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01 February 2017, Volume 34 Issue 2
    

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    PROPERTIES OF GEOSYNTHETICS
  • XIANG Qian-yong,LIU Hua-bei,WANG Lei,ZHANG Ya
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 1-4. https://doi.org/10.11988/ckyyb.20161064
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    Generally it takes a long period of time to complete conventional creep tests on geosynthetic materials. The test environment such as temperature and humidity should also be exactly controlled,which makes such tests very expensive and time consuming. Moreover, conventional creep test cannot predict the creep characteristics in design life. In view of this, the accelerated creep test method of short-term time-temperature superposition has been proposed.In this article, according to the principle of short-term time-temperature superposition,three groups of short-term creep tests of high-density polyethylene(HDPE) geogrids at 10%,20% and 30% load levels were conducted by three-axis electronic creep testing machine. Through the indoor creep tests,the long-term creep characteristics of the HDPE geogrids at each small load level were predicted. Results show that the long-term creep strain of the geogrids at 10%,20% and 30% load levels were low and the values at 10% load level maintained within 2%;the short-term time-temperature superposition principle takes relatively short time to predict the long-term creep strain and stiffness values of HDPE geogrids. This study could be used as reference for engineering application.
  • SUN Hui, LIU Jun, TONG Jun
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 5-7. https://doi.org/10.11988/ckyyb.20161013
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    High polymer anti-crack paste could reinforce local structural layer of asphalt pavement by effectively resisting the tensile stress at the crack of the layer and controlling the crack width. In this article, the influences of width, tensile rate, clamping distance and surface fabric on the tensile properties of crack paste samples were studied with electronic universal testing machine controlled by microcomputer. Results showed that the tensile strength of polymer anti-crack paste decreased and changed remarkably with the increase of width, but increased gradually with the increase of tensile rate. Clamping distance had no obvious regular effect on the tensile strength of the crack paste; while the properties of surface fabric had large impact on the tensile strength of the crack paste.
  • XIE Shi-ping, HE Shun-hui, ZHANG Jian
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 8-12. https://doi.org/10.11988/ckyyb.20161011
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    As an alternative of traditional compacted clay layer,sodium bentonite geosynthetic clay liner(hereinafter referred to as GCL) has excellent performance of anti-seepage and isolation, hence has been widely used in the anti-seepage engineering of water conservancy, environmental protection, transportation and other fields. GCL has been applied in China for over two decades, but misunderstandings about GCL still exist, which hinders the further application of GCL. In this article, problems of GCL, inclusive of the flatness of geo-woven, the performance of bentonite, the cognition and the testing methods, are expounded according to our experiences in GCL production and research for over a decade. Results suggest that uneven geo-woven is not available for producing GCL; powdered GCL should be selected for project with GCL as a main impermeable layer; although as a secondary barrier layer in environmental projects, GCL is an important part of the whole anti-seepage system; detection of flatness and leakage should be included and also the early hydraulic conductivity of GCL should be reflected in the testing standards of GCL.
  • TONG Jun, DING Jin-hua, HU Bo, SUN Hui
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 13-16. https://doi.org/10.11988/ckyyb.20161016
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    As a special polymer material, geosynthetics is widely used in hydraulic, transportation and environmental engineering. In its service period, the capability of maintaining mechanical properties is of vital importance to the stability of the whole project. The aging properties of geosynthetics are important for predicting the accurate life time of geosynthetics, which is a current hot research topic. Outdoor photo-oxygen aging test on HDPE geogrid was carried out at the outdoor test base of Yangtze River Scientific Research Institute. Test results showed that in the initial 9 months, the tensile strength of geogrid remained unchanged or even increased due to secondary compensatory responses to the UV aging. UV provided required energy for chemical crosslinking, which resulted in the polymer crosslinking reaction and slight contraction in woven fabric. As a result, the tensile strength of geogrid increased in the initial period (9 months), but decreased after 9 months. The long-term research results of the test base could provide first-hand data for the physical and mechanical indexes of the aging properties of geogrid under outdoor exposure.
