01 May 2019, Volume 36 Issue 5

    

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SPECIAL CONTRIBUTION
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  Optimization of Tunnel Construction Method Based on Grey Fuzzy Multi-attribute Group Decision-making

  XIE Quan-min, DING Xiu-yuan

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 1-6. https://doi.org/10.11988/ckyyb.20190057

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  In an attempt to mitigate engineering safety problems caused by inappropriate construction methods in tunnel construction, an optimization model for tunnel construction method is established based on grey fuzzy multi-attribute group decision-making. The attributes of construction method include construction environment, economic benefit, complexity of construction techniques, construction progress, and mechanized degree. The feasibility of the model is verified by a practical application to the Mila mountain tunnel of Linzhi-Lhasa highway in Tibet. The model could well reflect the emphasis of expert group on different attributes, quantify the decision process, and is proved practical.
RIVER-LAKE SEDIMENTATION AND REGULATION
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  A Parallel Finite-volume Method for Hydrodynamic Modeling of River Network

  SONG Li-xiang, LI Qing-qing, HU Xiao-zhang, YANG Fang, CHEN Wen-long

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 7-12. https://doi.org/10.11988/ckyyb.20171146

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  A hydrodynamic model of complex river network in which the computational cross-sections and reaches are fully decoupled is constructed for river network with dry beds and transition between supercritical and subcritical flows. The MUSCL-Hancock finite-volume scheme is adopted to discrete the Saint-Venant equations, and the method of Junction-Point Water Stage Prediction and Correction (JPWSPC) is used to calculate the hydrodynamic relations at junctions. The OpenMP and OpenACC applications are used to realize CPU-based and GPU-based parallel computing, respectively. Model accuracy is validated by benchmark cases with exact solutions, and the performance of parallel computing is demonstrated by real flood simulation of the Pearl River Delta. Results show that the proposed model is stable and effective, and is applicable for hydrodynamic simulation for steep river, thus has bright application prospects.
WATER RESOURCES AND ENVIRONMENT
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  Current Situation of Tidal Bore in North Branch of the Yangtze River Estuary

  XU Bao-hua, QIAO Hong-jie

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 13-17. https://doi.org/10.11988/ckyyb.20170978

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  In recent years, the implementation of many projects in the north branch of the Yangtze River estuary, such as the regulation project of Xincun shoal and the reclamation project in the middle and lower reach of Haimen reach, have narrowed the river width, changed the boundary condition and river-tidal dynamics of the north branch. In the aim of understanding the characteristics of tidal bores in the north branch, we observed the tidal bores by collecting tide level using self-recording tide gauge, visually observing tide rip on bank, observing flow velocity by buoys, and observing tidal bores on speed boat. We found that tidal bore mainly happens in shallow shoal area including the upper reach of Qinglong harbor and Chonghai ferry dock, with the height of tidal bore reaching 0.63 m and 0.74 m, respectively. In addition, one-line bore still exists in the reach from Lingdian shoal to the upstream shoals of Chonghai ferry dock. By recording the approximate locations of tidal bore’s generation, development, damping and vanishing, and analyzing the origin, type and characteristics of tidal bore, we can provide basic data for researching the interactions between river bed erosion/deposition and special hydrodynamic conditions in the middle and upper reaches of the north branch, and also would offer technical support for further stabilizing the river regime and utilizing the navigation channel in the north branch reasonably.
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  Variation Characteristics of Water Recharge from Changjiang River into Poyang Lake

  CHEN Jin-feng, QIAN Xiao-yan

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 18-22,27. https://doi.org/10.11988/ckyyb.20181255

