Line 7: Line 7:
 
'''Keywords:''' Scour''',''' 2D average velocity; RIVER 2D model, scour depth
 
'''Keywords:''' Scour''',''' 2D average velocity; RIVER 2D model, scour depth
  
−
==2 The main text<!-- You can enter and format the text of this document by selecting the ‘Edit’ option in the menu at the top of this frame or next to the title of every section of the document. This will give access to the visual editor. Alternatively, you can edit the source of this document (Wiki markup format) by selecting the ‘Edit source’ option.
+
=='''2. Methods of calculating bridge pier scour'''==
  
−
Most of the documents in Scipedia are written in English (write your manuscript in American or British English, but not a mixture of these). Anyhow, specific publications in other languages can be published in Scipedia. In any case, the documents published in other languages must have an abstract written in English.
+
'''2.1 Calculation of pier scour by the method of using 1D average velocity.'''
  
 +
'''General scour.'''
  
−
2.1 Subsections
+
O.V.Andreev (1955) [7] proposed a method to calculate the maximum general scour under the bridge (lower limit of scour) based on the analysis of the movement of alluvium particles in the mainstream and the river beach below the bridge. In the river beach part under the bridge, scour only starts when the velocity of water flowing under the bridge is greater than the allowed non-scour velocity (v<sub>ox</sub>) of the geological soil layer forming the river beach (v<sub>bc</sub>>v<sub>ox</sub>) and the scour will stop when the flow rate decreases to the allowed non-scour rate. In the mainstream, the flow rate is always greater than the allowable rate of non- scour of the riverbed’s geological layer and therefore the topsoil layer of the riverbed is always in a state of motion, but the river is not deeply eroded because there is a balance of alluvium along the river. Thus, the flow rate under the bridge is greater than the allowable rate without erosion, which is not the cause of scour in the mainstream and the deformation of the river under the bridge can only be explained by the imbalance of alluvium along the river. The overall scour under the bridge is calculated according to the principle of balance of sediment limit for the mainstream and the flow part with alluvium transport of O.V.Andreev (1955) [7]. The flow depth after scouring is determined according to equation (1) .
  
−
Divide your article into clearly defined and numbered sections. Subsections should be numbered 1.1, 1.2, etc. and then 1.1.1, 1.1.2, ... Use this numbering also for internal cross-referencing: do not just refer to 'the text'. Any subsection may be given a brief heading. Capitalize the first word of the headings.
+
Where:  
  
 +
+ Q<sub>1</sub>=Q<sub>ch</sub>, Q<sub>2</sub>=Q'<sub>ch</sub>: Water flow before and after bridge construction at the mainstream.
  
−
2.2 General guidelines
+
+ h<sub>ch</sub>, h'<sub>ch</sub> : Water depth at mainstream before (natural time) and after scouring.
  
−
Some general guidelines that should be followed in your manuscripts are:
+
h<sub>ch</sub> = ▼h<sub>hm</sub> – ▼h<sub>tbs</sub>
  
−
*  Avoid hyphenation at the end of a line.
+
▼h<sub>hm</sub>: Elevation of flow rate at natural time (taken according to design frequency)
  
−
*  Symbols denoting vectors and matrices should be indicated in bold type. Scalar variable names should normally be expressed using italics.
+
▼h<sub>tbs</sub>: average elevation of the riverbed
  
−
*  Use decimal points (not commas); use a space for thousands (10 000 and above).
+
+ B<sub>ch</sub>, B'<sub>ch</sub>: Mainstream width before and after bridge construction.
  
−
*  Follow internationally accepted rules and conventions. In particular use the international system of units (SI). If other quantities are mentioned, give their equivalent in SI.
+
B<sub>ch</sub> = L<sub>0</sub> = 1657.34m.
  
 +
B'<sub>ch</sub> = L = 1401.5 m.
  
