Case Study on Countermeasure to Liquefaction by Dewatering Method
Seiji SUWA and Mitsuharu FUKUDA
Abstract:There are some counter measurements developed for sustaining liquefaction damage. Though the method is theoretically clear, only few example of application. In 1995, Hyogo Nanbu earthquake triggered the liquefaction in the urban and coastal area around Osaka bay containing Tsukiji area. Liquefaction caused many houses tilted, settled and collapsed around the lowland and reclaimed area. In this paper, some damaged structures caused by the liquefaction are introduced. It focuses Tsukiji area, which is about 12km far from the active fault line describing geological profile and ground water environment. Tsukiji area is where the dewatering method was applied as the counter measurement. Land subsidence was caused by pumping groundwater and it caused the leakage from the surrounding sea which has been a concern for local overnment. This paper shows how to decrease the groundwater level in the area by working from the design concept on installing the permeable pipe in the netlike based upon the site pumping test. As the result, 3m of non liquefaction layer over the groundwater was secured. Key Words:Hyogo Nanbu earthquake, Tsukiji area, Dewatering method, Liquefaction, Groundwater