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01 September 2020, Volume 37 Issue 9
    

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    SPECIAL CONTRIBUTION
  • WU Zhi-guang, TANG Xian-qiang
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 1-7. https://doi.org/10.11988/ckyyb.20200431
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    River chief system is a regional management policy for environmental protection. Joint protection and management at basin level is still a challenge and shortage in the implementation of the river chief system. With Chishui River, a representative inter-provincial river in the Changjiang River Basin as an example, we expound the key issues in the eco-environment protection of Chishui River, and make a review on the practices of applying river chief system. On such basis, we summarize the experiences and lessons learned from the protection and management of Chishui River according to the major tasks of river chief system. Moreover, we put forward policy measures for the joint protection and management in the following aspects: promoting the overall planning and legislation for basin comprehensive management, strengthening interdepartmental cooperation and joint law enforcement, standardizing cross-regional sectional monitoring and assessment, tightening basin water allocation and scheduling, and improving financial support and encourage. The present research will provide policy support for basin integrated protection and management for other inter-provincial rivers elsewhere in China.
  • WATER RESOURCES AND ENVIRONMENT
  • CHANG Wen-juan, DONG Xin, MA Hai-bo, FANG Hao-tian
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 8-12. https://doi.org/10.11988/ckyyb.20191464
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    An assessment model for water resources carrying capacity (WRCC) in consideration of water conservation and water transfer was constructed with the maximum economic scale and maximum population sustained by corresponding WRCC as assessment indicators. The WRCC in Hanjiang River basin in different target years at varying water transfer scales was assessed as a case study. Under the scenarios of diverting 9.5 billion cubic meters of water for the Middle Route of South-to-North Water Diversion Project and in the mean time 1.0 billion cubic meters for the Hanjiang River-to-Weihe River Water Diversion Project, the water resources in Hanjiang River Basin could still support the potential for socio-economic development of the basin, and could even afford water transfer to other basins with a maximum amount reaching 1.97 billion cubic meters and 1.56 billion cubic meters in target year 2020 and 2030, respectively. Nevertheless, in the scenario of diverting 13 billion cubic meters of water for the Middle Route of South-to-North Water Diversion Project in 2030, the water resources in Hanjiang River Basin could no longer support the sustainable development of the basin, and external water compensation from outside the basin should be needed. In addition, a coordination degree model was constructed to evaluate the capacity of water resources sustaining socio-economic development on macroscopic level based on the theory of synergy with sequential parameters containing water consumption factor. From 2011 to 2017, the water resources carrying system in Xiangyang gradually developed from relatively uncoordinated to basically coordinated. The overall WRCC tended to develop soundly in consideration of water conservation. The research findings offer scientific basis as well as technical support for researching the trans-basin water diversion scale in the Hanjiang River basin in the long run and for determining the water compensation scale from the Yangtze River.
  • AI Sen, YANG YA-hong, XU Guang-lian, ZAI Ying-han, ZHANG Hui-ning, BAI Zhi-hui
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 13-17. https://doi.org/10.11988/ckyyb.20190521
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    Large content of total nitrogen (TN) in the tail water discharged from industrial wastewater treatment plant is likely to cause eutrophication in surface water. In order to improve the removal efficiency of TN in the tail water, we investigated into the removal rate of TN by biofilm floating bed strengthened with different amounts of rice straw (0, 0.18 g/L, and 0.54 g/L) by simulated static and dynamic stabilization pond experiment. Static experiment result showed that the removal rate of TN increased significantly along with the increment of rice straw amount; after 10 days, the removal rate of TN was respectively 18%, 40%, and 93% when 0 (CK), 0.18 g/L (T1), and 0.54 g/L (T2) rice straw were added into the floating bed. Dynamic experiment result revealed that the mean TN removal rate of CK, T1 and T2 was respectively 10%, 22%, and 49% when the hydraulic retention time (HRT) was 4 d; no significant difference was found in COD concentration in the influent and effluent under the three conditions due to the fact that rice straw provides organic matter for heterotrophic denitrifying bacteria in biofilms by slowly releasing carbon source.
