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silt Erosion Characteristics of a Cr_3C_2-NiCr Coating Fabricated by High Velocity Oxy-Fuel (HVOF) Thermal Spray

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稀有金属材料与工程 2012年第S1期41卷 453-455页

作者： Wang Qian,Wu Yuping,Li Gaiye,Guo Wenmin,He Zhihua,Hong Sheng Hohai University,Nanjing 210098,China Hohai Univ Coll Mech & Mat Nanjing 210098 Jiangsu Peoples R China

A Cr3C2-NiCr coating was prepared by high velocity oxy-fuel(HVOF)thermal spray on 1Cr18Ni9Ti stainless steel.Phases and microstructures of the coating were investigated by X-ray diffraction(XRD),optical microscopy(OM)and scanning election microscopy(SEM),respectively.The cavitation erosion resistance and silt erosion resistance of the coating were evaluated using a GB/T6383-2009 standard method in two experimental conditions(fresh water and water contained fine silt),compared with the coatings hydro machine material 1Cr18Ni9Ti stainless steel.The coating shows a layered structure and has a significantly higher microhardness(11.97 GPa)than that of the 1Cr18Ni9Ti stainless steel(2.1 GPa),which results in less mass losses both in cavitation erosion and silt erosion experiment.The HVOF coating has a predominant performance in the cavitation erosion and silt erosion resistance.The higher microhardness of the coating is the main cause which results in a less mass losses in the erosion experiments.And the mass loss usually happens at the edges of the pores.

关键词： Cr3C2-NiCr coating cavitation erosion silt erosion

Correlations between silt density index,turbidity and oxidation-reduction potential parameters in seawater reverse osmosis desalination

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Water Science and Engineering 2019年第2期12卷 115-120页

作者： Seyed Mohammad Hossein Fayaz Roya Mafigholami Fatemeh Razavian Karim Ghasemipanah Department of Environment West Tehran BranchIslamic Azad UniversityTehran ***Iran Department of Environment Parand BranchIslamic Azad UniversityParand ***Iran Research Institute of Petroleum Industry Tehran ***Iran

The reverse osmosis method is one of the most widely used methods of seawater desalination at present.Hydrophilic and desalting membranes in reverse osmosis systems are highly susceptible to the input pollutants.Various contaminants,including suspended organic and inorganic matter,result in membrane fouling and membrane degradation.Fundamental parameters such as the turbidity,the amount of chlorine injection,and silt density index (SDI) are the most predominant parameters of fouling control in the membranes.In this study,the operation system included a water intake unit,a pretreatment system,and an RO system.The pretreatment system encompassed a clarifier,a gravity sand filter,pressurized sand filters,and a cartridge filter.The correlation between the amount of chlorine injection in terms of the oxidation-reduction potential (ORP) and the SDI value of the input water was investigated at a specified site next to the Persian Gulf.The results showed that,at certain intervals of inlet turbidity,injection of a certain amount of chlorine into the raw water has a distinct effect on the decrease of SDI.

关键词： silt density index Oxidation-reduction potential Turbidity Reverse osmosis Membrane fouling

Characteristics of Pore Water Pressure of Saturated silt Under Wave Loading

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China Ocean Engineering 2010年第1期24卷 161-172页

作者：高玉峰张健沈扬闫俊 Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai University Geotechnical Research Institute of Hohai University Hohai University

The characteristics of dynamic stress in the seabed under wave loading are constant principal stress and continuous rotation of the principal stress direction. Cyclic triaxial-torsional coupling shear tests were pefformed on saturated silt by the hollow cylinder apparatus under different relative densities, deviator stress ratios and vibration frequencies to study the development of pore water pressure of the saturated silt under wave loading. It was found that the development of pore water pressure follows the trend of ＂fast - steady - drastic＂. The turning point from fast to steady stage is not affected by relative density and deviator stress ratio. However, the turning point from steady to drastic stage relies on relative density and deviator stress ratio. The vibration cycle for the liquefaction of saturated silt decreases with increasing deviator stress ratio and increases with relative density. The vibration cycle for the liquefaction of the saturated silt increases with vibration frequency and reaches a peak value, after which it decreases with increasing vibration frequency for the relative density of 70%. But the vibration cycle for the liquefaction of saturated silt increases with vibration frequency for the relative density of 30%. The development of pore water pressure of the saturated silt is influenced by relative density and vibration frequency.

