Mud pressure shield construction method and mud pressure shield excavator

摘要

PROBLEM TO BE SOLVED: To provide a slurry pressure shield method capable of excellently achieving boring work without requiring a large amount of a slurry forming material even if a part or a whole of natural ground is dehydrated, and a slurry pressure shield machine.SOLUTION: An inventive slurry pressure shield method uses a sealed type shield machine 1 which is equipped with a rotary cutter 2 for boring a working face of natural ground at its front end and equipped with a cutter chamber 3 behind the rotary cutter 2. A slurry forming material is added to and mixed with excavated sediment bored by the rotary cutter 2 and taken into the cutter chamber 3 so that the excavated sediment is converted into slurry having plastic fluidity and impermeability, and boring work is performed while generating a slurry pressure by pressurizing slurry filled in the cutter chamber 3. A first slurry forming material including at least one of bentonite, clay, polymeric material, and air bubbles and a second slurry forming material consisting of fresh water to which a surface tension depressant is added are simultaneously injected into the cutter chamber 3 as the slurry forming material to be added to the excavated sediment.