Zeitschriftenartikel: „Cohesive bed“

1

Khazratov, A. N., O. Sh Bazarov, A. R. Jumayev, F. F. Bobomurodov und N. Z. Mamatov. „Influence of cohesion strength in cohesive soils onchannel bed erosion“. E3S Web of Conferences 410 (2023): 05018. http://dx.doi.org/10.1051/e3sconf/202341005018.

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The results of experimental studies on the mechanical properties of cohesive soils associated with the use in the study of the erosion process are presented. The influence of the cohesion strength of cohesive soil on erosion is described. The relationship between the erosionflow velocities and cohesion strength has been obtained.

2

Gong, Mingze, Sivar Azadi, Adrien Gans, Philippe Gondret und Alban Sauret. „Erosion of a cohesive granular material by an impinging turbulent jet“. EPJ Web of Conferences 249 (2021): 08011. http://dx.doi.org/10.1051/epjconf/202124908011.

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The erosion of a cohesive soil by an impinging turbulent jet is observed, for instance, during the landing of a spacecraft or involved in the so-called jet erosion test. To provide a quantitative understanding of this situation for cohesive soils, we perform experiments using a model cohesion controlled granular material that allows us to finely tune the cohesion between particles while keeping the other properties constant. We investigate the response of this cohesive granular bed when subjected to an impinging normal turbulent jet. We characterize experimentally the effects of the cohesion on the erosion threshold and the development of the crater. We demonstrate that the results can be rationalized by introducing a cohesive Shields number that accounts for the inter-particles cohesion force. The results of our experiments highlight the crucial role of cohesion in erosion processes.

3

Glasbergen, K., M. Stone, B. Krishnappan, J. Dixon und U. Silins. „The effect of coarse gravel on cohesive sediment entrapment in an annular flume“. Proceedings of the International Association of Hydrological Sciences 367 (03.03.2015): 157–62. http://dx.doi.org/10.5194/piahs-367-157-2015.

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Abstract. While cohesive sediment generally represents a small fraction (<0.5%) of the total sediment mass stored in gravel-bed rivers, it can strongly influence physical and biogeochemical processes in the hyporheic zone and alter aquatic habitat. This research was conducted to examine mechanisms governing the interaction of cohesive sediments with gravel beds in the Elbow River, Alberta, Canada. A series of erosion and deposition experiments with and without a gravel bed were conducted in a 5-m diameter annular flume. The critical shear stress for deposition and erosion of cohesive sediment without gravel was 0.115 Pa and 0.212 Pa, respectively. In experiments with a gravel bed, cohesive sediment moved from the water column into the gravel bed via the coupling of surface and pore water flow. Once in the gravel bed, cohesive sediments were not mobilized under the maximum applied shear stresses (1.11 Pa) used in the experiment. The gravel bed had an entrapment coefficient (ratio between the entrapment flux and the settling flux) of 0.2. Accordingly, when flow conditions are sufficient to produce a shear stress that will mobilize the armour layer of the gravel bed (>16 Pa), cohesive materials trapped within the gravel bed will be entrained and transported into the Glenmore Reservoir, where sediment-associated nutrients may pose treatment challenges to the drinking water supply.

4

Borovkov, V. S., und M. A. Volynov. „RIVER BED EROSION IN COHESIVE SOILS“. Vestnik MGSU, Nr. 4 (April 2013): 143–49. http://dx.doi.org/10.22227/1997-0935.2013.4.143-149.

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5

Safak, Ilgar. „Variability of Bed Drag on Cohesive Beds under Wave Action“. Water 8, Nr. 4 (01.04.2016): 131. http://dx.doi.org/10.3390/w8040131.

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6

Geng, Tiesuo, Shuanghua Chen, Liuqun Zhao und Zhe Zhang. „Research on Bonding Performance of Anchorage Caisson Foundation with Different Contact Surfaces and Grouting Bed“. Buildings 11, Nr. 8 (19.08.2021): 365. http://dx.doi.org/10.3390/buildings11080365.

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In view of the first domestic offshore suspension bridge with caisson foundation, this paper mainly studies the bonding properties between underwater pre-filled aggregate grouting bed and anchorage caisson foundation. Through the test, the cohesive force of adding ordinary concrete between the anchorage caisson foundation and the grouting bed, the cohesive force of adding paper base asphalt felt between the anchorage caisson foundation and the grouting bed, and the cohesive force of adding geotextile between the anchorage caisson foundation and the grouting bed are measured, respectively. When the contact surface is concrete and geotextile, the fracture form of the specimen was analyzed by numerical simulation, and the AE variation trend of the two specimens have been studied. The results of this article can provide references for other projects.

7

Berlamont, Jean E., und Hilde M. Torfs. „Modeling (partly) cohesive sediment transport in sewer systems“. Water Science and Technology 33, Nr. 9 (01.04.1996): 171–78. http://dx.doi.org/10.2166/wst.1996.0204.

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Although the basic mechanisms of sediment transport in sewers are the same as in rivers, it is not necessarily appropriate to use the many models that have been developed for sediment transport in rivers also in sewers. Different reasons are: 1) sewer sediments are often mixtures of cohesive and non cohesive material, and the bed is often stratified; 2) due to consolidation of the (partly cohesive) bed material, the erosion resistance of the bed may vary with time; 3) the flow conditions in sewers are usually unsteady, which is not accounted for in the classical sediment transport models; 4) existing models have been derived from experiments in rectangular flumes: the results are not directly applicable to sewers with circular cross section where the distribution of bed shear stress may be completely different from a rectangular section; 5) the limited availability of erodible material and the varying supply of sediments add additional difficulty to the modelling of sediment transport in sewers.