关键词： silt wave loading pore water pressure vibration frequency cyclic triaxial-torsional coupling shear rotation of principal stress

Analysis of Wave-Induced Liquefaction in Seabed Deposits of silt

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China Ocean Engineering 2011年第1期25卷 31-44页

作者：高玉峰沈扬张健黎冰 Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai University Geotechnical Research Institute of Hohai University Hohai university College of Civil Engineering Southeast University

The dynamic stress introduced in half elastic space by wave loading is characterized by the equation between the magnitude of half cyclic axial stress and cyclic torsion shear stress and the principal stress, whose direction rotates continuously and compression stress on seabed can be calculated by the use of small amplitude wave theory. With relationship curves of saturated silt of liquefaction cycles and cyclic stress ratios obtained by cyclic triaxial-torsional coupling shear tests and curve fitting method to different data points of relative density, it is suggested that the cyclic stress ratio corresponding to constant liquefaction impedance be taken as the critical cyclic stress ratio which implies liquefaction. There exists a linear relationship between critical cyclic stress ratio and relative density under different relative densities. Empirical formula for critical cyclic stress ratios of seabed liquefaction induced by wave loading under different relative densities is established. The possibility of seabed silt liquefaction and its influence factors are analyzed based on the small-amplitude wave theory and the data acquired in laboratory tests.

关键词： wave loading seabed liquefaction silt triaxial-torsional coupling shear critical cyclic stress ratio

Experimental Study on silt Incipient Motion Under Wave Action

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China Ocean Engineering 2007年第4期21卷 677-688页

作者：洪大林高亚军谢瑞姬昌辉申霞 State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Nanjing Hydraulic Research Institute

Experiments on silt incipient motion under wave action were carried out. Under wave action, for different wave periods, water depths and bulk densities of silt, the shear stress or height of waves for incipient motion was determined, and a relation between the shear stress and bulk density of silt was established. Results indicate that the critical shear stress depends on the structure of the silt itself, related to the tightness between the grains （or bulk density）. Exterior condition is only an external cause of silt incipient motion, and the critical shear stress for the incipient motion is the token of exterior condition.

关键词： wave silt incipient motion bulk density shear stress

Study on the Liquefaction Properties of silt at Yellow River Delta

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Journal of Ocean University of China 2018年第6期17卷 1382-1390页

作者： LIU Tao ZHOU Lei CHEN Xuguang Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of China Laboratory for Marine Geology Qingdao National Laboratory for Maine Science and Technology

The seabed of the Yellow River Delta is formed by the rapid deposition of sediments from the Yellow River. Recent researches have shown that the geological hazards in the Yellow River Delta are mainly related to the liquefaction of silty seabed under cyclic loading. In this paper, based on the theory of Stokes Viscous Principle, a self-design dragging ball apparatus was used to study the fluid characteristics of liquefied and post-liquefied silt more thoroughly. Wave flume and shaking table were used to apply wave loads and vibration loads. The pore pressure, earth pressure, and moving parameters of the dragging ball were recorded during tests. The effect of cyclic loads and excess pore pressure ratio on viscosity of silty soil is discussed. The constitutive model of flow characteristics of liquefied silt is also established. The results indicate that the apparent viscosity of silty soil is much higher than sand. Cyclic loads accelerated the process of silt liquefaction, resulting in the decrease in apparent viscosity. The excess pore pressure ratio(ru) has effect on silt liquefaction. When the soil had not reached the completely liquefied state(ru silty soil characterized by shear thinning can be viewed as a type of non-Newtonian fluid. The equation of the shear stress and shear strain rates was established by fitting the test data.

