Abstract
In the wide area of the eastern part of Tokyo, the ground level is less than mean sea level. This area is more vulnerable to disasters than other areas. If large flood damage such as storm surge should occur in this area, the disaster would be a long-term catastrophe. On the coast of Tokyo Bay, countermeasures have been taken by tide embankments and floodgates. However, considering the damage scale when it occurs, an analysis in this area is very important. In this area, ground settlement occurred and groundwater head dropped because groundwater excessively withdrew by the industrial purpose during the period of economic growth. Currently, the groundwater head recovers and the ground settlement has been subsided. However, due to the groundwater head fluctuation, pore water pressure distribution had been different from hydrostatic pressure distribution. Therefore, in the analysis in this area, it is necessary to consider past groundwater head fluctuation. In this research, the ground settlement and the distribution of pore water pressure are simulated from groundwater level fluctuation over the past 100 years. Then, we conducted the seismic analysis by input the distribution of effective stress calculating from the simulated ground water pressure. The sites analyzed in this research are Tokyo Sea Life Park at the mouth of Arakawa River.
Highlights
In the Kanto region, the Tokyo Inland Earthquake is concerned
In the case of actual grounds, once the ground settlement occurred by the lowering of the groundwater level, the settlement didn’t recover even after the groundwater level recovers
We conducted consolidation analysis with groundwater level fluctuation and dynamic response analyses considering the influence of groundwater level fluctuation
Summary
In the Kanto region, the Tokyo Inland Earthquake is concerned. It is said that the Tokyo Inland Earthquake will occur with a probability of 70% within the 30 years. In the eastern part of Tokyo, the zero-meter area where the ground height is lower than the sea level is widely distributed. Suppose that a large earthquake such as Tokyo Inland Earthquake causes to fail the function of the tide equipment such as a water gate and embankment, and it will suffer the storm surge before the repair is over. An earthquake response analysis is performed on the eastern lowland of Tokyo, where there is a risk of serious damage when a large-scale earthquake occurs. In order to analyze Tokyo zero-meter area, it is necessary to conduct earthquake response analysis considering the groundwater level change. Matsumoto et al.[2] have analyzed the Tokyo Sea Life Park in the vicinity of Arakawa estuary and simulated the distribution of pore water pressure by considering the groundwater pumping. In order to calculate the distribution of effective stress to input to the earthquake response analysis, the same method as Matsumoto et al is applied in this research
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