Abstract: The geosynthetic reinforcement layer techniques have been widely used nowadays in the foundations and embankments. During the course of the design of the geosynthetic reinforcement layer, the confirmation of the stress diffusion angle is very important, but no good methods to calculate the stress diffusion angle. This paper presents the method of calculating the stress diffusion angle of geosynthetic reinforcement layer based on additional stress back-analysis; and then using this method, researching the setup parameters of geosynthetic reinforcement layer ( the thickness of geosynthetic reinforcement layer, the composite modulus of compressibility of geosynthetic reinforcement layer) and geosynthetic factors (such as reinforcing space, reinforcing width, total numbers of geosynthetic reinforcement layer etc.)on the distribution rule of the stress diffusion angle; the results indicate that the range of the stress diffusion angle is 45-60 º; further more the setup parameters of geosynthetic reinforcement layer and geosynthetic factors existing optimum values, corresponding on these values, the stress diffusion angle reaches the max. Finally, using orthogonal tests and regression methods, many effect factors on the stress diffusion angle are analyzed, the results indicate reinforcing space has a most effect on the stress diffusion angle of the geosynthetic reinforcement layer, secondly the embedded depth of the first geosynthetic, however, reinforcing width has a slight effect on the stress diffusion angle.

Key words: geosynthetic reinforcement layer, stress diffusion angle, numerical analysis