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  Poyang Lake is a typical lake that links to rivers in the middle and lower reaches of the Changjiang River. The outflow characteristics and water level fluctuation of Poyang Lake are affected by the flow from Ganjiang River, Fuhe River, Xinjiang River, Raohe River, Xiushui River and the Changjiang River, forming a complex hydrological relationship between rivers and lakes. According to hydrological data of the aforementioned five rivers and the control hydrological station of Poyang Lake from 1956 to 2016, we probed into the variations of water recharge from the Changjiang River into Poyang Lake via wavelet analysis and other methods. Research results revealed that the average annual runoff from 2003 to 2016 was lower than that from 1956 to 2002. The volume and number of days of water recharge are both positively correlated with the difference between the streamflow of Hankou Station and the amount of runoff entering Poyang Lake. After 2003, the impounding or releasing of the Three Gorges Reservoir has, to some extent, affected the seasonal changes of the rivers and lakes and the drought and flood opportunities in the Poyang Lake Basin, and further reduced the frequency of water recharge from the Changjiang River into Poyang Lake. In the 1960s, 1980s and early 21st century, the incoming flow from the upper and middle reaches of the Changjiang River exerted strong influence on Poyang Lake; and in the 1970s, 1990s and 2010s, such influence weakened. The research findings are of great significance for understanding the relationship between the Changjiang River and the Poyang Lake under varying circumstances.
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  Removing Cd from Paddy Field Soil with Electric Dehydration Based on Electrokinetic Geotextile

  HU Yan-ping,WANG Zhen-hua,TANG Xian-qiang, LI Qing-yun, HU Yuan

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 23-27. https://doi.org/10.11988/ckyyb.20171169

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  To investigate the rate of removing heavy metal Cd from paddy field soil with electric dehydration based on Electrokinetic geotextile (EKG), a leaching-electric dehydration laboratory simulation experiment was conducted. The variations of pH value of soil and the removal rate of Cd were inspected under different voltage gradients (1,2,3,4,5 V/cm) and electrode spacings (20, 30, 40, 50 cm) after leaching with FeCl₃. Results show that during the electric repair, the pH value of soil fluctuated between 2.2-2.5; the electric removal rate of Cd in soil increased with the climbing of voltage gradient, while decreased with the expansion of electrode spacing, and the removal rate was up to 47%; moreover, the energy consumption per unit of electric removal rate is positively correlated with the voltage gradient and the electrode spacing. The research finding demonstrates that electrokinetic dehydration with EKG as electrode material could control the pH value of soil effectively and promote the efficient removal of movable Cd in pore water of soil.
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  Chemical Characteristics and Water Quality Assessment of Karst Groundwater in Bijie

  ZHANG Shi-xu, WANG Zhong-mei, DAI Tian-hao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 28-33,41. https://doi.org/10.11988/ckyyb.20180050

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  In Bijie of Guizhou Province which is endowed with abundant karst groundwater resource, the unique geochemical background of parent rock carbonate rock gives rise to the special hydrochemistry and groundwater quality. We investigated the hydrochemical features of karst groundwater in Bijie and assessed the water quality in order to find out whether the karst groundwater in this area can be exploited as drinking water resource. According to hydrochemical test results of 22 groups of water samples collected from the study area, we obtained the Piper plot of groundwater’s chemical features via software AqQA and classified the water samples based on Shoka Lev’s classification. Moreover, we assessed the karst groundwater quality in the study area by using single factor evaluation and fuzzy comprehensive evaluation. Results unveil that the hydrochemical types of the study area are chiefly HCO₃-Ca·Mg, distributing in the west and south parts of the study area, with the hardness of carbonate in most areas greater than 50%. Single factor evaluation demonstrates that standard-meeting groundwater quality in the study area reaches 59.1%, whereas fuzzy comprehensive evaluation suggests that standard-meeting groundwater quality amounts to 81.8%. In general, groundwater resources in the study area can be exploited as drinking water resource. The findings of this study offer technical guidance for the exploitation of karst groundwater resources in this area.
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  Characteristics of Rainfall Amount Variations in Wet and Dry Partitions of China from 1971 to 2010

  ZHAO Yu-ming, QIU Xin-fa, ZHU Xiao-chen, XU Jin-qin

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 34-41. https://doi.org/10.11988/ckyyb.20180002

