| 摘要 |
<p>A trench is dug under the pipe. A collapsible means formed by a supple and deformable envelope is conveyed into the trench as it is dug in a state folded or coiled upon itself. The envelope is filled with water by a pump assembly and unfolded in a diverging cone, and progressively substituted for materials extracted as the trench is dug. The pipe is then lowered into and positioned in the trench by the escape of water out of the envelope through orifices or valves.</p> |
