Study On Guided Wave Characteristics In Dam Break Process Of Tailings Reservoir

The essence of the failure process of tailings dam is the continuous evolution process of internal structure mechanism.Acoustic signal is a phenomenon associated with the failure process of tailings dam.Its activity characteristics can reflect the evolution process of internal mechanism of tailings dam.In this paper,guided wave monitoring tailings dam slip failure test is carried out by the combination of "waveguide bar + steel ball".Firstly,the dispersion equation of longitudinal/flexural guided waves is derived based on the theory of longitudinal/flexural guided waves.Then,the size of the waveguide bar + steel ball structure used to collect longitudinal/flexural guided wave signals is optimized by the dispersion equation.Finally,the optimal size of the "waveguide bar + steel ball" structure is used to collect the test signal,and the guided wave characteristics are analyzed.The main conclusions are as follows:(1)Combining the attenuation dispersion equation of longitudinal guided wave and flexural guided wave in the waveguide rod and the frequency distribution law of longitudinal guided wave signal,it is found that the combination of 14 mm diameter guide rod and 6 mm diameter steel ball or the combination of 14 mm and 8 mm is suitable for collecting longitudinal guided wave signal in the process of tailings dam break.The combination of 20 mm diameter guide rod and 8 mm diameter steel ball or the combination of 20 mm and 10 mm is suitable for collecting flexural guided wave signals.(2)During the process of tailings dam break,longitudinal and flexural guided waves are generated.The parameters of the two types of signals are analyzed,and the characteristics of the changes can be used as the basis for the warning of slip damage of the tailings dam.Specifically: the micro-crack incubation stage,the longitudinal/flexural guided wave activity is not obvious,the guided wave parameter value is small;the crack propagation and penetration stage,the longitudinal/flexural guided wave activity is active,the guided wave parameter value is significantly increased;the slip failure stage The longitudinal/flexural guided wave activity is the most severe,and the value of the guided wave parameter increases sharply;the slip to the stable stage,the longitudinal/flexural guided wave activity is weakened,and the guided wave parameter value is lowered.(3)The ringdown counts,energy and amplitude series of longitudinal and flexural guided waves generated by tailings dam break have fractal characteristics in time domain.The fractal of longitudinal guided wave ringdown counts,energy and amplitude satisfies the change characteristics of "rise-fall" on the whole,while the fractal of flexural guided wave ringdown counts,energy and amplitude satisfies the change characteristics of "unchanged-rise-fall" on the whole,and the maximum fractal dimension of both guided wave parameters occurs in the stage of slip failure,which can be used as a precursor of tailings dam slip failure.(4)The main frequencies of longitudinal guided wave and bending guided wave are extracted respectively.It is found that the main frequencies of both guided waves are mainly distributed in two frequency bands,and the frequency band range is slightly different.Guided wave signals outside the frequency band appear in the crack propagation and penetration stage of tailings dam.Statistics of the number of main frequencies in each frequency band at different time intervals(10 seconds interval)show that the overall trend is "up-down".(5)The b-value analysis of longitudinal guided wave and flexural guided wave shows that the b-value of both guided wave signals decreases before slip failure and keeps fluctuating at a low level during slip failure period.