner slope to H/3. The internal force of reinforcement changed abruptly at the platform, and the position of maximum axial force of reinforcement moved downwards with the increase of slope height. The stability of the slope can be improved by increasing the length of geosynthetics in the lower slope appropriately. The stress distribution of reinforcement can be optimized by densifying the geosynthetics in the H/3 range of reinforced slopes at all levels. The numerical analysis results provide a theoretical basis for optimizing the design of reinforced slopes.
  • ZONG Qiu-lei, WANG Bin, WANG Kai, ZHANG Min-jia, ZHANG Jia-ming, WANG Cong
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 98-104. https://doi.org/10.11988/ckyyb.20190917
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The process of shield tunnel construction for metro is very complicated involving many potential risks. If not properly controlled, the construction will pose severe threats to public safety. In an attempt to effectively control the risks of shield tunnel construction, a risk assessment method based on trapezoidal fuzzy number and C-OWA operator is proposed. The evaluation information of experts is represented by trapezoidal fuzzy numbers, and the operational rule of fuzzy number is adopted to calculate the risk level of each potential risk factor. The risk level of evaluation indicators at all hierarchies, combined with the weight of each risk index calculated by C-OWA operator weighting method, is determined by calculating down-top of the evaluation system. The risk rating is obtained according to the risk matrix. The proposed method was applied to evaluate the construction risks of a shield tunnel construction of Shenzhen Metro Line 12, and the potential risk factors that require risk prevention measures in the project are obtained. The example shows that the proposed method is reasonable and reliable. Compared with traditional risk assessment methods, it has more advantages in dealing with complex problems involving fuzzy definition and subjectiveness.
  • SHI Lei, WU Yong,GUO Jian-feng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 105-111. https://doi.org/10.11988/ckyyb.20191152
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The aim of this study is to probe into the influence of ground load on the surrounding rock stress of shallow-buried tunnel with lining support. On the basis of Verruijt’s research on surrounding rock stress of shallow tunnel under complex boundary conditions, the analytical solution to surrounding rock stress under the combined action of lining support and ground surface load were obtained, and the influences of multiple factors on the stress field were examined. Results demonstrated that greater surface load resulted in larger circumferential stress at tunnel waist and smaller circumferential stress at tunnel bottom; larger internal pressure led to smaller circumferential stress at tunnel waist and greater circumferential stress at tunnel bottom. Ground load and lining support will not change the distribution law of circumferential stress around the shallow tunnel and its most unfavorable position, but will change its magnitude and direction. In the process of excavation, the soil is prone to suffer from instability and damage at the haunch of the tunnel.
  • DONG Hui, PENG Bo-cheng, ZOU Chang-yu, GAO Qian-feng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 112-118. https://doi.org/10.11988/ckyyb.20191008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Shallow quaternary deposited and sedimentary soil-rock mixtures (SRMs) are widely distributed on the earth. One of the most effective approaches to solve the increasingly complex geotechnical problems is to study the mechanical properties of SRMs from their structural characteristics. At present, the quantification of the structure of SRMs is mainly and indirectly described by macroscopic indicators, such as density, stone content, and void ratio; while the multiscale correlation between microscopic and mesoscopic structural indexes is still a technical bottleneck. To better understand the influence of the structure on the mechanical behavior of SRMs, the layered distribution form of rock blocks created in the deposited and sedimentary evolution was quantified via the standard variance based on the idea of comprehensive structural potential. The structural parameter (ms) was defined as the ratio of the deviator stress of uniform SRMs to that of non-uniform SRMs. The variations of ms with the axial strain (ε1), the non-uniformity (s) and the confining pressure (σ3c) were examined, and the quantitative expression of ms was obtained and incorporated into an elastic-plastic constitutive model with double yield surfaces. The results show that the variation of ms well reflects the influence of the layered structural characteristics on the mechanical behavior of SRMs. The comprehensive structural potential of SRMs is released almost completely as the axial strain reaches 5%, and the feature value (i.e., ms (5%)) reflects the macroscopic influence of structural characteristics on the mechanical behavior of SRMs. Meanwhile, the modified constitutive model with ms improves the accuracy of the deviator stress by about 28%. It proves that the modified constitutive model can reasonably reflect the macroscopic mechanical properties of layered SRMs.
