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    Recent Evolution Features of Tongzhou Shoal Channel in Chengtong Reach of Lower Yangtze River
    YU Wen-chou, LUAN Hua-long
    Journal of Yangtze River Scientific Research Institute    2020, 37 (12): 1-7.   DOI: 10.11988/ckyyb.20200579
    Abstract44)      PDF(pc) (6025KB)(44)       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.
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    Artificial Propagation of Herzensteinia microcephalus (Herzenstein, 1891) in the Southern Headwaters of the Yangtze River
    LI Wei, ZHAO Liang-yuan, ZHAO Wei-hua, GUO Wei-jie, QIAO Qiang-long, LIU Min
    Journal of Yangtze River Scientific Research Institute    2020, 37 (12): 8-13.   DOI: 10.11988/ckyyb.20200725
    Abstract36)      PDF(pc) (4388KB)(36)       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.
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    Slope Unit Extraction Methods: Advances and Prospects
    WANG Kai, ZHANG Shao-jie, WEI Fang-qiang
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 85-93.   DOI: 10.11988/ckyyb.20190210
    Abstract32)      PDF(pc) (6825KB)(107)       Save
    Slope unit is an important tool for assessment and prediction of regional landslide hazards. Currently several extraction methods based on the different definitions of slope unit has been proposed. In this paper we aim to analyze and summarize the advantages and limitations of common extraction methods from the view of landslide stability analysis. Among these methods the MIA-HSU method appeared in recent years is introduced in emphasis. Some limitations in common of these methods are drawn as follows: the excessive dependency on DEM resolution, the user-defined thresholds, and the lack of convenient optimization method. Finally, we suggest that future extraction method should pay more attention to the extraction of geologic environment boundary.
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    Analysis of Bonding Strength between Rebar and Recycled Concrete Based on Statistical Regression
    NIU Jian-gang, XU Yao, XIE Cheng-bin
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 156-159.   DOI: 10.11988/ckyyb.20190240
    Abstract29)      PDF(pc) (2683KB)(77)       Save
    In the purpose of researching the bond strength between reinforcing steel bar and recycled concrete, we examined the influences of parameters including compressive strength and protective layer thickness of recycled concrete as well as length of anchorage and diameter of rebar on the bonding strength according to test data of the bond performance between steel and recycled concrete. We employed the least squares method to obtain the equation of bonding strength by statistical regression and verified the equation by comparing the calculation result with test data. Result demonstrated that with the increase of compressive strength and protective layer thickness of recycled concrete, the bonding strength between rebar and recycled concrete also increased; however, with the elongation of steel anchorage length, the bonding strength reduced. The bonding strength when rebar diameter was 10 mm was larger than that of other diameters. The calculated results are close to the test results, indicating that the model presented in this paper is reasonable.
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    Effects of Water Uptake by Plant Roots on Slope Stability
    ZHANG Pan, XU Yong-fu, WU Xiao-tian
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (8): 120-125.   DOI: 10.11988/ckyyb.20190375
    Abstract28)      PDF(pc) (4331KB)(106)       Save
    Due to transpiration, the uptake of water by plant root plays a vital role in the stability of soil slope. To quantify such effect, the water uptake by four types of plant roots(uniform, triangular, exponential, and parabolic) were simulated using finite element method,and the effects of root’s geometry and depth on pore water pressure were also analyzed. Results demonstrate that with the proceeding of water uptake, shallow pore water pressure gradually decreases, while safety factor climbs, the shear strength of unsaturated soil increases, and slope stability enhances. The envelopes of pore water pressure and safety factor ratio of the four types of plant roots are basically the same as the root distribution’s shape function. The exponential root has the most superior reinforcement effect on slope because of its lowest ground surface pore water pressure and largest safety factor ratio. Given the same total root amount, the greater the root depth is, the larger the influence zone is, and the lower vegetated soil’s shear strength and smaller factor of safety increment.
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    Advances in Structural Analysis Methods for Optimal Operation of Reservoirs System
    ZHOU Ting, QI Wang-yue, JIN Ju-liang
    Journal of Yangtze River Scientific Research Institute    2020, 37 (12): 14-21.   DOI: 10.11988/ckyyb.20191117
    Abstract27)      PDF(pc) (6430KB)(23)       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.
