Rockfalls or rockslides are common in areas where highly fractured rocks are exposed on steep slopes and where weakness are inclined in the same direction as the slopes. To minimize the potential for rockfalls or small-scale rockslides, rock bolts are commonly used to anchor loose rocks to more massive, solid bodies of rock (Figure). Installation requires that a hole first be drilled to some desired depth, after which a bolt is inserted and held in place by one of several different techniques.
The most common anchoring technique is to use a tip that expands when the bolt is turned, forming a wedge that keeps the entire assemblage from backing out of the hole. Other types of rock bolts make use of cement grout or simple friction within the borehole to keep the bolts fixed in place. Rock bolts are used extensively along highways and rail lines where fractured rocks create a near constant threat of rockfalls. Bolts are also widely used for stabilizing walls and ceilings in tunnels and underground mines.