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8 CHAPTER 3 Data Acquisition and Analyses Details of the data acquisition and the quality control not known (Zhuravlyov 1978). Another important parameter procedures used to identify the final data sets are presented that is usually missing in field data is the level of maturity of in this chapter. As stated earlier, assessing the accuracy of the scour hole at the time of measurement. Therefore, the the scour evolution data required introducing assumptions potential errors associated with field data must be considered about the maturity of the scour holes at the end of the tests. when verifying predictive equations. Therefore, this data was used as published. Only field data for The available laboratory and field equilibrium scour data piers of simple shape (round, square, rectangular, etc.) were are presented in matrix plots in Figures 1 through 4. Each included in the field data set. of the independent parameters are plotted versus the other independent parameters, for example, a or a* versus V1; y1 versus D50; V1 versus y1, a, D50; etc. The matrix plots are also Equilibrium Local Scour Data given in dimensionless form in terms of the ratios a/y1, V1/Vc and a/D50. The histograms in the matrices provide an easy way Relatively large quantities of equilibrium local scour data to illustrate the distribution of existing data and thus where have been published (943 field and 569 laboratory data points). data gaps exist. Figures 1 through 4 provide a qualitative The sources and quantities of these data are listed in Table 2; view of the range and distribution of the variables covered in however, it includes only data where all the relevant parameters the laboratory and field data sets compiled in this study. The are known and the sediment is cohesionless. Only 15 field data information in the matrices can be interpreted as follows. In points were excluded due to missing information. Figure 1 the top row in the matrix has four elements. Starting Laboratory data are derived from experiments that were from the left, the first element is a histogram showing the carefully performed with all pertinent parameters (flow distribution of laboratory data with water depth. The vast speed and direction relative to the pier, sediment size and majority of the data is for water depths less than 1 ft with only size distribution, scour depths, etc.) given. There are, how- a small number of tests conducted at depths beyond 2 ft. The ever, potential scale effects when the laboratory results are second element shows the values of water depth and pier size used for prototype piers. Flow regimes are usually different covered by the data. The 3 ft diameter pier tests were performed between model and prototype resulting in differences in the at water depths ranging from about 1 ft up to 6 ft. There is relative magnitudes of the forces involved. This is particularly a data gap for pier diameters between 1 and 3 ft. The third true for such complex mechanisms as sediment transport element in the top row shows the values of water depth and and scour. flow velocity for the laboratory data. All of the high-velocity Field studies have the advantage of little or no scale effects (greater than 2 ft/s) tests were performed with water depths provided the structure size is approximately the size of interest. less than or equal to 2 ft. The fourth element shows the However, the measurement accuracy for both independent values of water depth and sediment size. The horizontal axis (flow velocity and duration, sediment properties, etc.) and is logarithmic so the value of -0.5 corresponds to a sediment dependent (contraction and local scour depths) quantities is, diameter of 0.32 mm, 0.5 to a diameter of 3.2 mm, etc. The in general, less than that for laboratory conditions. This is sediment diameters range from 0.1 to 7.0 mm, but only a few especially true for high-velocity flows where there is signifi- tests were conducted at water depths greater than 2 ft. The cant suspended sediment in the water column. In some of the other elements in Figures 1 through 4 can be interpreted in reported cases, the substructure shape and dimensions were this manner.