Analysis Of Slope Stability Based On Seepage And Earthquake

Groundwater seepage and earthquake are two important factors in analysis of the slope stability.The stability of slope under the complex conditions of seepage and earthquake has become one of the hot topics in geotechnical engineering.At present,the main problems are the calculation method of slope stability under the complex conditions is not perfected,and the factors influenced on stability need to be analyzed in this field of research.This thesis not only provides a new way to solve the stability of slope under complex conditions,but also provides a theoretical reference and practical significance to evaluate the mechanism of losing stability with the seepage and earthquake coupling.Based on the previous work,the limit equilibrium theory and numerical simulation are studied to analyze the slope stability with the complex conditions of seepage and earthquake,and the special slope stability problems are also discussed in this research.The main results are as follows.1?The analytical formulas of the safety factor on sandy slope and clay slope are derived under the seepage and earthquake coupling.Moreover,a generalized form of horizontal integration model is presented to calculate the safety factor.The results show that the analytical method can be obtained the consistent conclusions with other methods,and the laws of safety factor with vibration time can be reflected by these results.From these results it can conclude that the safety factor computed by analytical method is lower than the results of pseudo static method,but is similar to the results of dynamic time history method.It is important that the hydraulic gradient and water level have a significant influence on slope stability.The slope stability is seriously reduced by the high water level and the horizontal seismic force,but the effects of the vertical seismic force on the stability is not obviously compared with the horizontal seismic force affected.The analytical formula of the horizontal integral model for special shaped slope is obtained by mathematical integration,and the results show that the safety factor computed by this method is generally low,and then the evaluation of stability is relatively conservative.This analytical method provides an important theoretical basis for the research of slope stability under the seepage and earthquake,and also provides an effective tool to explore the laws of safety factor.2?A new method for evaluating the stability of slope is proposed,which is based on the dip angle of sliding surface as weight.Furthermore,the slope stability under the seepage and earthquake is analyzed based on the point safety factor method by using the Tianjin wave as the input ground motions.The second-order slope is as the research object in this study and the stress and strain distribution of slope are discussed,and the influence of the platform width and the slope angle on stability are also analyzed under this coupling effect of the seepage and stress.The results show that the safety factor which is modified by dip angle as weight is higher than that of the traditional Swedish slice method,and the results are consistent with the value obtained from the finite element strength reduction method.The coupling effects of seepage and stress has an obviously influence on the horizontal displacement of slope,and has little influence on the vertical displacement.Moreover,the results also show that the sandy slope of strong permeability is affected markedly by this coupling effect,and the shape and position of sliding surface are also decided by the platform and the slope angle,so that it indicates that the shear outlet of multi-order slope is no longer only.This study suggests that analysis of the slope stability by applying the point safety factor method should be used high order element,low grid and large scale boundary,and then it can improve the computational efficiency and reduce computational cost.3?A method of calculated the maximum crack on the top of slope is proposed and the stress intensity factor at the crack tip is also analyzed under the complex conditions.The results show that the maximum crack on the top of slope can be constrained by the soil deformation parameters and the maximum tension stress.Combined with the limit equilibrium method,the safety factor can be calculated in the tension shear model of slope.The reason of the crack induced by the water pressure and the horizontal seismic force is explained by the stress intensity factor of the crack tip,the results agree well with numerical simulation data.Although the method of this study provides a new idea for analysis of slope stability under the tension shear failure model,the reliability of this method also needs to be tested in future.4?The approximate solution of the nature frequency of weak interlayer is derived,and a simplified calculation method and its application scope are presented for this special slope.The results show that the instability of slope with weak interlayer is caused by the interaction between the slope and the weak interlayer.The nature frequency of the weak interlayer is calculated by using the elastic mechanics method,and the important role of the weak interlayer for slope instability is illustrated compared with the results of the harmonic resonance.Based on the limit equilibrium theory,taking the ratio of circle slip to the composite sliding surface as weight,a simplified method for analysis of the slope stability with weak interlayer is proposed.The results show that the safety factor calculated by this simplified method is generally lower,and this method is more suitable for the special slope with interlayer of small thickness,small inclination angle and horizontal distribution at the bottom of slope.However,for the slope with interlayer of large thickness,it is suggested to simplify the layered soil slope to analyze.