The incidence of Stress Corrosion Cracking (SCC) in rock bolts
has not been quantified and its magnitude has not been
addressed. A laboratory test has been achieved that causes a
tensile sample to fail in a manner similar to the failure mode
observed from service failures, namely slow SCC followed by fast
brittle fracture. The laboratory tests involve subjecting a
tensile sample to a linearly increasing stress at a slowly
applied stress rate whilst the specimen in exposed to a dilute
sulphate solution of pH 2.1. Detailed fractography of SCC
fracture features from the LT has shown that these fracture
surfaces have the same features as fracture surfaces of service
failures. An SCC velocity can be calculated from these tests.
This SCC velocity can be used to evaluate the benefit provided
by a material with a higher fracture toughness. The SCC velocity
measured from the laboratory tests indicates that the SCC
lifetime is increased only marginally by the use of a rock bolt
materials with a higher fracture toughnes