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incipient motion of Bed Load Sediment and Its Application in the Three Gorges Hydro Project

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四川大学学报（工程科学版） 2005年第S1期37卷 102-105页

作者： HE Wenshe~(1,3) CAO Shuyou~2 YUAN Jie~3 DAI Huichao~3 (1.Lanzhou Jiao Tong Univ.,Lanzhou 730070,China 2.State Key Lab.of Hydraulics and Mountain River Eng.,Sichuan Univ.,Chengdu 610065,China 3.China Yangtze Three Gorges Project Development Corporation,Hubei Yichang 443002,China) Lanzhou Jiaotong Univ. Lanzhou 730070 China State Key Lab. of Hydraulics and Mountain River Eng. Sichuan Univ. Chengdu 610065 China China Yangtze Three Gorges Project Development Corporation Yichang 443002 China

A formula for the calculation of critical shear stress of non-uniform sediment was developed by on river bed has been established while considering the relative degree expose of *** values of the Coeffi- cients in the formula have been *** formula has been verified with prototype observation data, flumes data of both nature and lightweight *** computed results fully reflect the characteristics of thresh- old motion of non-uniform *** result have been used in some physical mo...

关键词： non-uniform sediment incipient motion bed load Three Gorges Hydro Project

incipient motion of Sediment Under Currents

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China Ocean Engineering 2000年第4期15卷 391-406页

作者：窦国仁 Chinese Academy of Sciences Nanjing 210029 China Chinese Society of Ocean Engineering Nanjing 210029 China Nanjing Hydraulic Research Institute Nanjing 210029 China

Summarized in the paper are the author's studies on incipient motion of sediment in recent 40 years. In addition to the forces of gravity, drag and lift, the cohesive force and the additional static pressure are important for fine particles. The relations between three stages of incipient motion are defined by use of instantaneous velocity. Formulas for initial velocity and critical shear stress are given and overall verified by the author's and others' experimental data.

关键词： sediment incipient motion initial velocity critical shear stress

incipient motion of sediment by waves

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Science China(Technological Sciences) 2001年第3期44卷 309-318页

作者：窦国仁窦希萍李褆来 Nanjing Hydraulic Research Institute Nanjing China Nanjing Institute of Hydrology and Water Resources Nanjing China

In this paper, the forces acting on sediment particles are analyzed in all the aspects. Considering the cohesive force between particles, the additional static water pressure induced by the solid-body characteristics of film water and the inertia force of waves, a unified formula of the incipient motion for both coarse and fine particles is defined. The formula can reflect the variation in the initial velocity of fine particles with the volume weight of sediment. The verification of the formula is carried out by use of both experimental data and field observation data accumulated by experts at home and abroad. The verification shows that the formula expresses the law governing the incipient motion of sediment of all particle sizes inclusive of natural sediment and light-weight materials, and thus a basic formula for the study and solution of sediment problems in estuarine and coastal regions is provided.

关键词： wave sediment incipient motion

incipient motion of cohesionless sediments on riverbanks with ground water injection

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International Journal of Sediment Research 2012年第1期27卷 111-119页

作者： Yan LU Yong-jun LU Yee-meng CHIEW Nanjing Hydraulic Research Institute State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering School of Civil and Environmental Engineering Nanyang Technological Univ.

This study investigates the influence of ground water injection on the initial movement of non-cohesive sediment particles on a riverbank slope analytically and *** including the hydraulic gradient in the force analysis,the critical condition was derived to account for the effect of seepage flow, showing that the seepage hydraulic gradient and the riverbank slope are governing parameters in modifying the incipient motion of sediments on a riverbank *** investigations were performed in an open-channel flume for various riverbank slopes and hydraulic gradients of injection, showing that the critical shear stress increases with decreasing riverbank slopes and vise-versa,while injection reduces the critical *** experimental data agree well with the theoretical derived expression of the critical condition in the case of injection.

关键词： incipient motion Riverbank Injection Sediment Seepage

incipient motion of gravel in a bottomless arch culvert

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International Journal of Sediment Research 2011年第1期26卷 15-26页

作者： B.M.CROOKSTON B.P.M.TULLIS Utah State University 8200 Old Main HillLoganUT 84322

incipient motion was investigated for four gravel substrate materials in a bottomless arch culvert and a rectangular *** methods for calculating Shields parameter at incipient motion（θc） based upon local flow parameters were *** incipient motion region for bottomless arch culverts in fully turbulent flow was defined with two bounding curves on Shields *** variation ofθcas a function of relative roughness was ***,a method that utilizes measured flow velocities to determine stable substrate particle diameters for bottomless arched culverts is presented as an alternative to the Shields diagram.

