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01 November 2018, Volume 35 Issue 11
    

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    SPECIAL CONTRIBUTION
  • ZHU Jie-bing, WANG Xiao-wei
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 1-6. https://doi.org/10.11988/ckyyb.20170898
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Since prestressed anchorage structures in high slope are surrounded by complicated environment, the prestressed anchor cable(rod) in slope will damage or fail after long time service caused by comprehensive factors such as electrochemical corrosion, local stress, stress corrosion and others, further resulting in slope failure. Research on corrosion damage and diagnosis of prestressed anchor structures are of great significance. In this paper, the main research findings and advances of prestressed anchorage structures in China and abroad are reviewed from four aspects: corrosion damage mechanism and influential factors of prestressed anchorage structure, non-uniform corrosion behavior, deterioration law under corrosion condition, and corrosion assessment and health diagnosis. The trend and prospect of durability research are also discussed from the above four aspects.
  • RIVER-LAKE SEDIMENTATION AND REGULATION
  • LUAN Hua-long, LIU Tong-huan, HUANG Wei-dong
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 7-12. https://doi.org/10.11988/ckyyb.20180193
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    With Zhenjiang-Yangzhou reach in the downstream Yangtze River as study area, the morphological responses and trends of central bar channels to varying water and sediment discharge are investigated based on bathymetric data. Results indicate that: (1) In the presence of low incoming sediment, the branching channels of Shiye sanbar and Hechang sandbar experienced overall erosion and unidirectional deepening especially after 2010, while the middle bars are relatively stable. (2) The variations of water diversion ratios suggested that the Shiye sandbar is dominated by main channel development and secondary channel shrinkage, while Hechang sandbar is on the contrary. Recent regulation projects have effectively retrained the unidirectional change of branching pattern. (3) Channel erosion and deepening would continue under low sediment discharge in the future, leading to high risk of local bank collapse. Systematic monitoring and forecasting of bank failures are advised, particularly for several unprotected weak banks.
  • WATER RESOURCES AND ENVIRONMENT
  • ZHAO Deng-zhong, WANG Zhao-hui, SHEN Shao-hong, TAN De-bao, XU Ping, LI Qi-jiang
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 13-19. https://doi.org/10.11988/ckyyb.20170575
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    Consecutive field investigations and observations were carried out over the Tibetan Plateau from 2014 to 2016 in order to obtain the temporal and spatial distribution of carbon in water from typical high-altitude rivers and lakes. Water from typical rivers, lakes and ice points were sampled to be analyzed using the vario TOC analyzer from German Elementar corporation in our laboratory. The total carbon concentration, total inorganic carbon concentration and total dissolved organic carbon concentration were obtained. Preliminary results show that inorganic carbon is the major form whereas organic carbon is the auxiliary form of carbon in water from typical rivers and lakes in the Tibetan Plateau and source region of three rivers, namely the Changjiang River, the Yellow River, and the Lancang River. The averaged concentration of total carbon in water from typical rivers and lakes over the source region of Changjiang River, Yellow River and Lancang River source area was 62.46 mg/L, 32.88 mg/L, and 17.70 mg/L, respectively; while the total carbon concentration in the Dangqu River source (southern source), the Tuotuo River source (main source) and the Qumar River (northern source) was 32.90 mg/L, 36.56 mg/L, and 32.90 mg/L, respectively. Over the Tibetan Plateau, the total carbon concentration and total inorganic carbon concentration in surface water from typical lakes (403.82 mg/L and 398.35 mg/L, respectively) were much higher than those from typical rivers (17.03 mg/L and 14.56 mg/L, respectively); however, total organic carbon concentration displayed an opposite trend, with 1.24 mg/L in lakes and 2.46 mg/L in rivers. The research results are of vital importance for the climate change and water resources and eco-environmental safety in the Tibetan Plateau and the source region of the three rivers.
