Interaction between Geogrid and Tire Chips-Sand Mixture: Pullout Test Simulation

Abstract

The aims of the study were to measure and calculate the interaction coefficient between geogrid and sand and between geogrid and a tire chips-sand mixture using a laboratory test and numerical simulations. Numerical simulation was imperative for the sensitivity analyses of the laboratory test results to find the important parameters. Two types of material were used as backfill, namely sand and a tire chips-sand mixture. The sand and tire chips in the mixture were in the proportion by weight of 70 and 30%, respectively. Polyfelt geogrid was used as geosynthetic reinforcement with a tensile strength of 97.48 kN/m from the in-air tensile test. Pullout tests were carried out on a large-scale pullout machine. The shear strength parameters of Ayutthaya sand and the tire chips-sand mixture were a 29.8° friction angle with cohesion of 15.6 kPa for sand and a 24.4° friction angle with 14.3 kPa cohesion for the tire chips-sand mixture. The results revealed that the interaction coefficient obtained from the pullout test was 0.7 and 0.6 for the sand and tire chips-sand mix, respectively. Numerical analyses were also performed using finite element software. The results of the numerical simulation agreed reasonably with the laboratory results. Sensitivity analyses were carried out for the pullout test by varying the interaction coefficient and axial stiffness of the geogrid. These two important parameters were found to affect the efficiency of the geogrid reinforcement.