01 April 2019, Volume 36 Issue 4

    

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SPECIAL CONTRIBUTION
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  An Optimization for the Calculation Method of Deep Anti-sliding Stability with Multiple Sliding Surfaces for Gravity Dam

  PENG Wen-ming

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 1-8. https://doi.org/10.11988/ckyyb.20181267

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  In Design code for concrete gravity dam (NB/T 35026-2014) of China, the method for anti-sliding stability with multiple sliding surfaces gives the solution of resistance-action ratio η based on the prerequisite that resistance ΔQ_i of sliding blocks meets internal force equilibrium. However, as the angles between ΔQ_i and horizontal direction are different, the method in the code is of no physical significance, hence could not really meet the balance of internal force vectors. In this paper, we demonstrates that the theoretical system of the method in the code is not rigorous, which might give rise to wrong result when the values of φ_i are not equal. In view of this, we optimized the method by replacing ΔQ_i with shear force Q_i between blocks, and proposed an iterative solution based on single variable η. Through typical examples and engineering applications, we further verified that the imprecision of the standard method may lead to unacceptable calculation errors; and at the same time, we proved the accuracy and practicability of the proposed method in this paper.
RIVER-LAKE SEDIMENTATION AND REGULATION
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  Study on Dike-break Flood and Scouring: Review and Prospect

  ZHANG Xin-jian,QU Geng,FAN Bei-ling,ZHU Yong-hui

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 9-12,38. https://doi.org/10.11988/ckyyb.20171143

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  Due to the serious consequences of dike break, researchers all over the world have paid great attention to dike-break flood and scouring. In this paper, we made a review on dike-break flood and scouring from aspects of theoretical research, mathematical model, and physical model test. We summarized the development, research progress, and achievements in this regard, and by depicting the advantages and shortcomings of the aforementioned three research approaches, we reckon that single approach does not meet current requirements on the study anymore. Developing a comprehensive research method integrating various approaches with wide application scope, high simulation precision could be a crucial direction for future research. Moreover, theoretical research should be strengthened, and development on monitoring instruments should be also intensified to offer technical support for flood control and disaster prevention.
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  Fine Management of Water Quality Target on Rivers into Dianchi Lake

  YAO Yun-hui, MA Wei,SHI Guo-wu, JIANG Ru-cheng, SHU Guo-biao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 13-18. https://doi.org/10.11988/ckyyb.20181028

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  Total capacity control and target management on water quality as effective ways to implement “The Action Plan for Prevention and Treatment of Water Pollution” and “River (Lake) Chief System” are optimal management approaches for the comprehensive water pollution treatment and water quality protection of Lake Dianchi. On the basis of a good understanding of the water resources condition and unique water cycle in Dianchi Lake catchment under varying circumstance, we re-modeled the water environment capacity and analyzed the spatial-temporal dynamics of water environment capacity in Dianchi Lake via a fine-tuned numerical model. Furthermore, we proposed to control the water quality limits for each partition and time period, and set up fine management plans for the control of water quality into the Lake. The research achievement provides a technical support for comprehensively promoting the River Chief System in Dianchi Lake.
WATER RESOURCES AND ENVIRONMENT
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  Influence of Rain Gauges Network Configuration on the Accuracy of Rainfall Spatial Interpolation and Hydrological Modeling

  WANG Qing-jing, YANG Xin-yue, CHEN Hua, XU Chong-yu, ZENG Qiang, XU Jian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 19-26. https://doi.org/10.11988/ckyyb.20170624

