| 摘要 |
<p>A trench is dug in the earth, and is filled with a mixt.(a) of cement and bentonite. Before mixt.(a) has set, a guide wire or tube is located in a straight line, and at a specific height, in mixt. (a). The guide wire or tube is clamped at both ends so it is firmly held in a desired position. The mixt.(a) has adequate strength, but is sufficiently soft so that after setting, it can easily be drilled to make a hole or channel. The guide wire or tube is used in conjunction with the drill, so a straight hole is obtd.; and then pipes joined end to end are fed through the hole to make a pipeline. The guide wire or tube pref. has the same density as mixt.(a) so it neither rises nor sinks in the mixt. Process is used esp. for laying large dia. sewage pipes, where a straight pipeline at a specific height can be obtd.</p> |
