EFFECTS OF METHODS A AND B BACKFILL ON FLEXIBLE CULVERTS UNDER HIGH FILLS

Two large-diameter; structural steel plate pipes embedded in deep embankments were instrumented and tested to assess circumferential soil stress distributions, deformations, and internal strains. Construction techniques included the "imperfect trench" method (method B backfill) and positive projection (method A backfill). Method B uses layers of baled straw over a 114-in. (290-cm) pipe under 89 ft (27 m) of overfill. Method A consists of ordinary embankment materials surrounding twin, 108-in. (274-cm) pipes under 160 feet (49 m) of overfill. Method B soil stress-fill height functions were nonlinear; strains and strain gradients in the pipe walls were larger than those observed for the method A installation. Radial displacements were smaller than those observed for the method A installation. Method A soil stress-fill height functions were essentially linear. Observed deformations and stresses were compared with theoretical values obtained from Marston's theory, the Iowa deflection formula, and the ring compression method. The ring compression method provided correlations that were sufficient for design purposes. Internal strains were correlated with external, measured pressures by nautral point and finite element methods. Baled straw inclusions are not recommended for future designs of flexible pipe culverts. Design can be based on ring compression with a safety factor of 4, but a 70 percent increase in soil densities may be anticipated over a period of time after fill completion.

Media Info

  • Media Type: Print
  • Features: Figures; References;
  • Pagination: pp 41-55
  • Monograph Title: SOIL MECHANICS
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00081326
  • Record Type: Publication
  • ISBN: 0309023548
  • Files: TRIS, TRB
  • Created Date: Mar 26 1975 12:00AM