The dynamic SSI of a shallow buried plate under impact loading.

Soil is a particulate material, which provides a unique behavior when interacting with its adjacent structure. The dynamic soil-structure interaction (SSI) phenomenon involving in a shallow-buried flexible plate under impact loading is studied. The objective of this study is to understand this interaction process, which has caused load-relieves on the buried plate. The investigation includes an experimental reproduction of the phenomenon and numerical simulation. Plexiglass plates were used as a buried flexible roof structure, and low-velocity impact loadings were generated into the soil. Measurements of the interaction loads between the sand and the plate, and the accelerations of the buried plates were made. Three analytical modeling techniques: a decoupled Single Degree of Freedom (SDOF) model, a nonlinear Multiple Degree of Freedom (MDOF) model and an explicit Finite Element (FEM) model were used to simulate the dynamic responses of the buried flexible plates. A two dimensional Discrete Element (DEM) model was also attempted to simulate the SSI problem. Two aspects of the SSI are incorporated into each of the models to simulate the SSI behavior: relative motions and separation. Under dynamic loading, the buried structure and the soil medium will be traveling at different speeds and will separate from one another at certain moment in time. By modeling soil and structure as separate entities and allowing soil/structure separation, the numerical models are shown to provide reasonable estimation of the experimental results. Different degrees of load-relief phenomenon are experimentally and numerically observed for the buried plates of three different stiffnesses. The results show that the stiffer plates experienced less separation from soil, which was observed in terms of higher loading magnitudes and higher loading durations. The same separation phenomenon was also observed in terms of lower displacement magnitudes and durations. Two parameters are offered to quantify the separate process and the load-relief, namely, separation time and relative load-relief ratio. This research indicated that by incorporating the proper SSI behavior into the numerical schemes, a reasonable prediction of the behavior of the buried plates can be made. When using similar approach in actual design, reasonable results are anticipated.