Abstract: A rock bolt (10) comprising first and second elongate members (11, 12) is disclosed. The first elongate member comprises a first end (13) adapted to penetrate rock, and a second end (14) adapted to provide attachment for actuating means. The first elongate member is disposed at least partially, longitudinally inside the second elongate member. The second elongate member can be adapted for transverse expansion along at least a portion of its length in order to anchor the rock bolt into position. A cavity can be formed between the first and second elongate members extending between the first and second ends of the first elongate member. Methods of drilling with rock bolts according to the invention are also disclosed.