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  To investigate the influence of rain gauges network configuration on the accuracy of rainfall spatial interpolation and hydrological modelling,we selected different distributions of six rain gauges over the study basin and compared the results of four interpolation methods for 9-year(2006-2014) daily rainfall data. Then we calculated the mean areal daily rainfall series for different network configurations and used as the inputs of Xinanjiang model to obtain the simulated runoff. The results show that: 1) evenly distributed rain gauges lead to smaller rainfall interpolation error and higher hydrological modeling efficiency; 2)when the rain gauges are evenly distributed, no significant differences among the four rainfall interpolation results are found, while when the rain gauges are unevenly distributed, such differences are obvious especially for small rain gauge density networks; and 3) for point rainfall interpolation, Kriging interpolation method in consideration of spatial autocorrelation in residuals performs better than the other methods in calculating actual daily rainfall; for mean areal rainfall,the difference between different interpolation methods is small so we suggest to adopt a simple interpolation method, such as Thiessen Polygons or inverse distance weighted method.
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  Effect of Aquatics Combination System in Purifying Eutrophic Scenic Waters

  XU Ming-yu, LIU Wen, TAN Guang-wen, HUANG Shao-bin, WU Jin-hua, LU Yi-fei, CHEN Ping

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 27-31. https://doi.org/10.11988/ckyyb.20170878

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  An aquatics combination system composed of Bischofia javanica, Hygrophila salicifolia, Vallisneria natans, Macropodus opercularis, Cipangopaludina Cahayensi and biomass char was applied to the treatment of eutrophic garden scenic waters. The growth status of aquatics in this system and the aquatics’ effect of eliminating larvae and wiggler as well as the purification effect for TN, TP, COD, NH⁺₄-N, and NO^-₂-N in the water body were examined. Results showed that no larvae or wiggler was found in the aquatics combination system which enjoyed a good growth status and a satisfactory effect of removing pollutants. The removal rate of TN, TP, COD, NH⁺₄-N, and NO^-₂-N reached 64.4%, 49.5%, 65.7%, 73.8% and 82.6%, respectively. The content of TN, COD and DO met the standard of surface water quality IV-level specified in national standard GB 3838—2002, and NH⁺₄-N measured up to level Ⅱ. In conclusion, each component in the aquatics combination system performs its duty, and the technology is pollution-free, hence is conducive to the sustainable water ecological restoration.
FLOOD PREVENTION AND DISASTER REDUCTION
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  Influence of Water Content Variation on Mechanical Properties of Riverbank Cohesive Soil of Jingjiang River Reach

  LIU Zhao-xi, WANG Jun, ZONG Quan-li, ZHOU Yin-jun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 32-38. https://doi.org/10.11988/ckyyb.20180867

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  Bank retreat is affected by the physical and mechanical properties of riverbank soil as a major factor. To research the influence of water content on the mechanical properties of riverbank soil of Jingjiang River reach, the composition and mechanical properties of soils on Jingjiang riverbank were examined in a holistic sense via data analysis, indoor test and theoretical analysis; moreover, the effect of water content variation on the shear strength indicators of cohesive soil on Jingjiang riverbank and further on the riverbank stability was quantified using measured data of 2016. Eight typical bank retreat sections were sampled in 2017. Results suggest that the soil composition in the Jingjiang River reach is characterized by a typical composite structure involving cohesive upper layer and non-cohesive lower layer. With the augment of water content, cohesion of soil increased first and then decreased, while internal friction angle reduced continuously. In general, higher content of cohesive particles leads to greater peak value of cohesion. In addition, the formulae between water content and shear strength indicators are given. The stability of riverbank in dry season is fairly good, larger than that in rising stage; but in flood season and recession stage, riverbank stability is undesirable.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  A Method of Estimating Lacking Deformation Series of Concrete Dam Based on Spatial Distribution

  HU Tian-yi

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 39-42. https://doi.org/10.11988/ckyyb.20171163

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  As a typical spatio-temporal data, the monitoring data of concrete dam deformation in lack at some partial points would bring about inconveniences for deformation analysis. In this paper, we present a method of estimating the missing data of deformation sequence by proposing a spatial proximity point regression interpolation method and a space inverse distance weighted interpolation method based on integral deformation sequences of monitoring points in the vicinity of missing points. Engineering examples verifies that the method proposed in this paper is simple, clear, and is highly precise.
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  Temporal and Spatial Coupling Relationship Between Debris Flow and El Nino-La Nina Event in Southwest China

