ABSTRACT
Efficient dynamic bolt reinforcement is crucial in deep level gold mining prone to rockbursts. Deep level gold mining in South Africa is approaching 4000 m so appropriate support designs need to be implemented to manage ground stability challenges associated with these new depths. In order to extract the ore body, both novel mining methods and massive mining techniques have to be applied. Currently massive mining techniques are applied wherein destressing is imperative. Destressing is accomplished by cutting a series of overlapping, 5 m high horizontal slots across the reef. Although the minor span of each slot is about 100 m, stresses are extremely high due to presence of abutments. In order to protect workers from the effects of small seismic events, a yielding support system consisting of weldmesh (100 mm apertures and 5 mm strands) and 2.5 m long, Garford hybrid bolt have been developed. The support system allows installation to be made at 0.5 m from the advancing face without significant damage by the blast. A tendon pretension of 49.3 kN ensures an active support system at installation, with 29 kJ/m2 energy absorption capacity during seismic events, and static tensile capacity of 147 kN. The effectiveness of Garford hybrid bolt is discussed in this paper.