  • WANG Jing, SU Lin-wang, LI Tao
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 17-22. https://doi.org/10.11988/ckyyb.20161098
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    Prefabricated Vertical Drain (PVD) is a vertical channel of water discharge in foundation treated by drainage and consolidation. As the large settlement caused by foundation treatment results in the deflection of PVD, the corresponding decrease of flow capacity and reinforcement effect caused by the deflection of PVD should be studied. By building fixed iron frame model, PVDs were bended artificially to simulate the bending deformation in real working condition. On this basis, the water discharge capacities of four representative PVDs (conventional type with separated filtration fabrics, anti-silting type with separated filtration fabrics, conventional type with integral filtration fabrics, and anti-silting type with integral filtration fabrics) in different bending conditions were compared. Results indicate that conventional integral drainage board has the best drainage performance in the same bending form, followed by that of anti-silting integral type, filter-separated anti-silting type, and filter-separated conventional type. Core veneer, filtration fabric and bending angle are main factors influencing the flow capacity of PVD.
  • REINFORCEMENT MECHANISM AND REINFORCED SOIL STRUCTURE
  • LIANG Cheng, XU Chao
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 23-28. https://doi.org/10.11988/ckyyb.20161034
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    The vertical reinforcement spacing, which is not clear in present specifications, is an important parameter in the design of reinforced soil retaining wall and reinforced earth structure. According to the mechanism of reinforcement, shear band is concerned with the value of vertical reinforcement spacing, and also is closely related to the mechanical properties of reinforced soil. In this article, the causes and process of the formation of shear band are discussed, and then the research methods and results are summarized from three aspects including theoretical analysis, laboratory tests and numerical simulation. Results show that the thickness of shear band is affected by test apparatus and test conditions. Furthermore, some problems in current researches are pointed out. Finally, the development direction and prospect of shear band in the future are presented discrimination of the shear band, the stress-strain state within the soil of shear band, and the mechanics characteristics of composite reinforced soil mass will be the main directions of further research.
  • DING Jin-hua, TONG Jun, LIU Jun
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 29-34. https://doi.org/10.11988/ckyyb.20161030
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    The interaction between soil and geosynthetics is an important issue in the research of reinforcement mechanism, and the properties of reinforcement material are key parameters in the design of reinforced-soil structure. A new multifunctional soil-geosynthetics testing machine has been developed on the basis of conventional direct-shear test apparatus. The machine consists of two sets of servo motor, automatic control and data acquisition system, and a set of shear box with dimension of 600mm×300mm×300mm, etc. Direct-shear test, pull-out test, confined-tension test and confined-creep test can be conducted on the machine through several auxiliary means and control modes. Furthermore, the sand-confined tensile strength and creep properties of different geogrids were tested and compared. The contribution of geogrid-soil interaction to the strength of soil-geosynthetics was also analyzed. The tests validated that the machine has good operability and accuracy.
  • MA Qiang, XIAO Heng-lin, LI Li-hua
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 35-40. https://doi.org/10.11988/ckyyb.20161005
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    In the aim of identifying the influencing factors and their effects on load reduction effect for culvert beneath high fill, the method and mechanism of load reduction by reinforcement bridge are introduced firstly. On this basis, by means of numerical simulation, the influences of number of geogrid layer, width, height and lateral slope angle of load reduction ditches, as well as properties of filling material on the vertical earth pressure and the load reduction effect are investigated. Results suggest that the modulus of the filling material in the load reduction ditch and the height of the ditch have great effect on the load reduction. Ditches of larger height and lower material modulus lead to significantly better load reduction effect and less vertical earth pressures on the crown of culverts. The width of load reduction ditch, number of geogrid layer and internal friction angle of backfill material have little effect on the load reduction, but the increase of the width of the load reduction ditch results in more uniform internal forces for the culvert and a decrease of bending moment.