  • CHENG Zhong-yang, ZHANG Xing-nan, XIA Da-zhong
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 20-25. https://doi.org/10.11988/ckyyb.20170363
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    Numerical product has been an important means to improve the anticipation period of hydrological forecast. In the purpose of understanding areal rainfall forecast accuracy and error distribution of ECMWF (European Centre for Medium Range Weather Forecasts) and WRF (Weather Research and Forecasting Model) and providing scientific support for improving the robustness of flood forecast accuracy, we verified the forecast results of areal rainfall in flood season of 2016 in seven subareas of Jialing River Basin by examining indexes involving TS score, false alarm rate, point over rate, and success hit rate. Furthermore, we analyzed the relationship between the abovementioned indexes and the period of forecast validity in the subareas. Results suggest that ECMWF product and WRF product could be both applied to the sunny/rainy forecast in the study area. The forecast accuracy improves with the increase of rainfall grade, but reduces with the decrease of forecast validity period. In general, ECMWF has better forecast efficiency in the Jialing river basin.
  • DU Tao, OUYANG Shuo, LI Shuai, WANG Kun, BU Hui, YAN Lei
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 26-31. https://doi.org/10.11988/ckyyb.20180187
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    Design low-flow analysis under nonstationary conditions is a critical consideration in water resources management. The design low-flow varying from one year to the next obtained by using the time-varying moment method is hard to be applied to practical application. This paper is aimed to improve the characterization of nonstationary design low-flow under the expected number of exceedances (ENE) interpretation of return period by employing meteorological covariates in the nonstationary frequency analysis. The method of using time as the only covariate is also applied for comparison. Both methods are applied to the annual minimum monthly streamflow series of the Weihe River, China. Results demonstrate that the nonstationary design low-flow results of both methods are significantly different from the stationary case. The nonstationary design low-flow result using temperature and precipitation as covariates is found more reasonable and advisable than that of the case using time as covariate. It is concluded that nonstationary design low-flow analysis can be helpful to water resources management during dry seasons exacerbated by climate change.
  • LI Ke-guo, LI Zhong-yuan
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 32-36. https://doi.org/10.11988/ckyyb.20170569
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    As the first largest level-1 tributary of Nujiang River in Yunnan Province, Mengboluo River is featured with complex rainfall and runoff. The annual runoff series in Mengboluo River are obtained through restoration, interpolating and supplementing the observed data of runoff at seven hydrologic stations in the watershed. Statistical parameters are analyzed, and the linear relation with one variable, exponential relation with one variable, exponential relation with two variables are established between mean annual runoff of multiple years and drainage area of each hydrologic station, mean annual runoff of multiple years and mean annual precipitation of drainage area. Simulation and comparison are carried out from overall and regional perspectives. The simulation error of different relations from overall perspective ranges from ±19.6%-±11.5%, and the simulation error of exponential relation with two variables from regional perspective is within ±2.8%, indicating close relations between runoff and drainage area, and runoff and precipitation, which matches the hydrologic characteristics of Mengboluo River watershed. The method in the present paper could be promoted for plateau mountain area.
  • WATER-SOIL CONSERVATION AND ECO-CONSTRUCTION
  • XUE Tian-han, ZHANG Qi, GUO Zi-jian
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 37-40. https://doi.org/10.11988/ckyyb.20170552
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    To explore the dynamic changing features of land use in harbor area driven by port construction, the land use patterns in Dagushan area of Dalian in 1993, 2000, 2007, and 2014 were extracted as a case study. The ecosystem service values of different terms are assessed. In the case study, the influential factors of the land use and ecosystem service value changes are analyzed, and the spatial patterns of port-dominated coastal regions are summarized. Results show that the increase of construction land is basically consistent with the speed of port development, and the construction land has been the largest land use type in Dagushan area. Meanwhile, the proportion of ecological land decreases significantly, which results in the insufficient space for construction expansion and the great pressure on ecological environment. It is suggested that the protection of ecological land, in particular, forest land and water body shall be strengthened.