  GAO Yun-jian, CHEN Ning-sheng, HU Gui-sheng, DENG Ming-feng

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 43-48. https://doi.org/10.11988/ckyyb.20170988

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  Researching the temporal and spatial distribution characteristics of debris flow in mountainous area of southwest China under the influence of El Nino-La Nina event will be conducive to providing basic guidance for the prediction of debris flow disaster. According to statistical data, we examined the spatiotemporal coupling relationship between debris flow events and El Nino-La Nina events in mountainous area of southwest China through GIS spatial analysis approach. We found that 1) in El Nino-La Nina year, the frequency of debris flow disaster in mountainous area of southwest China increased in temporal scale, and the occurrence frequency in La Nina year was larger than that in El Nino year; 2) in spatial scale, under El Nino and La Nina events, debris flow disaster was mainly concentrated in mountainous area of southeast Tibet, Hengduan Mountains, northeast Yunnan Province, west and southwest parts of Guizhou Province, northwest Yunnan Province, Dadu River basin, and Yalong River basin, etc; 3) in El Nino-La Nina year, rainfall amount in the debris flow stricken area was larger than multi-year average rainfall in general. We conclude that debris flow events in mountainous area of southwest China are evidently correlated with El Nino-La Nina events.
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  Cushioning Capacity of Soils Against Rockfall’s Impact Force Based on Two-dimensional Particle Flow Code

  JIANG Wei, SONG Peng-cheng, CHEN Wei, WANG Yan-hai, MAO Cong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 49-54. https://doi.org/10.11988/ckyyb.20171069

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  In the design of rockfall protection structure, the cushioning capacity of soils on stone cutoff wall or shed-tunnel against rockfall’s impact force should be taken into consideration properly. PFC2D could simulate the dynamic process of rockfall impacting on the soil and structure effectively. The calculated result of rockfall’s impact force by PFC2D with no consideration of soil’s cushioning capacity is consistent with that by Swedish algorithm (proposed by Dr. Vincent Labiouse) and slightly larger than that by Japanese algorithm (proposed by Japanese Road Association). Furthermore, the impact forces of rockfall from different heights on structure with soil cushions—plain filling soil, silty clay, and sandy silty soil each of different thicknesses—are analyzed. The cushioning capacity of soil is in exponential function relation with soil cushion’s thickness and rockfall’s height; while the influence of falling height on cushioning capacity does not change with the change of soil material. Given the same soil thickness, the cushion capacity of silty clay is the largest, followed by that of plain filling soil and sandy silty soil in sequence. From an economic point of view, the thickness of soil cushion is recommended to be within 2-3 meters in engineering practice.
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  Displacement Prediction of Baishuihe Step-like Landslide by Least Square Support Vector Machine

  LI Shi-bo, LI De-ying, ZHANG Yu-en, LI Jie

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 55-59,76. https://doi.org/10.11988/ckyyb.20170944

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  Landslide displacement is the most intuitive manifestation of landslide deformation, and the prediction of displacement plays a very important role in judging the evolution trend of landslide. Landslide displacement curve is a non-stationary time series affected by various factors. In this paper the trend displacement of Baishuihe landslide in the Three Gorges Reservoir is extracted by the HP filter method. Because of the nonlinear increasing characteristics, the trend displacement which is determined by the characteristics of the landslide is fitted and predicted by polynomial. In the meantime, induced by various factors such as evolution stages, seasonal rainfall, and water level fluctuation, the periodic displacement is trained and predicted by the model of the least squares support vector machine model (LS-SVM). The prediction result of the cumulative displacement is the superposition of the trend term and the periodic term. The results show that the LS-SVM model has high precision in the prediction of monitoring point ZG93 and XD-04, implying that LS-SVM model is of good adaptability in predicting step-like landslide.
HYDRAULICS
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  Numerical Study of Characteristics and Discharge Capacity of Piano Key Weir

  HU Han, YANG Wei, HOU Dong-mei

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 60-66. https://doi.org/10.11988/ckyyb.20171116

