| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase the usability of a spacer used between a duct buried by a jacking method and a polyvinyl chloride sewage main duct inserted thereinto. SOLUTION: When polyvinyl chloride sewage main ducts 4 are sequentially inserted into a steel duct buried by the direct propelling of a small diameter jacking method, a spacer 17 is provided between the duct and the sewage main duct 4. This spacer 17 is composed of two divided rings 18 and 18 sandwiching the sewage main duct and bolts and nuts 20 and 21 inserted into the joined parts of these two rings 18 and 18 so as to fasten the rings and both end parts of the bolt 20 are brought into contact with the inner surface of the duct. Thus, by changing a contact position between both end parts of the bolt 20 based on a helical back and forth movement, the inserting position of the sewage main duct, for instance its gradient, is changed and the usability of the spacer is facilitated.</p> |