8

Mosquera, R., V. Groposo und F. Pedocchi. „Acoustic measurements of a liquefied cohesive sediment bed under waves“. Advances in Geosciences 39 (01.04.2014): 1–7. http://dx.doi.org/10.5194/adgeo-39-1-2014.

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Abstract. In this article the response of a cohesive sediment deposit under the action of water waves is studied with the help of laboratory experiments and an analytical model. Under the same regular wave condition three different bed responses were observed depending on the degree of consolidation of the deposit: no bed motion, bed motion of the upper layer after the action of the first waves, and massive bed motion after several waves. The kinematic of the upper 3 cm of the deposit were measured with an ultrasound acoustic profiler, while the pore-water pressure inside the bed was simultaneously measured using several pore pressure sensors. A poro-elastic model was developed to interpret the experimental observations. The model showed that the amplitude of the shear stress increased down into the bed. Then it is possible that the lower layers of the deposit experience plastic deformations, while the upper layers present just elastic deformations. Since plastic deformations in the lower layers are necessary for pore pressure build-up, the analytical model was used to interpret the experimental results and to state that liquefaction of a self consolidated cohesive sediment bed would only occur if the bed yield stress falls within the range defined by the amplitude of the shear stress inside the bed.

9

Wang, Rui, und Guoliang Yu. „Experimental study on incipient condition of fluidized bed sediment in oscillatory“. E3S Web of Conferences 81 (2019): 01014. http://dx.doi.org/10.1051/e3sconf/20198101014.

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In this paper, the incipient condition of the fluidized bed sediment with different sizes and water contents were experimentally studied in an os- cillatory tunnel made of acrylic boards. One-hundred experimental runs were performed with sediment samples by varying the yield stress to determine the relationship between the critical condition of incipient motion and the rheolog- ical properties of the cohesive sediments. Experimental results showed that the yield stress of the bed sediment decreased as the fluidization level increased. When the yield stress is no longer changed, the bed sediment was considered completely fluidized. In oscillatory flow, the critical shear stress decreases with the increase of fluidization level. When the bed sediment reaches the full flu- idization state, the critical shear stress of the bed sediment at the bottom re- mained constant. For cohesive sediments, in the case that particle size and bulk density were known, the relationship between the yield stress and the critical shear stress was analyzed, and the incipient condition of the cohesive sediment under oscillatory flow action was determined.

10

Sherwood, Christopher R., Alfredo L. Aretxabaleta, Courtney K. Harris, J. Paul Rinehimer, Romaric Verney und Bénédicte Ferré. „Cohesive and mixed sediment in the Regional Ocean Modeling System (ROMS v3.6) implemented in the Coupled Ocean–Atmosphere–Wave–Sediment Transport Modeling System (COAWST r1234)“. Geoscientific Model Development 11, Nr. 5 (14.05.2018): 1849–71. http://dx.doi.org/10.5194/gmd-11-1849-2018.

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Abstract. We describe and demonstrate algorithms for treating cohesive and mixed sediment that have been added to the Regional Ocean Modeling System (ROMS version 3.6), as implemented in the Coupled Ocean–Atmosphere–Wave–Sediment Transport Modeling System (COAWST Subversion repository revision 1234). These include the following: floc dynamics (aggregation and disaggregation in the water column); changes in floc characteristics in the seabed; erosion and deposition of cohesive and mixed (combination of cohesive and non-cohesive) sediment; and biodiffusive mixing of bed sediment. These routines supplement existing non-cohesive sediment modules, thereby increasing our ability to model fine-grained and mixed-sediment environments. Additionally, we describe changes to the sediment bed layering scheme that improve the fidelity of the modeled stratigraphic record. Finally, we provide examples of these modules implemented in idealized test cases and a realistic application.

11

Banasiak, Robert. „Hydraulic performance of sewer pipes with deposited sediments“. Water Science and Technology 57, Nr. 11 (01.06.2008): 1743–48. http://dx.doi.org/10.2166/wst.2008.287.

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This paper investigates in-sewer sediment deposit behaviour and its influence on the hydraulic performance of sewer pipes. This evaluation is based on experimental results regarding the mobility of non-cohesive and partly cohesive deposits in a partially full circular pipe. The focus of these tests is on the development of bed forms and friction characteristics. In particular, it is investigated to what extent the bed forms from the non-cohesive and (partly) cohesive sediments affect a sewer's discharge capacity. Based on the laboratory study results and on the existing criteria for sewer design, a generic assessment of a sewer's hydraulic performance is made. The relative discharge factor for a pipe with sediment deposit is analysed in terms of the thickness and roughness of the deposit.

12

Gao, Xiaojing, Qiusheng Wang, Chongbang Xu und Ruilin Su. „Experimental Study on Critical Shear Stress of Cohesive Soils and Soil Mixtures“. Transactions of the ASABE 64, Nr. 2 (2021): 587–600. http://dx.doi.org/10.13031/trans.14065.