  • FENG Jian-guo, JI De-shuai, GAO Zong-jun, YANG Li-zhi, ZHU Heng-hua, LIU Zhi-zheng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 18-23. https://doi.org/10.11988/ckyyb.20190476
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    The hydrochemical characteristics and water quality status of karst confined water in Dawu water source of Shandong Province were investigated using mathematical statistics, correlation analysis, Piper's plot, Gibbs model and ion ratio method by analyzing 57 groundwater samples taken in 2017. The major ion characteristics and causes were examined, and the water quality was assessed by comprehensive evaluation method. Results reveal that Ca2+ and Na+ are the major cations of groundwater, accounting for 82.8% of the total cations; HCO3-, SO42-, and Cl- are the main anions, accounting for 91.9% of the total anions. HCO3·SO4-Ca· Mg(Ca), HCO3·SO4·Cl-Ca·Mg(Ca), and HCO3·Cl-Ca·Mg(Ca) are dominant hydrochemical patterns. The hydrochemical components are mainly controlled by weathering and dissolution of carbonate rock. The groundwater quality is above class Ⅲ, which accounts for 47.4% of the total water samples, while Ⅳ and Ⅴ classes occupy 52.6% of the total water samples.
  • ZHANG Qian-zhu, DENG Hao-jun, LU Yang, ZHOU Huo-ming, GAO Qiang, ZHOU YU-hong
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 24-30. https://doi.org/10.11988/ckyyb.20190716
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    The chemical runoff materials of rivers usually originate from rock weathering, soil erosion and human activities in the basin. Hydrochemical characteristics comprehensively present the environmental information of the basin. The hydrochemical characteristics and influence factors of Danjiangkou Reservoir are investigated in this paper based on sampling data in October 2017, January 2018, April 2018, and July 2018. The pH value of water in Danjiangkou Reservoir is between 7.02 and 8.58, which is moderately alkalescent. The dissolved oxygen, ORP and conductivity of water change obviously with seasons. The average value of TDS is 176.14±15.98 mg/L, much higher than that of other rivers in the world. Among the main cations in the water, Ca2+ is the highest in content, ranging from 50% to 70%, and the content of Mg2+ is between 20% and 30%. Among the anions, the content of HCO3- in most of the samples is more than 70%; the content of (Cl-+SO42- ) is below 20%; and the content of DSi is below 10%. The statistical results show that the weathering of carbonate rocks controls the overall characteristics of the water. Some of the ions are affected by the weathering of silicate rocks. Human activity is also an important factor affecting the chemical characteristics of the water. Compared with previous monitoring results, the water quality in Danjiangkou Reservoir has been improved. The research results provide data support for the comprehensive management, development and utilization of water resources in the basin.
  • CAI Zhuo-sen, DAI Ling-quan, LIU Hai-bo, DAI Hui-chao, TANG Zheng-yang, WANG Yu
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 31-38. https://doi.org/10.11988/ckyyb.20190622
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    The downstream of Jinsha River is a national nature reserve for rare fishes. The natural reproduction and growth of fishes need appropriate ecological flow (AEF). In the purpose of exploring the effect of Xiluodu-Xiangjiaba cascade reservoirs on the AEF in the downstream of Jinsha River, the Range of Variability Approach (RVA) was employed to quantify the downstream AEF. A multi-objective model for the scheduling optimization of cascade reservoir group was established with objectives of maximizing power generation and minimizing the change degree of downstream AEF. The model was solved by Non-dominated Sorting Genetic Algorithm II (NSGA-II). The inflow of typical wet, normal and dry years was selected for the optimization. Results demonstrate that under the constraints, power generation in wet year increases by 0.7% to the maximum and the corresponding change degree of AEF soars by 20.82%; with ecological flow as objective, the change degree of AEF can be reduced by 28.06% by losing 0.48% of the power generation. The power generation in normal year increases by 1.28% compared with conventional operation, meanwhile the change degree of AEF augments by 13.87%; such change degree could decline by 22.53% by cutting power generation by 0.62%. The power generation in dry years grows by 1.89% compared with conventional operation while the change degree of AEF raises 4.96%; under the ecological objective, the change degree of AEF could lessen by 13.7% by curtailing 0.35% power generation. The research findings offer reference for the planning of ecological scheduling of Xiluodu-Xiangjiaba cascade reservoirs in the lower reaches of Jinsha River.
