Abstract: An expandable earth anchor is provided with pivoted arms that remain contracted about a bolt rod as the rod, together with the anchor, is driven into the earth. Rotation of the rod with respect to the anchor induces an initial degree of expansion by rotation of the anchor arms about their pivot connection, followed by full expansion of the arms induced by movement of the bolt rod as a result of rotation of a bearing nut against a plate. Arrangements are provided for the expansion of a plurality of anchor devices on a single bolt rod, rendering the system suitable for various types of soils.