Abstract: Soil seismic response analysis is of great meaning to the seismic response and seismic safety evaluation of structures. In this study, the non-linear seismic response law of soil in free field under uniform and non-uniform excitation and its influencing factors are studied by means of large-scale shaking table model test, which can provide support for analyzing the seismic failure mechanism of structures. By analyzing the dynamic characteristics of soil, acceleration peak magnification coefficient, shear stress-shear strain curve and soil settlement, the ground motion response characteristics and variation of free-field soil under different earthquake motions and different seismic intensities are studied. The results show that the non-linear development degree of soil is not only related to the record of ground motion, but also to the input mode and loading level of ground motion. In the case of large earthquake or longitudinal non-uniform excitation, inconsistent movement of free-field soil leads to stronger soil structural change, decrease of frequency, increase of damping ratio, weakening of soil stiffness and relatively faster nonlinear development of soil. The variation law of soil shear stress-shear strain curve and settlement curve also reflected the plasticity development of soil. The conclusions obtained are consistent with the observed macroscopic phenomena of the free-field seismic response, which mutually corroborated the rationality of the results.

Key words: non-uniform excitations, shaking table test, seismic response, soil nonlinear