  • FLOOD PREVENTION AND DISASTER REDUCTION
  • ZHANG Jing, FENG Bao-fei, LUO Shi-bing
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 41-45. https://doi.org/10.11988/ckyyb.20171258
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    The “No.1 flood in 2017” is a regional big flood in the midstream of Changjiang River. Reservoir groups in the upper and middle reaches were dispatched jointly to cope with the severe flood situation. The discharge of Three Gorges reservoir reduced from 27 300 m3/s to 8 000 m3/s, which had been the largest compensation ever. The compensation guaranteed that the water level at Lianhuatang station did not exceed the critical stage for flood diversion. Flood forecast for Lianhuatang station is crucial for the determination of joint dispatching time and dispatching effect. In this paper we introduce the flood forecast method for Lianhuatang station, and analyze the forecast result and the causes of errors. In addition, we also summarize the difficult points in flood forecast in the aim of providing more scientific technical support for the flood prevention and decision-making.
  • HU Zi-chen, LIU Shu-guang, ZHONG Gui-hui, WEI Qian-kun
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 46-51. https://doi.org/10.11988/ckyyb.20170570
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    Flood and waterlogging disasters in plain river network region in recent years have brought about severe damage to people's lives and property safety. Rainfall is the key factor causing flood disasters in the region, of which the most typical ones are plum rain and typhoon rainstorm. The flood generating mechanism of plum rain and typhoon rainstorm varies because of different temporal distribution. In the aim of investigating the influence of rainfall's temporal variation on flood process, a 1D- and 2D-coupled hydrodynamic model of Wuchengxiyu hydraulic district of Taihu Lake drainage basin was built with MIKE 11 and MIKE 21. The model was calibrated and validated by several measured flood events. Numerical simulation of flood processes under different design conditions in the study area was conducted. The influences of magnitude, duration and temporal variation of rainfall on flood process were examined. Results suggest that the temporal distribution of rainfall has apparent influence on flood in plain river network. Rainfall of long duration is sensitive to the delay of rainfall peak, while rainfall of short duration is largely affected by the time variance coefficient. Meanwhile, rainfall amount has evident impact on both long-duration and short-duration rainfall.
  • CHEN Ping, JI Xiao-guang, XU Hao-mei
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 52-56. https://doi.org/10.11988/ckyyb.20170409
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    Flood risk map is a vital scientific basis for flood risk management as it reflects the flood features, geographic elements and socio-economic information in the submerged area comprehensively and directly. To strengthen the safety construction planning of Nanli river area, a hydrodynamic model coupling 1D and 2D models of the river channel and both banks of Nan liriver is established by using MIKE software. The model test result is verified by historical flood data in August of 1996 in the Haihe river basin. The coupled model is used to simulate the flood routine process for 100-year event flood. Results validate that the established model could be used as a basis for flood risk analysis of Nanli river, and provide reference for the safety construction around the Nanli river.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • LI Gang, XIAO Fan, LIU Hao, HU Ming-bing, ZHAO Kui
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 57-62. https://doi.org/10.11988/ckyyb.20170008
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    The unique advantages of acoustic emission (AE) technology in signal collection and positioning of slope collapse failure are expounded by analyzing and summarizing existing slope monitoring technologies. By detailing the development and current situation of AE slope monitoring technology, the influential factors of AE slope monitoring are put forward. Case analysis demonstrates that AE technology could not only locate slip surface, but also can be used to judge the failure state by classifying the acoustic emission parameters into different damage levels. In addition, problems in waveguide, coupling agent, and sensor arrangement are pointed out. The selection of waveguide and coupling materials, the arrangement of sensors, and the correlation between acoustic emission from coupling material and surrounding rock mass are to be further studied and explored.