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  The three-dimensional flow fields in a piano key weir were simulated using the volume-of-fluid (VOF) model, and the reliability of VOF model result was verified according to Lempérière’s test result. An orthogonal numerical test revealed major geometric parameters that affect the discharge efficiency of piano key weir. Numerical simulations and theoretical analysis were conducted to analyse the effects of these geometric parameters. New formula for the discharge of piano key weir was then derived and verified. The maximum relative error of the proposed formula is 6.7%, and the mean relative error 3.7%. The proposed formula improves the accuracy of the design and structural optimization of piano key weir.
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  Prototype Observation of Roughness and Overflow Capacity in Pandaoling Tunnel

  HU Pu-nian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 67-70,76. https://doi.org/10.11988/ckyyb.20170949

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  Hidden dangers such as cracks, surface concrete denudation and groundwater infiltration appeared on Pandaoling tunnel, a long-distance pressure-free tunnel with a length of 15.723 km due to the complex lithology and severe geological conditions. In September 2013, the tunnel was reinforced with lining of a minimum thickness of 0.25 m which reduced the tunnel’s overflow section. The reinforcement also reduced the roughness of tunnel surface which is a key factor determining whether the overflow capacity meets design requirement. Conventional calculation and test of roughness could hardly meet accuracy requirements. In view of this, prototype observation was conducted. The theoretical basis, observation approaches and methods of prototype observation are introduced in this paper, and the rationality of observed roughness and discharge capacity of tunnel sections are analyzed. The roughness of rectangular open section, tunnel entrance without reinforcement, tunnel entrance with reinforcement, and tunnel outlet with reinforcement is 0.013 07, 0.015 49, 0.011 16, 0.010 52, respectively. According to the measured water level in the observation section, the overflow capacity of the Pandaoling tunnel after reinforcement meets design requirements.
ROCK-SOIL ENGINEERING
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  Application of Umbrella-shaped Anchor to the Reinforcement of Temporary Expansive Soil Slope in North Hubei Water Diversion Project

  CHENG Yong-hui, WANG Man-xing, XIONG Yong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 71-76. https://doi.org/10.11988/ckyyb.20171050

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  Expansive soil stratum is featured with deep fissure development which brings about stability problems to high slope of expansive soil in excavation process. Commonly used reinforcement or protective measures for temporary high slope of expansive soil are of poor adaptability and low economic benefit. Prestressed umbrella-shaped anchor is a new solution for the reinforcement of temporary expansive soil slope. In order to solve the stability problem in the excavation of expansive soil slope in Water Resources Allocation Project in North Hubei Province, we conducted field test of prestressed umbrella-shaped anchor and evaluated its popularization value in practical application. Research result demonstrates that prestressed umbrella-shaped anchor is of fast construction and large resistance against pull-out force, hence effectively controlling deformation development and ensuring slope stability. According to the safety monitoring data of slope, we verified that umbrella-shaped anchor is of good application and popularization values in the rapid reinforcement of expansive soil slope.
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  Investigation on Influence of Underlying Karst on Bearing Capacity of Pile Foundation by Finite Difference Method

  XIE Shu-meng

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 77-81. https://doi.org/10.11988/ckyyb.20171226

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  To investigate the influence of underlying karst on pile foundation’s bearing capacity, orthogonal tests were simulated in FLAC3D under different karst conditions—five different thicknesses and widths of karst roof, five different heights of karst cave, and three different types of surrounding rock—based on field static load test. Results demonstrated that given the same other circumstances, the bearing capacity of pile foundation is directly proportional to the thickness of cave roof and strength of surrounding rocks, inversely proportional to the width of cave roof, and has no direct relation with cave height. Karst caves and other weak substratum affects the upper pile foundation within a depth maximum to three times pile diameter. Further increasing the thickness of cave roof has little effect on improving the ultimate bearing capacity of pile foundation. Cave size has little effect on pile’s bearing capacity when cave size is close to pile diameter(L≤2D), but reduces the ultimate bearing capacity evidently when cave size continues to grow. The bearing capacity grows apparently with the increase of rock mass strength when the strength is below 11.5 MPa, but the growth is not obvious when the strength is over 11.5 MPa.
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  Unsaturated Wetting Deformation Behavior and Fabric Change of Compacted Loess