  • FLOOD PREVENTION AND DISASTER REDUCTION
  • YU Yu-cong, LI Wen-qing, LIU Zhao, YANG Zhou, YOU Feng-hua
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 39-44. https://doi.org/10.11988/ckyyb.20191511
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    Determining flood season stages and corresponding water levels in flood season stages rationally could help coordinate the contradiction between flood control benefit and power generation benefit of reservoirs, and is also of great significance to give full play to flood control and power generation capacity of reservoirs and improve the utilization rate of flood resources in flood season. In this paper, the flood season of cascade reservoirs(Wudongde,Baihetan,Xiluodu,and Xiangjiaba) in the lower reaches of Jinsha River is divided into stages according to the incoming flood using the improved fuzzy set analysis method, and the staged limit water level of cascade reservoirs is determined through the mapping relationship between membership degree and flood control capacity. The stages and corresponding limit flood levels are revised with intertemporal sampling method. Research results reveal that the pre-flood season of cascade reservoirs in the lower reaches of Jinsha River is July 1-July 14, main flood season July 15-September 16, and post-flood season September 17-October 24. The reasonable limit flood level for the four reservoirs is 962 m, 800 m, 575 m and 374 m, respectively. The staged limit flood levels are verified through the flood process of different typical floods. The staging results obtained in this study and the phased limit flood level of each reservoir could improve the economic benefits of reservoirs' power generation under the premise of flood control safety, and enhance the utilization rate of flood resources in flood season.
  • WANG Zhao-duo, CUI Li-fang, DENG Li-huan, CHEN Ke
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 45-49. https://doi.org/10.11988/ckyyb.20191155
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    Six notable flood marks and corrosion grooves on the Shizhongshan cliff of Poyang Lake higher than the current water level were identified through observations, and were further compared with the Holocene sedimentary profile of Poyang Lake and other climate information. The flood marks and grooves indicate the change and the duration of water level of Poyang Lake in different periods. Three lower flood marks are highly reproducible and last for short time, while the higher three flood grooves are less reproducible and last longer, which may indicate the water level of Poyang Lake in the context of warm period since mid-Holocene. By comparing the flood marks and grooves with the Holocene sedimentary profile on the east side of Poyang Lake and the climatic background in the corresponding period, we can infer the possible formation times of flood imprints and grooves at different heights, and preliminary reveal the historical flood information of water level change of Poyang Lake in the middle and late Holocene. The present research proves that the water level of Poyang Lake is indeed closely related to the climate background.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • YANG Pan-pan, WANG Nian-qin, GUO You-jin, MA Xiao
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 50-56. https://doi.org/10.11988/ckyyb.20190726
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    A weighted information value (WIV) model integrating random forest (FR) model and information value (IV) model is proposed in an attempt to improve the precision and accuracy of landslide susceptibility assessment. Lintong District of Xi'an City is taken as the research area. According to field survey and factor correlation analysis, ten factors including slope gradient, slope aspect, elevation, curvature, topographic relief, rock and soil type, rainfall, fault, water system, and road are selected as influence factors for the assessment. With 72 landslide hazard points as sample data, the landslide susceptibility is assessed using RF model, IV model and WIV model, respectively. Results demonstrate that the success rate and prediction rate of WIV model training samples are higher than those of FR model by 4.90% and 1.90%, respectively, and higher than those of IV model by 7.80% and 4.70%, respectively. Highly and extremely highly susceptible areas are mainly distributed in faults, rivers and roads. The rate of landslide hazard points in highly and extremely highly susceptible areas by WIV model is 6.37% and 4.44% higher than that by IV model and FR model, respectively. In conclusion, the results of WIV model are consistent with the actual situation of the research area.
  • ROCKSOIL ENGINEERING
  • PENG Shu-quan, ZHANG Ke-jia, KANG Jing-yu, FAN Ling, WANG Fan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 57-63. https://doi.org/10.11988/ckyyb.20190657
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    As a novel microbial reinforcement technology, microbially induced calcium carbonate precipitation (MICP) could change the hydraulic performance of fractured rock mass and barrier penetrations. Bacillus pasteurii was used as microbial filler to test the permeability performance of red sandstone specimens with penetrated fracture prepared by splitting. Furthermore, electrochemical impedance spectroscopy (EIS) method was employed to examine the influence of microbial filling on the structure of fractured rock mass, and further probe into the impermeability mechanism. Research results unveiled that 1) the permeability of fractured red sandstone can be reduced by 1-2 orders of magnitude by MICP; higher filling rate will result in better effect. 2) Crack width and confining pressure have impact on the change of permeability coefficient of fractured rock after microbial filling. 3) The permeability coefficient of fractured rock before and after microbial filling declines in a power relation with the growth of confining pressure. 4) The fractured sandstone after microbial filling is more conductive and denser than that before microbial filling, which explains the reduction of permeability coefficient.
