To prevent ground liquefaction and lateral flow in the event of an earthquake by encircling ground around a structure with an enclosure wall, filling the gap between the structure and the top portion of the enclosure wall with a solidification material, thereby restraining the ground immediately under the structure and preventing the ground surrounded with the enclosure wall from shearing deformation and volumetric change.

An enclosure wall 12 is constructed around the foot of an existing structure 10 supported with a plurality of foundation piles 11 by means of continuous underground wall method or the like. The enclosure wall 12 penetrates a possible liquefaction layer (b) into a non-liquefaction layer (c) to divide the liquefaction layer (b) into inside and outside of the enclosure wall 12. The upper portion of the structure 10 and the upper portion of the enclosure wall 12 are united together by pouring cement-based solidification material 13 such as expanded mortar to the interior of the enclosure wall 12 surrounding the ground portion of the structure 10. The ground in the area E just below the structure 10 to be treated with anti-liquefaction measures is isolated from the surrounding liquefaction layer (b) by the enclosure wall 12, the solidification material 13, and a non-liquefaction layer C closing the lower opening of the enclosure wall 12, and prevented from shearing deformation and volumetric change.