−
2.3 Tables, figures, lists and equations
+
Calculation results of general scour depth according to table 1
 +
''Table 1. Table of results for calculating the general scour depth of piers located on the main stream according to the 1D average velocity method.''
 +
{| class="MsoNormalTable"
 +
 +
  |
 +
<nowiki>  </nowiki>Bridge Piers
 +
 
 +
  |
 +
<nowiki>  </nowiki>Bottom elevation
 +
 
 +
(m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Surface elevation
 +
 
 +
(m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Water Depth before scour
 +
 
 +
h<sub>ch</sub>
 +
 
 +
(m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Water Depth after scour
 +
 
 +
h'<sub>ch</sub>
 +
 
 +
(m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Rising water
 +
 
 +
(m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>General depth scour (m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Bottom elevation after local scour (m) 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T3
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.500
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.330
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.504
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.235
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.735 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T4
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.250
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.080
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.293
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.274
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.524 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T5
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.240
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.070
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.283
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.274
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.514 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T6
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.210
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.040
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.251
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.272
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.482 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T7
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.960
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.790
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.988
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.259
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.219 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T8
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.420
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.250
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.472
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.283
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.703 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T9
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.720
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.550
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.788
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.299
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.019 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T10
 +
 
 +
  |
 +
<nowiki>  </nowiki>-1.900
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.730
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.977
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.308
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.208 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T11
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.050
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.880
 +
 
 +
  |
 +
<nowiki>  </nowiki>5.135
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.316
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.366 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T12
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.540
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>5.370
 +
 
 +
  |
 +
<nowiki>  </nowiki>5.651
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.342
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.882 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T13
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.630
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>5.460
 +
 
 +
  |
 +
<nowiki>  </nowiki>5.745
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.346
 +
 
 +
  |
 +
<nowiki>  </nowiki>-2.976 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T14
 +
 
 +
  |
 +
<nowiki>  </nowiki>-3.400
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>6.230
 +
 
 +
  |
 +
<nowiki>  </nowiki>6.556
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.387
 +
 
 +
  |
 +
<nowiki>  </nowiki>-3.787 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T15
 +
 
 +
  |
 +
<nowiki>  </nowiki>-8.150
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>10.980
 +
 
 +
  |
 +
<nowiki>  </nowiki>11.554
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.635
 +
 
 +
  |
 +
<nowiki>  </nowiki>-8.785 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T16
 +
 
 +
  |
 +
<nowiki>  </nowiki>-11.600
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>14.430
 +
 
 +
  |
 +
<nowiki>  </nowiki>15.184
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.815
 +
 
 +
  |
 +
<nowiki>  </nowiki>-12.415 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T17
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.260
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.570
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.652
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.143
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.117 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T18
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.000
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.978
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.209
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.209 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T19
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.050
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.880
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.031
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.212
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.262 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T20
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.040
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.790
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.936
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.207
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.167 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T21
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.040
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.830
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.870
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.020
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.211
 +
 
 +
  |
 +
<nowiki>  </nowiki>-0.251 
 +
 +
|}
  
−
Please insert tables as editable text and not as images. Tables should be placed next to the relevant text in the article. Number tables consecutively in accordance with their appearance in the text and place any table notes below the table body. Be sparing in the use of tables and ensure that the data presented in them do not duplicate results described elsewhere in the article.
+
'''Caculating local Scour (p = 1%)'''
  
−
Graphics may be inserted directly in the document and positioned as they should appear in the final manuscript.
+
Two authors N.X Truc and N.H. Khai (1982) [8] introduced the formula for determining the largest local scour value at the bridge pier. Based on the research results on the causes and development process of local scour on pier scour models in the hydraulic laboratory and the research results of foreign authors, a reasonable structural form of the local scour calculation formula has been selected. The formula (2) has the following simple form. When v³ v<sub>ox</sub> (for mainstream piers). 
  
