| 摘要 |
PROBLEM TO BE SOLVED: To provide the collapse preventive construction method for an upper sand bed in a slurry shield in which the taking-in and collapse of the sand bed are prevented even under the state, in which the slurry shield suspends, and ground-surface subsidence or the like is prevented without loosening a peripheral ground. SOLUTION: A carboxymethyloellulose(CMC) solution is injected to the cutting-face surface 6 of a slurry shield 1 from a CMC-solution injection pipe 2 in the case of the stoppage of the slurry shield 1, and the generation of the taking-in and collapse of the upper sand bed and the blows or the like of slurry is prevented by utilizing a fact that the specific gravity of the CMC solution is lighter than that of slurry. The mixed body of a bentonite solution and silicic acid is injected from a clay-shock injection pipe 7 for a skin plate 8 during the pipe jacking of the slurry shield 1, and friction between a machine and sand is reduced while the looseness of a ground is inhibited by generating a slurry-film effect 9 between the upper sand bed and the skin plate 8.
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