| Summary: | 碩士 === 國立中央大學 === 土木工程研究所 === 90 ===
This study uses experimental mobile channel to examine the characteristics of local scour around non-uniform piers and the piers with collar protection. The maximum scour depth and the range of the scour hole is analyzed. Furthermore, the change of scour at different exposure elevations is compared by performing a series of case studies.
When the collar is close to the bed, the scour depth decreases. When it’s top is flush with the bed, the scour depth decreases obviously, and both the downflow and horseshoe vortex are guided to the downstream successfully far away from the bridge pier structure. The scour depth doesn’t change obviously with the increase of the location of the collar, so the horseshoe vortex is the main factor for scouring. The experiments of non-uniform piers at different exposure elevations showed that the increase of exposure elevation causes the increase of obstruction area. So, the range of scour hole and the depth of scour will increase. When the top of the pier foundation is flush with the bed, the scour doesn’t occur in front of the pier foundation, the result is similar to that for using collar. While the scour depth is much deeper for those causes when the scour occurs in front of the pier.
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