Influence of the condition of pullout holes on the surrounding ground

In recent years, removal work of existing piles has been increasing, and many pulling-out methods for existing piles are being applied. As for the present situation, there is concern that the physical characteristics of the ground will deteriorate due to the holes that remain after pulling out the existing piles (pullout holes). In addition, the filler to be injected into these pullout holes has not yet been specified and the influence of the physical properties of the filler on the surrounding ground has not been elucidated. In this study, therefore, the authors evaluated the influence of pullout holes on the static physical characteristics of the ground by elasto-plastic analysis using a three-dimensional static FEM. As a result, the settlement of the ground surface was seen to increase as the number of pullout holes increased, but it was obvious that the region of the surrounding ground influenced by the settlement does not depend on the number of pullout holes. The authors also clarified that the strength characteristics of the filler injected into the pullout holes do not cause local settlement of the surrounding ground and that it is important to perform reliable filling to the bottom of the pullout holes.