Proposal of Elena Kapogianni of National Technical
Reinforced Slope Safety Evaluation and Design Due to Seismic Loading,
Based on the Determination of the Critical Slip Surface Using Acceptability Criteria
The design and safety evaluation of reinforced slopes subjected to seismic loading is a complex problem. Various methods of analysis are used in order to solve this problem such as the limit equilibrium method, the limit analysis and the finite element analysis. In most of the techniques that are based on the limit equilibrium method and on the limit analysis, the shape of the potential slip surface is predefined (planar, circular, log spiral etc).
Sarma (2004), Sarma and Tan (2006) formulated a new procedure for homogenous and non-homogenous unreinforced slopes, within the framework of the limit equilibrium technique, where no prior assumption of the shape of the surface is needed. According to this method, the slip surface, which comprises a series of straight lines, is obtained slice by slice, going from downhill to uphill. The slip surface and the interslice boundaries are not predefined. The equilibrium of the slice and the acceptability criteria determine the slip surface and the interslice boundaries of the slice.
Main goal of the research proposed here, is to develop a new solution for the design and safety evaluation of reinforced slopes with simple and composite geometry, with no prior assumption of the shape of the slip surface. Similarly to the method developed by Sarma & Tan, the acceptability criteria in terms of stresses and cinematics will determine the slip surface and the interslice boundaries of the slice. The non- linear equations which will include the affect of the reinforcement on the slope will be formed and a suitable optimization technique will be chosen for the implementation of the methodology. The solution will be programmed with the help of a suitable software development package (Borland Delphi), creating this way a fast tool for the design and safety evaluation of reinforced slopes.
The results that will derive will be compared with correspondent ones from a) analysis with conventional numerical methods based on the limit equilibrium technique b) limit analysis and c) finite element stress analysis.
In addition, the analysis method that will be developed for the design of reinforced slopes with composite geometry (slopes with berms) will be compared with an analytical solution for multi-step reinforced earth slope design that already has been developed and programmed (Kapogianni & Sakellariou 2008). In this case, the calculations will be performed initially for each berm individually (local stability calculations) and then for the whole slope (global stability calculations). The new procedure will enrich the already existing one, creating this way a comprehensive and completed tool for the design and safety evaluation of multi- step reinforced slopes.
Moreover, the forms of the slip surfaces that will derive form the new procedure will be compared with already existing predefined possible slip surfaces that are used in other techniques (such as planar, circular and log spiral). The results will show which predefined slip surface shape resembles more with the slip surface that will result from the new method. This comparison will be made for reinforced slopes with various mechanical and geometrical characteristics and at different seismic coefficient.
Finally, an experimental evaluation of the methodology can be planed where the failure conditions can be determined along with the form of the slip surfaces.
 Sarma, S.K. 2004. Critical Slip Surface in Slope Stability Analysis. In: Advances in Geotechnical Engineering
 Sarma, S.K. & Tan, D. 2006. Determination of Critical Slip Surface in Slope Stability Analysis. In: Geotechnique 56, No. 8, 539-550
 Kapogianni, E.K. & Sakellariou M.G. 2008. Analytical solution of multi step reinforced-soil slopes stability due to static and seismic
loading (1st International Conference on Transportation Geotechnics/ August 2008/ Nottingham-paper accepted)
 Kapogianni, E.K. & Sakellariou M.G. 2008. Comparison of an analytical solution for multi-step reinforced soil slopes with
conventional numerical methods (4th European Geosynthetics Conference/ September