Stability Analysis Of Multistage Loess Slope Under Earthquake Action

Multistage loess slope is one of the common slope types in Northwest China.At present,the research on its stability under earthquake action is relatively less,and the theoretical framework is lagging behind,which leads to the lack of reliable theoretical basis for seismic design and optimization of multistage loess slope.Therefore,the stability analysis of multistage loess slope under earthquake action has become an issue of widespread concern in my country’s geotechnical community.In view of this,this paper studies the related research contents of multistage loess slope stability analysis under earthquake action,such as the calculation of multistage loess slope stability under earthquake action,sensitivity analysis of influencing factors of multistage loess slope stability under earthquake action,seismic optimization design of multistage loess slope,etc.,in order to provide reference for the stability analysis of multistage loess slope under earthquake action.The main research contents and results are as follows:(1)This paper proposes a comprehensive method for analyzing the stability of multistage loess slope under earthquake action.Firstly,the possible failure mechanisms such as the toe circle and midpoint circle in the multistage loess slope global failure mode and partial failure mode are established;then based on the improved limit equilibrium pseudo-static method,the safety factor analytical formula of the multistage loess slope under earthquake corresponding to each failure mechanism is deduced,and the optimization method is further used to determine the minimum value of the slope seismic stability safety factor;Finally,the flow chart of seismic stability analysis of multistage loess slope is given to determine the minimum safety factor and critical slip surface.The results of numerical examples show that the slope stability analysis results of this method are very close to the traditional pseudo-static limit equilibrium method.The relative deviation of the minimum safety factor calculated by the two methods is not more than 7.2%,and the critical slip surfaces determined by the two methods are basically the same.(2)This paper briefly introduces the main factors that affect the stability of multistage loess slope under earthquake action,such as the properties and structure of slope rock and soil,slope topography and earthquake action.The slope soil parameters,slope geometric parameters and earthquake action are selected as the main research objects.The orthogonal experiment design method is used to arrange the sensitivity analysis test of multistage loess slope stability influence factors.The variance method and range method are used to analyze the test results,and the sensitivity ranking and significance of each influencing factor are obtained.The results show that the horizontal seismic force is the most sensitive factor affecting the seismic stability of multistage loess slope,and the horizontal seismic force and the internal friction angle of the soil have a highly significant affect on the seismic stability of multistage loess slope.(3)For this kind of multistage loess slope with limited sloping space(the total slope rate is certain),the single factor tests on the width of slope platform and number of stages is arranged.Through the finite element simulation,the influence law of the slope platform width and number of stages on the seismic dynamic response and stability of the slope is obtained,which provides a reference for the seismic optimization design of this kind of multistage loess slope.The study results show that as the width of each platform of the slope increases,the slope of each stage of slope becomes steeper,the seismic acceleration and displacement response of the slope increases,and the seismic stability of the slope first increases and then becomes smaller;With the increase of the number of stages,the slope of each stage of slope becomes steeper,the seismic acceleration and displacement response of the slope first increases and then weakens,and the seismic stability of the slope also increases first and then becomes smaller.