| 摘要 |
The apparatus straddles the position in which the pipe is to be placed. Diggers on either side of the pipe cut parallel trenches to either side of the level in which the pipe will be laid. Adjustable height patterns control the depth of the trenches and support the walls. A trencher ploughs clear the area between the two trenches and a pump draws off the material which has been removed. The pattern may be continuous or discontinuous. The ploughs are operated by jacks via levers. |
