BEST PRACTICES – GEOGRID REINFORCEMENT

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.

Best Practices, Designs, Earth Retention
February 28, 2022

NCMA & AASHTO WALL EMBEDMENT REQUIREMENTS

Embedment Rules:

Embed to a depth that provides 4-feet horizontal bench to daylight (i.e. For a 4H:1V slope, embed the toe of wall 1-foot minimum)
AASHTO requires 24” minimum for slopes steeper than a 4H:1V
AASHTO requires 24” minimum when the wall is in a water application with no permanent erosion prevention measures such as rip-rap or a hardened liner above grade.
Embed toe of wall below curbing or other site components to be installed after wall construction.