Experimental Study On Acoustic Emission Response Of Loose Dam Failure

China is a natural disaster frequent countries,after the "5.12" earthquake there are many geological disasters caused by loose dam,about half of the dangerous in a large loose dam.When the case of heavy rainfall and other conditions,the dam water level rise rapidly,at any time may be broken,and the damage caused by continuous dam break in series is greater.under this background,the paper firstly analyzes the model of dam burst and the continuous effect of the magnification.Followed by the selection of seven disk for the study of indoor physical simulation test,with acoustic emission,microseismic,high-speed cameras and pore pressure and other instruments,the vibration signal,the vibration signal,the pore pressure signal and the energy change generated during the process of failure are discussed.Finally,the indoor physical simulation test is carried out on the continuous failure of the dam,qualitatively validated the series dam failure to release the scale of amplification effect.Where the barrier dam outburst vibration during recording by microseismic sensor,recording the vibration acceleration change history.However,it is troublesome to understand the process of vibration by time domain waves.The HHT transform contains EMD decomposition and Hilbert transform.HHT is a new method for analyzing nonlinear and nonstationary signals.The spectrum is obtained by this transformation,and then analyzed in the frequency domain,and the distribution of time-frequency energy in the vibration can be clearly described by the transformation.Through the pore water pressure agent and video to analyze the effective stress changes in the soil during the process of dam damage.Acoustic emission measured by the instrument damming energy under different working conditions dam outburst generated acoustic emissions data from the main ring count,energy,amplitude,energy accumulated analyzed four aspects.The ringing count can show the activity of the acoustic emission,the greater the amplitude,the greater the density,the stronger the acoustic emission activity.Amplitude is also called amplitude,the index is not affected by the threshold,directly determine the measurable sound emission,indirect performance of the intensity of the acoustic emission signal and a certain time of a certain event.The energy reflects the relative energy or relative intensity of the event,mainly for comparison under different conditions.Cumulative energy refers to the sum of the energy generated during the entire dam damage,and the curvature of the cumulative curve can also reflect a specific event for a certain period of time.It is a relative indicator.we obtained the following results and understanding:(1)In loose dam break,slurry permeabtion,fine particle migration and the dam collapse will caused acoustic emission.Acoustic emission signal amplitude,ring count and cumulative energy is closely related to the content of fine particles and the bulk density of slurry.(2)In the condtions of different fines content and different slurry bulk density,dam burst mode mostly overtopping failure,but few fine content loose dam due to the hydrostatic pressure effect of landslide failure may occur.During the process of the collapse of the dam,the dam's back slope first formed a number of small gullies.As the erosion intensified,the soil collapses on both sides of the gullies to form larger gullies and fissures.The erosion of the dam foot to form a pit,breach under the cut and erosion will make the dam side of a larger rectangular collapse tank.Then the dam water lavel drops rapidly and final damage.(3)The permeability of the slurry in the dam and the failure progress of the dam are affected the change of the pore pressure.The change of pore pressure in the dam is divided into three cases: one is the pore pressure in a period of time continued to increase,with the dam to break the pore pressure dissipation;the other is the pore pressure increase is not obvious or the amplitude of increase is very small,the pore pressure in the dam instantaneous increase with the dam destroyed and then dissipated;the last one is the pore pressure continued to grow for a time,instantaneous increase with the dam destroyed and then dissipated.The fine particle content of the dam and the bulk density of the slurry affect the permeability of the slurry in the soil of the dam.The location of the ditch,the fissure and the flushing affects the infiltration path of the slurry in the dam,thus affecting the pore pressure.(4)With the help of microseismic sensors and acoustic emission sensors,the energy generated by the dams break under different fines content and different slurry bulk densities is considered.arrival at a conclusion that the time of collapse,the formation and expansion of fissures and the collapse in the process of dam break affecting the size of the energy.The change point of curvature in energy curve corresponding the formation and expansion of the fissures and the collapse of dam.(5)Through the indoor physical simulation test of continuous dam break,it is concluded that the energy generated by cascading barrier dam failures will have an amplification effect.Although the amplification coefficients are different under different conditions,the conclusion can be drawn qualitatively.