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20 September 2015, Volume 32 Issue 9
    

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    RIVERLAKE SEDIMENTATION AND REGULATION
  • LIN Yun-fa
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 1-5,20. https://doi.org/10.11988/ckyyb.20140274
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To understand the scouring intensity and scope in the middle Hanjiang River, we summarized the erosion regularity up to 2005 through years of observation. In this research, regularities of recent scouring in the reach from Danjiangkou to Nianpanshan are analysed according to observation data in the downstream of Danjiangkou dam from 2005 to 2012.It’s concluded that the erosion intensity in the downstream of dam varies with the scouring time and the distance to dam. With time goes by, major erosion develops from Danjiangkou-Xiangyang reach towords the downstream. In recent years the river reach from Cuijiaying to Nianpanshan was subjected to major scouring. Due to the changes in operation mode caused by the heightening of Danjiangkou dam, it is suggested to strengthen the monitoring and analysis on the erosion in the downstream of Danjingkou dam.
  • WATER RESOURCES AND ENVIRONMENT
  • LIU Yun-lang, CHENG Sheng-gao, CAI Hui-lian, SHI Yi
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 6-13. https://doi.org/10.11988/ckyyb.20140382
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Payment for Inter-basin Water Transfer Ecosystem Services (PIBWTES) is an approach by researchers to solve the problems of environmental pollution and benefit imbalance of inter-basin water transfer project from market perspective. In the present paper we summarized the researches in terms of concept, purpose, standards, implementation mechanisms, and security system, and made a review on the research achievements. Moreover we compared the research progresses in China and abroad, and found that a preliminary theoretical system inclusive of the concept and security of PIBWTES has been formed in foreign countries although it has attracted attention only in recent years. However in China, research in this regard is still in its initial stage. Endeavors should be made in future research in the following aspects: define PIBWTES from the perspective of ecosystem characteristics and PES market features; determine the purpose in consideration of the relationship between PES and poverty alleviation; make a standard based on the spatio-temporal characteristics of market and ecological services; set PES fund for implementation; specific legislating from regional and property rights.
  • CUI Xiao-lin, LU Jian-zhong, CHEN Xiao-ling, TAO Can
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 14-20. https://doi.org/10.11988/ckyyb.20140374
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    Calibration is a focus of SWAT (Soil and Water Assessment Tool) model research in simulating water basin runoff, while validation of the model’s stability in different climatic conditions is rarely seen. Taking Fuhe river watershed in Poyang Lake water system as an example, we built a SWAT model to simulate the runoff at Lijiadu hydrological station and further validated the model’s stability in extreme climate conditions. For the validation we took the data measured in continuous wet years (1975-1977) and dry years (1963-1965), continuous high temperature years (1963-1965) and low temperature years (1969-1971). Results show that the determination coefficient R2 and efficiency coefficient ENS are both larger than 0.85 in calibration period, and larger than 0.80 in validation period (1991-1998). The model was verified to be suitable for Fuhe river watershed and stable under extreme weather conditions.
  • JU Bin, ZHANG Shuai-ting, HU Dan
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 21-25,31. https://doi.org/10.11988/ckyyb.20150019
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    According to monthly precipitation data from three meteorological stations (Fuyun, Aletai, and Habahe)
    in the Irtysh River Basin from 1962 to 2013, we employed Mann-Kendall method, Morlet wavelet analysis method, R/S analysis method, and other hydrological statistical method to analyze the characteristics and trends of precipitation variation at these stations. Results suggest that the annual precipitations at these stations all present a trend of increase, with the trend rate of 17.91mm/10a, 17.47mm/10a, and 17.37mm/10a respectively. The annual precipitation series have significant periodic variation with main oscillation cycle of 22a, 18a, 22a and characteristic time scales of alternative wet-dry years. The Hurst values indicate that the trend of increase in precipitation at these three stations will continue in the future, and the largest increment of precipitation is at Fuyun station, followed by Aletai and Habahe.
