PURPOSE: To produce a treated soil usable as a filling material, a back filling material, a refilling material or an invert material by mixing soil produced from e.g. a shield driving work with a specified hardener, additives and water.

CONSTITUTION: This method comprises mixing soil produced from e.g. a shield driving work with a hardener such as cement or lime and water and adding an additive based on an acrylic acid salt or a polyacrylic acid salt or a derivative thereof to the mixture to form a treated soil and using the treated soil as a filling material, a back filling material or an invert material. It is desirable that the treated soil is pumped to a desired place. It is desirable that the produced soil is mixed with an additive such as an acrylic acid salt and water, and the hardener such as cement or lime is added to the mixture.