Abstract: An assembly and methods of installation thereof for supporting and stabilizing a rock structure adjacent a mine tunnel or other underground passageway. The assembly includes an elongated bolt, threaded from both ends for at least a portion of its length. A conventional, mechanical expansion anchor is threaded on one end of the bolt, within a drill hole in the rock structure, and a bearing plate, washer, jam nut and tensioning nut are carried on the other end, outside the drill hole. The tensioning nut is threaded into firm engagement with the jam nut to prevent further threaded advance of the tensioning nut a substantial distance from the termination of the threads. A torque applied to the tensioning nut thus rotates the bolt and expands the anchor shell into gripping engagement with the bore hole wall; torque producing an axial load on the jam nut in excess of its strength causes it to fracture or strip from threaded engagement with the bolt, permitting travel of the tensioning nut.