01 April 2022, Volume 39 Issue 4

    

• Select all
  |

• Select
  Cover and Table of Contents

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 0-0.

  Abstract ( ) Download PDF ( )   Knowledge map   Save
SPECIAL CONTRIBUTION
• Select
  Identification and Physical Mechanical Property Comparison between Completely Decomposed Granite and Granite Residual Soil

  ZHOU Xiao-wen, LUO Xing-cai

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 1-7. https://doi.org/10.11988/ckyyb.20211331

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Completely decomposed granite (CDG) and granite residual soil (GRS) are prone to trigger engineering accidents and geological disasters in South China. Despite that the weathering degree and engineering properties of CDG and GRS both vary remarkably, it is still a challenging task to distinguish CDG and GRS in practical geological investigation, in which the field geological appearance and the measured hit number of standard penetration test according to existing specification are taken as the major indicators for identification. In this paper, we discussed the relevant clauses about identifying CDG and GRS in some current specifications. In view of the difference in gradation between of CDG and GRS, i.e., the former is usually clayey sand, while the latter sand clay, we suggest to take grading characteristic as the subsidiary index of identifying CDG and GRS.According to physical properties test and triaxial shear test of soil samples from a foundation pit, we found that GRS sample had a larger pore ratio with a poor gradation lack of some intermediate particle sizes. Both the undisturbed CDG and GRS present initial structural features reflected by shear zone with strain localization in shear deformation, displaying drum-shear zone failure mode; the remolded samples present a standard drum-like failure mode. The friction angle of drainage shear of undisturbed CDG is slightly higher than that of GRS, and the cohesion obviously higher as CDG boasts a stronger structure; the cohesion of remolded CDG and remolded GRS are close due to the lack of original structure. Under low confining pressure, the structural strength of undisturbed soils contribute up to 60%-70% of the total shear strength, and the compression action of high confining pressure can completely destroy the initial structure of soils, in which case the structural strength will be eliminated.
RIVER LAKE PROTECTION AND REGULATION
• Select
  Research Status and Progress of Cohesive Sediment Flocculation

  LI Jie, YANG Wen-jun, JING Si-yu, CHEN Yue

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 8-13. https://doi.org/10.11988/ckyyb.20201353

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Study on the flocculation mechanism of cohesive sediment is of great significance to the treatment of deposition in estuaries, reservoirs and waterways and water environment protection. In this paper, we made a review on the equipment and methods used in numerical simulation, field observation and laboratory experiment of cohesive sediment flocculation, and also expounded the research achievements of sediment flocculation under the influences of turbulent shear rate, salinity, suspended sediment concentration and organic matters. Researches in the following fields are still inadequate: three-dimensional observation of floc structure, in-situ observation of flocculation in high-concentration water, sediment flocculation influenced by multi-factor, and the quantitative relation between flow turbulence structure and flocculation characteristics. Researches need to be strengthened in the following aspects: developing flocculation observation device; quantifying the corresponding relation between flow turbulence structure and flocculation characteristics; multi-factor coupling experiment; and three-dimensional structure observation of floc.
• Select
  Hydrodynamic Adjustment of the East Branch of Ouchi River under Different Incoming Discharge Conditions

  LIU Heng, LI Zhi-wei, CHEN Bang, HU Xu-yue

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 14-20. https://doi.org/10.11988/ckyyb.20201235

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Since the 1950s, the flow diversion ratio of Ouchi River in the Jingjiang reach of middle Yangtze River has decreased yearly and even experienced long-time zero-flow in recent years with the successive construction of water conservancy projects such as the cutoffs of lower Jingjiang River, the Gezhouba Dam, and the Three Gorges Reservoir. To understand the impact of flow discharge changes in flood season on the hydrodynamics along the reach, a 2D mathematical model using MIKE 21 was established based on the measured topographic data and hydrological data in the purpose of providing reference for the practice of river regulation, dredging and river network connection engineering in the Ouchi River. Under medium and low incoming discharge, the maximum flow velocity of the river channel appeared in the Meitian Lake reach. Under medium and high incoming discharge, due to the increase in the diversion capacity of the middle branch of Ouchi River, the flow velocity in downstream Huangjinzha reduced significantly, and the minimum flow velocity concentrated in the Huangjinzha-Yinjiazhou reach. Affected by the backward slope, the hydrodynamic axis of the Yinjiazhou segment gradually shifted to the right bank, and the maximum velocity was observed at the entrance of Meitian Lake, close to the channel on the left bank. Flow diversion in the right branch was mainly controlled by incoming discharge stage and cross section area.
WATER RESOURCES
• Select
  Interfacial Hydrological Process of Heat Tracing: Research Progresses and Development Trends