  • LI Yan-fang, YANG Kun, YANG Rong
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 26-31. https://doi.org/10.11988/ckyyb.20150084
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Land surface temperature is an important indicator of analysing the earth’s environment, and land surface emissivity is a key factor on retrieved land surface temperature from remote sensing data. In this paper according to the measured land surface temperature, we analyzed the effect of different emissivity on the retrieved land surface temperature from remote sensing data. Firstly we calculated the land surface emissivity by using NDVI threshold method and empirical formula model respectively, and then adopted a generalized single-channel method to retrieve the land surface temperature. The Landsat5 TM6 band data acquired in March 24, 2009 in Dianchi Lake watershed was taken as research example. Results show that the emissivity calculated by both NDVI threshold method and empirical formula are in significant relation with MODIS validation data, and the retrieved surface temperature has small error compared with measured temperature, in the control range. But the surface temperature retrieved from the emissivity calculated by empirical formula is abnormal in urban areas, exceeding the observed temperature by 4 ℃ -5 ℃, which does not accurately reflect the surface temperature; while the surface temperature retrieved from the emissivity calculated by NDVI threshold method is nearer to the measured surface temperature, and reflects the temperature under different land covers more accurately. Therefore, for areas with good land cover such as Dianchi Lake watershed, it is more appropriate to retrieve land surface temperature from the emissivity calculated by NDVI threshold method.
  • HE Zi-li, ZHAO Xiao-hua, YANG Jian-guo, HE Yu
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 32-36. https://doi.org/10.11988/ckyyb.20140265
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    The rural water supply in west China is facing with problems such as long transfer distance, small flow, and secondary pollution caused by long time stay of water in the regulation tank. In order to explore the impact of regulation tank made of different materials on water quality, we tested the variations of four water quality indicators (residual chlorine, pH, conductivity and dissolved oxygen) in different tanks made of concrete, tile, plastics and stainless steel, respectively. The results show that at given temperature, the attenuation coefficient of residual chlorine in concrete tank is the largest, followed by plastic, tile and stainless steel. The pH value also changes obviously: the pH value of water in concrete and tile regulation tanks shows an obvious rising trend with the increase of storage time, while in stainless steel tank the pH value increases gently, and in plastic tank the pH value does not change significantly. The water conductivity in concrete, tile and stainless steel tanks increases with time rapidly in the early stage, but the change becomes stable later. The variations of dissolved oxygen in concrete and stainless steel tanks are relatively stable, while in tile and plastic tanks, dissolved oxygen shows a trend of increasing. The effect of different tank materials on water quality and the variation of water quality with environmental factors are obtained. It could be a reference for the design, operation and management of rural water supply system.
  • LI Zhong-ping
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 37-41,46. https://doi.org/10.11988/ckyyb.20140405
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The distribution of ecological water demand of Yitong River within a year was investigated using flow duration curve method according to the historical flow data at Nong’an station and Yitong station. Nong’an Station is located in the mid-lower reaches of Yitong River, and Yitong station is in the upstream of Yitong river. Calculation results showed that the minimum ecological water demand at Nong’an station was 46.94 million m3, which accounts for 15.46% of the annual runoff; and the minimum ecological water demand at Yitong station was 3.04 million m3, taking up 4.80% of the annual runoff. Furthermore, the Tennant method and the average value of minimum monthly flow were used to estimate and verify the ecological water demand. The result obtained by Tennant method is close to the result by the flow duration curve method. The results indicate that the distribution of ecological water demand of Yitong River within a year is in correspondence with the practical water allocation, which means that the water demand is large in high flow period and small in low flow period. Through the ecological water demand, the aquatic habitats at Nong’an segment could be protected; whereas the aquatic habitats of Yitong segment have already degenerated and impoverished, and protective measures should be taken.
  • WATERSOIL CONSERVATION AND ECOCONSTRUCTION
  • CHENG Liu-san, SHI Wei-yu
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 42-46. https://doi.org/10.11988/ckyyb.20140275
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To scientifically determine the cost of eco-environmental damage is a focus and difficult issue in researches of ecological compensation. In this paper we take the transformation of paddy field into dry land (a pattern of land degradation caused by coal mine collapse) as research object, and analyse the changes of water factors (in terms of water cycle and eco-protection) from paddy field to dry land through literature review and household survey. On this basis, we introduce the concept of virtual water trade to determine the feasibility of eco-compensation standard for paddy field transferring into dry land. This research could be a reference for the eco-compensation mechanism and decision-making in coal mining collapse areas.