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    Influence of Rolling Mode on Engineering Characteristics ofCoral Sand Foundation
    WANG Wei-guang, HAO Xiu-wen, LI Wan, YAO Zhi-hua
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (8): 113-119.   DOI: 10.11988/ckyyb.20190599
    Abstract26)      PDF(pc) (5082KB)(93)       Save
    The influence of compaction mode on the mechanical deformation performance of coral sand foundation is examined by means of in-situ detection and settlement monitoring. The reinforcement project for coral sand foundation of an airport is taken as a case study. In line with the engineering properties of reclaimed coral sand foundation, vibratory compaction method and impact compaction method are employed in foundation treatment in different test areas. Results show that the CBR (California Bearing Ratio) could reach 38% after 20 times of vibration compaction, whereas after 30 times of impact rolling, the CBR value is only 28%. After 30 times of vibration rolling, the uncorrected characteristic value of foundation bearing capacity is above 270 kPa, the response modulus of soil foundation is up to 106.68 MN/m 3, and the rolling-induced settlement deformation tends to be stable. Under the same number of times of compaction, the bearing capacity and deformation resistance of the foundation after vibration compaction are obviously higher than those after impact compaction, indicating that vibration compaction is more suitable for coral sand foundation treatment than impact compaction. The in-situ immersion test in the vibratory rolling area shows that coral sand foundation is not easily affected by surface water changes in terms of deformation properties. The research results can be used as reference in guiding the foundation treatment of reclaimed coral sand foundation and similar projects.
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    Ecological Operation Scheme of Artificial River-communicating Lakes in Non-flood Period
    CHAI Zhao-hui, YAO Shi-ming, LIU Tong-huan, LIU Si-sheng
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 28-33.   DOI: 10.11988/ckyyb.20190276
    Abstract26)      PDF(pc) (4035KB)(129)       Save
    Except from Poyang Lake and Dongting Lake, river-communicating lakes in the middle and lower reaches of the Yangtze River connect with the Yangtze River by culverts and sluices in general. The water quality of such lakes is inferior on account of the weak water exchange capacity, especially in dry season. Taking Huayang river-lake group as an example, we studied the feasibility of ecological operation and specific plans in non-flood period via data analysis, field investigation and numerical simulation. Results reveal that the concentrations of TN and TP decrease with the rising of water level; but such tendency attenuates when water level exceeds a certain value (13.5 m). The annual mean water level of lake group in late September is higher than the current controlled water level in non-flood period, indicating that it is feasible to use Huayang and Yangwan sluices for ecological regulation in non-flood period. In line with the current dispatching mode, the relation between rivers and lakes, the flood control security and the water environment improvement as well as the simulated results, we obtained the specific plan of ecological operation for Huayang river-lake group in non-flood season: using Yangwan sluice and Huayang sluice to control the water level in the lake area at 13 m in October-December,12.5 m in January-February,and 11.8 m in March-April.
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    Influence of Arc-shaped Short Navigation Wall on Flow Structure in Downstream Approach Channel of Shiplock
    WU Yue, YANG Xiao-li, LI Yu, HU Cheng, YANG Lin
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 81-84,93.   DOI: 10.11988/ckyyb.20190269
    Abstract26)      PDF(pc) (2946KB)(77)       Save
    The influence of changing the length of straight navigation wall on the approach channel downstream of shiplock in the presence of varied downstream water depth is investigated via physical model experiments together with theoretical analysis. On this basis, the influence of adding arc-shaped short navigation wall on flow structure is also examined. Increasing the length of straight navigation wall is beneficial to improving the navigation condition in the entrance area of the approach channel; after reaching a certain length, however, such improvement weakens. Arc-shaped short navigation wall has a good effect on improving the flow structure in the protected area of the downstream approach channel. Small longitudinal parameter “ a” and larger lateral parameter “ b” have better effect; but the opening angle should not be too large.