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HighlightsErosion tests were performed to study the critical shear stress of cohesive soils and soil mixtures.Linear relationships were observed between critical shear stress and cohesion of cohesive soils.Mixture critical shear stress relates to noncohesive particle size and cohesive soil erodibility.A formula for calculating the critical shear stress of soil mixtures is proposed and verified.Abstract. The incipient motion of soil is an important engineering property that impacts reservoir sedimentation, stable channel design, river bed degradation, and dam breach. Due to numerous factors influencing the erodibility parameters, the study of critical shear stress (tc) of cohesive soils and soil mixtures is still far from mature. In this study, erosion experiments were conducted to investigate the influence of soil properties on the tc of remolded cohesive soils and cohesive and noncohesive soil mixtures with mud contents varying from 0% to 100% using an erosion function apparatus (EFA). For cohesive soils, direct linear relationships were observed between tc and cohesion (c). The critical shear stress for soil mixture (tcm) erosion increased monotonically with an increase in mud content (pm). The median diameter of noncohesive soil (Ds), the void ratio (e), and the organic content of cohesive soil also influenced tcm. A formula for calculating tcm considering the effect of pm and the tc of noncohesive soil and pure mud was developed. The proposed formula was validated using experimental data from the present and previous research, and it can reproduce the variation of tcm for reconstituted soil mixtures. To use the proposed formula to predict the tcm for artificial engineering problems, experimental erosion tests should be performed. Future research should further test the proposed formula based on additional experimental data. Keywords: Cohesive and noncohesive soil mixture, Critical shear stress, Erodibility, Mud content, Soil property.

13

Yamanishi, Hiroyuki, Osamu Higashi, Tetsuya Kusuda und Ryoichi Watanabe. „Scouring of Sloping Cohesive Sediment Bed under Waves.“ Doboku Gakkai Ronbunshu, Nr. 607 (1998): 55–67. http://dx.doi.org/10.2208/jscej.1998.607_55.

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14

Tong, Hua, und Hongzhong Li. „Floating internals in fast bed of cohesive particles“. Powder Technology 190, Nr. 3 (März 2009): 401–9. http://dx.doi.org/10.1016/j.powtec.2008.08.023.

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15

Qin, Cuicui, Xuejun Shao und Yi Xiao. „Secondary Flow Effects on Deposition of Cohesive Sediment in a Meandering Reach of Yangtze River“. Water 11, Nr. 7 (12.07.2019): 1444. http://dx.doi.org/10.3390/w11071444.

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Few researches focus on secondary flow effects on bed deformation caused by cohesive sediment deposition in meandering channels of field mega scale. A 2D depth-averaged model is improved by incorporating three submodels to consider different effects of secondary flow and a module for cohesive sediment transport. These models are applied to a meandering reach of Yangtze River to investigate secondary flow effects on cohesive sediment deposition, and a preferable submodel is selected based on the flow simulation results. Sediment simulation results indicate that the improved model predictions are in better agreement with the measurements in planar distribution of deposition, as the increased sediment deposits caused by secondary current on the convex bank have been well predicted. Secondary flow effects on the predicted amount of deposition become more obvious during the period when the sediment load is low and velocity redistribution induced by the bed topography is evident. Such effects vary with the settling velocity and critical shear stress for deposition of cohesive sediment. The bed topography effects can be reflected by the secondary flow submodels and play an important role in velocity and sediment deposition predictions.

16

Shugar, Daniel, Ray Kostaschuk, Peter Ashmore, Joe Desloges und Leif Burge. „In situ jet-testing of the erosional resistance of cohesive streambeds“. Canadian Journal of Civil Engineering 34, Nr. 9 (01.09.2007): 1192–95. http://dx.doi.org/10.1139/l07-024.

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Fletchers Creek is located in an urbanizing basin near Toronto and has a bed and banks composed primarily of cohesive Halton Till. Critical shear stress and an erodibility coefficient for the till were determined using an in situ jet-tester that directs a submerged jet of water perpendicular to the sediment surface. The results from 10 jet-tests indicate that the till has a relatively low critical shear stress and relatively high erodibility coefficient and could be susceptible to bed scour during flood events. Many other streams in southern Ontario have urbanizing watersheds with cohesive till beds that may also be susceptible to erosion.Key words: critical stress, submerged jet, erodibility, cohesive soils.

17

Willis, David H., und B. G. Krishnappan. „Numerical modelling of cohesive sediment transport in rivers“. Canadian Journal of Civil Engineering 31, Nr. 5 (01.10.2004): 749–58. http://dx.doi.org/10.1139/l04-043.

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Techniques available to practicing civil engineers for numerically modelling cohesive mud in rivers and estuaries are reviewed. Coupled models, treating water and sediment as a single process, remain research tools but are usually not three-dimensional. The decoupled approach, which separates water and sediment computations at each model time step, allows the three-dimensional representation of at least the bed and the use of well-proven, commercial, numerical, hydrodynamic models. Most hydrodynamic models compute sediment transport in suspension but may require modification of the dispersion coefficients to account for the presence of sediment. The sediment model deals with the sediment exchange between the water column and the bed using existing equations for erosion and deposition. Both equations relate the sediment exchange rates to the shear stress in the bottom boundary layer. In real rivers and estuaries, a depositional bed layer is associated with a period of low flow and shear, at slack tide for example, whereas in numerical models a layer is defined by the model time step. The sediment model keeps track of the uppermost layers at each model grid point, including consolidation and strengthening. Although numerical hydrodynamic models are based strongly on physics, sediment models are only numerical frameworks for interpolating and extrapolating full-scale field or laboratory measurements of "hydraulic sediment parameters," such as threshold shear stresses. Calibration and verification of models against measurement are therefore of prime importance.Key words: cohesive sediment, mathematical modelling, settling velocity, erosion, resuspension, deposition, fluid mud, bed layers.