  • LI Qiu-quan
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 63-68. https://doi.org/10.11988/ckyyb.20170446
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    The stability of surrounding rock of tunnel can be effectively identified by deformation prediction, which is a crucial basis for informatized tunnel construction. An improved prediction method combining local weights and global weights is proposed to improve traditional methods. The proposed method is simple, practical, and also reflects the impacts of sample data and node length on combinatorial weights. Meanwhile, ideas of cumulative superposition and multiplicative superposition are put forward in consideration of the influences of local and global factors on the combinatorial weights. Engineering case study verifies that the proposed combinatorial forecasting model is of higher prediction accuracy than traditional forecasting model, with the relative error less than 2%; in addition, multiplicative superposition is of better effect, higher accuracy and stability than cumulative superposition.
  • HUO Run-ke, LI Shu-guang, DU Li-hui, YANG Jun-qing, HAN Fei
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 69-75. https://doi.org/10.11988/ckyyb.20170536
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    To better analyze the effect of carbon fiber reinforcement for Nanwa tunnel as a case study, the reinforcement plans with different disease positions of tunnel lining and crack depths are simulated in ANSYS, and corresponding construction techniques and countermeasures are put forward. Analysis finds that only in plan 1 (when cracks of different depths exist on tunnel vault) and plan 2 (when cracks of different depths exist on both tunnel vault and sidewall), the deformation of lining increases obviously with the increase of crack depth before carbon fiber reinforcement, with the maximum displacement 5.81 mm in plan 1 at the center of the inverted arch and the maximum stress 18.80 MPa located in the foot of the arch. After carbon fiber reinforcement, the deformation of lining is greatly reduced, with the maximum displacement in plan 1 cut from 5.81 mm to 3.36 mm, declining by 42.2%, and the maximum displacement in plan 2 decreasing from 6.17 mm to 3.64 mm, dwindling by 41.0%. Result demonstrates that the carbon fiber reinforcement technology has good reinforcement effect on Nanwa tunnel.
  • LI Yun-jie, TANG Ming-gao, QU Fei-xing, SHAO Shan, MA Xu, LUO Jian, YANG He
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 76-81. https://doi.org/10.11988/ckyyb.20170543
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    The state of slope activity is an important indicator reflecting the hazard level of landslide. Previous assessments of landslide are focused on the mechanism of landslide by selecting reasonable indicators to quantify the degree of hazard. However, such assessments take no consideration of the evolution process and activity states of slope, which could not precisely depict the risk level of landslide. In view of this, a risk assessment method for large landslide in consideration of slope activity state is proposed. The risk value of large landslide is calculated by superpositioning the geological conditions and the activity state in GIS. With the landslide of Xishan Village as an example, geological factors inclusive of slope gradient, slope height, curvature, slope direction, stratigraphic lithology, fault, river, road, and vegetation coverage are selected to construct an assessment model with fracture development degree and monitored deformation to describe the activity state of slope. Verification results show that the degree of overlapping between highly active area and highly risky area reaches 96.03%, which indicates that the proposed risk assessment model is reasonable and effective.
  • HYDRAULICS
  • ZHANG Lei, SHE Xiao-jian, CUI Zheng
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 82-85. https://doi.org/10.11988/ckyyb.20170612
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    The New Port of Qinzhou Bay is located in the water area of 100 000 tons east channel and 300 000 tons oil wharf which will be affected by the New Port plan in terms of channel flow and cross flow. The tidal current in the whole Qinzhou Bay was simulated via physical model test in an attempt to analyze the channel flow and cross flow in the new port plan. Test results revealed that among the three plans, velocity change in plan 1# is the largest. Flow velocity in the channel of 300 000 tons oil wharf varies within 0.10 m/s; flow velocity in the east channel of west shoreline increases within 0.20 m/s. Since the main currents in the New Port concentrate in the 100 000 tons east channel, the influence on the flow and cross flow in 100 000 tons east channel will be larger than those in the 300 000 tons oil wharf channel. In plan 3# in which the shoreline is smoothed, cross flow in the east channel reduced apparently. Therefore, the encircling plan is recommended.
