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Analytical Exploration of Damage to Piles-structure System Caused by Liquefied Ground Motion near Quay Wall

by Masaki Fuchimoto, Akira Ohtsuki and Kiyoshi Fukutake

The January 17, 1995 Hyogo-ken Nambu Earthquake strongly shook the Hanshin districts along the coastline. The soil liquefaction caused serious damage to storehouses and buildings as well as other structures such as caisson-type quay walls and freeway bridges. The object of this study is to explore the reasons resulting in the failure of pile by which a structure is supported in the soft reclaimed ground. Based on results of observation on site, at first, the numerical analysis of non-linear earthquake responses has been performed to examine the dynamic behavior of the soil-pile-structure system during the shaking. Then, the permanent ground displacements due to post-liquefaction have been estimated, and the safety of the pile foundation against the earthquake has been assessed. Finally the failure of a caisson-type quay wall and the deformation behavior of its surrounding ground have been analyzed. The following main conclusions have been drawn from the analytical results.

1. The pile are likely to be damaged at their tips and middle parts;
2. The failure of the piles at their middle parts is considered to be attributed to liquefied surrounding soil;
3. The failure of the piles at their tips may occur by the permanent ground displacement due to post-liquefaction;
4. The cause of the large movement of the caisson-type quay walls towards sea seems to depend mainly on the large amplitude of inertia force and the earth pressure induced by the earthquake.