Aiming mainly to develop a liquefaction countermeasure method for the lower ground of existing structures, the development of a liquefaction countermeasure method using a solution-type injection solidification material was advanced, and the following conclusions were obtained.
(1) As a result of long-term durability test using low-strength improved soil with unconfined compressive strength qu=1.0kgf/cm2, no significant decrease in strength was observed after about 400 days.
(2) The solidification time, which affects the penetrability, is greatly affected by pH. Field experiments of the grouting method were carried out, and the following results were obtained regarding the shape, homogeneity, improvement effect, etc. of the improved ground.
(3) The modified body was not spherical, but had a flat shape with a circular plane and a rectangular side. This is thought to be due to the anisotropic effect of ground permeability.
(4) Considering the dilution of the chemical solution by pore water, the concentration of the chemical solution was varied, but the unconfined compressive strength increased as it approached the injection hole, and the solidification was not completely homogeneous. However, it was confirmed that a more homogenous improved product could be produced by considering dilution.
(5) As a result of repeated triaxial tests using undisturbed samples, the liquefaction resistance was more than double that of the unimproved one, confirming the improvement effect on liquefaction.