  • HU Zhi-yi, LI Yong-ye, HUANG Ying-bin
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 86-90. https://doi.org/10.11988/ckyyb.20170546
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    As a new type of pipeline hydrotransport, capsule hydrotransport is more energy-saving, highly efficient, and environmental-friendly compared with traditional transmission. In order to optimize the structural parameters of cylindrical capsule and promote capsule hydrotransport, we investigate the hydraulic characteristics of cylindrical capsules conveyed in pressurized pipeline under different loads. We find that: 1) the mean velocity of capsule increases with the rising of load; 2) water pressure in the pipeline reduces along the way, and the load of capsule does not affect this trend; 3) on a given section, pressure magnifies with the increment of load; 4) unit energy consumption also rises with the augment of load; 5) the transmission rate of capsule increases until the load reaches 4 N, and then decays. The conclusions of this paper offer theoretical basis for optimizing the structural parameters of cylindrical capsule and applying capsules in hydrotransport.
  • ROCK-SOIL ENGINEERING
  • GU Shuan-cheng, HU Chun-hui, HUANG Rong-bin
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 91-95. https://doi.org/10.11988/ckyyb.20180839
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    In this paper, a new creep test method for loess is proposed based on improved one-dimensional consolidation instrument. Boreholes are made on cylindrical loess specimens (height 6.0 cm and diameter 6.18 cm) to facilitate artificial damage space. Creep tests are conducted under different vertical loads (125 kPa, 175 kPa, 225 kPa, and 275 kPa) at different moisture contents (23.8%, 20.1% and 15.5%). Reliable test data are obtained by loading separately, and the changes of loess creep stages are observed by placing a camera probe in the borehole. By using this method, three stages of creep, namely, attenuation, stable, and acceleration, can be obtained rather than only attenuation and stable stages due to the limit of ring knife in WG-type consolidation instrument. The proposed method is of simple operation, few influential factors, and strong reliability, hence can be used for directly observing the changes of loess creep.
  • ZHANG Ji-xun, YU Shu-yang, HU Nan-xiong, YANG Zhao-bing
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 96-100. https://doi.org/10.11988/ckyyb.20170489
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    In an attempt to study the seepage characteristics of geomembrane dam with geomembrane defects and the stability of upstream dam slope under rapid drawdown of reservoir level,a finite element model of damaged geomembrane was established to analyze the seepage factors and stability of dam with different damage parts and sizes of the geomembrane. Results revealed that the higher the damaged position of geomembrane and the larger the size, the higher the phreatic line and the greater the leakage; the impact of damage size was obviously smaller than that of damage position. The phreatic line declined abruptly when the water level of the reservoir reduced to the height of the geomembrane. The initial stability safety factor decreased with the increase of the height and size of the defect position. In general, the safety factor decreased first and then stabilized, yet with a sudden rise when water level reached the geomembrane defect. The results provide a reference for the stability evaluation and treatment of geomembrane dam.
  • DING Lu-qiang, LI Da-yong, CHEN Fu-quan
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 101-106. https://doi.org/10.11988/ckyyb.20170474
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    As pivotal technical indicators in designing geosynthetic and reinforced soil structures, the properties of interface between soil and reinforcement reveal the reinforcement mechanism of geosynthetics. In the present study, the influences of shear rate, vertical stress, and geogrid's mesh size on the performance of interface between geogrid and saturated fine sand were investigated using GDS interface shear apparatus.Results revealed that 1) Small shear rate (≤1.0 mm/min) had only slight impact on the shear strength of interface. 2) When shear rate ranged between 1.0 and 10 mm/min, the shear strength of interface increased initially but decreased afterwards with the growth of shear rate. 3) The rising of vertical stress enhanced the shear strength of interface by intensifying the interlocking effect of geogrid on soil particles and limiting the shear displacement of soil particles. 4) When shear rate was 1.0 mm/min and vertical stress was small (50-100 kPa), geogrid with small mesh size was more effective in reinforcement; when shear rate was 0.1 mm/min and vertical stress was large (200-300 kPa), geogrid with large mesh size was of better reinforcement effect. The results can facilitate the application of geogrids in reinforced soil.
