This study focused on the middle-pressure jet grouting method, which has a complicated development mechanism for the columnar soil-improved body, with the aim of establishing a computer-aided engineering (CAE) system that can simulate the performance on a computer. Furthermore, in order to confirm the effect of middle-pressure jet grouting with mechanical agitation and mixing, a comparative analysis was performed with different jet pressures, the development situation was visualized, and the performance of this method was evaluated. The results of MPS-CAE as one of the CAE systems showed that the cement slurry jet ratio in the planned improvement range, including the periphery of the mixing blade, by the middle-pressure jet grouting together with the mechanical agitation and mixing was increased and a high quality columnar soil-improved body was obtained. It is expected that the introduction of CAE will contribute to the visualization of the ground, and that CAE will be an effective tool for the visual management of construction for ground improvement and the maintenance of improved grounds during the life cycle of the ground-improvement method.

Various issues have been encountered in the removal work of existing piles, such as existing piles being left in the ground, the subsidence of the surrounding ground, and the deterioration of the ground environment when reusing the site. However, there are no regulations for the filling material to be injected into the draw holes that form after the removal of existing piles or for the removal work itself. In this study, therefore, for an evaluation of the effect of the insertion of the casing by rotation on an existing pile in the removal work of existing piles, the effect of the stress loaded onto an existing pile when the casing is inserted into the ground using MPS-CAE and the mechanism of its occurrence are clarified. As a result, it is found that the inner diameter of the casing used for the diameter of an existing pile, the value of the plastic viscosity of the drilling fluid, and the mechanism of the stress loaded onto an existing pile against the pile diameter can be evaluated such that the destruction of the existing piles can be avoided.