Water Science and Engineering - 开云电竞网

Application of hydrological models in a snowmelt region of Aksu River Basin

Ouyang Rulin, Ren Liliang, Cheng Weiming, Yu Zhongbo — 2008-12-30

Ouyang Rulin, Ren Liliang, Cheng Weiming, Yu Zhongbo This study simulated and predicted the runoff of the Aksu River Basin, a typical river basin supplied by snowmelt in an arid mountain region, with a limited data set and few hydrological and meteorological stations. Two hydrological models, the snowmelt-runoff model (SRM) and the Danish NedbØr-AfstrØmnings rainfall-runoff model (NAM), were used to simulate daily discharge processes in the Aksu River Basin. This study used the snow-covered area from MODIS remote sensing data as the SRM input. With the help of ArcGIS software, this study successfully derived the digital drainage network and elevation zones of the basin from digital elevation data. The simulation results showed that the SRM based on MODIS data was more accurate than

NAM

. This demonstrates that the application of remote sensing data to hydrological snowmelt models is a feasible and effective approach to runoff simulation and prediction in arid unguaged basins where snowmelt is a major runoff factor Water Science and Engineering. 2008 1(4): 1-13 .

Numerical algorithm of distributed TOPKAPI model and its application

Deng Peng, Li Zhijia, Liu Zhiyu — 2008-12-30

Deng Peng, Li Zhijia, Liu Zhiyu The TOPKAPI (TOPographic Kinematic APproximation and Integration) model is a physically based rainfall-runoff model derived from the integration in space of the kinematic wave model. In the TOPKAPI model, rainfall-runoff and runoff routing processes are described by three nonlinear reservoir differential equations that are structurally similar and describe different hydrological and hydraulic processes. Equations are integrated over grid cells that describe the geometry of the catchment, leading to a cascade of nonlinear reservoir equations. For the sake of improving the model’s computation precision, this paper provides the general form of these equations and describes the solution by means of a numerical algorithm, the variable-step fourth-order Runge-Kutta algorithm. For the purpose of assessing the quality of the comprehensive numerical algorithm, this paper presents a case study application to the Buliu River Basin, which has an area of 3 310 km², using a DEM (digital elevation model) grid with a resolution of 1 km. The results show that the variable-step fourth-order Runge-Kutta algorithm for nonlinear reservoir equations is a good approximation of subsurface flow in the soil matrix, overland flow over the slopes, and surface flow in the channel network, allowing us to retain the physical properties of the original equations at scales ranging from a few meters to 1 km Water Science and Engineering. 2008 1(4): 14-21 .

Critical interfaces in geosynthetic multilayer liner system of a landfill

Qian Xuede — 2008-12-30

Qian Xuede This study is to identify the critical interface in a geosynthetic multilayer liner system by examining the effects of the interface shear strength of liner components, leachate level, leachate buildup cases, and peak and residual interface strengths. According to current landfill design procedures, conducting stability analysis along the same interface at both the back slope and base may result in a non-conservative result. The critical interfaces with the minimum factor of safety are generally found at different locations along the back slope and base. The critical interface for a multilayer liner system cannot simply be assumed during stability analysis. It can shift from one interface to another with changes in the leachate level and with different leachate buildup cases. The factor of safety for an interface with a high friction angle and low apparent cohesion generally drops much more quickly than it does under inverse conditions when the leachate level increases. The failure interface in a liner system under residual conditions is usually different from the failure interface under peak conditions. Water Science and Engineering. 2008 1(4): 22-35 .

Fuzzy stochastic generalized reliability studies on embankment systems based on first-order approximation theorem

Wang Yajun, Zhang Wohua, Jin Weiliang, Wu Changyu, Ren Dachun — 2008-12-30

Wang Yajun, Zhang Wohua, Jin Weiliang, Wu Changyu, Ren Dachun In order to address the complex uncertainties caused by interfacing between the fuzziness and randomness of the safety problem for embankment engineering projects, and to evaluate the safety of embankment engineering projects more scientifically and reasonably, this study presents the fuzzy logic modeling of the stochastic finite element method (SFEM) based on the harmonious finite element (HFE) technique using a first-order approximation theorem. Fuzzy mathematical models of safety repertories were introduced into the SFEM to analyze the stability of embankments and foundations in order to describe the fuzzy failure procedure for the random safety performance function. The fuzzy models were developed with membership functions with half depressed gamma distribution, half depressed normal distribution, and half depressed echelon distribution. The fuzzy stochastic mathematical algorithm was used to comprehensively study the local failure mechanism of the main embankment section near Jingnan in the Yangtze River in terms of numerical analysis for the probability integration of reliability on the random field affected by three fuzzy factors. The result shows that the middle region of the embankment is the principal zone of concentrated failure due to local fractures. There is also some local shear failure on the embankment crust. This study provides a referential method for solving complex multi-uncertainty problems in engineering safety analysis Water Science and Engineering. 2008 1(4): 36-46 .

