| 摘要 |
PROBLEM TO BE SOLVED: To provide a defoaming method for excavated soil in a foam shield construction method, which is advantageous to improvement in certainty of defoaming, safety, and workability.SOLUTION: When boring of a subgrade by a shield machine 10 is started, a sludge conveying pump 48, a defoaming agent injection device 43, a crusher 52, and a plurality of slurry discharge pumps 56 are operated, and a defoaming agent having a specific gravity of 1.0-1.1 is injected into a first slurry. Air bubble soil discharged from a conveyor 20 is merged and mixed with the first slurry in a junction pipe 44 to become a second slurry. Here, the second slurry contains the deforming agent and air bubbles of the air bubble soil. Then, the second slurry containing air bubbles is mixed with the deforming agent, thereby defoaming most of the air bubbles contained in the second slurry. The second slurry in which most of the air bubbles are defoamed is transferred to a flow diverter 54 after gravel is broken in a crusher 52, and is transferred to a vibration sieve device 64 by the plurality of slurry discharge pumps 56 through a sludge discharge pipe 50. |
