Abstract: The design of reinforced soil structure is mostly based on the Limited Equilibrium Theory (LET), which is somewhat conservative. In this paper, the conservatism in several international design codes or design guidelines are analyzed, and field measurement data from well working reinforced soil structures are listed to verify the degree of conservatism. Moreover, the failure modes (patterns) and stability analysis scenario for reinforced structures are described. Stability calculation is recommended to be conducted in terms of the stability of reinforcement material itself and the overall stability of reinforced soil structure. It is emphasized that as not all of the possible failure mechanisms were found from internal or external stability analysis, analysis on the compound slide surface which has possibly the minimum stability coefficient is necessary. It means that the designer has to consider all failure mechanisms: the compound slip surface might slide across the reinforcement and/or slide along the geosynthetics at each layer. So the stability calculation for the whole structure needs to be conducted without any distinction of internal or external. Finally, a reasonable design method (FEM + LEM) for reinforced soil structures is recommended. Stress-strain analysis is the most fundamental and useful data for design, but the performance of structure in limit state should also be taken into consideration.

Key words: geotechnical engineering, reinforced soil structure, limited balance theory, compound slip surface, FEM + LEM design method