  DONG Lin-yao, TANG Wen-jian, CHEN Jian-yao, HE Min

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 21-26. https://doi.org/10.11988/ckyyb.20201267

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  As an important link among regional resources, ecology and environment protection, interfacial hydrological process involves material circulation and energy exchange among different circles. Heat tracing of interfacial hydrological process is the focus and difficulty in future research due to the complex and widely-affected energy exchange process, notwithstanding its effectiveness in tracing hydrological process due to its low cost, easy operation and no pollution. In the present research, we made a review on the water and heat transport mechanism, heat tracing techniques, and typical heat tracing applications in the hydrological processes of rainfall-soil-groundwater, surface water-groundwater, as well as groundwater-sea water interfaces, and present the development trends in future: 1) scale effect in the interfacial hydrological process of heat tracing should be considered;2) multiple approaches are required to verify the uncertain heat tracing results; 3) novel temperature monitoring technique to monitoring large-scale and long-term interfacial energy change could be an effective means to improve the accuracy of results; 4) multi-dimensional water and heat transfer model suitable for different scales and types is the key direction of future research.
• Select
  Abrupt Changes and Their Causes of Runoff at Main Control Stations Upstream of Zhengyangguan of Huaihe River

  SU Cui, HU You-bing, FENG Zhi-gang, LI Wen-jie, WANG Jing-teng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 27-33. https://doi.org/10.11988/ckyyb.20201332

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The trends and abrupt changes of runoff at major control stations in the upstream of Zhengyangguan were investigated by using Mann-Kendall trend analysis method,Mann-Kendall abrupt change test method,and moving-t test method based on monthly measured runoff data and the monthly precipitation data since the 1950s. Factors affecting the abrupt change of runoff were also analyzed. Results demonstrated that the runoff of main control stations upstream of Zhengyangguan has been on a downward trend since the 1950s, and that of the tributary control stations more obvious. In the late 1950s, the Jiangjiaji station and Hengpaitou station in the southern tributary of Huaihe River witnessed abrupt changes in runoff because the reservoirs in the upstream of control station was built and put into operation, which led to the abrupt reduction of runoff. The annual runoff of Fuyangzha station in Huaibei tributary declined abruptly in 1971 possibly because of both the small precipitation in the 1970s and the regulation effect of sluice and dam. During the abrupt changes, the runoff of Jiangjiaji station, Hengpaitou station and Fuyangzha station affected by human activities were 116.0 billion,104.3 billion,130.3 billion m³ respectively, and the runoff reduction rates were 49.5%, 61.8% and 42.3%, respectively.The research results can provide technical support for flood and drought disaster prevention and water resources management for the Huaihe River Basin.
• Select
  Application of Fuzzy Analytic Hierarchy Process to Water Resource Value Assessment: Case Study of Mianyang City

  GONG Jie, ZHAO Qi-chao, LOU Hua-chao, LI Qiao-ling

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 34-40. https://doi.org/10.11988/ckyyb.20201205