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    Ecological Flow Calculation and Ecological Operation of SmallHydropower Based on Modified Flow Duration Curve Method
    LIU Shu-feng, CHEN Ji-chen, GUAN Shuai
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (8): 29-34.   DOI: 10.11988/ckyyb.20190462
    Abstract26)      PDF(pc) (4092KB)(116)       Save
    The water storage and power generation of small hydropower on small and medium-sized rivers not only brings about economic benefits but also affects the environment. The ecological flow calculation and ecological operation of small hydropower are particularly important to refrain from dehydration in the downstream. With Hengxi Hydropower Station on Yangxi River as a case study, we first of all calculate the runoff according to the relation between rainfall and runoff depth, and further calculate the ecological flow of wet year, flat year, and dry year respectively using the modified flow duration curve (FDC) method. Subsequently we calculate the ecological operation in consideration of ecological flow, power generation, and irrigation. Results reveal that we could accurately calculate the runoff of Hengxi Hydropower Station by using the relationship between rainfall and runoff depth. In the absence of operation, the inflow of Hengxi Hydropower Station could not fully meet the requirements of ecological flow calculated by the modified FDC method at each level year. The modified FDC method is applicable and rational. After ecological operation, the dam-crossing discharge of Hengxi Hydropower Station could meet the demand of aquatic ecology and maximize the benefit of power generation. The research results offer reference for promoting the sustainable development of hydropower, balancing the benefits of power generation and ecology, as well as the healthy management of small and medium-sized rivers.
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    Impact of Reservoir Construction on Water andSediment Transport in Minjiang River Basin
    LÜ Chao-nan, JIN Zhong-wu, LIN Mu-song, LI Qiu-li, WANG Yu-xuan
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (8): 9-15.   DOI: 10.11988/ckyyb.20190573
    Abstract25)      PDF(pc) (5231KB)(135)       Save
    As an important tributary of the upper Yangtze River, Minjiang River provides a pivotal support for the social economic development in western Sichuan and Chengdu plain. The overall hydropower development in the Minjiang River basin took place slightly later than that in other major tributaries of the Yangtze River. In recent years, reservoir construction project increases unceasingly in the Minjiang River basin, giving rise to variations in the water and sediment condition. In this paper, the characteristics of reservoir construction and water-sediment transport as well as their interrelations are preliminary examined according to flow-sediment process lines and accumulative runoff-sediment load curves based on measured data. Results demonstrated that the number of reservoirs and the total storage capacity have surged since 1970 and 2005, respectively. Reservoirs are constructed from the mainstream to tributaries, with the number of reservoirs under construction declining while high dams and large reservoirs increasing. As dam construction technology improves, earth dam which is easy to construct is gradually changed into other dam types with high difficulty. Moreover, due to the enhancement of reservoirs’ regulation ability and sediment holding function, the runoff and sediment transport in main flood season of the basin have been flattening. Annual runoff and annual sediment transport both saw a downward trend after 1990, of which the annual sediment transport has been decreasing more obviously. Recently, the change of annual sediment transport volume at Gaochang station is in a negative correlation with reservoir construction. Such correlation intensifies with the further increase in the total capacity of reservoir in Minjiang River basin, and is more evident in flood season.
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    Experimental Study on Thermal Conductivity of Red Clay in Drying Process
    CHEN Bo, YAN Rong-tao, LIANG Wei-yun, TIAN Hui-hui, WEI Chang-fu
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (7): 140-146.   DOI: 10.11988/ckyyb.20190328
    Abstract25)      PDF(pc) (4691KB)(89)       Save
    The dynamic change in the three-phase composition of rock and soil in natural environment poses difficulty to the accurate test of thermal conductivity of soil. The heat transfer property of soil can be indirectly obtained through the thermal conductivity dryout curve (TCDC). In this research, the change rule of thermal conductivity of Guilin red clay in drying process was examined by using pressure plate and KD2 Pro soil thermal properties analyzer. Before the matric suction reached the air entry value, the saturation of soil remained unchanged, and the thermal conductivity of soil specimens with varied dry density increased slightly; in this stage, thermal conductivity was mainly related with the change of soil density caused by the change of suction. When matric suction exceeded the air entry value, the thermal conductivity gradually decreased with the reduction of saturation degree; at this stage, moisture content was the main factor affecting thermal conductivity. Based upon the experimental results, Lu's model and William's model were employed to fit the thermal conductivity curve of red clay in the drying process. Both models have good fitting results, hence can be used to simulate the change of thermal conductivity in red clay in drying process.