  • HU Qi-zhi, HONG Chang-wei, LIU Heng, XU Zhao-dong
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 64-69. https://doi.org/10.11988/ckyyb.20190700
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    Granite residual soil is often used in the filling of highway roadbed because of its high strength; nevertheless in rainy season, the quality of filling would be affected markedly by rainfall due to granite residual soil's strong permeability and poor anti-scour ability. By adding red clay into granite residual soil, the influence of red clay content on permeability coefficient and unconfined compressive strength of granite residual soil was examined via permeability test and unconfined compressive strength test. On the basis of indoor test, comparative study was also carried out with specific filling project. Results revealed that with the increasing of red clay content, the permeability coefficient of granite residual soil declined while unconfined compressive strength augmented. The optimum content of red clay in granite residual soil is 40%. In actual project, two vehicles of granite residual soil mixed with one vehicle of red clay could achieve good filling effect. The research findings could be references for the filling and reinforcement of project construction in granite residual soil area.
  • LEI Ya-wei, ZHENG Gang, CHENG Xue-song, HUANG Tian-ming, LI Xi-yuan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 70-78. https://doi.org/10.11988/ckyyb.20190563
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    Although collapse cases caused by partial over-excavation are seen frequently, studies on the overall safety performance and the progressive collapse mechanism caused by partial over-excavation are still in lack. In this study, the load transfer mechanism of cantilever contiguous retaining piles of long strip excavation subjected to partial over-excavation were investigated by finite difference method and model test. Results revealed that with the increase of over-excavation depth, the internal force of the piles beyond over-excavation zone increased by a large margin due to soil arch effect, while the bending moment of piles within over-excavation zone increased first and then decreased or continued to decrease. When the excavation depth in a large area remained the same, the increments in bending moment and displacement of adjacent piles intensified gradually and tended to be stable along with the widening of partial over-excavation range. The research results reveal the load transfer rules reflecting the influence of partial over-excavation on internal force of piles.
  • WU Da-yong
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 79-86. https://doi.org/10.11988/ckyyb.20190561
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    To ensure the construction safety of tunnel's entrance segment, the causes of collapse at the entrance segment of Xiaozhaishan Tunnel are analyzed. On such basis, the status and development trend of surrounding rock stability are assessed using the cusp catastrophe theory and PSO-ELM (Particle Swarm Optimization based Extreme Learning Machine) model. The collapse treatment measures are systematically studied, and the treatment effects are analyzed to evaluate the effectiveness of measures. Results demonstrated that the major causes of collapse are deviatoric pressure and rainfall. The catastrophe characteristic values in the process of catastrophe analysis are less than zero, indicating that the surrounding rock of entrance segment is in an unstable state. In addition, deformation prediction results suggest that the deformation would continue, which is unfavorable for the stability of the entrance segment. Collapse treatment measures should be comprehensive and systematic to maintain the deformation of surrounding rock within controllable range. The effectiveness of various treatment measures is verified. The research findings offer a new idea for the prevention and control of hazards at such entrance segment of tunnels. Moreover, the collapse treatment measures should be implemented according to the practice of actual project. Targeted reinforcement should be carried out on surrounding rock in each construction stage, and then the macroscopic stress state of the tunnel support should be adjusted to ensure the stress balance. After treatment, the deformation of surrounding rock in Xiaozhaishan tunnel entrance is within controllable range, which verifies the effectiveness of the treatment measures.