  • ZHANG Jun , LIN Yong-liang, ZHANG Bo
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 41-44. https://doi.org/10.11988/ckyyb.20160281
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    The interaction between soil and reinforcement is the fundamental cause of the strengthening of reinforced soil. It is also a key issue in the application of geosynthetic reinforced soils. In this article, the effects of normal stress, sand cushion thickness and spacing between transverse ribs on ultimate pullout resistance of reinforced body were analyzed through pullout test. The mechanical properties of reinforcement-soil interface were also revealed in a macro-sense. Results suggest that sand cushion of 5 cm thickness could remarkably enhance the ultimate pullout resistance of geogrid. The influence of sand cushion thickness on test result is more obvious under large normal stress. Moreover, the frictional angle of geogrid-soil interface decreases with the increasing of the spacing between transverse ribs; but the cohesion stays stable. The shape of geogrid is also an important factor affecting the properties of interface between reinforcement and soils.
  • DU Yun-xing, ZHOU Fen, LIANG Qiang
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 45-51. https://doi.org/10.11988/ckyyb.20161017
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    The mechanical properties of reinforced body with double unbonded prestressed reinforcements are affected by the pre-tension applied on it. In scale model tests, steel shot was adopted to simulate the intensity of cohesionless fill and the stress state of the reinforced body. The distribution of deformation in the reinforced body and the soil pressure on the back of slab were obtained through applying pre-tension on unbonded prestressed reinforcement and heaped load at the top of reinforced body step by step. The test results were compared with those of common reinforced body. Results revealed that the settlement on the top of the reinforced body in the presence of pre-tension was smaller than that of common reinforced body in the absence of pre-tension. The increment of pre-tension reduced the horizontal deformation of slab and affected the settlement on the top of the reinforced body, which depends on the position of unbonded prestressed reinforcement. Moreover, the horizontal deformation of slab and vertical deformation of the prestressed reinforced body changed little under heaped load. When applying pre-tension, there is almost no interaction between the reinforcements.
  • ZHOU Yue-feng, GONG Bi-wei, ZHOU Xiao-wen, TONG Jun
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 52-55. https://doi.org/10.11988/ckyyb.20161022
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    The accuracy and reliability of a centrifuge model test depend on the similarity between the model and the prototype. Selection of a reasonable similar material is a key procedure of the centrifuge model test. The background of this study is the engineering design of a retaining dam for garbage deposit in Guangzhou City. A total of six types of woven-cloth were analyzed for the rationality of centrifugal model test. In consideration of strength similarity and interface friction factors, the similar materials were selected based on narrow strip tensile tests and frictional direct shear tests. According to design scheme, the model slope remains stable in the centrifugal field. Numerical analysis and engineering comparison should be taken into account to determine the design scheme. According to strength similarity, the selected materials can be used to simulate geotextiles with 13-360 kN/m tensile strength via adjusting the compacted thickness of each soil layer.
  • WAN Liang-long, CHEN Fu-quan, ZOU Wei-lie
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 56-62. https://doi.org/10.11988/ckyyb.20161014
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    Geosynthetics could be used for reinforcing embankment subjected to the influence of potential localised karst collapse. In this paper, the displacements and stresses in both embankment and geosynthetics, and the bearing mechanism of geosynthetic-reinforced embankment are analyzed in detail based on the numerical simulation results from PLAXIS3D software by using large deformation analysis method with updated mesh function. Moreover, the influences of design parameters (including size of karst collapse, embankment height, geosynthetic’s tensile stiffness and properties of embankment soil) on the maximum settlements of embankment and the maximum tensions of geosynthetics are investigated. Results indicate that the maximum settlement of embankment is depended on whether a closed stress dome in embankment is formed, and the height of the stress dome is mainly related to the size of collapse and the cohesion of embankment soil. Geosynthetic’s tensile stiffness, embankment height, and internal friction angle of embankment fill have slight influence on the height of stress dome. The maximum longitudinal and transverse tensions of geosynthetics are related to the longitudinal and transverse stiffness of geosynthetics, and the differences of both maximum pavement settlement and strain in geosynthetics caused from uniaxial and biaxial geogrids are small.