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    Lower Bound Limit Element Analysis on Bearing Capacity of Pile Foundation above Karst Caves
    LIANG Guan-ting, DENG Li-ming, XIAO Ming-zhao, XIAO Kai-qian, HE Lin
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 94-99.   DOI: 10.11988/ckyyb.20190145
    Abstract25)      PDF(pc) (3953KB)(100)       Save
    The procedures of calculating the limit bearing capacity of pile foundation above karst caves are provided in this paper based on MatLab using the theorem of the lower bound solution with finite element method. A plain strain model in no consideration of 3D space effect is built with the rock mass material assumed to obeying the Mohr-Coulomb criterion with plastic associated flow rule. A dimensionless parameter N is defined to describe the effect of different parameters on the bearing capacity of pile foundation. According to the position relation between piles and karst caves, the variation of limit bearing capacity of pile foundation in six different cases are examined in detail. The influences of rock-socketed pile depth h r, self-weight q s of overlying soil, and diameter D of karst caves on the bearing capacity of pile foundation are also investigated. Results reveal that the limit bearing capacity of pile foundation increases with the increase of h r, but decreases with increasing of D, while the influence of q s is negligible. In addition, the failure modes of pile foundation in different cases are also analyzed. The computation method in this paper is verified correct through two examples in the presence and in the absence of karst caves.
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    Effect of Subway Train Load on Cross-river Tunnel Lining Segments under Different Water Levels
    ZHANG Zhi-hua, AN Zhi-wei, ZHANG Xie-dong, LUO Lü-qing
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 115-119.   DOI: 10.11988/ckyyb.20190182
    Abstract25)      PDF(pc) (6690KB)(82)       Save
    The water level difference between dry season and flood season in Yangtze River basin amounts to over ten meters, which exerts an unneglectable impact on the stability of cross-river tunnel. Studying the stability performance of cross-river tunnel during subway train operation under water level fluctuation is an urgent task. In this paper, a cross-river tunnel model is built using the discrete element method. Microparameters of the tunnel are first calibrated based on triaxial test. A two-dimensional subway train load is adopted to execute dynamic load on the tunnel. Particle acceleration, radial and hoop stresses of the tunnel lining are considered as parameters to analyze the dynamic characteristics of the tunnel lining segments under different water levels. Results show that the tensile and compressive stresses of the lining segments under flood level are four times larger than those under normal water level, and are still smaller than the tensile strength. The average value of particle vibration acceleration reflecting the influence of subway train load on the lining under normal water level is 150 times larger than that under flood level. Therefore, during train operation, the inspection and maintenance of lining segments should be strengthened no matter in dry or flood season.
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    Vegetation Coverage Dynamics and Its Response to Climate Factors in the Guanzhong Basin
    ZHAO Yu
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 49-54.   DOI: 10.11988/ckyyb.20191006
    Abstract25)      PDF(pc) (4927KB)(98)       Save
    In association with MODIS vegetation index and meteorological data, the temporal and spatial distribution characteristics of vegetation cover in the Guanzhong Basin were analyzed via trend analysis and geostatistical analysis. The response of vegetation coverage to climate change in the study area was also revealed using spatial analysis method based on pixel. Results unveil that in terms of annual variation, the vegetation cover of the Guanzhong Basin shows a fluctuating upward trend, with an annual growth rate of 0.006 1 a -1; in terms of intro-annual variation, the vegetation cover of the Guanzhong Basin fluctuates significantly during the year, showing a unimodal curve. On the other hand, from the aspect of spatial distribution, the vegetation coverage is of obvious spatial heterogeneity. In annual scale, the vegetation coverage in the Guanzhong Basin is insignificantly positively correlated with rainfall and temperature; in monthly scale, the vegetation coverage is significantly correlated with monthly rainfall and monthly temperature. Such significant positive correlations indicate that seasonal fluctuations in hydrothermal factors have a greater impact on vegetation growth in the study area. The research findings offer scientific basis for ecological construction and environmental protection in arid and semi-arid regions.
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    Research and Application of Levee Road Reconstruction Technology
    HU Xiao-hong, DENG Yue-sheng
    Journal of Yangtze River Scientific Research Institute    2020, 37 (12): 67-71.   DOI: 10.11988/ckyyb.20201037
    Abstract25)      PDF(pc) (4050KB)(17)       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.
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    Optimizing Joint Dispatching of Xiluodu-Xiangjiaba Cascade Reservoirs in Consideration of Appropriate Downstream Ecological Flow in Storage Period
    CAI Zhuo-sen, DAI Ling-quan, LIU Hai-bo, DAI Hui-chao, TANG Zheng-yang, WANG Yu
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (9): 31-38.   DOI: 10.11988/ckyyb.20190622
    Abstract24)      PDF(pc) (5531KB)(136)       Save
    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.
