# Effect of Characteristics of Ground Motion on Seismically Induced Sliding Surface of Slopes
## 6 Conclusions  
The objective of this study is to evaluate the sensitivity of the sliding surface to input motion intensity and frequency characteristics for a range of slope characterizations. A series of 2D nonlinear dynamic FE analyses is performed. The sliding surface is calculated from the contour of maximum shear strain at the end of shaking. The sliding surfaces determined from the dynamic analyses are extensively compared with those derived from pseudo-static analyses. The differences in the calculated sliding surfaces are quantified with the residual, which is defined as the discrepancy in the mobilized soil mass area above the surface in log normal unit. The following conclusions are drawn from the comparative results presented in this study:  
* It is shown that the sliding surface may vary with the intensity and frequency characteristics of the input motion. Slopes with inclination angle equal or less than 35\({}^{\circ}\) are marginally influenced by the motion intensity if \(T_{m}\) < 0.3 s. For such cases, the residuals are less than 0.4. Slopes inclined at 45\({}^{\circ}\) are demonstrated to be more sensitive to the motion intensity and \(T_{m}\).
* For motions with \(T_{m}\) < 0.3 s, the sliding surfaces determined from dynamic analyses are not highly influenced by the motion intensity. In contrast, the surface widens with intensity when calculated from a pseudo-static analysis. Because of these contrasting trends, the residual in the calculated sliding surfaces decreases with an increase in intensity.
* For motions with \(T_{m}\) > 0.3 s, the sliding surface derived from a dynamic analysis is demonstrated to widen with an increase in the intensity of the input ground motions. The degree of widening generally increases proportionally with an increase in \(T_{m}\).
* It is, therefore, recommended to derive sliding surfaces from a dynamic analysis for steep slopes. It should, however, be noted that the conclusions are based on a limited number of motions. Further studies are warranted to quantify the discrepancy in the calculated sliding surfaces using an extensive series of motions.
* It is recommended that, when determining the Newmark displacement or dynamic factor of safety from a dynamic analysis, the failure surface should be determined from the shear strain contour at the end of the simulation. This additional procedure is particularly relevant for the design of slopes in highly active regions, for which the use of a predefined surface determined from a limit equilibrium method is discouraged.  
[PERSON], [PERSON] ([PERSON]), [PERSON]-[PERSON] ([PERSON]), [PERSON]-[PERSON] and [PERSON] conceived the idea, outlined the work and co-wrote the manuscript; [PERSON] performed the numerical analyses and co-wrote the manuscript; [PERSON]. ([PERSON]) supported in performing the numerical simulations and summarizing the results. All authors have read and agreed to the published version of the manuscript.  
This research was jointly supported by a project titled \"Evaluation of the dynamic response of nuclear slopes through reduced model tests\" funded by Korea Hydro & Nuclear Power Co. and by a grant (18 SCIP-B146946-01) from the Construction Technology Research Program funded by Ministry of Land, Infrastructure and Transport of Korean government.  
Data Wariability Statement: Data sharing not applicable.  
The authors declare no conflict of interest.