BACKFILL PLACEMENT METHODS LEAD TO FLEXIBLE PIPE DISTORTION

Achieving good results in compacting fill around flexible culverts requires a proper matching of pipe, backfill type, and backfill placement and compaction methods. In the construction of a nuclear power plant, the circulating water lines were designed as 3600-mm-diameter, filament-wound glass-fiber reinforced plastic pipe of low stiffness. Because of a high groundwater table and concern that liquefaction might occur during a seismic event, the specifications called for compaction of all site backfill, including backfill for the circulating water pipe, to 85% relative density. After construction, the pipe was found to be deflected upward beyond project limits. The pipe shape was distorted, and the joints were delaminated. Investigation showed that the backfill was compacted with large self-propelled vibratory rollers operated to achieve the required density with insufficient monitoring of the pipe condition. The emphasis on meeting the compaction requirement was demonstrated by the fact that 171 density tests were conducted at the sides of the pipe and within one diameter width of the pipe, yet observations of the condition of the pipe, which indicated the presence of a problem early in the project, were not given sufficient weight. Observations during construction indicated that the compaction equipment was operated too close to the pipe, and analysis confirmed that this could result in the observed deformations. The investigative team concluded that the pipe could have been properly installed with proper selection of compaction equipment and procedures.

Language

  • English

Media Info

  • Features: Figures; References;
  • Pagination: p. 27-32
  • Monograph Title: Culvert distress and failure case history and trenchless technology
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00666216
  • Record Type: Publication
  • ISBN: 0309055091
  • Files: TRIS, TRB
  • Created Date: Sep 15 1994 12:00AM