  • XIAO Kai-qian,WANG Shuai, ZHANG Ming, ZHENG Hong-wei, LIANG Guan-ting
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 119-125. https://doi.org/10.11988/ckyyb.20191068
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The Xiangxi Highway Bridge in the Three Gorges Reservoir Area is faced with prominent engineering geological problems as f1 and f2 faults and multiple free faces developed in the high bedding slope. On the basis of survey data and field investigation, we analyzed the geological background, and finely evaluated the parameters of dominant structural planes of the slope via site mechanical test. Moreover, we calculated the safety factor of the slope in different structural planes in different layers and slip surfaces with different lengths via the Sarma method. We further established the relations of support force and average thickness of sliding body against safety factor. Results demonstrated that for bedding slope with structural plane penetrating through to ground surface, the safety factor of sliding body on the structural plane is in a negative correlation with the average thickness of the sliding body, and in a weak correlation with the length of the sliding surface. The slope body can be divided into three sections according to the terrain: the locking section at slope foot, the main sliding section, and the pulling section at slope top. The sliding body on the f1 fault has insufficient safety reserve because of large thickness of rock layer and low strength of the sliding surface: the shear-off peak friction angle is 27.0°, the cohesive force is 0.07 MPa, the residual friction angle is 25.2°, and the residual cohesion is 0.05 MPa. An additional support force of 4 283 kN/m or unloading 32.6% of the slope volume is needed to meet the lower limit of stability standard. Due to huge work quantity, we recommend anti-slide pile design in combination with engineering excavation.
  • ZHANG Zhi-fei, TANG Wei-min, JIA Hong-biao
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 126-132. https://doi.org/10.11988/ckyyb.20191101
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The crack propagation process and failure mode of discontinuous jointed rock mass with different roughness coefficients under different normal stresses are studied via particle flow method, and the stress evolution process of pre-shearing plane is discussed. Results reveal that the failure modes of rock bridge can be roughly divided into five categories according to the tensile and shear properties of micro-cracks and their evolution process, which are closely related to the normal stress and joint surface roughness coefficients. The increments in normal stress and joint surface roughness coefficients would instigate rock bridge towards shear failure. The angle between the initial wing crack and the original joint surface is not sensitive to the change of normal stress; but declines with the increase of joint roughness coefficients. In the shearing process, the stress on the pre-shearing plane does not distribute uniformly and meanwhile redistributes continuously. The shear stress of flat jointed rock mass is mainly borne by rock bridge, and the compressive stress of the rock bridge is greater than that of the joint in both horizontal and normal directions, while for rough jointed rock mass, the shear stress is borne by both the joint and the rock bridge, and the stress of the joint part is higher than that of the rock bridge.
  • LI Gui-jiang, QU Yao, LU Guo-sheng, LIU Jun-shuai
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 133-138. https://doi.org/10.11988/ckyyb.20191052
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A model for calculating surrounding rock pressure of tunnel with small clear distance under complex unsymmetrical loading is established. The theoretical formulas of surrounding rock pressure are deduced based on roadway tunnel design specifications to investigate the influence of clear distance and ground sloping on surrounding rock pressure of tunnel. The rationality of the theoretical calculation formulas are verified by numerical simulation. The influences of varying clear distance and ground sloping on the surrounding rock pressure of vault, arch waist and arch foot of the first tunnel and the subsequently excavated tunnel are analyzed. Results reveal that when two tunnels are excavated successively, the change of clear distance and ground surface sloping has great influence on the surrounding rock pressure inside the tunnel. The pressure of surrounding rock inside the first-excavated tunnel is positively correlated with clear distance and sloping, while the inner surrounding rock pressure of the subsequently excavated tunnel is negatively correlated with clear distance and sloping.
