2010 年 59 巻 1 号 p. 84-88
Containment with soil-bentonite (SB) cutoff walls has been proved to be a valid method to prevent the contaminants in subsurface from migrating in the aquifer. Previous researches by the authors concluded that SB was able to maintain its hydraulic barrier performance even when exposed to various types and concentrations of chemicals (calcium chloride, heavy fuel oil, ethanol, and/or seawater) in the permeant and/or in the pore water of original soil, if a certain degree of bentonite hydration was expected to occur by the first wetting liquid. However, SB is a rather flexible material compared with other typical barrier materials. Thus, static/dynamic stability is another important issue. In this study, centrifuge model tests were performed to evaluate the seismic performance of the vertical SB cutoff wall, which is usually installed in a permeable aquifer with liquefaction potential during the earthquake. In addition, the deformation property of the SB against dynamic loading was examined by conducting the conventional cyclic triaxial test. SB maintained its elasticity until the axial strain reached 1%, and then the SB was subjected to large plastic deformation (5% in axial strain) against the cyclic loading. In centrifuge model tests, although vertical settlement of the SB cutoff wall in liquefied ground reached 300 to 400mm in prototype scale even against the earthquake with only 200gal in acceleration but relatively longer duration, its integrity was maintained for a range of earthquake motion applied in this study (max. 500gal in acceleration or 60second in duration).