| 摘要 |
PROBLEM TO BE SOLVED: To provide a ground improvement method to improve the ground over an extensive range by preparing a plurality of improvement materials without generating any overlapping areas or non-improved areas. SOLUTION: A rod 20 having injection nozzles N1 and N2 is inserted in a bored hole cut in the ground to be improved, the fluid to cut the ground is ejected J1 and J2 from the ejection nozzles, or the ground improvement materials are ejected to cut the ground and mix the ground with the improvement materials (a jet process), and the rod 20 is pulled upward while rotating the rod. At least a pair of ejection nozzles N1 and N2 are provided on the rod so that the fluid ejected in the jet process forms the crossing jets J1, J2, J1A and J2A, and in the jet process, each angle of ejection of the ejection nozzles N1 and N2 is regularly changed so that the section of the area to cut the ground so as to be mixed with the improvement materials is a non-circular closed shape.
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