  • YANG Zhou-jie, ZHOU Jia-zuo, CHEN Qiang, WAN Yi-zhao, WEI Chang-fu, MENG Xiang-chuan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 139-145. https://doi.org/10.11988/ckyyb.20190935
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Triaxial shear tests were conducted on self-prepared hydrate-bearing sediments to obtain the influences of effective confining pressure and saturation on the strength and rigidness of hydrate-bearing sediments. The test specimens were made from artificial clayey fine sand in reference to the particle size distribution of sediment in the north part of South China Sea. CO2 hydrate-bearing sediments with different saturations were prepared by a self-developed triaxial test machine, and the triaxial shear tests were carried out under the effective confining pressure of 1 MPa, 2 MPa, and 4 MPa. As confining pressure changes automatically with gas pressure, the effective confining pressure remained unchanged during the formation of hydrate when gas was consumed. The experimental results reveal that the initial elastic modulus increased with the rising of hydrate saturation, while independent of the effective confining pressure. The initial Poisson ratio decreased with the increase of effective confining pressure while grew with the rising of hydrate saturation. The strength index cohesive force increased with the increase of hydrate saturation, while the internal friction angle was independent of hydrate saturation. In addition, the nonlinear elastic constitutive model for hydrate-bearing sediment was established by introducing a parameter hydrate saturation based on Duncan-Chang’s model, and the proposed model was validated by test data.
  • ZHANG Ting, TAN Fan, YANG Zhe
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 146-151. https://doi.org/10.11988/ckyyb.20190970
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The dynamic modulus damping ratio of the tailings silt damming material of a tailings dam was tested using the GDS dynamic triaxial apparatus. The dynamic stress-strain characteristics of tailings silt were examined, and the effect of confining pressure and consolidation ratio on the maximum dynamic shear modulus as well as dynamic shear modulus ratio and damping ratio were analyzed. Moreover, the modified formulae for the maximum dynamic shear model and modulus attenuation which could normalize the influence of consolidation ratio was proposed based on Zhujiang Shen’s dynamic constitutive model. Test results demonstrated that with the rising of confining pressure and consolidation ratio, the dynamic elastic modulus of tailings silt increased while damping ratio decreased. With the augment of dynamic strain, the dynamic shear modulus ratio reduced while damping ratio increased. The modified formulae could normalize the effects of consolidation ratio and confining pressure on the maximum dynamic shear modulus and modulus attenuation, and thus accurately reflecting the dynamic deformation characteristics of tailings silt.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • WANG Dong-li, YANG Ce, ZHAO Qing-xin, LI Tong, YANG Fang-fang, ZHOU Mi
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 152-156. https://doi.org/10.11988/ckyyb.20191440
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The aim of this study is to investigate the frost resistance of pervious concrete added with different seashell wastes in northern coastal areas of China. The seashells from Qinhuangdao were selected to prepare pervious vegetation-growing concrete. The freeze-thaw durability of pervious concretes made from kitchen oyster waste, factory oyster waste, kitchen scallop waste and factory scallop waste were examined by slow freezing method with mass loss rate and strength as evaluation indexes in association with Scanning Electron Microscoke(SEM), Backscattered Electron Imaging(BSE) and other microscopic tests. Results revealed that (1)factory shell waste is of better freeze-thaw resistance and strength than kitchen shell waste. The incorporation of silica fume reduced the salinity while improving the compressive strength of shell pervious concrete, and enhancing the freeze-thaw resistance to a limited extent. Through microscopic analysis and multi-factor comparison, the content of silica fume is determined at 5% as the optimal. (2)Pervious concrete containing scallop waste boasts higher freeze-thaw durability than that containing oyster waste owning to its dense microscopic surface structure.
