The teardowns of social infrastructures, including civil engineering structures, have been increasing due to the aging of these structures, which were built in a period of high economic growth, and to a decrease in their utilization due the recent drop in population. The number of existing pile foundations being pulled out has gradually become a lot more than that of pile foundations being newly installed. However, after the pulling out of a pile foundation, the mechanical characteristics of the surrounding ground are of great concern due to the existence of the holes that form when the existing piles are removed (pulling-out holes). There are no regulations yet on the filling material to be injected into these holes, nor has the way that the strength of the filling material influences the surrounding ground been elucidated. The present study evaluates the manner in which the pulling-out holes of existing pile foundations influences the static and dynamic characteristics of the surrounding ground by means of a two-dimensional static and dynamic finite element analysis. The special qualities required for the filling material to be injected into these pulling-out holes are also clarified in this study.

Keywords: Existing pile foundation, Pulling-out method, Pulling-out hole, Finite element method