An interaction model for seismic stability analysis of caisson type structure

An interaction model was developed for a gravity type caisson with granular backfill sandwiching a protective compressible layer as cushion, whose function is to improve the seismic stability of the structure. Interfaces on either side of the cushion were modeled as elements of finite thickness having different stiffness and constitutive properties. Participation of each element of the interaction system was taken into the account by incorporating appropriate factors at the respective interfaces. Seismic analyses were performed on a gravity type caisson using the developed model. Comparison of the analysis results with a similar caisson without any protective cushion showed that the use of cushion (made from a compressible recycled material) yields a significant reduction of seismic load on the structure.