−
Number the figures according to their sequence in the text. Ensure that each illustration has a caption. A caption should comprise a brief title. Keep text in the illustrations themselves to a minimum but explain all symbols and abbreviations used. Try to keep the resolution of the figures to a minimum of 300 dpi. If a finer resolution is required, the figure can be inserted as supplementary material
+
h<sub>cb</sub>= 0,52.k<sub>d</sub>.b<sup>0,88</sup>.h<sup>0,12</sup>.(V/V<sub>ox</sub>)<sup>1,16</sup>                                                                                  (2)
  
−
For tabular summations that do not deserve to be presented as a table, lists are often used. Lists may be either numbered or bulleted. Below you see examples of both.
+
Where:
  
−
1. The first entry in this list
+
+ h<sub>cb</sub>: maximum local scour depth at bridge pier, m 
  
−
2. The second entry
+
+ k<sub>d</sub>: factor taking into account the influence of cylinder shape, taken as  0,1k<sub>ζ</sub>
  
−
2.1. A subentry
+
+ k<sub>ζ</sub> : Iaratslaxev's shape coefficient    
  
−
3. The last entry
+
+ h: depth of water flow at bridge pier before local scour, m 
  
−
* A bulleted list item
+
+ V: water velocity at bridge pier before local scour, m/s
  
−
* Another one
+
+ V<sub>ox</sub>  : allowable no- scour velocity of the soil layer at the location where scour development  
−
 
+
−
You may choose to number equations for easy referencing. In that case they must be numbered consecutively with Arabic numerals in parentheses on the right hand side of the page. Below is an example of formulae that should be referenced as eq. (1].
+
−
 
+
−
 
+
−
2.4 Supplementary material
+
−
 
+
−
Supplementary material can be inserted to support and enhance your article. This includes video material, animation sequences, background datasets, computational models, sound clips and more. In order to ensure that your material is directly usable, please provide the files with a preferred maximum size of 50 MB. Please supply a concise and descriptive caption for each file. -->==
+
  
 +
+ b: calculated width of the cylinder, m
  
 +
The results of local scour calculation are obtained from Table 2
  
 +
''Table 2. Table of results of calculation of local scour depth of piers located on the main stream according to the average 1D velocity method.''
 +
{| class="MsoNormalTable"
 +
 +
  |
 +
<nowiki>  </nowiki>Bridge Piers
 +
 
 +
  |
 +
<nowiki>  </nowiki>Shape factor
 +
 
 +
K<sub>d</sub>
 +
 
 +
  |
 +
<nowiki>  </nowiki>Width of pier
 +
 
 +
b (m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Depth of water flow
 +
 
 +
h (m)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Velocity
 +
 
 +
V (m/s)
 +
 
 +
  |
 +
<nowiki>  </nowiki>No-scour velocity Vox (m/s)
 +
 
 +
  |
 +
<nowiki>  </nowiki>Ratio
 +
 
 +
V/Vox
 +
 
 +
  |
 +
<nowiki>  </nowiki>Maximum local scour depth
 +
 
 +
h<sub>cb</sub> (m) 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T3
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.97
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.8
 +
 
 +
  |
 +
<nowiki>  </nowiki>3.565
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.484
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.720
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.061
 +
 
 +
  |
 +
<nowiki>  </nowiki>2.280 
 +
 +
|-
 +
  |
 +
<nowiki>  </nowiki>T4
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.97
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.8
 +
 
 +
  |
 +
<nowiki>  </nowiki>4.354
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.484
 +
 
 +
  |
 +
<nowiki>  </nowiki>0.790
 +
 
 +
  |
 +
<nowiki>  </nowiki>1.878
 +
 
 +
  |
 +
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==3 Bibliography<!--  
 