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Water resources play an irreplaceable role in maintaining ecological environment as well as economic and social development. Quantified research and assessment on the value of water resources, on one hand, offers theoretical support for governments in formulating policies, and on the other, promotes the stable and healthy development of regional social economy. The water resources value in Mianyang City was assessed comprehensively as a case study based on fuzzy analytic hierarchy process (FAHP). An index system involving 14 indicators covering water quality, water quantity, social economy, population, and ecological environment was constructed; weights of the indicators were calculated using both subjective and objective weighting methods. Among criterion layer factors that affect the water resources value in Mianyang, water quantity boasts the largest weight, followed by ecological environment, social economy, population, and water quality in sequence; among index layer factors, total water supply has the largest weight, followed by water resources per capita and reuse rate of industrial water in sequence. The fuzzy comprehensive index of water resource value in Mianyang is 2.37, implying that the water resources value in Mianyang ranks above middle. The price of water resources assets had been on the rise in general from 2014 to 2018, reaching 4.97 yuan/m³, which is 2.6 times the current water price for residents (1.91 yuan/m³). And water cost occupies 0.74% of residents’ income, far below the affordable water cost index, which is 1.19%, accounting for the rationality of raising the price of water resources properly. Nevertheless, the overall water resources value in Mianyang had shown a downward trend year by year during 2014-2018, mainly due to the decrease of water resources amount surpassing the growth of unit water resources value. Government should pay attention to the causes of water resources decline, and put forward future control measures to maintain the sustainable development of local water resources.
• Select
  Rainfall-Runoff Relation in Balegen River Basin Based on SWAT Model

  LI Kai, WANG Yong-qiang, XU Ji-jun, WU Zhi-jun, XU Xiang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 41-48. https://doi.org/10.11988/ckyyb.20201272

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Studying the relationship between rainfall and runoff in river basin provides a basis for reasonable water resources management and soil and water conservation. Based on measured rainfall data and historical measured runoff data in the Balegen River basin, SWAT model was constructed and was used to restore runoff series. The interannual variation characteristics and trend of rainfall-runoff relationship from 1970 to 2015 were examined using Kendall rank test, moving average, M-K test, wavelet analysis, cumulative anomaly method, and runoff coefficient analysis. Furthermore, the contribution rate of climate change and human activities to runoff changes were quantitatively separated by comparing the cumulative slope change rate. Results manifested that 1) SWAT model is feasible to restore the runoff in Balegen River basin, with the evaluation index R² reaching 0.78 and NSE 0.76 in calibration period, and R² 0.58 and NSE 0.51 in verification period. 2) From 1970 to 2015, rainfall in the Balegen River basin displayed a significant upward trend, while runoff trend was not significant; rainfall changed abruptly in 1981, and runoff in 1995 and 2010. The periodicity of rainfall and runoff series varied especially in the principal cycle; the principal cycle of rainfall is 28 years and runoff 23 years. 3) The rainfall-runoff relation changed abruptly in 1989 and 2001, after which the overall runoff coefficient declined, from 0.15 in 1970-1988 to 0.11 in 1989-2006, and 0.10 in 2007-2015. 4) With 1970-1988 as the base period, human activities dominated the runoff change from 1989 to 2001 with a contribution rate of 65%, and climate change contributed 35% to the runoff change; human activities also contributed 81% to runoff change from 2001 to 2015, and climate change contributed 19%. When 1989-2001 was determined as the base period, the contribution rate of human activities to runoff change from 2001 to 2015 was 51%, and the contribution rate of climate change was 49%.
WATER ENVIRONMENT AND WATER ECOLOGY
• Select
  Analyzing Spatio-temporal Characteristics of Water Quality in Jinyin Lake Using Water Quality Crucial Index (WQI_min)

  YANG Lie, YAN Xiao-ke, LIU Yan-li, ZHU Jing, WU Li, ZHANG Zu-lin

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 49-55. https://doi.org/10.11988/ckyyb.20201360