18

Khassaf, Saleh Issa. „Effect of Cohesive and Non-Cohesive Soils on Equilibrium Scour Depth“. Tikrit Journal of Engineering Sciences 14, Nr. 2 (30.06.2007): 73–85. http://dx.doi.org/10.25130/tjes.14.2.04.

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In this research ,the effect of cohesive soils ( clay ) and non –cohesive soils sand on equilibrium scour depth was studied .Experiments were carried out on two types of clay and two types of sand as a bed material using an obstruction ( pier ) to create a local scour. The effect of flow velocity and Froude number on scour depth and the occurrence time of equilibrium scour depth were studied . The results show that for the same conditions, the rate of scour in the clayey soils is less than in sandy soils. Also the time required for occurrence of the maximum scour depth ( equilibrium depth ) in clayey soils is more than in sandy soils. Two formulas were found to predict the equilibrium scour depth in terms of Froude number ,the first is for clayey soils and the second for sandy soils .

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Milburn, David, und B. G. Krishnappan. „Modelling Erosion and Deposition of Cohesive Sediments from Hay River, Northwest Territories, Canada“. Hydrology Research 34, Nr. 1-2 (01.02.2003): 125–38. http://dx.doi.org/10.2166/nh.2003.0032.

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A large volume sample of river-bed cohesive sediment and water from Hay River, Northwest Territories, Canada was collected during a spring field program in 2000 as part of a study on under-ice movement of sediment just before breakup. Controlled laboratory experiments were subsequently conducted on the Hay River water/sediments in a rotating annular flume at Burlington, Ontario, Canada to better understand the deposition and erosion processes of cohesive sediment transport. The deposition experiments in the rotating flume confirmed that the Hay River sediment is cohesive and the critical shear stress for deposition and the rates of deposition are a function of bed shear stress and the initial concentration of the sediment in suspension. The erosion experiments provided quantitative data on the critical shear stress for erosion and the rates of erosion as a function of bed shear stress and the age of the sediment deposit. The erosion experiments also indicated that the growth of the biofilm had an influence on the erosion characteristics of the Hay River sediment. Based on the data from the rotating circular flume experiments, a modelling strategy is proposed for calculating the under-ice transport of the cohesive sediments in the Hay River.

20

Geremew, Africa M. „Erosion characteristics and stochastic nature of bed shear stress in underwater mine tailings“. Canadian Journal of Civil Engineering 44, Nr. 6 (Juni 2017): 426–40. http://dx.doi.org/10.1139/cjce-2016-0319.

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The erosion of mine tailings was investigated by examining the physical processes during the initiation of motion of the tailings. Erosion experiments were conducted on mine tailings samples and natural soils in a Plexiglas laboratory annular column under 50 cm water cover. Resuspension was introduced with a Teflon stirrer and the bed shear stress was estimated from the measured near-bed velocity field and the pressure change in the boundary layer. Two modes of initiation of motion of cohesive mine tailings that showed cohesive behaviour was noticed: pitting erosion and line erosion and the modes of initiation of motion changed mainly with percentage of fines. At incipient motion of the tailings that showed cohesive behaviour, the pore water pressure distribution showed a relative sudden peak and a decline when the aggregated tailings burst. A four order of magnitude difference was observed between the undrained shear strength and critical shear stress for surface erosion of the tailings. The stochastic nature of the bed shear stress was explained by the Rayleigh distribution that provides an approach for correcting the critical shear stress estimated from the near-bed velocity. This correction is necessary to achieve a conservative estimate of the critical shear stress for design purposes.

21

Mazurek, Kerry A., und Tanvir Hossain. „Scour by jets in cohesionless and cohesive soils“. Canadian Journal of Civil Engineering 34, Nr. 6 (01.06.2007): 744–51. http://dx.doi.org/10.1139/l07-005.

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A technique is developed in this paper to unify the methods of analyzing scour by turbulent water jets in cohesionless and cohesive soils. Data from previous studies using circular turbulent impinging jets and circular turbulent wall jets are used to compare the scour in low void ratio cohesive soils to that in uniform sands and gravels. Scour by these jets is related to the dimensionless excess stress on the soil bed. It is seen that this parameter will likely work well for developing a method to predict scour for circular wall jets that is applicable to both materials. However, a circular impinging jet appears to vary appreciably in its interaction with the bed between the two types of soil, which makes developing a unified method to predict scour by impinging jets more difficult. Key words: erosion, scour, water jets, cohesionless sediments, cohesive sediments, fine-grained soils, coarse-grained soils.

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Ebisa Fola, Miressa, und Colin D. Rennie. „Downstream Hydraulic Geometry of Clay-Dominated Cohesive Bed Rivers“. Journal of Hydraulic Engineering 136, Nr. 8 (August 2010): 524–27. http://dx.doi.org/10.1061/(asce)hy.1943-7900.0000199.