==3 Bibliography<!--  

Revision as of 07:32, 29 July 2023

  • Abstract:  When the Cua Dai bridge is built across the Thu Bon River, it causes a narrowing of the flow leading to scour, which seriously threatens the pier and endangers the structure. In order to limit the influence of scour the bridge, it is necessary to ensure that the scour under the bridge is within the allowable range. At the same time, it is necessary to take measures to limit and overcome the causes of scour. Therefore, the study and prediction of locations that are likely to cause scour are of great significance in choosing effective and versatile prevention solutions for works on this river section. Most of the scour formulas for bridge use the 1D average velocity to calculate; The calculated results are much different from the real distribution of flow velocity in the river. Therefore, the results of scour calculation often have big deviations from reality, especially when the river cross-section has no flats or curved rivers... The article focuses on researching scour at the bridge pier based on the two-dimensional horizontal velocity in front of the pier by using RIVER 2D model, built from the mathematical model of two horizontal flows and solved by the finite element method. The results of the paper show that the scour depth of pier by the one-dimensional (1D) average velocity gives much larger than when applying the two-dimensional horizontal velocity to calculate the scour.

Keywords: Scour, 2D average velocity; RIVER 2D model, scour depth

2. Methods of calculating bridge pier scour

2.1 Calculation of pier scour by the method of using 1D average velocity.

General scour.

O.V.Andreev (1955) [7] proposed a method to calculate the maximum general scour under the bridge (lower limit of scour) based on the analysis of the movement of alluvium particles in the mainstream and the river beach below the bridge. In the river beach part under the bridge, scour only starts when the velocity of water flowing under the bridge is greater than the allowed non-scour velocity (vox) of the geological soil layer forming the river beach (vbc>vox) and the scour will stop when the flow rate decreases to the allowed non-scour rate. In the mainstream, the flow rate is always greater than the allowable rate of non- scour of the riverbed’s geological layer and therefore the topsoil layer of the riverbed is always in a state of motion, but the river is not deeply eroded because there is a balance of alluvium along the river. Thus, the flow rate under the bridge is greater than the allowable rate without erosion, which is not the cause of scour in the mainstream and the deformation of the river under the bridge can only be explained by the imbalance of alluvium along the river. The overall scour under the bridge is calculated according to the principle of balance of sediment limit for the mainstream and the flow part with alluvium transport of O.V.Andreev (1955) [7]. The flow depth after scouring is determined according to equation (1) .

Where:

+ Q1=Qch, Q2=Q'ch: Water flow before and after bridge construction at the mainstream.

+ hch, h'ch : Water depth at mainstream before (natural time) and after scouring.

hch = ▼hhm – ▼htbs

▼hhm: Elevation of flow rate at natural time (taken according to design frequency)

▼htbs: average elevation of the riverbed

+ Bch, B'ch: Mainstream width before and after bridge construction.

Bch = L0 = 1657.34m.

B'ch = L = 1401.5 m.

Calculation results of general scour depth according to table 1 Table 1. Table of results for calculating the general scour depth of piers located on the main stream according to the 1D average velocity method.

Bridge Piers

Bottom elevation

(m)

Surface elevation

(m)

Water Depth before scour

hch

(m)

Water Depth after scour

h'ch

(m)

Rising water

(m)

General depth scour (m)

Bottom elevation after local scour (m)

