| 摘要 |
PROBLEM TO BE SOLVED: To easily and surely move an injecting position from an end portion during excavation to a position above an agitating blade during hoisting so as to shorten construction time and an increase agitating and mixing rate during subsoil improving and earth retaining work whereby a solidifying agent such as cement milk is agitated and mixed with the in-situ earth and sand as the solidifying agent is injected so that a soil cement column or the like is created under the ground. SOLUTION: A discharge opening switching device comprises a combination of three mechanisms: a switch mechanism for causing valves fed to an upper discharge opening 8 and an excavating rod to be opened or closed at the same time by the expanding or contracting movement of a piston and a cylinder, between the excavating rod and an upper rod 30; a mechanism for effecting the opening and closing of a lock pin in rotating direction, for maintaining the switching of the switch mechanism; and another mechanism ensuring that confirmation can be made above the ground, based upon the movement of a bar 36 raised from a coupling band 31 fixed in a position above a lower rod 32, because each time the discharge opening 8 is changed, the position of the lower rod 32 is moved from a drive by an amount equal to the expansion or contraction of the switch mechanism.
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