| Upstream tailings dam is a traditional dam type widely used in tailings reservoir engineering of mining enterprises and it is accounting for about 80% of nonferrous metal mines in China.Under earthquake,it poses a potential serious threat to people's personal safety and ecological environment downstream.In order to further explore the dynamic stability of upstream tailings dam,this paper starts with the dynamic response of upstream tailings dam,considering the geometric characteristics of dam structure and the seismic characteristics of the two factors,and uses Flac3 D finite difference software to simulate and analyze the dynamic response characteristics of upstream tailings dam under different combination of influence factors.Finally,the field test of microseism is carried out to explore the dynamic response characteristics of upstream tailings dam.The natural vibration characteristics of upstream tailings dam are studied.The main results are as follows:(1)The main factors affecting the dynamic stability of upstream tailings dam are summarized.Considering the four factors of dam height,dam slope ratio,buried depth of phreatic line and seismic peak of ground acceleration by orthogonal experimental method.The dynamic stability characteristics of the dam under couple of the four factors above is obtained.The main factors of the influence degree of the four factors are: dam height ? seismic peak of ground acceleration ? buried depth ofphreatic line ? dam slope ratio.That is,the stability of the upstream tailings dam is most sensitive to the influence of the dam height.The position of the buried depth of phreatic line affects the mechanical properties of the tailings materials of various parts of the dam,thus affecting the macroscopic stability of the dam.When the dam slope ratio is reasonable within the design scope,when the static anti-sliding stability has a certain safety reserve,the influence of the dam slope ratio on the overall stability of the dam is smaller than other factors under the action of the seismic inertial force.(2)Based on the finite difference strength reduction method,the influence of dam height,dam slope ratio and buried depth of phreatic line on the static safety factor of the upstream tailings dam is analyzed,and the distribution and development law of the Through area(potential slip zone)of the dam body under the influence of various factors are summarized.The buried depth of the phreatic line in the dam mainly affects the position and extent of the slip zone.When the depth of the phreatic line is shallow,the higher the position of the plastic penetration zone,the smaller the safety factor of the dam body and the more unstable the dam body.The steepness of the dam slope mainly affects the smoothness of the arc-shaped slip zone.The steeper the dam slope,the more curved the potential slip zone and the more unstable the dam body.The shape and position distribution of the plastic zone slip zone with the same slope ratio and the depth of the phreatic line are similar.The higher the dam body,the larger the weight of the tailings on the upper part of the slip zone,the more the dam body tends to Unstable.(3)Considering the dynamic response of the dam body under single action of four factors: seismic peak of ground acceleration,dam height,dam slope ratio and buried depth of phreatic line,the law about distribution and variation of peak acceleration,peak displacement and peak excess pore pressure ratio of the upstream tailings dam under seismic load are summarized.Under the excitation of the same peak seismic inertia force,when the dam height is constant,the dam slope is slower(the slope ratio is smaller)and the phreatic of phreatic surface is smaller,the overall amplification effect of the upstream tailings dam on the ground motion is smaller;as a whole,the horizontal response displacement of the dam is greater than the verticalresponse displacement.The higher the dam body and the steeper the dam slope,the greater the peak response of the dam.The influence of the buried depth of the phreatic line on the response displacement of the dam is relatively small;The surface of the sedimentary beach at the top of the upstream tailings dam is prone to liquefaction.Under the same dam height and phreatic line depth,the steeper the dam slope,the greater the input acceleration peak,the more significant the liquefaction degree.(4)The influence of different ground motion parameters(peak value,spectrum and duration)on the dynamic response of the upstream tailings dam is analyzed,and the variation laws of displacement field,response acceleration,response displacement and excess pore pressure ratio of the dam body under different ground motion parameters are summarized.The input seismic waves are amplified in the vertical direction of the upstream tailings dam and on the face of the dam slope.The damping characteristics of dam material filter the high frequency part of the input seismic wave.And there is amplification effect on the low frequency part;The response acceleration and displacement of the dam slope and the dam body as a whole increase with the increase of the peak value and duration of the input seismic wave,and decrease with the increase of the frequency of seismic wave.The excess pore pressure ratio of the dam body has a significant response to the peak value and duration of the input seismic wave,with the peak value and duration of the input seismic wave increase significantly,but is not sensitive to the input ground motion frequency.(5)The in-site microseism test of the upstream tailings dam is carried out,and the microseism spectrum characteristics and natural vibration characteristics of the upstream tailings dam are obtained by combining the sedimentary structure data of the dam body and the measured microseism data.The data processing results show that the dominant frequency range of the natural vibration of the tailings dam is 1.5Hz ~5.1Hz,and the microseism dominant frequency at the top of the dam is 3.5Hz.The spectrum curve of the whole spectrum is multi-peak type,and the excellent frequency component of the microseism is rich and varied,with a wide frequency band,showing a chaotic state. |
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