| 摘要 |
First and second frame assemblies (18, 20) respectively provided with a pair of plate-like earthretaining means (24, 36) are alternately advanced by drive means (22). While the first and second frame assembies are alternately advanced, the ground (14) is excavated so as to form a channel (16). A reaction force acting on the first frame assembly (18) when the second frame assembly (20) is advanced and a reaction force acting on the second frame assembly (20) when the first frame assembly (18) is advanced are respectively transmitted to the ground defining the channel by the action of first and second position maintaining means (32, 52). When the first and second frame assemblies (18, 20) are advanced by required distances, a new pipe (12) is placed in the channel and connected to a pipe (12) already installed.
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