  SHAO Xian-xian, ZHANG Hu-yuan, HE Dong-jin, SU Zhen-yan, ZHANG Guo-chao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 82-87,92. https://doi.org/10.11988/ckyyb.20170914

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  To investigate the unsaturated wetting deformation of loess, staged water-saturation test is conducted on loess specimens of different compactness degrees. The critical void ratio for the wetting deformation of compacted loess is proposed by comparing the deformation behaviors of loess among different stages from unsaturated to saturated state. In addition, scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) are adopted to analyze the correlation between wetting deformation behavior and microstructure evolution. Results are concluded as follows: 1) under a constant vertical pressure, the void ratio of loess specimen decreases exponentially with the rising of saturation degree and finally reduces to the critical void ratio when its corresponding initial void ratio is greater than critical void ratio; while when initial void ratio is lower than critical void ratio, void ratio exhibits no change. 2) When the compactness degree is 70%, strong wetting deformation is resulted from large amounts of inner pores with sizes larger than most particle sizes, while loess with a compactness of 90% presents an opposite trend. 3) Under loading and wetting actions, the pore structure of loess with a compactness of 70% varies significantly, with particles getting rounded and particles’ predominant orientation reinforced; while for loess with a compactness of 90%, the pore structure changes slightly with no obvious change in particles’ predominant orientation, and particles tend to be angular due to the weak cementation among particles.
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  Estimating Maximum Dry Density of Gravel Soil by Back Propagation Neural Network Optimized by Genetic Algorithm

  RAO Yun-kang, DING Yu, XU Wen-nian, ZHANG Liang, ZHANG Heng, PAN Bo

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 88-92. https://doi.org/10.11988/ckyyb.20180281

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  A model of estimating the maximum dry density of gravel soil is established to provide reference for controlling the compaction quality of gravel soil projects and selecting the gravel soil which meets engineering requirements. In the light that particle gradation is the crucial factor that determines the maximum dry density of gravel soil, 92 groups of data of gravel soil are collected and obtained, of which full gradation (d₁₀-d₁₀₀) is used as the input variable of back propagation (BP) neural network. Furthermore, genetic algorithm (GA) is adopted to optimize the initial weights and thresholds of the BP neural network, based on which the estimation model for maximum dry density of gravel soil is constructed. In addition, the GA-BP neural network model is compared with BP neural network model. According to estimation results, the mean relative error of the predicted results of 86 groups of training samples is 0.54%, and the coefficient of determination is 0.983; the mean relative error of the predicted results of 6 groups of test samples is 0.57%, which indicates that the proposed model is of good generalization performance. It is concluded that the maximum dry density of gravel soil could be well predicted by applying GA-BP neural network in consideration of full gradation. GA-BP neural network model is superior than conventional BP neural network model in terms of convergence rate, prediction accuracy and generalization performance.
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  Ring-shear Test of Basalt Residual Soil

  ZHANG Lang, LEI Xue-wen, MENG Qing-shan, LI Yong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 93-97. https://doi.org/10.11988/ckyyb.20170850

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  To accurately understand the mechanical properties of soil with large shear displacement, we examined the peak strength and residual strength of basalt residual soil under different shear modes and shear rates using ring shear apparatus to obtain the shear mode and the shear rate suitable for basalt residual soil, and on this basis analyzed the impacts of dry density and moisture content on peak strength and residual strength. Results unveil that specimens with existing shearing surface could reach residual strength state rapidly. As the results of pre-shear and multistage shear are large, we should select single-stage shear. Shear rate has a great influence on peak strength, but the influence on the residual strength is relatively small. Specimens under large shear rate would experience water leakage and soil squeezing, which is liable to cause deviation to the result. Moreover, with the increase of dry density, peak strength increases, while residual strength decreases first and then remains unchanged. The greater the water content, the smaller the peak strength and residual strength. Residual soil of basalt softens obviously when contacting with water. The research results offer reference for the stability analysis and treatment of basalt residual soil slope.
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  Lead-contaminated Soil Solidified by Cement-Flyash-Gypsum- desulphurized:Mechanical Strength Characteristics and Prediction Method