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The spatial and temporal changes of ten water quality indicators obtained monthly from August 2018 to October 2019 in seven water systems of Jinyin Lake in Wuhan were investigated by constructing a water quality crucial index model (WQI_min) consisting of four crucial indices, namely, five-day biochemical oxygen demand (BOD₅), permanganate index (PI), chemical oxygen demand (COD), and dissolved oxygen (DO) using principal component analysis. Result demonstrated that the water quality in Jinyin Lake differed notably in spatial scale: Dongyin Lake, Shangjin Lake, and Moshui Lake in the upstream of Jinyin Lake belonged to polluted area of inferior water quality with the WQI_min values ranging between 25.63 and 31.79; Dongda Lake, Xiajin Lake, Xiayin Lake and Shangyin Lake in the downsteam were low-polluted areas of medium level with their average WQI_min values ranging from 45.64 to 53.19. In temporal scale, water quality in Jinyin Lake can be divided according to three time periods: January 2019 witnessed the optimum water quality with an average WQI_min value amounting to 61.68; August 2018 to March 2019 (except for January 2019) undergone low pollution with the average WQI_min value from 47.17 to 52.70; April 2019 to October 2019 presented inferior water quality with the WQI_min value from 24.41 to 35.95. The water quality in August-September 2019 declined compared with the same period in 2018 because of the increasing discharge of xenobiotic and endogenous pollutants. In conclusion, the water management of Jinyin Lake needs to be further strengthened.
• Select
  Assessment of Water Quality in Tuojiang River Basin in Winter and Spring Alternate and Analysis on Differences

  SHUI Yong-hong, LU Yong-hong, LUO Jing, LUO Yong-jun, MAO Hong-mei, PENG Li-fan

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 56-62. https://doi.org/10.11988/ckyyb.20201328

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The aim of this research is to further investigate the effectiveness of comprehensive governance and policy implementation for the Tuojiang River. According to monitorings at sixteen state-control sections and one background reference point in February from 2016 to 2019 , the water quality of Tuojiang River Basin in Winter and Spring Alternate (WSA) was compared and analyzed by using WQI_min method. Seven parameters including pH value, dissolved oxygen (DO), total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH₃-N), permanganate index (COD_Mn) and electrical conductivity (EC) were selected for comparative analysis. The contribution rate of each parameter was also examined by using comprehensive water quality index method. Results revealed an ever-increasing water quality in the WSA from 2016 to 2019 in Tuojiang River Basin: sections of extremely inferior water quality were eliminated in 2019; total phosphorus pollution has been effectively controlled in the upstream. Nevertheless, total nitrogen pollution was prominent across the whole basin, and water pollution in the background sections has emerged. Controlling domestic sewage and agricultural non-point source pollution should be the focus of treatment of Tuojiang River Basin, especially the downstream.
WATER SOIL CONSERVATION AND ECOLOGICAL RESTORATION
• Select
  Land Use Change Prediction and Hydrological Response Assessment of Watershed Based on FLUS Model

  TANG Jia, HU Xi-jun, WEI Bao-jing, LUO Zi-wei, ZHAO Si-wen, WANG Ye-zi

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 63-69. https://doi.org/10.11988/ckyyb.20210182

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Simulating land use change under different future development scenarios and evaluating its impact on hydrology play an important role in guiding land use optimization and water security in the watershed. The trend of land use change in the Miluo River Basin from 2000 to 2018 was analyzed, and the land use in 2035 was predicted using FLUS model under two scenarios: the baseline scenario with no control area, and the restricted scenario with development restriction area. Moreover, the change of hydrological response caused by land use change in different scenarios was evaluated by SWAT model. Results showed that: 1) The six land use types in the Miluo River Basin showed obvious change trends from 2000 to 2018, among which the main trend was the transformation from woodland and cultivated land to construction land. 2) Compared with the baseline scenario, the restricted scenario saw increments in forestland and unused land by 0.14 km² and 0.04 km², and reduction in cultivated land and grassland by 0.13 km² and 0.06 km², respectively. The proportion of total area of various land use types remained unchanged. 3) The annual runoff of the basin under the restricted scenario is 383 500 m³ less than that under the baseline scenario.
• Select
  Vegetation Stability and Its Influencing Factors in Inner Mongolia

  TELIGEER, NARENMANDULA, GUO En-liang, ARUNA, KANGYAO, NARENFU

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 70-76. https://doi.org/10.11988/ckyyb.20210014

