Abstract: An expandable anchor assembly is provided for anchoring the threaded end portion of an elongated roof bolt in a borehole. The anchoring assembly includes a hollow outer sleeve in the form of a plurality of symmetrically arranged, longitudinal segmented wall portions with exterior gripping teeth and an inner expander sleeve in the form of a corresponding plurality of longitudinal wall portions symmetrically arranged about a central axis to define an inner threaded cylindrical section. The inner sleeve is captured within and moveable axially relative to the outer sleeve. As the threaded end portion of the elongated bolt is inserted into the inner threaded cylindrical section of the inner sleeve from the trailing end to the leading end thereof, the inner sleeve expands over and clamps around the threaded end portion of the elongated bolt.