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  According to daily rainfall data at 743 meteorological stations from 1971 to 2010, we classified annual rainfall amount and rainfall days by grade and further discussed the variation characteristics of rainfall amount and rainfall days and the temporal evolution of annual rainfall in four regions (arid region, semi-arid region, semi-humid region and humid region) via linear trend analysis, accumulative anomaly, M-K test and moving-t test. Results demonstrated that (1) in the past four decades, the annual rainfall days differed among the four regions, among which the humid area experienced more days of rainfall in the middle but less in the surroundings. (2) In the north part of arid region, light rainfall contributed more with high frequency, whereas in semi-arid regions, heavy rain and rainstorm contributed less with lower frequency. (3) In terms of interdecadal change, the annual rainfall amount during 1991-2000 increased most remarkably in humid region, yet not obviously in 2001-2010 in semi-humid region. (4) The trend of abrupt change of rainfall amount was inconsistent between wet and dry regions: in humid region the rainfall amount declined abruptly in 2002, while in semi-arid region no abrupt change happened.
HYDRAULICS
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  Technique of Fish Inducing and Expelling by Light and Sound: Research Status and Application Prospect

  LIU Zhi-xiong, ZHANG Di-yan, YANG Wen-jun, LIU Huo-jian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 42-48,61. https://doi.org/10.11988/ckyyb.20171179

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  Technique of fish inducing and expelling by light and sound is of great value and far-reaching significance in ensuring the smooth migration of fishes. Light and sound have an important effect on the behavior characteristics of fish. Different light and sound conditions will make fish behave differently. The physiological basis of the technique of fish inducing and expelling by light and sound is presented, and the factors affecting the phototaxis and phonotaxis of fishes are discussed. By analysing relevant projects and researches over years, we summarize the research status and propose the application prospect in this regard, and point out that light and sound can be combined for oriented fish inducing. Moreover, research on fish’s responses to the illuminance and photochromic of light and the volume and frequency of sound should be strengthened.
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  Failure Mechanism of Pressurized Expansive Water Seal and Countermeasures

  HE Chang-hai, FEI Wen-cai, ZHANG Hong-zhi, WANG Dan-bai

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 49-54. https://doi.org/10.11988/ckyyb.20171056

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  Pressurized expansive water seal is widely applied to weep holes of high head in water conservancy project. Due to many reasons, radial gate may suffer from leakage or even failure of the water seal and adapting pieces. Taking an actual project for example, most M20 stainless steel bolts on the bottom water clamping plate rotated out and were washed away in the first flood season after operation; in the second flood season, the bolts still fractured even after enlargement of the diameter of bolts (from M20 to M27) and improvement of bolts grade (from A2-70 to 10.9). In view of this, we investigated the hydraulic characteristics in the vicinity of the bottom water seal of the working radial gate via physical model test. Results unveiled that negative pressure and cavitation induced by high-velocity flow and resonance generated by flow-excited vibration are major causes of the failure of water seal system. Furthermore, through scheme optimization, we proposed an engineering countermeasure, which is to arrange baffle sill in the downstream reach near the slope of the gate slot. Test results demonstrated that flow condition in the exit segment has improved remarkably, negative pressure of water seal vanished, and flow cavitation number increased, implying evident energy dissipation and corrosion reduction effects. In addition, we recommend rigid connection instead of elastic connection between the clamping plate and the base plate in order to avoid resonance of the water seal system by keeping the natural frequency of the water seal system far from the dominant area of frequency distribution of fluctuating pressure. The research findings offer reference for the design and fault treatment of water seal system of radial gate.
ENGINEERING SAFETY AND DISASTER PREVENTION
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  Investigation on Characteristics of Gully Erosion Caused by the July 4, 2013 Co-seismic Debris Flows in Shimian County, Sichuan Province

  QU Yong-ping

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 55-61. https://doi.org/10.11988/ckyyb.20171232

