| 摘要 |
PROBLEM TO BE SOLVED: To prevent sand and soil from invading in a machine from between an enlargement and reduction segment and a tail seal by using the enlargement and reduction segment capable of width enlargement and simultaneously enlarging the enlargement and reduction segment at the time of width enlargement of a building block. SOLUTION: With regard to a shield machine 1, right and left excavation blocks 5, 7 are expandably disposed on the front part of a cross body block 3 in a planar view and right and left construction blocks 9, 11 are expandably disposed on the rear part by expansion mechanisms 21, 23. Excavation is performed in a width reduction state to construct a segment 65, the excavation blocks 5, 7 are width-enlarged at a width enlargement spot to continue excavation, and an enlargement and reduction segment 50 is constructed in a width reduction state. The construction blocks 9, 11 are width-enlarged, the enlargement and reduction segment 50 is expanded by a slide jack 55 to prevent sand and soil from invading from a gap between tail seals 45, 46. The bolt hole of a joining bolt with an adjacent segment 65 is formed oblong, and the bolt inserted before width enlargement is tightened after width enlargement completion. Thus, sand and soil can be prevented from invading in a machine at the time of width enlargement. |
