The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fr...The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fracture under cyclic normal stress with diferent oscillation amplitudes.The experimental results show that the activations of fast slips always correlate with unloading of normal stress.Besides,the intensive normal stress oscillation can weaken the shear strength which is recoverable when the normal stress return to constant.The rupture patterns are quantifed by stress drop,slip length and slip velocity.With the efect of small oscillation amplitudes,the slip events show chaotic shapes,compared to the regular and predictable style under constant normal stress.When the amplitude is large enough,the big and small slip events emerge alternately,showing a compound slip style.Large amplitude of the cyclic normal stress also widens the interval diferences of the slip events.This work provides experimental supports for a convincible link between the dynamic stress disturbance and the slip behavior of rock fractures.展开更多
Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory...Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory friction testson saw-cut granite joint surfaces. The effects of load point velocity and normal stress disturbances were investigated. Based on laboratory observations, a one-dimensional Spring-Block model was developed to interpret thefrictional behavior. Under constant normal stress, the simulated fault (granite joint) exhibits a regular stick-slipphenomenon at different load point velocities with stable recurrence intervals and stress drop magnitudes.Under cyclic normal stress, when the load point velocity is slow, stick-slip events occur only after 4-5 cycles ofnormal stress loading. When the load point velocity is large, due to the rapid sliding of the joint interface, onenormal stress cycle can lead to 4-5 stick-slip events. We find that the cyclic normal stress weakens the joint shearstrength when the load point velocity is slow and improves the strength when the velocity is fast. There is acritical value of load point velocity for resonance where the stick-slip occurrence timespan is identical to thenormal stress cyclic period. This work sheds light on the frictional evolution of tectonic faults during the seismiccycles influenced by a complex stress state.展开更多
基金supported by Fundamental Research Funds for the Central Universities(22dfx06)Natural Science Foundation of Guangdong Province-Joint Program for Ofshore Wind Power(2022A1515240009).
文摘The frictional rupture mechanisms of rock discontinuities considering the dynamic load disturbance still remain unclear.This paper investigates the transitional behaviors of slip events happened on a planar granite fracture under cyclic normal stress with diferent oscillation amplitudes.The experimental results show that the activations of fast slips always correlate with unloading of normal stress.Besides,the intensive normal stress oscillation can weaken the shear strength which is recoverable when the normal stress return to constant.The rupture patterns are quantifed by stress drop,slip length and slip velocity.With the efect of small oscillation amplitudes,the slip events show chaotic shapes,compared to the regular and predictable style under constant normal stress.When the amplitude is large enough,the big and small slip events emerge alternately,showing a compound slip style.Large amplitude of the cyclic normal stress also widens the interval diferences of the slip events.This work provides experimental supports for a convincible link between the dynamic stress disturbance and the slip behavior of rock fractures.
基金funded by the National Natural Science Foundation of China(No.52474122)the Natural Science Foundation of Guangdong Province,China(No.2022A1515240009).
文摘Understanding the slip-style evolution of tectonic faults is important for exploring the earthquake mechanisms. Toreveal the fault slip characteristics under a complex stress state, we conducted a series of laboratory friction testson saw-cut granite joint surfaces. The effects of load point velocity and normal stress disturbances were investigated. Based on laboratory observations, a one-dimensional Spring-Block model was developed to interpret thefrictional behavior. Under constant normal stress, the simulated fault (granite joint) exhibits a regular stick-slipphenomenon at different load point velocities with stable recurrence intervals and stress drop magnitudes.Under cyclic normal stress, when the load point velocity is slow, stick-slip events occur only after 4-5 cycles ofnormal stress loading. When the load point velocity is large, due to the rapid sliding of the joint interface, onenormal stress cycle can lead to 4-5 stick-slip events. We find that the cyclic normal stress weakens the joint shearstrength when the load point velocity is slow and improves the strength when the velocity is fast. There is acritical value of load point velocity for resonance where the stick-slip occurrence timespan is identical to thenormal stress cyclic period. This work sheds light on the frictional evolution of tectonic faults during the seismiccycles influenced by a complex stress state.