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  At 20:00 on July 4, 2013, large-scale co-seismic debris flows broke out in Shimian County, Sichuan Province. Affected by the earthquake which hit Lushan County in April, the region is stricken with abundant debris flow sources, of which the sources in debris flow gullies takes up over 64% of the total. Investigating the erosion characteristics in debris flow gullies is of crucial and imperative significance to understanding the development of debris flows in the study area. According to field investigation of the cross sections of three typical co-seismic debris flow gullies in the study area, namely, Hougou gully, Majingzi gully, and Xiongjia gully, we examined the relationship among flow depth, erosion thickness, relative height difference between profiles, and original gully width. For the first time we present the concept of flow direction difference based on curvature radius, and obtained the coefficient of average linear function between erosion thickness and flow direction difference as 0.06, and the coefficient of average linear function between erosion thickness and profile height difference as 0.09. The relationship between erosion and flow depth is h=5Δh+1.798×10^-15, while thickness erosion volume per unit distance and gully width is ΔV=6.845D^0.625. The research findings offer basis for understanding the erosion characteristics of debris flow gullies in the earthquake-stricken area.
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  A Time Series Prediction Model of High Slope Displacement Based on Support Vector Machine and Elman Neural Network

  LIU Chong, SHEN Zhen-zhong, GAN Lei, DANZENG Chi-lie, YAN Zhong-qi

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 62-68. https://doi.org/10.11988/ckyyb.20171018

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  A new displacement time series predicting model was proposed by integrating support vector machine (SVM) and Elman neural network, named as SVM-Elman model. In the process of measured displacement data learning, by searching the best historical step and the best prediction step, SVM model was optimized by particle swarm algorithm to dynamically forecast the trend of development. In the meantime, Elman neural network has the ability of dynamically reflecting the development trend of the absolute error of SVM model prediction. By comparing the influence of different hidden layers of Elman neural network on the prediction results, the optimal number of hidden layer was determined for SVM-Elman model and hence modifying the predicted data of SVM in real time. The proposed SVM-Elman model was applied to the strong unloading high slope on the left bank of a concrete face rockfill dam, and the prediction result was compared with that of conventional SVM. Results demonstrate that the proposed model has superior accuracy and real application value in predicting the deformations of high slope.
ROCK-SOIL ENGINEERING
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  Effect of Pore Water Pressure on Dynamic Stability of Slope under Seismic Action

  ZHAO Lan-hao,ZHOU Chao,FENG Yan,HOU Shi-chao

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 69-74. https://doi.org/10.11988/ckyyb.20171214

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  The influence of pore water pressure on the dynamic stability of slope under seismic action is studied in this paper with a reservoir dam as research object. The temporal changes of seepage field caused by seismic load are analyzed first, and then the stability of dam slope is investigated by coupling the stress field with the seepage field. Finite element method is used to analyze seepage field and vibration field, while limit equilibrium method is used to analyze slope stability. Results demonstrate that seismic action stimulates the increase of excess pore water pressure, and whether to consider the coupling effect of seismic load and pore pressure change will make the results of stability analysis quite different. When the coupling effect is not considered, the slope is prone to shallow sliding, with flat sliding surface; as a result, the seismic stability of dam slope is overestimated. On the contrary, when the coupling effect is taken into account, the position of slip surface is obviously deeper, which easily leads to deep sliding. The cumulative effect of pore pressure may be the crucial factor of the dynamic instability of two-phase media slopes. In conclusion, pore water pressure under seismic action plays an important role in the analysis of slope dynamic stability.
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  Analytical Solution for Consolidation of Composite Ground under Vacuum-surcharge Preloading

  ZHANG Yu-guo, YANG Han-yue, DUAN Meng-meng, SHI Xiao-jie, ZHANG Wei-jie

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 75-80. https://doi.org/10.11988/ckyyb.20170945

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  Aiming at the consolidation problem of composite ground with granular columns, the calculation model for the consolidation of composite foundation in consideration of vacuum-surcharge preloading and uniform distribution of initial excess pore water pressure is established. The general analytical solution for the consolidation of composite ground under vacuum-surcharge preloading is given, and the variation regularity of excess pore pressure and consolidation degree is discussed. Research findings demonstrate that the excess pore pressure and consolidation degree of composite ground are much more affected by pile diameter ratio (n), disturbance area (s), loading method and time factor (T_h). The greater the values of n and s are, the greater the excess pore pressure is, and the slower the consolidation is; the greater the load is, the greater the excess pore pressure is. Excess pore pressure rises as depth increases, and such increase is more apparent in the shallow part of the foundation, while attenuates in the deep. The effects of vacuum loading and surcharge loading can be superimposed. In addition, the changes of time factor (T_h) have important influence on the distribution law of excess pore water pressure: excess pore pressure distributes linearly in the shallow part of the foundation, but distributes nonlinearly when depth exceeds a certain value, and such nonlinearity gets more evident when the value of T_h is larger.
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  Validation of Spraying Method for Precisely Preparing Compacted Bentonite Samples with Target Water Content