  • LI Liang-yong, CHEN Jian-feng, XU Chao, GUO Peng-hui, CHEN Bao-cheng, YANG Xiao-nan
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 63-68. https://doi.org/10.11988/ckyyb.20161069
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    In the aim of investigating the soil arching of geotextile-encased stone columns, we established a three-dimensional finite element model of geotextile-encased granular columns composite foundation under embankment load to analyze the influences of geotextile stiffness, column spacing and embankment height. Results indicated that the ratio of geotextile modulus to soil modulus which induced the start of soil arching was 20. The modulus ratio had little effect on soil arching after reaching 67. The height of soil arching increased linearly until the height of embankment reached 5 times of net spacing and then remained constant. The required height for a complete soil arching increased with the increase of net spacing. When net spacing reached twice the pile diameter, the height of soil arch remained stable. Moreover, with the increase of embankment height, the soil arch rate decreased gradually. When the height of embankment reached 1.7 times of net spacing to form complete soil arch, the soil arching rate did not change anymore. Compared with numerical results, we found that the results calculated by the three-dimensional soil arching method proposed by Hewlett and Randolph are the closest to the numerical results, and we suggest to use this method for design.
  • MA Qiang, XING Wen-wen, LI Li-hua, ZHENG Zhen-yi
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 69-74. https://doi.org/10.11988/ckyyb.20161006
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    Bamboo slats (thickness of 5mm, width of 10mm, and length of 20, 40, 60mm respectively) were added into soil in different mass percentage contents (0.2%, 0.4%, 0.6%, 0.8%, 1.0%, and 1.2%). Then large-scale direct shear test was carried out on the soils reinforced with the bamboo slats to investigate the reinforcement mechanism. Results reveal that compared with pure sand, the shear strength of reinforced soil is obviously improved, the peak strength and residual strength are increased; and also cohesion and friction angle have increased, among which cohesion increased greatly; the peak shear strength of reinforced soil increased firstly and then decreased with the increasing size and percentage of bamboo slats; the optimal size of bamboo slat is 10mm×40mm and the optimal ratio of reinforcement is 0.8%.
  • XUE Peng-peng,ZHENG Jun-jie,CAO Wen-zhao,LAI Han-jiang
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 75-79. https://doi.org/10.11988/ckyyb.20161066
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    A composite retaining structure composed of reinforced soil retaining wall and anti-slide piles is proposed to solve the construction problems in high fill embankment upon soft soil. Finite difference software FLAC3D was used to establish the numerical models of composite retaining structure. The influences of cast mode of panels on lateral displacement of wall surface,lateral earth pressure behind retaining walls,lateral displacement and bending moments of anti-slide piles and stress distribution of geosynthetic geogrids were analyzed. Numerical results revealed a linear distribution of lateral displacement of panels in post-cast rigid mode and the maximum displacement at the top of walls. Earth pressure on post-cast panels was far less than that on rigid panels. Moreover,the displacement and bending moments of anti-slide piles in the composite retaining structure with post-cast rigid panels were larger than those in the structure with rigid panels. The largest tensile stress of geosynthetic geogrids in the structure with rigid panels was found at the junction between panels and geogrids;while for the structure with post-cast rigid panels,the position of the largest tensile stress deviated from the retaining wall as the layer of geogrids were higher.Composite retaining structure with post-cast rigid panel could be used and promoted in high embankment area on soft soil due to its good performance with small displacement and earth pressure on post-cast panel.
