Abstract: This paper developed a subgrade discrete element model and a geocell finite difference model. A series of coupled finite difference method-discrete element method (FDM-DEM) numerical calculations was carried out to study the compaction behavior of geocell-reinforced subgrade under vibration loads. The contribution of geocells to the horizontal residual stresses after vibration compaction was further revealed. Additionally, the prestressing effect of the geocell-reinforced subgrade was proposed to reflect the reinforcement improvement due to the stretching of geocell pockets induced by the infill materials after loading and unloading during construction. The mechanism of the prestressing effect of geocell-reinforced subgrade was discussed by combining the microscopic particle contact, the changes in coordination, and the stress path during compaction process. The results suggest that geocells can improve the resilient modulus of reinforced subgrade and significantly increase the horizontal residual stress compared to the unreinforced subgrade. Under vibration loading, the geocell shows a flared shape with an upper opening. After compaction, the geocell pockets stretch wider, and the maximum tensile strain in the geocell walls ranges from 0.17% to 0.21%. The distribution of contact force also indicates that the force chain develops from a vertical to horizontal direction after vibration compaction, reflecting the increase of horizontal residual stresses. The geocell further enhances the development of lateral contact forces among particles.

Key words: geocell, reinforced-subgrade, vibration compaction, numerical simulations, FDM-DEM coupling