  • FAN Bing,LIN Mu-song,QIAN Sheng
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 47-51,75. https://doi.org/10.11988/ckyyb.20140225
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The strengthening work of submerged dike at Hechangzhou left braded channel consists of two parts: rock riprap (with nylon cage) on the dike crest and slope protection by rock blocks. Since there is no related specification or experience in determining the compensation coefficient of engineering quantity and construction technique, field tests were conducted for the construction positioning, the detailed technique of rock riprap (with nylon cage), and the compensation coefficient of engineering quantity. Through the field tests, construction positioning was determined, and according to the test results, the compensation coefficient of engineering quantity of riprap at dam crest and dam abutment is 1.2, the compensation coefficient of engineering quantity at underground dam slope is 1.5. Moreover, the calculation formula of the riprap's and nylon riprap's drift distance were derived, and in association with the field test, the riprap's and nylon riprap's drag coefficient was calculated. The research achievements have been applied to the design and construction of strengthening work of submerged dike at Hechangzhou left braded channel, and achieved expected results.
  • FENG Tao, LI Chang,HUANG Jian-wu,SHI Qian, GE Cheng-yan, WU Jiang-hua
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 52-57. https://doi.org/10.11988/ckyyb.20140259
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    Assessment on the social vulnerability to flood is of guiding importance to the disaster reduction, decision-making and early warning in flood-stricken areas. According to the socio-economic data of Jingzhou city, we established an assessment index system involving 32 indicators in terms of population, economy, employment, education, land use and housing conditions, transportation and communication, and disaster management. Through factor analysis, we determined five main factors, namely, comprehensive economy, agriculture and population, rescue condition, social security system and housing conditions. Then we calculated the score of each factor and the regional total scores of social vulnerability. Finally, these factor scores are processed by hierarchical cluster procedures and geographic information system (GIS). The social vulnerability to flood is classified into serious, medium-serious, moderate, and gentle class. Among districts in Jingzhou city, Jianli belongs to serious class, Jiangling, Gong’an, Honghu, Songzi and Shishou belong to medium-serious class, Jingzhou district belongs to moderate and Shashi district belongs to gentle class.
  • ENGINEERING SAFETY AND DISASTER PREVENTION
  • FAN Xin-yu, LUO Xue-dong, LI Jin-wei, LI Xuan, MEI Nian-feng
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 58-62. https://doi.org/10.11988/ckyyb.20140263
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    Analysing the primary and secondary factors of mine slope stability could provide basis for the monitoring and governance of slopes. Taking into account the influence of mining type and extreme climate in cold region, we considered blasting damage factor and freezing-thawing coefficient aside from general factors, and then carried out interactive test for all the factors using a nonlinear data evaluation model of uniform design in order to research the variation of slope stability coefficient under different factor levels. Furthermore we adopted grey correlation analysis to analyze the test results, and then sequenced the factors according to their correlation degrees. The results show that cohesion is the greatest influence factor with a correlation degree of 0.763, followed by modulus of elasticity, blasting damage factor and freezing-thawing coefficient, which indicates that rock mass strength has the largest influence on slope stability in cold region, yet the effects of blasting vibration and the freezing-thawing cycle are non-negligible.
  • NI Zhen-qiang, SHI Cun-peng, HAN Tao
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 63-68. https://doi.org/10.11988/ckyyb.20140250
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Under strong earthquake action, plastic zone penetrates through rock slope and makes it unstable. Encountered with external forces these unstable slopes are likely to become lagged landslides. In the present research we established a numerical model using finite element software ANSYS to simulate an unstable slope after Wenchuan earthquake. The simulation revealed that joint surfaces changed a lot after earthquake waves passed through, the movements of rocks on two sides of the joint surface were different; the internal shear stress and tensile stress of rock bridge fluctuated heavily, which induced the penetration of plasticity; the contact sliding distance distributed very unevenly, and the dynamic responses of different positions of joints were quite different. Finally, according to engineering geological survey results and characteristics of unstable slope, we identified the potential sliding surface, and proposed treatment measures including crack-grouting and slope-cutting.
