| Summary: | 碩士 === 國立中央大學 === 土木工程研究所 === 87 === The analysis and discussion of local scour are studying in the cylindrical bridge piers which with nonwoven gabions protection and no protection. The flume that is a mobile experimental water tank: 800cm long, 120cm wide and 20cm depth in sand. The flow condition in flume that control in subcritical flow. ( Fr < 1 ) The characteristic of cylindrical bridge pier is 55cm long, 6cm and 7.6cm diameter, respectively. The gabions were made of nonwoven, and surround the bridge piers. There are three major factors can make bridge piers protection efficiency changed: the difference in the top elevation of the foundation and stream bed, Z; pier diameter, ap; and foundation diameter, af. According the result, it can reduce the scour depth indeed if bridge piers with gabions protection. And it better put proection under base 1cm. The bridge piers with 6cm and 7.6cm diameter can reduce scour depth abount 67% and 71%, respectively. It also makes the range of scour hole smaller, the slope of center profile changes a little and the deepest local scoue depth is far away from bridge pier. There is no protection when gabions layup 10cm from based, and makes the deeper scour depth.
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