  MING Hua-jun, KE Rui, WANG Hong-xing

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 81-85,90. https://doi.org/10.11988/ckyyb.20171128

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  To investigate the reliability of spraying method for precisely preparing compacted bentonite samples with target water content, the water content at both upper and lower parts of compacted specimen was measured. Since orthogonal test method could reduce test times and shorten test cycles, nine orthogonal experiments were designed to study the influences of added water quantity (target water content), curing time, and compaction force on water content, with the help of the orthogonal table. Results imply that specific abnormal data indicates that the spraying method is artificial in the process of compounding, hence should be removed firstly. Moreover, with the increase of water addition, water content at both upper and lower parts of the compacted specimen decreased to be smaller than the target water content; local agglomeration was weakened, and water loss intensified. Curing time and compaction force have significant influences on the uniformity of water content in compacted specimens. As the spraying method is superior to other methods in terms of time, it is worth recommending after abnormal test data are removed. Nevertheless, due to the water loss in the process of bentonite mixing, the actual water content of compacted samples should be corrected before further use.
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  Model of Estimating Bulging Deformation of Expansive Soil Subgrade

  BIAN Jia-min,CAI Xiao-fei

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 86-90. https://doi.org/10.11988/ckyyb.20171123

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  In the aim of providing reference for the design and construction of expansive soil fill in subgrade, the calculation method for the bulging deformation of expansive soil was analyzed. First of all, one-dimensional linear expansive ratio test on weak expansive soil of different initial dry density under varying overburden pressure was conducted, and the law of moisture equilibrium of expansive soil fill in subgrade was expounded. With reference to the results of one-dimensional linear expansive ratio obtained by other scholars, the concepts of relative overburden pressure and relative deformation were put forward. Test results unveiled that the relative linear expansive deformation was in a power exponential relation with relative overburden pressure. In addition, the wet expansive deformation model was established and a practical calculation method for bulging deformation of expansive soil fill in subgrade was proposed to solve the coupling problem of three factors for the linear expansive ratio of expansive soil.
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  Parametric Analysis of Buckling Stability of Extra-long Pile Based on Energy Method

  YANG Song, ZHANG Li, LI Li-chen, ZHANG Jing-kun, LIANG Rong-zhu, WU Wen-bing

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 91-98. https://doi.org/10.11988/ckyyb.20171405

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  The buckling stability of extra-long pile which has been increasingly used in high-rise buildings has emerged as a crucial engineering issue. In this research, the formula of critical buckling load of extra-long pile is acquired via energy approach by establishing a model in which the soil resistance is calculated by combining the C method and the constant number method. The self-weight together with side frictional resistance of pile is taking into consideration. Furthermore, the impacts of influential factors on the buckling stability are examined. Results reveal that the influences of unit side friction and self-weight of extra-pile are negligible. The more the number of flexural function items and the smaller the soil resistance, the smaller the buckling critical load is; the larger the pile length and diameter, the larger the buckling critical load is; and the larger the ground soil proportion coefficient, the greater the critical buckling load is. Therefore, in terms of the buckling stability of extra-long pile, large-size extra-long piles have the greatest performance against buckling failure when applied to hard foundations.
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  A Method of Predicting Long-term Deformation of Clay Based on Rate Sensitivity

  WANG Zhi-chao, HU Qian, ZHENG Jun-xing, XIONG Yun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 99-103,115. https://doi.org/10.11988/ckyyb.20171237

