Open issues in retaining wall-soil-structure dynamic interaction

Retaining walls are widely used for supporting various structures and infrastructures. However, the dynamic interaction of the retaining walls with the retained structures has not been investigated, while it is evident that during a seismic event the dynamic response of each component of this complex system (wall, soil, structure) may affect substantially the response of the rest and vice versa. This complex phenomenon includes: (a) the dynamic interaction between a wall and a retained single soil layer, and (b) the "standard" dynamic soil-structure interaction of a structure with its underlying soil. In the present study, using numerical two-dimensional simulations, the influence of the wall flexibility on the free-field ground shaking behind the wall is investigated. Emphasis is given on the impact of the wall's presence on the amplification of the base acceleration of the retained soil layer, an amplification generally ignored by the seismic design norms. Subsequently, a structure founded on the retained soil is included in the numerical models and various parameters of the problem are examined. The numerical results of this preliminary study provide a clear indication of the dynamic interaction between a retaining wall and its retained structures.