Experiment on Incipient Motion of Clayey Silt in the Main Channel of Xuwei Harbor, Lianyungang under Wave-Current Action

2014 ◽  
Vol 638-640 ◽  
pp. 1247-1251
Author(s):  
Yan Li ◽  
Hui Xiao
Keyword(s):  
Shear Stress ◽  
Main Channel ◽  
Bed Sediment ◽  
Incipient Motion ◽  
Current Action ◽  
Clayey Silt ◽  
Current Interaction ◽  
Depth Water ◽  
Sediment Incipient Motion

For two sampling sediment take from the-3m and-5m depth water in the main channel of Xuwei port, Lianyungang, the experiment of sediment incipient motion under wave-current interaction is carried out in a wave-current flume. The results show that the wet density of bed sediment is 1.4 t/m3 and 1.5 t/m3 respectively, the critical incipient shear stress at the bottom of the bed is between 0.21 N/m2~ 0.29 N/m2 and 0.35 N/m2 ~ 0.46 N/m2 respectively; the critical incipient shear stress of sediment from-3m depth water is greater than from the-5m depth water for the same wet density of bed sediment. The results can provide parameters and basis to the research of engineering sediment problem.

scholarly journals Effects of relative submergence and bed slope on sediment incipient motion under decelerating flows

2015 ◽  
Vol 63 (4) ◽  
pp. 295-302 ◽  
Author(s):  
Ramin Bolhassani ◽  
Hossein Afzalimehr ◽  
Subhasish Dey
Keyword(s):  
Experimental Study ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Incipient Motion ◽  
Grain Sizes ◽  
Bed Slope ◽  
Sediment Incipient Motion

Abstract This paper presents the results of an experimental study to quantify the effects of bed slope and relative submergence on incipient motion of sediment under decelerating flows. Experiments were conducted in an experimental tilting-flume of 8 m long 0.4 m wide and 0.6 m deep with glass-walls. Three uniform sediments with median grain sizes of 0.95, 1.8 and 3.8 mm and three bed slopes of 0.0075, 0.0125 and 0.015 were used under decelerating flow. The main conclusion is that the Shields diagram, which is commonly used to evaluate the critical shear stress, is not suitable to predict the critical shear stress under decelerating flows.

scholarly journals Prediction of Boundary Shear Stress Distribution in Converging Compound Channel Using Gene Expression Programming

2022 ◽  
Author(s):  
Bandita Naik ◽  
Vijay Kaushik ◽  
Munendra Kumar
Keyword(s):  
Shear Stress ◽  
Stress Distribution ◽  
Shear Force ◽  
Gene Expression Programming ◽  
Main Channel ◽  
Shear Stress Distribution ◽  
Force Distribution ◽  
Compound Channel ◽  
Boundary Shear ◽  
Boundary Shear Stress

Abstract The computation of the boundary shear stress distribution in an open channel flow is required for a variety of applications, including the flow resistance relationship and the construction of stable channels. The river breaches the main channel and spills across the floodplain during overbank flow conditions on both sides. Due to the momentum shift between the primary channel and adjacent floodplains, the flow structure in such compound channels becomes complicated. This has a profound impact on the shear stress distribution in the floodplain and main channel subsections. In addition, agriculture and development activities have occurred in floodplain parts of a river system. As a consequence, the geometry of the floodplain changes over the length of the flow, resulting in a converging compound channel. Traditional formulas, which rely heavily on empirical approaches, are ineffective in predicting shear force distribution with high precision. As a result, innovative and precise approaches are still in great demand. The boundary shear force carried by floodplains is estimated by gene expression programming (GEP) in this paper. In terms of non-dimensional geometric and flow variables, a novel equation is constructed to forecast boundary shear force distribution. The proposed GEP-based method is found to be best when compared to conventional methods. The findings indicate that the predicted percentage shear force carried by floodplains determined using GEP is in good agreement with the experimental data compared to the conventional formulas (R2 = 0.96 and RMSE = 3.395 for the training data and R2 = 0.95 and RMSE = 4.022 for the testing data).