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  The prediction and control of the long-term deformation of clay is a crucial problem in the construction of a large quantity of projects. Predicting clay deformation conventionally via creep test is time-consuming, challenging in considering complex stress path, and also unsuitable for complicated finite element analysis. In this paper, the strength, deformation and rate sensitivity of saturated over-consolidated clay and artificial structural clay were obtained via triaxial shear tests under three different loading rates. On this basis, parameters of an elastic-viscoplastic constitutive model based on super-subloading surface were obtained, and the rate sensitivity and creep deformation of clay were estimated by the model. Results revealed that: 1) compared with conventional triaxial test, predicting the long-term deformation of clay in association with rate sensitivity test is highly efficient with only several shear test at different loading rates added yet no additional test conditions; 2) the parameters of the constitutive model determined by rate sensitivity test can be used to predict the creep deformation of clay correctly, and the prediction results are in good agreement with test results; 3) the elastic-viscoplastic constitutive model based on super-subloading surface can be embedded in finite element program to calculate the complex boundary value problems. In conclusion, the presented method of long-term deformation prediction of clay is of sound value in engineering application.
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  Triaxial Tests on Municipal Solid Waste Incineration Bottom Ash

  ZHANG Pan, XU Yong-fu

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 104-107. https://doi.org/10.11988/ckyyb.20171291

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  As the product of municipal solid waste incineration (MSWI), bottom ash can be used as subgrade cushion material by replacing aggregate to achieve the secondary utilization of resources. To investigate its shear strength and deformation properties, triaxial consolidated drained tests were performed on saturated bottom ash with different dry density (ρ_d=1.4,1.5,1.6g·cm^-3) at different curing ages (t=3,7,14,28 d). Shear strength parameters (cohesion and internal friction angle) of MSWI bottom ash are determined via Lambe plane approach. Results unveil that the stress-strain curve of MSWI bottom ash under low confining pressure (100 kPa and 200 kPa) displays strain softening characteristic, and hardening feature under higher confining pressure (200 kPa and 400 kPa). Peak shear strength increases logarithmically with curing age, namely peak shear strength grows rapidly in the early stage (before the first 14 days), and in subsequence slows down. Cohesion and internal friction angle present different trends with curing age: cohesion increases with curing age, while internal friction angle remains almost unchanged.
HYDRAULIC STRUCTURE AND MATERIAL
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  Finite Element Modeling of Leakage Dissolution of Cement-based Materials

  JIA Pan, SHE Cheng-xue

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 108-115. https://doi.org/10.11988/ckyyb.20180173

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  Leakage dissolution which exists extensively in water conservancy projects in China and abroad has not been well revealed by numerical simulation. In view of this, with respect to leakage dissolution of cement-based materials, a research on finite element analysis method is conducted. Firstly, on the basis of the mechanism of hydrodynamic dispersion and convection of ions in cement-based materials, a three-dimensional mathematical model of Ca²⁺ ion transport during leakage dissolution is developed according to the mass conservation law of ion, the Fick’s second law, mathematical model of flow in porous media and Darcy’s law. In subsequence, a three-dimensional mathematical model of leakage dissolution of cement-based materials is established based on the aforementioned Ca²⁺ ion transportat model, the solid-liquid equilibrium curve, the porosity evolvement model and the diffusion coefficient evolvement model. Meanwhile, the finite element method for this model is given. Finally, the proposed model is validated by numerical simulation of leakage dissolution test under high hydraulic gradient. The simulated result is consistent with the experimental result, which demonstrates that the proposed model can be used to simulate the process of leakage dissolution of cement-based materials. The research lay a foundation for the modeling of leakage dissolution in water resources and hydropower engineering, and is of great significance to the study of structural safety of water resources and hydropower projects.
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  Evaluation of Mechanical and Thermal Properties of Low-heat Cement Binding System

  JIANG Chun-meng, GONG Jing-wei, TANG Xin-jun

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 116-120,127. https://doi.org/10.11988/ckyyb.20171207

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  The mortar strength and hydration heat in different ages of low-heat cement material are investigated and an evaluation function of its mechanical and thermal properties is established by limited upper (or lower) bound linear rule to provide reference for the application of low-heat cement to mass concrete. On this basis, the satisfaction on the comprehensive performance of cementitious materials is calculated to draw a satisfaction contour map. Research results show that: the contours of satisfaction on comprehensive performance of low-heat cement cementitious system can be approximated as a series of concentric elliptical lines, and the cementitious material system with fly ash content in and slag content in has high comprehensive performance for lower hydration heat and higher strength. The combination of evaluation function and satisfaction contour map provides a new idea for the comprehensive performance evaluation of composite cementitious material system.
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  Analyzing Anti-seepage Performance of Dam Foundation Curtain Based on Hydrogeochemistry

