A key consideration in physical modeling of seismic problems in geotechnical engineering is 7 the impact of the model container boundaries on the soil layer response. The container 8 boundaries may alter the stress-strain behavior from free-field conditions through the possible 9 reflection of incident shear waves and generation of P-waves within the soil layers. In this 10 study, 1g shaking table experiments were performed to evaluate the impacts of container 11 boundary conditions on the response of saturated, loose sand layers subjected to harmonic base 12 motions in (1) a free-field condition, (2) with a shallow foundation, and (3) with a shallow 13 foundation supporting a single degree of freedom super-structure. The sand layers were formed 14 in a newly-fabricated laminar shear container that can be converted to a rigid box by adding 15 elements to the end walls. Acceleration, excess pore water pressure, and settlement 16 measurements demonstrate that the rigidity of the container boundaries can have a major 17 impact on seismic behavior of the models. In particular, the observed permanent settlement of 18 the foundations increased by 58% to 115% in the soil models with fixed-end (or rigid) 19 boundaries compared to those in soil models with flexible conditions. This was attributed to 20 non-uniformity of strains near the fixed-end container boundaries and a higher level of energy 21 trapped inside the model. Furthermore, higher spectral accelerations were captured in tests with