  • CHEN Xu-dan,SUN Xin-li,CHENG Jin-xing,WEN Wei-wei
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 69-75. https://doi.org/10.11988/ckyyb.20150092
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    The vulnerability assessment for bearing body caused by single landslide is not highly quantitative. In view of this, we present a calculation method for the vulnerability of bearing body. On the basis of analyzing the process of landslide movement and the failure mechanism of bearing body, we introduced the plastic hinge concept and took plastic deformation process of bearing body into consideration to build a simplified calculation model. Furthermore, we simulated the deformation process of a reinforced concrete frame structure under the action of side force by using FEM software SAP2000, hence obtaining parameters of force and displacement for the simplified calculation model, and finally acquired the vulnerability results and classified the damage degree of the bearing body. Results show that the elastic-plastic process of building is similar to that of local plastic hinge, and the plastic process takes up a large proportion. The calculation results of safety distance 92.7m and distance 69.7m(V=1) are consistent with practical data.
  • HYDRAULICS
  • ZHOU Chi, LI Jing
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 76-79,89. https://doi.org/10.11988/ckyyb.20140255
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    Cavitation and cavitation erosion under high flow velocity and gate seal under high water head are two problems that high-head outlet structure is facing with in operation. To further understand the hydraulic and cavitation characteristics of aerators with sudden lateral enlargement and bottom drop, we took a hydraulic project’s flood discharge tunnel with orifices as research object and through a local hydraulic model with scale of 1:20, we analyzed the physical hydraulic parameters (wind velocity of ventilation hole, flow pattern, pressure, air concentration) of the middle lock chamber’s ventilation system and the aerator with sudden lateral enlargement and bottom drop. Furthermore we compared the test results with prototype observation results. Results showed that this project had good aeration effect. The test values of wind speed change with gate opening in ventilation pipe, flow aeration concentration, pressure and its fluctuation were consistent with prototype result. Prototype observation and practical operation both validate that the sudden enlargement layout meets practical demand, so it is safe and feasible. It is also an effective measure to solve gate seal and air entrainment to alleviate cavitation under high water head.
  • DUAN Wen-gang,WANG Cai-huan,TIAN Zi-qin,ZHENG Tao-ping
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 80-85. https://doi.org/10.11988/ckyyb.20140203
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    Damping well combined with tailrace tunnel with sloping ceiling is a new type of hydropower station’s tail pipeline. There is no such operation experience for large generation units with unit capacity of 700MW in China. To learn more about the hydraulic characteristics of tailrace system with sloping ceiling of large unit, and to validate the project design and the hydraulic model test results and to ensure the safe and stable operation of the project, we conducted field monitoring on the hydraulic transition process of load rejection of TGP’s underground power station in conditions of two characteristic reservoir water levels (trial run152.3m, normal storage 175.0m) and four load magnitudes (25%, 50%, 75%, 100%). The monitoring is focused on water hammer pressure of spiral case’s end parts and tail pipe’s inlet parts, damping well surge, unsteady free-surface pressurized flow of the tail pipe, and the increment of unit rotating speed. Analysis on the monitoring results suggests that the hydraulic indicators of the tail pipe meet the design requirement, with a certain safety margin. The monitoring results could be reliable basis for the design and project operation of tail pipe in the future.
  • YANG Ji-jian, LIU Han-sheng, DAI Shu-bing
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 86-89. https://doi.org/10.11988/ckyyb.20140269
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    Stepped spillways have gained significant interest and popularity among researchers. Energy dissipation rate and Froude number are important hydraulic parameters. In this paper we introduce the concept of relative Froude number of stepped spillway which reflects the effect of step on the value of Froude number through comparing the Froude number of stepped spillway and the corresponding Froude number of smooth spillway. Through tests on stepped spillways (with different step heights 0.5m, 1.0m, 2.0m and chute angle 38.66°), we investigate the relation between relative Froude number and relative rate of energy dissipation. Results show that in non-uniform flow the relative Froude number is in linear relation with relative rate of energy dissipation, and the correlation coefficient is 0.9927-0.9989. Further study shows that the slope of the linear relation increases with the increase of unit width discharge, but the height of step has only slight effect on the slope of the linear relation between relative Froude number and relative ratio of energy dissipation.