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  As a major component of ecosystem, vegetation plays a vital role in regulating global climate change and ecological balance. It is an indicator of climate change. The study of vegetation elasticity, vegetation resistance and their influencing factors is of great significance to regional vegetation stability and ecological sustainable development. Based on the MOD13A2 normalized difference vegetation index (NDVI) data, meteorological data and vegetation type data from 2000 to 2019, we discussed the vegetation stability and its influencing factors in Inner Mongolia through autoregressive model, trend analysis and geospatial analysis. Results illustrated that the NDVI of forest, meadow grassland and desert grassland in Inner Mongolia increased from 2000 to 2019, and vegetation coverage tended to improve as a whole. The fitting degree between vegetation elastic index and average NDVI of forest and meadow steppe is low, and the fitting degree between vegetation elastic index and NDVI of desert steppe is higher, which indicates that the vegetation elasticity of forest and meadow steppe is high, and that of desert steppe is low. Desert steppe is more resistant to precipitation and temperature, while forest and meadow steppe are less resistant to temperature. The results suggest that the elasticity of different types of vegetation in Inner Mongolia varies with climate factors, and precipitation is the major limiting factor of vegetation change in Inner Mongolia.
ENGINEERING SAFETY AND DISASTER PREVENTION
• Select
  Monitoring Slope Displacements of Muyubao Landslide Using InSAR Analysis Technique

  WANG Shang-xiao, LI Shi-yao, NIU Rui-qing

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 77-84. https://doi.org/10.11988/ckyyb.20201237

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The Three Gorges Reservoir area has been suffering from striking landslid disasters due to complex geological conditions and numerous slope problems, posing daily monitoring requirements. Conventional monitoring not only costs large amounts of manpower and material resources, and also is prone to be limited by external conditions. In the present research, 22 views of ALOS-2 satellite data from August 2016 to October 2017 of the Yangtze River bank in Badong County as the research area were processed using PS InSAR (permanent scatterer interferometry) technology to obtain accurate regional surface deformation results. In association with hydrology, geology and field investigation, the deformation characteristics such as sliding rate and scale of Muyubao landslide were analyzed. Results manifested that in the monitoring period, the Muyubao landslide was in a slow creep deformation stage, with an average deformation rate of 10.4 mm/a. Water level fluctuation was the major influential factor of landslide deformation.
• Select
  Gross Error Detection of Slope Safety Monitoring Data Based on SSA-DBSCAN

  JIANG Qi-jia, JIANG Zhong-ming, TANG Dong, ZENG Jing-ming

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 85-90. https://doi.org/10.11988/ckyyb.20210032

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  A method of detecting the gross error of slope monitoring data is presented based on singular spectrum analysis (SSA) and density-based spatial clustering of applications with noise (DBSCAN). The method integrates the advantages of SSA in signal extraction and DBSCAN in distinguishing gross errors and outliers. Firstly, SSA is used to decompose and reconstruct the monitoring series to accurately extract the main signal and obtain the residual components. Secondly, DBSCAN is employed to analyze the residual components. The two methods are combined to determine and eliminate the gross errors. Examples of slope monitoring series affected by multiple factors are introduced for verification. Moreover, the present method is compared with the median absolute deviation method (MAD) and Grubbs criterion method (Grubbs), and results suggest that the present SSA-DBSCAN method is of excellent performance and low misjudgment rate compared with the abovementioned methods.
HYDRAULICS
• Select
  Local Scour Characteristics of Step-shaped Spur Dike under Unsteady Flow

  ZHONG Liang, JIANG Li, JIANG Tong, LI Guo-ji, CHEN Jing-yuan

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 91-98. https://doi.org/10.11988/ckyyb.20201341