  CUI Jin-yang, WANG Qiang, GONG Bao-ju, YAO Wei-jing

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 98-103. https://doi.org/10.11988/ckyyb.20170904

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  Orthogonal unconfined compression test was conducted on lead-contaminated soil solidified by curing agent CFG (cement mixed with flyash and desulphurized gypsum) to investigate the strength characteristics of treated lead-contaminated soils varying with lead ion concentration and CFG dosage. Results reveal that the unconfined compressive strength of stabilized soils increases with the growth of CFG dosage, while reduces with the climbing of lead ion concentration. In the first seven days of curing, the effect of lead ion concentration is greater than that of curing agent dosage; after seven days, the influence of the dosage of curing agent is greater than that of lead ion concentration. At 3 d and 7 d of curing, the influences of both factors on soil strength are small, while at 14 d the influence greatly increases, and at 28 d, the effect is especially significant. Furthermore, the formula of strength prediction based on curing age and CFG dosage is proposed as a reference for the treatment of lead-contaminated soil.
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  Experimental Study on Shear Behaviors of Interface Between Pile and Marine Clay

  GUO Ju-kun, KOU Hai-lei, XU Hong-lin, LEI Sheng-you

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 104-108,117. https://doi.org/10.11988/ckyyb.20171138

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  The mechanical behaviors of pile foundation are restricted by the shear behavior of pile-soil interface which is of importance for the study of pile-soil interaction mechanism. In this research, shear tests on marine clay-steel interface and marine clay-concrete interface were conducted via an improved direct shear apparatus to investigate the relationship between shear stress and shear displacement of interface with varied water content and consolidation time. Results indicate that relationship between shear stress and shear displacement of interface displayed good elastic-plasticity which can be expressed by hyperbolic model. The peak shear stress and displacement of interface increased with the climbing of normal stress, the declining of water content and the extension of consolidation time. The increment of peak shear stress concentrated within 14 days after consolidation. Moreover, the friction angle and cohesive force of interface decreased with the climbing of water content. Consolidation time had little influence on the friction angle of interface which concentrated in the range from 20 degrees to 23 degrees. The cohesive force of interface increased with the increasing of consolidation time, and such increment concentrated within 14 days after the initiation of consolidation. The research findings provide reference for estimating the resistance during the pile driving stage and for numerical simulation of marine pile foundation engineering.
HYDRAULIC STRUCTURE AND MATERIAL
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  Effect of Multidimensional Load on Permeability of Concrete with Different Moisture Content

  ZHANG Bin, YANG Shuo, ZHOU Jun-xia

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 109-112. https://doi.org/10.11988/ckyyb.20171115

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  The effect of multidimensional load on the permeability of concrete of varied water content is examined in this research by using ZYS-1 coal-rock multifunctional triaxial infiltration apparatus under different test conditions. The change trend of permeability coefficient during the climbing of axial compression, confining pressure, and pore pressure are analyzed, and the curves of permeability coefficient under such conditions are acquired respectively. Results illustrate that the permeability coefficient of concrete is in a negative exponential relationship with axial pressure and confining pressure, but is more sensitive to confining pressure, which is reflected in the swift change of permeability coefficient in the presence of low confining pressure. Under the action of confining pressure or axial compression, the permeability coefficient of concrete tends to be stable, and decreases with the increase of water content and gets less sensitivity to water content. The research findings are of great significance to enhancing the durability of concrete and the long-term performance of bridges.
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  Early Performance and Microstructure of Fly-ash-based Geopolymeric Materials Modified by Soda Residue

