| The landslide has become a mountain road traffic,mining,hydropower and other areas of a major security risks.The occurrence of the landslide does not occur in the instantaneous period,but after a period of instability of the accumulation of factors,during which began to produce micro-cracks,While microscopic damage is accompanied by a weak elastic wave of the launch,which makes it possible to capture the early acoustic emission signal of slope failure.In this paper,the acoustic emission combined with the waveguide is used to monitor the slip surface of the slope.The waveguide and the coupling material in the slope monitoring hole are simulated by the cement mortar pouring waveguide.Using the combination of experimental study,theoretical analysis and numerical analysis,the following conclusions are obtained:(1)The crack type of the specimen under three-point bending Test is mainly: the crack is irregularly expanded from the bottom to the bottom;the crack of the specimen in the shear test develops mainly along two shear surfaces,few specimens show "splayed".(2)Before the shear failure occurs,when the acoustic emission event rate suddenly increases and then plummeted,it indicates that the coupling material is in the elastic stage at this time,and no crack is appeared.It can be used as a criterion for predicting the possible damage.Before the three-point bending failure,acoustic emission rate increases rapidly and do not decline,then the specimen do not produce cracks,and then the rate of acoustic emission event is high and low which can be used to predict the slope failure.The variation law of energy and ringing count rate in the process of shear and three point bending failure is similar to that of the corresponding event rate.(3)The amplitude,ringing count and energy sequence of the acoustic emission of the cement mortar casting waveguide specimen have fractal feature in the time domain.The acoustic emission energy of the three-point bending Test does not have obvious fractal characteristics in the time domain,While the acoustic emission amplitude and ringing count have fractal characteristics.Through the analysis of correlation dimension of the acoustic emission amplitude,ringing count and energy of the shear test and the three-point bending test,it is concluded that the correlation dimension rule in the shear failure process of the specimen has its own different places.In general,the increase of the correlation dimension can be used as the basis for the crack initiation.(4)The ΣN / ΣE value of the acoustic emission decreases with the steady loading stage of the shear failure of the specimen,and then increases slowly after entering the elastic stage.In the threepoint bending failure experiment,the ΣN / ΣE value of the acoustic emission decrease in elastic stage suddenly,and then gently change.However,the decrease of the ΣN / ΣE value of the acoustic emission can be used as the basis for the shear or bending failure of the specimen.(5)The definition of microcrack in PFC2 D is introduced.Through the observation of numerical simulation,the failure mode of cement mortar pouring waveguide is described.At the beginning of loading,the bond between the particles is broken,so there are fewer damage cracks,and then the load increases,the micro-cracks gradually expand,which lead to the increasing number of micro-cracks.Ultimately in the model to form a continuous penetration of macroscopic cracks,Which is consistent with the law of the crack propagation during the test. |
