| Summary: | 碩士 === 逢甲大學 === 水利工程與資源保育研究所 === 98 === In this study, the use of cylinder of rings as a pier scour countermeasure is reported. The cylinder of rings consisting of cylindrical rubber rings are placed upstream of a bridge pier to reduce the flow impacting energy and scour by their irregular surface roughness and porous characteristics. Furthermore, the FLOW-3D model was used to simulate the flow field around a bridge pier, and to investigate the difference in the protection effect of pier foundation before and after the installation of cylinder of rings protection works. The main purpose of this study is to search for the optimum arrangements of the cylinder of rings protection works to solve bridge failure problems.
The results showed that certain degrees of protection were obtained with any type of cylinder of rings protection works installing upstream of the pier. When the diameter of the ring column is equal to the pier diameter, the flow through the cylinder of rings does not impact the front edge of the pier, and the best protective efficiency can be obtained. In addition, if the height of the ring column is lower than the water surface, the energy of the vertical velocity will be increased when the flow passes over the cylinder of rings and induces a downflow. The submerged type of protection work provides lower protective efficiency than the case that the cylinders of rings are unsubmerged. The latter gives anticipated scour protection results.
The flow velocity in front of pier increases with an increase of the distance between the cylinder of rings and pier, but the velocities besides the pier have little variation. In addition, the sour influencing area increases with an increase of the distance between the cylinder of rings and pier. The best arrangement of this research is that the diameter of ring column equals to the diameter of the pier, the height of the ring column exceeds the flow depth, and the distance between the cylinder of rings and pier equals to the pier diameter, which reduces the downflow velocity for 89%, i.e. reduces from -10.2 cm/s to -1.1 cm/s, and the velocities of both sides of the piers reduce about 31%.
|
|---|
