Abstract
The 2011 Great East Japan Earthquake caused liquefaction in many places in the Kanto and Tohoku regions. In residential areas where liquefaction occurred, the ground in the whole area, including lifelines and roads, must be treated by special measures to prevent re-liquefaction. The Ministry of Land, Infrastructure, Transport and Tourism established a new project “Urban liquefaction countermeasure project” after the earthquake. Among several countermeasures, lowering the ground water table has been selected as the most promising in several cities in Kanto region. Several studies on the effect of the lowering the groundwater table were conducted in this paper. Case histories on previous earthquakes showed the critical water table to cause liquefaction-induced damage to wooden houses is around GL-2m. Similar results were obtained by residual deformation analyses. Then it was concluded that lowering the ground water table at the depth of about GL-3m must be enough to mitigate liquefaction-induced damage to wooden houses
