| 摘要 |
PROBLEM TO BE SOLVED: To form a foundation improvement column by using an excavation shaft having single-shaft constitution, preventing corotation through the simple constitution, and smoothly discharging excavation earth.SOLUTION: A single-body shaft 1 driven by a rotary driving device to rotate is provided with a blade body 2 which agitates and smooths excavation earth onto the ground, and a holing bit 5 which has an excavation blade at an outer periphery and a discharge hole for a foundation improvement material 12 at a lower end, and excavate the ground. An excavation surface guide wall body 3 which makes an excavation hole smooth is provided at an outer periphery of the blade body 2. The single-shaft body 1 between the blade body 2 and holing bit 5 is provided with a suppression blade 6, which has an outer peripheral end cut into the excavation surface to rotate relatively to rotation of the blade body 2 and holing bit 5, and thereby agitates and mixes the excavation earth, in a rotatable state. With this constitution, when the suppression blade 6 is cut into the excavation hole, relative rotation with the single-body shaft 1 is caused to prevent corotation and to accelerate the agitation, and surplus excavation earth accompanying the injection of the foundation improvement material 12 in the excavation is discharged onto the ground through the excavation hole which is made smooth so as to form the foundation improvement column. |