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The flow in natural river is mostly unsteady flow. Researching the local scour characteristics of step-shaped spur dike, a common waterway regulation structure, under the action of unsteady flow is of great significance to spur dike structure design and protection against flood damage. In the present research, the local scour characteristics of step-shaped spur dike under unsteady flow were discussed by establishing a 2-D mathematical model of flow and sediment. The natural inflow process was simplified as trough and peak inflow processes by using autoregressive Markov model. Research results demonstrated that the flow velocity in the main flow area and the recirculation area behind the spur dike changed with the upstream flow regardless of different discharge processes. The main flow area in trough inflow process gradually divided into two regions along with time, while in peak inflow process into two regions in the early stage. Influenced by the change of the main flow area and the siltation area behind the scour pit, the downstream boundary of the scour pit protruded towards the downstream and then retracted in trough inflow process, while in peak inflow process, the boundary of the scour pit shrank into the pit and then diffused to the downstream. The maximum scour depth at dam head can increase by 25.5%-54.3% compared with that in constant flow condition. L_d1, the length of the first-step spur dike, was used to characterize the scour pit scale; during the 6-hour scouring, the maximum length and width of the scour pit can reach 9.2L_d1 and 2L_d1 respectively in trough inflow process, and 11.3L_d1 and 2.1L_d1 respectively in peak inflow process.
• Select
  Erosion Characteristics of Exposed River-crossing Pipe under the Protection of Heavy Block

  YANG Qing-hua, WANG Zi-cong, YANG Qian, ZHANG Yu-qian

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 99-105. https://doi.org/10.11988/ckyyb.20210029

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The uncertainty of riverbed terrain changes caused by water scour poses a threat to the safe operation of river-crossing pipeline. In the aim of exploring the scour characteristics of exposed river-crossing pipelines under heavy block protection measures, a flume model test was carried out to investigate the influences of four factors, namely, length of heavy block, the spacing between heavy blocks, flow rate and water depth, on scour terrain and scouring depth of riverbed around the pipeline. The scouring process of underwater pipeline under the protection of heavy block can be divided into four stages: formation of scouring pits, suspension of heavy block on the upstream side, suspension of pipeline on the upstream side, and scour balance. The maximum scouring depth of pipeline is positively correlated with the flow velocity and the length of heavy block, but negatively correlated with the water depth and the spacing between heavy blocks. The functional relationship between the dimensionless scouring depth, the length of heavy block, the spacing between heavy blocks and Froude number is obtained by dimensional analysis method. The research findings could be a theoretical support for the design, construction, operation and maintenance of heavy block protection measures for underwater crossing pipeline.
ROCK SOIL ENGINEERING
• Select
  Experimental Study on Soil-Water Characteristic Curve of Coastal Saline Soil

  ZHANG Jian-hui, DING Zi-kai, CHEN Bao-ze, LIU Jing, YANG Hong-yu

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 106-110. https://doi.org/10.11988/ckyyb20201271

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The suction of coastal unsaturated saline soil at Huanghua Port with varied salt content and moisture content was studied via filter paper method. The soil-water characteristics together with the relationship between salt content and suction was examined, and the influencing factors and change rules of suction were analyzed. Moreover, the mathematical models of matric suction against volumetric water content, and osmotic suction against salt content and volumetric water content were established by fitting. Results revealed that the change of salt content had a great influence on total suction and osmotic suction. An exponential relationship was found between matric suction and volumetric water content. The model of osmotic suction against salt content and volumetric water content is of high goodness of fit.
• Select
  Stress and Deformation Characteristics of Composite Geomembrane Cofferdam with Different Patterns of Laying and Connection

  XU Han, LI Bo, PAN Jia-jun, LI Hao-min

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 111-115. https://doi.org/10.11988/ckyyb.20201244

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To improve the laying and connection type of composite geomembrane and to enhance its adaptability to cofferdam deformation is the key to the design of earth-rock cofferdam with composite geomembrane as seepage control system. Centrifugal model test was carried out to obtain the strain distribution of geomembrane in water-storage period; numerical simulation of the centrifugal model test was also conducted by using the membrane unit M3D4 provided by ABAQUS to acquire the spatial distribution characteristics of stress and deformation of composite geomembrane with different laying and connection patterns. The numerical simulation results were compared with the centrifugal model test results, and the comparison illustrated that the stress of geomembrane laid in an S-shape was more reasonable than that in linear type as the S-shape plays a reinforcing role and reduces the settlement of cofferdam. Strain concentrated in the connection part of geomembrane and the restraint effect of flexible connection is between that of anchorage connection and unconstrained connection, implying stronger deformation compatibility. The results of centrifugal model test can be well reflected by the geomembrane simulation algorithm.
• Select
  Macro-and-microscopic Analysis of Shear Strain Zone of Reinforced Tailings Based on Partical Flow Code

