| 摘要 |
PROBLEM TO BE SOLVED: To enhance strength of a columnar ground improvement body formed in the ground by a cast-in-place construction method. SOLUTION: The ground is excavated up to the prescribed depth by a ground improvement machine having an excavator 20 in a tip part of a hollow shaft 10. Afterwards, excavating surplus soil D of a ground improvement area is supplied to a central area 51 of an excavating hole 40 from a central part 21 of the excavator 20 via a soil supply passage (an inner tube 31) provided in the hollow shaft 10 in a process of pulling up the ground improvement machine, and a ground improvement material (cement C) is supplied to soil of an outer peripheral area 52 of the excavating hole 40 from an outer peripheral part of the excavator 20 via a ground improvement material supply passage (an outer tube 32) provided in the hollow shaft 10, and since the central area 51 of the ground improvement body 50 is soil before a ground improvement and the outer peripheral area 52 becomes improved soil, the ground improvement body 50 becomes a shape near a state of driving a hollow cylindrical body in the soil, and becomes a ground improvement body 50 having high flexural strength.
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