  • WANG Chun-hai, LIU Hua-bei
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 80-83. https://doi.org/10.11988/ckyyb.20161020
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    A non-linear elastic incremental analysis method for reinforcement loads is introduced in view of the fact that most available methods are not suitable for reinforced soil slopes under working stress conditions. The method is based on the generalized Hooke’s law in the light of the soil-reinforcement compatible deformation at the potential failure surface and the nonlinear elastic constitutive relation of soil with Duncan-Chang model. The analytical results of three slope examples with different inclination angles by incremental analysis method are compared with those by finite element method. The comparison results reveal a very high accordance between the two methods for vertical slopes, which indicates that the incremental analysis method is very suitable for reinforced vertical slopes; but when the angle between slope surface and vertical direction increases, the difference of the results increases, which could be modified by reduction factor. Incremental analysis method has a broad application range with advantages of being simple, practical and efficient. This research is expected to promote understandings of the mechanism of the interaction between soil and reinforcement, and shed some light on the design of geosynthetic-reinforced slopes.
  • LEI Sheng-you, HUI Hui-qing, GAO Pan, ZHANG Lei
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 84-88. https://doi.org/10.11988/ckyyb.20161021
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    In order to reveal the deformation law of a three-level reinforced earth retaining wall in a V-shaped valley,according to in-situ test data, we analyzed the changes in wall panel displacement, settlement of backfill of the wall, settlement of road surface on high fill, and settlement of the bottom of culvert beneath the wall in construction period and after completion. Results revealed that the vertical and horizontal displacements of wall panels, and the deformations of the backfill mainly occurred during the construction period, and the values of displacements and deformations were relatively large. One or two years after the completion, the deformation tended to be stable, but the total cumulative deformation was large, which indicated that the reinforced earth retaining wall could adapt to the large deformation of filling projects, which is an advantage. Moreover, the structure of reinforced high earth retaining wall beneath high fill in V-shaped valley could meet the challenges posed by road surface settlement, and the culvert beneath high fill is safe. Besides, since the reinforcements of the wall are reinforced concretes, the reinforced earth wall has some advantages of anchoring board retaining wall and soil nailing wall, which could restrain the deformation of soil mass in the wall, and also serves as a whole to coordinate the deformation of V-shaped valley. Hence the stresses in the fill are redistributed, road surface settlement and deformation are transited smoothly with no significant settlement difference and good application effect.
  • SEEPAGE CONTROL, FILTER AND DRAINAGE
  • LI Shao-long, ZHU Guo-sheng, DING Pei-zhong, WU Qing-hua, SHENG Xiao-tao
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 89-93. https://doi.org/10.11988/ckyyb.20161070
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    Groundwater is an important influential factor of bank slope stability, and drainage facility for bank slope is necessary in waterway regulation project. Horizontal drainage holes could effectively reduce groundwater level by draining away the water of deep soils. The drainage effect of horizontal drainage holes in bank slope is studied by means of three-dimensional transient seepage numerical simulation. The numerical result agrees with indoor model test result. The groundwater of slope converges to horizontal drain and drains away from slope. Simulation of characteristic real bank slope shows that the drainage effect of horizontal drain for bank slope is apparent, and the control region of seepage field is enlarged. The deeper the drainage hole is, the better the drainage effect is. The research results could provide references for the application of horizontal drainage holes in waterway regulation engineering.
  • SHENG Xiao-tao , GU Xie-qin, DING Pei-zhong, LI Shao-long, ZHU Guo-sheng, YAN Min
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 94-98. https://doi.org/10.11988/ckyyb.20161264
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    In the aim of investigating the drainage effect of horizontal drainage holes in bank slope, in-situ tests were carried out on a bank slope of Yangtze River through arranging horizontal drainage holes of different depths with replaceable filter. The drainage effects were compared with that of blind ditch to validate the effectiveness and operability of drainage holes. Results of water level monitoring suggest that the water level in bank slope is closely related with that of the Yangtze River when river water level rises, groundwater of bank slope is recharged; whereas when river water level declines, groundwater of bank slope discharges to the river. We conclude that horizontal drainage holes have good effect in drainage and pressure reduction. The drainage effect of bank slope in the presence of drainage holes is better than that of conventional blind ditch; and the effect of drainage holes of 15m depth is superior to that of 8m depth.