  • DAI Shu-bing, LIU Han-sheng, BIAN Xiao-wei, YANG Ji-jian
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 90-93. https://doi.org/10.11988/ckyyb.20140241
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to get the direct calculation formula of water depth in semi-cubic, square, and cubic parabola-shaped channels with contracted section, we identically transformed the basic equation of contraction water depth and obtained higher degree equation of non-dimensional contraction depth. But it could not be solved theoretically, so we obtained the iterative calculation formula of non-dimensional contraction depth by further transformation. Furthermore we employed 1stOpt software to optimize and fit the established nonlinear model parameters based on genetic algorithm and built the direct calculation formula of contraction depth for the semi-cubic, square, and cubic parabola-shaped sections. Error analysis and calculation example show that the maximum relative error is respectively 0.064%, -0.091%, and 0.136% within common engineering range λ∈[0.01,0.6]. The direct calculation formula is convenient, and has high precision and wide range of application.
  • ROCKSOIL ENGINEERING
  • HE Yu-hong
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 94-98,103. https://doi.org/10.11988/ckyyb.20140277
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The engineering application of present calculation methods for foundation pit’s springback deformation is limited due to a large number of required parameters and cumbersome calculation process. In this paper, the ratio of plastic deformation to total soil compression deformation was defined as the plastic development coefficient β, and on this basis, a new practical estimation method for the springback deformation was proposed. The expression of β can be deduced by the relationship between void ratio and compression deformation. The calculated depth of rebound soil can be estimated according to the influence of unloading ratio R on springback deformation. Ignoring the spatial effect of soil stress distribution in the center of deep foundation pit, and assuming that the gravity stress field of central pit bottom soil is uniform before and after excavation, we hence obtained the calculation method. The method was used to calculate the central springback deformation of a foundation pit (depth 17.9m) in Shanghai. By comparing calculated results with monitoring data, this method was proved to be feasible, and recommendations of prediction correction and engineering application were given.
  • LI He-zhi,ZHAO Yong-qing,CHEN Chun-ming
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 99-103. https://doi.org/10.11988/ckyyb.20140206
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    According to upper bound theorem of the limit analysis method, we analyzed the velocity field at the bottom of active slip zone ABC and transition zone BCD and passive slip zone BDE in a foundation pit. Virtual work-rate equation of plastic area at the bottom of the foundation pit was established. On this basis, the upper-bound solution to the depth of support excavations which meets the requirement of stability against upheaval was induced, and the stability safety factor k was solved when the support depth t was given. Engineering examples verified that the upper-bound solution and the formula of stability safety factor k are rational. The results could provide reference for the calculation of support depth in similar foundation pits, and improve the correctness of bottom soil stability in foundation pit.
  • CHEN Xiu-yun
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 104-110. https://doi.org/10.11988/ckyyb.20140990
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    Particle flow code was used to simulate uniaxial compression test of rock containing one closed central pre-existing fissure. The effects of fissure width, fissure length, friction coefficient and dip angle on the failure characteristics of cracked rock were analyzed. Results show that crack closure has impact on the strength and failure characteristics of cracked rocks. With the decrease of fissure length or increase of fissure's friction coefficient or the decrease of dip angle to zero or the increase of dip angle to 90°, the failure characteristic of cracked rock is more similar to that of intact rock. Extension of wing cracks and secondary cracks forms the macroscopic failure plane of rock. Mode-I fracture extension of wing cracks forms the macroscopic failure plane of rock while mode Ⅱ-Ⅰ fracture extension of secondary cracks forms the macroscopic failure plane of rock.
