Effects of physical modeling boundary conditions on the responses of 3 × 3 pile groups to liquefaction induced lateral spreading

In this research, 1 g shake table experiments were conducted to evaluate the effects of boundary conditions on the responses of a 3 × 3 pile group to liquefaction-induced lateral spreading. For this purpose, a rigid and a laminar shear box with similar dimensions were designed and constructed at the Sharif University of Technology. The similitude laws for 1 g tests were implemented to construct the physical models. The profile of the soil layers consisted of a mildly sloped thick liquefiable layer between two non-liquefiable layers. The soil in the free field (far from the boundaries) and near or on the pile groups were fully instrumented to measure various parameters during and after shakings. The piles were also heavily instrumented with pair strain gauges to detect pure bending moments. The results, including acceleration and pore water pressure in various elevations of the free field, acceleration at the pile cap, surficial displacements, and bending moments in the piles, are presented and discussed in this paper. According to the results obtained from these two similar models (differing only by boundary conditions or containers), the response of the model implementing the rigid box is greater, possibly due to wave reflections from boundaries, limitation in movement, and bouncing back of the liquefied and spreading soil from the rigid walls.