The Tohoku Earthquake caused widespread geotechnical damage in the towns of Fusa and Katori, two towns situated immediately north of Tokyo. The damage to structures and foundations in these towns was mainly the result of ground liquefaction, and surprising since they are located at an epicentral distance of about 300 km. The authors investigated the performance of foundations and liquefaction-induced damage during a post-earthquake engineering field reconnaissance in April 2011. In areas where the ground liquefied, they observed that structures constructed on deep foundations generally behaved very well, as opposed to those constructed on shallow foundations, which settled and tilted considerably. The performance of small residential and commercial buildings supported by deep foundations consisting of closely spaced small diameter piles that extended below the liquefied layer was also excellent. Numerical modeling shows that the flexibility of small diameter piles, such as the ones typically used in Japan, makes deep foundations particular resilient when liquefaction occurs in laterally confined areas.
Subjects: driven piles, drilled shafts, earthquake, seismic performance, soil liquefaction
Author: Daniel Pradel, PE GE DGE, Joseph Wartman, Prof. and Binod Tiwari, Prof.
Publisher: DFI, EFFC