| Most of the tuff opencast mines in northwest Sichuan are located in high-intensity seismic zones,and earthquakes are an important factor leading to slope instability,with particularly serious consequences,often inducing large-scale landslides and cave-ins,which directly endanger people’s lives and property,and lead to serious ecological and environmental problems.Therefore,the research on the dynamic stability of slopes in open pit mines in high seismic intensity areas is an important research topic that needs to be addressed urgently.To address the above topic,the slope project of Beichuan Zhonglian’s Mu Jia Dabao limestone open pit mine,which is located in a high seismic intensity zone,was used as a background to explore the factors affecting slope stability and the damage mode under dynamic action;numerical simulation techniques were applied to study the influence of step height,slope angle and width on the stability of the step slope,and the dynamic response characteristics and dynamic stability of the overall slope of the open pit mine under the action of earthquake were analysed.The specific research results are as follows.（1）In view of the engineering characteristics of the slope of the limestone opencast mine in Mujia Da Bao,the factors influencing the stability of the slope under seismic action were discussed and the dynamic damage mode of the slope was determined.（2）A typical slope in the background project was selected,and the safety sensitivity of the step slope of the open pit mine was studied by applying numerical simulation technology and single factor analysis.The influence of the step parameters on the stability of the step slope was analyzed as follows: step height > step slope angle > step width;the recommended step slope parameters are: step height from 13 m to 19 m,step slope angle from 30° to 70°,and step width from 1/3 to 1/2 of the step slope height.（3）On the basis of the safety sensitivity study of the step slope,the seismic response characteristics of the slope at the end of the open pit were investigated by using numerical simulation technology,and the results showed that there are certain elevation amplification effect,tendency table effect and interlayer mutation effect for velocity and acceleration.In general,the displacement has an obvious tendency to be distributed along the slip surface,and the vertical displacement is larger at the top of the slope and the horizontal displacement is larger at the foot of the slope.（4）Combined with the results of the slope dynamic damage model analysis,the seismic stability of the slope at the end of the open pit mine was analyzed by applying the numerical simulation method of dynamic strength reduction,and the results showed that the seismicdamage of the slope was caused by the downward development of the tensile damage at the top edge of the slope and the upward development of the shear damage at the foot of the slope.Shear damage unit at the interlayer is more,one or two steps at the foot of the slope and one or two steps at the top of the slope are relatively serious.（5）It is calculated that the safety coefficient of the taken slope meets the specification requirements and has a certain amount of surplus.Based on the conclusion of the appeal study,the slope step parameters are optimized.The results show that the safety coefficients of the optimized model can meet the specification requirements under extreme working conditions. |
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