As a liquefaction countermeasure technique, lattice-type deep-mixing method restrains shear deformations of the ground induced by earthquakes and therefore is effective in controlling the generation of excess pore water pressure. In a full-scale liquefaction experiment, ground improvement by lattice-type deep mixing method was implemented in Ishikari Bay New Port where the lattice was formed by X-jet (cross jet) method which is a high-pressure jet-type deep mixing method. The effectiveness of the method as liquefaction countermeasure was confirmed from the excess pore water pressure that was generated by blast-induced shaking and the workability of the method was examined. This report focused on the data acquired from the field test, such as the excess pore water pressure generated during the earthquake, and the controlling effect on the post-earthquake subsidence at the site. Moreover, FEM analysis and simplified analysis were conducted to reproduce the above behavior. As the result of this study, it is confirmed that the lattice-type deep-mixing method using X-jet method is very effective as a liquefaction countermeasure technique.
