The service failure of rock bolts and cable bolts are frequently reported issues in underground coal mines. Whilst numerous experimental investigations concerned with the service failure of bolts have been conducted, ...The service failure of rock bolts and cable bolts are frequently reported issues in underground coal mines. Whilst numerous experimental investigations concerned with the service failure of bolts have been conducted, numerical modelling offers an alternative approach in evaluating the factors contributing to service failures of bolts in underground mines. In this study, analysis of the influence of groundwater and tensile stress on bolts in underground coal mines was studied through the numerical modelling of a grouted bolt in the immediate roadway roof. Bolt tensile stress and groundwater dripping rates in the immediate roadway roof were analysed using a package based on finite element method to assess the effect of coal roof thickness and claystone bands, as main contributors of known service failures of bolts in roadways of underground coal mines. Increasing coal roof thickness was found to increase bolt dripping rates. Probable location of stress corrosion cracking (SCC) occurrence was established through examining the shift and increase in maximum bolt tensile stress that was exhibited along the bolt length with increasing coal roof thickness. Claystone bands situated at the top and centre horizon of a grouted bolt produced lower bolt dripping rates compared with scenarios with no claystone bands. Intersecting claystone bands at the centre horizon of a bolt for a fully grouted bolt could increase the likelihood of SCC corrosion and bolt failure by contributing to microbial corrosion processes and grout fracturing by tensile stress. This study improves the understanding the bolt failure associated with the presence of groundwater and changing stress environments, which in turn is imperative in formulating strategies to mitigate support element failures and improve the ground support viability.展开更多
Anchor bolts are commonly used throughout underground mining and tunnelling operations to improve roof stability.However,premature failures of anchor bolts are significant safety risks in underground excavations aroun...Anchor bolts are commonly used throughout underground mining and tunnelling operations to improve roof stability.However,premature failures of anchor bolts are significant safety risks in underground excavations around the world due to susceptible bolt materials,a moist and corrosive environment and tensile stress.In this paper,laboratory experiments and hydrogeochemical models were combined to investigate anchor bolt corrosion and failure associated with aqueous environments in underground coal mines.Experimental data and collated mine water chemistry data were used to simulate bolt corrosion reactions with groundwater and rock materials with the PHREEQC code.A series of models quantified reactions involving iron and carbon under aerobic and anaerobic conditions in comparison with ion,pH and pE trends in experimental data.The models showed that corrosion processes are inhibited by some natural environmental factors,because dissolved oxygen would cause more iron from the bolts to oxidize into solution.These interdisciplinary insights into corrosion failure of underground anchor bolts confirm that environmental factors are important contributors to stress corrosion cracking.展开更多
文摘The service failure of rock bolts and cable bolts are frequently reported issues in underground coal mines. Whilst numerous experimental investigations concerned with the service failure of bolts have been conducted, numerical modelling offers an alternative approach in evaluating the factors contributing to service failures of bolts in underground mines. In this study, analysis of the influence of groundwater and tensile stress on bolts in underground coal mines was studied through the numerical modelling of a grouted bolt in the immediate roadway roof. Bolt tensile stress and groundwater dripping rates in the immediate roadway roof were analysed using a package based on finite element method to assess the effect of coal roof thickness and claystone bands, as main contributors of known service failures of bolts in roadways of underground coal mines. Increasing coal roof thickness was found to increase bolt dripping rates. Probable location of stress corrosion cracking (SCC) occurrence was established through examining the shift and increase in maximum bolt tensile stress that was exhibited along the bolt length with increasing coal roof thickness. Claystone bands situated at the top and centre horizon of a grouted bolt produced lower bolt dripping rates compared with scenarios with no claystone bands. Intersecting claystone bands at the centre horizon of a bolt for a fully grouted bolt could increase the likelihood of SCC corrosion and bolt failure by contributing to microbial corrosion processes and grout fracturing by tensile stress. This study improves the understanding the bolt failure associated with the presence of groundwater and changing stress environments, which in turn is imperative in formulating strategies to mitigate support element failures and improve the ground support viability.
基金Project(140100153)supported by Australian Research Council Linkage Grant。
文摘Anchor bolts are commonly used throughout underground mining and tunnelling operations to improve roof stability.However,premature failures of anchor bolts are significant safety risks in underground excavations around the world due to susceptible bolt materials,a moist and corrosive environment and tensile stress.In this paper,laboratory experiments and hydrogeochemical models were combined to investigate anchor bolt corrosion and failure associated with aqueous environments in underground coal mines.Experimental data and collated mine water chemistry data were used to simulate bolt corrosion reactions with groundwater and rock materials with the PHREEQC code.A series of models quantified reactions involving iron and carbon under aerobic and anaerobic conditions in comparison with ion,pH and pE trends in experimental data.The models showed that corrosion processes are inhibited by some natural environmental factors,because dissolved oxygen would cause more iron from the bolts to oxidize into solution.These interdisciplinary insights into corrosion failure of underground anchor bolts confirm that environmental factors are important contributors to stress corrosion cracking.