  • WANG Jia-le
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 87-95. https://doi.org/10.11988/ckyyb.20190822
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    In the light of the modified Timoshenko beam theory, a vibration-control differential equation of the modified Timoshenko beam on viscoelastic Winkler foundation is established in consideration of the viscous damping of foundation. The present equation overcomes the shortcoming of the classical Timoshenko beam on viscoelastic foundation that “one mode has two frequencies”. The frequency solution to the transcendental equation and its modal function under various boundary conditions are derived by complex modal analysis. When the influence of shear inertia caused by shear deformation of beams is not taken into account, the equation degrades to the classical Timoshenko beam model of viscoelastic Winkler foundation; when the shear deformation of beams and the viscous damping of foundation are not taken into account, the equation decays to the common Euler beam vibration model of elastic foundation. The computational model in this paper is a more general one. The calculation differences of viscoelastic foundation beams under different theories are analyzed. The results show that Euler beams on viscoelastic foundation have great errors in high frequency band as well as in low frequency band with short beams. The error of classical Timoshenko beams on viscoelastic Winkler foundation is smaller than that of Euler beams; but the relative error increases gradually with the increase of order, and the influence cannot be ignored in high frequency band. The research finding proves that the viscous damping of foundation has great influence on the low frequency vibration of foundation beam.
  • XIAO Xin-hong, WANG Jing, XIE Xiao-shuai, CHEN Hua-song, ZHOU Jia-wen
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 96-101. https://doi.org/10.11988/ckyyb.20190580
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    The rheological property of soft rock under water-rock interaction is crucial for the long-term stability of geotechnical projects in real water environment. The creep characteristics of red mudstone in central Yunnan under different stresses and water pressures were studied by means of rock rheological test system under combined action of axial compression and hydraulic pressure. Results unveiled that instantaneous deformation was dominant at low stress level, and the creep curves mainly displayed attenuation and steady stages; accelerated creep stage only appeared at the last stress level. Given the same hydraulic pressure, the instantaneous strain, creep strain and creep rate of mudstone increased with the augment of loading stress; creep characteristics of mudstone are more sensitive to the stress under high water pressure. Under the same stress level, the creep strain, creep rate and the proportion of creep deformation to total deformation of mudstone increased with the climbing of water pressure; such increment intensified under higher stress. The research findings are of engineering significance for ensuring the safety of soft rock project in real water environment.
  • WU Jin-bo, WU Qing-hua
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 102-109. https://doi.org/10.11988/ckyyb.20200104
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    The stability of Huangtupo landslide in the Three Gorges Reservoir area has always received attentions from researchers as it exerts significant influence on the safe operation of the Three Gorges Project. Nevertheless, the mechanism of porosity and seepage of slip zone affecting the landslide stability is still unclear. In the present paper, the pore structure and seepage characteristics of the slip zone soil of Huangtupo landslide are investigated in consideration of groundwater seepage via collecting samples from Badong field test site and by using laboratory approaches. Results reveal that 1) the roundness and distribution pattern of gravels, the clear stratigraphic boundary of slip zone as well as the friction marks between gravel and bedrock surface all indicate that the slip zone soil is of evident sliding features. 2) Penetrating cracks at the upper bound (interface between the slip zone soil and landslide accumulation body) of slip zone and the lower bound (interface between slip zone soil and bedrock) are the concentrated seepage channels of groundwater. The slip zone soil is of apparent stratification structure; however, the soil is dense, and groundwater doesn't flow preferentially along the gap between soil layers under the condition of low groundwater head. 3) The saturated permeability coefficient of slip zone soil is lower than those of overlying unconsolidated accumulation body and strongly-weathered bedrock by 2-3 orders of magnitude, which results in the concentrated drainage of rainfall water through the upper bound and fissure water in bedrock through the lower bound. Under the action of matric suction, the groundwater slowly infiltrates into the slip zone soil from both upper and lower bounds, implying that slip zone soil notably controls the groundwater flow. 4) Under natural water head, the slip zone soil is of strong resistance against seepage destruction as the seepage gradient at failure exceeds 16, which suggests that groundwater mainly increases the moisture content and reduces the mechanical properties of slip zone soil rather than destructs it.
  • TU Ying, YANG Jian-hua, DAI Jin-hao
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 110-114. https://doi.org/10.11988/ckyyb.20190894
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    The blasting excavation of an underground laboratory was carried out with the upper and lower layers excavated simultaneously. The peak particle velocity (PPV) and frequency characteristics in the lower layer of rock mass during the horizontal-hole blasting in the upper layer were investigated by using field blasting vibration monitoring. On this basis, the influence of upper-layer blasting on the dynamic stability of lower-layer rock mass was analyzed. Results demonstrate that during the horizontal-hole blasting in the upper layer excavation, the explosion-induced seismic wave energy preferentially propagates into the lower rock mass, which results in the PPV at the roof of the lower opening to be greater than that on the upper floor at the same distance. With regard to the downward-propagating seismic waves, a significant amount of energy is transported in the shear-vertical (SV) mode. As a result, the maximum vibration velocity component occurs in the direction along the blasthole axis (also the laboratory axis). In addition, the vibration frequency in the lower rock mass is significantly higher than that on the upper floor because the downward-propagating body waves travel at depth in a relatively competent medium, while the surface vibration on the upper floor travels in a weaker layer.