Mode-I fracture and durability of FRP-concrete bonded interfaces

Qiao PizhongXu Yingwu — 2008-12-30

Qiao PizhongXu Yingwu In this study, a work-of-fracture method using a three-point bend beam (3PBB) specimen, which is commonly used to determine the fracture energy of concrete, was adapted to evaluate the mode-I fracture and durability of fiber-reinforced polymer (FRP) composite-concrete bonded interfaces. Interface fracture properties were evaluated with established data reduction procedures. The proposed test method is primarily for use in evaluating the effects of freeze-thaw (F-T) and wet-dry (W-D) cycles that are the accelerated aging protocols on the mode-I fracture of carbon FRP-concrete bonded interfaces. The results of the mode-I fracture tests of F-T and W-D cycle-conditioned specimens show that both the critical load and fracture energy decrease as the number of cycles increases, and their degradation pattern has a nearly linear relationship with the number of cycles. However, compared with the effect of the F-T cycles, the critical load and fracture energy degrade at a slower rate with W-D cycles, which suggests that F-T cyclic conditioning causes more deterioration of carbon fiber-reinforced polymer (CFRP)-concrete bonded interface. After 50 and 100 conditioning cycles, scaling of concrete was observed in all the specimens subjected to F-T cycles, but not in those subjected to W-D cycles. The examination of interface fracture surfaces along the bonded interfaces with varying numbers of F-T and W-D conditioning cycles shows that (1) cohesive failure of CFRP composites is not observed in all fractured surfaces; (2) for the control specimens that have not been exposed to any conditioning cycles, the majority of interface failure is a result of cohesive fracture of concrete (peeling of concrete from the concrete substrate), which means that the cracks mostly propagate within the concrete; and (3) as the number of F-T or W-D conditioning cycles increases, adhesive failure along the interface begins to emerge and gradually increases. It is thus concluded that the fracture properties (i.e., the critical load and fracture energy) of the bonded interface are controlled primarily by the concrete cohesive fracture before conditioning and by the adhesive interface fracture after many cycles of F-T or W-D conditioning. As demonstrated in this study, a test method using 3PBB specimens combined with a fictitious crack model and experimental conditioning protocols for durability can be used as an effective qualification method to test new hybrid material interface bonds and to evaluate durability-related effects on the interfaces. Water Science and Engineering. 2008 1(4): 47-60 .

Time-dependent water permeation behavior of concrete under constant hydraulic pressure

Fang Yonghao, Wang Zhongli, Zhou Yue — 2008-12-30

Fang Yonghao, Wang Zhongli, Zhou Yue In the present work, a concrete permeability testing setup was designed to study the behavior of hydraulic concrete subjected to constant hydraulic pressure. The results show that when concrete is subjected to high enough constant hydraulic pressure, it will be permeated, and after it reaches its maximum permeation rate, the permeability coefficient will gradually decrease towards a stable value. A time-dependent model of permeability coefficient for concrete subjected to hydraulic pressure is proposed. It is indicated that the decrease of the permeability coefficient with permeation time conforms well to the negative-exponential decrease model. Water Science and Engineering. 2008 1(4): 61-66 .

Influence of shrinkage-reducing admixture on drying shrinkage and mechanical properties of high-performance concrete

Nguyen QuangphuJiang Linhua, Liu Jiaping, Tian Qian, Do Tienquan — 2008-12-30

Nguyen QuangphuJiang Linhua, Liu Jiaping, Tian Qian, Do Tienquan High-performance concrete (HPC) has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios (m_W/m_B) in the range of 0.2-0.4, so volume changes of concrete as a result of drying, chemical reactions, and temperature change cannot be avoided. For these reasons, shrinkage and cracking are frequent phenomena. It is necessary to add some types of admixture for reduction of shrinkage and cracking of HPC. This study used a shrinkage-reducing admixture (SRA) for that purpose. Concrete was prepared with two different m_W/m_B (0.22 and 0.40) and four different mass fractions of SRA to binder (w(SRA) = 0%, 1%, 2%, and 4%). The mineral admixtures used for concrete mixes were: 25% fly ash (FA) and 25% slag by mass of binder for the mixture with m_W/m_B = 0.40, and 15% silica fume (SF) and 25% FA for the mixture with m_W/m_B = 0.22. Tests were conducted on 24 prismatic specimens, and shrinkage strains were measured through 120 days of drying. Compressive strength, splitting strength, and static modulus of elasticity were also determined. The results show that the SRA effectively reduces some mechanical properties of HPC. The reductions in compressive strength, splitting tensile strength, and elastic modulus of the concrete were 7%-24%, 9%-19%, and 5%-12%, respectively, after 90 days, compared to concrete mixtures without SRA. SRA can also help reduce drying shrinkage of concrete. The shrinkage strains of HPC with SRA were only as high as 41% of the average free shrinkage of concrete without SRA after 120 days of drying. Water Science and Engineering. 2008 1(4): 67-74 .