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23

Krone, Ray B. „Effects of Bed Structure on Erosion of Cohesive Sediments“. Journal of Hydraulic Engineering 125, Nr. 12 (Dezember 1999): 1297–301. http://dx.doi.org/10.1061/(asce)0733-9429(1999)125:12(1297).

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24

Aberle, Jochen, Vladimir Nikora und Roy Walters. „Effects of bed material properties on cohesive sediment erosion“. Marine Geology 207, Nr. 1-4 (Juni 2004): 83–93. http://dx.doi.org/10.1016/j.margeo.2004.03.012.

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25

Chaudhuri, Susanta, Santosh Kumar Singh, Koustuv Debnath und Mrinal K. Manik. „Pier scour within long contraction in cohesive sediment bed“. Environmental Fluid Mechanics 18, Nr. 2 (17.11.2017): 417–41. http://dx.doi.org/10.1007/s10652-017-9560-x.

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26

Yang, S. C. „Segregation of cohesive powders in a vibrated granular bed“. Chemical Engineering Science 61, Nr. 18 (September 2006): 6180–88. http://dx.doi.org/10.1016/j.ces.2006.05.048.

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27

Zhou, Zaiyang, Jianzhong Ge, Dirk Sebastiaan van Maren, Jinghua Gu, Pingxing Ding und Zhengbing Wang. „Measuring Bed Exchange Properties of Cohesive Sediments Using Tripod Data“. Journal of Marine Science and Engineering 10, Nr. 11 (10.11.2022): 1713. http://dx.doi.org/10.3390/jmse10111713.

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The Krone–Partheniades (K-P) framework has been used for decades to quantify and analyze the sediment exchange at a water–bed interface. Measuring the erosion and deposition parameters that are part of this framework requires time-consuming field observations. Additionally, the erosion parameters are measured independently of deposition parameters, while in reality they are coupled. In numerical models applying the K-P framework these parameters are often assumed to be constant in time and mutually independent. In this study, we develop a relatively simple methodology to determine the erosion and deposition parameters, using conventional near-bed observations of bed level, sediment concentration and flow velocity. This methodology is subsequently applied to tripod observations collected in the Changjiang estuary, China, to compute continuous time-varying erosion and settling parameters. We propose a diagram to visualize the interdependency and accuracy of erosion and deposition parameters, which is the input for K-P framework models requiring this interdependency.

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Bosa, Silvia, Marco Petti und Sara Pascolo. „Numerical Modelling of Cohesive Bank Migration“. Water 10, Nr. 7 (21.07.2018): 961. http://dx.doi.org/10.3390/w10070961.

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River morphological evolution is a challenging topic, involving hydrodynamic flow, sediment transport and bank stability. Lowland rivers are often characterized by the coexistence of granular and cohesive material, with significantly different behaviours. This paper presents a bidimensional morphological model to describe the evolution of the lower course of rivers, where there are both granular and cohesive sediments. The hydrodynamic equations are coupled with two advection–diffusion equations, which consider the transport of granular and cohesive suspended sediment concentration separately. The change of bed height is evaluated as the sum of the contributions of granular and sediment material. A bank failure criterion is developed and incorporated into the numerical simulation of the hydrodynamic flood wave and channel evolution, to describe both bed deformation and bank recession. To this aim, two particular mechanisms are considered: the former being a lateral erosion due to the current flow and consequent cantilever collapse and the latter a geostatic failure due to the submergence. The equation system is integrated by means of a finite volume scheme. The resulting model is applied to the Tagliamento River, in northern Italy, where the meander migration is documented through a sequence of aerial images. The channel evolution is simulated, imposing an equivalent hydrograph consisting of a sequence of flood waves, which represents a medium year, with reference to their effect on sediment transport. The results show that the model adequately describes the general morphological evolution of the meander.

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Koroleva, K. S., und I. I. Potapov. „EVOLUTION OF BED FORMS PRODUCED BY CLARIFIED TURBULENT FLOW OVER A NON-COHESIVE BED“. Journal of Applied Mechanics and Technical Physics 63, Nr. 1 (Februar 2022): 67–74. http://dx.doi.org/10.1134/s0021894422010114.

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30

Hamidifar, Hossein, und Mohammad Hossein Omid. „Local scour of cohesive beds downstream of a rigid apron“. Canadian Journal of Civil Engineering 44, Nr. 11 (November 2017): 935–44. http://dx.doi.org/10.1139/cjce-2016-0398.

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In this paper, the physics of scour hole in a mixed sand–clay bed downstream of an apron is studied experimentally. Seven combinations of sand–clay mixtures including clay contents, Cc, ranging from 0 to 0.4 were used. The results show that Cc = 0.4 can reduce the maximum scour depth, εm, up to about 80% for all the densimetric Froude numbers in the range of the present study. An empirical equation has been proposed for calculation of εm in sand–clay mixtures with the mean error of 0.12. The removal mechanism of sediments from the bed was different based on the Cc. For low clay contents, i.e., Cc ≤ 15%, individual particles were detached from the bed. At higher Cc, clusters of particles were separated and moved downstream with the flow. A new equation has been proposed to predict the dimensionless scour hole profile in mixed sand–clay sediments. Dimensionless graphs have been presented for incorporating the effect of tailwater depth and sediment grain size on the main characteristics lengths in sand–clay mixtures.