  YI Fu, JIN Hong-song, YU Hui-ze, DU Chang-bo, YU Ben

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 116-121. https://doi.org/10.11988/ckyyb.20201335

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  The aim of this research is to enhance the overall stability of tailings dam by identifying the influence range of shear zone of geogrid-reinforced tailings dam. The influence law of shear strain zone was analyzed from macro-and-microscopic perspectives via indoor direct shear tests of tailings sand with varied moisture contents under different overlying loads. Results unveiled that: the test displacement of geogrid-reinforced tailings increased approximately linearly with the peak displacement ranging between 20 mm and 25 mm; overlying load presented a positive proportional relationship with peak shear displacement, and the growth rate of shear displacement gradually attenuated. The water content of tailings sand was 3%, 7%, 11% and 15%, respectively, and the density of tailings declined by 2.2%. With the growth of water content, the apparent cohesion gradually strengthened, and the interfacial friction angle first climbed and then dropped. Furthermore, partical flow code(PFC) model was established to accurately locate the area with large displacement change in the test chamber for meso-scale non-punctuation measurement analysis. The influence distance of shear strain zone reduced with the increase of water content of tailings sand, and such reduction alleviated gradually.
• Select
  Surrounding Rock Classification Method for Tunnel Construction Based on Entropy Weight Method

  ZHANG Bo

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 122-127. https://doi.org/10.11988/ckyyb.20201326

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To overcome the subjectity in determining the index parameters of surrounding rock by existing classification methods, six parameters, namely, uniaxial saturated compressive strength, integrity coefficient, volumetric joint number, groundwater, quality index RQD, and elastic longitudinal wave velocity of surrounding rock, were selected as evaluation indexes. Surrounding rock classification was carried out by using entropy weight extension matter-element theory and entropy weight cloud model mathematical analysis method, respectively. The rationality and accuracy of the two methods were verified by the data of surrounding rock classification in the design and construction stage of Longnan tunnel of Ganzhou-Shenzhen high-speed railway. Results manifested that entropy weight method could overcome subjectivity and avoid human interference in calculating the weight coefficient of evaluation index. The present two methods of surrounding rock classification are conducive to the development of intelligent and information-based surrounding rock classification.
• Select
  Formation of Shear Zone and Evolution of Related Mesostructure in Rockfill under High Confining Pressure

  WU Xiang-hao, LIANG Bing-han, HUA Xiang-yu

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 128-134. https://doi.org/10.11988/ckyyb.20201299

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  In order to study the formation of shear zone and the evolution of mesostructures in rockfill under high confining pressure, we constructed three different shapes of broken particle clusters by using self-designed program, and randomly generated two-dimensional particle flow samples for biaxial compression test. Results show that when axial strain is 6%, the volume shrinkage of specimen changes to volume expansion; when axial strain reaches 10%, the structure changes in the sample. The formation of shear zone can be clearly reflected by the evolution of micro-structures such as rotation, movement, fragmentation and porosity of particle clusters in the sample; when axial strain reaches 10%, the particle clusters with large rotation amplitude and serious breakage and the region with large porosity both present asymmetric X-shaped distribution, and the X-shaped contour gradually becomes clear.
• Select
  Relative Permeability Coefficient Model of Unsaturated Soil with Multiphase Flow Based on Fractal Theory

  CAO Shuai, NING Jin-cheng, YANG Qing-guo

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 135-139. https://doi.org/10.11988/ckyyb.20201141

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Relative permeability coefficient is a crucial parameter describing the hydraulic characteristics of unsaturated soil. In researches of traditional relative permeability model for unsaturated soil, the seepage characteristic model of wet phase rather than non-wet phase received much focus. To study the multiphase flow transport model of unsaturated soil, we at first simplified the soil pores into a group of tortuous capillaries obeying the fractal law; by establishing the transport characteristic model of liquid and gas phase in porous media, we obtained the model of relative permeability coefficient of both liquid and gas phase of unsaturated soil in association with the Young-Laplace equation and the Buckingham-Darcy’s law. The model only contains two parameters, with clear physical meanings and can be measured by experiments. Eight groups of test data validated the rationality and applicability of the present model. We hence conclude that the model better describes the multiphase seepage characteristics of unsaturated soil.
• Select
  Two-dimensional Evaluation Model of Surrounding Rock Stability Based on OBLFOA-PP-BC