  • KANG Chen-yun, WANG Shao-kai, PAN Deng-li, HE Ming
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 115-121. https://doi.org/10.11988/ckyyb.20190569
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    Loess joints are the places where groundwater exists and migrates. They break the soil, and affect the stability and strength of loess, causing enormous losses on both economy and human lives. Joints are the structural basis of all kinds of loess disasters. Accurate analysis of its development characteristics and distribution rules is crucial to understanding the frequent occurrence of loess disasters. Through systematic field investigation, mathematical statistics and topological analysis of loess in Longxi, we found that: (1) The dominant strikes of loess tectonic joints in Longxi are NNW,NWW and NE, which is influenced by strike-slip fault and reverse tilting fault.(2) The occurrence of dominant tectonic joints group obeys the Gaussian normal distribution, with the dip angle mostly within 60-80°. The occurrence of vertical joints are more randomly distributed and highly discrete. (3) The average spacing of both tectonic and vertical joints is wide, the opening of joints belongs to “crack” in standard, and the continuity medium, except that the spacing of vertical joints is more concentrated, while the opening of tectonic joints is smaller by comparison. (4) Topological analysis shows that I-node is the majority. Joints extension process is easily interrupted. Branch ratio is at a low level below 3. Topological analysis is more simple and intuitive to describe connectivity, especially under the help of powerful toolbox in software, and has been discussed for decades in the world, yet is rarely used in relative research in China. The research results provide basic data for the recovery of Neotectonics stress fields, for understanding the basic laws of joints development and the numerical modeling of joints network.
  • LI Cao, ZHANG Meng-xi, ZHOU Rong-feng, WANG Ze-qing
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 122-127. https://doi.org/10.11988/ckyyb.20190593
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    The construction of traditional pile foundation is featured by environmental pollution, soil squeezing effect, low efficiency and high energy consumption. In an attempt to tackle these problems, the deformation characteristics and vibration of pile's surrounding soil during pile sinking and those of a high-rise bridge pier during adjacent subway running were investigated via in-situ pile sinking test and field vibration test. The resonance-free hydraulic vibratory hammer system was adopted for pile sinking test. Results demonstrated that the horizontal displacement of soil around the pile during pile sinking concentrated in the range of 0-2/3L(L represents pile length) near the ground surface, and in particular, the horizontal displacement in the range of 0-1/4L below the surface was very large. The maximum horizontal and vertical displacement of surrounding soil was 2.37 mm and 3.13 mm, respectively, and the inclination of the pier was 0.4‰-0.7‰. The soil squeezing effect was not obvious during the pile sinking. Field vibration test results showed that the maximum peak velocity was 0.823 mm/s in the absence of subway running, while in the presence of subway running, the peak velocity was 1.90 mm/s, which indicates that the impact on the surrounding environment is weak during pile sinking.
