Pullout Resistance and Load-Slip Response of Mechanically Damaged Geogrids

Pullout tests were conducted on 30 pre-damaged specimens of a uniaxial and a biaxial polyester geogrid to determine the effect of damage on their pullout resistance and end displacement. The specimens were embedded in crushed aggregates and subjected to surcharge loads of 14 kPa and 20 kPa. The results showed that substantial damage in the tested specimens could reduce their maximum pullout force by up to 33% and their pullout stiffness by 50%, where pullout stiffness is defined by the ratio of the maximum pullout force to the corresponding slip (KN/mm). For moderate amounts of damage, the reduction was in the order of 10% to 14%. These results suggest that the present safety factors for installation damage (1.1 to 3.0) may be applicable to pullout resistance, but they may need to be modified for controlling displacements in geogrids.