Examination of rockbolt stress corrosion cracking utilising full size rockbolts in a controlled mine environment

Previous studies had identified that a testing protocol was required to examine stress corrosion cracking (SCC) of full sized rockbolts under simulated in situ conditions. As a result, a load frame capable of inducing both tensile and bending loads on a rockbolt specimen, erected within a controlled mine environment (CME) laboratory was constructed. The newly designed and purpose built Bend and Tension Loading Apparatus (BaTLA) was used to conduct both static and slow strain rate (SSR) tests on rockbolt specimens in an acidified sodium chloride solution containing hydrogen sulphide in the CME. It was found that SSR testing provided an appropriate analogue for examining rockbolt susceptibility to SCC and was thus used to examine the effect of grit blasting, galvanising and varying steel grades on the SCC resilience of rockbolts. Of these, 300 grade steel and galvanising provided the most promising resistance to SSC, while grit blasting provided a 40% improvement in resistance compared to untreated HSAC 840 grade rockbolts.