Laboratory Pullout Testing Of Biaxial Geogrid in Sand-Crumb Rubber Mixtures

In the present study, a series of pullout tests were conducted to understand the sand-crumb rubber interaction behaviour with biaxial geogrid. Six different crumb rubber–sand mixtures with mixing ratios of 0:100, 10:90, 20:80, 30:70, 40:60 and 50:50 by volume were studied. Pullout tests were conducted at five different normal stresses (i.e., 20 kPa, 40 kPa, 60 kPa, 80 kPa and 100 kPa), where pullout forces were applied to the geogrid specimen at a constant strain rate of 1 mm/min. The normal stress-dependent pullout capacity was obtained from each test. The peak pullout load was observed at the verge of the failure of the geogrid. Two different types of failure of the geogrid were observed (i.e., slippage and rupture failure). The pullout test results were interpreted in terms of pullout resistance factor (F), which represents the interaction between backfill material and geogrid specimen. The resistance factor was found to increase with the increase in rubber percentage in the mix from 10% to 30%. The maximum value was found to be 1.07 at 30% rubber percentage in the mixture at 20 kPa normal stress. However, at 40% rubber percentage in the mixture, F was found to reduce. A similar trend was also observed for other normal stresses. Furthermore, strain variation in the geogrid due to pullout loading was also studied. The strain was found to decrease with the addition of rubber content. Strain reduced by 48% at 30% rubber content. Hence, the 30:70 mixing ratio of rubber-sand showed the highest interaction, thus giving the optimum pullout capacity of the