In-situ characterization of Soil Structure Interaction through measurement of Impedance Functions

In situ characterization of structural behaviour under seismic hazard provides an opportunity to acquire experimental data that improve our understanding of soil-structure interaction (SSI). Experimental programs such as Lotung and Hualien in Taiwan, EuroProteas in Greece and NUPEC in Japan, are amongst the most known. Such investigations aim at studying a structure with a rigid shallow raft and measuring the seismic impedance functions at soil-foundation interface. Indeed, impedance functions are by far the most widely used tools to study SSI. In this paper, considering feedbacks from these in situ tests, we aim at assessing the feasibility to acquire measurements of the seismic impedance functions for any structure with a rigid shallow foundation. To test the proposed methodology, we carry out a laboratory test with a small-scale device: the soil is represented by a model material (silicon rubber block) and the foundation by a cylindrical shaker inducing monitored harmonic vertical forces on the silicon rubber block. Experimental tests are paired with numerical simulations to identify, by inverse analysis, unknown parameters and to compute the order of magnitude of displacements and forces within the system. This paper presents the laboratory test setup, the experimental design, and the results of the associated simulations.