To provide a discharge structure for the soil around an under-foundation base isolator, capable of discharging the soil refilled to around the foundation in the under-foundation base isolator, in which the sliding surface is formed between the foundation for supporting the skeleton of a building and a ground level.

The soil sliding boundary surface is formed between the soil 6 refilled around the foundation and the ground level 7. The refilled soil is extruded from the soil sliding boundary surface to the outside by the movement of the foundation while the under-foundation base isolator is operated. Since the soil sliding boundary surface is formed between the soil 6 refilled around the foundation and the ground level 7, the refilled soil 6 is scraped out to the side without being collapsed during an earthquake. Since the refilled soil 6 being scraped out is kept scraped out to the ground level around the foundation, it does not resist even when an upper structure is oscillated in the reverse direction due to the oscillation of an earthquake. A boundary member inserted between the refilled soil and the ground level is used as the soil sliding boundary surface.

COPYRIGHT: (C)2010,JPO&INPIT