| 摘要 |
PROBLEM TO BE SOLVED: To replace a bit while a lowering of propulsion efficiencies is being prevented. SOLUTION: If an excavation bit 12d has been worn away, requiring replacements, the propulsion of a shield propulsion machine is stopped. For replacing the bit 12d, each opening 12e of a cutter disk is closed by a plate 32 for preventing gravel, earth and sand from flowing in. When the opening 12e is closed, a setting agent A comprising a mixture of a highly water absorptive resin and water is supplied. The agent A is injected through a path provided in the propulsion machine from a groove in the bit 12d toward excavated earth and sand. Since highly water absorptive reins are contained in the agent A mixed into earth and sand, the resins absorb moisture in the earth and sand and are solidified so that an impervious layer B is formed around the disk. When the layer B is formed, a worker gets into the interior and removes bolts and nuts 12j and detaches a fixed plate 12i and the bit 12d and then sets a new excavation bit 12d and fixes the bolts and nuts 12j. |
