| 摘要 |
PROBLEM TO BE SOLVED: To lower a casing simply and quickly without requiring a space by erecting a portal crane provided with a hoist movably longitudinally and laterally on a frame made of supports and a beam material on a casing installation section. SOLUTION: When an open shield machine 1 advances while excavating and discharging sediment from the front face or upper face of an excavation section 2 with an excavator 7, a portal crane 19 is also moved. A concrete casing 8 to be lowered is conveyed by a carriage 23 to below a concrete casing hoist section 21 with the upper faces of existing concrete casings 8 aligned in tandem, it is hoisted by a hoist 18 and is moved to above a casing installation section 3 behind the open shield machine 1, and it is lowered in the casing installation section. It is unnecessary to use a heavy machine such as a motor truck crane or to use a bridge type or portal crane traveled on a rail installed separately, and the casing 8 can be lowered simply and quickly without requiring a space.
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