  • ZHU Xi-xi, CHEN Cong-xin, XIA Kai-zong
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 111-117. https://doi.org/10.11988/ckyyb.20140215
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    Having elaborated the importance of study on rock mechanics parameters, we introduced the principles and methods of determining rock mechanics parameters by Hoek-Brown criterion. The mechanical parameters of soft-hard interbedded rock slope at Pengjiawan of Yichang-Badong expressway are taken as research example. On the basis of physico-mechanical parameters, rock integrity factor and wave velocity obtained from laboratory test, we reduced the physico-mechanical parameters by Hoek-Brown criterion. Comparative analysis on the results suggest that the shear strength parameters determined by linear regression analysis and non-linear fitting method are both logical; the numerical simulation result is consistent with the deformation and failure characteristics of actual rock. The results provide guidance for the determining of rock mechanics parameters in other similar projects.
  • ZHANG De-yong, WANG Yu-zhou, ZHANG Zhi-hao, QIAN Ming
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 118-122. https://doi.org/10.11988/ckyyb.20140097
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    According to the statistical data of a large-scale project in Yunnan Plateau, a typical karst cave model covered with clay was established by employing ANSYS and FLAC3D, and the ultimate bearing capacity of foundation was calculated and its regularities were summarized in the presence of varying cohesion, internal friction angle, tensile strength, thickness of roof, depth-span ratio, cave radius, and cave width. Furthermore, through orthogonal analysis and rough set theory, the influences of these factors on the ultimate bearing capacity of the foundation were analyzed. Results reveal that roof thickness and shear strength have the biggest influence on the ultimate bearing capacity, followed by cave radius, depth-span ratio and cave width, while tensile strength has the smallest impact.
  • LI Zheng-bing, ZHANG Li-zhan
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 123-127. https://doi.org/10.11988/ckyyb.20150017
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    The arch dam of Jinping first-stage hydropower station had complex geological conditions of dam foundation. Fault f5 in the left bank, a typical large-scale weak rock mass with poor rock properties, is a crucial factor affecting the dam’s seepage stability, anti-sliding stability and deformation stability. The reinforcement effect determines directly whether the dam could work safely in the long run. In the present paper we explored and introduced the technologies of reinforcing the fault, including excavation-displacement, prestressed anchorage, high pressure consolidation grouting, cement-chemical compound grouting and the technique of “two-ended high pressure washing then backfilling with concrete”. Also we analyzed and evaluated the reinforcement effect. Monitoring data suggest that these reinforcement measures have worked as expected, shortened construction period, saved cost, and compared with single measure, these comprehensive measures met the requirements of seepage stability, anti-sliding stability and deformation stability, and can be taken as references for similar engineering.
  • CHEN Song,ZHOU Li-ming,LUO Shi-xin
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 128-133,139. https://doi.org/10.11988/ckyyb.20140296
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    Forecasting tunnel’s geological conditions using forward procedures of GPR (ground penetrating radar) provides interpretation basis, improves the accuracy of interpretation and helps avoid accidents. Currently most forward modellings are focused on the tunnel lining, but less on the surrounding rock in front of the working face.Through theoretical forward simulation by establishing large-scale geological model together with low-frequency antenna, we conclude that 1) the effective forecast distance is about 30m by using low-frequency antenna of 50MHz; 2) GPR could accurately identify the depth and shape of fracture zone, caves and other geological bodies, and cophase axis of reflected waves is consistent with that in theoretical model; 3) the variation trend of dielectric constant of surrounding rock in the front could be obtained from the wave phase and amplitude changes of single-channel data; 4) the electromagnetic waves attenuate more rapidly in complex model, and the simulation result is weaker than that of single geological model. Finally, we give two application examples to verify the forward modelling and provide a reference for reflected waves with the same shape.
  • WANG Jun-long
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 134-139. https://doi.org/10.11988/ckyyb.20140348
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    The multi-index models of predicting soil liquefaction level can be divided into two types: models based on classification standard of soil liquefaction level, and models based on instance data. In this research, instance data and data produced by stochastic interpolation based on classification standard were used as training samples. Dimension reduction of the samples was conducted through principal component analysis (PCA), and logistic regression model was adopted to describe the relationship between soil liquefaction level and its influencing factors. Hence the PCA-Logistic models were established for the two model types. Case study proves that the PCA-Logistic models are feasible in the prediction of soil liquefaction level. But the prediction result of the second type (which is based on instance data) of PCA-Logistic model is more in line with the actual situation, and especially has more practical value in the presence of more instance data.
