Abstract
In light of the disastrous the 2011 Tohoku Pacific Earthquake, the government of Japan has conducted studies to revise the seismic design code, and elevated peak ground accelerations have been adopted. Consequently, revisions on existing design to comply with the updated code are required for public projects that are still undergoing. The design safety needs to be reassessed, and implementation of strengthening measures is required if deemed necessary. For liquefaction countermeasures, ground treatment techniques that could increase the density of soils are often the preferable alternatives. The treatment usually increases the in situ SPT-N or CPT-qc values, which in turn would increase the resistance of soil against liquefaction. For many public infrastructures in Japan supported by bored piles embedded partly or entirely in sandy soils, reevaluation of design safety against soil liquefaction would be required. In an assessment of possible retrofitting countermeasures for an infrastructure foundation, ground treatment has been considered. In this case study, effect of ground treatment on response of piles in liquefiable soils was investigated with numerical analyses using FLAC. Results provide insights into this ground treatment effect and useful information for consideration in future design or decision making.
Highlights
The 2011 Great East Japan Earthquake, with a magnitude of Mw=9.0, occurred in the Pacific Ocean about 130 km off the northeast coast of Japan’s main island on March 11, 2011
This paper presents a potential to approach determine and evaluate the range of ground treatment in practice and the verification of the effectiveness of ground treatment with the behavior of the pile foundation
The following statements can be concluded from the analysis results stated above: 1) When soils were liquefied, the displacement vectors of soils around the pile group exhibited downward movement (Fig.7), which was in agreement with liquefaction phenomenon in practice, where the ground settlements were observed in liquefied soils
Summary
The 2011 Great East Japan Earthquake, with a magnitude of Mw=9.0, occurred in the Pacific Ocean about 130 km off the northeast coast of Japan’s main island on March 11, 2011. The quake was followed by a huge tsunami that destroyed many cities and killed and injured many people along the Pacific Coast. The tsunami broke the emergency cooling system of a nuclear power plant in Fukushima Prefecture, and large areas of Japan have been plagued by radiation and a shortage of electricity ever since. Many houses and lifelines were damaged by soil liquefaction, landslides occurred, dams failed and river dikes settled in the Tohoku district of northeastern Japan, and in the Kanto district, which surrounds Tokyo. Liquefaction occurred over a wide area of reclaimed lands along Tokyo Bay, the epicentral distance was very large, about 380–400 km
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