  CHEN Guang-yao, WANG Ming-wu, JIN Ju-liang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 140-148. https://doi.org/10.11988/ckyyb.20210010

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Projection pursuit is an efficient uncertainty analysis method in solving complex stability problems for surrounding rock. Its result is affected and controlled by the projection direction. To find an optimum projection direction vector and reflect the uncertainty of the process, we adopted an opposition-based learning fruit fly optimization algorithm (OBLFOA) to modify the projection pursuit evaluation model for surrounding rock stability. The classification threshold of projection pursuit is difficult to be divided in some special cases. In view of this, we constructed the normal cloud models for different grades of surrounding rock by using the optimal projection value according to the optimum projection value of measured samples. To determine the reliability of the model evaluation results and the fuzziness of the evaluation process, we introduced the fuzzy entropy E as the auxiliary parameter with the evaluation result L forming a two-dimensional evaluation mode (L, E). Since the evaluation indexes of surrounding rock stability are varied and the evaluation system is not unique, we selected two cases with different evaluation index systems for application and compared with other methods. Results indicated that the proposed model is feasibile and effective and the evaluation results are objective and accurate.
HYDRAULIC STRUCTURE AND MATERIAL
• Select
  Numerical Analysis of Micro-cracks in Rubber Concrete under Low Strain Conditions

  LI Hou-min, WU Ke-yang, KE Jun-hong, WANG Yang

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 149-155. https://doi.org/10.11988/ckyyb.20201331

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  To explore the propagation form of micro-cracks in rubber concrete and the factors affecting crack propagation, a random aggregate model composed of five phases (mortar, aggregate, rubber, rubber-mortar interface, and aggregate-mortar interface) was established by ANSYS redevelopment in APDL language. The model was applied to simulating the compression of rubber concrete, and on such basis, the relations of aggregate gradation with rubber and cracks distribution were examined by using grayscale recognition. Results illustrated that cracks developed rapidly in areas with dense rubber distribution. The number of crack pixels was proportional to the density of rubber distribution in the presence of low rubber content; when rubber content was high, the number of crack pixels first decreased and then increased with the densification of rubber distribution.
INFORMATION TECHNOLOGY APPLICATION
• Select
  Model of Extracting Remotely-sensed Information of Black and Odorous Water Based on Deep Learning

  SHAO Hu-xiang, DING Feng, YANG Jian, ZHENG Zi-cheng

  Journal of Changjiang River Scientific Research Institute. 2022, 39(4): 156-162. https://doi.org/10.11988/ckyyb.20210045

  Abstract ( ) Download PDF ( )   Knowledge map   Save

  Black and odorous water bodies are widely distributed and seriously damages people’s living environment and the overall beautiful image of the city. With Langfang City in Hebei Province as the research area, we conducted a comparative experimental study on the extraction of remote sensing information of black and odorous water bodies by using PSPNet (Pyramid Scene Parsing Network) and U-Net model based on the multi spectral data and measured data of GF-2 satellite. The normalized difference vegetation index (NDVI) and normalized difference black odorous water index (NDBWI) are calculated based on the visible light band (RGB) and near infrared band (NIR). In view of the common problem of missing detection of small black and odorous water bodies, the module of attention mechanism is introduced to optimize and improve the model. Thus, an improved deep learning model of extracting the remotely-sensed information of black and odorous water bodies is constructed. Results demonstrate that the U-Net model, which inputs RGB+NIR+NDVI+NDBWI six channel remote sensing images in combination with attention mechanism, has the most superior extraction result for black and odorous water bodies, and achieves 0.864 5, 0.868 1 and 0.835 9 in accuracy evaluation indexes F1-srore, MIoU and Recall, respectively.