*4.4. Analysis Case and Evaluation Method*

In order to conduct a visible and measurable evaluation of the displacement reduction performance when the stirring wing of the DRT is used, the results are compared with the results when the stirring wing of the NT is used.

In the evaluation of the displacement reduction performance, attention was paid to the moving velocity of the particles assuming the targeted soft ground. In order to suppress the occurrence of displacement due to the construction, it is important to discharge the surplus soil generated when the solidifying material is injected. For the particles inside the targeted soft ground during the analysis, the velocity components in the *Z*-axis direction were color-coded, and the mechanism of the discharging surplus soil and its performance were evaluated. In order to quantitatively evaluate the performance of the discharging surplus soil, the volume of discharging surplus soil was estimated by measuring the *Z*-axis velocity of the particles existing in the specified region and calculating the flow ratio. The volumes of discharging surplus soil in the two cases of the stirring wing of the NT and the stirring wing of the DRT were estimated, and the results were compared.

In addition, in order to compare the construction process of the improved body when the stirring wing of the NT is used and when the stirring wing of the DRT is used, the cross section during the analysis is cut out, and the behavior of the particles, assuming the cement slurry and the targeted soft ground, were visually evaluated. Specifically, the difference in the quality of the improved body due to the difference in the stirring wing, the effect of the stirring wing of the DRT on the improved body, and the distribution of the solidifying material were evaluated.
