Confinement and shear behavior of geocell-reinforced granular aggregates considering junction failure under large-scale triaxial compression

The lateral confinement provided by geocells is mobilized through the combined response of cell walls and junctions. In laboratory studies, however, geocells are often simplified, particularly in their junction configurations, and their mechanical characteristics differ from those of engineering geocells. This study examines the mechanical behavior of geocell-reinforced granular aggregates considering different geocell types and reinforcement arrangements. Three model geocells were employed: LWJ, with PP cell walls connected by bolts and metal washers to represent newly developed liquation-welded geocells; UWJ, with HDPE cell walls connected by bolts and nylon washers to represent conventional ultrasonic-welded geocells; and MTJ, with PET cell walls connected by plastic mortise-and-tenon fasteners to represent newly developed mortise-and-tenon geocells. Large-scale static triaxial tests investigated the effects of geocell type, vertical spacing, layer number, and confining pressure on stress–strain response, radial deformation, and apparent cohesion. An apparent-cohesion model incorporating junction strength and reinforcement layout was developed. The results show that the distinct responses of the three geocell types were closely associated with differences in junction failure behavior. LWJ specimens mobilized the highest deviator stress and apparent cohesion but exhibited an abrupt post-peak loss of confinement following junction peeling. UWJ specimens maintained strain hardening because of high-density polyethylene ductility despite lower confinement capacity. MTJ specimens exhibited strain softening associated with progressive interlock failure. Reducing vertical spacing and increasing layer number enhanced strength and suppressed lateral bulging, whereas reinforcement efficiency decreased nonlinearly because of the overlap between adjacent confinement zones.