Dilation stress in borehole induced by a spiral anchor

Applying a twist to a flat sheet bar makes spiral bar. It is easy to apply the spiral bar to a ground anchor, since the spiral bar has a high performance to resist to a pull-out from ground. A characteristic of the spiral bar is studied for the introducing to an actual ground work. It is proposed to use the spiral bar for a ground anchor. The spiral anchor fixed by grouting or a filling material to in a borehole acts a dilation force on borehole surface. Then, the spiral behavior is satisfying enough to resist as a ground anchor.