Study on liquefaction countermeasures for existing road bridge pile foundations in volcanic ash ground
Study on liquefaction countermeasures for existing road bridge pile foundations in volcanic ash ground
Some pile foundations in older road bridges do not meet current seismic design standards. While certain piles require structural reinforcement, others can be improved by simply preventing liquefaction in the surrounding ground. This also applies to volcanic coarse-grained soils, which are widely distributed in areas like Hokkaido and Kyushu and are treated as special soil types in Japan.
This study examined the applicability of a seismic reinforcement methodused when pile foundation stability is compromised solely due to liquefaction of volcanic ash groundthrough centrifuge model tests. The method involves enclosing the ground around the pile foundation using a Grid-form ground improvement wall, installed without contact with existing structures. In the tests, three types of pile foundations that were widely used in Hokkaido before the introduction of current seismic design standards were selected to evaluate how the distance from the outermost pile to the wall and the strength of the improved ground affect liquefaction resistance and pile behavior.
The results showed that a maximum grid spacing of 7.0 meters and a minimum clearance of 2.0 meters from the pile center effectively suppress the reduction in the coefficient of horizontal subgrade reaction of pile, while avoiding adverse effects on the overall seismic design of the bridge.
T. Egawa; Masahiko Yamaki; Koichi Isobe
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Session 6: Onshore and offshore foundation systems
https://doi.org/10.53243/ICPMG2026-119