A laboratory study of the influence of reinforcement stiffness and the size of soil particles on soil pull-out strength

The interaction parameters between soil and reinforcement at their interface play a critical role in influencing the mechanical behavior of reinforced soil systems. Interaction parameters between soil and reinforcement influence reinforced soil behavior mechanically. In this research, the effect of the size of soil grains and the stiffness of the reinforcement on the pull-out resistance of the reinforcement from the soil has been investigated in a laboratory. The pullout resistance of three types of reinforcements with different stiffness in three types of soil with different grain sizes has been investigated. Pull-out tests have been performed at three stress levels of 50, 100, and 150 kPa. To investigate this issue and determine an evaluation for the stiffness of the reinforcement, a device has been built to measure the penetration of solid soil grains in the reinforcement. The results of the tests show that the penetration of soil grains into the reinforcement has a significant impact on the resistance of the reinforcement to being pulled out of the soil. The amount of penetration of solid soil grains into reinforcement increases by reducing the stiffness of the reinforcement and increasing the size of the diameter of the soil grains. For each specific vertical stress level, the greater the penetration of solid soil grains into reinforcement, the higher the pull-out strength of that reinforcement. The results show that with the increase in the diameter of the solid grains of the soil, the pullout resistance of the reinforcement has also increased, but this increase has been more significant in the case of reinforcement with lower stiffness compared to reinforcement with higher stiffness. Also, the difference in the pullout resistance of three reinforcements with different stiffness in fine-grained soil was less than the difference in the pullout resistance of three reinforcements in coarse-grained soil, which indicates the simultaneous effect of reinforcement stiffness and soil grain size on pullout resistance.