  • WEI Tao, CHEN Guo-qing, XU Peng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 157-164. https://doi.org/10.11988/ckyyb.20190936
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To tackle the problems of strength loss and poor durability of concrete in high geothermal tunnel, we examined the mechanical properties of composite concretes undergone thermal curing mixed with steel fiber, polypropylene fiber and vitrified microspheres, hence revealing the variation of compressive strength, tensile strength and failure characteristics of composite concretes with curing temperature. Furthermore, we deduced the formula of uniaxial compression strength of composite concretes considering the thermal-force relationship based on the homogenization theory. Results unveiled that the composite concretes are of higher compressive strength and tensile strength compared with ordinary concrete with no such mixtures, and have smaller strength loss after thermal curing. Failed sample is cracked but not separated, implying higher residual strength. The inclusion materials in the composite concretes attribute to the strength and durability after high temperature curing. The concrete strength model based on the homogenization theory fits well with the experimental results. The research findings offer theoretical basis for the design and evaluation of lining structures in high geothermal tunnel.
  • ZHANG Jun-wen, ZHANG Zhi-xin, NI Yuan-zhen
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 165-168. https://doi.org/10.11988/ckyyb.20200530
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The causes of the upper diagonal cracks at the downstream side of the main dam pier of Lushui Hydropower Complex are analyzed using finite element method with ABAQUS. By establishing a 3D model of the downstream side of the main dam 5# pier, including the spillway surface, the pier and the foundation of hoist bents on the pier, the thermal stress was analyzed using ABAQUS. The action of solar temperature is a major cause of the cracks. In addition, a crack treatment scheme for the pier was developed, and emergency measures such as prestressed anchoring, planting reinforcement, and chemical grouting were adopted to effectively control the cracks. The research offers a reference for the treatment of similar engineering defects.
  • INFORMATION TECHNOLOGY APPLICATION
  • YAN Jiang-ping, ZHAI Hai-feng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 169-175. https://doi.org/10.11988/ckyyb.20200731
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In the aim of improving project management efficiency, controlling project quality, and reducing the impact of human factors on project quality, the construction information, concrete temperature, concrete vibrating, and grouting in the construction process are intelligently monitored and controlled via information technology, digitalization, automatic control and other technologies. In view of this, an intelligent management system for construction quality under the intelligent construction environment for Yangfanggou Hydropower Station is developed based on the quality management modules of the BIM management system as well as the intelligent temperature control, intelligent vibrating, intelligent grouting, and whole-process image acquisition system integrated by the BIM management system. The construction quality information is managed dynamically through real-time collection, real-time analysis, and decision feedback. The problems in construction quality control, information collection, analysis, and decision-making in the EPC and traditional construction mode have been solved. The present intelligent system has improved management efficiency and management quality, and achieved better management results.
  • CHEN Liang-xiong, YANG Jing-xue, LI Xing-han, LI Wei-tian, CHEN Yu-fei, GAO Yi-shan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(12): 176-182. https://doi.org/10.11988/ckyyb.20191088
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    It is a very inevitable choice to improve the efficiency and level of reservoir water administration supervision with the help of modern information technology under the current situation. A complete reservoir water administration and supervision system for Hedi reservoir is developed by integrating unmanned aerial vehicle survey, map cache, remote sensing inversion of water quality and “Internet+” technology. The supervision platform achieved the goal of air-space-ground integration for reservoir water resource, giving support for reservoir management and water law enforcement, maintaining ecological balance in reservoir area, and ensuring the water safety of production and living. Practical application of the system demonstrates that the supervision platform which is based on the integration of massive, multi-source and heterogeneous data, can effectively, dynamically and comprehensively grasp and monitor different water-related behaviors, water quality safety conditions and reservoir operation status within the reservoir area. This platform can also promote the reservoir management and water law enforcement to be more scientific, accurate, timely and efficient.