Seismic Analyses for Caisson-type Wharf Structures

• Main Authors: Tzu-Ying Li, 李姿穎
• Other Authors: 陳正興
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/68860282918506302146

碩士 === 國立臺灣大學 === 土木工程學研究所 === 97 === In 1986, Suao Harbor suffered disasters of Hualien earthquake which caused it damage ; in 1999, Taichung Harbor suffered disasters of 921 earthquake that caused it damage, too. The FEM program─PLAXIS is the main analysis tool in this study including effective stress dynamic analysis. This study chooses three representative cases: Taichung Harbor #1 and #4A gravity-type caisson wharf (liquefaction to silding failure), Suao Harbor #4 gravity-type caisson wharf (silding failure) and Hualien #19~21 gravity-type caisson wharf(no silding failure). For studying seismic behavior of gravity-type caisson wharf and backfilled zones, three cases use PLAXIS to proceed numerical analysis, and compare numerical results with field reports and numerical analyses by other researchers. The numerical simulation results of this study show that the failure mechanism of both two cases─Taichung Harbor #1 and #4A caisson wharfs are due to the loss of shear strength of backfilled zones during earthquake. So backfilled zones produce large lateral force acting on the caisson, leading to its lateral sliding, rotation and settlement, the same as that found in literature. .The excess pore pressure at locations far away from the caisson rises up higher than that near the caisson when #1 and #4A caisson wharf suffered Chi-Chi earthquake. The effective stress of soil just behind the caisson does not reach zero during shaking, but further portion of the backfill reaches closer zero. In 1986, during Hualien earthquake, there was sliding displacement in Suao Harbor #4 caisson wharf. Although the acceleration amplitude of Hualien earthquake was larger than 921 earthquake, the geological survey of the disaster found that # 4 caisson wharf was no liquefaction at backfilled zones, only a slight sliding displacement.Therefore, the result of the numerical analysis is similar to field reports. In addition, Hualien Harbor #19~21 caisson wharf had no failure during 921 Chi-Chi earthquake, and the result of the numerical analysis shows that there is nearly no sliding displacement. So, this result is the same as field reports.