  ZHAO Xian-hui, LIU Chun-yuan, ZUO Li-ming, LIU Yu-fei, PANG Yun-ze

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 113-117. https://doi.org/10.11988/ckyyb.20170616

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  Alkali-activated class F fly-ash-based polymer materials (FA-GEO) by NaOH solution has not ideally solidified at room temperature and atmospheric pressure. In this research, the properties of fly-ash-based geopolymer materials are improved by soda residue. The early mechanical properties, microstructure and thermal stability of the modified materials are researched through flexural strength test, compressive strength test, XRD, SEM-EDS, FTIR and TG-DSC test. Results show that the early mechanical properties and microstructure of FA-GEO are significantly improved by soda residue. When soda residue content is 27%, the 60 d compressive strength of mortar increases by 1.4 times. Soda residue reduces the crystallinity of zeolite crystals of FA-GEO. Soluble Ca²⁺ makes the modified gels tend to form a more cohesive calcium-containing zeolite-like phase geopolymer which is particle-shaped. Soda residue promotes the polymerization of Si-O-Al chain and the absorption of Ca²⁺ and Na⁺. The research result could be regarded as a new idea in optimizing FA-GEO.
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  A Rigorous Mass Lumping Scheme for Vibration of Beams

  GAO Dai-heng, GUO Hong-wei, ZHENG Hong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 118-122,139. https://doi.org/10.11988/ckyyb.20170997

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  In the vibration analysis of beam bending problems, none of existing mass lumping schemes that are mathematically rigorous (ignored mass of rotational degree of freedom) are available to maintain the lumped mass matrix symmetric and positive definite up to now, which leads to the difficulty in generating symmetric and positive definite matrix. It has caused great inconvenience to analyses in both the time and frequency domain. Within the framework of the partition of unity (PU), the PU functions and local approximations on the patches are retrieved from Hermitian interpolations via numerical manifold method. Next, the variation principle is integrated using the definition of integral of a scalar function on a manifold to retrieve the diagonal block mass matrix. In addition, compared with consistent mass matrix, our method could achieve higher precision and speed, especially for higher order modes.
INFORMATION TECHNOLOGY APPLICATION
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  An Information Monitoring Platform for County-level Rural Tap Water Safety: Design and Implementation

  WANG Wei-dong, LIU Shu-bo, TU Guo-qing

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 123-128. https://doi.org/10.11988/ckyyb.20171206

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  During the critic period of the 13th five-year plan, information technology as a non-engineering measure becomes increasingly important than engineering measures to consolidate and improve rural tap water safety projects. In this paper, an information monitoring platform for county-level rural tap water safety which could collect and manage the monitoring data from dispersed and heterogeneous SCADA (Supervisory Control and Data Acquisition) systems inside the county area is designed and implemented. By using the registration and negotiation mechanism within directory server, heterogeneous networks can be connected. Meanwhile, messages from heterogeneous network protocols can be resolved and encapsulated by platform communication server middle-wares. As a consequence, issues such as networks’ synchronization and systems’ interconnection can be solved. The platform software has been running stably for more than one year. Result indicates that the platform is beneficial to manage the water plants’ operations more comprehensively in time, to supervise the water-supply industry more completely, to evaluate quality more objectively, and to promote the water-supply guarantee rate.
HE 28TH NATIONAL SYPOSIUM ON GEOTECHNICAL TESTING
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  In-situ Test of Soft Soil in Pearl River Delta: Engineering Practices and Effect Analysis of Result Applications

  CHEN Fu-qiang, YANG Guang-hua, SUN Shu-kai, GUAN Da-shu, ZHU Si-jun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 129-134. https://doi.org/10.11988/ckyyb.20180907