  LIU Sheng,YU Bo, ZHENG Ke-xun, MA Cong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 121--127. https://doi.org/10.11988/ckyyb.20171055

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  By employing the Darcy’s law analytic expression expressed by hydrochemical indicators proposed by previous researchers for calculating hydrogeological parameters on theoretical basis of chemical thermodynamics, chemical kinetics, hydrogeochemistry, hydrogeology, and mineral dissolution kinetics, we calculated the permeability coefficient of seepage curtain in a compound dam foundation, and also the saturation index of calcite, dolomite, and gypsum in the water environment of dam site in full consideration of the impacts of complex compound in water. We analyzed the suitability and rationality of applying this method to seepage curtain by comparing the calculation results with in-situ permeability test results together with seepage control value, seepage amount, water pressure, and precipitation behind the curtain, and on this basis further evaluated the status of seepage curtain. Results demonstrate that permeability coefficient calculated by water quality indicators could well reflect the seepage status of grouting curtain. This paper is of referential value for evaluating the anti-seepage performance of grouting curtain in similar projects.
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  Ideal Elasto-plastic Solution of High-strength Shaft Lining Based on Weighted Double Shear Strength Theory

  YANG Long, YAO Zhi-shu, XUE Wei-pei

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 128-134. https://doi.org/10.11988/ckyyb.20171482

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  An ideal elasto-plastic solution of thick-walled cylinder is presented to acquire the ultimate bearing capacity of high-strength shaft lining based on the weighted double shear unified strength theory in consideration of different intermediate principal stress effects. In one case, under external pressure p₀,thick-walled cylinder is in full elastic state, but changes to elasto-plastic state when axial compression P is applied; in another case, only under external pressure p₀, thick-walled cylinder is in elasto-plastic state. Moreover, the formula of elasto-plastic stress solution, the formula of elasto-plastic ultimate bearing capacity, and the expression of the radius of plastic zone are obtained based on the weighted double shear unified strength theory, and the applicable conditions of different intermediate principal stresses are given. The aforementioned formula of ultimate bearing capacity is modified for C70 concrete shaft lining. Compared with the test value, the error of the ultimate bearing capacity calculated by the modified formula is about ±3%. In summary, the modified formula of ultimate bearing capacity is of guiding significance for the optimal design of shaft lining structure and model test results.
TECHNOLOGY FOR UNDERGROUND WATER-SEALED CAVERN OF ZHANJIANG NATIONAL CRUDE OIL STORAGE PROJECT
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  Test Methods of Bond Strength Between Shotcrete and Surrounding Rock in Underground Oil Storage in Rock Cavern

  LUO Rong, ZHANG Yi-hu, XIANG Qian, JIANG Jian-jun, GAO Xi-min,SUN Xiao-min

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 135-140. https://doi.org/10.11988/ckyyb.20181370

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  Currently recognized as the best form of oil storage, underground oil storage in rock cavern is supported only by bolt-shotcrete without lining. Bond strength plays an important role in transmitting stress to ensure the collaborative work between shotcrete and surrounding rock; as a result, bond strength is an important indicator for analyzing and evaluating the structural stability and construction quality in underground oil storage in rock cavern.In this research, several kinds of methods were adopted to test the bond strength between shotcrete and surrounding rock in a underground oil storage in rock cavern in south China. Results suggest that in-situ tensile method by drilling shotcrete specimen with a diameter of 50 mm is not suitable for underground oil storage in rock cavern. When the diameter of test specimen is increased to 100 mm, the success rate of specimen production for in-situ tensile test has greatly improved, and the tensile test results are reliable as the lower limiting value of bond strength. Meanwhile, result of laboratory tensile test by cutting panel-formed shotcrete with rock block is adopted as the upper limiting value of bond strength. In summary, the aforementioned two methods, namely, in-situ tensile method by drilling shotcrete specimen with a diameter of 100 mm, and tensile test by cutting panel-formed shotcrete with rock block, are recommended to evaluate the bond strength comprehensively. In other words, the results of the former could be referenced as the lower limiting value of bond strength and the results of the latter as the upper one. The research findings offer important application reference for the structural stability and construction quality in underground oil storage in rock cavern.
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  Research Status and Thinking about Underground Oil Storage in Rock Caverns in China