  • HE Tao, CAO Ya-xian
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 107-111. https://doi.org/10.11988/ckyyb.20170433
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    Research on the heat-force-liquid coupling of rock is extremely important for deep mining engineering, nuclear waste storage, geothermal resources exploitation and utilization and other engineering fields. In an attempt to study the permeability evolution regularity of rock after high temperature, the mechanical properties of rock mass undergone thermal fracture treatment at different temperatures were analyzed in terms of strength and permeability through triaxial loading test. Rock samples collected from a mining well in Tarim were taken as research objects. Results manifested that:(1)In the initial stage of loading, the climbing of confining pressure led to lower permeability;in the mid-stage, permeability increased slowly; in the later stage of loading, permeability increased dramatically. (2) The permeability of rock increased in positive exponential relation with the rising of temperature. (3) The thermal expansion of rock was unapparent below a certain temperature, while thermal expansion induced by higher temperature would significantly damage rock structure, mitigating the increasing of elastic modulus and strength with the rise of temperature. (4) In line with the theory of thermodynamics, the rock fracture caused by thermal stress under varying temperature was deduced, and the model of permeability varying with temperature was obtained. The results offer reference for the study of multi-field coupling under high temperature.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • JING Yue-ling, WANG Yang-yang
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 112-116. https://doi.org/10.11988/ckyyb.20170331
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    A three-dimension finite element model of a power station at dam toe is built in this paper. The main structures include dam, foundation, powerhouse at dam toe, roof net, and simplified bearing model. Three kinds of bearings, namely, laminated rubber bearing supported with anchor bolt, lead rubber bearing, and hinge support, are compared to find their influence on the upper structure under earthquake action. Result reveals that hinge support is unfavorable for seismic reduction with the shortest natural vibration period and the largest seismic response; also, the maximum displacement of node pairs on the upstream and downstream side of powerhouse are higher than that in the case of lead rubber bearing by 31.74% and 44.5%, respectively. Lead rubber bearing has good ability of releasing support force under earthquake due to good energy absorption effect and better adaptation to shear deformation; moreover, the first principal stress of node pairs on upstream and downstream side of the powerhouse under earthquake is the lowest among the three cases. In conclusion, the lead rubber bearing is recommended.
  • LIU Jian-xun
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 117-121. https://doi.org/10.11988/ckyyb.20170501
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    To obtain the variation law of the rebound strength of concrete pier and the strength of test block under different curing methods in Gobi region, we tested and analyzed the properties of the raw materials firstly. In subsequence, we tested the strength of concrete piers and test blocks cured by different methods (standard curing, air curing, geotextile maintenance, and rubber-plastic board maintenance) in Gobi region at different ages (3 d, 5 d, 7 d, 14 d, 28 d, and 56 d). Formula fitting and verification results of rebound strength and test block strength show that: (1) The compressive strength, tensile strength, and ratio of tensile strength to compressive strength increased gradually following the order of air curing, geotextile maintenance, rubber-plastic board maintenance, and standard curing. (2) The rebound strength of concrete pier under different curing conditions in Gobi region is smaller than the strength of test block, with the difference between 3-9 MPa, which reduces along with the increase of age. (3) When the thermal insulation effect of curing method improves, the difference between rebound strength and block strength of concrete in Gobi region shrinks. (4) The calculation formulae of concrete's rebound strength under different curing conditions in Gobi region and the strength of test block are proposed and verified to be of small error, hence could be used as reference for strength calculation.
