ABSTRACT
In general Swellex bolts strengthen the rock mass through a combination of friction and mechanical interlock at the rock-bolt interface. The anchoring mechanism of the Swellex bolt is actually different in hard and soft rocks. In hard rock, the secondary contact stress, induced by the mechanical interlock of the asperities at the borehole wall, plays a major role in the anchoring, whereas the primary contact stress, created by the bolt expansion does not contribute much. However, in soft rocks, it is the friction, and thus the primary contact stress, which determines the anchoring capacity of the bolt.
