In the field of earthquake geotechnical engineering, mitigation of damage caused by liquefaction has been one of the most important targets of study. Conventionally, effort has been focused on prevention of liquefaction by employing such measures as densification. However, lifeline industries and river-dike engineering have been aware recently that such measures are impractical from economic viewpoints. In this context, this paper discusses the use of embedded sheet-pile wall which can mitigate the magnitude of lateral displacement of liquefied ground. Shaking table tests revealed the mitigative effects of a wall. Study was then extended to develop an analytical method which can assess the displacement reduced by a wall. Example calculation on a recent event during the 1995 Kobe earthquake matches with the observation.
Many attempts have been made in the past decades to develop measures which can prevent subsoil liquefaction during strong earthquakes. Those measures consist of densification of sand, grouting, drainage, and pumping of ground water among others. All of them aimed at protecting specified facilities from liquefaction hazards by reducing the development of excess pore water pressure and consequently preventing onset of liquefaction. In contrast, there is a situation in which mitigation of liquefaction-induced damage is needed in a larger area. Examples can be taken in seismic resistance of embedded lifelines as well as river dikes of a long length. The present study is concerned with installation of subsurface sheet-pile walls which mitigate lateral flow displacement of liquefied ground. It consists of two phases of study which are namely shaking-table model tests to demonstrate the mitigative effects of subsurface walls and development of analytical method which can assess the extent of mitigated displacement. A special attention is focused on not requiring detailed subsoil investigation for practical calculation of ground displacement.
