*4.3. Analysis Model*

In this study, the RS-DMM, which is a kind of ground-improvement method, is reproduced by an MPS-CAE analysis, and the behavior of each particle assumed as cement slurry and the behavior of the targeted soft ground are evaluated. In order to perform the analysis, two types of stirring wing, NT and DRT, as well as one ground model, were modeled on a computer using CAE.

The stirring wing used in the RS-DMM is composed of an inner wing and an outer wing, which are rotated in opposite directions to penetrate and stir. The rod part of the stirring wing of the NT is columnar, while that of the stirring wing of the DRT is spiral. Figure 5 shows the stirring wing model used in this analysis. In addition, when performing the analysis, it is necessary to set the parameters related to the rotation, penetration, and volume of the cement slurry being injected into the stirring wing. The parameters shown in Table 2 were set by referring to the construction results of the RS-DMM, which is the analysis target of this study.

**Figure 5.** Stirring wing model used for MPS-CAE analysis: (**a**) Stirring wing of NT; (**b**) Stirring wing of DRT.



A columnar ground model, with a diameter of 6000 mm and a height of 5000 mm, was used as the targeted soft ground. In the PBMs, the inter-particle distance, which corresponds to the size of the particles, was set to 40 mm in consideration of the calculation load. In addition, the targeted soft ground was divided into four parts in advance and color-coded so that it would be easier to evaluate the state of the stirring and mixing of the targeted soft ground and the cement slurry to be injected during excavation and the state of stirring by the stirring wing (see Figure 6). The particles of the solidifying material injected from the stirring wing are displayed in gray.

**Figure 6.** Targeted soft ground model used for MPS-CAE analysis: (**a**) Plan (top) view; (**b**) Side view.
