PURPOSE: To allow safe, easy, and effective execution of works for the pit base at the bottom, construct easily the pit which offers access to an unutilized underground cavity, in particular a large depth underground cavity, and collect a cutter head etc., which contributes largely to the good utilization and which constitutes a costly part of a shield machine, for another application to enhance the economy.
CONSTITUTION: At the bottom of a pit 2 constructed by excavating downward vertically by a vertical type enclosed shield machine in muddy water pressurization system, dia. enlarged excavation is performed with the dia. of the cutter head 3 of the shield machine 1 enlarged and then the dia. of cutter head 3 is contracted and the head 3 is retreated to inside of the shield body 5. Water stop treatment is performed between the shield body 5 and cutter face 6, and a solidifying material such as aqueous concrete 8 is placed in the dia. enlarged excavation part 7 so as to construct a bottom base which is consolidated with the cutter face 6 and shield body 5. When the intended strength of the bottom base has come to effect, the bulkhead 10 of the shield machine 1 is dismantled, and the cutter head 3, etc., is collected.
SHIMOKOUCHI TAKAFUMI
IWAMOTO HIROSHI
FUJII YOSHIBUMI
YATSUKA MASHIO
TAKENAKA DOBOKU