IS 15061 provides structural design methodology for buried flexible pipelines. Unlike rigid pipes (concrete, CI) which resist loads by stiffness, flexible pipes (PE, PVC) rely on soil support. The key design check is deflection — max 5% of pipe diameter.
Code of practice for structural design of buried flexible pipelines (PE, PVC, steel with flexible joints) under earth and traffic loads.
Key Values
Max allowable deflection5% of pipe diameter
Min cover depth0.6m (no traffic), 1.2m (traffic)
Bedding angleStandard 120°
Practical Notes
! Proper bedding and compaction is MORE important than pipe wall thickness for flexible pipes.
! Never compact directly over flexible pipe with heavy equipment — use hand compaction for first 300mm.
! Deflection testing with mandrel should be done 30 days after backfilling (after initial deflection stabilizes).
! For deep burial (>6m), long-term deflection can be 1.5× initial — account for creep in PE pipes.