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Güven, Oktay, Joel G. Melville und John E. Curry. „Analysis of Clear-Water Scour at Bridge Contractions in Cohesive Soils“. Transportation Research Record: Journal of the Transportation Research Board 1797, Nr. 1 (Januar 2002): 3–10. http://dx.doi.org/10.3141/1797-01.

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A new, simplified theory for the analysis of the time-dependent development of the depth of scour at bridge contractions in cohesive soils under clear-water conditions is presented. The new theory is an extension of the clear-water scour theory for a long contraction currently used for non-cohesive bed materials. It is based on the “scour rate in cohesive soils” concepts introduced recently by Briaud and his colleagues at Texas A&M University. A description of the simplifying assumptions made in the development of the theory and several applications with different bed soils and flow conditions are presented to illustrate the effects of various assumptions on the estimate of the scour depth. Limitations of the theory are also discussed. The results indicate that a very long time may be required in some cohesive soils for the scour depth to reach its maximum value for a given flow condition. The results also indicate that significant differences in the estimate of the scour depth may occur depending on the assumptions made about the behavior of the water surface elevation and the total head in the contraction during the development of the scour in the contraction.

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N., Mohd Radzuan, Anuar M.S. und S. M. Tahir. „The mixing of cohesive and flowable powder materials using a common laboratory powder mixer“. Supplementary 1 5, S1 (03.01.2021): 19–24. http://dx.doi.org/10.26656/fr.2017.5(s1).004.

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This study presented the homogeneity obtained when mixing cohesive and flowable powder materials using a laboratory powder mixer. The mixing process parameters studied were the mixing time and the mixer rotational speed (20 rpm, 40 rpm and 60 rpm) at the different ratios (95%: 5%, 50%: 50% and 5%: 95%) of the cohesive cocoa and flowable mannitol powder materials. The homogeneity sampled at the powder bed surface showed that only at the highest rotational speed of 60 rpm used in this work yield acceptable homogeneity at the two extremes of the powder mass ratios; 95%: 5% and 5%: 95% of mannitol: cocoa for some of the locations on the powder bed surface, especially near the wall of the mixer. Other combinations of the experimental conditions did not yield acceptable mixture homogeneity. These results showed the difficulties in obtaining a homogeneous powder mix when mixing cohesive powder materials, especially in academic teaching and research laboratories using a simple powder mixer apparatus.

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Kleijwegt, Rob A. „On the Prediction of Sediment Transport in Sewers with Deposits“. Water Science and Technology 27, Nr. 5-6 (01.03.1993): 69–80. http://dx.doi.org/10.2166/wst.1993.0487.

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There is a need for models to predict the negative effects of sewer deposits in order to improve design, maintenance and operation of sewerage systems. The lack of success of deterministic sewer sediment models in the past is caused by a lack of basic knowledge, which causes unknown uncertainties in the model's results. The basic knowledge about non-cohesive sediment transport has been studied with laboratory experiments. This has resulted in an understanding of the non-cohesive sewer sediment transport and the related subjects of bed shear stress, incipient motion, bed forms and flow resistance. This understanding can be used in the development of deterministic models for sewer systems. However, the next objective will be to develop probabilistic models.

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Govender, Preyin, Deborah Clare Blaine und Natasha Sacks. „INFLUENCE OF POWDER CHARACTERISTICS ON THE SPREADABILITY OF PRE-ALLOYED TUNGSTEN- CARBIDE COBALT“. South African Journal of Industrial Engineering 32, Nr. 3 (2021): 284–89. http://dx.doi.org/10.7166/32-3-2664.

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With rising interest in additive manufacturing (AM) techniques, there is an increased focus on research that evaluates critical parameters that guide the selection of powders that are suitable for AM. One such parameter is a powder’s spreadability, described by metrics such as powder bed density and percentage coverage. This study focused on three spray-dried WC-Co powders (two 12 wt% and one 17 wt% Co) and evaluated the influence of typical powder characteristics, such as particle size and shape, apparent density, and flow rate, on their spreadability. It was found that particle size distribution influenced the powder spreadability. Larger particles hindered the even spreading of powder over the base plate, resulting in low powder bed density and percentage coverage. This also correlated with the powders’ apparent densities. The flow rate and angle of repose gave an indication of how cohesive the powders are. The more cohesive a powder, the poorer the spreadability, resulting in a lower powder bed density and percentage coverage.

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Sahin, Cihan, Ilgar Safak, Alexandru Sheremet und Ashish J. Mehta. „Observations on cohesive bed reworking by waves: Atchafalaya Shelf, Louisiana“. Journal of Geophysical Research: Oceans 117, Nr. C9 (September 2012): n/a. http://dx.doi.org/10.1029/2011jc007821.

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36

Rehman, Z., A. Akbar und B. G. Clarke. „Characterization of a Cohesive Soil Bed using a Cone Pressuremeter“. Soils and Foundations 51, Nr. 5 (Oktober 2011): 823–33. http://dx.doi.org/10.3208/sandf.51.823.

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37

Amos, C. L., T. F. Sutherland, D. Cloutier und S. Patterson. „Corrasion of a remoulded cohesive bed by saltating littorinid shells“. Continental Shelf Research 20, Nr. 10-11 (Juli 2000): 1291–315. http://dx.doi.org/10.1016/s0278-4343(00)00024-8.

