State-of-the-Art Intersection Support in Coal Mines in the USA

Spearing, A. C.; Mueller, Allen Robert

doi:10.36487/acg_repo/808_151

Cited by 4 publications

(4 citation statements)

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“…The SCC related rock bolt and cable-bolt failures in underground reinforcement system were first observed in the 1990s in the United Kingdom where the collapse of a roadway roof occurred [22,23]. SCC has also been identified as an issue in underground mines in China [24,25], Canada [26,27], Australia [15], and the USA [28,29]. However, only little research has been conducted to determine the long-term performance of cable bolts in underground conditions, particularly with regards to SCC.…”

Section: Introductionmentioning

confidence: 99%

“…However, only little research has been conducted to determine the long-term performance of cable bolts in underground conditions, particularly with regards to SCC. Spearing [28] conducted a series of laboratory tests to determine the effects of corrosion on the serviceability of cable bolts installed in underground coal mines in the USA. Different types of cable bolts including standard cable bolts, epoxy-coated cables, and galvanized cables were tested in a range of corrosive conditions with different pH and temperature.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory-Based Investigation into Stress Corrosion Cracking of Cable Bolts

Guo

Guang-bin

et al. 2019

Materials

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Cable-bolt failures due to stress corrosion cracking (SCC) could significantly compromise the sustainability and long-term stability of underground constructions. To fully understand the SCC of cable bolts, a two-step methodology was implemented: (i) long-term cable-bolt coupon tests using mineralogical materials collected from underground mines; and (ii) accelerated full-scale cable-bolt tests using an acidified solution. In the long-term tests, a novel three-point bending coupon was designed. The effects of mineralogical materials on SCC were evaluated under the simulated underground bolting conditions through the application of “corrosion cells”. For accelerated tests, SCC resistance of different type of cable bolts was examined using the new designed tensile-loading apparatus under the periodically increasing strain-rate loading mechanism. It was identified that mineralogical materials and applied stress intensity accelerated the corrosion process of the cable bolts. The number of wires and wire surface conditions in different types of cable bolt directly affected SCC susceptibility. The cable bolts with a greater number of wires provided higher resistance to SCC. The developed experimental methodologies can be applied to study SCC in other reinforcement materials and the results can be used to design optimal support systems in different environmental and geotechnical conditions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Laboratory-Based Investigation into Stress Corrosion Cracking of Cable Bolts

Guo

Guang-bin

et al. 2019

Materials

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“…Due to the large cross‐sectional area and high stress concentration, the potential for structural instability is high at intersections. According to ground fall statistics, over 30% of roof falls occur at excavation intersections, and the proportion exceeds 70% in mines where the room‐and‐pillar method is used . During the late 1980s, the U.S. Bureau of Mines specifically studied the stability and design of excavation intersections in shallow coal mines.…”

Section: Introductionmentioning

confidence: 99%

Fracturing behaviour of sandstone specimens with a cavity formed by intersecting excavations under compression: Experimental study and numerical modelling

Zhao

Kulatilake

et al. 2019

Strain

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To investigate the mechanical properties, damage characteristics, and fracturing behaviour of specimens with a cavity formed by intersecting excavations, a series of uniaxial compression tests were conducted incorporating digital image correlation (DIC) and acoustic emission (AE) techniques. PFC 2D modelling was conducted to further study the failure modes and crack evolution under biaxial loading. The results showed that the mechanical properties are significantly weakened by the cavity and influenced by its shape. The failure of the specimens containing a cavity under uniaxial compression can be considered as a progressive process of crack initiation, propagation, and coalescence of different cracks with each other, leading to forming macrofractures, which can be visually displayed by the DIC technique. A new method for determining the crack closure stress is proposed, and the crack initiation stress and the crack damage stress of specimens are also obtained by the AE measurements. The failure mode of the intact specimen changed from the tensileshear failure mode under the uniaxial compression to the shear-dominated failure mode under the biaxial compression. Failure of the specimens with a cavity is dominated by shear cracks rather than tensile cracks. Under high confining stresses, almost no macrotensile cracks appeared on the roof or floor of the cavity; instead, several spalling fractures were visible on the two sides of the cavity. The fracturing mechanism is well explained by the evolution of the internal stresses in the specimens.

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“…The rate of steel bolt corrosion is influenced by ground water composition, flowrates, water pH, temperature, CO 2 content, surface condition, presence of corrosion inhibitors, applied stresses, residual stresses (from workings, forming or welding operations) and any hydrogen sulphide concentrations (Henthorne, 1971(Henthorne, -1972Spearing et al, 2010). Accordingly, a specialised test rig was constructed at the University of Wollongong to study the effect of long term exposure on full size bolts, which are of current use in Australian mines.…”

Section: Introductionmentioning

confidence: 99%

Rock bolt corrosion – an experimental study

Aziz

Craig²,

Nemcik

et al. 2014

Mining Technology

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The effect of long term exposure of full size bolts to corrosive environments is presented. A special test rig was used to test four bolts under different loading conditions. Four, X-grade identical profile bolts, each of 21.7 mm core diameter (23.7 mm full diameter) were subjected to prolong corrosion testing using acid sulphate water. The pH value of the circulated water varied between 3.4 and 4.3. The corrosion exposure test period lasted three and half years. Two bolts were axially loaded to 10 and 20 t force respectively, the third bolt was subjected to a 360 Nm torsion load and the fourth bolt was left unstressed to act as a reference bolt. After the test period ended, the bolts were stripped of their corroded coatings and weighted for weight loss. The diameter of each bolt was subsequently measured, and the loaded bolt samples were first tested non-destructively for tensile cracks and then tested for tensile failure. No cracks were found on post corrosion bolts tested non-destructively. The failure strength reduction on all four post-corroded bolts was significant, varying between 21% and 39%. The onset of corrosion was not confined to the targeted mid-section length of the bolt, however, the severest corrosion occurred at the anchored ends of the bolts.

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State-of-the-Art Intersection Support in Coal Mines in the USA

Cited by 4 publications

References 0 publications

Laboratory-Based Investigation into Stress Corrosion Cracking of Cable Bolts

Laboratory-Based Investigation into Stress Corrosion Cracking of Cable Bolts

Fracturing behaviour of sandstone specimens with a cavity formed by intersecting excavations under compression: Experimental study and numerical modelling

Rock bolt corrosion – an experimental study

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