This study investigates the load transfer mechanisms between adjacent reinforcement layers in geosynthetic-reinforced soil (GRS) structures. Using the Discrete Element Method (DEM), a numerical model was developed to simulate a three-layer reinforcement system and explore the composite behavior resulting from soil–reinforcement interactions when reinforcement layers are closely spaced. The model replicates a controlled laboratory setup, in which a central active reinforcement layer is subjected to pullout loading while being confined by two passive layers above and below. TResults indicate that the pullout behavior of the active layer closely resembles that of a single reinforcement layer, with its tensile response primarily controlled by interfacial shear resistance. Analysis further shows that the increase in interface shear stress in the passive layers exhibits a linear relationship with the corresponding increase in the active layer, and this trend remains consistent under different normal stress levels ranging from 15 to 50 kPa. In addition, particle size was found to significantly affect stress redistribution: larger particles improved mechanical interlocking, thereby enhancing shear stress transfer to passive reinforcement layers. As a result, the vertical spacing at which composite interaction becomes significant was found to depend on the particle size distribution of the soil.
Jia et al. (2026) studied this question.