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Xu, Huibin, Wenqi Zhong, Zhulin Yuan und A. B. Yu. „CFD-DEM study on cohesive particles in a spouted bed“. Powder Technology 314 (Juni 2017): 377–86. http://dx.doi.org/10.1016/j.powtec.2016.09.006.

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39

Helland, Eivind, René Occelli und Lounès Tadrist. „Numerical study of cohesive powders in a dense fluidized bed“. Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics-Physics-Astronomy 327, Nr. 14 (Dezember 1999): 1397–403. http://dx.doi.org/10.1016/s1287-4620(00)87511-0.

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40

Mikami, Takafumi, Hidehiro Kamiya und Masayuki Horio. „Numerical simulation of cohesive powder behavior in a fluidized bed“. Chemical Engineering Science 53, Nr. 10 (Mai 1998): 1927–40. http://dx.doi.org/10.1016/s0009-2509(97)00325-4.

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41

Chen, Yuhua, Jun Yang, Ajit Mujumdar und Rajesh Dave. „Fluidized bed film coating of cohesive Geldart group C powders“. Powder Technology 189, Nr. 3 (Februar 2009): 466–80. http://dx.doi.org/10.1016/j.powtec.2008.08.002.

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42

Camenen, Benoît, und Magnus Larson. „A general formula for non-cohesive bed load sediment transport“. Estuarine, Coastal and Shelf Science 63, Nr. 1-2 (April 2005): 249–60. http://dx.doi.org/10.1016/j.ecss.2004.10.019.

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43

Tatemoto, Yuji, Yoshihide Mawatari und Katsuji Noda. „Numerical simulation of cohesive particle motion in vibrated fluidized bed“. Chemical Engineering Science 60, Nr. 18 (September 2005): 5010–21. http://dx.doi.org/10.1016/j.ces.2005.03.058.

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44

Ishikura, Toshifumi, Hiroshi Nagashima und Mitsuharu Ide. „Behaviour of Cohesive Powders in a Powder-Particle Spouted Bed“. Canadian Journal of Chemical Engineering 82, Nr. 1 (19.05.2008): 102–9. http://dx.doi.org/10.1002/cjce.5450820113.

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45

Nalluri, C., und E. M. Alvarez. „The Influence of Cohesion on Sediment Behaviour“. Water Science and Technology 25, Nr. 8 (01.04.1992): 151–64. http://dx.doi.org/10.2166/wst.1992.0189.

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This paper describes the results of a laboratory study financed by the Science and Engineering Research Council (SERC), UK. The work was carried out at the University of Newcastle upon Tyne in collaboration with the Water Research Centre's (WRc) River Basin Management Project during the period 1987-90. The present study has covered hydraulics, deposition, erosion and sediment transport, all with deposited bed. Noncohesive sands and sewer sediment analogues (with cohesive additives to sand) have been used and throughout the study comparisons between cohesive and noncohesive sediments were made. The noncohesive sediment studies suggested that the initiation of erosion and transport rates criteria in channels of circular cross-section using bed shear stress are comparable to those of wide channels. The sewer sediment analogues corresponding to type A needed a maximum mean shear stress of around 6-7 N/m2 whereas a weaker sediment (type C) needed only around 2.5 N/m2. The chosen cohesive analogues behaved as noncohesive sediments once they started moving, perhaps a phenomenon close to reality.

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PARKER, GARY, und NORIHIRO IZUMI. „Purely erosional cyclic and solitary steps created by flow over a cohesive bed“. Journal of Fluid Mechanics 419 (25.09.2000): 203–38. http://dx.doi.org/10.1017/s0022112000001403.

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An erodible surface exposed to supercritical flow often devolves into a series of steps that migrate slowly upstream. Each step delineates a headcut with an associated hydraulic jump. These steps can form in a bed of cohesive material which, once eroded, is carried downstream as washload without redeposition. Here the case of purely erosional, one-dimensional periodic, or cyclic steps in cohesive material is considered. The St. Venant shallow-water equations combined with a formulation for sediment erosion are used to construct a complete theory of the erosional case. The solution allows wavelength, wave height, migration speed and bed and water surface profiles to be determined as functions of imposed parameters. The analysis also admits a solution for a solitary step, or single headcut of self-preserving form.

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Pradhan, S., R. N. Samal, S. B. Choudhury und P. K. Mohanty. „HYDRODYNAMIC AND COHESIVE SEDIMENT TRANSPORT MODELING IN CHILIKA LAGOON“. ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-5 (15.11.2018): 141–49. http://dx.doi.org/10.5194/isprs-annals-iv-5-141-2018.

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Abstract. Chilika lagoon, one of the largest brackish water lagoons in Asia located along the east coast of India. The rivers draining into the lagoon carry about 13 million tonnes of sediments annually. Because of the cohesiveness properties of the fine sediments, nutrients, heavy metals and other polluted substances tend to bind to the sediment’s surface. Consequently, pollutants can be concentrated in the inlets/estuaries, thus being of great environmental interest. In addition, the mudflats occurring are important biotopes for a large number of micro- and macro-faunal species and act as feeding places for a number of birds. To understand the cohesive sediment dynamics, a numerical model, MIKE 21 Mud Transport (MT) coupled with hydrodynamic (HD) was used. The model simulated the relative bed level height and suspended sediment concentrations. The sediment interchange and accumulation between each sectors and Bay of Bengal were evaluated. The suspended sediment concentration is high in the north-east portion of the lagoon while medium and low suspended loads are observed in the eastern and western portion of the lagoon. Bed thickness is very high in the north-western corner of the lagoon covered with Phragmites Karka which facilitate sediment trap. Total bed thickness change is very much pronounced in the northern sector which receives most of the sediments from the Mahanadi river systems as well along the periphery of the lagoon due to drainage. The eastern lagoon shows a net deposition accumulated fraction (5–15kg/m2) and hence gives enough indication of the sedimentation processes in the lagoon. Further, the results also warrant immediate attention to check and monitor suspended sediment concentration to find out the net deposition trend in the lagoon environment in order to take decisions in minimizing the sediment load.