Evaluation of urban river landscape design rationality based on AHP

Qiao Lifang, Zhang Yichuan, Cao Wei — 2008-12-30

Qiao Lifang, Zhang Yichuan, Cao Wei An evaluation model for the rationality of the landscape design of urban rivers was established with the analytic hierarchy process (AHP) method so as to provide a foundation for updating the landscape design of urban rivers. The evaluation system was divided into four layers, including the target layer, the comprehensive layer, the element layer, and the index layer. Each layer was made of different indices. The evaluation standards for each index were also given in this paper. This evaluation model was proved tenable through its application to the landscape design rationality evaluation of the Weihe River in Xinxiang City of Henan Province. The results show that the water quality, space, activity, facility, community, width of vegetation, sense of beauty and water content are among the most influential factors and should be considered the main basis for evaluating the rationality of the landscape design of urban rivers. Water Science and Engineering. 2008 1(4): 75-81 .

R/S method for evaluation of pollutant time series in environmental quality assessment

Bu Quanmin, Bi Jun, Yuan Zengwei, Huang Lei — 2008-12-30

Bu Quanmin, Bi Jun, Yuan Zengwei, Huang Lei The significance of the fluctuation and randomness of the time series of each pollutant in environmental quality assessment is described for the first time in this paper. A comparative study was made of three different computing methods: the same starting point method, the striding averaging method, and the stagger phase averaging method. All of them can be used to calculate the Hurst index, which quantifies fluctuation and randomness. This study used real water quality data from Shazhu monitoring station on Taihu Lake in Wuxi, Jiangsu Province. The results show that, of the three methods, the stagger phase averaging method is best for calculating the Hurst index of a pollutant time series from the perspective of statistical regularity. Water Science and Engineering. 2008 1(4): 82-88 .

Biodegradability enhancement of municipal landfill leachate

Pi Kewu, Gong Wenqi — 2008-12-30

Pi Kewu, Gong Wenqi The method of enhancing the biodegradability of landfill leachate via air stripping followed by coagulation/ultrafiltration (UF) processes is introduced. In this study, the air stripping process obtained a removal efficiency of 88.6% for ammonia nitrogen (NH₃-N), at an air-to-liquid ratio (A/L) of 3 300 (pH = 11) and after 18 h of stripping. The single coagulation process increased the BOD (biological oxygen demand)/COD (chemical oxygen demand) ratio by 0.089 with a FeCl₃dosage of 570 mg/L, at pH 7.0, and the single UF process increased the BOD/COD ratio from 0.049 to 0.311. However, the combination of coagulation and UF increased the BOD/COD ratio from 0.049 to 0.423, and the final BOD, COD, NH₃-N, and colour of the leachate were 1 023 mg/L, 2 845 mg/L, 145 mg/L, and 2 056, respectively, when a 3 kDa molecular weight cut-off (MWCO) membrane was used at an operating pressure of 0.7 MPa. In the ultrafiltration process, the average solution flux (J_V), concentration multiple (M_C), and retention rate (R) for the COD were 107.3 L/(m²·h), 6.3, and 84.2%, respectively Water Science and Engineering. 2008 1(4): 89-98 .

Effect of EM Bokashi application on control of secondary soil salinization

Shao Xiaohou, Tan Min, Jiang Ping, Cao Weiling — 2008-12-30

Shao Xiaohou, Tan Min, Jiang Ping, Cao Weiling In order to ameliorate saline-alkaline soil, EM Bokashi has been applied to rice production in conjunction with subdrainage in Ningxia Autonomous Region and Zhejiang Province. The preliminary results can be summarized as follows: EM Bokashi can increase soil organic matter content, improve soil porosity and permeability, and raise the soil’s levels of available nutrients; and EM Bokashi combined with subdrainage treatment is more effective in controlling secondary soil salinization and raising the grain yield and quality than other treatments. The results suggest that EM Bokashi can reduce the necessary amount of chemical fertilizer application, thereby improving the agricultural environment, and that the introduction of EM Bokashi into systems of secondary soil salinization control systems has resulted in significant benefits Water Science and Engineering. 2008 1(4): 99-106 .

Reliability model of organization management chain of South-to-North Water Diversion Project during construction period

Feng Jingchun, Zhou Yang, Hong Yuzhen, Zhao Shixin, Ren Xiaoqiang — 2008-12-30

Feng Jingchun, Zhou Yang, Hong Yuzhen, Zhao Shixin, Ren Xiaoqiang In order to analyze the indispensability of the organization management chain of the South-to-North Water Diversion Project (SNWDP), two basic forms (series connection state and mixed state of both series connection and parallel connection) of the organization management chain can be abstracted. The indispensability of each form has been studied and is described in this paper. Through analysis of the reliability of the two basic forms, reliability models of the organization management chain in the series connection state and the mixed state of both series connection and parallel connection have been set up. Water Science and Engineering. 2008 1(4): 107-113 .