Mechanical expansion anchor shell

A one-piece expansion shell for use with a tapered camming plug in a blind drill hole of predetermined diameter in a rock structure to anchor therein an elongated rod having an externally threaded end portion engaged with an internally threaded opening in said plug, said expansion shell comprising:

• a) a ring-like base portion concentrically arranged about a central axis;
• b) a plurality of leaf portions extending integrally from said base portion in a common direction and concentrically arranged about said central axis, each of said leaf portions having inner and outer surfaces, lateral side edges and free ends lying in a common plane perpendicular to said central axis;
• c) said outer surfaces including a plurality of stepped serrations extending laterally thereof, said outer surfaces, including said serrations, lying substantially on a circle centered at said central axis in all planes perpendicular to said central axis, said circle having a maximum diameter in at least one of said planes which is less than said predetermined diameter;
• d) a group of teeth on each of said leaf portions extending outwardly from said external surface thereof, each of said teeth having a crest lying on a line parallel to said central axis and spaced from said central axis by a distance substantially equal to one-half said predetermined diameter, the teeth of each of said groups being vertically aligned along a lateral edge substantially coincident with one of said leaf portion side edges.

A combined resin-mechanical anchoring system for supporting and reinforcing a rock structure having formed therein a blind drill hole of predetermined diameter, said anchoring system comprising:

• a) an elongated bolt having threads extending from one end for at least a portion of the length thereof;
• b) a tapered camming plug having relatively larger and smaller ends and a central bore with internal threads for engagement with said bolt threads;
• c) a radially expansible shell including a plurality of leaf portions each having internal and external surfaces and side edges, said side edges of adjacent leaves being separated by axially extending slots, said shell being substantially circular in cross section and symmetrically arranged about a central axis;
• d) means for supporting said shell upon said one end of said bolt with said smaller end of said plug extending into said shell;
• e) a two-compartment resin cartridge adapted for insertion into said drill hole in advance of said one end of said bolt with said plug and shell thereon, and for rupture of said cartridge by advance of said bolt to release the components thereof for mixing;
• f) said external surfaces of said leaf portions including a plurality of stepped serrations on at least portions of said leaf portion external surfaces extending substantially the full width thereof, said external surfaces, including said serrations, in the unexpanded condition of said shell having a maximum distance from said central axis less than one-half said predetermined diameter;
• and
• g) at least one tooth on each of said leaf portions extending outwardly from said external surface thereof, each of said teeth having a crest spaced from said central axis by a distance substantially equal to one-half said predetermined diameter, whereby an annular space, into which said resin components may flow, is provided between said leaf portion external surfaces and the wall of said drill hole.