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    Rapid Measurement of Advection-Dispersion-Adsorption Parameters of Heavy Metals by Soil Column Test
    YANG Kong-li, ZHAN Liang-tong, CHEN Cheng, XIE Hai-jian
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 120-126.   DOI: 10.11988/ckyyb.20190054
    Abstract24)      PDF(pc) (5143KB)(94)       Save
    The advection-dispersion-adsorption parameters of heavy metals are crucial for evaluating the service performance of barrier systems. Efficient and reliable method to test these parameters systematically is still in lack at present. In order to obtain the advection-dispersion-adsorption parameters of heavy metal ions with less experimental quantities in a shorter test time, the soil column test using Pb 2+ as a representative heavy metal ion was carried out in soil-bentonite. Results showed that the retardation factor of Pb 2+ decreased from 13 to 11 when the flow rate increased from 0 m/s to 1.59×10 -7 m/s, which was consistent with the law that the larger the flow rate, the smaller the retardation factor. The advection-dispersion-adsorption parameters of Pb 2+ obtained by this method were in good agreement with the typical values reported in previous literature, which proved the validity of this method. This method reduced the number of tests, improved the efficiency of parameter acquisition by which the test results were also more reliable by means of single parameter decoupling.
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    Comprehensive Reliability Analysis of Deformation Induced by Shield Tunneling Considering Spatial Variability of Soil Parameters
    LI Jian-bin, CHEN Jian
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 127-133.   DOI: 10.11988/ckyyb.20190149
    Abstract24)      PDF(pc) (4953KB)(85)       Save
    Stochastic calculations, by combining the random field theory with the finite difference analysis and Monte Carlo simulation, are used to conduct reliability analysis on the surrounding soil deformation induced by twin tunneling in multi-layer soils considering the spatial variability of soil parameters. The effects of scales of fluctuation (SOF) of Young’s modulus in both vertical and horizontal directions on deformation reliability index are investigated and discussed in detail. Results demonstrate that the reliability index of maximum deformation (surface settlement, vault settlement, and surrounding rock convergence) obtained by stochastic analysis decreases with the increase of SOF, and the comprehensive reliability index of deformation increases with the increase of allowable value of deformation. Additionally, the entropy weight coefficients of deformation indices are objectively determined by using the entropy theory. Combining the reliability design method and the engineering risk analysis theory, the comprehensive reliability of deformation is analyzed, and the deformation control index system of shield tunnel suitable for Xiamen area is put forward.
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    A Strength Criterion of Coarse Granular Materials under Three-dimensional Stress State
    JIANG Jing-shan, ZUO Yong-zhen, CHENG Zhan-lin, GAO Pan, CHEN Jian
    JOURNAL OF YANGTZE RIVER SCIENTIFIC RESEARCH INSTI    2020, 37 (6): 100-107,114.   DOI: 10.11988/ckyyb.20190150
    Abstract24)      PDF(pc) (7554KB)(77)       Save
    The intermediate principal stress has an important effect on the strength of coarse granular materials. However, the large-scale triaxial tests commonly used in strength study does not consider the effect of intermediate principal stress on the strength of coarse granular materials. Large-scale true triaxial tests under isotropic consolidation and proportional loading conditions were conducted to investigate the strength properties of coarse granular materials under three-dimensional stress states. Test results show that the peak value of the difference between major and minor principal stress of coarse granular material increases with the increasing of the coefficient ( b) of intermediate principal stress, especially when b increases from 0 to 0.25 the peak value of the difference between major and minor principal stress increases nearly 50% compared to strength under axisymmetric triaxial stress state. Lade-Duncan failure criterion well describes the variation trend of internal friction angle for coarse granular materials; but overestimates the internal friction angle. SMP failure criterion commendably depicts the numerical value of internal friction angle when b increases from 0 to 0.25; when b is larger than 0.25, however, the results of SMP criterion decrease with the further increasing of b, which underestimates the internal friction angle. In view of this, a one-parameter composite strength criterion combining Lade-Duncan criterion and SMP criterion was proposed based on test results. The proposed criterion well reflects the numerical value and variation trend of the strength of coarse granular materials. The proposed strength criterion is shown as a triangular conical surface in three-dimensional principal stress space. The strength and triangular conical surface are small and the cone angle tends to be circle when the internal friction angle under axisymmetric stress state is small; with the increasing of internal friction angle, the strength and triangular conical surface gradually become larger and the cone angle tends to be triangular.
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