关键词： silt liquefaction fluid dragging ball method

NUMERICAL PREDICTION OF silt ABRASIVE EROSION IN HYDRAULIC TURBINE

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Journal of Hydrodynamics 1999年第1期11卷 103-110页

作者： Zhang Jia-chuan Liu Xiao-bing (Sichuan Institute of Technology, Chengdu 611744, P. R. China) Sichuan Inst of Technology Chengdu China

Numerical investigations on silt abrasive erosion of hydraulic turbine for low sand concentration were reported. The turbulent flow velocity fields, pressure distributions and trajectories of sand particle in the hydraulic turbine have been numerically calculated by mixed Eulerian-Lagrangian turbulence model, which was based on a particle-source-in-cell numerical technique for two-phase flows. The Eulerian equations were used for the description of liquid phase flow, the solid particles were treated within Lagrangian framework. The sand particle rebound model and erosion wear model in flow field were also presented. The erosion wear rates of the guide vane of Gezhouba hydraulic turbine were calculated. The numerical predictions show a good agreement with the tests.

关键词： Two phase flow Sand silt Particles (particulate matter) Turbulent flow Erosion Abrasives Numerical analysis

Intergrain contact density indices for granular mixes——Ⅱ: Liquefaction resistance

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Earthquake Engineering and Engineering Vibration 2007年第2期6卷 135-146页

作者： S. Thevanayagam Dept. of Civil Struct. & Env. Eng. State Univ. of New York Buffalo NY 14260 USA

Whether the presence of non-plastic silt in a granular mix soil impact its liquefaction potential and how to evaluate liquefaction resistance of sand containing different amounts of silt contents are both controversial issues. This paper presents the results of an experimental evaluation to address these issues. Two parameters, namely, equivalent intergranular void ratio （ec）eq and equivalent interfine void ratio （ef）eq, proposed in a companion paper （Thevanayagam, 2007） as indices of active grain contacts in a granular mix, are used to characterize liquefaction resistance of sands and silty sands. Results indicate that, at the same global void ratio （e）, liquefaction resistance of silty sand decreases with an increase in fines content （Cv） up to a threshold value （Crth）. This is due to a reduction in intergrain contact density between the coarse grains. Beyond Crth, with further addition of fines, the interfine contacts become significant while the inter-coarse grain contacts diminish and coarse grains become dispersed. At the same e, the liquefaction resistance increases and the soil becomes stronger with a fttrther increase in silt content. Beyond a limiting fines content （CrL）, the liquefaction resistance is controlled by interfine contacts only. When Cr〈Crth, at the same （e）eq, the liquefaction resistance of silty sand is comparable to that of the host clean sand at a void ratio equal to （ec）eq. When CF〉CFth, at the same （ef）eq, the cyclic strength of a sandy silt is comparable to the host silt at a void ratio equal to （ef）eq.

关键词： Sand silt fines silty sand liquefaction cyclic strength

Intergrain contact density indices for granular mixes——Ⅰ: Framework

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Earthquake Engineering and Engineering Vibration 2007年第2期6卷 123-134页

作者： S. Thevanayagam Dept. of Civil Struct. and Envir. Eng. State University of New York Buffalo NY 14260 USA

Mechanical behavior such as stress-strain response, shear strength, resistance to liquefaction, modulus, and shear wave velocity of granular mixes containing coarse and fine grains is dependent on intergrain contact density of the soil. The global void ratio e is a poor index of contact density for such soils. The contact density depends on void ratio, fine grain content （Cv）, size disparity between particles, and gradation among other factors. A simple analysis of a two-sized particle system with large size disparity is used to develop an understanding of the effects of Cv, e, and gradation of coarse and fine grained soils in the soil mix on intergrain contact density. An equivalent intergranular void ratio （ec）oq is introduced as a useful intergrain contact density for soils at fines content of less than a threshold value Crth. Beyond this value, an equivalent interfine void ratio （ef）eq is introduced as a primary intergrain contact density index. At higher values of Cv beyond a limiting value of fine grains content CVL, an interfine void ratio ef is introduced as the primary contact density index. Relevant equivalent relative density indices （Drc）eq and （Drf）eq are also presented. Experimental data show that these new indices correlate well with steady state strength, liquefaction resistance, and shear wave velocities of sands, silty sands, sandy silts, and gravelly sand mixes.

关键词： Sand silt silty sand sandy silt cyclic strength shear wave velocity intergrain contact density