Seismic design of deep pier foundations in very soft clayey soils

This paper presents the results of a numerical and theoretical study aimed at identifying optimal design solutions for the seismic design of bridge pier foundations in very soft soil deposits. The reference case study consists of the pier foundations of a cross-river bridge designed to complete a highway over the Po Valley (Northern Italy). The subsoil is of sedimentary origin, with alternating layers of clayey silts and clays interbedded by thin layers of silty sand and peat. The mechanical properties of the soils were defined by conventional site and laboratory investigations, including Resonant Column tests carried out to define the dissipative and nonlinear behaviour of the soils. Numerical 2D and 3D models are used to assess the dynamic soil-structure interaction for the bridge piers, focusing both on inertial and kinematic effects. The main goal of the work is to highlight the influence of the type and layout of the foundation system on the overall seismic response of the bridge pier.