  • ZHU Nan, LIU Chun-yuan, ZHAO Xian-hui, WANG Wen-jing
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 128-134. https://doi.org/10.11988/ckyyb.20190551
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    Triaxial drainage shear tests are conducted on undisturbed and remolded samples of marshy and lacustrine clay to explore the mechanism of structure affecting shear strength and deformation. The undisturbed soil samples after the triaxial drainage shear test are photographed by scanning electron microscope (SEM) and the SEM photos are qualitatively and quantitatively analyzed by IPP program. In addition, the effects of soil structure on shear strength and deformation and the change of microstructure of marshy and lacustrine clay are examined under different consolidation pressures. Results demonstrate that before the yield failure of soil structure, the soil structure of the undisturbed soil could enhance shear strength and reduce shear deformation, while after the yield failure of soil structure, the soil structure of undisturbed soil reduces shear strength and instigates shear deformation which is similar to the remolded soil. Moreover, the peak structural strength of undisturbed soil increases linearly and the peak structural volumetric strain decreases exponentially with the growth of confining pressure. When consolidation pressure is smaller than structural yield stress, the soil structure damages slightly in consolidation stage, and the shear load is bore by the bonding and fabric of the undisturbed soil in shearing stage. Meanwhile, the pores are almost uncompressed and the shape and arrangement of particles and pores have changed slightly. However, when consolidation pressure exceeds the structural yield stress, the soil structure damages significantly in consolidation stage and the bonding and fabric gradually degrades in shearing stage. As a result, the pores are compressed, the shape of particles and pores gradually becomes circular, and the arrangement orientation of particles and pores adjust with the direction of load.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • FU Ying-kun
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 135-141. https://doi.org/10.11988/ckyyb.20190736
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    In order to study the creep characteristics of concrete under the complex conditions of seawater corrosion, load and hydraulic seepage, we conducted triaxial staged-loading creep test on port concrete immersed in seawater for different days. Test results demonstrate that: 1) seawater corrosion has a significant weakening effect on the strength of port concrete. The long-term strengths of concrete immersed for 0,30,60,120 days are 12.8 MPa, 11.5 MPa, 10.6 MPa, and 10.2 MPa, respectively. 2) As the time of immersion elongates, the initial permeability of concrete increases gradually. The initial permeability of concrete immersed for 0,30,60,120 days are 8.15×10-17 m2, 1.12×10-16 m2, 1.49×10-16 m2, and 1.60×10-16m2, respectively. However, the corrosion effect of seawater attenuates gradually, and the initial permeability is negatively correlated with the corrosion time. 3) The non-linear creep constitutive equation of improved Nishihara model has an ideal fitting effect with the test data, and the determination coefficients are up to 0.98, 0.96, 0.95, and 0.92, respectively, well reflecting the stage characteristics and aging characteristics of creep deformation of port concrete under the coupled action of stress, seepage and corrosion. The research results can provide guidance for the long-term operation of port project in China.
  • CHEN Rui, GONG Jing-wei
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 142-148. https://doi.org/10.11988/ckyyb.20190652
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    A thermal conductivity model of concrete under temperature variation is proposed in the purpose of exploring the influence mechanism of alternating positive and negative temperatures on the thermal conductivity of concrete. The calculation theory of thermal conductivity of liquid phase (ice-water phase) in concrete pore at different temperatures is proposed to characterize the phase transformation characteristics of pore solution in concrete at different temperatures.Concrete is regarded as a three-phase composite material consisting of equivalent solid phase, liquid phase (ice-water phase), and gas phase in concrete pore. The series-parallel calculation model for the thermal conductivity of concrete as a three-phase composite material varying with temperature, saturation, and pore distribution is established and compared with other models. The thermal conductivity of concrete calculated by the present series-parallel model is in good agreement with measured values, with the relative error ranging from 8.83% to 24.13%, indicating high accuracy. The calculated results of the model well reflect the correlation between thermal conductivity and saturation and temperature of concrete in cold region. In sensitive temperature (-10 ℃~0 ℃) zone, the thermal conductivity of concrete changes abruptly with an amplitude from 2.59% to 8.47%. The liquid-phase (ice-water phase) model effectively depicts the phase transformation of pore solution under temperature variation, and the series-parallel three-phase model also objectively reveals the evolution mechanism of thermal conductivity of concrete under alternating positive and negative temperatures.
  • 2020 ANNUAL CONFERENCE (ACADEMIC SEMINAR) OF SURVEY SPECIALIZEDCOMMITTEE OF CHINESE HYDRAULIC ENGINEERING SOCIETY
  • HUANG Zhen-wei, LEI Ming, ZHANG Wei-peng
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 149-153. https://doi.org/10.11988/ckyyb.20200580
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    Asphalt concrete core wall is an important structure of earth rock dam. The quality of raw materials such as aggregate and filler has a decisive influence on the impermeability, durability and deformation adaptability of the core wall. With Laluo water conservancy project in Rikaze city of Tibet Autonomous Region as an example, we compared two artificial aggregate quarries for the asphalt concrete through testing and inpection of multiple quality parameters. After comprehensive consideration of various factors, we selet Kagong limestone yard which is more distant yet boasts better rock quality as the material source to ensure the safety of asphalt concrete core dam in plateau, cold and high altitude areas. Moreover, we analyze and discusse some problems that should be paid attention to in the quality evaluation of raw materials of artificial aggregate for asphalt concrete, and put forward some suggestions to solve the problems for reference in the revision of relevant standards.
