Study On Acoustic Emission Characteristics Of Loose Granular Media Under Different Seepage Conditions

Currently,seepage failure accidents occur frequently in geotechnical engineering,which has brought serious casualties and property losses to people.Therefore,the accurate prediction of seepage state is of great significance to engineering safety.Because seepage generally occurs in loose granular media,the friction and collision between granular media will produce elastic waves,which makes it possible to monitor the seepage state by acoustic emission technology.Therefore,in order to predict the seepage state,it is a very necessary premise to explore the evolution law of acoustic emission characteristics of loose granular media under different seepage states by using acoustic emission technology.Firstly,based on the elastic wave signals induced by the rise of water,various tailings sand particle size and seepage velocity,the seepage state of tailings sand medium is monitored by acoustic emission technology.From 80 cm,110cm 140 cm three different head heights The water flow under（flow velocity）infiltrates into tailing sand media with particle sizes of 0.1-0.25 mm,0.25-0.5mm,0.5-1mm and mixed respectively,simulates the seepage of tailing dam,monitors the AE signals in the seepage process under different conditions,and analyzes the characteristics of AE signals of liquid level rise,tailing sand particles with different particle sizes and seepage at different flow velocities.The results show that among the groups of particle sizes selected in the test,when the flow velocity is the same The larger the particle size,the stronger the AE signal of tailings sand seepage process;Under the same particle size,the smaller the velocity,the smaller the AE signal amplitude and the fewer AE events,that is,the smaller the velocity,the weaker the AE signal in the seepage process of tailings sand;In the process of liquid level rise,the AE signal generated at the liquid level position is the strongest,and the AE signal changes with the distance between the liquid level position and the sensor.The closer to the sensor,the stronger the AE signal,which shows that the change of liquid surface during the rise of water level under seepage state can be reflected in AE signal.Secondly,considering the influence of flow velocity,mass proportion of small particles to skeleton particles and small particle size,the motion test of small particles in porous media seepage process is carried out.By analyzing the characteristics of AE signal under various influencing factors,it can be concluded that the greater the flow rate,the larger the ringing count,amplitude and energy of AE signal generated by small particle movement,and the smaller the b value,that is,the stronger the AE signal;Too much or too little filling of small particles will reduce the AE activity.Among the 1/9,1/6,1/4,1/3 and 1/2 mass ratios selected in the test,when the ratio is less than 1/4,with the increase of the ratio,the ringing count,amplitude and energy of the AE signal generated by the movement of small particles in the seepage state gradually increase,and the b value gradually decreases,that is,the AE signal increases with the increase of the filling proportion,When it is greater than 1/4,it shows the opposite trend;When there is small particle movement in the seepage process,the AE signal generated is significantly stronger than that without small particle movement,and the larger the particle size of filled small particles（much smaller than the particle size of skeleton particles）,the larger the ring count,amplitude and energy of AE signal,the smaller the b value,that is,the stronger the AE signal.Then,the small particle transport test under seepage state is simulated.The AE ringing count,amplitude and energy generated in the process of small particle transport will show a phased weakening trend with the development of small particle transport process,while the b value is on the contrary,and this trend gradually decreases with the development of seepage process,and the fluctuation amplitude of AE signal characteristic parameters gradually decreases;When the transport process of small particles is in the same stage,the larger the flow velocity is,the larger the AE characteristic parameters are,and the change of AE characteristic parameters is more obvious.If the small particles do not rush out with the water flow,that is,the amount of small particles in the container remains constant,there is no such trend of periodic change.Finally,using the obtained AE characteristic parameters and their evolution law,and with the help of BP neural network,the reverse prediction of groundwater level rise process and small particle transport development stage under seepage state is carried out,and the prediction results generally are up to the mark.The results of this study can provide theoretical and technical support for the prediction of groundwater level rise and piping,and is of great significance to prevent major accidents caused by seepage damage.