  QIN Zhi-yong, GAO Xi-min

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 141-148. https://doi.org/10.11988/ckyyb.20181142

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  Considered as the best way to store oil, underground oil storage in rock caverns is in urgent need for the national petroleum reserve. Subject to the technical blockade of foreign countries, many large caverns in China are directly undergoing engineering practice with no technical standards or construction standards, posing a great deal of challenges. By sorting out literatures on water-sealed oil storage caverns, we discuss in this paper our theoretical and practical understandings of such key technologies as site selection of water-sealed oil storage caverns, stability of surrounding rock, permeability of surrounding rock, design and application of water curtain system, and seepage control. Current survey, design, and construction are mainly based on the continuum theory and methods, and understanding on rock fissure control is insufficient, resulting in the difficulties of constructing water-sealed caverns. In light of problems in current engineering practice, we suggest that fundamental research should be intensified, summaries and standard compiling should be strengthened, and admittance qualification of the industry should be furthered opened.
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  Load-bearing Characteristics of Bolt-Shotcrete Support System for Underground Oil Storage in Rock Caverns

  QIN Zhi-yong,GAO Xi-min,CHENG Chuan-huan,XIANG Qian

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 149-154. https://doi.org/10.11988/ckyyb.20180583

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  The stress of support system and the load-bearing characteristics between shotcrete and rock are research focuses in the excavation of underground oil storage in rock caverns. In this paper, the deformation and stability of cavern and the stress condition of the support system are studied though simulating the excavation of underground caverns by finite element software ANSYS. Furthermore, the work condition of shotcrete and rock is discussed by incorporating thin layer element in the simulation with the bond strength between surrounding rock mass and shotcrete into consideration. Research reveals that the deformation of surrounding rock is relatively small with linear elastic deformation due to good integrity and high strength. The support system should be completed in time to prevent from local falling resulting from joints. Sensitivity analysis shows that under the action of water pressure, when the bond strength between surrounding rock and shotcrete is less than 0.6 MPa, shotcrete begins to separate from the side walls, and when bond strength is less than 0.5 MPa, more separated area appear even in the vaults. Therefore the construction quality of shotcrete should be noted and field adhesion test should be intensified.
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  A Method of Optimizing Axis Direction of Underground Water-sealed Storage Cavern

  CAO Yang-bing, CHEN Yu-hua, HUANG Zhen-ping, LIU Cheng-yu, QIU Dong-dong

  Journal of Changjiang River Scientific Research Institute. 2019, 36(5): 155-162. https://doi.org/10.11988/ckyyb.20190012

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  The axis direction of underground water-sealed cavern plays a pivotal role in surrounding rock stability, support costs, and construction safety. We present a comprehensive optimization method together with evaluation indexes for the axis direction of cavern in line with engineering characteristics of underground water-sealed cavern. Firstly, we determined the optional range of axis direction according to specifications in China. Subsequently, we determined the optimal axis direction in equivalent continuum model and in discontinuous medium model, respectively, with evaluation indicators including the maximum displacement of surrounding rock, the volume of plastic zone, the stability coefficient, and the maximum shear displacement on joint surface. Afterwards, we determined the optimal axis direction of cavern with support pressure as evaluation index based on key block theory. Finally, we obtained the optimal axis direction comprehensively through holistic analysis of the calculation result of each index. Research findings suggest that the numerical model should include the excavation face to reflect the safety of construction process. In the determination of stability coefficient of surrounding rock based on strength reduction method, we should select the abrupt change point on the displacement-reduction factor curve as the critical stability coefficient rather than by calculating misconvergence. The present method has been proved to be feasible and reliable in application to an underground water-sealed cavern project in Shandong Province.