  • CAO Yang-bing,YAN E-chuan,XU Jun,ZHANG Ting-ting
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 140-145,156. https://doi.org/10.11988/ckyyb.20140257
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    Based on the size of cavern section and the development characteristics of discontinuities, the preliminary bolt-shotcrete parameters were obtained for specific Q-value cavern surrounding rock using Q system. A water-sealed liquefied petroleum gas rock cavern in Shandong province was taken as research background. In view of the distribution characteristics of in-situ stress, the relationship between Q value and equivalent mechanical parameters of rock mass were established via GSI and Hoek-Brown failure criterion. Using 3DEC software, the preliminary bolt-shotcrete parameters were checked respectively from the aspects of continuous and discontinuous surrounding rocks using 3DEC software, respectively. Moreover, the security safety of support structure was evaluated based on the overloading safety factor law. Results show that: 1) when surrounding rock is continuous, the bolt-shotcrete support has an obvious effect on the displacement of surrounding rock, and the minimum safety factor of bolt is 2.75,while that of the shotcrete layer is 1.25, which indicate that the bolt-shotcrete parameters are safe and reasonable; 2) when surrounding rock is discontinuous, the bolt-shotcrete support fails due to the local unstability of blocks; 3) since the support object of Q system does not include local unstability block, so it is necessary to adopt discrete element numerical simulation for the support design, and it is important to discriminate local instability problems during construction stage.
  • GUO Hai-qing, ZHANG Min, HUANG Tao, AI Chun-bin
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 146-152. https://doi.org/10.11988/ckyyb.20140236
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    Slope's deformation stability has been a pressing issue in civil engineering. A large number of studies have shown that it is accurate to predict slope deformation using measured displacement-time series. But de-noising of data is needed because of errors caused by external factors. In the present paper we put forward a time shift wavelet coefficient correlation de-noising and wavelet-MGM(1, n) model. The model is based on time shift wavelet theory and gray theory. The slope displacement data of Jinping first stage hydropower station is taken as an example. Through decomposition and reconstruction of wavelet scale coefficients and approximation coefficients, the real signal is simulated, and the slope elevation-displacement curve is predicted. Validation proves that the prediction curve is very close to the measured curve.
  • HYDRAULIC STRUCTURE AND MATERIAL
  • SHAO Xiao-mei, LI Zhen,HAN Wei
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 153-156. https://doi.org/10.11988/ckyyb.20140220
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    In order to understand the expansion and deterioration of concrete in macro-and-micro senses,we took the alkali activity of sandstone aggregate of a large hydropower station in China as research background. In consideration of practical engineering demands, we carried out long-age simulation test on fully-graded mass concrete alkali aggregate reaction using SEM (Scanning Electron Microscope) test technology, and in association with the existing assessment system for alkali aggregate reaction, we researched the long-term inhibition of alkali activity. Results suggest that the characteristics of reaction product can be observed evidently by using SEM, the reaction degree can be obtained semi-quantitatively, and the trend of concrete deterioration can be estimated.
  • INSTRUMENTATION DEVELOPMENT AND TESTING TECHNIQUES
  • LI Jin
    Journal of Changjiang River Scientific Research Institute. 2015, 32(9): 157-160. https://doi.org/10.11988/ckyyb.20140107
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    For large power motors with fan or pump load, variable frequency speed regulation is an important means of energy saving. SVPWM (Space Vector Pulse Width Modulation) technology applied in variable frequency speed regulation system can not only improve the shortcoming of low voltage utilization in the PWM technology, but also have advantages of small torque ripple and low noise. In this paper, a SVPWM vector control AC asynchronous motor speed regulation system employing a core TMS320LF2407A-type DSP chip is presented. The basic principle of voltage space vector control is introduced, and the design of hardware and software in the system is analyzed. The obtained experimental results indicate that the speed regulation system has excellent dynamic and static performance and good control effect, so it has vast application prospect in high energy consuming devices such as fan and pump.