Study on Incipient Motion of Consolidated Cohesive Fine Sediment

2012 ◽  
Vol 204-208 ◽  
pp. 354-358
Author(s):  
Jun Wang ◽  
Wei Guo ◽  
Hai Tao Xu ◽  
Zhong Wu Jin ◽  
Yin Jun Zhou
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Fine Sediment ◽  
Weight Increase ◽  
Unit Weight ◽  
Incipient Motion ◽  
Mean Particle Size ◽  
Dry Unit Weight ◽  
The One

The incipient motion mechanism of cohesive fine sediment is different to the one of non-cohesive sediment. It is related to the consolidation while being influenced by the dry unit weight and particle size. By means of the rectangle piping flume, the influence mechanism of dry unit weight and particle size to critical shear stress of cohesive fine sediment is studied. Experimental results show that on the condition of consolidation, the influence of dry unit weight to incipient motion is divided into two different stages, one is that when dry unit weight increase quickly, but the influence to incipient motion is not greatly, another is that when dry unit weight increase slowly, but the influence to incipient motion is very greatly, the critical dry unit weight to two stages decline as mean particle size decrease. So the mean particle size is finer, the degree of dry unit weight influence to critical shear stress is stronger, and the incipient motion is more difficult when consolidation last longer; it is also shown consolidation is more disadvantageous to incipient motion.

scholarly journals Experimental study on incipient shear stress of consolidated cohesive sediment

2020 ◽  
Vol 13 (18) ◽  
Author(s):  
Caiwen Shu ◽  
Guangming Tan ◽  
Peng Chen ◽  
Jun Wang ◽  
Ping Lv
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Bulk Density ◽  
Cohesive Sediment ◽  
Experimental Results ◽  
Incipient Motion ◽  
Motion Mechanism ◽  
Cohesive Particles ◽  
Sediment Mixtures ◽  
Consolidation Time

Abstract This paper analyzes the incipient motion mechanism of consolidated cohesive sediment. An experimental device based on previous studies was designed to investigate the influencing factors of the incipient shear stress, including the consolidation time, the density of dry bulk, cohesive particles content, and the composition of sediment mixtures. The experimental results indicated that the incipient shear stress of cohesive sediment increased with the increase of consolidation time, dry bulk density, and content of cohesive particles. The incipient motion mechanism of cohesive particles was further investigated using experimental data and theoretical analysis. A formula of the incipient shear stress for cohesive sediment was proposed herein, which is related to both the content of cohesive particles and the relative dry bulk density. The proposed formula was validated by the experimental data, and the calculated values of incipient shear stress using the formula were in good agreement with the experimental results.

STABILISATION OF OFFSHORE MARINE PIPELINES BY DUMPED STONE

2002 ◽  
Vol 42 (1) ◽  
pp. 537
Author(s):  
W. Lipski ◽  
J.B. Hinwood
Keyword(s):  
Shear Stress ◽  
Scale Model ◽  
Downstream Face ◽  
Bed Shear Stress ◽  
Design Chart ◽  
Current Action

Tests were carried out on a scale model of a rock berm in a wave-current flume to determine the resistance of the berm to damage from combined wave and current action. The range of tests covered many of the situations possible in the field and serves to aid in the design of pipeline protection systems.Two distinct mechanisms of berm damage were observed. The first was damage on the downstream face of the berm caused by the formation of a vortex and the second was damage due to excessive bed shear stress causing rocks to dislodge from the berm. These mechanisms can occur individually or simultaneously to cause unacceptable damage to the berm.The results are presented as a design chart, indicating under what conditions damage to a rock berm can be expected to occur and the extent of the expected damage where it does occur.

In situ observation of the water-sediment interface in combined sewers, using endoscopy

2003 ◽  
Vol 47 (4) ◽  
pp. 11-18 ◽  
Author(s):  
C. Oms ◽  
M.-C. Gromaire ◽  
G. Chebbo
Keyword(s):  
Shear Stress ◽  
Small Diameter ◽  
Organic Layer ◽  
In Situ Observation ◽  
Bed Shear Stress ◽  
Bed Sediment ◽  
Plastic Tube ◽  
Non Destructive ◽  
Sediment Interface

A new method for water-sediment interface observation has been designed. This system is based on a small diameter endoscope protected by a graduated plastic tube. It makes it possible to visualise in a non-destructive manner the sediments and the water-sediment interface. The endoscope was used to investigate Le Marais catchment (Paris): an immobile organic layer was observed at the water-sediment interface. This layer appears in pools of gross bed sediment, at the upstream of collectors, in zones where velocity is slow and where bed shear stress is less than 0.03 N/m2.

scholarly journals Experimental study on incipient condition of fluidized bed sediment in oscillatory

2019 ◽  
Vol 81 ◽  
pp. 01014
Author(s):  
Rui Wang ◽  
Guoliang Yu
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Fluidized Bed ◽  
Oscillatory Flow ◽  
Critical Shear Stress ◽  
Cohesive Sediments ◽  
Bed Sediment ◽  
The Relationship ◽  
Experimental Runs ◽  
Water Contents

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.

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