Shakedown method versus pseudostaic method for seismic slope stability

Seismic stability of slopes is typically evaluated by conventional methods under the assumption that the slope is subjected to an earthquake just for one time. In general, time histories of loadings on slopes are unknown and loads are of variable repeated nature. Shakedown phenomenon can be considered as a safe state for slopes subjected to variable repeated loadings. In this study, lower bound dynamic shakedown theorem is employed for the seismic stability of slopes as a comprehensive verification. A numerical method applied previously to evaluate roads under the traffic loads was modified to make it appropriate for dynamic shakedown analysis in the present study. The numerical method is based on the combination of finite element and linear programming methods. Critical PGA is employed as a comparative parameter to compare shakedown and pseudostatic methods. Results show that, unlike pseudostaic method, shakedown approach is able to consider dynamic properties of load and slope. Also, it is indicated that contrary to pseudostaic approach, shakedown solutions are different for slopes and embankments. Shakedown and pseudostaic critical PGA versus dynamic properties of load and slope creates four distinct zones. It is shown that the forgoing zones can be used as appropriate tools for seismic zonation of slopes based on their short term and long term safety