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Noya, Yunita A., Mulia Purba, Alan F. Koropitan und Tri Prartono. „COHESIVE SEDIMENT TRANSPORT MODELING ON INNER AMBON BAY“. Jurnal Ilmu dan Teknologi Kelautan Tropis 8, Nr. 2 (06.04.2017): 671–87. http://dx.doi.org/10.29244/jitkt.v8i2.15834.

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The presence of cohesive sediment in the water column can reduce light penetration and affect photosynthesis process, and it can be disrupted the primary productivity of aquatic, and sedimentation of coastal waters. The objective of this research was to determine the cohesive sediment distribution pattern and the relationship with sedimentation. MIKE 3 FM modeling was used to understand the process of sediment transport and sedimentation on Inner Ambon Bay. Sediment transport modeling method was divided into two stages: the hydrodynamic modeling (baroclinic) and sediment transport (mud transport) modeling. The model results indicate current patterns in the Inner Ambon Bay is influenced by the tidal factor. Suspended sediment dispersed vertically from the surface to a depth of 30 m with concentration of about 3.5-15 Kg/m3. The maximum consentration of the suspended sediment occurs at head of the bay (around Waiheru, Passo, and Lateri). Model simulations for 30 days showed the rate of erosion is about 1.04-6.15 Kg/m2/s, while in Inner Ambon Bay the erosion about 9.07x10-8Kg/m2/s only occurred in T1 station. Sedimentation associated with the cohesive sediment accumulation and it was shown by bed level. In addition, the simulation showed bed level in sill ranged at 0.01-0.19 cm and 0.47 mm/day on average, while in the Inner Ambon Bay it ranged from 1.75-10.01 cm, and the sedimentation rate was approximately 39.9 mm/day.

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Wu, Xuxu, Jonathan Malarkey, Roberto Fernández, Jaco H. Baas, Ellen Pollard und Daniel R. Parsons. „Influence of cohesive clay on wave–current ripple dynamics captured in a 3D phase diagram“. Earth Surface Dynamics 12, Nr. 1 (30.01.2024): 231–47. http://dx.doi.org/10.5194/esurf-12-231-2024.

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Abstract. Wave–current ripples that develop on seabeds of mixed non-cohesive sand and cohesive clay are commonplace in coastal and estuarine environments. While laboratory research on ripples forming in these types of mixed-bed environments is relatively limited, it has identified deep cleaning, the removal of clay below the ripple troughs, as an important factor controlling ripple development. New large-scale flume experiments seek to address this sparsity in data by considering two wave–current conditions with initial clay content, C0, ranging from 0 % to 18.3 %. The experiments record ripple development and pre- and post-experiment bed clay contents to quantify clay winnowing. The present experiments are combined with previous wave-only, wave–current, and current-only experiments to produce a consistent picture of larger and smaller flatter ripples over a range of wave–current conditions and C0. Specifically, the results reveal a sudden decrease in the ripple steepness for C0 > 10.6 %, likely associated with a decrease in hydraulic conductivity of 3 orders of magnitude. Accompanying the sudden change in steepness is a gradual linear decrease in wavelength with C0 for C0 > 7.4 %. Ultimately, for the highest values of C0, the bed remains flat, but clay winnowing still takes place, albeit at a rate 2 orders of magnitude lower than for rippled beds. For a given flow, the initiation time, when ripples first appear on a flat bed, increases with increasing C0. This, together with the fact that the bed remains flat for the highest values of C0, demonstrates that the threshold of motion increases with C0. The inferred threshold enhancement, and the occurrence of large and small ripples, is used to construct a new three-dimensional phase diagram of bed characteristics involving the wave and current Shields parameters and C0, which has important implications for morphodynamic modelling.

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Ashley, R. M., D. J. J. Wotherspoon, M. J. Goodison, I. McGregor und B. P. Coghlan. „The Deposition and Erosion of Sediments in Sewers“. Water Science and Technology 26, Nr. 5-6 (01.09.1992): 1283–93. http://dx.doi.org/10.2166/wst.1992.0571.

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The problems caused by sediments in sewers are now universally acknowledged. A number of countries have set up comprehensive programmes to study all aspects of sewer sediments; their occurrence, nature and movement. In the UK the Water Research centre and others have funded a comprehensive study of the sediments in the Dundee sewer system. The rate of sedimentation and the yield strength of the sediments have been investigated and considered in terms of the subsequent erosion by increasing flows. The sediments have been found to be cohesive in nature and highly resistant to erosion in the main interceptor sewer, whereas in the trunk sewers the sediments are more granular and less cohesive in nature. A sewer classification system is suggested which is based on physical characteristics, and also relates to the nature of the sediments deposited, and the bed-load material conveyed close to the bed.

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