1. Study of Field Experiment on Prevention of Bridge-Pier Scouring by Using A Stack of Rings with Soft Blades * Ta-Hsiung Peng Yu-Chao HsuChyan-Deng Jan* 701 1 n8896103@mail.ncku.edu.tw 2008 3 2008 2009 8 AbstractFlow vortexes are generated at the surrounding area of a bridge pier when water passes it. This phenomenon could cause severe erosion at the bottom of a pier and therefore, it is a threat to stability of the pier especially during flood events. This research is aimed to develop a soft device that could effectively eliminate or reduce the vortex phenomenon, and then reduce the bed erosion, so as to protect bridge pier. Field investigation of the present research was conducted at the prier #5 of Tsengwen-River Bridge No. 2. The soft device was made of used tires of motor vehicles, attached with soft metal blades/fins one tires surface. This device is also named as a stack of rings with soft blades. The soft devices were tightly installed around the bride pier. The flow patterns around the bridge1 2. pier at flood events were observed, and the variations of river bed around the pier were also observed to check the effectiveness the proposed soft device. The results show that the soft device could effectively reduce the vortex intensity around piers, so as to reduce erosion ability and let some sediments deposit around the bridge pier. The proposed device has been proved having the function of protecting bridge pier against scouring. And the device also passed the serious test of huge flood of Morakot typhoon in the 2009.KeywordsA stack of rings with soft blades, Bridge pier, Bridge pier protection 1.1 1 (Ettema, 1980;Raudkivi, 1986;, 1995;, 2002 , 2006) (, 2006 , 2007) 2 3. (1) (2) (3) (a) (b) Chiew and Lim (2000) Unger and Hager(2006) Yoon(2005) 1.2 (P5) (1) 3 4. (2) (3) (4) 1. 2 2. 3. 4. 5. 6. 4 5. 36cm 24cm U 1 2 -10cm 2 (, 2007) U 3 4.1 (, 2007 , 2007) 3 4 4 5 P5 5 6. () 6 100 P5 7 ( 8) 9 4.2 2008 3 2008 7 8 9 2009 8 2008 7 9 2008 2009 4.2.1 (Kalmaegi) 2008 17 21 18 7 6 7. 957mm 944mm 900mm ( 5) 10 7 19 ( 11)P5 P4 P5 ( 12) 7 24 ( 13) ( 14) 15 7 8. 16 2008 8 30 17 4.2.2 (Sinlaku) 2008 9 14 3 1,000mm 32 1,602mm 1,466mm( 6) 18 2008 9 14 19 2008 8 4.2.3 2008 9 28 15 29 4 994mm 632mm 602mm ( 7) 8 9. 20 21 4.2.4 2008 12 P5 2008 2008 12 9 P5 22 23 P4 P5 P6 P5 P5 P5 23 24 P4 25 26 P5 4.2.5 2009 8 7 23 8 8 14 8 6 11 2000mm 1000mm 20 2900mm 2500mm 8 8 pm08:30 11000 350 9 8277 13 8 9 10. 27 28 29 P5 30 P6 31 P5 5.1 1. U 10 11. 2. 3. 4. P4P5 P6 P5 5. 5.2 1. 2. 11 12. 96-2622-E-006-041-CC3 1. 2002 2. 20083. 2007 4. 20075. 2006 32 8 39 44 6. 20077. 1995(I) 16 21 8. Chiew, Y.M., and Lim, F.H., 2000, Failure Behavior of Riprap Layer at Bridge PiersUnder Live-Bed Conditions. Journal of Hydraulic Engineering, ASCE, Vol. 126(1), pp.43-55.9. Ettema, R., 1980, Scour at Bridge Piers. School of Engineering Report No.216,Department of Civil Engineering, University of Auckland, Auckland, New Zealand.10. Raudkivi, A.J., 1986, Functional Trends of Scour at Bridge Piers. Journal ofHydraulic Engineering, ASCE, Vol. 112(1), pp. 1-13. 12 13. 11. Unger J. and Hager W.H., 2006, Riprap Failure at Circular Bridge Pier. Journal ofHydraulic Engineering, ASCE, Vol. 132(4), pp. 354-362.12. Yoon, T.H. 2005, Wire Gabion for Protecting Bridge Pier. Journal of HydraulicEngineering, ASCE, Vol. 131(11), pp. 942-949. 1 (Ettema, 1980) (a) (b) 2 13 14. 1 2 3 3 14 15. (a) (b) 4 P5 4 5 P5 15 16. 6 7 8 9 16 17. 16,000 015,000 1014,000 13,000 2012,00011,000 3010,000 40(CMS) 9,000 8,000 50 7,000 60 6,000 5,000 70 4,000 3,000 80 2,000 90 1,000 0 100 800 00817 1819 20 2177 777 5 10 (2008 7 18 ) 11 P5 (2008 7 19 ) 12 (2008 7 19 ) 17 18. 13 (2008 7 24 ) 14 (2008 8 17 ) 15 16 18 19. 17 (Aug. 30, 2008) 6 18 (Sep. 14, 2008) 19 P5 (Sep. 16, 2008) 19 20. 7 20 P5 (Oct. 1, 2008) 21 (Oct. 5, 2008) 22 P5 P6 (March 31, 2008)20 21. 23 P5()(Dec. 9, 2008) 24 P5 (Dec. 9, 2008) 25 P4 (Dec. 9, 2008) 26 P4 P5 (Dec. 9, 2008)21 22. 8 27 (Aug. 9, 2009) 28 P5 (Aug. 13, 2009) 29 (Aug. 13, 2009) 22 23. 30 P5 (Aug. 26, 2009 ) 31 P6 ()(Aug. 26, 2009) 23