| 摘要 |
PURPOSE:To safely exchange a tail seal without deterioration of sealing property by detachably fitting a tail seal on the inner circumference of the rear part of a shield, and fitting a new tail seal before the rear end of the shield slips out from the front of an old seal. CONSTITUTION:A tail seal 2 is detachably fitted on the inner circumference of the rear part of a shield 1, and after releasing connection of the tail seal 2 to the shield 1, the shield 1 only is advanced, remaining the tail seal 2 on the outer circumference of an existing segment S1. Nextly, before slipping out of the rear end of the shield 1 from the front of the tail seal 2, the shield 1 is stopped and a new tail seal 2 is fitted on the inner circumference of the rear part of the shield 1. A freezing pipe 8 is buried in the rear end part of the shield 1, while keeping the sealing condition with the tail seal 2 refrigerant is brought to flow in the freezing pipe 8 to freeze ground Y around the rear end part of the shield 1, and the tail seal is exchanged. |
