An acoustic emission(AE)location experiment was performed on sandstone using an advanced AE test system.The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE.The results show t...An acoustic emission(AE)location experiment was performed on sandstone using an advanced AE test system.The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE.The results show that AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase;at the beginning of cyclic loading with low duration time and energy,AE events came from a small crack.The location result showed that most events occurred in the core zone forming at the static loading process,and the location points changed slowly.AE energy changed little during the metaphase of cyclic process.There was a modest increase of location points in every cycle.The tendency of steady development could be predicted from the AE location events.At the end of each cyclic loading,the quantity of AE events and energy increased quite rapidly,reaching a maximum at the last cycle.AE events had high energy and duration time.Location events changed quite rapidly and assembled and linked continuously in the core zone.At the same time,they expanded to the top of specimen.A macroscopic crack finally formed.In the postfailure process,some AE events still existed due to fracturing of gliding friction.Owing to the inner stress balance of rock even after loading stopped,minor AE events still occurred.展开更多
Rock failure phenomena,such as rockburst,slabbing(or spalling) and zonal disintegration,related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining.Currently,the...Rock failure phenomena,such as rockburst,slabbing(or spalling) and zonal disintegration,related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining.Currently,the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward.In this study,new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced.Two types of coupled loading modes,i.e.'critical static stress + slight disturbance' and 'elastic static stress + impact disturbance',are proposed,and associated test devices are developed.Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory,and the rockburst mechanism and related criteria are demonstrated.The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold,and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion.Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density.In addition,we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass,which can efficiently and accurately locate the rock failure in hard rock mines.Also,a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.展开更多
文摘An acoustic emission(AE)location experiment was performed on sandstone using an advanced AE test system.The space-time evolution rule regarding damage was analyzed under cyclic loading as well as AE.The results show that AE on static loading process is consistent with the damage evolution rule of compression and the elastic-plastic deformation phase;at the beginning of cyclic loading with low duration time and energy,AE events came from a small crack.The location result showed that most events occurred in the core zone forming at the static loading process,and the location points changed slowly.AE energy changed little during the metaphase of cyclic process.There was a modest increase of location points in every cycle.The tendency of steady development could be predicted from the AE location events.At the end of each cyclic loading,the quantity of AE events and energy increased quite rapidly,reaching a maximum at the last cycle.AE events had high energy and duration time.Location events changed quite rapidly and assembled and linked continuously in the core zone.At the same time,they expanded to the top of specimen.A macroscopic crack finally formed.In the postfailure process,some AE events still existed due to fracturing of gliding friction.Owing to the inner stress balance of rock even after loading stopped,minor AE events still occurred.
基金jointly supported by the State Key Research Development Program of China (Grant No.2016YFC0600706)the National Natural Science Foundation of China (Grant Nos.41630642 and 11472311)
文摘Rock failure phenomena,such as rockburst,slabbing(or spalling) and zonal disintegration,related to deep underground excavation of hard rocks are frequently reported and pose a great threat to deep mining.Currently,the explanation for these failure phenomena using existing dynamic or static rock mechanics theory is not straightforward.In this study,new theory and testing method for deep underground rock mass under coupled static-dynamic loading are introduced.Two types of coupled loading modes,i.e.'critical static stress + slight disturbance' and 'elastic static stress + impact disturbance',are proposed,and associated test devices are developed.Rockburst phenomena of hard rocks under coupled static-dynamic loading are successfully reproduced in the laboratory,and the rockburst mechanism and related criteria are demonstrated.The results of true triaxial unloading compression tests on granite and red sandstone indicate that the unloading can induce slabbing when the confining pressure exceeds a certain threshold,and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion.Numerical results indicate that the rock unloading failure response under different in situ stresses and unloading rates can be characterized by an equivalent strain energy density.In addition,we present a new microseismic source location method without premeasuring the sound wave velocity in rock mass,which can efficiently and accurately locate the rock failure in hard rock mines.Also,a new idea for deep hard rock mining using a non-explosive continuous mining method is briefly introduced.
