| 摘要 |
PROBLEM TO BE SOLVED: To change a bit at a low cost in a short period while avoiding complication of a structure. SOLUTION: A bag 30c free to increase and decrease in diameter is inserted into a chamber 26 by use of a sealing device 30 attached to a selector valve and then compressed air is injected into the bag 30c to increase the diameter of the bag 30c so as to fill the chamber 26 with the compressed air injected in the bag 30c. Next, the process of forming a soil improvement zone 34 ahead of a shield excavator 10 is performed to form the soil improvement zone 34, and the bag 30c is contracted by removal of fluid therefrom and is removed from within the chamber 26 to hollow out the chamber 26; operators get into the chamber 26 and perform the work of changing a drill bit 12d. After the work of changing the drill bit 12d is finished, the shield excavator 10 performs normal excavation. |
