Depth of cover

The minimum and maximum depth of cover depend on the pipe characteristics and the laying conditions.

Definitions

By convention, manufacturers make a distinction between:

  • the backfill area;
  • the careful backfill area comprised of:
    • the trench bottom and pipe surround backfill up to at least 0.10 m above the assembly crown for flexible pipes;
    • the trench bottom and surround up to the horizontal diameter for rigid pipes
  • the extant soil. 

The backfill zone conditions the pipe stability and/or protection. Its execution must meet variable demands depending on:

  • the pipe characteristics (rigid, semi-rigid, flexible);
  • the external loadings (depth of cover, wheel loads);
  • the more or less rocky or heterogeneous nature of the ground.

The backfill zone varies according to the area involved (rural, semi-urban or urban), and has to take road stability into account.

Other constraints also affect the laying conditions:

  • keeping the pipe frost-free (minimum depth of cover),
  • passing through critical safety areas (railways, motorways, etc.), which require special arrangements,
  • current regulations and local requirements applicable to roadways.