The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering...The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering mechanisms,i.e.strain burst and fault-slip burst.Strain burst occurs on rock surfaces when the tangential stress exceeds the rock strength in hard and brittle rocks.Fault-slip burst is triggered by fault-slip induced seismicity.Topic 2 is prediction and forecasting of rockburst events.Prediction for a rockburst event must tell the location,timing and magnitude of the event.Forecasting could simply foresee the probability of some of the three parameters.It is extremely challenging to predict rockbursts and large seismic events with current knowledge and technologies,but forecasting is possible,for example the possible locations of strain burst in an underground opening.At present,the approach using seismic monitoring and numerical modelling is a promising forecasting method.Topic 3 is preconditioning methods.The current preconditioning methods are blasting,relief-hole drilling and hydrofracturing.Defusing fault-slip seismicity is difficult and challenging but has been achieved.In very deep locations(>3000 m),the fracturing could extend from the excavation face to a deep location ahead of the face and therefore preconditioning is usually not required.Topic 4 is dynamic ground support against rockburst.Dynamic ground support requires that the support system be strong enough to sustain the momentum of the ejecting rock on one hand and tough enough on the other hand to absorb the strain and seismic energies released from the rock mass.The current dynamic support systems in underground mining are composed of yielding tendons and flexible surface retaining elements like mesh/screen and straps.Yielding props and engineered timber props are also used for dynamic support.展开更多
This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In additio...This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In addition,the long-term deterioration of a series of ore/waste passes that were excavated with the bottom-up Alimak methodology is investigated.These excavations were completed at depths between 1200 and 1915 m below the surface in a hard rock mine in Sudbury,Ontario,Canada.The ability to see a cross-section of fracturing around the bored raises while slashing into them and observing the progressive growth of fractures was critical for understanding the factors leading to deterioration.The Alimak-driven ore/waste passes were in an advanced state of deterioration,which provided a late-stage notch growth profile that could be compared with the notch growth observed in the bored raises.The methods used to support and stabilize these excavations are detailed;in addition,methodologies to prevent some of the deterioration from occurring are also presented.The findings of this work are useful for understanding the mechanisms driving brittle rock failure in deep mining and subsequently for minimizing or preventing the deterioration from occurring.展开更多
文摘The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering mechanisms,i.e.strain burst and fault-slip burst.Strain burst occurs on rock surfaces when the tangential stress exceeds the rock strength in hard and brittle rocks.Fault-slip burst is triggered by fault-slip induced seismicity.Topic 2 is prediction and forecasting of rockburst events.Prediction for a rockburst event must tell the location,timing and magnitude of the event.Forecasting could simply foresee the probability of some of the three parameters.It is extremely challenging to predict rockbursts and large seismic events with current knowledge and technologies,but forecasting is possible,for example the possible locations of strain burst in an underground opening.At present,the approach using seismic monitoring and numerical modelling is a promising forecasting method.Topic 3 is preconditioning methods.The current preconditioning methods are blasting,relief-hole drilling and hydrofracturing.Defusing fault-slip seismicity is difficult and challenging but has been achieved.In very deep locations(>3000 m),the fracturing could extend from the excavation face to a deep location ahead of the face and therefore preconditioning is usually not required.Topic 4 is dynamic ground support against rockburst.Dynamic ground support requires that the support system be strong enough to sustain the momentum of the ejecting rock on one hand and tough enough on the other hand to absorb the strain and seismic energies released from the rock mass.The current dynamic support systems in underground mining are composed of yielding tendons and flexible surface retaining elements like mesh/screen and straps.Yielding props and engineered timber props are also used for dynamic support.
文摘This paper presents details of the early to mid-stage deterioration in the form of notch growth of two 3 m diameter bored raises that were excavated and slashed to 7.8 m to serve as an internal shaft(winze).In addition,the long-term deterioration of a series of ore/waste passes that were excavated with the bottom-up Alimak methodology is investigated.These excavations were completed at depths between 1200 and 1915 m below the surface in a hard rock mine in Sudbury,Ontario,Canada.The ability to see a cross-section of fracturing around the bored raises while slashing into them and observing the progressive growth of fractures was critical for understanding the factors leading to deterioration.The Alimak-driven ore/waste passes were in an advanced state of deterioration,which provided a late-stage notch growth profile that could be compared with the notch growth observed in the bored raises.The methods used to support and stabilize these excavations are detailed;in addition,methodologies to prevent some of the deterioration from occurring are also presented.The findings of this work are useful for understanding the mechanisms driving brittle rock failure in deep mining and subsequently for minimizing or preventing the deterioration from occurring.