Nonlinear Simulation of the Seismic Performance of Unreinforced and Fiber-Reinforced Rigid Inclusions in Soft Soil Site

Rigid inclusions (RIs) are a cost-effective ground improvement solution used to enhance bearing capacity and reduce settlement in soft soil sites. However, during earthquakes, ground deformation can induce transient kinematic lateral loading, potentially causing bending failure due to the brittle nature of concrete. Fiber reinforcement, commonly used for crack control and enhancing concrete flexural ductility, offers potential to improve flexural capacity of RIs. This study investigates the seismic response of unreinforced (URI) and fiber-reinforced (FRI) rigid inclusion using two-dimensional (2D) FLAC analysis, with a focus on soil-structure interaction (SSI) and flexural capacity of RIs at near-failure condition. The 2D plane strain model consists of a typical strip footing supported by RIs in soft clay site. The RIs were modeled using FLAC pile elements with nonlinear moment-curvature to capture plastic hinge development. Dynamic SSI simulations were performed to evaluate RI element response that was embedded in soft clay soil, modeled using the PM4Silt soil constitutive model. The simulations were performed using ground motion scaled to cause near-failure conditions in unreinforced RIs, followed by a simulation of FRI case using identical motion. Results indicate while FRIs provide slightly higher flexural capacity, the calculated maximum moments still approach their capacity, indicating a limited margin of safety.