The interaction characteristics of the interface between geogrids reinforcement and soil as well as geogrids reinforcement and interlock concrete blocks are the two key indexes for the stability of interlock segmental reinforced retaining walls. It is found that the two-way geogrids reinforcement would be tension fracture when the normal stress is over 24.8 kPa from the results of pullout test

and under this condition the tensile strength of the geo-grid is lesser than that when the two-way geogrid is tensed in the air. The strength envelopes is composed by two straight lines

the frictional strength between two-way geogrid reinforcement and interlock concrete blocks increases with the increase of normal stress when normal stress is less than 24.8 kPa and is invariable when normal stress is over 24.8 kPa.