geogrid
In French: géogrille
Definition
A polymer grid laid in layers in the compacted backfill behind a wall. It ties the wall into the soil mass so they act together. Its length, type and layer spacing are designed: that is an engineer's job.
Sources
CMHA sets a minimum geogrid length equal to the greater of 0.6 times the wall height and 1.2 m. (geogrid length and spacing)
SRW-TEC-004-10: Segmental Retaining Wall Design · Concrete Masonry & Hardscapes Association (CMHA, formerly NCMA and ICPI)