Mineralogically influenced stress corrosion cracking of rockbolts and cable bolts in underground mines

Abstract

Stress corrosion cracking (SCC) of rockbolts and cable bolts in underground mines has been identified as a serious international problem over the past two decades. The frequent occurrence of rockbolt and cable bolt SCC in strata containing clay and groundwater suggests the presence of certain mineral types may be an influencing factor. To identify the environmental factors leading to SCC and evaluate the effects of mineralogically influenced corrosion, a laboratory testing program capable of recreating the underground bolting environments was designed and conducted. A static load was applied to specimens of rockbolts and cable bolts placed in “corrosion cells” containing groundwater, clay, coal or a combination of those materials for about 300 days. Results from these tests revealed that the mineralogical materials indirectly affected the rate of corrosion by significantly altering the local water chemistry. The mechanical load applied to the specimens was found to accelerate the rate of corrosion, and corrosion pits were observed to have formed on the steel surfaces. The generation of corrosion pits would likely result in local stress concentration and contribute to SCC. The results of this study provide further insights into the environmental factors leading to SCC and the proposed methodologies can be used for investigating this type of failure through in-situ experiments.