Evaluation of Geofoam Effects on Seismic Response in Cantilever Retaining Wall

In the present numerical study, using the finite difference software FLAC (version 7), the effect of EPS geofoam inclusions was investigated on the improvement of the retaining walls response in static and dynamic conditions. In order to evaluate the performance of geofoam inclusions, parameters such as wall height, type of retaining wall (yielding and non-yielding types), density and thickness of geofoam inclusion were studied. Two earthquake records were selected for present research: far-field and near-field. Retaining walls at the heights of 6 and 9 m and two types of EPS geofoam, EPS15 (γ = 0.15 kN/m³) and EPS20 (γ = 0.2 kN/m³), were modeled at relative thicknesses (t/H) of 0.1 and 0.2. According to the results, the isolation efficiency of geofoam inclusion against the forces imposed to the retaining wall, A_P, was achieved in static condition more than dynamic condition. In the present study at seismic record of the near-field, EPS geofoam showed a better performance than the far-field record in reduction of lateral forces. Also, the isolation efficiency of geofoam inclusion against the permanent displacement, A_d, and application point of the seismic force to the yielding retaining wall were investigated. The results of the analyses indicate that, geofoam inclusion can reduce seismic lateral forces acting on yielding and non-yielding retaining walls by 40% and 50%, respectively. In addition, isolation efficiency of geofoam inclusion, A_d, for yielding wall may reach values in excess of 40%, depending on peak acceleration amplitude (a_max), excitation frequency (f), relative frequency (f/f_n), geofoam relative thickness (t/H), and wall height (H).