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  In order to expand the application of in-situ testing technology in soft soil projects in the Pearl River Delta and to verify the feasibility of using cross plate shear test result to calculate the shear strength of soft soil, we compared in-situ test results with indoor test results, and analyzed the application effects. We took the in-situ test and its engineering application in a soft soil fill slope in Zhuhai and a foundation pit engineering in Nansha, Guangzhou as engineering examples. Results unveil that in-situ test could well reflect the actual state of soft soil, and the shear strength parameter of soft soil calculated via vane shear test result is greater than those obtained by laboratory soil test. However,in Pearl River Delta region, the cohesion of soft soil calculated by method in Appendix J of Code for Foundation of Port Engineering(JTS 147-1—2010) exceeds empirical range, hence is not suitable for direct use in engineering design. We suggest that further theoretical research on the application of in-situ test data should be conducted to expand its application scope.
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  Mechanical and Micro-structural Characteristics of Coastal Cement Soil Modified by Nano-MgO

  ZHANG Chen, LI Na, WANG Wei, YUAN Jun-ping, JIANG Ping, WU Wang-yi, FU Ke-xian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 135-139. https://doi.org/10.11988/ckyyb.20180910

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  To investigate the effect of nano-MgO on cement-treated seashore soil, mechanical test and microscopic test were conducted on nano-MgO modified cement-treated seashore soil (NmCS). The mechanical performances of NmCS samples with varied cement content and nano-MgO content were examined via indoor direct shear test. Furthermore, the micro-structural characteristics and mechanism were studied by using SEM technology. Test result unveiled that: (1) there exists an optimum content of nano-MgO for NmCS. Specifically in the test of the present research, the optimum content of nano-MgO is 10‰. (2) Cement-treated seashore soil in the absence of nano-MgO is dominated by loose-structure and small particles; while NmCS with 10‰ nano-MgO is the most compact, reflected as in the improvement of mechanical strength.
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  Microstructural Variation Characteristics of Weak Expansive Soils During Hydration

  CHEN Bao, PAN Yan-min, LU Xiao-jun, YU Da

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 140-144,150. https://doi.org/10.11988/ckyyb.20180925

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  One-dimensional swelling tests under different load conditions were conducted to obtain the evolution of Nanyang expansive soil’s microstructure. Samples with initial state and samples swelling under different conditions were freezing-dried to get prepared for Scanning Electron Microscope (SEM) tests and Mercury Intrusion Porosimetry (MIP) test. Then the modification in microstructures and pore size distribution were analyzed. SEM tests show that soil-particle arrangement has no obvious directionality. Samples with initial compacted state and swelling under constant volume are in turbulent flow structures, while samples swelling under 0 or 50 kPa surcharge are of granular structures after reaching steady state. MIP test shows that the pore size distribution curves of samples under different swelling conditions are of three peaks. Pores in soils can be classified into macro-pore, fine-pore, micro-pore and ultra-micro-pore. Compared with initial states, fine-pores in samples swelling under constant volume are compressed into micro-pore. The volumes of all kinds of pores in samples swelling under 0 or 50 kPa surcharge loads all increase as the surcharge loads are larger than the expansive force. In this situation, soil particles can push each other away.
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  Influence of Microstructure on Soil-Water Characteristic Curve of Undisturbed Expansive Soils

  QI Dao-kun, PAN Yan-min, ZHANG Liang

  Journal of Changjiang River Scientific Research Institute. 2019, 36(4): 145-150. https://doi.org/10.11988/ckyyb.20180917

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  The water retention characteristics of Nanyang undisturbed weak expansive soil were tested using the osmotic technique and the vapor phase technique. The hydrating path of soil-water characteristic curve (SWCC) in the suction ranging from 0.01 to 309 MPa was gained and fitted according to a model proposed by Van Genuchten. Scanning Eelectron Microscope (SEM) and Mercury Intrusion Porosimetry (MIP) tests were conducted to analyse the influence of microstructure modification on SWCC. Results showed that during hydrating process, the volume content of micro-pore and macro-pore increased while that of fine-pore decreased. Changes in micro-pore and fine-pore resulted in the continuous absorption of water by soils with no inflection point on the SWCC. The increase of macro-pore mainly influences the boundary effect segment of SWCC, but such influence is slight.