关键词： incipient motion Bottomless arch culvert Shields parameter Flow rate Experiment

Shear velocity criterion for incipient motion of sediment

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Water Science and Engineering 2014年第2期7卷 183-193页

作者： Francisco J.M.SIMOES U.S. Geological Survey Geomorphology and Sediment Transport LaboratoryGolden CO 80403 USA

The prediction of incipient motion has had great importance to the theory of sediment transport. The most commonly used methods are based on the concept of critical shear stress and employ an approach similar, or identical, to the Shields diagram. An alternative method that uses the movability number, defined as the ratio of the shear velocity to the particle＇s settling velocity, was employed in this study. A large amount of experimental data were used to develop an empirical incipient motion criterion based on the movability number. It is shown that this approach can provide a simple and accurate method of computing the threshold condition for sediment motion.

关键词： incipient motion sediment transport Shields diagram critical shear stress criticalshear velocity movability number

A method for simulating sediment incipient motion varying with time and space in an ocean model(FVCOM):development and validation

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Journal of Oceanology and Limnology 2018年第4期36卷 1216-1235页

作者： ZHU Zichen WANG Yongzhi BIAN Shuhua HU Zejian LIU Jianqiang LIU Lejun The First Institute of Oceanographic State Oceanic AdministrationQingdao 266061China

We modified the sediment incipient motion in a numerical model and evaluated the impact of this modification using a study case of the coastal area around Weihai, China. The modified and unmodified versions of the model were validated by comparing simulated and observed data of currents, waves, and suspended sediment concentrations(SSC) measured from July 25^(th) to July 26^(th), 2006. A fitted Shields diagram was introduced into the sediment model so that the critical erosional shear stress could vary with time. Thus, the simulated SSC patterns were improved to more closely reflect the observed values, so that the relative error of the variation range decreased by up to 34.5% and the relative error of simulated temporally averaged SSC decreased by up to 36%. In the modified model, the critical shear stress values of the simulated silt with a diameter of 0.035 mm and mud with a diameter of 0.004 mm varied from 0.05 to 0.13 N/m^2, and from 0.05 to 0.14 N/m^2, respectively, instead of remaining constant in the unmodified model. Besides, a method of applying spatially varying fractions of the mixed grain size sediment improved the simulated SSC distribution to fit better to the remote sensing map and reproduced the zonal area with high SSC between Heini Bay and the erosion groove in the modified model. The Relative Mean Absolute Error was reduced by between 6% and 79%, depending on the regional attributes when we used the modified method to simulate incipient sediment motion. But the modification achieved the higher accuracy in this study at a cost of computation speed decreasing by 1.52%.

关键词： sediment model incipient motion suspended load critical shear stress for erosion fraction of mixed grain size sediment

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

Rheological Properties and incipient motion of Cohesive Sediment in the Haine Estuary of China

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China Ocean Engineering 2002年第4期17卷 483-498页

作者：白玉川 NG Chiu-on 沈涣庭王尚毅 Institute for Sedimentation on River and Coast Engineering Tianjin UniversityTianjin300072China Department of Mechanical Engineering The University of Hong KongHong KongChina The State Key Laboratory of Estuarine and Coastal Research East China Normal UniversityShanghai 200062China

The Haihe cohesive sediment, which is typical in China, is studied systematically for its basic physical and incipient motion properties. Following the requirements of dredging works in the Haihe Estuary, cohesive sediment samples were taken from three locations. Laboratory experiments were conducted to determine the rheological properties of these samples and to examine the incipient motion of the cohesive sediment. It is found that the cohesive sediment has an obvious yield stress tau(b), which increases with the mud density in a manner of an exponential function, and so does the viscosity parameter eta. The cohesive sediment behaves like a Bingham fluid when its density is below 1.38 similar to 1.40 g/cm(3), and when denser than these values, it may become a power-law fluid. The incipient motion experiment also revealed that the incipient velocity of the cohesive sediment increases with die density in an exponential manner. Therefore, the incipient motion is primarily related to the density, which is different from the case for non-cohesive sediment in which the incipient motion is con-elated with the diameter of sand particles instead. The incipient motion occurs in two different ways depending on the concentration of mud in the bottom. For sufficiently fine particles and a concentration lower than 1.20 g/cm(3), the cohesive sediment appears as fluidized mud, and the incipient motion is in the form of instability of an internal wave. For a higher concentration, the cohesive sediment appears as general quasi-solid-mud, and the incipient motion can be described by a series of extended Shields curves each with a different porosity for newly deposited alluvial mud.

关键词： incipient motion rheological properties cohesive sediment estuary and coast