T3

-0.500

2.830

3.330

3.504

0.061

0.235

-0.735

T4

-1.250

2.830

4.080

4.293

0.061

0.274

-1.524

T5

-1.240

2.830

4.070

4.283

0.061

0.274

-1.514

T6

-1.210

2.830

4.040

4.251

0.061

0.272

-1.482

T7

-0.960

2.830

3.790

3.988

0.061

0.259

-1.219

T8

-1.420

2.830

4.250

4.472

0.061

0.283

-1.703

T9

-1.720

2.830

4.550

4.788

0.061

0.299

-2.019

T10

-1.900

2.830

4.730

4.977

0.061

0.308

-2.208

T11

-2.050

2.830

4.880

5.135

0.061

0.316

-2.366

T12

-2.540

2.830

5.370

5.651

0.061

0.342

-2.882

T13

-2.630

2.830

5.460

5.745

0.061

0.346

-2.976

T14

-3.400

2.830

6.230

6.556

0.061

0.387

-3.787

T15

-8.150

2.830

10.980

11.554

0.061

0.635

-8.785

T16

-11.600

2.830

14.430

15.184

0.061

0.815

-12.415

T17

1.260

2.830

1.570

1.652

0.061

0.143

1.117

T18

0.000

2.830

2.830

2.978

0.061

0.209

-0.209

T19

-0.050

2.830

2.880

3.031

0.061

0.212

-0.262

T20

0.040

2.830

2.790

2.936

0.061

0.207

-0.167

T21

-0.040

2.830

2.870

3.020

0.061

0.211

-0.251

Caculating local Scour (p = 1%)

Two authors N.X Truc and N.H. Khai (1982) [8] introduced the formula for determining the largest local scour value at the bridge pier. Based on the research results on the causes and development process of local scour on pier scour models in the hydraulic laboratory and the research results of foreign authors, a reasonable structural form of the local scour calculation formula has been selected. The formula (2) has the following simple form. When v³ vox (for mainstream piers). 

hcb= 0,52.kd.b0,88.h0,12.(V/Vox)1,16                                                                                  (2)

Where:

+ hcb: maximum local scour depth at bridge pier, m 

+ kd: factor taking into account the influence of cylinder shape, taken as  0,1kζ

+ kζ : Iaratslaxev's shape coefficient    

+ h: depth of water flow at bridge pier before local scour, m 

+ V: water velocity at bridge pier before local scour, m/s

+ Vox  : allowable no- scour velocity of the soil layer at the location where scour development  

+ b: calculated width of the cylinder, m

The results of local scour calculation are obtained from Table 2

Table 2. Table of results of calculation of local scour depth of piers located on the main stream according to the average 1D velocity method.

Bridge Piers

Shape factor

Kd

Width of pier

b (m)

Depth of water flow

h (m)

Velocity

V (m/s)

No-scour velocity Vox (m/s)

Ratio

V/Vox

Maximum local scour depth

hcb (m)

T3

0.97

1.8

3.565

1.484

0.720

2.061

2.280

T4

0.97

1.8

4.354

1.484

0.790

1.878

2.097

T5

0.97

1.8

4.344

1.484

0.780

1.903

2.128

T6

0.97

1.8

4.312

1.484

0.770

1.927

2.158

T7

0.97

1.8

4.049

1.484

0.740

2.005

2.243

T8

0.97

1.8

4.533

1.484

0.805

1.843

2.062

T9

0.97

1.8

4.849

1.484

0.815

1.821

2.049

T10

0.97

1.8

5.038

1.484

0.820

1.810

2.044

T11

0.97

2

5.196

1.484

0.825

1.799

2.235

T12

0.97

4

5.712

1.484

0.835

1.777

4.103

T13

0.97

5

5.806

1.484

0.840

1.767

4.969

T14

0.97

5

6.617

1.484

0.860

1.726

4.911

T15

0.97

5

11.615

1.484

0.910

1.631

4.921

T16

0.97

5

15.245

1.484

0.950

1.562

4.837

T17

0.97

4

1.713

1.484

0.650

2.283

4.748

T18

0.97

2

3.039

1.484

0.705

2.105

2.515

T19

0.97

1.8

3.092

1.484

0.705

2.105

2.297

T20

0.97

1.8

2.997

1.484

0.690

2.151

2.346

T21

0.97

1.8

3.081

1.484

0.700

2.120

2.315

3 Bibliography

4 Acknowledgments

5 References

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Document information

Published on 24/11/23
Accepted on 30/10/23
Submitted on 31/07/23

Volume 39, Issue 4, 2023
DOI: 10.23967/j.rimni.2023.10.009
Licence: CC BY-NC-SA license

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