Metallurgical examination of rockbolts failed in service due to stress corrosion cracking

Elias, Elias; Vandermaat, Damon; Craig, Peter; Chen, Huichao; Crosky, A.; Saydam, Serkan; Hagan, Paul; Hebblewhite, Bruce

doi:10.36487/acg_rep/1304_32_elias

Cited by 12 publications

(13 citation statements)

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“…The location of the failures relative to the end fittings was determined. Bolts T1, T3 0-2060 Dissolved oxygen (mg l -1 ) 7-10 chloride (mg l -1 ) 20-28 Total Alkalinity as caco 3 (mg l -1 ) 550-1840 carbonate (mg l -1 ) 0-70 Bicarbonate (mg l -1 ) 515-2200 for failures in the shank (Shutter et al 2001;Elias et al 2013).…”

Section: Location Of Fracturementioning

confidence: 99%

“…Final catastrophic failure of rockbolts occurs by fast fracture once the stress corrosion crack reaches a critical crack length, which is determined by the magnitude of the stress and the fracture toughness of the steel (Erdogan 2000;Shutter et al 2001). Failure of the rockbolt occurs transverse to the bolt axis and is brittle in appearance (Shutter et al 2001;Elias et al 2013).…”

Section: Introductionmentioning

confidence: 99%

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Failure of the threaded region of rockbolts in underground coal mines

et al. 2018

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HSAC 840 steel rockbolts were examined, all of which had failed in service through the threaded region exterior to the rock face by brittle fracture transverse to the bolt axis. The bolts had been in service in an Australian coal mine in which the groundwater had a pH of 7•5-8•5 and a relatively high bicarbonate level of 515-2200 mg l −1 . All failures had occurred within the region comprising the domed washer and the end plate. The majority of the bolts showed a small thumbnail-shaped discoloured region 1.5-4.5 mm in length at the fracture origin, as is characteristic of stress corrosion cracking (SCC) in rockbolts. In half of these bolts, SCC had initiated immediately at the root of the thread, but in the other half of the bolts, SCC had initiated from a small pre-existing crack that had been produced in the thread as a result of a prior bending load.

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Section: Location Of Fracturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Failure of the threaded region of rockbolts in underground coal mines

et al. 2018

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“…The purpose of the roof support systems is to control the ground for a safe and reliable opening over the design period. Corrosion of these roof control products and ancillaries is a problem to the mine ground control (Shutter et al 2001;Elias et al 2013;Kang et al 2013;Chen et al 2018;Craig 2018;Aritan and Can 2019;Guo et al 2019). Although there are various forms of corrosion mechanisms, the metallic corrosion mechanisms that occur to the roof support systems in an underground mining environment are uniform, crevice, pitting and stress corrosion.…”

Section: Introductionmentioning

confidence: 99%

Stress corrosion testing of roof bolt grade 60 steel in simulated underground coal mine atmosphere

et al. 2019

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Corrosion of roof bolts in underground mine environments could have an adverse impact on ground control, which is directly related to workforce safety. Past studies state that stress corrosion cracking (SCC) of roof bolts is a significant problem in underground coal mines, resulting in premature bolt failures. However, it has not been seriously studied in U.S. underground coal mines. As a preliminary study, the most common roof bolt material used in U.S. mines, ASTM A 615 Grade 60 steel, was studied under stress corrosion conditions. ASTM G30 standard was applied to achieve this and tested in the simulated coal mine conditions. SCC was observed on samples that were tested for 180 days. Chloride SCC (ClSCC) was found to be the corrosion mechanism resulting in cracks from the EDS data. This paper mainly discusses the test protocol, shortcomings of this preliminary testing and makes recommendations based on the observations and results.

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“…As modern mining environments become increasingly deep, the accompanying underground stresses also increase, thus requiring traditional ground support techniques and materials to adapt. In response to these challenges, increasingly higher strength grades of steel have been used to meet the increasingly demanding requirements placed on rockbolts in underground mines (Elias et al 2013). However, the benefits of these higher-quality support elements have often been negated in highly corrosive mining environments.…”

Section: Introductionmentioning

confidence: 99%