Abstract: The basic principle of equivalent additional stress method is that only soil skeleton is concerned while the reinforcing effect is considered to be equivalent additional stress acting on the soil skeleton in the direction reinforcement being bedded. This method is fit for fiber reinforced soil, soil nailing wall and soil reinforced with layered reinforcements, etc. It can not only remove interface element for the method dealing with soil and reinforcement separately, but also avoid determining the composite constitutive equation of the reinforced soil. However, iteration is necessary for the conventional equivalent additional stress method, which makes it difficult in writing FEM program. In this paper, a modified method is put forward to deal with this problem. An additional matrix is calculated and added to the elastic matrix or elastoplastic matrix of soil, the method can be employed directly without iteration. The modified method is easy for writing FEM program and helpful for extending the application of equivalent additional stress method.

Key words: reinforced soil, fiber reinforced soil, soil-nailing wall, equivalent additional stress method, finite element method