  • XIAO Jian-qiang, XIA Xiao-zhou
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 122-125. https://doi.org/10.11988/ckyyb.20170611
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    Lightweight aggregate concrete is considered as a three-phase composite material composed of matrix cement mortar, intercalated aggregate and interface layer. In line with the homogenization theory in mesoscopic mechanics, the compressive strength of light aggregate concrete is analyzed via numerical simulation. The influences of ratio of aggregate's Young's modulus and mortar matrix's Young's modulus and aggregate's volume fraction on the ratio of concrete's compressive strength to aggregate's compressive strength are examined. Result reveals that there exists a critical value of Young's modulus ratio, below which the compression strength of concrete is dominated by the compressive strength of interface, and above this value the compression strength of concrete is controlled by the compressive strength of aggregate.
  • KUANG Chu-feng, ZHANG Gui-jin, LIU Jie, LIU Yun-gui, YANG Ju
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 126-132. https://doi.org/10.11988/ckyyb.20170500
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    The grouting of water-rich karst macrovoid formation is a difficult problem in foundation treatment as the filling, seepage-proofing and reinforcement requirements are high. Commonly used mortar is of poor water-dilution resistance, while cement paste-slurry is of weak controllability and serious waste. In view of the respective advantages of paste-slurry and sand, a novel controllable cement-sand paste-slurry which is suitable for water-rich Karst macrovoid formation is proposed in this paper via long-term indoor test with large sample. Results demonstrate that the cement sand paste-slurry is of large viscosity and initial yield stress with the bleeding rate declining to 0%-3%, the minimum fluidity reaching 10-20 cm, and the setting time adjustable in 2-30 min. In the flow rate of 0.4-0.6 m/s, the slurry retention rate reaches 85% after water scouring and dilution, stone rate is nearly 100%, and the 28 d compressive strength reaches about 10 MPa. Moreover, the cost of the cement-sand paste-slurry slurry is equivalent to ordinary cement paste-slurry; the slurry also has social benefits such as environmental protection. Although cement-sand paste-slurry is the preferred material for the seepage-proofing and reinforcement of water-rich karst macrovoid formation, the pumpability should receive enough attention in practical engineering application.
  • WATER CONSERVANCY ECONOMICS
  • GAO Xin-wen, ZHOU Jian-zhong, XIAO Xiao-gang, ZHANG Sheng, MO Li, JIANG Zhi-qiang, FENG Zhong-kai
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 133-139. https://doi.org/10.11988/ckyyb.20171385
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    Unit commitment is a typical issue involving large-scale complicated nonlinear optimization. The difficulty of solving unit commitment increases nonlinearly with the increase of system scale. Effectively solving this problem has always been a hotspot and difficulty in power system research. In this paper, a Binary Harmony Search Particle Swarm Optimization (BHSPSO) algorithm is proposed for unit commitment problem. Firstly, the information sharing mechanism of particle swarm optimization is incorporated into the process of learning the harmony memory of the harmony search algorithm. And then the heuristic intelligent strategy is used to deal with the complex constraints of the time series. The spinning reserve constraints are repaired according to the priority of the unit, and an "on-off-on" repair strategy is designed to deal with the constraints of minimum power-off time and power-on time, effectively improving the quality of the results obtained. The BHSPSO algorithm is applied to standard calculation examples of six systems with 10, 20, 40, 60, 80 and 100 units. The simulation results show that the proposed algorithm has advantages of simplicity, fast convergence and strong robustness. This research offers a new approach for efficient solution of unit commitment optimization problem.
