Rockburst is a complex mining-induced phenomenon that remains difficult to be quantified.In particular,geological conditions contributing to rockbursts are more variable than those in many conventional engineering app...Rockburst is a complex mining-induced phenomenon that remains difficult to be quantified.In particular,geological conditions contributing to rockbursts are more variable than those in many conventional engineering approaches.Faults,intact rock properties,and other rock mass conditions vary,sometimes,within small distance.Stress levels that store energy or drive structures can change with geological complications.For example,faults may channel stress between the void and the discontinuity,and/or alter the local stress direction.High-strength rock masses may be very massive at shallow depth,allowing for large/stable excavations.The same rock type may store excessive strain energy at depth or high mineral extraction,and lead to rockbursts.More robust ground support systems that can bear dynamic loading are now commonplace in mining industry.A typical approach would be able to evaluate rockburst potential,and selectively deploy more robust ground support systems.Rockburst resistant support is more expensive in installation than most support systems designed for gravity loading.Thus,an excessively conservative risk assessment can affect both direct support costs and productivity.As mines continue to go deeper,selective use of burst-prone support may not be an optimal choice,and pervasive installation may become necessary.This implies a need to maintain a reasonable installation speed,and the time to get to deep orebodies is a major economic factor.This paper shows field examples of rockbursts to highlight some of the complex issues related to the rockburst.A multi-tiered risk mitigation approach is used for rockburst conditions.Examples of risk reduction strategies are given and some examples from a deep hard rock mine are used to illustrate the relative success of the strategies.Given that some residual risks to worker safety remain,discussion is presented on where more research or process improvements would be beneficial.展开更多
Strainburst is the most frequently encountered type of rockburst in underground mines.Strainburst occurs when the stress near the excavation boundary reaches the peak strength of the rock mass causing it to fail sudde...Strainburst is the most frequently encountered type of rockburst in underground mines.Strainburst occurs when the stress near the excavation boundary reaches the peak strength of the rock mass causing it to fail suddenly and violently.To mitigate strainburst damage risk,effective rock support is needed.In strainburst-prone grounds,it is critical to have rock support components to fulfill the role of rock reinforcement first to prevent rock failure.On the other hand,well-retained and reinforced rock masses may be excessively deformed and fail violently.In such a case,yielding elements are needed in the rock support system to absorb the excess strain energy released due to rock failure.The conventional method to support strainburst-prone grounds is to install rock reinforcement system using rebar and mesh first and then install yielding support system using dynamic rockbolts at a later stage.This two-stage rock support installation process is not effective because it can adversely impact mine production schedule.This paper presents a new,patented dynamic rockbolt,which is called superbolt and is developed for rock support in burst-prone grounds.Laboratory testing confirmed that the superbolt has superb capacity to achieve the goal of reinforcing and holding rock masses.The superbolt is characterized by high dynamic energy absorption capacity,consistent performance,and the ability to withstand repeated dynamic loading.The new rockbolt can be used in a one-pass rock support system to facilitate rapid drift development in underground mines and increase mine safety and productivity.展开更多
文摘Rockburst is a complex mining-induced phenomenon that remains difficult to be quantified.In particular,geological conditions contributing to rockbursts are more variable than those in many conventional engineering approaches.Faults,intact rock properties,and other rock mass conditions vary,sometimes,within small distance.Stress levels that store energy or drive structures can change with geological complications.For example,faults may channel stress between the void and the discontinuity,and/or alter the local stress direction.High-strength rock masses may be very massive at shallow depth,allowing for large/stable excavations.The same rock type may store excessive strain energy at depth or high mineral extraction,and lead to rockbursts.More robust ground support systems that can bear dynamic loading are now commonplace in mining industry.A typical approach would be able to evaluate rockburst potential,and selectively deploy more robust ground support systems.Rockburst resistant support is more expensive in installation than most support systems designed for gravity loading.Thus,an excessively conservative risk assessment can affect both direct support costs and productivity.As mines continue to go deeper,selective use of burst-prone support may not be an optimal choice,and pervasive installation may become necessary.This implies a need to maintain a reasonable installation speed,and the time to get to deep orebodies is a major economic factor.This paper shows field examples of rockbursts to highlight some of the complex issues related to the rockburst.A multi-tiered risk mitigation approach is used for rockburst conditions.Examples of risk reduction strategies are given and some examples from a deep hard rock mine are used to illustrate the relative success of the strategies.Given that some residual risks to worker safety remain,discussion is presented on where more research or process improvements would be beneficial.
基金financial support from NSERC(No.CRDPJ 461108-13)Mansour Mining Technologies Inc.(MMTI)
文摘Strainburst is the most frequently encountered type of rockburst in underground mines.Strainburst occurs when the stress near the excavation boundary reaches the peak strength of the rock mass causing it to fail suddenly and violently.To mitigate strainburst damage risk,effective rock support is needed.In strainburst-prone grounds,it is critical to have rock support components to fulfill the role of rock reinforcement first to prevent rock failure.On the other hand,well-retained and reinforced rock masses may be excessively deformed and fail violently.In such a case,yielding elements are needed in the rock support system to absorb the excess strain energy released due to rock failure.The conventional method to support strainburst-prone grounds is to install rock reinforcement system using rebar and mesh first and then install yielding support system using dynamic rockbolts at a later stage.This two-stage rock support installation process is not effective because it can adversely impact mine production schedule.This paper presents a new,patented dynamic rockbolt,which is called superbolt and is developed for rock support in burst-prone grounds.Laboratory testing confirmed that the superbolt has superb capacity to achieve the goal of reinforcing and holding rock masses.The superbolt is characterized by high dynamic energy absorption capacity,consistent performance,and the ability to withstand repeated dynamic loading.The new rockbolt can be used in a one-pass rock support system to facilitate rapid drift development in underground mines and increase mine safety and productivity.