  • WANG Wang-sheng, CHEN Chang-sheng, WANG Jia-xiang, SHI Cun-peng, LI Yin-quan
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 154-159. https://doi.org/10.11988/ckyyb.20200565
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    Xianglushan deep-buried long tunnel is a control project for the total construction period of the water diversion project in central Yunnan Province. With a total length of 62.596 km and maximum buried depth of 1 450 m, the tunnel is featured with large survey scope, complex geotectonic background and complicated karst hydrogeological conditions as well as sensitive groundwater environment. In survey period, the tunnel line was selected and its engineering geological and hydrogeological conditions and major engineering geological problems were basically ascertained. In this paper, we probe into such problems including the seismic resistance in high earthquake-intensity area and shear resistance of structures passing through active fractures, the environmental impacts of water inrush and mud intrusion, the high geostress, hard rock burst, large deformation of soft rock, high external water pressure, and the special geotechnical engineering problems of coal stratum and expansive soils. The research result offers a technical support for the design and construction of tunnel and a reference for researches on similar deep-buried long tunnels.
  • MU Hong-yuan, MI Jian, LI Shao-fei, LIU Xiao-ning
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 160-164. https://doi.org/10.11988/ckyyb.20200571
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    In order to alleviate the impact of Haidong tunnel construction in the water diversion project in central Yunnan Province on groundwater environment, we investigated into the hydrogeological characteristics of karst water system and the groundwater environment in the tunnel route area by comprehensive means inclusive of hydrogeological survey and mapping, prospecting and observation, as well as analytical and numerical approaches. We also optimized the route scheme of Haidong tunnel in consideration of its impact on groundwater environment, and recommend the line B scheme which has less impact on groundwater environment. The present research offers a reference for the selection and comparison of tunnel scheme for water diversion project.
  • WU Peng-fei, JIA Zhen, ZHANG Xue-chao, ZHANG Xue-dong, CHEN Shu-wen
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 165-168. https://doi.org/10.11988/ckyyb.20200569
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    Altered granite develops in the dam site of Daigusi Reservoir in Gansu Province. The alteration characteristics of altered granite directly affect the engineering characteristics of rock mass and the safety of permanent and temporary hydraulic (construction) buildings. The engineering characteristics of altered granite in the dam site area of Daigusi Reservoir were examined in macro-and-microscopic scales via field survey, sampling test, and geophysical prospecting. Results suggest that the altered granite is mainly caused by magmatic and vein hydrothermal metasomatism, and the alteration type is mostly argillization. Altered granite concentrates in the riverbed and the low elevation parts of the near-river right-side rock in 70-180 meters downstream of Daigusi Hydropower Station; the depth of alteration is concentrated in the range of 20-100 meters below ground surface. The altered granite is featured with remarkably reduced strength, increased porosity and water absorption, as well as sound integrity.
  • LI Guo-rui, WANG Jie, LIU Kang-he, TANG Ke-xuan, WANG Zhi-hao
    Journal of Changjiang River Scientific Research Institute. 2020, 37(9): 169-174. https://doi.org/10.11988/ckyyb.20200566
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    Comprehensive detection technologies are applied in this research to detecte crack leakage of a concrete gravity dam. The leakage inlet is detected by using pseudo-random flow field method, and the range of leakage channel is located by drilling and drilling test technologies including temperature logging, acoustic logging, borehole television observation, water pressure test, and so forth. Results demonstrate that: 1) pseudo-random flow field method could precisely delineate the scope of leakage inlet in the dam in the presence of obvious leakage outlets; 2) cracks in the dam body generally distribute vertical to the direction of the dam body (such as connecting transverse joints) or along the direction of the dam body (such as horizontal joints), or both of them are connected; 3) drilling on dam crest and borehole test method are effective in identifying the elevation and pile number distribution range of leakage channel. The comprehensive detection methods integrating pseudo-random flow field method and borehole testing technology are accurate, rapid, convenient, and safe in detecting the crack leakage of concrete dam, thus can be taken as reference for similar engineering problems.