  • HUANG Chao-xuan,FANG Yong-lai,ZENG Zhen
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 99-103. https://doi.org/10.11988/ckyyb.20161075
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    At present, traditional sand well consolidation theory is adopted to calculate the consolidation characteristics of foundation treated by prefabricated vertical drains. The equivalent diameter of prefabricated vertical drain can be obtained by formulas including Hansbo’s perimeter equivalence and the equivalent reduction 0.75 times the perimeter in Code for Design of Sea Dike Project. But there is no unified understanding on it. In view of this, an analytical solution for the consolidation of foundation treated by prefabricated vertical drains is presented based on equal strain assumption. The rationality of this solution is validated by using ADINA. Furthermore, finite element method is adopted to build a 2D model of foundation treated by prefabricated vertical drains. The coefficient of permeability of drain tends to infinity in the model. It is found that the consolidation characteristics in the 2D model by Long & Covo (1994) are close to those by finite element method, yet with some deviations. Finally, the formula for calculating the equivalent diameter of 2D consolidation model of higher accuracy is given.
  • YANG Xin-guang, XU Tang-jin, XU Han, CHEN Yun
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 104-109. https://doi.org/10.11988/ckyyb.20161019
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    The impervious system of cofferdam, which is composed of composite geomembrane and impervious wall, is easily damaged at the joint parts. In view of this, the pattern of joint between composite geomembrane and impervious wall needs to be studied in order to insure the safety of the whole cofferdam and to avoid the damage of geomembrane caused by the deformation difference between cofferdam body and impervious wall. A case study on the high earth-rockfill cofferdam of a hydropower station in west China was carried out by means of nonlinear finite element method. The research focused on the stress and deformation behaviors of the geomembrane and the high cofferdam built on deep overburden. Results show that the joint pattern had little influence on the stress and deformation of dam body and impervious wall, but had significant influence on the geomembrane strain and the deformation difference between dam body and impervious wall. If the geomembrane is laid horizontally on the top of impervious wall, the settlement difference could induce large tensile strain of geomembrane at joint parts. With the rising of the location of geomembrane, the tensile strain decreased remarkably, which is beneficial for its safety. In conclusion, it is reasonable to lay the geomembrane above the impervious wall for a distance. The critical thickness of overlaying soil should be determined by indoor pull-out tests.
  • XU Han,CHEN Yun,RAO Xi-bao,PAN Jia-jun
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 110-113. https://doi.org/10.11988/ckyyb.20161056
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    To reflect the mechanical properties of composite geomembrane in 3-D finite element calculation is a technical problem to be solved. On the basis of summarizing current numerical methods of geomembrane simulation, we propose to simulate the geomembrane using membrane element in 3-D finite element calculation. By building a finite element model of high earth-rock cofferdam of 65 m height with geomembranes contacted with dam in the upstream and downstream, we simulated the flexible and rigid constraint conditions of geomembrane boundary respectively in filling construction and impounding stages. Results suggest that the membrane element could well reflect the flexible tensile properties of geomembrane. The proposed method could also adapt to the stepped filling in 3-D finite element simulation. Moreover, it could conveniently and effectively display the displacements and stresses of geomembranes in post-processing. The displacement distribution of geomembrane under flexible boundary restraint was the same with that under rigid boundary constraint; while the principal tensile stress and its distributed region under flexible boundary constraint were slightly smaller than those under rigid constraint. The calculation results are consistent with the general rules of earth-rockfill dam.