  • THE 28TH NATIONAL SYMPOSIUM ON GEOTECHNICAL TESTING
  • JIANG Min-min, YANG An-lun, XIAO Zhao-ran, CHEN Gui-xiang
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 140-144. https://doi.org/10.11988/ckyyb.20180928
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    Cyclic properties of fly ash under earthquake load are crucial for the safety of stock yard and filling bodies. In this paper the cyclic deformation, cyclic pore pressure, failure mode and modulus degradation of fly ash under earthquake load were investigated via triaxial test under effective consolidation stress of 50-200 kPa and three different cyclic stress levels. The cyclic shear stress was calculated based on Seed-Idriss's equation. Results revealed that under large cyclic stress level, fly ash failed under the criterion of dual-amplitude axial strain; under medium cyclic stress level and 50 kPa consolidation stress, fly ash failed under the criterion of accumulative axial strain, while when consolidation stress exceeded 50 kPa, fly ash failed under the criterion of dual-amplitude axial strain; under low cyclic stress level, cyclic deformation failure did not occur. At the same cycle, pore pressure ratio decreased with the rising of consolidation stress; pore pressure in fly ash was far below liquefaction criterion when deformation failure occurred. Modulus of fly ash degraded rapidly under large stress level until 10 cycles; under medium cyclic stress level, the modulus degradation index decreased swiftly when cycle number was beyond critical value; degradation of modulus was very small under low cyclic stress level.
  • XU Ke1, 2, CHEN Mo-zi1, 2, GU Yao-tian1, 2, LEI Guo-hui1, 2
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 145-148. https://doi.org/10.11988/ckyyb.20180909
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    In practical situations, soils are frequently subjected to the simultaneous action of consolidation and shearing, namely, sheared under partially drained condition. To simulate this action, the triaxial compression testing method is adopted while keeping the water outlet valve open during shearing at different axial-strain rates. Partially drained shearing tests are carried out on remolded saturated kaolin specimens. The stress-strain behavior under the interactions of volumetric strain and pore-water pressure is analyzed. The test results show that under partially drained condition, the induced pore-water pressure increases and the shear strength decreases with the increase in the rate of axial strain. The critical-state line is, however, independent of the axial strain rate and the drainage condition.
  • CHEN Bao, YU Da, HU Xin, PAN Yan-min
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 149-153. https://doi.org/10.11988/ckyyb.20180926
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    The collapsibility of loess has exerted adverse impact on the stability of tower base of electric power transmission line in Henan Province.In view of this,we conducted tests on the basic physical properties and collapsibility of loess in Sanmenxia area in Henan Province in order to obtain collapsibility coefficient and evaluate collapsibility grades.Moreover,by analyzing the effects of changing vertical pressure and initial water content on loess collapsibility,we examined the relationship between collapsibility and structural strength of loess.Test results show that the relationship between vertical pressure and collapsibility coefficient is not a simply and monotonically increasing function; instead,we found intervals of vertical pressure which induces the exacerbation or weakening of collapsibility.A plastic limit of 18.6% is the dividing point on collapsibility curve which means that collapsibility weakens when initial water content is close to or over the plastic limit,or exacerbates when initial water content is smaller than that plastic limit.In addition,the relationship between water content and collapsibility coefficient is also not a simple and monotonically decreasing function where the turning point on that function would appear when initial water content equals 10% and structural strength is 200 kPa at the same time.
  • LI You-hong, GU Xiao-qiang, LIANG Fa-yun
    Journal of Changjiang River Scientific Research Institute. 2018, 35(11): 154-158. https://doi.org/10.11988/ckyyb.20180924
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    One-dimensional consolidation tests were carried out in a stress path triaxial to investigate the coefficient of lateral earth pressure K0 of saturated Toyoura sand with different densities. Bender elements for shear wave measurement were installed in the triaxial device. The shear wave velocity of sand specimens can be measured under the K0 stress state and then the small strain shear stiffness G0 of Toyoura sand can be calculated. Results demonstrated that the value of K0 decreases as the density of sand increases. Furthermore, the effects of effective mean confining pressure and density on shear modulus G0 at small strain were also investigated. Parameters A and n in the empirical equation for predicting the G0 of sand sample during the K0 stress rate were determined. Moreover, the relationship between K0 and G0 was analyzed and it was found that K0 decreases almost linearly as G0 increases.
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