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From page 30... ... , two sets of correction factors had to be developed. The correction factors for the maximum scour depth were developed on the basis of flume tests; the correction factors for the initial maximum shear stress were developed on the basis of numerical simulations. Read the entire page →
From page 31... ... Attack Angle Effect Figure 5.1. Parameter definition for complex pier scour. Read the entire page →
From page 32... ... Pier models used in the complex pier scour tests. Figure 5.4. Read the entire page →
From page 33... ... This requirement was particularly important for the contraction scour tests. 5.6 FLUME TESTS: PROCEDURE AND MEASUREMENT Complex pier scour tests were conducted in the 1.5-m-wide flume and all of the tests were done according to the following procedure: 1. Read the entire page →
From page 34... ... Gudavalli's flume tests indicate that in cohesive soils the flow depth has no clear influence on the scour depth when H/B≥1.6 where H is the water depth and B the pier diameter. In this study, a series of pier scour tests with water depths ranging from H/B = 0.2 to H/B = 2.5 were conducted. Read the entire page →
From page 35... ... Influence of shallow water depth on maximum pier scour depth. Read the entire page →
From page 36... ... . Since the initial scour rate is directly tied to the initial shear stress through the erosion function, it can be stated that the initial shear stress increases when the water depth decreases and decreases when the pier diameter increases. Read the entire page →
From page 37... ... The maximum scour depth may happen either around the pier or at some intermediate location; its location was determined with the point gage system. 5.11 PIER SPACING EFFECT ON MAXIMUM SCOUR DEPTH The pier spacing effect on the maximum pier scour depth can be incorporated in the general equation by using a correction factor, Ksp, equal to the ratio of the maximum scour depth of the line of piers over the maximum scour depth of the isolated pier. Read the entire page →
From page 38... ... It shows that the initial scour rate tends to increase as the piers become more closely spaced. In summary, both the maximum pier scour depth and the initial scour rate will increase as the piers become more closely spaced. Read the entire page →
From page 39... ... Again, the maximum scour depth and the initial scour rate were calculated in the same way as in the case of the other flume tests. The scour depth development curves are plotted in Figure 5.18. Read the entire page →
From page 40... ... The maximum scour depth and initial scour rate were obtained in the same way as previously, by using the hyperbola model. 5.18 ATTACK ANGLE EFFECT ON MAXIMUM SCOUR DEPTH The correction factor Ka, used to account for the attack angle effect on maximum pier scour depth, is calculated as the ratio of the maximum scour depth for a given pier and a given attack angle over the maximum scour depth for the same pier and an attack angle equal to zero (reference case) Read the entire page →
From page 41... ... 1.0 2.0 3.0 4.0 5.0 6.0 7.0 0 4 8 12 L/B Ka Mostafa, n=0.8 Laursen, n=0.68 Richardson, n=0.65 SRICOS, n=0.635 Ka' Ka Figure 5.25. Attack angle effect on maximum scour depth. Read the entire page →
From page 42... ... In order to examine the pure attack angle effect, the shallow water effect and pier spacing effect need to be eliminated. The proposed equations for shallow water depth and pier spacing are used to isolate the angle of attack effect. Read the entire page →
From page 43... ... . 5.21 MAXIMUM SCOUR DEPTH EQUATION FOR COMPLEX PIER SCOUR In the previous sections, individual effects on the maximum pier scour depth were studied by flume testing. Read the entire page →
From page 44... ... C (mm) 61 244 375 45 330 500 61 244 375 15 330 500 Attack Angle Effect Pier width Pier length Water depth Attack angle Mean approaching velocity Center to center pier spacing B' (mm) Read the entire page →

From page 30...

... , two sets of correction factors had to be developed. The correction factors for the maximum scour depth were developed on the basis of flume tests; the correction factors for the initial maximum shear stress were developed on the basis of numerical simulations.