  • ENGINEERING APPLICATION AND OTHERS
  • CHEN Yun,HU Zhi-gang,WU Zheng-ping,XU Han
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 114-119. https://doi.org/10.11988/ckyyb.20170025
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    The application of composite geomembrane in water conservancy and hydropower engineering in China is mainly concentrated in fields such as channel,low dam,cofferdam,and dam seepage control,but rarely in high earth rockfill dam. With the application of composite geomembrane in the high earth rockfill dam of Luding hydropower station as a research background,we summarized some key points of quality control for composite geomembrane in terms of welding test,laying construction,quality control and welding quality inspection. We also proposed some specific construction techniques and detection methods for the suture of geotextile, welding of geomembrane, and the connection between geomembrane and concrete in grouting gallery. This research provides reference for the application and quality control of composite geomembrane in similar engineering.
  • HUANG Yue-wen
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 120-125. https://doi.org/10.11988/ckyyb.20161071
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    Geosynthetics are widely used in hydraulic projects in Guangzhou city. In this article, experiences and understandings in the application of geosynthetics to hydraulic projects in Guangzhou are discussed. Geotextiles are widely used for anti-filtration design in hydraulic engineering, but attentions should be paid to the invalid drainage when geotextiles are clogged by slurry during construction. Geotextiles can also be applied to localised treatment of soft soil foundation, but the settlement is generally large and occurs over a long period. Moreover, geotextiles can be placed between erosion-resistant facility, such as anti-scour trench, and foundation soil to protect the soil from erosion damage. Soil filling geotextile bags are widely used in cofferdam and emergency projects, but rarely in embankment projects due to worries about their quality and durability. Furthermore, an example of EPS(expanded polystyrene sheet) used in soft soil treatment in a sluice connecting embankment is introduced, and the importance of surface protection and anti-floating calculation is pointed out. The applications of ecological retaining wall and ecological bags to river revetment projects in Guangzhou are also introduced. But worries about the quality and durability of ecological bags affect the popularization of eco-bag technology.
  • LIU Bo, NIU Yun-hua, WANG Ying-kui, DAI De-fu
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 126-131. https://doi.org/10.11988/ckyyb.20161041
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    The dam site of Wudongde Hydropower Station is threatened by a number of debris flow gullies. In this article, some prevention and control measures are presented to avoid huge losses caused by debris flow disasters. The static and dynamic characteristics of debris flows in Zhugongdi Gully were analyzed by means of field investigation and laboratory model test. In view of the particularity of terrain, geological conditions and project layout, the countermeasures of debris flow were proposed. In addition, the effect of the countermeasures in Zhugongdi Gully was tracked and evaluated. Results show that block dam could effectively prevent large particles of solid matter from being involved in debris flow activity and reduce the erosion degree of upstream gully. Silting field could detain some small particles of solid matter, and as a consequence only a small amount of solid substances and the flood are discharged through the drainage canal. Triangular drainage canal has the characteristics of three dimensional beam current, so the draining effect is significant. The outlet of drainage canal is located in hard bedrock with strong anti-scouring ability, conducive to the stability of drainage canal. The control system composed of block dam, silting field and drainage canal has good control effect. This research can be used as a reference for debris flow treatment in the future.
  • LUO Shun-cheng,GU Huan-da,CHEN Dong-qing
    Journal of Changjiang River Scientific Research Institute. 2017, 34(2): 132-138. https://doi.org/10.11988/ckyyb.20151061
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    Foamed mixture lightweight soil using river sludge(FMLSS) as a new engineering material of light weight and high strength is applied widely in engineering. By using physical and mechanical test methods on density, strength and consolidation, the physical and mechanical characteristics of FMLSS are analyzed in the presence of different cement contents, air foam contents, water contents and curing ages. Results show that the density, strength and deformation of FMLSS are mainly affected by cement content, air foam content and water content, and the influence of interaction among different factors cannot be ignored. In addition, the strength and stiffness of FMLSS are also affected by curing age, with which displaying a good hyperbolic relationship. Under external load, FMLSS shows good resistance to deformation. The study indicates that FMLSS has good engineering applicability and application prospect.