The National Concrete Masonry Association (NCMA) has put together a collection of  practical, field proven solutions.  This excerpt is for best practices when using geogrid reinforcement. 

Reinforcement Empirical Limits:

  • Minimum grid length =
    • 60% H static,
    • 60% bottom/middle and
    • 90% upper layers for seismic
  • Absolute minimum grid length = 4.00 feet
  • Minimum anchorage length (beyond failure plane) = 1 foot
  • Maximum vertical spacing =
    • 16 inches if % passing #200 is >35%
    • 24 inches if % passing #200 is <35%
  • Maximum vertical spacing = twice (2x) the block depth
  • Minimum soil cover between layers = 3 inches
  • Maximum height to first layer of geogrid = 18 inches

    For more information on best practices for segmental retaining walls, download the NCMA guide here.